| Paper | Title | Page |
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| MOP001 | Charge Separation for Muon Collider Cooling | 103 |
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| Most schemes for six dimensional muon ionization cooling work for only one sign. It is then necessary to have charge separation prior to that cooling. Schemes of charge separation using bent solenoids are described, and their simulated performances reported. It is found that for efficient separation, it should take place at somewhat higher momenta than commonly used for the cooling. | ||
| MOP002 | Tapered Six-Dimensional Cooling Channel for a Muon Collider | 106 |
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| A high-luminosity muon collider requires a reduction of the six-dimensional emittance of the captured muon beam by a factor of approximately 106. Most of this cooling takes place in a dispersive channel that simultaneously reduces all six phase space dimensions. We describe a tapered 6D cooling channel that should meet the requirements of a muon collider. The parameters of the channel are given and preliminary simulations are shown of the expected performance. | ||
| MOP003 | Six-Dimensional Bunch Merging for Muon Collider Cooling | 109 |
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| A muon collider requires single, intense, muon bunches with small emittances in all six dimensions. It is most efficient to initally phase-rotate the muons into many separate bunches, cool these bunches in six dimensions (6D), and, when cool enough, merge them into single bunches (one of each sign). Previous studies only merged in longitudinal phase space (2D). In this paper we describe merging in all six dimensions (6D). The scheme uses rf for longitudinal merging, and kickers and transports with differing lengths (trombones) for transverse merging. Preliminary simulations, including incorporation in 6D cooling, is described. | ||
| MOP007 | The Development Status of Compact Linear Accelerator in Korea | 112 |
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Funding: This work was supported by KBSI D30300 to M.S Won The establishment of a compact linear accelerator is in progress by Korea Basic Science Institute. The main capability of this facility is the production of multiply ionized metal clusters and the generation of intense beams of highly charged ions for material, medical and nuclear physical research. To generate the intense beam of highly charged ions, we will develop an Electron Cyclotron Resonance Ion Source (ECRIS) using 28GHz microwaves. For this ECRIS, the designing of a superconducting magnet, microwave inlet, beam extraction, and plasma chamber were in progress. A superconducting magnet system have also being developed. In this presentation, I report the current status of our compact linear accelerator development and future plan. |
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| MOP008 | Upgrade of the Argonne Wakefield Accelerator Facility (AWA) and Commissioning of a New RF Gun for Drive Beam Generation | 115 |
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. The AWA Facility is presently undergoing several upgrades that will enable it to further study wakefield acceleration driven by high charge electron beams. The facility employs an L-band photocathode RF gun to generate high charge short electron bunches, which are used to drive wakefields in dielectric loaded structures as well as in metallic structures (iris loaded, photonic band gap, etc). Several facility upgrades are underway: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level. |
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| MOP009 | Status and Plans for a SRF Accelerator Test Facility at Fermilab | 118 |
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Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy A superconducting RF accelerator test facility is being constructed at Fermilab. The existing New Muon Lab (NML) building is being converted for this facility. The accelerator will consist of an electron gun, injector, beam acceleration section consisting of 3 TTF-type or ILC-type cryomodules, multiple downstream beamlines for testing diagnostics and conducting various beam tests, and a high power beam dump. When completed, it is envisioned that this facility will initially be capable of generating a 810 MeV electron beam with ILC beam intensity. Expansion plans of the facility are underway that will provide the capability to upgrade the accelerator to a total beam energy of 1.5 GeV. In addition to testing accelerator components, this facility will be used to test RF power equipment, instrumentation, LLRF and controls systems for future SRF accelerators such as the ILC and Project-X. This paper describes the current status and overall plans for this facility. |
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| MOP010 | Resonance, Particle Stability, and Acceleration in the Micro-Accelerator Platform | 121 |
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Funding: US Defense Threat Reduction Agency A micron-scale dielectric-based slab-symmetric accelerator is currently being designed and fabricated at UCLA. This Micro-Accelerator Platform (MAP) accelerates electrons in a 800nm wide vacuum gap via a resonant accelerating mode excited by a side-coupled optical-wavelength laser. Detailed results of particle dynamics and field simulations are presented. In particular, we examine various methods of achieving net acceleration and particle stability. Additionally, structural designs that produce accelerating fields synchronous with both relativistic and sub-relativistic electrons are discussed. |
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| MOP011 | Standing Wakefield Accelerator Based on Periodic Dielectric Structures | 124 |
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| In recent years dielectric wakefield accelerators (DWA) have attracted significant attention for applications in high energy physics and THz radiation sources. However, one needs sufficiently short driving bunches in order to take advantage of the DWA's scaling characteristics to achieve high gradient and high frequency accelerating fields. Since a single large charge Q driving bunch is difficult to be compressed to the needed rms bunch length, a driving bunch train with smaller Q and small emittance, should be used instead for the DWA. In view of this senario, the group velocity of the excited wakefields needs to be decreased to nearly zero, so the electromagnetic energy does not vacate the structure during the bunch train. In this paper we propose a standing wakefield accelerator based on periodic dielectric structures, and address the difference between the proposed structure and the conventional DWA. | ||
| MOP012 | Ultra-High Gradient Compact S-Band Accelerating Structure | 127 |
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Funding: Dept. of Energy DE-SC0000866 In this paper, we present the radio-frequency design of the DECA (Doubled Energy Compact Accelerator) S-band accelerating structure operating in the pi-mode at 2.856 GHz, where RF power sources are commonly available. The development of the DECA structure will offer an ultra-compact drop-in replacement for a conventional S-band linac in research and industrial applications such as drivers for compact light sources, medical and security systems. The electromagnetic design has been performed with the codes SuperFish and HFSS. The choice of the single cell shape derives from an optimization process aiming to maximize RF efficiency and minimize surface fields at very high accelerating gradients, i.e. 50 MV/m and above. Such gradients can be achieved utilizing shape-optimized elliptical irises, dual-feed couplers with the "fat-lip" coupling slot geometry, and specialized fabrication procedures developed for high gradient structures. The thermal-stress analysis of the DECA structure is also presented. * V. Dolgashev, "Status of X-band Standing Wave Structure Studies at SLAC", SLAC-PUB-10124, (2003). ** C. Limborg et al., "RF Design of LCLS Gun", LCLS-TN-05-03 (2005). |
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| MOP014 | Status and Upgrades of the NLCTA for Studies of Advanced Beam Acceleration, Dynamics, and Manipulation | 130 |
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| The Next Linear Collider Test Accelerator (NLCTA) is a low-energy electron accelerator (120 MeV) at SLAC that is used for ultra-high gradient X-band RF structure testing and advanced accelerator research. Here we give an overview of the current program at the facility, including the E-163 direct laser acceleration experiment, the echo-enabled harmonic generation (EEHG) FEL experiment, narrow-band THz generation, coherent optical transition radiation (COTR) studies, microbunching instability studies, and X-band structure testing. We also present the upgrades that are currently underway and some future programs utilizing these upgrades, including extension of the EEHG experiments to higher harmonics, and an emittance exchange experiment. | ||
| MOP015 | An X-band Gun Test Area at SLAC | 133 |
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Funding: Work supported by the U.S. DOE Contract No. DE-AC03-76SF00515 The XTA (X-Band Test Area) is being assembled in the NLCTA tunnel of the SLAC National Laboratory to serve as a test facility for new RF guns. The first gun to be tested will be an upgraded version of the 5.6 cell, 200MV/m peak field X-band designed at SLAC in 2003 for the Compton Scattering experiment run in ASTA. This new version includes some features implemented in 2006 on the LCLS gun such as racetrack couplers, increased mode separation and elliptical irises. These upgrades were discussed in collaboration with LLNL since the same gun will be used as a driver for the LLNL Gamma-ray Source. Our beamline includes an X-band accelerating section which takes the electron beam up to 100 MeV and an electron beam measurement station. Other X-Band guns such as the UCLA Hybrid gun will be characterized at our facility. |
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| MOP016 | Preliminary Simulations of Plasma Wakefield Accelerator Experiments at FACET | 136 |
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Funding: This work is supported by USDoE under DE-FC02-07ER41500, DE-FG02-92ER40727 and NSF under NSF PHY-0904039, PHY-0936266. Recent experiments on former facility FFTB at SLAC has demonstrated that a single electron beam driven Plasma Wakefield Accelerator (PWFA) can be produced with an accelerating gradient of 52 GeV/m over a meter-long scale*. If another electron bunch is properly loaded into such a wakefield, it will obtain a high energy gain in a short distance as well as a small energy spread. Such PWFA experiment with two bunches will be performed in FACET, which is a new facility at SLAC**. Simulation results show that with possible beam parameters in FACET the first electron bunch (with less current than that in the FFTB experiment) can still produce a meter-long plasma column with a density of 5x1016 cm-3 via field ionization when we use a gas with a lower ionization energy. The second electron bunch can have a 10 GeV energy gain with a very narrow energy spread. If a pre-ionized plasma is used instead of the neutral gas, the energy gain of the second bunch can be enhanced to 30 GeV. * I. Blumenfeld et al., Nature 445, 741 (2007). ** M. J.Hogan, et al.,NewJ. Phys.12, 055030(2010). |
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| MOP017 | A Sphere Cooler Scheme for Muon Cooling | 139 |
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| Muon cooling is the greatest obstacle for producing an intensive muon beam. The frictional cooling method holds promise for delivering low-energy muon beams with narrow energy spreads. We outline a sphere cooler scheme based on frictional cooling to effectively produce such a “cold” muon beam. As an example source, we take the parameters of a surface muon source available at the Paul Scherrer Institute. Simulation results show that the sphere cooler has an efficiency of 50% to produce a “cold” muon beam with an energy spread of 0.9 keV. The high quality beam can potentially meet the requirements of a neutrino factory or a muon collider. | ||
| MOP018 | The Impact of Beam Emittance on BSM-Physics Discovery Potential at a Muon Collider | 142 |
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| A muon collider would allow for high precision probing of the multi-TeV energy regime and the potential discovery of new physics. Background radiation from electrons from the decay of muons interacting with the beam pipes near the interaction point (IP) places limitations on the design of a muon-collider detector. In particular, conical shielding extending out from the IP along the outside of the beam pipes prevents detection of particles at small angles to the beam line. For a given luminosity, bunches with smaller emittances will have fewer muons and therefore smaller background levels, allowing for shielding with shallower angles. The angular-acceptance dependence of the discovery potential for Kaluza-Klein excitations of the standard model particles is presented as a motivation for improved beam-cooling techniques that can achieve high luminosities with small bunch populations. | ||
| MOP019 | Performance of the Bucked Coils Muon Cooling Lattice for the Neutrino Factory | 145 |
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| Ionization cooling is essential to the Neutrino Factory in order to decrease the large emittance of the tertiary muon beam. Strong focusing and a large RF gradient in the cooling channel are required for efficient cooling; however, the presence of a strong magnetic field inside the RF cavities limits their performance by lowering the breakdown limit. In order to mitigate this problem a new lattice configuration, the Bucked Coils, is proposed: two solenoidal coils of different radius and opposite polarities are placed along the channel at the same z-positions. The Bucked Coils lower the magnetic field in the RF cavities while also providing strong focusing. This paper presents the results of the beam dynamics simulations in the new lattice, using the G4MICE code. The comparison of the achieved cooling performance and transmission between the currently proposed Neutrino Factory baseline lattice (FSIIA) and the new configuration is provided in detail. | ||
| MOP021 | The MICE Muon Beamline and Induced Host Accelerator Beam Loss | 148 |
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Funding: Science and Technology Facilities Council The international Muon Ionisation Cooling Experiment (MICE) is designed to provide a proof of principle of ionisation cooling to reduce the muon beam phase space at a future Neutrino Factory and Muon Collider. The MICE Muon Beam is generated by the decay of pions produced by dipping a cylindrical titanium target into the proton beam of the 800 MeV ISIS synchrotron at the Rutherford Appleton Laboratory, U.K. Studies of the particle rate in the MICE Muon Beamline and its relationship to induced beam loss in ISIS are presented, using data taken in Summer 2010. Using time-of-flight to perform particle identification estimates of muon rates are presented and related to induced beam loss. |
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| MOP022 | The Expected Performance of MICE Step IV | 151 |
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Funding: STFC The international Muon Ionization Cooling Experiment (MICE), under construction at the Rutherford Appleton Laboratory in Oxfordshire (UK), is a test of a prototype cooling channel for a future Neutrino Factory. The experiment aims to achieve, using liquid hydrogen absorbers, a 10% reduction in transverse emittance, measured to an accuracy of 1% by two scintillating fibre trackers within 4 T solenoid fields. Step IV of MICE will begin in 2012, producing the experiment's first cooling measurements. Step IV uses an absorber focus coil module, placed between the two trackers, to house liquid hydrogen or solid absorbers. The performance of Step IV using various absorber materials was simulated. Multiple scattering in high Z absorbers was found to mismatch the beam with the lattice optics, which was largely corrected by re-tuning the MICE lattice accordingly. |
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| MOP023 | Particle Tracking and Beam Matching Through the New Variable Thickness MICE Diffuser | 154 |
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| The Muon Ionisation Cooling Experiment (MICE) aims to demonstrate the transverse cooling of muons for a possible future Neutrino Factory or Muon Collider. The diffuser is an integral part of the MICE cooling channel. It aims to inflate the emittance of the incoming beam such that cooling can later be measured in the MICE channel. A novel new diffuser design is currently in development at Oxford, consisting of a high density scatterer of variable radiation lengths. Simulations have been carried out in order to fully understand the physics processes involved with the new diffuser design and to enable a proper matching of the beam to the MICE channel. | ||
| MOP030 | Muon Capture for the Front End of a μ+μ- Collider | 157 |
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| We discuss the design of the muon capture front end for a μ±μ- Collider. In the front end, a proton bunch on a target creates secondary pions that drift into a capture transport channel, decaying into muons. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. The muons are then cooled and accelerated to high energy into a storage ring for high-energy high luminosity collisions. Our initial design is based on the somewhat similar front end of the International Design Study (IDS) neutrino factory. | ||
| MOP032 | High Pressure RF Cavity Test at Fermilab | 160 |
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Funding: Supported in part by DOE STTR grant DE-FG02-08ER86350 Operating a high gradient radio frequency cavity embedded in a strong magnetic field is an essential requirement for muon beam cooling. However, a magnetic field influences the maximum RF gradient due to focusing of dark current in the RF cavity. This problem is suppressed by filling the RF cavity with dense hydrogen gas. As the next step, we plan to explore the beam loading effect in the high pressure cavity by using a 400 MeV kinetic energy proton beam in the MuCool Test Area at Fermilab. We discuss the experimental setup and instrumentation. |
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| MOP036 | Epicyclic Twin-Helix Ionization Cooling Simulations | 163 |
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Funding: Supported in part by DOE SBIR grant DE-SC0005589 Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we earlier developed an epicyclic twin-helix channel with correlated behavior of the horizontal and vertical betatron motions and dispersion. We now insert absorber plates with short energy-recovering units located next to them at the appropriate locations in the twin-helix channel. We first demonstrate conventional ionization cooling in such a system with the optics uncorrelated. We then adjust the correlated optics state and induce a parametric resonance to study ionization cooling under the resonant condition. |
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| MOP037 | Muon Ionization Cooling Experiment: Controls and Monitoring | 166 |
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Funding: NSF The Muon Ionization Cooling Experiment (MICE) is a demonstration experiment to prove the viability of cooling a beam of muons for use in a Neutrino Factory and Muon Collider. The MICE cooling channel is a section of a modified Study II cooling channel which will provide a 10% reduction in beam emittance. In order to ensure a reliable measurement, we intend to measure the beam emittance before and after the cooling channel at the level of 1%, or an absolute measurement of 0.001. This renders MICE as a precision experiment which requires strict controls and monitoring of all experimental parameters in order to control systematic errors. The MICE Controls and Monitoring system is based on EPICS and integrates with the DAQ, detector, environment, and data monitoring systems. A description of this system, its implementation, and performance during recent muon beam data collection will be discussed. |
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| MOP038 | Non-Magnetic Momentum Spectrometer Based on Fast Time-of-Flight System | 169 |
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Funding: Supported in part by SBIR Grant DE-SC0005445 A new generation of large-area, low cost time-of-flight detectors with time resolutions ≤ 10 ps and space resolutions ≤ 1 mm is being developed for use in nuclear and particle physics experiments, as well as for medical and industrial applications. Such detectors can serve as the basis for measuring momenta without requiring measurement of curvature in magnetic fields. Factors affecting measurement accuracy and simulation results are presented. |
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| MOP040 | Fast Time-of-Flight System for Muon Cooling Experiments | 172 |
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Funding: Supported in part by SBIR Grant DE-SC0005445. A new generation of large-area, low cost time-of-flight detectors with time resolutions ≤ 10 ps and space resolutions ≤ 1 mm is being developed for use in nuclear and particle physics experiments, as well as for medical and industrial applications. Such detectors are being considered for use in muon cooling channel tests. Designs and fabrication of prototype planes and associated readout electronics are described. Results of simulations of time and space resolutions are presented. |
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| MOP041 | 17 GHz Overmoded Dielectric Photonic Bandgap Accelerator Cavity | 175 |
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Funding: This research is supported by the U.S. Department of Energy, Office of High Energy Physics. We present the design of an overmoded photonic band gap (PBG) accelerator cavity, made from a 2D lattice of sapphire rods supported between copper plates, that operates in a TM02-like mode at 17 GHz. The cavity does not support the lower-frequency TM01-like mode. Higher-order modes are damped effectively by removing rods from the lattice so that only the operating mode is supported with a high quality factor. The TM02 cavity mitigates the high pulsed heating of the copper surface seen in some metal-rod TM01 PBG cavities, which may be an advantage for high-gradient operation. We discuss plans for testing a 17 GHz TM02 standing-wave cavity at gradients above 100 MV/m. |
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| MOP042 | Design of a Superconducting Photonic Band Gap Structure Cell | 178 |
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Funding: This work is supported by the U.S. Department of Energy (DOE) Office of Science Early Career Research Program. We present a design of a superconducting photonic band gap (PBG) accelerator cell operating at 700 MHz. It has been long recognized that PBG structures have great potential in reducing long-range wakefields in accelerators. Using PBG structures in superconducting particle accelerators will allow moving forward to significantly higher beam luminosities and lead towards a completely new generation of colliders for high energy physics. We designed the superconducting PBG cell which incorporates higher order mode (HOM) couplers to conduct the HOMs filtered by the PBG structure out of the cryostat. The accelerator characteristics of the cell were evaluated numerically. A scaled prototype cell was fabricated out of copper at the higher frequency of 2.8 GHz and cold-tested. The 700 MHz niobium cell will be fabricated at Niowave, Inc. and tested for high gradient at Los Alamos in the near future. |
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| MOP043 | Simulations of a Muon Linac for a Neutrino Factory | 181 |
