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| MOPC047 | Status of Kharkov X-ray Generator NESTOR Based on Compton Back Scattering | injection, electron, storage-ring, laser | 175 | ||
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The purpose of the NESTOR (New Electron STOrage Ring) project is to create intense X-ray generator based on compact storage ring and Compton back scattering in the National Science Centre “Kharkov Institute of Physics and Technology”. It allows to carry out investigations in the wide range of fundamental and applied sciences such as physics, biology, medicine and so on. The facility consists of the compact 40-225 MeV storage ring, linear 35-90 MeV electron accelerator as an injector, transportation system and Nd:Yag laser and optical cavity. In addition to hard Compton radiation it is supposed to use 4 soft vacuum ultraviolet radiation channels of natural synchrotron radiation of dipole. The facility is going to be in operation in the middle of 2009 and the expected X-rays flux will be of about 1013 phot/s. In the paper the main facility parameters are presented.
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| MOPC050 | Ground Motion Studies at NSLS II | site, ground-motion, storage-ring, background | 184 | ||
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In 3rd generation light sources such as the 3 GeV NSLS II under design at BNL, strict requirements associated with vibration on the storage ring floor are imposed in order to minimize the jitter in the electron beam. Spectral characteristics storage ring vibration and dynamic properties of the ring lattice are controlling parameters. Ground motion at the NSLS-II site is characterized by a complex spectrum consisting of fast and slow motions stemming from natural and cultural sources. Cultural noise with frequencies higher than a few Hz has the potential of dramatically affecting the accelerator performance. In this study, an array of vibration measurements at the undisturbed NSLS II site has been made in order to establish the “green-field” vibration environment and its spectral characteristics. Its interaction with the NSLS II accelerator structure and the quantification of the storage ring vibration, both in terms of amplitude and spectral content have been assessed through a state-of-the-art wave propagation and scattering analysis. This paper focuses primarily on the wave propagation and scattering aspect as well as on the filtering effects of accelerator structural parameters.
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Work performed under the auspices of the US DOE. |
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| MOPC053 | BEAM DYNAMICS IN THE LASER-ELECTRON STORAGE RING FOR A COMPTON X-RAY SOURCE | laser, electron, photon, lattice | 187 | ||
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We present the lattice analysis and simulation study of the beam dynamics in the pulse mode of the laser-electron storage ring. Compton Scattering (CS), Intra-beam Scattering (IBS) with non-Gaussian beam and Synchro-tron Radiation (SR) are taken into consideration. Emittance growth, energy spread and phase space of the electron beam, as well as spatial and temporal distribution of the scattered photon are studied in this paper.
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| MOPC056 | Challenges for Beams in an ERL Extension to CESR | linac, emittance, electron, undulator | 190 | ||
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Cornell University is planning to build an Energy-Recovery Linac (ERL) X-ray facility. In this ERL design, a 5 GeV superconducting linear accelerator extends the CESR ring. Currently CESR is used for the Cornell High Energy Synchrotron Source (CHESS). The very small electron-beam emittances would produce an x-ray source that is significantly better than any existing storage-ring light source. However, providing, preserving, and decelerating a beam with such small emittances has many issues. We describe our considerations for challenges such as optics, space charge, dark current, coupler kick, ion accumulation, electron cloud, intra beam scattering, gas scattering, radiation shielding, wake fields including the CSR wake, and beam stabilization.
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| MOPC064 | Beam Losses Due to Intra-Beam and Residual Gas Scattering for Cornell's Energy Recovery Linac | beam-losses, radiation, undulator, simulation | 214 | ||
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In this paper we analyze particle loss rates in Cornell's x-ray Energy Recovery Linac. Because of the small beam emittances and high beam intensity, intra-beam scattering (IBS) can be a source of significant particles loss in the horizontal plane. It will result in radiation doses which should be carefully examined for adequate radiation protection. Additionally, scattering on the residual gas (RGS) causes particle losses in the vertical plane. With Mote-Carlo type simulations of the scattering processes and transport matrixes for particle-trajectory propagation we found the beam loss distribution along ERL. It indicated that 99% of the total beam loss will be due to IBS. However, the RGS contribution can not be ignored because it dominates scattering in the vertical plane causing IDs irradiation and damage. For both (IBS and RGS) processes the highest beam losses will occur at the end of deacceleration due to adiabatic anti-damping causing traverse betatron amplitudes to increase. These beamlosses can be consentrated in collimation sections. Knowing RGS beam loss rates at the ID locations, we estimate the ID’s life time and suggest a radiation protection scheme.
