| Paper | Title | Page |
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| THP001 | Hybrid Electron Linac Based on Magnetic Coupled Accelerating Structure | 2136 |
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| This paper presents the design of a hybrid linac which consists of a standing wave buncher and a travelling wave accelerating part. Both electric and magnetic-coupled disk-loaded waveguide (DLW) could be used as accelerating structure. The last one has better electrodynamical parameters comparing to classical DLW. Such an accelerator possesses the advantages of both standing wave and travelling wave linacs and has better output beam parameters. | ||
| THP002 | Re-Circulated Inverse Compton Scattering X-ray Source for Industrial Applications | 2139 |
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| An experiment is under way at the Accelerator Test Facility (ATF) at BNL to demonstrate inverse Compton scattering in a pulse-train regime. A photoinjector generated electron beam pulse train is scattered by a recirculating laser pulse in a novel resonant configuration termed Recirculation Injection by Nonlinear Gating (RING). The goal of the experiment is to demonstrate strong enhancement of the ICS photon flux through laser recirculation. The project status is presented, and the long-term outlook is discussed with emphasis on the medical and security applications. | ||
| THP003 | High Power THz FEL Source Based on FFAG Betatron | 2142 |
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| A novel source of high power sub-mm waves is proposed that combines two well-known technologies – a betatron induction FFAG accelerator and a free electron laser (FEL). The system is configured as an FEL oscillator: the electron beam circulates in bi-periodic FFAG lattice and the external optical resonator maintains beam-radiation overlap through multiple orbits. Initial analysis shows that FEL gain and very high extraction efficiency are possible with modest injected beam current. A simplified interaction model and preliminary analysis results are presented. | ||
| THP005 | High Power Cyclotron Complex for Neutron Production | 2145 |
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| Now the cyclotron seems as the most suitable accelerator for production of proton beams with energy up to Ep= 800 MeV and the power Pp=10 MW. There are some offers on creation of such complexes, all of them have common properties. A full cycle of acceleration consists of three stages: high-voltage injection with bunching of continuous beam, then preliminary acceleration in fore sectors cyclotron and acceleration up to the maximal energy 500-800 MeV in the ring cyclotron with six or more sectors. At the first stage of acceleration instead of high-voltage injection one can use the parallel work of two cyclotrons with injection in the subsequent cascade of a beam of the double intensity. In our department of New Accelerators the magnetic and high-frequency systems of a ring cyclotron on the energy 50 - 800 MeV (so-called “supercyclotron”) have been developed. A project of cyclotron injector with energy of protons about 10 MeV has been suggested as injector for Fasotron JINR LNP. It is offered to continue development of the project of cyclotron facility with energy of protons Ер ~ 800 MeV and average current of beam up to 10 mA. | ||
| THP006 | Status of High Current R&D Energy Recovery Linac at Brookhaven National Laboratory | 2148 |
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| An ampere-class 20 MeV superconducting energy recovery linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing of concepts relevant for high-energy coherent electron cooling and electron-ion colliders. One of the goals is to demonstrate an electron beam with high charge per bunch (~5 nC) and low normalized emittance (~5 mm-mrad) at an energy of 20 MeV. A flexible lattice for the ERL loop provides a test bed for investigating issues of transverse and longitudinal instabilities and diagnostics for CW beam. A superconducting 703 MHz RF photo-injector is considered as an electron source for such a facility. We will start with a straight pass (gun/cavity/beam stop) test for gun performance studies. Later, we will install and test a novel injection line concept for emittance preservation in a lower-energy merger. Here we present the status and our plans for construction and commissioning of this facility. | ||
| THP007 | FEL Potential of eRHIC | 2151 |
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Brookhaven National Laboratory plans to build a 5-to-30 GeV energy-recovery linac (ERL) for its future electron-ion collider, eRHIC. In past few months, the Laboratory turned its attention to the potential of this unique machine for free electron lasers (FELS), which we initially assessed earlier*. In this paper, we present our current vision of a possible FEL farm, and of narrow-band FEL-oscillators driven by this accelerator.
* V.N. Litvinenko, I. Ben-Zvi, Proceedings of FEL'2004, http://jacow.org/f04/papers/WEBOS04/ |
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| THP009 | Collimator Design of 15 MeV Linear Accelerator Based Thermal Neutron Source for Radiography | 2154 |
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| Neutron Radiography is a powerful non-destructive testing technique used for the analysis of objects which are widely used in security, medical, nuclear and industrial applications. Optimization of the thermal neutron radiography facility has been carried out using 15 MeV LINAC based neutron source. In this case, a neutron collimator has been designed along with g-n target, moderator, reflector and shielding. The g-n target has been optimized based on their photonuclear threshold. The moderating properties have been studied for few light elements to optimize best suitable moderator for radiography system. The major part of the design was to optimize the collimator for neutron beam which decides quality of the image given. To get best values of collimator parameters such as collimation ratio, gamma content, neuron flux, cadmium ratio, beam uniformity, etc. a FLUKA simulation was carried out. The collimator has been optimized with cadmium lining square cone to capture the scattered thermal neutrons and the collimation ratio to L/D=18. The neutron flux of the optimized facility obtained at the object plane is 1.0·10+5 n/(cm2-sec1) and neutron to gamma ratio is 1.0·10+5 n/(cm2-mR1). | ||
| THP010 | Optimization of Dual Scattering Foil for 6 to 20 MeV Electron Beam Radiotherapy | 2157 |
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| From last 50 years, electron beam therapy has an important radiation therapy modality. The electron beam from the LINAC is of size ~ 2 mm, whereas the size required for actual treatment is usually larger than 2 X 2 cm2 up to 30 X 30 cm2 at the isocenter. In the present work, it is proposed to use dual scattering foil system for production of clinical electron beam. The foils for 6 to 20 MeV electrons were optimized using the Monte Carlo based FLUKA code. The material composition, thickness of primary foil, Gaussian width and thickness of secondary foil were optimized such that it should meet the design parameters such as Dose at iso-center, beam uniformity, admixture of bremsstrahlung, etc. A pencil beam of electrons passing through primary foil converted into Gaussian shape and falling at the centroid of secondary foil which experienced maximum scattering, whereas falling at the edge experienced the minimum scattering. This results into flat profile of electron at isocenter. In conclusion, the primary scattering foil has been optimized with high Z element (Ta) having uniform thickness, whereas the secondary foil has been optimized with low Z element (Al) having Gaussian shape. | ||
| THP012 | Development of Imaging Techniques for Medical Accelerators in the QUASAR Group | 2160 |
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Funding: Work supported by the EU under contract PIIF-GA-2009-234814, PITN-GA-2008-215080 and DFG under WE3565/5. Ions offer an increased precision in radiotherapy due to their specific depth-dose properties. This precision can only be fully exploited if exact knowledge of the particle beam properties, as well as the exact range of the particles in the inhomogeneous target, is available. The QUASAR Group has addressed the key issues in a number of different ways: Using a monolithic active pixel sensor, designed for dead time-free operation, we have developed a beam monitoring system capable of monitoring pulsed and continuous beams at typical therapeutic energies and intensities in real time during patient treatment; using a non-intrusive detector system based on the VELO detector, we will measure variations in beam properties without intersecting the beam core altogether; using liquid ionization chambers, we aim at obtaining information on the biological quality of the beam; using a simple set-up based on a silicon pixel detector, developed for the ALICE experiment, we have demonstrated the feasibility of detecting the distal edge of the Bragg peak in antiproton beams by detecting the pions resulting from pbar-nucleon annihilations. This paper gives an overview of these studies. |
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| THP016 | Design of an Achromatic and Uncoupled Medical Gantry for Radiation Therapy | 2163 |
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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. We are presenting the layout and the optics of a beam line to be used as a medical gantry in radiation therapy. The optical properties of the gantry’s beam line are such as to make the beam line achromatic and uncoupled. These two properties make the beam spot size, which is delivered and focused by the gantry, on the tumor of the patient, independent of the angular orientation of the gantry. In this paper we present the layout of the magnetic elements of the gantry, and also present the theoretical basis for the optics design of such a gantry. * N. Tsoupas et. al. “Uncoupled achromatic tilted S-bend” Presented at the 11th Biennial European Particle Accelerator Conference, Genoa, Italy, June 23-27,2008 |
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| THP020 | Effects of 6 MeV Electron Irradiation on ZnO Nanoparticles Synthesized by Microwave Method | 2166 |