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Funding: Supported in part by DOE grant DE-FG-08ER86351 The Neutrino Factory baseline design involves a complex chain of accelerators including a single-pass linac, two recirculating linacs and an FFAG. The first linac follows the capture and bunching section and accelerates the muons from about 244 to 900 MeV. It must accept a high emittance beam about 30 cm wide with a 10% energy spread. This linac uses counterwound, shielded superconducting solenoids and 201 MHz superconducting cavities. Simulations have been carried out using several codes including Zgoubi, OptiM, GPT, and G4beamline, both to determine the optics and to estimate the radiation loads on the elements due to beam loss and muon decay. |
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| MOP046 | RF Breakdown Studies Using Pressurized Cavities | 184 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE Contract DE-AC02-07CH11359 Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved, and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual gas and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) has been built, and a series of detailed experiments is planned at the Argonne Wakefield Accelerator. These experiments will be followed by additional experiments using a second test cell operating at 402.5 MHz. |
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| MOP047 | Helical Channels with Variable Slip Factor for Neutrino Factories and Muon Colliders | 187 |
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Funding: Supported in part by DOE SBIR grant DE-SC0002739. In order to realize a muon collider or a neutrino factory based on a muon storage ring, the muons must be captured and cooled efficiently. For a muon collider, the resulting train of bunches should be coalesced into a single bunch. Design concepts for a system to capture, cool, and coalesce a muon beam are described here. In particular, variants of a helical channel are used, taking advantage of the ability to vary the slip factor and other parameters of such a channel. The cooling application has been described before; this paper reports recent studies of a system that includes two novel concepts to accomplish capture and coalescing via a slip-controlled helical channel. |
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| MOP050 | EPIC Muon Cooling Simulations using COSY INFINITY | 190 |
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| Next generation magnet systems needed for cooling channels in both neutrino factories and muon colliders will be innovative and complicated. Designing, simulating and optimizing these systems is a challenge. Using COSY INFINITY, a differential algebra-based code, to simulate complicated elements can allow the computation and correction of a variety of higher order effects, such as spherical and chromatic aberrations, that are difficult to address with other simulation tools. As an example, a helical dipole magnet has been implemented and simulated, and the performance of an epicyclic parametric ionization cooling system for muons is studied and compared to simulations made using G4Beamline, a GEANT4 toolkit. | ||
| MOP051 | End-to-End Simulation of an Inverse Cyclotron for Muon Cooling | 193 |
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Funding: DOE Office of High-Energy Physics, SBIR DE-FG02-08ER85044 Neutrino factories and muon colliders require significant cooling of the muon beam. Most muon cooling channels are long and expensive single-pass structures, due to the difficulty injecting very large emittance beams into a circular device. Inverse cyclotrons can potentially solve the injection problems associated with other circular cooling channels, and they can potentially provide substantial initial cooling of the beam. We present the first end-to-end (injection to extraction) simulations of an inverse cyclotron for muon cooling, performed with the particle-in-cell code VORPAL. We study the cooling capability of the device as well as potential limitations due to space charge effects and material interactions with the beam. |
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| MOP052 | Matched Optics of Muon RLA and Non-Scaling FFAG ARCS | 196 |
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Funding: Supported in part by US DOE STTR Grant DE-FG02-08ER86351 Recirculating Linear Accelerators (RLA) are an efficient way of accelerating short-lived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. To reduce the number of required return arcs, we employ a Non-Scaling Fixed-Field Alternating-Gradient (NS-FFAG) arc lattice design. We present a complete linear optics design of a muon RLA with two-pass linear NS-FFAG droplet return arcs. The arcs are composed of symmetric cells with each cell designed using combined function magnets with dipole and quadrupole magnetic field components so that the cell is achromatic and has zero initial and final periodic orbit offsets for both passes’ energies. Matching to the linac is accomplished by adjusting linac quadrupole strengths so that the linac optics on each pass is matched to the arc optics. We adjust the difference of the path lengths and therefore of the times of flight of the two momenta in each arc to ensure proper synchronization with the linac. We investigate the dynamic aperture and momentum acceptance of the arcs. |
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| MOP053 | Measurement of Neutral Particle Contamination in the MICE Muon Beam | 199 |
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Funding: NSF The Muon Ionization Cooling Experiment (MICE) is being built at the ISIS proton synchrotron at Rutherford Appleton Laboratory (RAL) to test ionization cooling of a muon beam. Production of particles in the MICE beamline begins with a titanium target dipping into the ISIS proton beam. The resulting pions are captured, momentum-selected, and fed into a 5T superconducting solenoid. This magnet contains the pions and their decay muons which are then sent through the rest of the MICE beamline toward the cooling channel. During recent data-taking, it was determined that there is a significant background contamination of neutral particles populating the MICE muon beam. This contamination creates unwanted triggers in MICE, thus reducing the percentage of useful data taken during running. This paper describes the analysis done with time-of-flight detectors, used to identify particle type, in order to understand the level of contamination in both positive and negative polarity muon beams. |
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| MOP054 | Racetrack Muon Ring Cooler Using Dipoles and Solenoids for a Muon Collider | 202 |
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Funding: DOE Grant No. DE-FG02-92ER40695 A racetrack muon ring cooler for a muon collider is considered. The achromatic cooler uses both dipoles and solenoids. We describe the ring lattice and show the results of beam dynamic simulation that demonstrates a large aperture for acceptance. We also examine the 6D cooling of the muon beam in the cooler and discuss the prospects for the future. |
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| MOP055 | Robust 6D Muon Cooling in Four-sided Ring Cooler using Solenoids and Dipoles for a Muon Collider | 205 |
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Funding: DOE Grant No. DE-FG02-92ER40695 We present a four-sided ring cooler that employs both dipoles and solenoids to provide robust 6D muon cooling of large emittance beams in order to design and build a muon collider. Our studies show strong 6D cooling adequate for components of a muon collider front end. |
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| MOP056 | A Compact and High Performance Muon Capture Channel for Muon Accelerators | 208 |
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Funding: Work is funded by U.S. Dept. of Energy grant numbers DE AC02-98CH10886. It is widely believed that a neutrino factory would deliver unparallel performance in studying neutrino mixing and would provide tremendous sensitivity to new physics in the neutrino sector. Here we will describe and simulate the front-end of the neutrino factory system, which plays critical role in determining the number of muons that can be accepted by the downstream accelerators. In this system, a proton bunch on a target creates secondaries that drift into a capture transport channel. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to nearly equal central energies, and initiates ionization cooling. For this, the muon beams are transported through sections containing high-gradient cavities and strong focusing solenoids. In this paper we present results of optimization and variation studies toward obtaining the maximum number of muons for a neutrino factory by using a compact transport channel. Stratakis et al. Phys. Rev. ST Accel. Beams 14, 011001 (2011). |
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| MOP057 | A SLAB Dielectric Structure as a Source of Wakefield Acceleration and THz Cherenkov Radiation Generation | 211 |
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Funding: Work is funded by US Dept. of Energy grant numbers DE-FG03-92ER40693. Acceleration of electrons in wakefields set up by a series of drive bunches in a dielectric structure has been proposed as a possible component of next-generation accelerators. Here, we discuss future experimental work with a slab sub-millimeter dielectric loaded accelerator structure that in contrast to conventional dielectric tubes should diminish the effects of transverse wakes and will permit higher total charge to be accelerated. The proposed experiment will allow the generation of unprecedented peak power at THz frequencies. In addition, it can generate ~50-150 MV/m drive fields and thus will allow the testing of acceleration using witness and drive beams. We examine details of the geometry and composition of the structures to be used in the experiment. |
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| MOP058 | Particle Production in the MICE Beamline | 214 |
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Funding: NSF The Muon Ionization Cooling Experiment (MICE) will test transverse cooling of a muon beam, satisfying a crucial demonstration step along the path toward creating high intensity muon beams in a Neutrino Factory or Muon Collider. In the last year, MICE has taken a record amount of data to commission the beamline and calibrate the particle identification (PID) detectors. Studies of the MICE beamline and target timing will be discussed, including the use of Time-of-Flight (TOF) detectors to understand the MICE beam content. |
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| MOP059 | Simulations of the Tapered Guggenheim 6d Cooling Channel for the Muon Collider | 217 |
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Funding: Work is supported by the U.S. Department of Energy. Recent progress in six-dimensional (6D) cooling simulations for the Muon Collider based on the RFOFO ring layout is presented. In order to improve the performance of the cooling channel a tapering scheme is studied that implies changing the parameters such as cell length, magnetic field strength, RF frequency, and the amount of the absorbing material along the cooling channel. This approach allows us to keep the cooling rates high throughout the process. The results of the simulations carried out in G4beamline are presented. |
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| MOP060 | Wedge Absorber Design and Simulation for MICE Step IV | 220 |
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Funding: Work is supported by the Science and Technology Facilities Council, the U.S. Department of Energy and the U.S. National Science Foundation. In the Muon Ionization Cooling Experiment (MICE), muons are cooled by passing through material, then through RF cavities to compensate for the energy loss; which reduces the transverse emittance. It is planned to demonstrate longitudinal emittance reduction via emittance exchange in MICE by using a solid wedge absorber in Step IV. Based on the outcome of previous studies, the shape and material of the wedge were chosen. We address here further simulation efforts for the absorber of choice as well as engineering considerations in connection with the absorber support design. |
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| MOP061 | Stability of the MICE Muon Beam Line | 223 |
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Funding: University of Chicago The international Muon Ionization and Cooling Exper- iment (MICE) aims to demonstrate transverse beam emit- tance reduction for a muon beam. During the summer of 2010, data was taken using different configurations of the upstream beam line magnets to measure the optical pa- rameters of the muon beam and study the functionality of the beam line itself. Throughout this period of data taking, reference runs were taken with a fixed target configuration, and magnet settings which provide a muon beam with 200 MeV/c momentum and 6π 4D transverse emittance. Time of flight (TOF) detectors were used to measure many of the beam properties including emittance, particle identifi- cation, and profile. Analysis of these reference runs was carried out in order to determine the stability and repro- ducibility of the beam line data. This overall data quality check is essential to ensure the validity of measurements made so that further analysis can be carried out and that the muon beam is suitable for the MICE cooling channel. |
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| MOP062 | Usage of Li-rods for Ionization Cooling of Muons | 226 |
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| Four different schemes of final ionization cooling are discussed. The first scheme is the straight channel based on lithium rods, which can provide only 4D cooling, but which can be modified to obtain 6D cooling. The helical orbit scheme with decrement redistribution is one such modification. Two other modifications use emittance redistribution and emittance exchange procedures, respectively, to transfer phase-space volume from longitudinal to transverse degrees of freedom (where the transverse degrees of freedom alternate for each successive exchange or redistribution). By emittance redistribution is meant a arbitrary redistribution of phase-space volume from one degree of freedom to another and by emittance exchange is meant a symplectic operation of emittance swap. Estimates of the final emittance, calculations of the technical parameters and simulations of beam movement are presented for each scheme. The study focused on the scheme with emittance exchange because it looks the most promising and simple, both conceptually and in terms of implementation, and it can also extend the cooling process to handle a larger initial emittance relative to the basic straight channel scheme. | ||
| MOP064 | Asymmetric Laser Radiant Cooling in Storage Rings | 229 |
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| Laser pulses with small spatial and temporal dimensions can interact with a fraction of the electron bunches circulating in Compton storage rings. We studied synchrotron dynamics of such bunches when laser photons scatter off from the electrons with energy higher than the synchronous energy. In this case of ‘asymmetric cooling', as shown theoretically, the stationary energy spread is much smaller than under conditions of regular scattering; the oscillations are damped faster. Coherent oscillations of large amplitude may be damped in one synchrotron period, which makes this method feasible for injection the bunches into a ring in the longitudinal phase space. The theoretical results are validated with simulations. | ||
| MOP066 | Effects of e-beam Parameters on Coherent Electron Cooling | 232 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Coherent Electron Cooling (CeC) requires detailed con- trol of the phase between the hadron an the FEL-amplified wave packet. This phase depends on local electron beam parameters such as the energy spread and the peak current. In this paper, we examine the effects of local density variations on the cooling rates for CeC. |
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| MOP067 | Vlasov and PIC Simulations of a Modulator Section for Coherent Electron Cooling | 235 |
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Funding: This work is supported by the US DOE Office of Science, Office of Nuclear Physics, grant numbers DE-SC0000835 and DE-FC02-07ER41499. Resources of NERSC were used under contract No. DE-AC02-05CH11231. Next generation ion colliders will require effective cooling of high-energy hadron beams. Coherent electron cooling (CEC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques. We present Vlasov-Poisson and delta-f particle-in-cell (PIC) simulations of a CEC modulator section. These simulations correctly capture the subtle time and space evolution of the density and velocity wake imprinted on the electron distribution via anisotropic Debye shielding of a drifting ion. We consider 1D and 2D reduced versions of the problem, and compare the exact solutions of Wang and Blaskiewicz with Vlasov-Poisson and delta-f PIC simulations. We also consider interactions under non-ideal conditions where there is a density gradient in the electron distribution, and present simulations of the ion wake. * V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009). |
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| MOP071 | Terahertz Light Source and User Area at FACET | 238 |
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Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515. FACET at SLAC provides high charge, high peak current, low emittance electron beam that is bunched at THz wavelength scale during its normal operation. A THz light source based coherent transition radiation (CTR) from this beam would potentially be the brightest short-pulse THz source ever constructed. Efforts have been put into building this photon source together with a user area, to provide a platform to utilize this unique THz radiation for novel nonlinear and ultrafast phenomena researches and experiments. |
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| MOP072 | Design of On-Chip Power Transport and Coupling Components for a Silicon Woodpile Accelerator | 241 |
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| Three-dimensional woodpile photonic bandgap (PBG) waveguide enables high-gradient and efficient laser driven acceleration, while various accelerator components, including laser couplers, power transmission lines, woodpile accelerating and focusing waveguides, and energy recycling resonators, can be potentially integrated on a single monolithic structure via lithographic fabrications. This paper will present designs of this on-chip accelerator based on silicon-on-insulator (SOI) waveguide. Laser power is coupled from free-space or fiber into SOI waveguide by grating structures on the silicon surface, split into multiple channels to excite individual accelerator cells, and eventually gets merged into the power recycle pathway. Design and simulation results will be presented regarding various coupling components involved in this network. | ||
| MOP074 | Simulations of a Single-Pass Through a Coherent Electron Cooler for 40 Gev/n Au+79 | 244 |
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Funding: US DOE Office of Science, Office of Nuclear Physics, grant No.’s DE-FG02-08ER85182 and DE-FC02-07ER41499. NERSC resources were supported by the DOE Office of Science, contract No. DE-AC02-05CH11231. Increasing the luminosity of ion beams in particle accelerators is critical for the advancement of nuclear and particle physics. Coherent electron cooling promises to cool high-energy hadron beams significantly faster than electron cooling or stochastic cooling. Here we show simulations of a single pass through a coherent electron cooler, which consists of a modulator, a free-electron laser, and a kicker. In the modulator the electron beam copropagates with the ion beam, which perturbs the electron beam density according to the ion positions. The FEL, which both amplifies and imparts wavelength-scale modulation on the electron beam. The strength of modulated electric fields determines how much they accelerate or decelerate the ions when electron beam recombines with the dispersion-shifted hadrons in the kicker region. From these field strengths we estimate the cooling time for a gold ion with a specific longitudinal velocity. * Vladimir N. Litvinenko, Yaroslav S. Derbenev, Physical Review Letters 102, 114801 (2009) |
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| MOP081 | Proton Acceleration by Trapping in a Relativistic Laser Driven Uphill Plasma Snowplow | 247 |
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| We explore a novel regime of proton and ion acceleration off of overdense Plasma created by a Laser pulse. In Coulomb explosion, Target Normal Sheath, Acoustic shock acceleration regimes the protons are neither high-energy nor monoenergetic enough for applications such as hadron radiation therapy, fast ignition fusion research and particle physics. This calls out for exploration of effective regimes of acceleration. The proposed Snowplow regime of acceleration uses a Snowplow of charge created by a relativistic Laser pulse at the critical density on a uphill Plasma density gradient. The relativistically moving Snowplow's space charge drags the protons and its velocity can be controlled to effectively trap the protons using laser pulse shape and the uphill density profile. We describe the principles behind this mechanism. We derive analytical expressions for the Snowplow velocity and its dependence on the parameter space. We primarily explore the density gradient and laser pulse shape to optimally accelerate protons from rest to the desired velocities. Preliminary, 1-D simulation results are presented and analyzed. | ||
| MOP082 | Modeling a 10 GeV Laser-Plasma Accelerator with INF&RNO | 250 |
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Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The numerical modeling code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde, pronounced "inferno") is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a particle-in-cell (PIC) or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged ponderomotive force. These and other features allow for a significant speedup compared to standard full PIC simulations while still retaining physical fidelity. A boosted Lorentz frame (BLF) modeling capability has been introduced within the fluid framework enhancing the performance of the code. An example of a 10 GeV laser-plasma accelerator modeled using INF&RNO in the BLF is presented. |
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| MOP083 | Plasma Wake Excitation by Lasers or Particle Beams | 253 |
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Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. |
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| MOP084 | A High Repetition Plasma Mirror for Staged Electron Acceleration | 256 |
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Funding: Acknowledgment: This work is supported by the National Science Foundation and DTRA. In order to build a compact, staged laser plasma accelerator the in-coupling of the laser beam to the different stages represents one of the key issues. To limit the spatial foot print and thus to realize a high overall acceleration gradient, a concept has to be found which realizes this in-coupling within a few centimeters. We present experiments on a tape-drive based plasma mirror which could be used to reflect the focused laser beam into the acceleration stage. References: * W. Leemans et. al, Phys. Today, 62, 44 (2009) ** G. Doumy et. al, Phys. Rev. E 69, 026402 (2004) *** B. Dromey et. al,, Rev. Sci. Instrum. 75, 645 (2004) |
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| MOP086 | Fabrication of a Prototype Micro-Accelerator Platform | 259 |