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| MOPC092 | Single Particle Multi-turn Dynamics During Crystal Collimation | simulation, proton, collimation, betatron | 277 | ||
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As the increase in luminosity remains a high-profile issue for current and future accelerator projects, protecting superconducting magnets from beam induced quenches implies using state-of-the-art halo cleaning devices given the required beam intensities. In CERN's LHC case, a multi-stage collimation system is being set up so as to provide a halo cleaning efficiency up to 99.995%. In order to improve this system even further, US-LARP funded studies have started to appreciate the use of a silicon-based crystal as a primary target for the halo particles. Dedicated experiments have recently been performed in an SPS extraction line for a bent silicon crystal in case of single-pass particles. This article compares the published results of this experiment with simulations using established tracking codes. The goal is to better describe the main physics mechanisms involved in the beam-crystal interaction. A simple algorithm is then introduced to allow for fast tracking of the effect of a crystal on a high energy proton beam over many turns. The general feasibility of single particle, multi-turn crystal experiments at the SPS (CERN) and Tevatron (Fermilab) and their outline are discussed.
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| MOPP006 | Machine Induced Backgrounds for FP420 | proton, background, simulation, betatron | 559 | ||
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The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors at 420m from the ATLAS and/or CMS interaction points. Such detectors aim at measuring diffracted protons, which lost less than 2% of their longitudinal momentum. The success of this measurement requires a very good understanding of the charged and neutral particle environment in the detector region in order to avoid the signal being swamped as well as for detector survivability. This background receives contributions from beam-gas interactions, halo particles surviving from the Betatron and momentum cleaning systems and secondary showers produced by particles from the 14TeV collision region striking the beampipe upstream of the FP420 detectors. In this paper, such background sources are reviewed, and the expected background rates calculated.
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| MOPP034 | Large Scale Linac Simulations Using a Globalised Scattering Matrix Approach | simulation, linac, dipole, electromagnetic-fields | 619 | ||
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A globalised cascaded scattering matrix scheme serves as practical method to simulate the electromagnetic (e.m.) fields in the groups of cavities which constitute the main accelerating structures of a linac. The cascaded scattering matrix technique is a well-proven method which allows realistic fabrication errors to be incorporated in an efficient manner without the necessity to re-mesh the entire geometry. Once the unit cell structures have been determined using a numerical scheme, such as finite element method utilized here, the overall cascaded scattering matrix calculation requires little in the way of computational resources or time and is consequently an efficient means of characterizing the e.m. field. Details of the e.m. field, shunt impedance and trapped modes for large scale linac simulations applied to the baseline and alternate high gradient cavities for the ILC and applications to XFEL are presented.
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| MOPP071 | Intense Stopping Muon Beams | dipole, target, background, proton | 712 | ||
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The study of rare processes using stopping muon beams provides access to new physics that cannot be addressed at energy frontier machines. The flux of muons into a small stopping target is limited by the kinematics of the production process and by stochastic processes in the material used to slow the particles. Innovative muon beam cooling techniques are being applied to the design of stopping muon beams in order to increase the event rates in such experiments. Such intense stopping beams will also aid the development of applications such as muon spin resonance and muon-catalyzed fusion.
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| MOPP074 | Improvement of an S-band RF-gun cavity with a Cs-Te Photo-cathode | cathode, electron, impedance, resonance | 721 | ||
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A 1.6cell S-band photo-cathode RF-Gun is one of the good alternatives of the short pulse electron source. Therefore,we are operating as a high brightness short pulse electron source for studying a reaction of radiation chemistry,an inverse Compton scattering at Waseda University and as an injector at KEK-ATF. To improve an electron beam quality and to reduce a dark current,we decided to improve the RF-Gun cavity. Frequency tuning of the half cell of existing RF-gun was performed by the torque control of Helicoflex seal on the cathode plate and two moving rod type tuners were installed on the full cell. Newly designed RF-Gun cavity has four compact tuners on each cell,which can be tune the frequency to deform the cavity wall,to remove the Helicoflex seal and tuning holes that were considered to be the major cause of electric discharge and/or a dark current source. According to these improvements,the Q-value and shunt impedance of the cavity is 30% larger than that of existing guns. As the result,the reduction of dark current is succeeded and the beam energy is reached up to 5.5MeV at 10MW RF input. The detailed results of electron beam generation will be reported at the conference.