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| The sizes of zinc-oxide (ZnO) nanoparticles were synthesized by microwave method and were tailored by electron irradiation method. The ZnO nanoparticles having size of ~46 nm synthesised by microwave method were exposed to different fluences of 6 MeV electrons over the range from 1x1015 to 2.5x1015 e- /cm2. The electron irradiated ZnO nanoparticles were characterized by XRD, SEM, UV techniques. The XRD results show that the particle size reduced continuously from 46 nm to 15 nm with the increase in electron fluence and SEM images also confirms the formation of nanoparticles of minimum size of around 14 nm. The band gap of the ZnO nanoparticle also increased from 3.29 to 3.42 eV as the size reduced. The result shows the ZnO particles are broken in to smaller size under electron irradiation and increase in the band gap indicates the formation of defects in ZnO. The electron irradiation method is found to be an efficient method in tailoring the size of ZnO nano particles. The nanosized ZnO particles can suit for the applications such as photovoltaics, photocells and antimicrobial activity. | ||
| THP025 | A Cooled Generalized Multiple Target System to Create Positrons for a Compact Tunable Intense Gamma Ray Source | 2169 |
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Funding: This work was funded by Pacific Northwest National Laboratory which is operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830. A compact tunable gamma ray source has many potential uses in medical and industrial applications. One novel scheme to produce an intense beam of gammas relies on the ability to create a high flux of positrons, which are produced by an electron beam on a high Z target. We present an innovative system which allows for a nearly arbitrary targeting geometry that supports multiple targets, whose optimal design is allowed to be driven by the physics of the positron production processes, while naturally supporting cooling of the targets. |
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| THP027 | Status and Development of a Proton FFAG Accelerator at KURRI for ADSR Study | 2172 |
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| In Kyoto University Research Reactor Institute (KURRI), the fixed-field alternating gradient (FFAG) proton accelerator has been constructed to make an experimental study of accelerator driven sub-critical reactor (ADSR) system with spallation neutrons produced by the accelerator. The world first ADSR experiment has been carried out in March of 2009. The proton FFAG accelerator consists of three FFAG rings; injetor (spiral sector FFAG), booster(radial sector FFAG) and main ring(radial sector FFAG), respectively. In March 2010, the experiment conducted with a thorium-loaded accelerator driven system using the proton FFAG accelerator has also been carried out. In order to increase the beam intensity of the proton FFAG accelerator, a new injector with H− ions is under construction. In this scheme, H− ions accelerated up to the energy of 11 MeV with a linac are injected into the main ring with charge-exchange injection. In this paper, the details of ADSR experiments with the proton FFAG accelerator at KURRI, and also the R&Ds of the accelerator will be presented. | ||
| THP029 | Temperature and Optimize Design of Beam Window in the Accelerator | 2175 |
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| Careful evaluation of the heat-transfer and corresponding problems is important in the beam window in the design and operation of Accelerator Driven sub-critical System (ADS). Using the Monte-Carlo code Fluka, we studied the energy deposition of the beam window in high power proton accelerator. The temperature distribution of the beam window is calculated in presence of the coolant. The process of computation for various materials will be introduced, and an optimized design scheme is given. The results suggest that some measures could be used to reduce the damage to the beam window, such as dividing current into branch currents, expanding the bunch or using beryllium as the material of the beam window, et al. | ||
| THP030 | GEANT4 Studies of the Thorium Fuel Cycle | 2178 |
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| Thorium “fuel” has been proposed as an alternative to uranium fuel in nuclear reactors. New GEANT4 developments allow the Monte Carlo code to be used for the first time in order to simulate the time evolution of the concentration of isotopes present in the Thorium fuel cycle. A full study is performed in order to optimise the production of Uranium-233 starting with "pure" Thorium fuels, leading to levels of Uranium-233 which ensure the operation of the nuclear reactor in a regime close to criticality. | ||
| THP034 | Accelerators for Subcritical Molten Salt Reactors | 2181 |
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Funding: Supported in part by Accelerator Technologies Inc. Accelerator parameters for subcritical reactors that have been considered in recent studies * are based on using solid nuclear fuel much like that used in all operating critical reactors as well as the thorium-burning accelerator-driven energy amplifier ** proposed by Rubbia et al. An attractive alternative reactor design that used molten salts was experimentally studied at ORNL in the 1960s, where a critical molten salt reactor was successfully operated using enriched U235 or U233 tetrafluoride fuels ***. These experiments give confidence that an accelerator-driven subcritical molten salt reactor will work as well or better than conventional reactors, having better efficiency due to their higher operating temperature and having the inherent safety of subcritical operation. Moreover, the requirements to drive a molten salt reactor are considerably relaxed compared to a solid fuel reactor, especially regarding accelerator reliability and spallation neutron targetry, to the point that the required technology exists today. * http://www.er.doe.gov/hep/files/pdfs/ADSWhitePaperFinal.pdf ** http://wikipedia.org/wiki/Energy_amplifier *** Paul N. Haubenreich and J. R. Engel, Nuc. Apps & Tech, 8, Feb. 1970 |
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| THP037 | Design of an e-γ Converter for a 10 MeV Electron Beam | 2184 |
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| In the last years, the INFN-Gruppo Collegato di Messina has designed and setup an x-ray source based on the 5 MeV electron linac hosted at the Dipartimento di Fisica - Università di Messina. In the meanwhile, and in the framework of an European funding, the group has setup the Centro Ricerche at Villafranca Tirrena (Messina, Italy) which holds a 10 MeV electron linac and which is, at the moment, mainly devoted to industrial Radiation Processing applications. Nevertheless, to the aim to provide also x-ray beams, an e-g converter has been designed by means of the MCNP4C2 simulation code and optimized for a 10 MeV electron beam. A wide investigation has been performed to choose material and thickness for the e-g converter in order to provide the highest x-ray yield. Then, angular distribution and energy spectrum have been simulated to characterize the produced bremsstrahlung beam. Also the target activation has been investigated. Finally, thermal analysis has been performed using a finite element model code, Deform 2D, to choose the definitive mechanical settings of the e-g converter. | ||
| THP038 | Development of Laser Compton Scattering X-ray Source on the Basis of Compact Electron Linac | 2187 |
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| A compact hard 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 yields, 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. 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. | ||
| THP039 | Development of a High-power THz-TDS System on the Basis of a Compact Electron Linac | 2190 |
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| The high-power terahertz time-domain spectroscopy (THz-TDS) system has been developed on the basis of a compact S-band electron linac at AIST, Japan. The linac whose injector is a photocathode rf gun generates about a 40 MeV, 1 nC electron bunch. The bunch is compressed into less than 1ps with a magnetic compressor. It is bended by a 90-degree bending magnet, which causes generation of the THz coherent synchrotron radiation (CSR). It has useful characteristics such as high power, a short pulse and continuous spectrum. In particular, peak power of THz-CSR is estimated to be about 106 times larger than that of the conventional THz source on the basis of the mode-locked fs laser. The THz-TDS is based on the EO sampling methods with the pump-probe technique. The frequency spectrum is obtained by Fourier transform of the measured temporal THz waveform. In addition, it is applied to the ultra-short bunch length monitor by analysing the THz spectrum. In this paper, we will describe details of our system and preliminary experimental results. | ||
| THP041 | Particle Dynamics Simulation in Wobbler System for Hollow High Energy Heavy Ion Beam Formation | 2193 |
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Funding: Work supported by Rosatom contract #N.4е.45.90.10.1065 Intense heavy ion beam is an efficient tool to generate high energy density states in macroscopic amounts of matter. As result it enables to study astrophysical processes in the laboratory under controlled and reproducible conditions. For advanced experiments in high energy density physics the cylindrical target irradiated by hollow cylindrical beam is required. A new method for RF rotation of the ion beam is applied for the formation of the required hollow beam. The RF system consisting of two four-cell H-mode cavities with a resonant frequency of 297 MHz was chosen. The layout of the suggested rotating system for hollow beam formation including focusing elements is presented. The particle dynamics simulation was carried out for expecting beam parameters at ITEP Terawatt Accumulator project (ITEP TWAC). The results of simulation is considered in this paper. |
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| THP043 | High-performance Accelerators for Free-Electron Laser (FEL) and Security Applications | 2196 |
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We describe the status of two accelerators that Advanced Energy Systems has recently designed and built, and is presently commissioning. One system will drive the THz FEL at the Fritz Haber Institute of the Max Planck Society in Berlin, while the other will produce radiation for Homeland Security applications. A key aspect of the required FEL accelerator performance is low longitudinal emittance < 50 keV-psec at 200 pC bunch charge from a thermionic electron source. The other system is compact, robust and efficient since it must be transportable.