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Funding: Work supported by U.S. Defense Threat Reduction Agency, Grant no. HDTRA1-09-1-0043. The Micro-Accelerator Platform is a laser powered particle acceleration device made from dielectric materials. Its main building blocks, distributed Bragg reflectors and nanoscale coupling slots are fabricated using cutting-edge nanofabrication techniques. In this report, a prototype device will be presented, and technical details with fabrication will be discussed. Optical property of the DBR films is measured by ellipsometry, and film surface roughness is measured using profilometer. In addition, a few remaining challenges with manufacture of this device will be discussed. |
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| MOP087 | A Laser-Driven Linear Collider: Sample Machine Parameters and Configuration | 262 |
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Funding: Work supported by Department of Energy contracts DE-AC03-76SF00515 (SLAC) and DE-FG03-97ER41043-III (LEAP). We present a design concept for an e+ e- linear collider based on laser-driven dielectric accelerator structures, and discuss technical issues that must be addressed to realize such a concept. With a pulse structure that is quasi-CW, dielectric laser accelerators potentially offer reduced beamstrahlung and pair production, reduced event pileup, and much cleaner environment for high energy physics and. For multi-TeV colliders, these advantages become significant. |
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| MOP088 | A High Transformer Ratio Plasma Wakefield Accelerator Scheme for FACET | 265 |
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Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 The ideal drive beam current profile for the plasma wakefield accelerator (PWFA) has been predicted by 1D and 2D simulations to be characterized by a triangular ramp that rises linearly from head to tail, followed by a sharp drop. A technique for generating such bunches experimentally was recently demonstrated. We present here an adaptation of this scheme to generate ramped bunches using the 23 GeV electron beam produced in the first two-thirds of the SLAC linac, and discuss plans to implement this scheme for high transformer ratio demonstration experiments at the FACET plasma wakefield accelerator facility. |
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| MOP090 | Optics Tuning Knobs for FACET | 268 |
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Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. FACET is a new facility under construction at the SLAC National Accelerator Laboratory. The FACET beam line is designed to provide 23 GeV tightly focused and compressed electron and positron bunches for beam driven plasma wakefield acceleration research and other experiments. Achieving optimal beam parameters for various experimental conditions requires the optics capability for tuning in a sufficiently wide range. This will be achieved by using optics tuning systems (knobs). Design of such systems for FACET is discussed. |
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| MOP093 | Precision Monitoring of Relative Beam Intensity | 271 |
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Funding: U.S. Department of Energy. For future experiments at the intensity frontier, precise and accurate knowledge of beam time structure will be critical to understanding backgrounds. The proposed Mu2e experiment will utilize ~150nsec (FWHM) bunches of 107 protons at 8 GeV with a bunch-to-bunch period of 1.7 microseconds. The out-of-bunch beam must be suppressed by a factor of 10-9 relative to in-bunch beam and continuously monitored. I propose a Cerenkov based particle telescope to measure secondary production from beam interactions in a several tens of microns thick foil. Correlating timing information with beam passage allows the determination of relative beam intensity to arbitrary precision given a sufficiently long integration time. The goal is to verify out-of-bunch extinction to the level 10-6 in the span of several seconds. This allows near real-time monitoring of the initial extinction of the beam slow extracted from Fermilab's Debuncher before a system of AC dipoles and collimators, which will provide the final extinction. The effect on beam emittance is minimal, allowing the necessary continuous measurement. I will present the detector design and results of a test in Fermilab's MI-12 beamline. |
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| MOP094 | Development of Advanced Beam Halo Diagnostics at the Jefferson Lab Free-Electron-Laser Facility | 274 |
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Funding: Many colleagues at JLab FEL provided help with the installation of the present experimental setup. This work is partially supported by DOE Contract DE-AC05-060R23171. High average current and high brightness electron beams are needed for many applications. At the Jefferson Lab FEL facility, the search for dark matter with the FEL laser beam has produced interesting results*, and a second very promising method for dark matter search using JLab Energy-recovery-linac (ERL) machine has been put forward**. Although the required beam current has been achieved on this machine, one key challenge is the management of beam halo. UMD has demonstrated a high dynamic range halo measurement method using a digital micro-mirror array device. A similar system has been established at JLab FEL facility as a joint effort by UMD and JLab to measure the beam halo on the high current ERL machine***. The experiment and characterization are being performed while the new UV FEL is running for optimization. In this paper, the limitations of the current system will be analyzed and study of other approaches (such as an optimized coronagraph) for further extending measuring dynamic range will be presented. In particular, we will discuss in detail the possibility of performing both longitudinal and transverse (3D) halo measurement altogether on one single system. * A. Afanasev, et al., PRL. 101 120401 (2008). ** J. Thale, Searching for a New Gauge Boson at JLab, Newport News, VA, September 20-21, 2010 *** H. Zhang, et al., this conference. |
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| MOP095 | Experimental Determination of Damage Threshold Characteristics of IR Compatible Optical Materials | 277 |
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Funding: Work funded by DOE contract DE‐AC02‐76SF00515 (SLAC) The accelerating gradient in a laser-driven dielectric accelerating structure is often limited by the laser damage threshold of the structure. For a given laser-driven dielectric accelerator design, we can maximize the accelerating gradient by choosing the best combination of the accelerator’s constituent material and operating wavelength. We present here a model of the damage mechanism from ultrafast infrared pulses and compare that model with experimental measurements of the damage threshold of bulk silicon. Additionally, we present experimental measurements of a variety of candidate materials, thin films, and nanofabricated accelerating structures. |
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| MOP096 | Fabrication and Measurement of Dual Layer Silica Grating Structures for Direct Laser Acceleration | 280 |
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Funding: Department of Energy: DE-AC02-76SF00515(SLAC),DE-FG06-97ER41276 We present our progress in the fabrication and measurement of a transmission-based dielectric double-grating accelerator structure. The structure lends itself to simpler coupling to the accelerating mode in the waveguide with negligible group velocity dispersion effects, allowing for operation with ultra-short (fs) laser pulses. This document describes work being done at the Stanford Nanofabrication Facility to create a monolithic guided-wave structure with 800 nm period gratings separated by a fixed sub-wavelength gap using standard optical lithographic techniques on a fused silica substrate. An SEM and other characterization tools were used to measure the fabrication deviations of the grating geometry and simulations were carried out in MATLAB and HFSS to study the effects of such deviations on the resulting accelerating gradient. |
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| MOP097 | Modeling of Quasi-Phase Matching for Laser Electron Acceleration | 283 |
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Funding: This work is supported by the Defense Threat Reduction Agency through contract HDTRA1-10-1-0034. Sensing of shielded fissile materials at long range is critically dependent on the development of compact particle accelerators. Direct laser acceleration (DLA) of electrons has the potential to meet this requirement. In DLA, the axial component of the electric field of a focused radially polarized laser pulse accelerates particles. The acceleration gradient could be estimated as 77 MeV/mm for 800 nm laser with power of 0.5 TW and 8.5 μm guided mode radius. The implementation of long guided propagation of laser pulses and the phase matching between electrons and laser pulses may limit the DLA in reality. A preformed corrugated plasma waveguide could be applied to extend the laser beam propagation distance and for quasi-phase matching between laser and electron pulses for net acceleration. We perform numerical calculations to estimate the phase matching conditions for a radially polarized laser pulse propagating in a corrugated plasma waveguide. Further, the electric field distribution of a radially polarized laser pulse propagating in this waveguide is also analyzed via particle-in-cell simulations, and will be used to guide future experiments. * P. Serafim, et al., IEEE Trans. Plasma Sci. 28, 1155 (2000). ** A.G. York, et al., Phys. Rev. Lett. 100, 195001 (2008). |
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| MOP101 | Numerical Study of Self and Controlled Injection in 3-Dimensional Laser-Driven Wakefields | 286 |
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Funding: DOE and NSF In plasma based accelerators (LWFA and PWFA), the methods of injecting high quality electron bunches into the accelerating wakefield is of utmost importance for various applications. Understanding how injection occurs in both self and controlled scenarios is therefore important. To simplify this understanding, we start from single particle motion in an arbitrary traveling wave wakefields, an electromagnetic structure with a fixed phase velocity(e.g., wakefields driven by non-evolving drivers), and obtain the general conditions for trapping to occur. We then compare this condition with high fidelity 3D PIC simulations through advanced particle and field tracking diagnostics. Numerous numerical convergence tests were performed to ensure the correctness of the simulations. The agreement between theory and simulations helps to clarify the role played by driver evolution on injection, and a physical picture of injection first proposed in * is confirmed through simulations. Several ideas, including ionization assisted injection, for achieving high quality controlled injection were also explored and some simulation results relevant to current and future experiments will be presented. *W. Lu et al., PRSTAB 10, 061301, 2007 |
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| MOP102 | High-Gradient High-Energy-Gain Inverse Free Electron Laser Experiment using a Helical Undulator | 289 |
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Funding: UC Lab fee award 09-LR-04-117055-MUSP DOE-HEP grant DE-FG02-92ER40693 Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0073 Preparations for a high energy gain inverse free electron laser (IFEL) experiment using an undulator and Brookhaven National Lab’s (BNL) Accelerator Test Facility’s (ATF) terawatt CO2 laser are underway. 3D simulations suggest that the experiment will likely accelerate a 50 MeV beam to 117 MeV in 54 cm while maintaining a low energy spread. The helical undulator is currently under construction at UCLA’s Particle Beam Physics Laboratory. |
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| MOP104 | Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure | 292 |
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Funding: Work funded by DOE contract DE‐AC02‐76SF00515 (SLAC) A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. |
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| MOP106 | Electron Acceleration via Positron Driven Plasma Wakefield Accelerator | 295 |
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Funding: Work supported by US DoE and NSF. We show that a positron bunch with parameters accessible at FACET can excite a stable plasma wakefield over a few meters and a witness electron bunch experiences an accelerating gradient on the order of 10 GeV/m. Initial simulations show that the positron drive bunch is strongly affected by the transverse components of the wakefield: the positron bunch evolves significantly, which affects both the wakefield and witness bunch dynamics. Various solutions are presented, of which the positron-electron train shceme generates a desirable wakefield. |
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| MOP107 | Status of Dielectric-Lined Two-Channel Rectangular High Transformer Ratio Accelerator Structure Experiment | 298 |
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Funding: This work is supported by DoE, Office of High Energy Physics Recent tests of a two-channel rectangular dielectric lined accelerator structure are described; comparison with theory and related issues are presented. The structure (with channel width ratio 6:1) is designed to have a maximum transformer ratio of ~12.5:1. It operates mainly in the LSM31 mode (~ 30GHz). The dielectric liner is cordierite (dielectric constant ~4.76). The acceleration gradient is 1.2 MV/m for each 10nC of the drive bunch for the first acceleration peak of the wakefield, and 0.92 MV/m for the second peak. The structure is installed into the AWA beam-line (Argonne National Lab) and is excited by a single 10-50nC, 14MeV drive bunch. Both the drive bunch and a delayed witness bunch are produced at the same photocathode. This is the first experiment to test a two-channel dielectric rectangular wakefield device where the accelerated bunch may be continuously energized by the drive bunch. The immediate experimental objective is to observe the energy gain and spread, and thereby draw conclusions from the experimental results and the theory model predictions. The observed energy change of the test bunch might be well explained*. * G. V. Sotnikov, et al., Advanced Accelerator Concepts: 13th Workshop, Carl B. Schroeder, Wim Leemans and Eric Esarey, editors, AIP Conf. Proc. 1086), pp. 415–420 (AIP, New York, 2009). |
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| MOP108 | Simulation Study of Proton-Driven PWFA Based on CERN SPS Beam | 301 |
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| We have proposed an experimental study of the proton-driven plasma wakefield acceleration by using proton beam from the CERN SPS. In this paper, the particle-in-cell (PIC) simulation of the SPS beam-driven plasma wakefield acceleration is introduced. By varying the beam parameters and plasma parameters, simulation shows that electric fields in excess of 1 GeV/m can be achieved. | ||
| MOP112 | Study of Enhanced Transformer Ratio in a Coaxial Dielectric Wakefield Accelerator using a Profiled Drive Bunch Train | 304 |
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Funding: The research was supported by US Department of Energy, Office of High Energy Physics, Advanced Accelerator R & D. A key parameter of wakefield acceleration is the transformer ratio T. For a dielectric wakefield accelerator, it has been suggested to use a ramped drive bunch train (RBT), or a multizone dielectric structure to enhance T. Here we show the possibility of greatly improving the RBT technique by the use of a numerical algorithm. We study a two-channel 28 GHz structure with two nested Alumina cylindrical shells (CDWA) which is to be excited by a train of four annular bunches having energy 14 MeV and axial RMS size 1mm; the total charge of bunches is 200 nC. For bunch charge and spacing chosen for optimum acceleration gradient, or for optimizing T using the standard method, we obtain T~3.6. We found that if the charge ratios are 1.0:2.4:3.5:5.0 and the spaces between the bunches are 2.5, 2.5, and 4.5 wakefield periods, then T~17. The RBT also can be used successfully in a high gradient THz CDWA structure. * C.Jing et.al., Phys. Rev. Lett. 98 144801, (2007) ** C. Wang, et.al. Proc. PAC 2005. IEEE, 2005, p.1333. *** G. Sotnikov et.al. PRST-AB, 061302 (2009). |
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| MOP113 | High Quality Electron Beams Generated in a Laser Wakefield Accelerator | 307 |
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Funding: The U.K. EPSRC, the EC's Seventh Framework Programme (LASERLAB-EUROPE / LAPTECH, grant agreement no. 228334) and the Extreme Light Infrastructure (ELI) project. The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laser-plasma accelerators for the production of ultra-short electron beams as drivers of incoherent and coherent radiation sources from plasma and magnetic undulators. Here we report on the latest laser wakefield accelerator experiments on the University of Strathclyde ALPHA-X accelerator beam line looking at narrow energy spread electron beams. ALPHA-X uses a 26 TW Ti:sapphire laser (energy 900 mJ, duration 35 fs) focused into a helium gas jet (nozzle length 2 mm) to generate high quality monoenergetic electron beams with central energy in the range 80-180 MeV. The beam is fully characterised in terms of the charge, transverse emittance, energy spread and bunch length. In particular, the energy spectrum (with less than 1% measured energy spread) is obtained using a high resolution magnetic dipole imaging spectrometer. |
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| MOP115 | Progress on Multipactor Studies in Dielectric-Loaded Accelerating Structures | 310 |
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Funding: DOE SBIR Significant progress has been made in the development of high gradient rf driven dielectric accelerating structures (DLA). One principal effect limiting further advances in this technology is the problem of multipactor. The fraction of the power absorbed at saturation in DLA experiments was found to increase with the incident power, with more than 30% of the incident power per unit length being absorbed. We studied a possibility of multipactor mitigation by introduction of surface grooves (transverse and longitudinal) to interrupt the resonant trajectories of electrons in the multipactor discharge. Four DLA structures based on quartz tubes with transverse and longitudinal grooves of various dimensions were designed. In this paper we report simulation results and plans for high-power tests of these structures. |
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| MOP116 | Development of an X-Band Dielectric-Based Wakefield Power Extractor for Potential CLIC Applications | 313 |
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Funding: Work is funded by DoE SBIR PhaseI. In the past decade, tremendous efforts have been put into the development of the CLIC Power Extraction and Transfer Structure (PETS), and significant progress has been made. However, one concern remains the manufacturing cost of the PETS, particularly considering the quantities needed for a TeV machine. A dielectric-based wakefield power extractor in principle is much cheaper to build. A low surface electric field to gradient ratio is another big advantage of the dielectric-loaded accelerating/decelerating structure. We are currently investigating the possibility of using a cost-effective dielectric-based wakefield power extractor as an alternative to the CLIC PETS. We designed a 12 GHz dielectric-based power extractor which has a similar performance to CLIC PETS with parameters 23 mm beam channel, 240 ns pulse duration, 135 MW output per structure using the CLIC drive beam. In order to study potential rf breakdown issues, as a first step we are building a 11.424 GHz dielectric-based power extractor scaled from the 12 GHz version, and plan to perform a high power rf test using the SLAC 11.424 GHz high power rf source. |
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| MOP117 | Beam Test of a Tunable Dielectric Wakefield Accelerator | 316 |
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Funding: Work supported by US DoE SBIR Grant under Contract # DE-FG02-07ER84822 We report on a collinear wakefield experiment using the first tunable dielectric loaded accelerating structure. Dielectric-based accelerators are generally lacking in approaches to tune the frequency after fabrication. However, by introducing an extra layer of nonlinear ferroelectric which has a dielectric constant sensitive to temperature and DC voltage, the frequency of a DLA structure can be tuned on the fly by controlling the temperature or DC bias. The experiment demonstrated that by varying the temperature of the structure over a 50°C temperature range, the energy of a witness bunch at a fixed delay with respect to the drive beam could be changed by an amount corresponding to more than half of the nominal structure wavelength. |
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| MOP119 | The Dielectric Wakefield Accelerating Structure | 319 |
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Funding: US Department of Energy We report here on the development of THz diamond wakefield structures produced using Chemical Vapor Deposition (CVD) technology*. The diamond structures would be used in a THz generation experiment at the new FACET facility at SLAC. We consider a dielectric based accelerating structure to study of the physical limitations encountered driving >GV/m wakefields in the cylindrical and planar geometries of a dielectric wakefield accelerator (DWA). In a DWA, an ultrashort drive bunch traverses the evacuated central region of the structure, creating Cherenkov wakefields in the dielectric to accelerate a witness bunch. A diamond-based DWA structure will allow a sustained accelerating gradient exceeding breakdown threshold demonstrated with the FFTB experiments**. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric rf structures: high breakdown voltage, extremely low dielectric losses and the highest thermoconductive coefficient available for removing waste heat from the device. *R. J. Barker et al., Modern Microwave and Millimeter-Wave Power Electronics, IEEE Press/Wiley-Interscience, Piscataway NJ 2005, Chapter 7 **M.C. Thompson et al. Phys. Rev.Lett.100:214801, 2008. |
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| MOP121 | Experimental Studies on Coherent Synchrotron Radiation in the Emittance Exchange Line at the Fermilab A0 Photoinjector | 322 |
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| Future accelerators will employ advanced beam conditioning systems such as emittance exchangers to manipulate high brightness beams. Coherent synchrotron radiation (CSR) in the dipoles could limit the performance of the emittance exchanger. In this paper, we report the experimental and simulation studies on measuring coherent synchrotron radiation and its effects on the beam at the A0 photoinjector in the emittance exchange line. We show how CSR can be used to measure bunch length of the beam. We also report on the diagnostic scheme based on a weak skew quad in the emittance exchange line to study the CSR effects on the beam and other beam dynamics. | ||
| MOP123 | Colliding Pulse Injection Control in a Laser-Plasma Accelerator | 325 |
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Funding: This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, NA-22, and in part by the Office of Science under Contract No. DE-AC02-05CH11231. Control of injection into a high gradient laser-plasma accelerator is presented using the beat between two ’colliding’ laser pulses to kick electrons into the plasma wake accelerating phase. Stable intersection and performance over hours of operation were obtained using active pointing control. Dependence of injector performance on laser and plasma parameters were characterized in coordination with simulations. By scanning the intersection point of the lasers, the injection position was controlled, mapping the acceleration length. Laser modifications to extend acceleration length are discussed towards production of tunable stable electron bunches as needed for applications including Thomson gamma sources and high energy colliders. |