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| MOPP093 | Fast L-band Waveguide Phase Shifter | insertion, acceleration | 769 | ||
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During the operation of accelerators it is often important to rapidly change the parameters of the RF system, such as cavity resonant frequency, coupling, or electrical length. For this purpose a fast L-band planar phase shifter has been designed, that has advantages compared to the coaxial scheme considered before by the authors (EPAC 06). The phase shifter is based on a new ferroelectric ceramic, whose permittivity changes with application of an external voltage. The switching time depends on only the external HV circuit and can by less than a few microseconds. The conceptual design and electrical parameters of the new phase shifter are presented, as are first results of low power measurements on a 1/3 model.
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| MOPP127 | Commissioning of Superconducting Linac at IUAC - Initial Challenges and Solutions | linac, acceleration, vacuum, damping | 856 | ||
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During initial acceleration of ion beam through the first module of linac having eight superconducting (SC) niobium quarter wave resonators (QWR), energy gains were found to be much lower. Major problem encountered was limitation of accelerating fields in the QWR achieved at much higher RF power (up to 300 W) leading to cable melting, metal coating on SC surface and increased cryogenic losses. Cold leaks in the niobium-stainless steel transition assemblies and niobium tuner bellows also posed a major challenge. A novel way of damping mechanical vibration was implemented to reduce RF power. Cooling was improved by installing a hemispherical structure on the resonator. The drive coupler was redesigned to eliminate metal coating. Design of the tuner/transition flange assemblies was modified to avoid cold leak. After incorporation of these modifications, on-line beam acceleration through Linac was accomplished. Pulsed (1.3 ns) Silicon beam of 130 MeV from Pelletron accelerator was further bunched to 250 ps by SC Superbuncher. After acceleration through the linac module and subsequent re-bunching using SC Rebuncher, 158 MeV Silicon beam having pulse width of 400 ps was delivered.
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| TUPC039 | p-Carbon CNI Polarimetry in the AGS and RHIC | polarization, target, vacuum, proton | 1140 | ||
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Polarimetry based on proton carbon elastic scattering in the Coulomb Nuclear Interference (CNI) region has been utilized for Relativistic Heavy Ion Collider (RHIC). They have been critical tools for polarized proton acceleration setup and provided polarization values for RHIC experiments. This paper summarizes the recent modifications to the hardware and electronics. The performance of the polarimeters is also discussed.
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| TUPC047 | Optical Transition Radiation Interferometry for the A0 Photoinjector | electron, vacuum, radiation, optics | 1164 | ||
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OTR interferometry (OTRI) is a promising diagnostic technique and was successfully developed and used for investigation of relativistic beams. For mid-energy accelerators the technique is traditionally based on thin polymer films (the first one is transparent for visible light) providing the beam multiple scattering of about 1 mrad or less. The disadvantage of these films is the unacceptable vacuum properties for photoinjectors and accelerators using superconducting cavities. We studied the application of thin mica sheets for OTRI diagnostics at the A0 Photoinjector in comparison with 2.5 μm thick Mylar films. This diagnostic is also applicable for the ILCTA-NML accelerator test facility that is planned at Fermilab. The experimental setups of the OTR interferometer for the A0 Photoinjector are described in the report. Results of simulations and measurements and comparison of the results obtained using Mylar and Mica-based interferometers are presented and discussed.
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| TUPC124 | Development of a High Power Fibre Laser for Laser Based Electron Beam Diagnostics | laser, collider, linear-collider, electron | 1359 | ||
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We present the latest results on the development of a high power fibre laser system for the laserwire project on ILC-like laser based electron beam diagnostics. The laser consists of a solid state oscillator which can be synchronised to an external frequency reference, and two amplification stages in double clad doped fibre, giving 1uJ pulses in a burst mode suitable for the ATF2 laserwire project. This output is amplified in large mode area photonic crystal fibre to generate the high pulse energy necessary for Compton scattering without any deleterious nonlinear effects, whilst maintaining the high spatial mode quality and beam pointing stability of a fibre laser. These properties are essential for producing the sub-micron spot sizes required for the measurement of small particle beam sizes.
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| TUPD022 | Electron Beam Polarimetry at the S-DALINAC | electron, polarization, target, background | 1476 | ||
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It is planned to carry out experiments at the Superconducting Darmstadt Linear Accelerator S-DALINAC with both polarized electron and photon beams at the energy of the electron beam between 10 and 130 MeV. In order to extract asymmetry from these experiments the absolute degree of the electron beam polarization needs to be known. We present the existing and planned polarimeters at the source of polarized electrons and the experimental sites, especially a 100 keV Mott polarimeter and Möller polarimeter for 15-130 MeV electrons.