Consultants to AES |
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| THP044 | Linear Accelerator Design Study with Direct Plasma Injection Scheme for Warm Dense Matter | 2199 |
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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. Warm Dense Matter (WDM) is a growing rapidly science field, which is related to planetary science and inertial fusion. It is difficult to expect the behavior because the state with high density and low temperature is completely different from ideal condition. The well-defined WDM generation is required to understand it. Moderate energy ion beam (~ 0.3 MeV/u) slightly above Bragg peak is an advantageous method for WDM because of the uniform energy deposition. Direct Plasma Injection Scheme (DPIS) with a linear accelerator has a potential for the beam parameter. The design of linear accelerator for WDM is presented. |
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| THP045 | Proposed Facility Layout for MaRIE | 2202 |
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| The MaRIE (Matter-Radiation Interactions in Extremes) experimental facility will be used to advance materials science by providing the tools scientists need to develop materials that will perform predictably and on demand for currently unattainable lifetimes in extreme environments. The Multi-Probe Diagnostic Hall (MPDH) will create probes of matter using both photon- and proton-based diagnostics. The Fission and Fusion Materials Facility (F3) will provide capabilities for materials irradiation studies, subjecting materials to radiation extremes that are present in fission and fusion environments. The Making, Measuring, and Modeling Materials (M4) Facility will foster discovery by design of next-generation materials that will perform with better durability in extreme environments. MaRIE features a 20-GeV electron linac for an X-ray driver. Five X-ray beams will be delivered to the experimental areas. The facility will also deliver an electron beam to MPDH. The existing LANSCE proton beam will be delivered to MPDH and F3 in addition to the existing LANSCE areas. Multiple high power lasers will deliver beams to MPDH. This paper will provide an overview of the MaRIE facility layout. | ||
| THP046 | Characterization of an SRF Gun: A 3D Full Wave Simulation | 2205 |
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Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE We characterized a BNL 1.3GHz half-cell SRF gun is tested for GaAs photocathode. The gun already was simulated several years ago via two-dimensional (2D) numerical codes (i.e., Superfish and Parmela) with and without the beam. In this paper, we discuss our investigation of its characteristics using a three dimensional (3D) full-wave code (CST STUDIO SUITE™).The input/pickup couplers are sited symmetrically on the same side of the gun at an angle of 180⁰. In particular, the inner conductor of the pickup coupler is considerably shorter than that of the input coupler. We evaluated the cross-talk between the beam (trajectory) and the signal on the input coupler compared our findings with published results based on analytical models. The CST STUDIO SUITE™ also was used to predict the field within the cavity; particularly, a combination of transient/eigenmode solvers was employed to accurately construct the RF field for the particles, which also includes the effects of the couplers. Finally, we explored the beam’s dynamics with a particle in cell (PIC) simulation, validated the results and compare them with 2D code result. |
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| THP048 | Radiation and Thermal Analysis of Production Solenoid for Mu2e Experimental Setup | 2208 |
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| The Muon-to-Electron (Mu2e) experiment at Fermilab, will seek the evidence of direct muon to electron conversion that cannot be explained by the Standard Model. An 8 GeV 25 kW proton beam will be directed onto a gold target inside a large-bore superconducting Production Solenoid (PS) with the peak field on the axis of ~5T. The negative muons resulting from the pion decay will be captured in the PS aperture and directed by an S-shaped Transport Solenoid towards the stopping target inside the Detector Solenoid. In order for the superconducting magnets to operate reliably and with a sufficient safety margin, the peak neutron flux entering the coils must be reduced by 3 orders of magnitude that is achieved by means of a sophisticated absorber placed in the magnet aperture. The proposed absorber, consisting of W and Cu parts, is optimized for the performance and cost. Results of MARS15 of energy deposition and radiation analysis are reported. The results of the PS magnet thermal analysis, coordinated with the coil cooling scheme, are reported as well for the selected absorber design. | ||
| THP050 | Normal Conducting Radio Frequency X-band Deflecting Cavity Fabrication and Validation | 2211 |
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| An X-band Traveling wave Deflector mode cavity (XTD) has been developed at Radiabeam Technologies to perform longitudinal characterization of the sub-picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory, and is scalable to higher energies. The XTD is designed to operate at 11.424 GHz, and features short filling time, femtosecond resolution, and a small footprint. RF design, fabrication and RF validation and tuning will be presented. | ||
| THP051 | An Overview of Normal Conducting Radio Frequency Projects and Manufacturing Capabilities at Radiabeam Technologies, LLC | 2214 |
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| Radiabeam Technologies is currently designing, engineering and fabricating 8 different Normal Conducting Radio Frequency (NCRF) accelerating and diagnostic structures. These NCRF programs include compact X-band industrial systems, laboratory grade NCRF photoinjectors, deflecting cavities and High-Gradient structures. Nearly all aspects of these NCRF structures’ lifecycle are performed in house, including design, 3D electromagnetic and thermomechanical modeling, engineering, fabrication, cleaning and RF cold testing, tuning, and RF power testing. An overview of these varied projects along with references to more detailed publications presented in this conference are provided. Details concerning specific processes applicable to all of the above mentioned RF projects are also discussed. | ||
| THP053 | The New Approximation of Dose Attenuation Curve in Concrete | 2217 |
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| The analytical approach in shielding calculations is simple and fast method for quick estimations. But it provides less accuracy than Monte-Carlo one. Often the exponential attenuation of dose in shielding is considered. But also it is necessary to take into account the dose increase in the first layers of shielding due to initial accumulation of neutrons. The new approximation of dose attenuation curve in concrete is offered for quick analytical estimations of shielding of hadron accelerators. It allows to make fast estimation of shielding thickness enough correctly. | ||
| THP054 | Medium Energy Heavy Ion Operations at RHIC | 2220 |
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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 search for a phase transition or critical point on the QCD phase diagram, an energy scan including 5 different energy settings was performed during the 2010 RHIC heavy ion run. While the top beam energy for heavy ions is at 100 GeV/n and the lowest achieved energy setpoint was significantly below RHICs injection energy of approximately 10 GeV/n, we also provided beams for data taking in a medium energy range above injection energy and below top beam energy. This paper reviews RHIC experience and challenges for RHIC medium energy operations that produced full experimental data sets at beam energies of 31.2 GeV/n and 19.5 GeV/n. |
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| THP055 | Status of the RHIC Head-on Beam-beam Compensation Project | 2223 |
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Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. Two electron lenses are under construction for RHIC to partially compensate the head-on beam-beam effect in order to increase both the peak and average luminosity. The final design of the overall system is reported as well as the status of the component design, acquisition, and manufacturing. |
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| THP056 | Near Real-time ORM Measurements and SVD Matrix Generation for 10 Hz Global Orbit Feedback In RHIC | 2226 |
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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. To reduce the effect of trajectory perturbations due to vibrations of the final focusing quadrupoles at RHIC, global orbit feedback was successfully prototyped during run-10. The system was tested using transfer functions between the beam position monitors and correctors obtained from the online optical model and a correction algorithm based on singular value decomposition (SVD). In run-11 we plan to self-calibrate the system using SVD matrices derived from orbit response matrix (ORM) measurements acquired real-time using the new FPGA-based signal processing. Comparisons between measurement and model and of feedback performance with the two methods are presented. |
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| THP057 | Optimal Focusing for a Linac-Based Hard X-ray Source | 2229 |
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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 spite of having a small average beam current limit, a linac can have features that make it attractive as an x-ray source: high energy, ultralow emittance and energy spread, and flexible beamline optics. Unlike a storage ring, in which an (undulator) radiation source is necessarily short and positioned at a electron beam waist, in a linac the undulator can be long and the electron beam can be adjusted to have a (virtual) waist far downstream toward the x-ray target. Using a planned CEBAF beamline as an example, this paper shows that a factor of 2000 in beam current can be overcome to produce a monochromatic hard x-ray source comparable with, or even exceeding, the performance of an x-ray line at a third generation storage ring. The optimal electron beam focusing conditions for x-ray flux density and brilliance are derived, and are verified by simulations using the SRW code. |