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| MOP124 | Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations | 328 |
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Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy pro- vided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators. |
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| MOP127 | The LLNL/UCLA High Gradient Inverse Free Electron Laser Accelerator | 331 |
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Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We describe the Inverse Free Electron Laser (IFEL) accelerator currently under construction at LLNL in collaboration with UCLA. This project combines a strongly tapered undulator with a 10 Hz repetition rate, Ti:Sapphire laser to produce > 200 MeV/m average accelerating gradient over the 50 cm long undulator. The project goal is to demonstrate IFEL accelerator technology that preserves the input beam quality and is well suited for future light source applications. We discuss the accelerator design focusing on issues associated with the use of 800 nm, 100 fs laser pulses. Three-dimensional simulations of the IFEL interaction are presented which guide the choice of laser and electron beam parameters. Finally, experimental plans and potential future developments are discussed. |
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| MOP128 | An Optimized X-band Photoinjector Design for the LLNL MEGa-Ray Project | 334 |
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Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We present an optimized 5 + ½ cell, X-band photoinjector designed to produce 7 MeV, 250 pC, sub-micron emittance electron bunches for the LLNL Mono-Energetic Gamma-Ray (MEGa-Ray) light source. This LLNL/SLAC collaboration modifies a design previously demonstrated to sustain 200 MV/m on-axis accelerating fields*. We discuss the photoinjector operating point, optimized by scaling beam dynamics from S-band photo-guns and by evaluation of the MEGa-Ray source requirements. The RF structure design is presented along with the current status of the photoinjector construction and testing. *A.E. Vlieks, et al., High Energy Density and High Power RF: 6th Workshop, AIP, CP691, p. 358 (2003). |
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| MOP130 | New Studies of X-band Dielectric-loaded Accelerating Structures | 337 |
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Funding: Work supported by the DoE Office of High Energy Physics and ONR. A joint program is under way to study externally driven X-band dielectric-loaded accelerating (DLA) structures and CLIC-type power extraction structures. The structures are designed and fabricated by Argonne National Laboratory and Euclid Techlabs and tested at up to 20 MW drive power using the X-band Magnicon Facility at the Naval Research Laboratory, with additional tests carried out at SLAC. Thus far, tests have been carried out on a large variety of structures fabricated from quartz, alumina, and MCT-20, and the principal problems have been multipactor loading and rf breakdown.* Multipactor loading occurs on the inner surface of the dielectric in a region of strong normal and tangential rf electric fields; rf breakdown occurs principally at discontinuities in the dielectric. Gap-free DLA structures have been tested at 15 MV/m without breakdown. New tests are being prepared to address these two issues. New gap-free structures will make use of a metallic coating on the outer surface of the dielectric in order to permit tapering both the inner and outer diameters for rf matching, while new multipactor studies will examine the use of grooved surfaces to suppress multipactor. * C. Jing, W. Gai, J.G. Power, R. Konecny, W. Liu, S.H. Gold, A.K. Kinkead, S.G. Tantawi, V. Dolgashev, and A. Kanareykin, IEEE Trans. Plasma Sci., vol. 38, pp. 1354–1360, June 2010. |
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| MOP132 | Wakefield Generation in Compact Rectangular Dielectric-Loaded Structures Using Flat Beams | 340 |
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Funding: This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0051, to Northern Illinois University Wakefields with amplitude in the 10's MV/m range can be routinely generated by passing electron beams through dielectric-loaded structures. The main obstacle in obtaining high field amplitude (in the GV/m range) is the ability to focus the high-peak-current electron beam in the transverse plane to micron level, and to maintain the focusing all the way along the dielectric structure. In this paper we explore the use of a flat, high-peak current, electron beams to be produced at the Fermilab's NML facility to drive dielectric loaded structures. Based on beam dynamics simulation we anticipate that we can obtain flat beams with very small vertical size (under 100 microns) and peak current is in excess of 1 kA. We present simulations of the wakefield generation based on theoretical models and PIC simulations with VORPAL. |
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| MOP133 | Fabrication and Measurements of a Silicon Woodpile Accelerator Structure | 343 |
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Funding: DOE grants: DE-AC02-76SF00515 and DE-FG03-97ER41043-II We present results for the fabrication of a silicon woodpile accelerator structure. The structure was designed to have an accelerating mode at 3.95 μm, with a high characteristic impedance and an accelerating gradient of 530 MeV/m. The fabrication process uses standard nanofabrication techniques in a layer-by-layer process to produce a three-dimensional photonic crystal with 400 nm features. Reflection spectroscopy measurements reveal a peak spanning from three to five microns, and are show good agreement with simulations. * Sears, PRST-AB, 11, 101301, (2008). ** Cowan, PRST-AB, 11, 011301, (2008). *** McGuinness, J. Mod. Opt., vol. 56, is. 18, pp. 2142, (2009). **** Lin, Nature, 394, pp. 251 (1998). |
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| MOP136 | Coupler Studies for PBG Fiber Accelerators | 346 |
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Funding: U.S. Dept. of Energy contract DE-AC02-76SF00515 Photonic band gap (PBG) fibers with hollow core defects are being designed and fabricated for use as laser driven accelerators because they appear capable of providing gradients of several GeV/m at picosecond pulse lengths. While we expect to have fiber down to 1.5-2.0 micron wavelengths we still lack a viable means for efficient coupling of laser power into these structures. The reasons for this include the very different character of these TM-like modes from those familiar in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our coupling work in terms of what has been done and the options we are pursuing for both end and side coupling. In both basic coupler types, the symmetry of the PBG crystal leads to significant differences between this and the telecom field. We show that side coupling provides more possibilities and is preferred. Our motivation is to test new fiber for gradient, mode content and throughput on the NLCTA at SLAC. |
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| MOP137 | Predictive Design and Interpretation of Colliding Pulse Injected Laser Wakefield Experiments | 349 |
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Funding: Work supported by DOE, NA-22, and Office of Science, HEP via the SciDAC-2 project ComPASS, grant No DE-FC02-07ER41499. Resources of NERSC were used (DOE contract No DE-AC02-05CH11231). The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtain reproducible and tunable electron bunches with low energy spread and emittance. We present recent particle-in-cell simulations of colliding pulse injection for parameters relevant to ongoing experiments at LBNL. We perform parameter scans in order to determine the best conditions for the production of high quality electron bunches, and compare the results with experimental data. We also evaluate the effect of laser focusing in the plasma channel and of higher order laser mode components on the bunch properties. |
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| MOP141 | Design, Fabrication and Characterization of a Micron-scale Electron Source Based on Field Enhanced Pyroelectric Crystals | 352 |
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| As a part of the Micro-Accelerator Platform (MAP) project, an electron source with a sub-micron size emitter is required. It is also desired that the source produces electrons with energies above the structure's minimum capture energy (about 25 keV) without the use of an external power supply. Field enhanced emission backed by field generation in pyroelectric crystals has been explored for this application. Here we present experimental progress towards characterization of electron, and x-ray emission. Purpose built diagnostics and specialized test assembly for optimized heat transmission are discussed. | ||
| MOP142 | Development of Picosecond CO2 Laser Driver for an MeV Ion Source | 355 |
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Funding: This work is supported by DOE grant DE-FG02-92ER40727. Laser-Driven Ion Acceleration in thin foils has demonstrated high-charge, low-emittance MeV ion beams with a picosecond duration. Such high-brightness beams are very attractive for a compact ion source or an injector for RF accelerators. However in the case of foils scaling of the pulse repetition rate and improving shot-to-shot reproducibility is a serious challenge. CO2 laser-plasma interactions provide a possibility for using a debris free gas jet for target normal sheath acceleration of ions. Gas jets have the advantage of precise density control around the critical plasma density for 10 um pulses (1019 cm-3) and can be run at 1-10 Hz. The master oscillator–power amplifier CO2 laser system at the UCLA Neptune Laboratory is being upgraded to generate 1 J, 3 ps pulses at 1Hz. For this purpose, a new 8 atm CO2 module is used to amplify a 3 ps pulse to ~10 GW level. Final amplification is realized in a 1-m long TEA CO2 amplifier, for which the bandwidth necessary for 3 ps pulses is provided by the field broadening mechanism. Modeling of the pulse amplification shows that ~0.3 TW power is achievable that should be sufficient for producing 1-3 MeV H+ protons from the gas plasma. |
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| MOP143 | Enhanced Laser-Driven Ion Acceleration via Forward Raman Scattering in a Ramped Gas Target | 358 |
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Funding: This work is supported by DOE grant DE-FG02-92ER40727. CO2 laser-plasma interactions provide a unique parameter space for using a gas jet for Target Normal Sheath Acceleration (TNSA) of ions instead of a thin foil target. The generation of 1-5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density (1019 cm-3) has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma, having similar to the gas jet symmetric, linearly ramped density distribution, occurs via formation of a sheath of hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. This mechanism of an additional heating of electrons is strongly affected by nonlinear laser-plasma interactions and results in the proton energy enhancement by more than an order of magnitude in comparison with the regular ponderomotive force scaling of TNSA. Forward directed ion beams from a gaseous target can find an application as a high-brightness ion source-injector. |
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| MOP144 | Multi-Harmonic Cavity for RF Breakdown Studies | 361 |
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Funding: DOE, Office of HEP An axially-asymmetric cavity to support several modes at harmonically-related frequencies is predicted to sustain higher RF breakdown thresholds than a conventional pillbox cavity, when driven by two or more external RF phase-locked harmonic sources. Experimental efforts are underway at Yale Beam Physics Lab to study RF breakdown in a bimodal asymmetric cavity. Such a cavity could be a basic building-block for a future high-gradient warm accelerator structure. * S.Yu. Kazakov, S.V. Kuzikov, Y. Jiang, and J.L. Hirshfield, PRSTAB, 13, 071303 (2010). ** S.V. Kuzikov, S.Yu. Kazakov, Y. Jiang, and J.L. Hirshfield, PRL 104, 214801 (2010). |
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| MOP145 | Physics Design of the Project X CW Linac | 364 |
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| The general design of the 3 GeV superconducting CW linac of the Project X is presented. Different physical and technical issues and limitations that determine the linac concept are discussed. The results of the RF system optimization are presented as well as the lattice design and beam dynamics analysis. | ||
| MOP146 | Investigation of Synchro-Betatron Couplings at S-LSR | 367 |
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| Tune couplings of beam were observed at S-LSR, Kyoto University. Synchrotron oscillation in the longitudinal direction and betatron oscillation in the horizontal direction was intentionally coupled in a drift tube located at the finite dispersive section. Horizontal and vertical coupling of betatron oscillation was also observed. This fact is a good sign of 3-D couplings to achieve a theoretically predicted crystal beam through the resonant coupling method for transverse laser cooling. | ||
| MOP147 | Experimental Study of Magnetically Confined Hollow Electron Beams in the Tevatron as Collimators for Intense High-Energy Hadron Beams | 370 |
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Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP). Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and tested at Fermilab for this purpose. It was installed in one of the Tevatron electron lenses in the summer of 2010. We present the results of the first tests of the hollow-beam collimation concept on individual 980-GeV antiproton bunches in the Tevatron. |
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| MOP152 | G4beamline Particle Tracking in Matter Dominated Beam Lines | 373 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86281 The G4beamline program is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available. |
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| MOP153 | High Efficiency Laser Ion Acceleration in Low Density Plasmas | 376 |
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| Laser driven sources of high energy ions commonly use thin solid foils. A gaseous target can also produce ion beams with characteristics comparable to those obtained with solid targets. Using Particle-In-Cell simulations, we have studied in detail ion acceleration with high intensity laser pulses interacting with low density plasmas. A two-step acceleration process can be triggered: first, ions are accelerated in volume by electric fields generated by hot electrons, second, the ion energy is boosted in a strong electrostatic shock. 2D and 3D simulations show the potential of this regime. It is possible to model separately these two steps. In the first step a hot electron population and a descending density profile are necessary, and the second step develops if a fast proton wave enters in a low density plasma. | ||
| MOP154 | Prospects for Proton Accelerators Driven by the Radiation Pressure from a Sub-PW CO2 Laser | 379 |
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Funding: DOE Laser acceleration of ion beams is normally realized via irradiating thin-foil targets with near-IR solid-state lasers with up to petawatt (PW) peak power. Despite demonstration of significant achievements, further progress towards practical application of such beam sources is hindered by the challenges inherent in constructing still more intense and higher-contrast lasers. Our recent studies of the radiation pressure acceleration indicate that the combination of a 10-μm CO2 laser with a gas jet target offers a unique opportunity for a breakthrough in the field. Strong power scaling of this regime holds the promise of achieving the hundreds of MeV proton beams with just sub-PW CO2 laser pulses. Generation of such pulses is a challenging task. We discuss a strategy of the CO2 laser upgrade aimed to providing a more compact and economical hadron source for cancer therapy. This include optimization of the method of the 10μm short-pulse generation, higher amplification in the CO2 gas under combined isotopic and power broadening effects, and the pulse shortening to a few laser cycles (150-200 fs) via self-chirping in the laser-produced plasma and the consecutive dispersive compression. |
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| MOP155 | Progress on Diamond Amplified Photo Cathode | 382 |
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Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE Two years ago, we obtained an emission gain of 40 from the Diamond Amplifier Cathode (DAC) in our test system. In our current systematic study of hydrogenation, the highest gain we registered in emission scanning was 178. We proved that our treatments for improving the diamond amplifiers are reproducible. Upcoming tests planned include testing DAC in a RF cavity. Already, we have designed a system for these tests using our 112 MHz superconducting cavity, wherein we will measure DAC parameters, such as the limit, if any, on emission current density, the bunch charge, and the bunch length. |
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| MOP156 | Status of the Polarized SRF Photocathode Gun Design | 385 |
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Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-FG02-06ER84450. A polarized SRF photocathode gun is being considered as a high-brightness electron injector for the International Linear Collider (ILC). The conceptual engineering analysis and design of this injector, which is required to deliver a large emittance ratio, is presented. The delivered beam parameters we predict are compared to the required performance after the ILC damping ring. The analysis indicates that it may be possible to save cost by eliminating the damping ring though higher values of the emittance ratio are still to be demonstrated. |
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| MOP157 | Testing a GAAS Cathode in SRF Gun | 388 |
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Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode’s surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1⁄2 cell SRF gun, the vacuum can be maintained at nearly 10-12 Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun. |
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| MOP158 | Numerical Study of Plasma Wakefields Excited by a Train of Electron Bunches | 391 |
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Funding: Work supported by the US department of Energy We study numerically the excitation of plasma wakefields by a train of electron bunches using the UCLA particle-in-cell code Quickpic*. We aim to find an optimal regime that combines both the advantages of linear and non-linear plasma wakefield accelerator. On one hand, the longitudinal electric field excited by individual bunches add as in the linear region, and the transformer ratio can be maximized (i.e. much larger than 2) by adjusting the number of particles in the bunches as well as their distance. On the other hand, the bunches create large wakefield independent of transverse sizes evolution while propagating through the plasma as in the non-linear region. In principle, such a scheme can multiply the energy of the witness bunch following the drive bunch train in a single plasma wakefield accelerating stage. The parameters for electron bunches are chosen based on the current experiment at the Brookhaven National Laboratory Accelerator Test Facility (ATF), where this scheme can be tested. Detailed simulation results will be presented. * C. Huang, J. Comp. Phys. |
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| MOP159 | Ionization-Induced Trapping in Laser-Plasma Accelerators and Synchrotron Radiation from the Betatron Oscillation | 394 |
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Funding: This work is supported by the U.S. DOE Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and NNSA, NA-22, and used the computational resources of NERSC. Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR). |
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| MOP161 | Undulator-based Laser Wakefield Accelerator Electron Beam Diagnostic | 397 |
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Funding: This work is supported by DTRA and DOE-HEP. The design and current status of experiments to cou- ple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented. * W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006). ** C.B. Schroeder et al., Proceedings AAC08 Conference (2008). *** F. Grüner et al., Appl. Phys. B, 86(3):431–435 (2007). |
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| MOP162 | Betatron Radiation from an Off-axis Electron Beam in the Plasma Wakefield Accelerator | 400 |
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Funding: supported by US DoE In the non-linear or blow-out regime of a plasma wakefield, the electrons of the accelerated bunch oscillate in a pure ion column. It was demonstrated that a single bunch can emit betatron radiation in the keV to MeV range*. In a drive/witness bunch system, the witness bunch can be injected into the ion column with a transverse momentum or initial radial offset, so that the whole bunch oscillates about the column axis as one marcro-electron. This results in a larger emitted power and higher photon energy. The energy loss due to radiation can be compensated for by the energy gain from the wakefield so that the emission process can be sustained over long distance. Detailed results will be presented about the characteristics of the witness bunch oscillations and radiation through numerical simulations** and calculations. * S.Q. Wang, et al., Phys. Rev.Let., 88(13), 135004,(2002), D. K. Johnson et al., Phys. Rev. Lett. 97(17), 175003, (2006) ** C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006) |
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| MOP165 | Bringing Accelerator Models to the Control System Studio | 403 |
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| This paper is the next logical step in the evolution of the new EPICS-based high-level accelerator application environment. The project presents the connection of its middle layers servers with the new Eclipse-based operational toolkit, Control System Studio. The approach is illustrated by the implementation of the Model Independent Analysis application involving three key servers: Machine, Online Model, and Virtual Accelerator. | ||
| MOP166 | Comissioning of a BPM system for the LNLS Booster to Storage Ring Transfer Line | 405 |
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| In order to increase the number of diagnostics and make possible studies of beam position effects in the injection efficiency, a beam position monitoring system was designed to equip the BTS (booster to storage ring) transfer line employing the long striplines BPMs. The log-ratio technique was applied using a commercial electronics module (LR-BPM) from Bergoz Instrumentation. Currently the system is integrated to the LNLS control system, database and ready to be used routinely during the injections. This work describes the system topology, details about the hardware and software, bench tests and measurements performed with electron beam. Future plans to improve the injection efficiency will also be presented. | ||
| MOP169 | Optical Beam Diagnostics at ELSA | 408 |