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| TUPD027 | Commissioning of the Offline-teststand for the S-DALINAC Polarized Injector SPIN | electron, polarization, cathode, laser | 1482 | ||
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At the superconducting Darmstadt linear electron accelerator S-DALINAC a new injector for polarized electrons is under development. For this purpose an off-line test stand has been constructed. It consists of the source of polarized electrons and a test beamline including a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and various beam steering and diagnostic elements. The polarized electron beam is produced by photoemission from a strained GaAs cathode. We report on the status of this project and present first results of the measurements of the beam properties. We also give an outlook on the upcoming installation of SPIN at the S-DALINAC.
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| TUPD031 | Crystals Application in the TOTEM Experiment to Increase the Acceptance of a Roman Pot | proton, optics, simulation, closed-orbit | 1491 | ||
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Bent crystal may enhance the physics reach of a near-beam physics detector in the CERN-LHC, by increasing the acceptance of scattered protons in low transverse momentum reactions. As an example we present simulations demonstrating the increase of the Roman Pot acceptance in the TOTME apparatus. Starting from the MadX v6.5 nominal optic, a crystal is placed at different longitudinal and transversal positions: for each scheme a gaussian beam of protons with different kinematic variables is created and tracked along the optical line with crystal. The number of protons with transversal coordinates greater than 10σ+0.5mm, that is inside the Roman Pot, is compared with the total number of protons. The possible gain in acceptance is around 15-20%.
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| TUPP040 | Intra Beam Scattering in Linear Accelerators, Especially ERLs | linac, simulation, lattice, radiation | 1631 | ||
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The theories of beam loss and emittance growth by Touschek and Intra Beam Scattering have been formulated for beams in storage rings. It is there that these effects have hitherto been important because of their large currents. However, there are linear accelerators where these effects become important when considering loss rates and radiation damage. Prime examples are high current Energy Recovery Linacs (ERLs), managing these scattering effects can become challenging, and not only because of the large current, but also because the deceleration of the spent beam increases relative energy spread and transverse oscillation amplitudes. In this paper we describe two ways of simulating particle loss by these scattering affects, both implemented in BMAD. One that yields the places where scattering occurs, and another that yields loss rates along the chamber walls. BMAD includes nonlinear beam dynamics, wake effects, and more, which allows a rather complete propagation of scattered particle. For the example of the ERL x-ray facility that Cornell plans to build, we demonstrate that these capabilities are very important for designing a functional radiation protection system.
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| TUPP042 | Status of the ORBIT Code: Recent Developments and Plans | acceleration, injection, collimation, synchrotron | 1637 | ||
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We report on recent enhancements to the physics modules of the ORBIT Code and on progress toward a new implementation of ORBIT using python. We have developed the capability to track particles through general three dimensional electromagnetic field configurations. This facility has proved essential in modeling beam transport through the complicated magnetic field regions of the SNS injection chicane and injection dump line, where beam losses are high. We have also enhanced the acceleration module to provide more flexibility for synchrotron calculations. Finally, progress continues on the migration of the ORBIT physics models to a python user environment, and we present the status of this work.
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| TUPP062 | Beam Coupling Impedance Studies on LHC FP420 Multi-pocket Beam Pipe Prototype | impedance, simulation, coupling, resonance | 1682 | ||
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The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors 420m from the ATLAS and/or CMS interaction points. The latest prototype of a FP420 station consists of a modified LHC beam pipe in which two pockets hosting the detectors introduce an abrupt cross-section variation of the pipe. During the FP420 proposed operation, each station is moved towards the beam as close as 3 mm (~ 10 σx). The impact on the LHC beam coupling impedance has been evaluated with a laboratory wire measurement and a suite of numerical simulations. In addition, we describe a proposed modification of the beam pipe design which minimizes the impedance of the resonances without compromising the FP420 detector signal to background ratio.