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| THP058 | The Effects of Betatron Phase Advances on Beam-beam and its Compensation in RHIC | 2232 |
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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 this article we perform simulation studies to investigate the effects of betatron phase advances between the beam-beam interaction points on half-integer resonance driving terms, second order chromaticity and dynamic aperture in RHIC. The betatron phase advances are adjusted with artificial matrices inserted in the middle of arcs. The lattices for 2011 polarized proton (p-p) run and 2010 RHIC Au-Au runs are used in this study. We also scan the betatron phase advances between IP8 and the electron lens for the proposed Blue ring lattice with head-on beam-beam compensation. |
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| THP059 | Chromatic Analysis and Possible Local Chromatic Correction in RHIC | 2235 |
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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 this article we will answer the following questions: 1) what is the source of second order chromaticities in RHIC? 2) what is the dependence of second order chromaticity on the on-momentum β-beat? 3) what is the dependence of second order chromaticity on β* at IP6 and IP8? To answer these questions, we use the perturbation theory to numerically calculate the contributions of each quadrupole and sextupole to the first, second, and third order chromaticities. Possible methods to locally reduce chromatic effects in RHIC rings are shortly discussed. |
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| THP060 | RHIC 12x150A Current Lead Temperature Controller: Design and Implementation | 2238 |
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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 There are 60 12×150A current leads distributed in 6 RHIC service buildings; each current lead delivers power supply current from room temperature to cryogenic temperature in RHIC. Due to the humid environment, condensation frequently occurs and ice was quickly formed during operation, especially during an extensive storage period. This condition generated warnings and alarms that personal had to respond to, in order to provide temporary solutions, to keep the machine operational. A temperature control system was designed to avoid such occasions. We will discuss design, implementation and some results of this design in this paper. |
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| THP061 | Mimicking Bipolar Sextupole Power Supplies for Low-energy Operations at RHIC | 2241 |
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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. RHIC operated at energies below the nominal ion injection energy of E=9.8 GeV/u in 2010. Earlier test runs and magnet measurements indicated that all defocusing sextupole unipolar power supplies should be reversed to provide the proper sign of chromaticity. However, vertical chromaticity at E=3.85 GeV/u with this power supply configuration was still not optimal. This uncertainty inspired a new machine configuration where only half of the defocusing sextupole power supplies were reversed, taking advantage of the flexibility of the RHIC nonlinear chromaticity correction system to mimic bipolar sextupoles. This configuration resulted in a 30 percent luminosity gain and eliminated the need for further polarity changes for later 2010 low energy physics operations. Here we describe the background to this problem, operational experience, and RHIC online model changes to implement this solution. |
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| THP062 | Beam Experiments Related to the Head-on Beam-beam Compensation Project at RHIC | 2243 |
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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. Beam experiments have been performed in RHIC to determine some key parameters of the RHIC electron lenses, and to test the capability of verifying lattice modifications by beam measurements. We report the status and recent results of these experiments. |
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| THP063 | Lattice Design for Head-on Beam-Beam Compensation at RHIC | 2246 |
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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. Electron lenses for head-on beam-beam compensation will be installed in IP 10 at RHIC. Compensation of the beam-beam effect experienced at IP 8 requires betatron phase advances of ∆ψ=k·π between the proton-proton interaction point at the IP 8, and the electron lens at IP 10. This paper describes the lattice solutions for both the BLUE and the YELLOW ring to achieve this goal. |
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| THP064 | The Dipole Corrector Magnets for the RHIC Fast Global Orbit Feedback System | 2249 |
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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 recently completed RHIC fast global orbit feedback system uses 24 small “window-frame” horizontal dipole correctors. Space limitations dictated a very compact design. The magnetic design and modelling of these laminated yoke magnets is described as well as the mechanical implementation, coil winding, vacuum impregnation, etc. Test procedures to determine the field quality and frequency response are described. The results of these measurements are presented and discussed. A small fringe field from each magnet, overlapping the opposite RHIC ring, is compensated by a correction winding placed on the opposite ring’s magnet and connected in series with the main winding of the first one. Results from measurements of this compensation scheme are shown and discussed. |
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| THP065 | Advances in High-Order Interaction Region Nonlinear Optics Correction at RHIC | 2252 |
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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 method to indirectly measure and deterministically correct the higher order magnetic errors of the final focusing magnets in the Relativistic Heavy Ion Collider has been in place for several years at BNL. This method yields control over the effects of multi-pole errors through application of closed orbit bumps followed by analysis and correction of the resulting betatron tune shifts using multi-pole correctors. The process has recently been automated in order to provide more efficient and effective corrections. The tune resolution along with the reliability of tune measurements has also been improved significantly due to advances/upgrades in the betatron tune measurement system employed at RHIC (BBQ). Here we describe the foundation of the IR bump method, followed by recent improvements along with experimental data. |
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| THP067 | Ambient Beam Motion and its Excitation by "Ghost Lines" in the Tevatron | 2255 |
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| Transverse betatron motion of the Tevatron proton beam is measured and analyzed. It is shown that the motion is coherent and excited by external sources of unknown origins. Observations of the time-varying "ghost lines" in the betatron spectrum are reported. | ||
| THP068 | Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC | 2258 |
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Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and was partially supported by the DOE through the US LHC Accelerator Research Program (LARP). A compact 400-MHz half-wave spoke resonator (HWSR) superconducting crab cavity is being developed for the LHC upgrade. The cavity shape and the LOM/HOM couplers for such a design have been optimized to meet the space and beam dynamics requirements, and satisfactory RF parameters have been obtained. As it is known that multipacting is an issue of concern in a superconducting cavity which may limit the achievable gradient. Thus it is important in the cavity RF design to eliminate the potential MP conditions to save time and cost of cavity development. In this paper, we present the multipacting analysis for the HWSR crab cavity using the Track3P code developed at SLAC, and to discuss means to mitigate potential multipacting barriers. |
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| THP069 | Vibration Budget for SuperB | 2261 |
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Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515. We present a vibration budget for the SuperB accelerator. This includes ground motion data, motion sensitivity of machine components, and beam feedback system requirements. |
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| THP071 | Interaction Region Design of Super-CT-Factory in Novosibirsk | 2264 |
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| The interaction region of the Super-CT-factory is designed to bring stored electron-positron beams into collision with luminosity of 1035 cm-2sec-1. To achieve this a waist collision scheme is implemented, which requires cross-angle collision with high Piwinski angle. The small values of the beta functions at the interaction point and distant final focus lenses are the reasons for high nonlinear chromaticity limiting energy acceptance of the whole ring. The present design allows correction of linear and nonlinear chromaticity of beta functions and of betatron tune advances, correction of second and third order geometrical aberrations from the strong sextupoles pairs, satisfies geometrical constraints, embraces realistic design of final focus quadrupoles and as close as possible positioning of crab sextupole to interaction point. | ||