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Funding: Funded by the DFG within the SFB / TR 16. The Electron Stretcher Facility ELSA consists of several accelerator stages, the last one being a storage ring providing a beam of polarized electrons of up to 3.5 GeV. At ELSA various diagnostic devices based on synchrotron radiation are installed or planned. A new beamline at the storage ring designed for high resolution diagnostics in the transversal plane will be presented. The measurement setup is sensitive at the UV range of the synchrotron light spectrum. Upgrade measures aiming to extend the diagnostic possibilities to the longitudinal direction will be detailed. In the external beamlines beam currents below 1 nA are delivered to photo production experiments. Beam profiles are detected using dedicated synchrotron light monitors optimized for low intensities. The characteristics of the monitors will be described. In addition, beam parameters derived from the measured profiles at different resonance extraction setups will be shown. |
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| MOP170 | Combining Multiturn and Closed-Orbit Methods for Model-Independent and Fast Determination of Optical Functions in Storage Rings | 411 |
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| Multiturn / turn-by-turn data acquisition is a new source for Twiss parameter determination in storage rings, while closed-orbit measurements are a long-known tool for diagnostics with conventional low-frequency beam position monitor (BPM) systems, being available at almost every storage ring. The presented method aims to join the advantages of multiturn and closed-orbit measurement methods. For uncoupled optics, there are only two correctors per oscillation plane and two multiturn BPMs needed in one drift space in the storage ring for model-independent measurement of beta and betatron phase functions at all BPMs in the ring, including conventional ones. This is a cost-effective alternative to the exclusive usage of multiturn BPMs in a storage ring, resulting in the same amount of information. This method can also be extended to include betatron coupling. In addition, we describe a possible experimental setup needed for multiturn data acquisition using a bunch-by-bunch feedback system. By applying an uncritical coherent excitation to coupled bunch modes, the accuracy of the multiturn data acquisition may be significantly improved, enabling the use of smaller drift spaces. | ||
| MOP174 | The Study and Implementation of Signal Processing Algorithm for Digital Beam Position Monitor | 414 |
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| Digital beam position monitor (DBPM) system is one of the most important beam diagnostic instruments generally used in modern accelerators. The performance of DBPM is mainly given by its digital signal processing algorithm. In order to find out a better solution for our new DBPM system, two algorithms have been designed and implemented on a commercial FPGA based DAQ module (ICS1554) to retrieve the turn-by-turn (TBT) data. The first algorithm is based on frequency mixing, and the second one on discrete Fourier transform (DFT). Laboratory tests show that the standard deviation of measured positions can be better than 1μm at 5 dBm with input signal stronger than 5 dBm for both algorithms. And on-line evaluation indicates that real beam motion can be observed correctly using either algorithm. | ||
| MOP176 | Design of Cavity Beam Quadrupole Moment Monitor at HLS | 417 |
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Funding: Work supported by the Natural Science Foundation of China, National “985 Project”, China Postdoctoral Science Foundation and “the Fundamental Research Funds for the Central Universities” Traditional ways to get beam emittance of linacs, such as multi-slits method, are destructive and then not able to be used in on-line beam diagnostics. To meet the requirements of XFEL equipments and improve the quality of electron beam, non-destructive on-line beam emittance measurement methods basing on getting the quadrupole moment of a beam non-destructively are then required. An advanced way to pick up beam information non-destructively with great precision is making use of eigenmodes of resonant cavities. High brightness injector at Hefei light source is used to study FEL based on photocathode RF electron gun. Cavity beam quadrupole moment monitor system designed for the high brightness injector consists of a square pill-box cavity used to pick up quadrupole signal, a cylindrical pill-box reference cavity, a waveguide coupling network that can suppress monopole and dipole signal, and a superheterodyne receiver used as front-end signal processing system. The whole system works at 5.712 GHz. Strength of quadupole magnets is adjust to construct a matrix which can be used to work out beam parameters. |
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| MOP177 | Design and Cold Test of Re-entrant Cavity BPM for HLS | 420 |
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Funding: Supported by Natural Science Foundation of China, National 985 Project, China Postdoctoral Science Foundation and the Fundamental Research Funds for the Central Universities An S-band cavity BPM is designed for a new injector in National Synchrotron Radiation Laboratory. A re-entrant position cavity is tuned to TM110 mode as position cavity. Theoretical resolution of the BPM is 31 nm. A prototype cavity BPM system is manufactured for cold test. Wire scanning method is used to calibrate the BPM and estimate the performance of the on-line BPM system. Cold test results showed that position resolution of prototype BPM is better than 3 μm. Cross-talk has been detected during the cold test. Racetrack cavity can be used to suppress cross-talk. Ignoring nonlinear effect, transformation matrix is a way to correct cross-talk. |
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| MOP179 | Numerical Study on Zone Plate Imaging | 423 |
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Funding: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education, Science and Technology (MEST) (grant No. R0A-2008-000-20013-0). The X-ray is focused by two zone plates in 1B2 beamline to image electron beam in PLS. From numerical study, we can determine the optical limit of resolution with the same specifications of Fresnel zone plates in 1B2 beamline. The width of Airy pattern and the outmost width of zone plates are turned out to be not good parameters to determine the resolution of the imaging system with a zone plate. The resolution of the entire imaging system 1B2 beamline will be revealed as 682 nm. |
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| MOP182 | Measurement of the Energy Dependence of Touschek Electron Counting Rate | 426 |
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| We have measured a dependence of the intra-beam scattering rate on the VEPP-4M beam energy and compared it with our theoretical estimates. Measurements have been performed at several energy points in a wide range: from 1.85 up to 4.0 GeV. | ||
| MOP183 | First Measurements of a New Beam Position Processor on Real Beam at Taiwan Light Source | 429 |
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| Libera Electron, Libera Brilliance and Libera Brilliance+ compose the electron beam position processors product family, which covers the needs of wide variety of the circular light source machines. The instruments deliver unprecedented possibilities for either building powerful single station solutions or architecting complex feedback systems. Compared to its predecessors (Libera Electron and Libera Briliance), the latest member of the family Libera Brilliance+ allows even more extensive machine physics studies to be conducted due to large data buffers and the new true turn-by-turn position calculation. It offers a large playground for custom- written applications with VirtexTM 5 and COM Express Basic module with Intel Atom N270 (x86) inside. First field tests of the new product were performed on real beam at Taiwan Light Source (TLS). The test setup, measurements and results are discussed in the paper. | ||
| MOP184 | Beam Instrumentation for the European Spallation Source | 432 |
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| The European Spallation Source, which will be built in the south of Sweden, is a neutron source based on a 5MW, 2.5GeV proton linac. The project is currently in the design update phase, and will deliver a Technical Design Report at the end of 2012. Construction is expected to begin in 2013. This paper discusses the initial beam diagnostics specifications, along with some possible instrument design options. | ||
| MOP185 | Development of Longitudinal Beam Profile Diagnostics within DITANET | 435 |
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Funding: Work supported by the EU under contract PITN-GA-2008-215080. The exact determination of the time structure of ever shorter bunches in accelerators and light sources such as for example the X-FEL, the ILC or CLIC is of high importance for the successful operation of these next-generation machines. It is also a key to the optimization of existing scientific infrastructures. The exact measurement of the time structure poses a number of challenges to the beam diagnostics system: The monitors should be non-destructive, easy to maintain and provide time resolutions down to the femtosecond regime. Several DITANET partners are active in this field. This contribution gives examples of the network’s research activities in this area with a focus on the LHC longitudinal density monitor, beam profile monitoring using electro-optics techniques and the exploitation of diffraction radiation for non-invasive diagnostics. |
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| MOP186 | Low Energy Beam Diagnostics Developments within DITANET | 438 |
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Funding: Work supported by the EU under contract PITN-GA-2008-215080. Low energetic ion beam are very attractive for a large number of fundamental physics experiments. The development of beam instrumentation for such beams poses many challenges due to the very low currents down to only a few thousands of particles per second and the resulting very low signal levels. Within DITANET, several institutions aim at pushing low energy, low intensity diagnostics beyond the present state-of-the-art. This contribution gives examples from the progress across the DITANET network in this research area. On behalf of the DITANET consortium. |
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| MOP189 | Progress in the Development of a Grazing-incidence Insertion Device X-ray Beam Position Monitor | 441 |
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Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Recently, a grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) was proposed for the intense x-ray beam from the future APS undulators [*]. By combining the function of limiting aperture with the XBPM, it increases the power-bearing capacity of the XBPM and, at the same time, eliminates the problem of relative alignment of the two critical components in the beamline. Furthermore, by imaging the hard x-ray fluorescence footprint on the collimator, the XBPM is immune to the soft x-ray background, and its accuracy is improved at larger gap settings. In addition to these advantages, the GRID-XBPM can also be implemented to measure center-of-mass of the x-ray fluorescence footprint when pinhole-camera-like optics are used for position readout*. This offers a solution for long-standing XBPM design issues for elliptical undulators, which have a donut-shaped power distribution. In this work, we report design progress for the GRID-XBPM for the high-power elliptically polarized undulator planned for the APS intermediate energy x-ray (IEX) beamline. Computer simulation of its performance and experimental tests from a scale model system will also be presented. * B.X. Yang, G. Decker, S. H. Lee, and P. Den Hartog, Beam Instrumentation Workshop, Santa Fe, 2010, to be published. |
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| MOP190 | Precision, Absolute Proton Beam Polarization Measurements at 200 MeV Beam | 444 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. A new polarimeter for absolute proton beam polarization measurements at 200 MeV to accuracy better than ±0.5% has been developed as a part of the RHIC polarized source upgrade. The polarimeter is based on the elastic proton-carbon scattering at 16.2 degree angle, where the analyzing power is close to 100% and was measured with high accuracy. The elastically and in-elastically scattered protons are clearly identified by the difference in the propagation through variable copper absorber and energy deposition of the protons in the detectors. The 16.2 degree elastic scattering polarimeter was used for calibration of a high rate inclusive 12 degree polarimeter for the on-line polarization tuning and monitoring. This technique can be used for accurate polarization measurements in energy range of at least 160-250 MeV. |
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| MOP191 | RHIC Spin Flipper Status and Simulation Studies | 447 |
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Funding: This work was supported by Department of Energy of U.S.A and RIKEN, Japan The commissioning of the RHIC spin flipper in the RHIC Blue ring during the RHIC polarized proton run in 2009 showed the detrimental effects of global vertical coherent betatron oscillation induced by the 2-AC dipole plus 4-DC dipole configuration *. Additional three AC dipoles were added to the RHIC spin flipper in the RHIC Blue ring during the summer of 2010 to eliminate the vertical coherent betatron oscillations outside the spin flipper [2]. This new design is scheduled to be commissioned during the RHIC polarized proton run in 2011. This paper presents the status of the system as well as latest simulation results. * M. Bai , T. Roser, C. Dawson, Y. Makdisi, W. Meng, F. Meot, P. Oddo, C. Pai, P. Pile, RHIC Spin Flipper New Design and Commissioning Plan, IPAC10 proceedings, IPAC 2010, Kyoto, Japan, 2010 |
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| MOP192 | NSLS-II BPM System Protection from Rogue Mode Coupling | 450 |
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Funding: Work supported by DOE contract DE-AC02-98CH10886 Rogue mode RF shielding has been successfully designed and implemented into the production multipole vacuum chambers. In order to avoid systematic errors in the NSLS-II BPM system we introduced frequency shift of HOM's by using RF metal shielding located in the antechamber slot of each multipole vacuum chamber. To satisfy the pumping requirement the face of the shielding has been perforated with roughly 50 percent transparency. It stays clear of synchrotron radiation in each chamber. |
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| MOP193 | Design of Visible Diagnostic Beamline for NSLS2 Storage Ring | 453 |
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| A visible synchrotron light monitor (SLM) beam line has been designed at the NSLS2 storage ring, using the bending magnet radiation. A retractable thin absorber will be placed in front of the first mirror to block the central x-rays. The first mirror will reflect the visible light through a vacuum window. The light is guided by three 6" diameter mirrors into the experiment hutch. In this paper, we will describe design work on various optical components in the beamline. | ||
| MOP194 | A Laser-Wire Beam-Energy and Beam-Profile Monitor at the BNL Linac | 456 |
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Funding: Work performed under Contract #DE-AC02-98CH10886 under the auspices of the US Department of Energy. In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H− beam by background gas. Electrons are stripped by the 1.7x10-7torr residual gas at a rate of ~2.4x10-8/cm. Since beam electrons have the same velocities as beam protons, the beam proton energy is deduced by multiplying the electron energy by mp/me=1836. A 183.6MeV H− beam produces 100keV electrons. In 2010 we installed an optics plates containing a laser and optics to add beam-profile measurement capability via photodetachment. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. The chamber in which the laser light passes through the ion beam is upstream of a dipole magnet which deflects the electrons into a biased retarding-grid (V<125kV) Faraday-cup detector. To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H− beam intercepted by the laser. The laser also gives us energy measurements on the 0.2mA polarized proton beam. |
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| MOP196 | A Modular Architecture for Accelerator Instrumentation | 459 |
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Funding: US Department of Energy With accelerated schedules and finite resources the development of a common open source platform for accelerator instrumentation is required. This effort has led to the development of a flexible architecture with clearly defined interfaces. The resulting platform is currently used to implement fast orbit feedback as well as the Beam Position monitors for NSLS-II. The design includes an embedded processor, digital signal processing resources and communications interfaces to controls, the timing system and other devices distributed throughout the accelerator complex. This new architecture promotes customization and design re-use and is presented as an Open Source Hardware development project. |
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| MOP197 | RHIC Stochastic Cooling Motion Control | 462 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Relativistic Heavy Ion Collider (RHIC) beams are subject to Intra-Beam Scattering (IBS) that causes an emittance growth in all three-phase space planes. The only way to increase integrated luminosity is to counteract IBS with cooling during RHIC stores. A stochastic cooling system [1] for this purpose has been developed, it includes moveable pick-ups and kickers in the collider that require precise motion control mechanics, drives and controllers. Since these moving parts can limit the beam path aperture, accuracy and reliability is important. Servo, stepper, and DC motors are used to provide actuation solutions for position control. The choice of motion stage, drive motor type, and controls are based on needs defined by the variety of mechanical specifications, the unique performance requirements, and the special needs required for remote operations in an accelerator environment. In this report we will describe the remote motion control related beam line hardware, position transducers, rack electronics, and software developed for the RHIC stochastic cooling pick-ups and kickers. |
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| MOP198 | BPM Inputs to Physics Applications at NSLS-II | 465 |
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| A new BPM (Beam Position Monitor) electronics is under development and in good progress at NSLS-II. This in-house BPM receiver with many new features is comparable to commercial solution. BPM data for fast orbit feedback (FOFB) is one of the most important physics applications. The procedure to use BPM for FOFB is introduced firstly. Then, different BPM data flows associated with different physics requirements and applications are discussed. And control implementation of BPM system for physics applications is presented. | ||
| MOP199 | NSLS-II X-ray Diagnostics Development | 468 |
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| NSLS-II storage ring will have less then 1nm*rad emittance. A concept of X-ray diagnostics beamline was developed in order to measure small sizes of radiation sources to deduct beam emittance. Diagnostics will include pinhole cameras and Compound Refractive Lens focusing optics. A novel optical layout was suggested in order to measure sources with large horizontal to vertical aspect ratio. | ||
| MOP202 | Simulations of the LHC High Luminosity Monitors at Beam Energies 3.5 TeV to 7.0 TeV | 471 |
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Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). We have constructed two pairs of fast ionization chambers (BRAN) for measurement and optimization of luminosity at IR1 and IR5 of the LHC. These devices are capable of monitoring the performance of the LHC at low luminosity 1028 cm-2s−1 during beam commissioning all the way up to the expected full luminosity of 1034 cm-2s−1 at 7.0 TeV. The ionization chambers measure the intensity of hadronic/electromagnetic showers produced by the forward neutral particles of LHC collisions. To predict and improve the understanding of the BRAN performance, we created a detailed FLUKA model of the detector and its surroundings. In this paper, we describe the model and the results of our simulations including the detector’s estimated response to pp collisions at beam energies of 3.5, 5.0, and 7.0 TeV per beam. In addition, these simulations show the sensitivity of the BRAN to the crossing angle of the two LHC beams. It is shown that the BRAN sensitivity to crossing angle is proportional to the measurement of crossing angle by the LHC beam position monitors. |
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| MOP203 | RHIC Spin Flipper AC Dipole Controller | 474 |
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Funding: Work supported by Brookhaven Science Associates, LLC under contract DE-AC02-98CH10886 with the U.S. Department of Energy and RIKEN, Japan. The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to control and dynamically tune the magnets. The current implementation and results will be presented. |
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| MOP205 | NSLS-II Injection Straight Diagnostics | 477 |
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| The ultra-bright light source being developed by the NSLS-II project will utilize top-up injection and fine tuning of the injection process is mandatory. In the paper we present the diagnostics installed on the injection straight. Its usage for commissioning and tuning of the injection cycle is also described. | ||
| MOP206 | Calibration and Performance of a Secondary Emission Chamber as a Beam Intensity Monitor | 480 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and with support of NASA. We report on a study of the behavior of a secondary emission chamber (SEC). We show the dependence of the SEC signal on the charge and velocity of the primary beam for beams of protons, and heavy ions including Helium, Neon, Chlorine and Iron. We fill the SEC with a selection of different gases including Hydrogen, Helium, Nitrogen, Argon, and air, studying the SEC response when it is acting as an ion chamber. We also investigate the behavior of the SEC at intermediate pressures between 10-8 torr and atmospheric pressure. |
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| MOP207 | Diamond X-ray Beam Position Monitors | 483 |
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Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grant DE-FG02-08ER41547. Modern synchrotrons are capable of significant per-pulse x-ray flux, and time resolved pulse-probe experiments have become feasible. These experiments provide unique demands on x-ray monitors, as the beam position, flux and arrival time all potentially need to be recorded for each x-ray pulse. Further, monitoring of “white” x-ray beam position and flux upstream of beamline optics is desirable as a diagnostic of the electron source. We report on a diamond quadrant monitors which provide beam monitoring for a variety of applications, for both white and monochromatic beams. These monitors have a position resolution of 20 nm for a stable beam, are linear in flux over at least 11 orders of magnitude, and can resolve beam motion shot-by-shot at repetition rates up to 6.5 MHz. |
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| MOP208 | Baseline Suppression Problems for High Precision Measurements Using Optical Beam Profile Monitors. | 486 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The use of fluorescent screens for beam profile monitors provides a simple and widely used way to obtain detailed two dimensional intensity maps. For high precision measurements many possible error contributions need to be considered that have to do with properties of the fluorescent screens and of the CCDs. Saturation effects, reflections within and outside the screen, non-linearities, radiation damage, etc are often mentioned. Here we concentrate on an error source less commonly described, namely erroneous baseline subtraction, which is particularly important when fitting projected images. We show computer simulations as well as measurement results having remarkable sensitivity of the fitted profile widths to even partial suppression of the profile baseline data, which often arises from large pixel-to-pixel variations at low intensity levels. Such inadvertent baseline data suppression is very easy to miss as it is usually not obvious when inspecting projected profiles. In this report we illustrate this effect and discuss possible algorithms to automate the detection of this problem as well as some possible corrective measures. |