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| TUPP102 | Beam Transport with Scattering Using SRIM Supporting Software Routines Code | beam-transport, emittance, simulation, ion | 1767 | ||
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In many situations a particle beam is transported through matter-containing components separated by ion-optical elements. The matter-containing components scatter the beam and alter its emittance diagram. In order to include accurately the scattering in beam-transport a special beam-transport module was included in the SRIM Supporting Software Modules package (S3M)*. It uses transfer-matrix formalism in ion-optical elements. At the entry to a scattering element a beam-generation routine converts the actual σ-matrix into an ensemble of particles and writes a special SRIM input-file. The beam-transport in the scattering element is then calculated by SRIM MC particle tracking. At the exit of the scattering element, the module imports back the SRIM output data and can either continue with transfer-matrix transformations or generate a modified σ-matrix that can be used by other ion-optical programs. It means the beam transport with scattering can either be fully calculated by S3M, or data exchange between S3M and ion-optical programs can be provided. S3M beam-transport module is described in the paper with some typical application examples.
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*M. Pavlovic, I. Strasik. Supporting Routines for the SRIM code, Nucl. Instr. and Meth. B 257 (2007) 601-604. |
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| TUPP155 | Compact EUV Source Based on Laser Compton Scattering between Micro-bunched Electron Beam and CO2 Laser Pulse | laser, electron, undulator, radiation | 1869 | ||
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High-power extreme ultra-violet (EUV) sources are required for next generation semiconductor lithography. We start developing a compact EUV source in the spectral range of 13-14 nm, which is based on laser Compton scattering between a micro-bucnhed electron beam and a high intensity CO2 laser pulse. The electron beam extracted from a DC photocathode gun is micro-bunched using laser modulation techinque and a magnetic compressor before the main laser Compton scattering for EUV radiation. We will describe a considerating scheme for the compact EUV source based on laser Compton scattering with micro-bunched electron beam and the result of its numerical studies. A plan of test experiment generating micro-bunched electron beam will be also introduced in this conference.
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| TUPP156 | Development of a Compact X-ray Source Based on Laser-Compton Scattering with a Pulsed-laser Super-cavity | laser, electron, photon, target | 1872 | ||
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A compact and high quality x-ray source is required for various fields, such as medical diagnosis, drug manifacturing and biological sciences. Laser-Compton based x-ray source that consists of a compact electron storage ring and a pulsed-laser super-cavity is one of the solutions of a compact x-ray source. Pulsed-laser super-cavity has been developed at KEK-ATF for a compact high brightness x-ray source. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. Recently, 357MHz mode-locked Nd:VAN laser pulses can be stacked stably in a 420mm long Fabry-Perot cavity with 2.5kW average power in our R&D. On the other hand, we have succeeded to stack the pulsed amplified laser in the super-cavity. This indicates that the number of X-ray is multiplied due to the gain in the amplification system to synchronize the pulsed pump to the beam. In view of this successful result, we have started an X-ray generation experiment using a super-cavity and a multi-bunch electron beam at KEK-LUCX. Development of the super-cavity and the results of X-ray generation experiment will be presented at the conference.
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| TUPP158 | Development of Laser System for Compact Laser Compton Scattering X-ray Source | laser, electron, gun, linac | 1878 | ||
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A compact X-ray source via laser Compton scattering is required for biological, medical and industrial science because it has many benefits about generated X-rays such as short pulse, quasi-monochromatic, energy tunability and good directivity. Our X-ray source is conventionally the single collision system between an electron pulse and a laser pulse. To increase X-ray yield, we have developed a multi-collision system with a multi-bunch electron beam and a laser optical cavity. The multi-bunch beam will be generated from a Cs-Te photocathode rf gun sytem using a multi-pulse UV laser system. The laser optical cavity will be built like the regenerative amplification including the collision point between the electron pulse and the laser pulse to enhance the laser peak power per 1 collision on laser Compton scattering. In this conference, we will describe the results of preliminary experiments for the multi-collision system and future plans.
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| WEPC014 | Beam Lifetime Studies of Hefei Advanced Light Source (HALS) Storage Ring | coupling, emittance, lattice, storage-ring | 2016 | ||
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Hefei Advanced Light Source (HALS) will be a high brightness light source with about 0.2nmrad emittance at 1.5GeV. Ultra low beam emittance and relatively low beam energy of HALS would result in poor beam lifetime. Comparing the beam-gas scattering and Touschek scattering effects, a conclusion can be drawn that Beam lifetime will be affected strongly by Touschek scattering. Touschek lifetime has been studied considering linear and nonlinear effects for the lattice structure. Relations between lifetime and RF cavity voltage, lifetime and emittance coupling, lifetime and gap heights of insertion devices have been calculated respectively. After the optimization, proper cavity voltage and emittance coupling are chosen to get about 1.06 hours of total lifetime including gas scattering losses effect. Installing a third harmonic RF cavity can lengthen the beam bunch to increase the total lifetime to about 3.85 hours. Top up injection operation will be applied to keep bunch current within the required value.