| THP072 | Compensation of Detector Solenoid in SUPER-B | 2267 |
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Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. The SUPER-B detector solenoid has a strong 1.5 T field in the Interaction Region (IR) area, and its tails extend over the range of several meters. The main effect of the solenoid field is the coupling of the horizontal and vertical betatron motion which needs to be corrected in order to preserve the small design beam size at the Interaction Point. The additional complications are that: a) due to the crossing angle the solenoid is not parallel to either of the two beams, thus leading to orbit and dispersion perturbations; b) the solenoid overlaps the innermost IR permanent quadrupoles, which will cause additional coupling effects. The proposed correction system provides local compensation of the solenoid effects independently for each side of the IR. It includes “bucking” solenoids to remove the unwanted long solenoid field tails and a set of skew quadrupoles, dipole correctors and anti-solenoids to cancel all linear perturbations to the optics. The details of the correction system design are presented. |
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| THP073 | Simulations of Emittance Measurement at CLIC | 2270 |
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| A proposal for a CLIC emittance measurement line using laser-wire beam profile monitors is presented. Results of simulations and optimizations are given. Estimates of the impact of beam size as well as statistical and machine-related errors on the measurement accuracy are discussed. | ||
| THP076 | Combined Target-collection System for Positron Production in ILC | 2273 |
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Funding: NSF We describe the positron collection system with Lithium lens, while one of the flanges of this lens made on Tungsten, which serves as a target for the photons radiated in a helical undulator by high-energy ILC beam. |
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| THP077 | SC Quadrupole for Cryomodule for ERL/ILC | 2276 |
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Funding: NSF We are considering the SC quadrupole where the field formed not only by the current distributions, but with the poles also. This delivers a good quality field in all aperture allowing compact and inexpensive design. This type of quadrupole designed for Cornell ERL could be recommended for ILC also. |
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| THP078 | Study of a TeV Level Linear Collider Using Short rf Pulse (~20ns) Two Beam Accelerator Concept | 2279 |
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Funding: Work is supported by DOE SBIR grant under contract No. DE-SC0004320. In a general sense, a high gradient is desirable for a TeV level linear collider design because it can reduce the total linac length. More importantly, the efficiency and the cost to sustain such a gradient should be considered as well in the optimization process of an overall design. We propose a high energy linear collider based on a short rf pulse (~22ns flat top), high gradient (~267MV/m loaded gradient), high frequency (26GHz) dielectric two beam accelerator scheme. This scheme is a modular design and its unique locally repetitive drive beam structure allows a flexible configuration to meet different needs. Major parameters of a conceptual 3-TeV linear collider are presented. This preliminary study shows an efficient (~7% overall ) short pulse collider may be achievable. As the first step, a dielectric based broadband accelerating structure is under development. |
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| THP079 | Recent RHIC-motivated Polarized Proton Developments in the Brookhaven AGS | 2282 |
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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 polarized proton physics program requires high luminosity and high polarization which depends directly on the intensity, emittances and polarization delivered to RHIC by the injector chain. In the AGS, two partial snakes create gaps in the realized spin-tune around the integers which allows an accelerating beam with sufficiently small vertical emittance and near-integer vertical tune to avoid the imperfection and vertical intrinsic resonances. The same strategy strengthens the many (82) weak horizontal intrinsic resonances crossed during AGS acceleration. A system speeding up these resonance crossings – the AGS JumpQuad system: 82 tiny (0.04) fast (100usec) betatron tune shifts – has been commissioned and evolved during RHIC Runs 09, 10, and 11. Subtle properties of the AGS geometry and lattice, magnified into relevance by the high vertical tune can result in polarization-damaging emittance growth when combined with the Jump Quad gymnastics. Orbit stability is critical. Some aspects of the JumpQuad system, of this commissioning effort and related developments will be described. |
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| THP081 | Beam Lifetime and Limitations during Low-Energy RHIC Operation | 2285 |
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Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States. The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam γ=6.1 and γ=4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings. |
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| THP082 | Design Aspects of an Electrostatic Electron Cooler for Low-energy RHIC Operation | 2288 |
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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. Electron cooling was proposed to increase the luminosity of RHIC operation for heavy ion beam energies below 10 GeV/nucleon. The electron cooling system needed should be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (0.9-5 MeV). An option of using an electrostatic accelerator for cooling heavy ions in RHIC was studied in detail. In this paper, we describe the requirements and options to be considered in the design of such a cooler for RHIC, as well as the associated challenges. The expected luminosity improvement and limitations with such electron cooling system are also discussed. |
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| THP083 | Fabrication and Design of the Main Linacs for CLIC with Damped and Detuned Wakefield Suppression and Optimised Surface Electromagnetic Fields | 2291 |
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Funding: Research leading to these results has received funding from the European commission under the FP7 research infrastructure grant no. 227579. We report on the suppression of long-range wakefields in the main linacs of the CLIC collider. This structure operates with a 120 degree phase advance per cell. The wakefield is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. This serves as an alternative to the present baseline CLIC design which relies on heavy damping. Detailed simulations of both the optimised surface fields resulting from the monopole mode, and from wakefield damping of the dipole modes, are discussed. We report on fabrication details of a structure consisting of 24 cells, diffusion bonded together. This design, known as CLICDDSA, takes into practical mechanical engineering issues and is the result of several optimisations since the earlier CLICDDS designs. This structure is due to be tested for its capacity to sustain high gradients at CERN. |
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| THP085 | Radiation Effects in a Muon Collider Ring and Dipole Magnet Protection | 2294 |
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Funding: Work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. Requirements and operating conditions for a Muon Collider Ring (MCR) pose significant challenges to superconducting magnets. The dipole magnets should provide a high magnetic field to reduce the ring circumference and thus maximize the number of muon collisions during their lifetime. One third of the beam energy is continuously deposited along the lattice by the decay electrons at the rate of 0.5 kW/m for a 1.5-TeV c.o.m. MCR. Unlike dipoles in proton machines, the MCR dipoles should allow this dynamic heat load to escape the magnet helium volume in horizontal plane predominantly towards the ring center. Two alternative designs, one based on the open mid-plane approach with block type coils and absorber outside the coils, and another based on the traditional large-aperture cos-theta approach with a shifted beam pipe and absorber inside the coil aperture were developed for the MCR designed for a luminosity of 1034 cm-2s−1. This paper presents the analysis and comparison of radiation effects in MCR based on the two dipole magnets. Tungsten masks in the interconnect regions are used in both cases to mitigate the unprecedented dynamic heat deposition and radiation in the magnet coils. |
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| THP087 | G4Beamline and MARS Comparison for Muon Collider Backgrounds | 2297 |
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Funding: Supported in part by SBIR Grant DE-SC0005447 Technological innovations in recent years have revived interest in muon colliders as the next generation energy frontier machine. The biggest challenge for muon colliders is that muons decay. Advances in muon cooling technology will make the focussing and acceleration of muons to TeV energies possible. The challenge for the detectors in such machines is overcoming the large backgrounds from muon decays in the colliding ring lattice that will inundate the interaction region (IR) and will make triggering and data reconstruction a challenge. Developing simulation tools that can reliably model the environment of the muon collider IR will be critical to physics analyses. We will need to expand the capabilities of current programs and use them to benchmark and verify results against each other. Here we are comparing an emerging capabiligy of G4beamline, an interface for physicists to GEANT4 code, with MARS, a mature program for particle fluences, in developing code for muon collider background studies |