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| MOP209 | Proposed Scattered Electron Detector System as One of the Beam Overlap Diagnostic Tools for the New RHIC Electron Lens | 489 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. An electron lens for head-on beam-beam compensation planned for RHIC requires precise overlap of the electron and proton beams which both can have down to 0.3 mm rms transverse radial widths along the 2m long interaction region. Here we describe a new diagnostic tool that is being considered to aid in the tuning and verification of this overlap. Some of ultra relativistic protons (100 or 250 GeV) colliding with low energy electrons (2 to 10 keV) will transfer sufficient transverse momentum to cause the electrons to spiral around the magnetic guiding field in a way that will make them detectable outside of the main solenoid. Time-of-flight of the halo electron signals will provide position-sensitive information along the overlap region. Scattering cross sections are calculated and counting rate estimates are presented as function of electron energy and detector position. |
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| MOP210 | Residual Gas Fluorescence Monitor at RHIC | 492 |
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Funding: This work was supported by U.S. Department of Energy under Contract No. DE-AC02-98CH10886. A residual gas fluorescence beam profile monitor at the relativistic heavy ion collider (RHIC) has successfully recorded vertical beam sizes of Au-ion beams from 3.85 to 100 GeV/n during the 2010 beam runs. Although the fluorescence cross section of Au-ion is sufficiently large, the low residual gas in a typical vacuum chamber of <10-9 torr produces necessary weak fluorescence photons. However, with adequate CCD exposure time, the vertical beam profiles are captured to provide an independent measurement of the RHIC beam size and emittance. This beam diagnostic technique, utilizing the Au-ion beam induced fluorescence from residual gas where hydrogen is still the dominant constituent in nearly all vacuum system, represents a step towards the realization of a truly noninvasive beam monitor for high-energy particle beams. |
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| MOP211 | NSLS-II RF Beam Position Monitor | 495 |
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Funding: Work supported by the U.S. DOE under contract No. DE-AC02-98CH10886. An internal R&D program has been undertaken at BNL to develop a sub-micron RF Beam Position Monitor (BPM) for the NSLS-II 3rd generation light source that is currently under construction. The BPM R&D program started in August 2009. Successful beam tests were conducted 15 months from the start of the program. The NSLS-II RF BPM has been designed to meet all requirements for the NSLS-II Injection system and Storage Ring. Housing of the RF BPMs in ±0.1C thermally controlled racks provide sub-micron stabilization without active correction. An active pilot-tone has been incorporated to aid long-term (8hr min) stabilization to 200nm RMS. |
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| MOP212 | Quadrupole Beam-Based Alignment in the RHIC Interaction Regions | 498 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Continued beam-based alignment (BBA) efforts have provided significant benefit to both heavy ion and polarized proton operations at RHIC. Recent studies demonstrated previously unknown systematic beam position monitor (BPM) offset errors and produced accurate measurements of individual BPM offsets in the experiment interaction regions. Here we describe the algorithm used to collect and analyze data during the 2010 and early 2011 RHIC runs and the results of these measurements. |
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| MOP214 | Methods for Quantitative Interpretation of Retarding Field Analyzer Data | 501 |
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Funding: US Department of Energy grant DE-FC02-08ER41538 US National Science Foundation grant PHY-0734867 Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring, and a great deal of data has been taken with them. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. Obtaining a quantitative understanding of RFA data requires use of cloud simulation programs, as well as a detailed model of the detector itself. In a drift region, the RFA can be modeled by postprocessing the output of a simulation code, and one can obtain best fit values for important simulation parameters with a chi-square minimization method. |
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| MOP215 | Digital Tune Tracker for CESR | 504 |
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Funding: Work supported by the DOE through DE-FC02-08ER41538 and the NSF through PHY-0734867. Numerous storage ring diagnostic operations require synchronous excitation of beam motion. An example is the lattice phase measurement, which involves synchronous detection of the driven betatron motion. In the CESR storage ring, the transverse tunes continuously vary by several times their natural width. Hence, synchronous beam excitation is impossible without active feedback control. The digital tune tracker consists of a direct digital frequency synthesizer which drives the beam through a transverse kicker, and is phase locked to the detected betatron signal from a quad button position detector. This ensures synchronous excitation, and by setting the correct locking phase, the excitation can be tuned to peak resonance. The fully digital signal detection allows a single bunch amid a long train to be synchronously driven, which allows lattice diagnostics to be performed which include collective effects. The collective effects potentially of interest in CESR include wakefield couplings within the train, and plasma effects such as ion trapping and electron cloud trapping. |
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| MOP218 | High Level Software for 4.8 Ghz LHC Schottky System | 507 |
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| A high level software package has been developed for a 4.8GHz Schottky system installed in the LHC at CERN. It has two main components. The first is a monitor application continuously running on a dedicated server as a daemon process to acquire the FFT traces, perform data analysis, publish results and do archiving. The second is a graphical user interface to display the FFT traces and various measurement results. It also allows the end user to change the settings for the front-end electronics such as the local oscillators, bunch selector, amplifier gains etc. Data analysis with curve fitting poses a big challenge due to the strong coherent signals that are often observed superimposed onto the Schottky sidebands. A method has been successfully created to remove the coherent spikes to enable curve fitting on the underlying signals, with the ultimate aim of providing reliable tune, momentum spread, chromaticity and emittance measurements for LHC beams with no external excitation. | ||
| MOP219 | Initial Beam-Profiling Tests with the NML Prototype Station at the Fermilab A0 Photoinjector | 510 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Beam-profile diagnostics are being developed for a superconducting (SC) radiofrequency (RF) Test Accelerator that is currently under construction at the New Muon Lab (NML) at Fermilab. The facility’s design goals include the replication of the pulse train proscribed for the International Linear Collider (ILC). An RF photoelectric gun based on the DESY design will generate the beam. In test-beam mode a low-power beam will be characterized with intercepting radiation converter screens: either a 100-micron thick YAG:Ce single crystal scintillator or a 1-micron thin Al optical transition radiation (OTR) foil. This prototype station was constructed by RadiaBeam Technologies under a contract with Fermilab. In both cases the screen surface was normal to the beam direction followed by a downstream 45-degree mirror that directed the radiation into the optical system. The optical system has better than 20 (10) micron rms spatial resolution when covering a vertical field of view of 18(5) mm. These initial tests were performed at the A0 Photoinjector at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for beam sizes of 45 to 250 microns. Example results will be presented. |
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| MOP220 | The Feasibility of Near-Field ODR Beam-Size Monitoring at 23 GeV at FACET | 513 |
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Funding: Work partially supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam- size sensitivity at the 10- to 20- μm σ level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year. |
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| MOP221 | An Application for Tunes and Coupling Evaluation From Turn-by-Turn Data at the Fermilab Booster | 516 |
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Funding: Work supported by Fermi Research Alliance, LLC under DE-AC02-07CH11359 with the U.S. DOE. A console application using the phasing of Turn-by-Turn signals from the different BPMs has been tested at the Fermilab Booster. This techinique allows the on-line detection of the beam tunes during the fast Booster ramp in conditions where other algorithms were unsuccessful. The application has been recently expanded to include the computation of the linear coupling coefficients. Algorithm and measurement results are presented. |
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| MOP222 | Operational Use of Ionization Profile Monitors in the Fermilab Main Injector | 519 |
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Funding: Operated by the Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the United States Department of Energy. Ionization profile monitors (IPMs) are used in the Fermilab Main Injector (MI) for injection lattice matching and to measure transverse emittance of the beam during acceleration. The IPMs provide a periodic, non-destructive means for emittance measurements where other techniques are not applicable. As Fermilab is refocusing its attention on the intensity frontier, non-intercepting diagnostics such as IPMs are expected to become even more important. This paper gives an overview of the operational use of IPMs for emittance measurements and injection lattice matching measurements at Fermilab, and summarizes the future plans. |
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| MOP224 | A Data Acquisition System for Longitudinal Beam Properties in a Rapid Cycling Synchrotron | 522 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A longitudinal beam properties, data acquisition system has been commissioned to operate in the Fermilab booster ring. This system captures real time information including beam synchronous phase, bunch length, and coupled bunch instability amplitudes as the beam is accelerated from 400MeV to 8GeV in 33ms. The system uses an off-the-shelf Tektronix oscilloscope running Labview software and a synchronous pulse generator. This paper describes the hardware configuration and the software configuration used to optimize the data processing rate. |
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| MOP225 | Initial Characterization of a Commercial Electron Gun for Profiling High Intensity Proton Beams in Project X | 525 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Measuring the profile of a high intensity proton beam is problematic in that traditional invasive techniques such as flying wires don't survive the encounter with the beam. One alternative is the use of an electron beam as a probe of the charge distribution in the proton beam as was done at the Spallation Neutron Source at ORNL. Here we present an initial characterization of the beam from a commercial electron gun from Kimball Physics, intended for use in the Fermilab Main Injector for Project X. |
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| MOP226 | Transverse Emittance and Phase Space Program Developed for Use at the Fermilab A0 Photoinjector | 528 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The Fermilab A0 Photoinjector is a 16MeV high intensity, high brightness electron Linac developed for advanced accelerator R&D. One of the key parameters for the electron beam is the transverse beam emittance. Here we report on a newly developed MATLAB based GUI program used for transverse emittance measurements using the multi-slit technique. This program combines the image acquisition and post-processing tools for determining the transverse phase space parameters with uncertainties. |
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| MOP228 | TE Wave Measurements of the Electron Cloud in a Dipole Magnetic Field | 531 |
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Funding: Work supported by the U.S. Department of Energy under Contract Nos. DE-AC02-05CH1123 and DE-FC02-08ER41538 and by the National Science Foundation Grant PHY-0734867. The TE wave propagation method has become a widely used technique for measuring electron cloud density in an accelerator beampipe. In most instances the wave very low power is not capable of affecting the low-energy electrons distribution. During experiments in the CESR Damping Ring Test Accelerator (Cesr-TA), we have observed a particular situation where a resonance between the wave and a dipole magnetic field produces a large modification in the electron cloud distribution that can be measured by other detectors. We believe this resonance is strongly dependent on the geometry of standing waves pattern that discontinuities in the beampipe generate. We present measurements in Cesr-TA, which describe the effect and are in support of our hypothesis. |
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| MOP229 | Electron Bunch Characterization using Temporal Electric-field Cross-correlation | 534 |
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Funding: Work supported by DARPA and by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 A new single-shot diagnostic is presented for mapping THz spatiotemporal waveforms with high temporal resolu- tion for use in diagnostics of electron bunch temporal pro- files. The THz waveform is encoded using electro-optic sampling onto either the phase or amplitude of a broadband chirped probe pulse, and is recovered using linear spectral interferometry with a temporally-short reader pulse. The technique was used to measure waveforms of coherent, ultrashort THz pulses emitted by electron bunches from a laser-plasma accelerator with sub-50 fs resolution. The presence of strong spatiotemporal coupling in the THz waveforms and of complex temporal electron bunch structure was determined. |
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| MOP230 | Precise Charge Measurement for Laser Plasma Accelerators | 537 |
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Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Cross-calibrations of charge diagnostics are conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). Employed diagnostics are a scintillating screen, activation based mea- surement, and integrating current transformer. The diagnostics agreed within ±8 %, showing that they can provide accurate charge measurements for LPAs provided they are used properly. |
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| MOP231 | Absolute Beam Flux Measurement at NDCX-I Using Gold-Melting-Calorimetry Technique | 540 |
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Funding: Supported by the U.S. Department of Energy under Contracts No. DE-AC02-05CH11231 and DE-AC52-07NA27344. We report on an alternative way to measure beam fluence at NDCX-I, which is necessary for numerical simulation and planning of warm-dense-matter (WDM) experiments. So far the NDCX-I beam fluence has been characterized using a fast Faraday cup, radiation from a scintillator and tungsten foil calorimeter techniques. The present beam intensity is sufficient to melt and partially evaporate a 150 nm thick gold foil. Thermal emission (function of temperature) of the gold foil in the visible spectrum was measured during beam irradiation. A distinct shelf in the thermal emission intensity was observed after 600 ns, indicating that the sample reached the melting temperature. Using known heat capacity and latent heat of melting, the beam flux fully determines the duration of the melting shelf and the moment it appears. Using this technique we estimate an average 260 kW/cm2 beam flux over 10μs, which is consistent with values provided by the other methods. |
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| MOP232 | LANSCE-R Wire-Scanner Analog Frontend Electronics (AFE) | 542 |
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Funding: U.S. Department of Energy. A new AFE is being developed for the new LANSCE-R wire-scanner systems. The new AFE is implemented in a National Instruments cRIO module installed a BiRa 4U BiRIO cRIO chassis specifically designed to accommodate the cRIO crate and all the wire-scanner interface, control and motor-drive electronics. A single AFE module provides interface to both X and Y wire sensors using true DC coupled transimpedance amplifiers providing collection of the wire charge signals, real-time wire integrity verification using the normal data-acquisition system, and wire bias of 0V to ±50V. The AFE system is designed to accommodate comparatively long macropulses (>1ms) with high PRF (>120Hz) without the need to provide timing signals. The basic AFE bandwidth is flat from true DC to 50kHz with a true first-order pole at 50kHz. Numeric integration in the cRIO FPGA provides real-time pulse-to-pulse numeric integration of the AFE signal to compute the total charge collected in each macropulse. This method of charge collection eliminates the need to provide synchronization signals to the wire-scanner AFE while providing the capability to accurately record the charge from long macropulses at high PRF. |
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| MOP233 | LANSCE-R Wire-scanner System | 545 |
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Funding: US Department of Energy The National Instruments cRIO platform is used for the new LANSCE-R wire-scanner systems. All wire-scanner electronics are integrated into a single BiRa BiRIO 4U cRIO chassis specifically designed for the cRIO crate and all interface electronics. The BiRIO chassis, actuator and LabVIEW VIs provide a complete wire-scanner system integrated with EPICS. The new wire-scanner chassis includes an 8-slot cRIO crate with Virtex-5 LX 110 FPGA and Power-PC real-time controller, the LANL-developed cRIO 2-axis wire-sensor analog interface module (AFE), NI9222 cRIO 4-channel 16-bit digitizer, cRIO resolver demodulator, cRIO event receiver, front-panel touch panel display, motor driver, and all necessary software, interface wiring, connectors and ancillary components. This wire-scanner system provides a complete, turn-key, 2-axis wire-scanner system including 2-channel low-noise sense-wire interface with variable DC wire bias and wire-integrity monitor, 16-bit signal digitizers, actuator motor drive and control, actuator position sensing, limit-switch interfaces, event receiver, LabVIEW and EPICS interface, and both remote operation and full stand-alone operation using the touch panel. |
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| MOP234 | Beam Position and Phase Monitors for the LANSCE Linac | 548 |
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Funding: This work is supported by the US Department of Energy under contract DE-AC52-06NA25396 New beam-position and phase monitors are under development for the linac at the Los Alamos Neutron Science Center. Transducers have been designed and are being fabricated. We are considering many options for the electronic instrumentation to process the signals and provide position and phase data with the necessary precision and flexibility to serve the various required functions. We’ll present the requirements of the system and the various options under consideration for instrumentation along with the advantages and shortcomings of these options. |
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| MOP235 | LANSCE Wire Scanning Diagnostics Device Prototype | 551 |
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| The Accelerator Operations & Technology Division at Los Alamos National Laboratory operates a linear particle accelerator which utilizes 110 wire scanning diagnostics devices to gain position and intensity information of the proton beam. In the upcoming LANSCE improvements, 51 of these wire scanners are to be replaced with a new design, up-to-date technology and off-the-shelf components. This document outlines the requirements for the mechanical design of the LANSCE wire scanner and presents the recently developed linac wire scanner prototype. Additionally, this document presents the design modifications that have been implemented into the fabrication and assembly of this first linac wire scanner prototype. Also, this document will present the design for the second and third wire scanner prototypes being developed. These last two prototypes belong to a different section of the particle accelerator and therefore have slightly different design specifications. Lastly, the paper concludes with a plan for future work on the wire scanner development. | ||
| MOP236 | First Test Results of the New LANSCE Wire Scanner | 554 |
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Funding: United States Department of Energy. The Beam Diagnostics and Instrumentation Team at Los Alamos National Laboratory’s LANSCE facility is presently developing a new and improved wire scanner diagnostics system controlled by National Instrument’s cRIO platform. This report describes the current state of development of the control system along with the results gathered from the latest actuator motion performance and accelerator beam data acquisition tests. |
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| MOP237 | Large Dynamic Range Beam Profile Measurements at SNS: Challenges and Achievements | 557 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. Beam profile diagnostics with large dynamic range is an important tool for understanding origin and evolution of the beam halo in accelerators. Typical dynamic range for conventional wire scanners has been in the range of 100. In high power machines like SNS fractional losses of 1 to 100 part per million is of concern and, therefore, higher dynamic range of profile measurements is desirable. Our near term goal was set to achieve a dynamic range of at least 10000 for all profile measurements in the SNS linac and transport lines. We will discuss present status of this program, challenges, and solutions. |
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| MOP238 | Laser Compton Proton Polarimetry Revisited | 560 |
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Compton polarimetry of polarized proton beams is more feasible now than it was in 1995*, when I first estimated the laser requirements of a polarimeter using the available laser technology. New methods of high energy photon generation make the technique of Compton proton polarimetry a viable option for polarized proton beams. Since the analyzing power of a Compton polarimeter increases with photon energy and the count rate of the polarimeter increases with the laser intensity, the new laser technologies available today imply the construction of a working device with reasonable effort. I estimate the device parameters necessary for a working Compton polarimeter at RHIC using several methods of high energy photon generation.