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| WEPC164 | Development of Modulating Permanent Magnet Sextupole Lens for Focusing of Cold Neutrons | sextupole, focusing, dipole, permanent-magnet | 2392 | ||
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A modulating permanent magnet sextupole lens that can focus pulsed cold neutrons is under development. It is based on the extended Halbach configuration to generate stronger magnetic field. In order to adjust the strength, the magnet is divided into two co-axial nested rings, where the inner ring is fixed and the outer ring can be rotated. Synchronizing the period of the modulation with that of pulsed neutron beam suppress the chromatic aberration. We have fabricated a half-scale model and studied the strength, the torque and the temperature rise caused by eddy current. Now we are developing the full-scale model improving such problems. These two scale models of magnet are described.
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| WEPP058 | Optics Measurements and Matching of TT2-TT10 Line for Injection of the LHC Beam in the SPS | optics, injection, emittance, betatron | 2650 | ||
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A well matched injection in the SPS is very important for preserving the emittance of the LHC beam. The paper presents the algorithms used for the analysis and the results of the optics measurements done in the transfer line TT2-TT10 and in the SPS. The dispersion is computed by varying the beam momentum and recording the offsets at the BPMs, while the Twiss parameters and emittance measurements in TT2-TT10 are performed with beam profile monitors equipped with OTR screens. These results are completed by those obtained with a matching monitor installed in the SPS as a prototype for the LHC. This device makes use of an OTR screen and a fast acquisition system, to get the turn by turn beam profiles right at injection in the ring, from which the beam mismatch is computed and compared with the results obtained in the line. Finally, on the basis of such measurments, a betatron and dispersion matching of TT2-TT10 for injection in the SPS has been performed and successfully put in operation.
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| WEPP070 | High Efficiency Collimation with Bent Crystals | collimation, alignment, proton, simulation | 2680 | ||
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A revolutionary collimation approach is being developed by the H8RD22 collaboration. The basic idea is to replace the amorphous jaws, which spread the beam halo in the whole solid angle, with bent crystals, which are able to deviate the halo particles in a given direction outside the beam core. Studies to investigate the bent crystal properties have been carried out over the past 3 years at the H8 beam line (CERN SPS) with a 400 GeV/c proton beam. The crucial result of these studies is the observation of the Volume Reflection effect, the coherent scattering of the beam on the crystalline plane which provides a small but very efficient (respectively, 14 μrad and 98% at 400 GeV/c) particle deflection. The high efficiency (which should increase at higher energy) combined with a large angular acceptance (~100 μrad) led to the development of multi-reflection systems to increase the deflection angle. Nowadays this system has reached the stage to be tested in a circular accelerator as a primary collimator to verify the effective collimation efficiency in a complex environment. The second phase of the LHC collimation could be the first application of this crystal based system.
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| WEPP099 | Results from Atomic Layer Deposition and Tunneling Spectroscopy for Superconducting RF Cavities | superconductivity, vacuum, coupling, electron | 2749 | ||
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Atomic Layer Deposition is a process that synthesizes materials in successive monolayers, at rates on the order of 1 micron/hour. We have been using this technique at Argonne as a possible way to improve both superconducting rf (SCRF) and normal rf structure performance. Initial experiments have led to a new model of high field Q-slope and new ways of controlling SCRF surfaces, as well as suggesting ways to significantly improve the operating gradients of both superconducting and normal structures. We have also been testing this technique in superconducting structures. Initial measurements show significant improvement over “cavity-grade” Nb samples.
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| THPC015 | Computational Beam Dynamics Studies for Improving the Ring Injection and Extraction Systems in SNS | injection, quadrupole, septum, coupling | 3008 | ||
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The ring injection and extraction systems must function as designed in order for the Spallation Neutron Source (SNS) to achieve its specified performance. In commissioning and early operations we have encountered problems that have been traced to these systems. We experienced high beam losses in and around the injection dump, the rectification of which has necessitated significant study and development by a multidisciplinary team. The results include a number of enhancements of existing features and the addition of new elements and diagnostics. The problem in the extraction region stems from tilted beam distributions observed in the ring-to-target beam transport line (RTBT) and on the target, thus complicating the control of the beam-on-target distribution. This indicates the inadvertant introdution of x-y beam coupling somewhere upstream of the RTBT. The present paper describes computational studies, using the ORBIT Code, addressed at the detailed understanding and solution of these problems.
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