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| THP088 | Beam Induced Detector Backgrounds at a Muon Collider | 2300 |
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Funding: Supported in part by SBIR Grant DE-SC0005447 Muon colliders are considered to be an important future energy frontier accelerator. It is possible to build a large muon collider as a circular machine, even at multi-TeV energies, due to the greatly reduced synchrotron radiation expected from muons. In addition to the same physics processes present in an electron collider, a muon collider will have the potential to produce s-channel resonances such as the various Higgs states at an enhanced rate. For a muon collider with 750 GeV/c mu+ and mu- with 1012 mu per bunch we would expect 4.3x105 muon decays per meter. These muon decays will produce very energetic off momentum electrons that can produce detector backgrounds that can affect the physics. These backgrounds include electrons from muon decays, synchrotron radiation from the decay electrons, hadrons produced by photo-nuclear interactions, coherent and incoherent beam-beam pair production and Bethe-Heitler muon production. In this paper we will discuss these processes and calculate particle fluxes into the detector volume from these background processes. |
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| THP090 | Physics Validation of Monte Carlo Simulations for Detector Backgrounds at a Muon Collider | 2303 |
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| Muon colliders are considered to be an important future energy-frontier accelerator. A muon collider could be built as a circular accelerator into the TeV energy range as a result of the reduced synchrotron radiation expected from the larger rest mass of muons. For a muon collider with 750 GeV μ+ and μ- with 1012 μ per bunch, it can be expected that there would be 4.3×105 muon decays per meter per beam. These decays will produce very energetic off-momentum electrons that can produce detector backgrounds that can affect the physics. The main backgrounds include electrons from muon decays, synchrotron radiation from the decay electrons, hadrons produced by photonuclear interactions, coherent and incoherent beam-beam pair-production, and Bethe-Heitler muon production. In this paper we will discuss the simulation results in terms of observed physics processes in G4Beamline. | ||
| THP093 | Design Status of MEIC at JLab | 2306 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. An electron-ion collider (MEIC) is envisioned as the primary future of the JLab nuclear science program beyond the 12 GeV upgraded CEBAF. The present MEIC design selects a ring-ring collider option and covers a CM energy range up to 51 GeV for both polarized light ions and un-polarized heavy ions, while higher CM energies could be reached by a future upgrade. The MEIC stored colliding ion beams, which will be generated, accumulated and accelerated in a green field ion complex, are designed to match the stored electron beam injected at full energy from the CEBAF in terms of emittance, bunch length, charge and repetition frequency. This design strategy ensures a high luminosity above 1034 s−1cm-2. A unique figure-8 shape collider ring is adopted for advantages of preserving ion polarization during acceleration and accommodation of a polarized deuteron beam for collisions. Our recent effort has been focused on completing this conceptual design as well as design optimization of major components. Significant progress has also been made in accelerator R&D including chromatic correction and dynamical aperture, beam-beam, high energy electron cooling and polarization tracking. |
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| THP100 | Structure and Design of the Electron Lens for RHIC | 2309 |
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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. Two electron lenses for a head-on beam-beam compensation are being planned for RHIC; one for each circulating proton beam. The transverse profile of the electron beam will be Gaussian up to a maximum radius of re=3σ. Simulations and design of the electron gun with Gaussian radial emission current density profile and of the electron collector are presented. Ions of the residual gas generated in the interaction region by electron and proton beams will be removed by an axial gradient of the electric field towards the electron collector. A method of optical observation the transverse profile of the electron beam is described. |
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| THP101 | The MERLIN Simulation Program: New Features used in Studies of the LHC Collimation System using MERLIN | 2312 |
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| We present recent developments in the MERLIN particle tracking simulation code, originally developed at DESY. Their use is illustrated by studies of the LHC collimation system. We make detailed comparisons of our results with those of other codes, and also, where possible, with the data. Different beam optics designs are studied, and the effect of new collimator materials for different upgrade scenarios is predicted. | ||
| THP102 | Simulation Studies of Accelerating Polarized Light Ions at RHIC and AGS | 2315 |
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Funding: This work was supported by the Department of Energy of U.S.A As the worlds’s first high energy polarized proton col- lider, RHIC has made significant progresses in measuring the proton spin structure in the past decade. In order to have better understanding of the contribution of u quark and d quark to the proton spin structure, collisions of high energy polarized neutron beams are required. In this paper, we discuss the perspectives of accelerating polarized light ions, like deuteron, Helium-3 and tritium. We also repre- sent simulation studies of accelerating polarized Helium-3 in RHIC. Brookhaven National Lab., Upton, NY 11973 |
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| THP103 | Spin Code Benchmarking at RHIC | 2318 |
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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. Stepwise ray-tracing methods are being developed at C-AD, BNL, in view of benchmarking of existing spin codes and of spin dynamics simulations at RHIC. A status of that work is reported here. |
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| THP105 | Final Design of ILC RTML Extraction Line for Single Stage Bunch Compressor | 2321 |
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| The use of single stage bunch compressor (BC) in the International Linear Collider (ILC) [1] Damping Ring to the Main Linac beamline (RTML) requires new design for the extraction line (EL). The EL located downstream of the BC will be used for both an emergency abort dumping of the beam and the tune-up continuous train-by-train extraction. It must accept both compressed and uncompressed beam with energy spread of 3.54% and 0.15% respectively. In this paper we report the final design that allowed minimizing the length of such extraction line while offsetting the beam dumps from the main line by 5m distance required for acceptable radiation level in the service tunnel. Proposed extraction line can accommodate beams with different energy spreads at the same time providing the beam size suitable for the aluminum ball dump window. | ||
| THP107 | Source of Microbunching at BNL NSLS Source Development Laboratory | 2324 |
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| We report experimental studies of the origins of electron beam microbunching instability at BNL Source Development Laboratory (SDL). We eliminated laser-induced microbunching by utilizing an ultra-short photocathode laser. The measurements of the resulting electron beam led us to conclude that, at SDL, microbunching arising from shot noise is not amplified to any significant level. Our results demonstrated that the only source of microbunching instability at SDL is the longitudinal modulation of the photocathode laser pulse. Our work shows that assuring a longitudinally smoothed photocathode laser pulse allows mitigating microbunching instability at a typical FEL injector with a moderate microbunching gain. | ||
| THP108 | Analysis of RHIC Beam Dump Pre-fires | 2327 |
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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. It has been speculated that the beam may cause instability of the RHIC Beam Abort Kickers. In this study, we explore the available data of past beam operations, the device history of key modulator components, and the radiation patterns to examine the correlations. |
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| THP109 | Dielectric Collimators for Linear Collider Beam Delivery System | 2330 |
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Funding: US Department of Energy The current status of ILC and CLIC concepts require additional research on wakefield reduction in the collimator sections. New materials and new geometries have been considered recently*. Dielectric collimators for the CLIC Beam Delivery System have been discussed with a view to minimize the BDS collimation wakefields**. Dielectric collimator concepts for the linear collider are presented in this paper; cylindrical and planar collimators for the CLIC parameters have been considered, and simulations to minimize the beam impedance have been performed. The prototype collimator system is planned to be fabricated and experimentally tested at Facilities for Accelerator Science and Experimental Test Beams (FACET) at SLAC. *J.R.Lopez. ILC-CLIC Beam Dynamics Workshop. CERN, Geneva, 23-25 June, 2009. **R. Tomas. ILC-CLIC Beam Dynamics Workshop. CERN, Geneva, 23-25 June, 2009. |