* Arnold Stillman, in Proceedings of the 1995 Particle Accelerator Conference, 1995, p.2560 |
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| MOP239 | Commercially Available Transverse Profile Monitors, the IBIS | 562 |
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| With ever decreasing budgets, shorter delivery schedules and increased performance requirements for pending and future facilities, the need for cost effective yet high quality profile monitors is paramount to future advancement in the accelerator field. While individual facilities are capable of designing and fabricating these often custom devices, this is not always the most efficient or economical route. In response to the lack of commercially available profile monitors, RadiaBeam Technologies has been developing its line of Integrated Beam Imaging System (IBIS) over the past several years. Here, we report on these commercially available profile monitors. | ||
| MOP241 | Beam Diagnostics for FACET | 565 |
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Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515. FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration beginning in summer 2011. The nominal FACET parameters are 23 GeV, 3 nC electron bunches compressed to ~20 μm long and focussed to ~10 μm wide. Characterization of the beam- plasma interaction requires complete knowledge of the incoming beam parameters on a pulse-to- pulse basis. FACET diagnostics include Beam Position Monitors, Toroidal current monitors, X-ray and Cerenkov based energy spectrometers, optical transition radiation (OTR) profile monitors and coherent transition radiation (CTR) bunch length measurement systems. The compliment of beam diagnostics and their expected performance are reviewed. |
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| MOP242 | Evaluation of Temporal Diagnostic Techniques for Two-bunch FACET Beam | 568 |
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Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which will incorporate a unique two-bunch beam for plasma wakefield acceleration experiments. The results of these experiments will depend strongly on the the inter-bunch spacing as well as the longitudinal profiles of the two bunches. A reliable, single-shot, high resolution measurement of the beam’s temporal profile is necessary to fully quantify the physical mechanisms underlying the beam driven plasma wakefield acceleration. In this study we show that a transverse deflecting cavity is the diagnostic which best meets our criteria. |
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| MOP243 | Design of a Compact, High-Resolution Analyzer for Longitudinal Energy Studies in the University of Maryland Electron Ring | 571 |
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Funding: Work supported by US Dept. of Energy Offices of High Energy Physics and Fusion Energy Sciences, the Dept. of Defense Office of Naval Research, and the Joint Technology Office. Retarding-potential energy analyzers have long been used for energy spread measurements in low-energy beams. In addition to energy spread and energy profile measurements, a high-resolution analyzer can be used to reconstruct the longitudinal phase space. This is useful for our experimental studies of longitudinal physics topics, such as dispersion, space charge waves, and longitudinal focusing. A previous energy analyzer designed at the University of Maryland demonstrated high-resolution measurements of a 5 keV electron beam.* Motivated by the need to characterize the 10 keV electron beam of the University of Maryland Electron Ring, we have improved on the design of the earlier analyzer, increasing its high voltage breakdown threshold and vacuum performance. Results of high-voltage testing and particle optics simulations of the new design are presented. *Y. Cui, Y. Zou, et al., "Design and Operation of a Retarding Field Energy Analyzer with Variable Focusing for Space-Charge Dominated Electron Beams," Review of Scientific Instruments 75(8), 2736 (2004). |
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| MOP247 | Quick Setup of Unit Test For Accelerator Controls System | 574 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Testing a single hardware unit of an accelerator control system often requires the setup of a graphical user interface. Developing a dedicated application for a specific hardware unit test could be time consuming and the application may become obsolete after the unit tests. This paper documents a methodology for quick design and setup of an interface focused on performing unit tests of accelerator equipment with minimum programming work. The method has three components. The first is a generic accelerator device object (ADO) manager which can be used to setup, store, and log testing controls parameters for any unit testing system. The second involves the design of a TAPE (Tool for Automated Procedure Execution) sequence file that specifies and implements all testing and control logic. The third is the design of a PET (parameter editing tool) page that provides the unit tester with all the necessary control parameters required for testing. This approach has been used for testing the horizontal plane of the Stochastic Cooling Motion Control System at RHIC. |
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| MOP248 | Automating Power Supply Checkout | 577 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Power Supply checkout is a necessary, pre-beam, time-critical function. At odds are the desire to decrease the amount of time to perform the checkout while at the same time maximizing the number and types of checks that can be performed and analyzing the results quickly (in case any problems exist that must be addressed). Controls and Power Supply Group personnel have worked together to develop tools to accomplish these goals. Power Supply checkouts are now accomplished in a time-frame of hours rather than days, reducing the number of person-hours needed to accomplish the checkout and making the system available more quickly for beam development. |
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| MOP249 | Improved Alarm Tracking for Better Accountability | 579 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. An alarm system is a vital component of any accelerator, as it provides a warning that some element of the system is not functioning properly. The severity and age of the alarm may sometimes signify whether urgent or deferred attention is required. For example, older alarms may inadvertently be given a lower priority if an assumption is made that someone else is already investigating it, whereas those that are more current may indicate the need for an immediate response. The alarm history also provides valuable information regarding the functionality of the overall system, thus careful tracking of these data is likely to improve response time and remove uncertainty about the current status. Since one goal of every alarm display is to be free of alarms, a clear and concise presentation of an alarm along with useful historic annotations can help the end user address the warning more quickly. By defining a discrete set of very specific alarm states and by utilizing database resources to maintain a complete and easily accessible alarm history, we anticipate a decrease in down time due to more efficient operator response and management of alarms. |
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| MOP250 | NSLS-II High Level Application Infrastructure and Client API Design | 582 |
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Funding: Work performed under auspices of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 with Brookhaven Science Associates, LLC. The beam commissioning software framework of NSLS-II project adopts a client/server based architecture to replace the more traditional monolithic high level application approach. It is an open structure platform, and we try to provide a narrow API set for client application. With this narrow API, existing applications developed in different language under different architecture could be ported to our platform with small modification. This paper describes a detailed client API design, and latest progress. |
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| MOP252 | Server Development for NSLS-II Physics Applications and Performance Analysis | 585 |
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Funding: Work performed under auspices of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 with Brookhaven Science Associates, LLC. The beam commissioning software framework of NSLS-II project adopts a client/server based architecture to replace the more traditional monolithic high level application approach. The server development is ongoing, and adopts a sourceforge open project so-called epics-pvdata, which consists of pvData, pvAccess, pvEngine, and pvService. Some services have being demonstrated as one service under pvService module such as itemFinder service, gather service, and lattice manager, and each service runs as one standalone server using pvData to store in-memory transient data, pvService to transfer data over network, and pvEngine as service engine. This paper describes a detailed development, latest progress, and performance analysis. |
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| MOP256 | Upgrading the Data Acquisition and Control System of the LANSCE LINAC | 588 |
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Funding: This work has benefited from the use of the LANSCE at LANL. This facility is funded by the US DOE and operated by LANS for NSSA under Contract DE-AC52-06NA25396. Los Alamos National Laboratory LANL is in the process of upgrading the control system for the Los Alamos Neutron Science Center (LANSCE) linear accelerator. The 38 year-old data acquisition and control equipment is being replaced with COTS hardware. An overview of the current system requirements and how the National Instruments cRIO system meets these requirements will be given, as well as an update on the installation and operation of a prototype system in the LANSCE LINAC. LANL Release Number: LA-UR 10-06605 |
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| MOP257 | High Power RF Distribution and Control for Multi-Cavity Cryomodule Testing | 591 |
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Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS has been successfully operating 81 superconducting six-cell cavities in 23 cryomodules in its linac to achieve the goals in beam power and energy. For near-term production of spare cryomodules and the upcoming power upgrade project that will need 36 additional cavities in 9 cryomodules, high RF power testing and qualification of the cavities is required in the RF test facility. Simultaneously powering all the cavities in a cryomodule is considered desirable for robust conditioning and studying of cavity field emission since certain cavities exhibit field emissions that could be mutually coupled. A four-way variable output power waveguide splitting system is being prepared for testing cryomodules with up to four cavities. The splitting system is fed by an 805 MHz, 5 MW peak power pulsed klystron. The power output at each arm can be adjusted in both amplitude and phase to wide ranges of values using two mechanical waveguide phase shifters that form a vector modulator. The system control is implemented in the EPICS environment similar to the main accelerator controls. The work performed on the design, integration, operation, and test of the system are presented. |
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| MOP261 | The CEBAF Element Database | 594 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. With inauguration of the CEBAF Element Database(CED) in Fall 2010, Jefferson Lab computer scientists have taken a first step toward the eventual goal of a model-driven accelerator. Once fully populated, the database will be the primary repository of information used for everything from generating lattice decks to booting iocs to building controls screens. A requirement influencing the CED design is that it provide access to not only present, but also future, and eventually past, configurations of the accelerator. To accomplish this, an introspective database schema was designed that allows new elements, types, and properties to be defined on-the-fly with no changes to table structure. Used in conjunction with Oracle Workspace Manager, it allows users to query data from any time in the database history with the same tools used to query the present configuration. Users can also check-out workspaces to use as staging areas for upcoming machine configurations. All Access to the CED is through a well-documented API that is translated automatically from original C++ into native libraries for script languages such as perl, php, and TCL making access to the CED easy and ubiquitous. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. |
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| MOP263 | Fast Orbit Feedback System for the LNLS Storage Ring | 597 |
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| The Brazilian Synchrotron Light Laboratory (LNLS) is based on a 1.37 GeV storage ring, previously operated by means of a Slow Orbit Feedback System at a maximum rate of 1 correction every 3 seconds. Since photon flux stability is a key issue for light source users, a faster control system was envisaged to provide better beam stability. This work presents an overview of the hardware architecture and the preliminary results achieved with the implementation of a Fast Orbit Feedback System using commercial hardware. BPM signals are acquired in a distributed topology and sent through a deterministic EtherCAT network to a PXI controller, responsible for applying the SVD-based correction matrix multiplication and communicating with the accelerator control system; the calculated current setpoints are sent to the correctors’ power supplies through a second EtherCAT network. FPGA-based acquisition and actuation chassis perform pre-filtering and control on the digitized input and output signals, respectively. | ||
| MOP265 | The FONT5 Prototype ILC Intra-train Feedback System at ATF2 | 600 |
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| We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction in y and y' to the train of bunches extracted from the ATF damping ring. We describe the feedback performance in both single and coupled-loop modes and the optimisation of the loop gains. | ||
| MOP266 | Stripline Kicker Design for NSLS2 Storage Ring | 603 |
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| In the NSLS2 storage ring, there are four stripline kickers/pickups. Two long striplines with electrode length of 30cm will be used as bunch-by-bunch transverse feedback actuators. Two short stripline kickers/pickups with 15cm length will mainly used for tune measurement excitation or signal pickup for the beam stability monitor. High shunt impedance of the long stripline kickers is demanded to produce 200μs damping time. Meanwhile the beam impedance should be minimized. The design work for these two types of stripline is discussed in this paper. | ||
| MOP267 | Fast BPM Data Distribution for Global Orbit Feedback Using Commercial Gigabit Ethernet Technology | 606 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In order to correct beam perturbations in RHIC around 10Hz, a new fast data distribution network was required to deliver BPM position data at rates several orders of magnitude above the capability of the existing system. The urgency of the project limited the amount of custom hardware that could be developed, which dictated the use of as much commercially available equipment as possible. The selected architecture uses a custom hardware interface to the existing RHIC BPM electronics together with commercially available Gigabit Ethernet switches to distribute position data to devices located around the collider ring. Using the minimum Ethernet packet size and a field programmable gate array (FPGA) based state machine logic instead of a software based driver, real-time and deterministic data delivery is possible using Ethernet. The method of adapting this protocol for low latency data delivery, bench testing of Ethernet hardware, and the logic to construct Ethernet packets using FPGA hardware will be discussed. |
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| MOP268 | RHIC 10 Hz Global Orbit Feedback System | 609 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including reinforcing the magnet base support assembly, a mechanical servo feedback system, and a local beam feedback system at each of the two experimental areas. However, implementation of the mechanical solutions would be expensive, and the local feedback system was insufficient since perturbation amplitudes outside the experimental areas were still problematic. A global 10 Hz orbit feedback system is currently under development at RHIC consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two counter-rotating rings. A subset of the system consisting of 8 BPMs and 4 corrector magnets in each ring was installed and successfully tested during the RHIC 2010 run; and the complete system is being installed for the 2011 run. A description of the overall system architecture and results with beam will be discussed. |
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| MOP269 | Design of Longitudinal Feedback Kicker for HLS Storage Ring | 612 |
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| Hefei Light Source (HLS) is a dedicated synchrotron radiation research facility. It is now undergoing a major upgrade. To obtain a better performance of the light source, a longitudinal feedback system will be developed as part of the upgrade project to cure the coupled bunch mode instabilities. In this work, we present a design of the LFB kicker, a waveguide overloaded cavity with two input and two output ports. The cavity design specifications include a central frequency of 969 MHz (4.75 RF frequency), a bandwidth of more than 100 MHz, and a high shunt impedance of 1200 Ω. A study is carried out to find the dependence of the cavity performance on a few critical geometric parameters of the cavity. Since the shape of the vacuum chamber of the HLS storage ring is octagon, a transition from a circular vacuum chamber to an octagon one is built into the end pieces of the cavity to minimize the total cavity length. To lower the required amplifier power, the structure is optimized to obtain a high shunt impedance. The higher order modes of the kicker cavity are also considered during the design. | ||
| MOP272 | Radiation Dose Level in the SSRF during Normal Operation | 615 |
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| Shanghai Synchrotron Radiation Facility (SSRF) has been commissioned since December 2007, and has been formally operated since May 2009. In order to ensure the radiation safety for staff members and publics, the radiation levels of the workplace, the environment and the staff are monitored through a real-time network of gamma and neutron monitors as well as through TLD passive dosimeters. This paper reports the results of the radiation monitoring. From these results, we found that the annual dose equivalents were good to meet the management values of SSRF. | ||
| MOP273 | Calibration and Simulation of the LCLS Undulator Beam Loss Monitors using APS Accelerators | 618 |
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Funding: U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357 Electrons scattered by alumina ceramic transverse beam profile monitors inserted in the Advanced Photon Source (APS) booster-to-storage ring (BTS) transfer line are used to generate C ̆erenkov light for calibration of beam loss monitors (BLMs) installed in the Linac Coherent Light Source (LCLS) undulator beamline. In addition, gas bremsstrahlung (GB) photons generated by 7-GeV electrons in the APS sector 35 storage ring straight section are used to create pair-production electrons for measurement and calibration purposes. Both cases are modeled with the particle-matter interaction program MARS. The realized tuning fork geometry of the BLM exhibits regions of greater sensitivity in the radiator. Transverse GB beam scans have provided uniformity and sensitivity data throughout the volume of the radiator. Comparisons between predicted and measured signal strengths and thermoluminescent dosimeter readings are given and shown to be in reasonable agreement. |
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| MOP274 | Beam Loss Monitors for NSLS-II Storage Ring | 621 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 The shielding for the NSLS-II storage ring will provide adequate protection for the full injected beam losses in two periods of the ring around the injection point, but the remainder of the ring is shielded for lower losses of <10% top-off injection beam current. This will require a system to insure that beam losses do not exceed these levels for a period of time that could cause excessive radiation exposure outside the shield walls. This beam Loss Control and Monitoring system will have beam loss monitors that will measure where the beam charge is lost around the ring, to warn operators if losses approach the design limits. In order to measure the charge loss quantitatively, we propose measuring the electron component of the shower as beam electrons hit the vacuum chamber wall. This will be done using the Cerenkov light as charged particles transit an ultra-pure fused silica rod placed close to the inner edge of the VC. The length of rod will collect the light from many charged particles of the spread out shower resulting from the small glancing angle of the lost beam particles to the VC wall. The design and measurements results of the prototype Cerenkov BLM will be presented. |