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| THP110 | Front End Energy Deposition and Collimation Studies for IDS-NF | 2333 |
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Funding: Work supported by DOE, STFC. The function of the Neutrino Factory front end is to reduce the energy spread and size of the muon beam to a manageable level that will allow reasonable throughput to subsequent system components. Since the Neutrino Factory is a tertiary machine (protons to pions to muons), there is an issue of large background from the pion-producing target. The implications of energy deposition in the front end lattice for the Neutrino Factory are addressed. Several approaches to mitigating the effect are proposed and discussed, including proton absorbers, chicanes, beam collimation, and shielding. |
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| THP114 | Status of the PEP-X Light Source Design Study | 2336 |
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Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences. The SLAC Beam Physics group and collaborators continue to study options for implementing a near diffraction-limited ring-based light source in the 2.2-km PEP-II tunnel that will serve the SSRL scientific program in the future. The study team has completed the baseline design for a 4.5-GeV storage ring having 160-pm-rad emittance with stored beam current of 1.5 A, providing >1022 brightness for multi-keV photon beams from 3.5-m undulator sources. The team is now investigating possible 5-GeV ERL configurations which, similar to the Cornell and KEK ERL plans, would have ~30 pm-rad emittance with 100 mA current, and ~10 pm-rad emittance with 25 mA or less. In the next year, a diffraction-limited storage ring using on-axis injection in order to reach 30 pm-rad or less emittance will be investigated. An overview of the PEP-X design study and SSRL’s plans for defining the performance parameters that will guide the choice of implementation options is presented. |
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| THP119 | Potential Two-fold Reduction of Advanced Photon Source Emittance using Orbit Displacement | 2339 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) is a 7-GeV electron storage ring light source that operates with an effective emittance of 3.1 nm using optics with distributed dispersion. Lower emittance is desirable for some x-ray experiments, but is difficult using conventional optics adjustments because of the required strength of quadrupoles and sextupoles. Changing the damping partition number by changing the rf frequency is another approach, but is incompatible with distributed dispersion because it would require simultaneous realignment of all APS beamlines. In this paper, we evaluate a new approach to changing the damping partition number using a systematic orbit bump in all sectors. |
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| THP120 | Light Sources Optimized with Super Bends | 2342 |
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Funding: Work at Argonne was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357 In the past small storage rings with dipole-magnet-only sources were called second-generation light sources (before insertion devices (IDs) were used). With today's technology, e.g. superconducting dipole magnet of 5 T (e.g., ALS's Superbend *), one could make a smaller ring (say, 60-m circumference) with substantial brightness for dipole-magnet beams. Without IDs, these optimized sources would be designated as between second and third generation. Such rings don't exist yet, but their concept can be compared with other types of compact light sources. Typical parameters of such ring would be 60-m circumference, 2 GeV, several 5-T dipole sources in TME-like cells, and 4x1013 photons/s/0.1% BW at 1 Angstrom. The number of beamlines is variable, but potentially very large, only limited by funding. * D. Robin et al., NIM A 538, 1-3, (2005), 65-92. |
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| THP121 | Open-source Software System for Multi-author Documents | 2345 |
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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 An efficient means was developed to manage multi-author documents using software components not usually run together that are both freely available and free of cost: Concurrent Version Software (CVS), LaTeX typesetting software, and the Unix make utility. Together they solve the main problem with multi-author documents: losing track of "latest" version, tracking author contributions, and a strict enforcement of document format. APS has used this system for two large documents with about a dozen authors each: a 2007 white paper (150 pages) on a ERL proposal and a chapter (200 pages) of the APS Upgrade CDR. We stress the use of LaTeX because the plain-text format is amenable to version comparisons and the macro-based system allows last-minute global format changes. Several contributions from APS to this conference actually use this system. |
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| THP122 | Comparison of Chirp Schemes for Short-Pulse X-ray Beams in Light Sources | 2348 |
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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. The Advanced Photon Source is planning [*] to produce a short-pulse x-ray beam by way of rf deflecting cavities that locally impose a y'-t correlation on the stored beam at an insertion device. SPring-8 recently proposed [**] a variation on this scheme whereby the deflecting cavities impose a local y-t correlation on the stored beam. In one case the chirp is in the angle coordinate and in the other case the position coordinate. They both use slits to pass through a "short" portion of the photon beam. The practical limitations for the two schemes are discussed and compared, such as photon source size and angular divergence, storage ring apertures, and slit transmission. * A. Nassiri et al., these proceedings ** T. Fujita et al., Proc. of IPAC10, p. 39 |
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| THP124 | Higher Current Operation for the APS Upgrade | 2351 |
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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. The Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. Operation for users is delivered at a nominal current of 100 mA in one of three bunch patterns. The APS Upgrade calls for a minimum planned operating current of 150 mA, with an option to deliver beam up to 200 mA. The high-current threshold in the storage ring has been explored, and storage ring components have been identified that either drive collective instabilities or are subjected to excessive beam-drive higher-order-mode (HOM) heating. In this paper, we describe machine studies at 150 mA in a special lattice that simulates the upgraded APS. We also describe the accelerator upgrades that are required to accommodate 200-mA operation, as well as the ongoing machine studies plan. |
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| THP125 | Multi-objective Optimization of a Lattice for Potential Upgrade of the Advanced Photon Source* | 2354 |
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Funding: *Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. In the near future, the ring may be upgraded, including changes to the lattice such as provision of several long straight sections (LSSs). Use of deflecting cavities for generation of short x-ray pulses is also considered. Because APS beamlines are nearly fully built out, we have limited freedom to place LSSs in a symmetric fashion. Arbitrarily placed LSSs will drastically reduce the symmetry of the optics and would typically be considered unworkable. We apply a recently developed multi-objective direct optimization technique that relies on particle tracking to compute the dynamic aperture and Touschek lifetime. We show that this technique is able to tune sextupole strengths and select the working point in such a way as to recover the dynamic and momentum acceptances. We also show the results of experimental tests of lattices developed using these techniques. |
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| THP126 | Obtaining Sub-Picosecond X-Ray Pulses in the Advanced Photon Source Using Laser Slicing | 2357 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The laser slicing technique* has been successfully applied at several low- to medium-energy storage ring light sources to create sub-picosecond pulses of x-rays. Application to high-energy storage rings has been considered problematic because of the required average laser power. However, because of on going advances in laser technology, this technique is now within reach at light sources like the Advanced Photon Source (APS), which operates at 7 GeV. In this paper, we analyze the potential performance of laser slicing at the APS, and compare it to alternatives such as deflecting cavities. * R. W. Schoenlien et al., Science, 287, 2237(2000). |
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| THP127 | Analysis of NSLS-II Touschek Lifetime | 2360 |
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Funding: Work supported by DOE contract DE-AC02-98CH10886 As scrapers are adopted for the loss control of NSLS-II storage ring, Touschek lifetime estimations for various cases are required to assure the stable operation. However, to estimate the Touschek lifetime, momentum apertures should be measured all along the ring and, if we want to estimate the lifetime in various situations, it can take extremely long time. Thus, rather than simulating for each case, semi-analytic methods with the interpolations are used for the measurements of the momentum apertures. In this paper, we described the methods and showed the results. |
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| THP129 | Emittance Reduction Approaches for NSLS-II | 2363 |