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| MOP275 | Beam Loss Control for the NSLS-II Storage Ring | 624 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 The shielding design for the NSLS-II storage ring is designed for the full injected beam losses in two periods of the ring around the injection point, but for the remainder of the ring its shielded for <10% top-off injection beam. This will require a system to insure that beam losses do not exceed these levels for time sufficient to cause excessive radiation exposure outside the shield walls. This beam Loss Control and Monitoring (LCM) system will control the beam losses to the more heavily shielded injection region while monitoring the losses outside this region. To achieve this scrapers are installed in the injection region to intercept beam particles that might be lost outside this region. The scrapers will be thin (< 1Xrad) that will allow low energy electrons to penetrate and the subsequent dipole will separate them from the stored beam. These thin scrapers will reduce the radiation from the scraper compared to thicker scrapers. The dipole will provide significant local shielding for particles that hit inside the gap and a source for the loss monitor system that will measure the amount of beam lost in the injection region. * Beam Loss Monitors for NSLS-II Storage Ring, S.L. Kramer & P. Cameron, these proceedings |
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| MOP276 | Applying Cascaded Parameter Scan to Study Top-off Safety in NSLS-II Storage Ring | 627 |
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Funding: Work supported by U.S. DOE, Contract No. DE-AC02-98CH10886 In this paper we introduce a new algorithm, the cascaded parameter scan method, to efficiently carry out the scan over magnet parameters in the safety analysis for the NSLS-II top-off injection. In top-off safety analysis, one must track particles populating phase space through a beamline containing magnets and apertures and clearly demonstrate that for all possible magnet settings and errors, all particles are lost on scrapers within the properly shielded region. In the usual approach, the number of tracking runs increases exponentially with the number of magnet settings. In the cascaded parameter scan method, the number of tracking runs only increases linearly. This reduction of exponential to linear dependence on the number of setpoints, greatly reduces the required computation time and allows one to more densely populate phase space and to increase the number of setpoints scanned for each magnet. An example of applying this approach to analyze an NSLS-II beamline, the damping wiggler beamline, is also given. |
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| MOP277 | The Machine Protection System for the R&D Energy Recovery LINAC | 630 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Machine Protection System (MPS) is a device-safety system that is designed to prevent damage to hardware by generating interlocks, based upon the state of input signals generated by selected sub-systems. It protects all the key machinery in the R&D Project called the Energy Recovery LINAC (ERL) against the high beam current. The MPS is capable of responding to a fault with an interlock signal within several microseconds. The ERL MPS is based on a National Instruments CompactRIO platform, and is programmed by utilizing National Instruments' development environment for a visual programming language. The system also transfers data (interlock status, time of fault, etc.) to the main server. Transferred data is integrated into the pre-existing software architecture which is accessible by the operators. This paper will provide an overview of the hardware used, its configuration and operation, as well as the software written both on the device and the server side. |
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| MOP278 | Ultra Precision Timing System for the Laser Megajoule | 633 |
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| This article presents a specific timing system designed for the Laser Megajoule project. This accuracy timing system has to deliver 64 electrical trigger signals with a very low jitter (< 5 ps rms) in order to synchronize the 240 laser pulses on the same target, in single shot mode and over 100 meter distances. After a dimensioning phase leading to the architecture of the system and the selection of components, a prototype was developed providing 8 electrical trigger signals. We expose the architecture and the excellent results achieved on this prototype regarding jitter, thermal drift and delay linearity. | ||
| MOP279 | Synchronize Lasers to LCLS e- Beam | 636 |
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| Fiber based synchronization system is used in LCLS to synchronize the laser for pump probe experiment to average electron beam arrival time. Electron bunch arrival time measured by phase cavity is one of the best measurement for FEL X pulse until now. The average bunch arrival time is transmitted through electronic length stabilized fiber link to AMO and other experiment hall. The laser oscillator is phase locked to this reference signal to maintain low jitter and drift between pump and probe. The in loop error shows the jitter is less then 100 fs and meets the experiment requirement. | ||
| MOP281 | ADC Clocking Formats and Matching Networks | 639 |
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| Clocking an ADC is the most critical point when resolution is a major concern. Any fluctuations on the input clock performance correlates to jitter. The many different formats used to clock ADCs on the market makes choosing the appropriate one no easy task. LVDS, PECL, LVPECL, CMOS and CML are just some of the different types. With each type a certain matching network will be required. This paper will discuss the advantages of each format as well as its associated matching network. | ||
| MOP282 | A Deterministic, Gigabit Serial Timing, Synchronization and Data Link for the RHIC LLRF | 642 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. A critical capability of the new RHIC low level rf system is the ability to synchronize signals across multiple locations. The Update Link provides this functionality. The Update Link is a deterministic serial data link based on the Xilinx Aurora protocol that is broadcast over fiber optic cable at 1 gigabit per second. The link provides timing events and data packets as well as time stamp information for synchronizing diagnostic data from multiple sources. |
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| MOP283 | A Hardware Overview of the RHIC LLRF Platform | 645 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The RHIC LLRF platform is a flexible, modular system designed around a carrier board with six XMC daughter sites. The carrier board features a Xilinx FPGA with an embedded, hard core Power PC that is remotely reconfigurable. It serves as a front end computer (FEC) that interfaces with the RHIC control system. The carrier provides high speed serial data paths to each daughter site and between daughter sites as well as four generic external fiber optic links. It also distributes low noise clocks and serial data links to all daughter sites and monitors temperature, voltage and current. To date, two XMC cards have been designed: a four channel high speed ADC and a four channel high speed DAC. |
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| MOP284 | A High Performance DAC / DDS Daughter Module for the RHIC LLRF Platform | 648 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The RHIC LLRF upgrade is a flexible, modular system. Output signals are generated by a custom designed XMC card with 4 high speed digital to analog converters interfaced to a high performance field programmable gate array (FPGA). This paper discusses the hardware details of the XMC DAC board as well as the implementation of a low noise rf synthesizer with digital IQ modulation. This synthesizer also provides injection phase cogging and frequency hop rebucketing capabilities. |
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| MOP285 | Synchronization and Jitter Studies of a Titanium-sapphire Laser at the A0 Photoinjector | 651 |
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Funding: Supported by Fermi Research Alliance, LLC under U.S. Dept. of Energy Contract No. DE-AC02-07CH11359, and Northern Illinois Univ. under US Dept. of Defense DURIP program Contract N00014-08-1-1064. A new titanium-sapphire laser has recently been installed at the A0 photoinjector for use in ongoing beam generation and ultra-fast beam diagnostics experiments. Where the system is used as the photoinjector drive laser, jitter and drift in the laser pulse time of arrival with respect to the low-level RF master oscillator and other beam components are known to degrade beam performance. These same fluctuations can also impact the temporal resolution of laser-based diagnostics. To resolve this, we present the results of some beam-based timing experiments as well as current progress on a synchronization feedback loop being adapted to the new laser system. |
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| MOP287 | Femtosecond RF Timing in Low Charge Photoinjectors | 654 |
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Funding: Office of Naval Research Grant No. N000140711174 and US Department of Energy Grant No. DE-FG02-92ER40693. Photoelectron gun rf parameter mapping is explored as an extension to electro-optic sampling to monitor bunch vs. laser relative time-of-arrival. The method is evaluated for timestamping sub-picocoulomb femtosecond laser-pumped dynamics in graphite via electron diffraction where the required timing resolution is < 10 fs. *AL Cavalieri, et al. Phys. Rev. Lett. 94, 114801 (2005) **A Azima, et al. Appl. Phys. Lett. 94, 144102 (2009) ***CM Scoby, et al. PRST-AB 13, 022801 (2010) ****KJ Kim, Rev. Nucl. Inst. Meth. A 275, 2 (1989) |
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| MOP288 | Progress Report on Development of the RING Cavity for Laser-based Charge Stripping of Hydrogen Ions | 657 |
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| Charge stripping of hydrogen ions is the first stage of any high intensity proton accelerator. To achieve higher-charge proton sources, the stripping efficiency must be improved, especially in the context of the Spallation Neutron Source at Oak Ridge National Laboratory. A method based on laser-ion interaction has a great potential for increasing efficiency. The approach of this proposed project is to design a laser cavity based on the Recirculation Injection by Nonlinear Gating (RING) technique. This paper reports on the progress of the development of the RING cavity. | ||
| MOP290 | Self Excited Operation for a 1.3 GHz 5-cell Superconducting Cavity | 660 |
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| Self-Excited operation of a resonant system does not require any external frequency tracking as the frequency is determined by the phase lag of the self-excited loop, it is therefore particularly useful for testing high Q RF cavities that do not have an automatic tuning mechanism. Self-exited operation has long been shown to work with single-cell cavities. We have recently demonstrated that it is also possible for multi-cell cavities, where multiple resonant modes are present. The Cornell 1.3 GHz 5-cell superconducting cavities was operated using Self-Excited operation and we were able to lock to the accelerating (pi) mode, despite the presence of neighbouring modes that are less than 10 MHz away. By means of the loops phase advance, we were able to select which mode was excited. | ||
| MOP292 | Universal FMC-Compliant Module for xTCA Systems | 663 |
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Funding: The research leading to these results has received funding from Polish National Science Council Grant 642/N-TESLAXFEL/09/2010/0. The Advanced Telecommunications Computing Architecture (ATCA), MicroTCA (uTCA) and Advanced Mezzanine Card (AMC) standards, known as xTCA, provide unique features desired by various control systems of particle accelerators. The standards provide availability and operability as high as 99.999 %. A significant number of additional features must be implemented to take a full advantage of xTCA standards and gain the required availability. On the other hand, many control systems require various data acquisition and control modules with different number of input analogue and digital inputs or outputs as defined by their respective system specifications. The paper presents an universal base module, designed according to the AMC standard with an FPGA Mezzanine Card connector, that can be used for fast development of input-output subsystems. The module consists of two submodules. The digital part is designed according to the AMC standard while the main input-output functionality is realized by the FPGA Mezzanine Card part. The FMC submodule provides the functionality required by the specification of the LLRF system. |
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| MOP293 | Performance of Analog Signal Distribution in the ATCA Based LLRF System | 666 |
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| The Low Level Radio Frequency System (LLRF) for the European X-FEL must provide exceptional stability of the accelerating RF field in the accelerating cavities. The regulation requirements of 0.01% and 0.01 degrees in amplitude and phase respectively must be achieved at a frequency of 1.3 GHz while keeping low drifts (during RF pulse). The quality of analog signal processing and distribution plays a crucial role in achieving these goals. The RF signals are connected to the Rear Transition Module (RTM), downconverted there into intermediate frequency (IF) signals and finally sampled at AMC-ADC module. The high quality of the signals (SNR, low crosstalk) must be assured across all the way. The paper presents the results of development of ATCA based LLRF system for XFEL. The special attention is paid to RTM module with downconverters and carrier board conducting analog signals to the AMC-ADC and the AMC Vector Modulator module in the presence of digital processing components (FPGA, DSP). | ||
| MOP295 | The Low-level Radio Frequency System for the Superconducting Cavities of National Synchrotron Light Source II | 669 |
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Funding: US DOE A digital low-level radio frequency (LLRF) field controller has been developed for the storage ring of The National Synchrotron Light Source-II (NSLS-II). The primary performance goal for the LLRF is to support the required RF operation of the superconducting cavities with a beam current of 500mA and a 0.14 degree or better RF phase stability. The digital field controller is FPGA-based, in a standard format 19”/1-U chassis. It has an option of high-level control support with MATLAB running on a local host computer through a USB2.0 port. The field controller has been field tested with the high-power superconducting RF (SRF) at Canadian light Source, and successfully stored a high beam current of 250 mA. The test results show that required specifications for the cavity RF field stability are met. This digital field controller is also currently being used as a development platform for other functional modules in the NSLS-II RF systems. |
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| MOP296 | Embedded System Architecture and Capabilities of the RHIC LLRF Platform | 672 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. A high performance FPGA based platform has been developed for the RHIC Low Level RF system upgrade, and is now replacing our aging VME based systems. This new platform employs a sophisticated embedded architecture to implement its core functionality. This architecture provides a control system interface, manages remote access to all configuration parameters and diagnostic data, supports communication between all system components, enables real time application specific processing, monitors system health, etc. This paper will describe the embedded architecture and its capabilities, with emphasis on its application at RHIC. |
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| MOP297 | A Bunch to Bucket Phase Detector for the RHIC LLRF Upgrade Platform | 675 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy As part of the overall development effort for the RHIC LLRF Upgrade Platform, a 4 channel ADC daughter module was developed to provide high speed, wide dynamic range digitizing and processing of signals from DC to several hundred megahertz. The first operational use of this card was to implement the bunch to bucket phase detector for the RHIC LLRF beam control feedback loops. This paper will describe the design and performance features of this daughter module as a bunch to bucket phase detector, and also provide an overview of its place within the overall LLRF platform architecture as a high performance digitizer and signal processing module suitable to a variety of applications. |
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| MOP298 | Commisioning Results from the Recently Upgraded RHIC LLRF System | 678 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy During RHIC Run 10, the first phase of the LLRF Upgrade was successfully completed. This involved replacing the aging VME based system with a modern digital system based on the recently developed RHIC LLRF Upgrade Platform, and commissioning the system as part of the normal RHIC start up process. At the start of Run 11, the second phase of the upgrade is underway, involving a significant expansion of both hardware and functionality. This paper will review the commissioning effort and provide examples of improvements in system performance, flexibility and scalability afforded by the new platform. |
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| MOP299 | Commissioning and Performance of the BNL EBIS LLRF System | 681 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Electron Beam Ion Source (EBIS) LLRF system utilizes the RHIC LLRF upgrade platform to achieve the required functionality and flexibility. The LLRF system provides drive to the EBIS high-level RF system, employs IQ feedback to provide required amplitude and phase stability, and implements a cavity resonance control scheme. The embedded system provides the interface to the existing Controls System, making remote system control and diagnostic possible. The flexibility of the system allows us to reuse VHDL codes, develop new functionalities, improve current designs, and implement new features with relative ease. In this paper, we will discuss the commissioning process, issues encountered, and performance of the system. |
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| MOP300 | The Spallation Neutron Source Eight-Channel Pulsed Power Meter | 684 |
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| The Spallation Neutron Source (SNS) Low Level Radio Frequency (LLRF) Control System currently utilizes the High-Power Protection Module (HPM) to monitor RF power levels, arc faults, and associated signals for the protection of the RF systems and accelerating cavities. The HPM is limited to seven RF channels for monitoring signals which in some instances leaves some signals of interest unmonitored. In addition, the HPM does not support monitoring of RF frequencies below 100 MHz which makes it unusable for our Ring and Ion Source systems that operate at 1 and 2 MHz respectively. To alleviate this problem, we have developed a microprocessor based eight channel pulsed RF power meter that allows us to monitor additional channels between the frequency range of 1 MHz to 2.5 GHz. This meter has been field tested in several locations with good results and plans are in place for a wider deployment. | ||
| MOP304 | Development of an X-Ray Beam Size Monitor with Single Pass Measurement Capability for CesrTA | 687 |
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| The CESR Test Accelerator (CesrTA) program targets the study of beam physics issues relevant to linear collider damping rings. This endeavor requires new instrumentation to study the beam dynamics along trains of ultra low emittance bunches. A key element of the program has been the development of an x-ray beam size monitor capable of collecting single pass measurements of individual bunches in a train over thousands of turns. This instrument utilizes custom, high bandwidth amplifiers and digitization hardware to collect signals from a linear InGaAs diode array. The digitizer is synchronized with the CESR timing system and is capable of recording beam size measurements for bunches spaced by as little as 4ns. The x-ray source is a bending magnet with Ec=0.6 keV during 2 GeV CesrTA operations. For these conditions the amplifier dynamic range was optimized to allow measurements with 3x109 to 1011 particles per bunch. Initial testing is complete. Data analysis and examples of key measurements which illustrate the instrument's performance are presented. This device offers unique measurement capabilities applicable to future high energy physics accelerators and light sources. | ||