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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 NSLS-II is a third generation light source that is under construction at the Brookhaven National Laboartory. The 3GeV 792m long 30-cell storage ring will be commissioned in 2014. The emittance is lowered from 2nm to 1nm by three 7m damping wigglers. This paper will discuss the future emittance reduction approaches for NSLS-II. One option is installing more damping wigglers; an alternative solution is to manipulate the damping partition by shifting the chromatic quadrupoles horizontally. Both methods can lower the emittance effectively; however, the second method does not occupy the user straights. When the quarupoles are moved, the orbit and thus the vacuum chamber need to be redesigned, and beam dynamics could be affected. In the paper we will compare the lattice properties for the two options, and address the potential issues. |
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| THP131 | Injection Straight Pulsed Magnet Error Tolerance Study for Top-off Injection | 2366 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 NSLS II is designed to work in top-off injection mode. The goal is to minimize the disturbance of the injection transient on the users. The injection straight includes a septum and four fast kicker magnets. The pulsed magnet errors will excite a betatron oscillation. This paper gives the formulas of each error contribution to the oscillation amplitude at various source points in the ring. These are compared with simulation results. Based on the simple formulas, we can specify the error tolerances on the pulsed magnets and scale it to similar machines. |
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| THP132 | Beam Diagnostics using BPM Signals from Injected and Stored Beams in a Storage Ring | 2369 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 Many modern light sources are operating in top-off injection mode or are being upgraded to top-off injection mode. For top-off injection mode, the storage ring always has the stored beam and injected beam. So the BPM data is the mixture of both beam positions and the injected beam position cannot be measured directly. We propose to use a BPM with special electronics in NSLS II storage ring to retrieve the injected beam trajectory with the SVD method. The BPM has the capability to measure bunch-by-bunch beam position. We also need another system to measure the bunch-by-bunch beam current. The injected beam trajectory can be measured and monitored all the time without dumping the stored beam. We can adjust and optimize the injected beam trajectory to maximize the injection efficiency. We can also measure the storage ring acceptance by mapping the injected beam trajectory. |
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| THP133 | Modulation of Low Energy Beam to Generate Predefined Bunch Trains for the NSLS-II Top-off Injection | 2372 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 The NSLS II linac will produce a bunch train, 80-150 bunches long with 2 ns bunch spacing. Having the ability to tailor the bunch train can lead to the smaller bunch to bunch charge variation in the storage ring. A stripline is integrated into the linac baseline to achieve this tailoring. The stripline must have a fast field rise and fall time to tailor each bunch. The beam dynamics is minimally affected by including the extra space for the stripline. This paper discusses the linac beam dynamics with stripline, and the optimal design of the stripline. |
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| THP134 | Lifetime Measurement with Pseudo Moveable Septum in NSLS X-ray Ring | 2375 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory and starts to commission in 2014. The beam injection works with two septa and four fast kicker magnets in an injection section. To improve the injection stability and reproducibility, we plan to implement a slow local bump on top of the fast bump so that the fast kicker strength is reduced. This bump works as a pseudo movable septum. We can also use this ‘movable’ septum to measure the storage ring beam partial lifetime resulting from the septum edge and possibly increasing the lifetime by moving the stored beam orbit away from the edge. We demonstrate the feasibility of this idea, by implementing DC bump in NSLS X-ray ring. We report the results of beam lifetime measurements as a function of the amplitude of this bumped orbit relative to the septum and the idea of a slow bump that could reduce the fast bump magnet strengths. |
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| THP135 | Implementation of a DC Bump at the Storage Ring Injection Straight Section | 2378 |
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Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886 The NSLS II beam injection works with two septa and four fast kicker magnets. The kicker power supplies each produce a two revolution periods pulsed field, 5.2μs half sine waveform, using ~5kV drive voltage. The corresponding close orbit bump amplitude is ~15mm. It is desired that the bump they produce is transparent to the users for top-off injection. However, high voltage and short pulse power supplies have challenges to maintain pulse-to-pulse stability and magnet-to-magnet reproducibility. To minimize these issues, we propose to implement a DC local bump on top of the fast bump to reduce the fast kicker strength by a factor of 2/3. This bump uses two ring corrector magnets plus one additional magnet at the septum to create a bump. Additionally, these magnets could provide a DC bump, which would simulate the effects of a movable septum on the store beam lifetime. This paper presents the detail design of this DC injection bump and related beam dynamics. |
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| THP136 | Short Pulse Generation by Laser Slicing at NSLSII | 2381 |
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Funding: Work supported by DOE contract DE-AC02-98CH10886. We propose an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. In this paper we discuss the basic parameters for this system and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring. |
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| THP140 | Synchrotron Light Options at Super-B | 2384 |
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| The Super-B facility will collide electron and positron beams with different characteristics as done in the past at PEP-II and KEKB. The ring and electron (positron) beam characteristic of both high and low energy rings of the Super-B are comparable to NSLS-II and other state of the art synchrotron light sources. This suggests the use of this facility, either parasitically or in dedicated runs, as light source. In this paper we compare the characteristics of the synchrotron light generated at Super-B with existing, in construction and proposed facilities. We investigate different schemes to incorporate the generation of synchrotron radiation in the collider lattice design and look at different beam line layouts for users. | ||
| THP141 | On the Problem of Threshold Characteristics for FELWI | 2387 |
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Funding: ISTC A-1602 For a free-electron laser without inversion (FELWI), es- timates of the threshold laser power are found. The large- amplification regime should be used to bring an FELWI above the threshold laser power. |
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| THP144 | FELs as X-ray Sources in ERL Facilities | 2390 |
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Funding: This work has been supported by NSF award DMR-0807731. Hard x-ray Energy Recovery Linacs (ERLs) operate with high-brightness electron beams, matching the requirements for X-ray FELs in terms of emittance and energy spread. We have analyzed in how far it is feasible to include X-ray FELs in ERL facilities. X-ray FEL Oscillators require comparatively low peak currents and are therefore good candidates for FEL sources in ERLs. However, also high-gain FELs do not seem out of reach when bunch-compression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, different FEL concepts are discussed and their suitability as X-ray sources are analyzed. |
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| THP146 | Preliminary Study of Terahertz Free-Electron Laser Oscillator Based on Electrostatic Accelerator | 2393 |
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| Since the terahertz radiation sources provide wide applications in medical, industrial and material science, a compact, wavelength tunable and high-power THz source attracted much attention in many laboratories. In this paper, we give a primary study of a compact THz FEL based on electrostatic accelerator and the choice of basic design parameters is presented. The feasibility study is carried out using FELO codes. It is proved that FEL utilizing electrostatic accelerators (EA-FEL) will be a promising compact and powerful terahertz source. | ||
| THP148 | Experimental Investigation of Superradiance in a Tapered Free-Electron Laser Amplifier | 2396 |
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We report experimental studies of the effect of undulator tapering on superradiance in a single-pass high- gain free-electron laser (FEL) amplifier. The experiments were performed at the Source Development Laboratory (SDL) of National Synchrotron Light Source (NSLS). Efficiency was nearly tripled with tapering. Both the temporal and spectral properties of the superradiant FEL along the uniform and tapered undulator were experimentally characterized using frequency-resolved optical gating (FROG) images. Numerical studies predicted pulse broadening and spectral cleaning by undulator tapering Pulse broadening was experimentally verified. However, spectral cleanliness degraded with tapering.
* T. Watanabe et al, Phys. Rev. Lett. 98, 034802 (2007). ** X.J. Wang et al, Phys. Rev. Lett. 103, 154801 (2009). |
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| THP149 | Amplification of Current Density Modulation in a FEL with an Infinite Electron beam | 2399 |
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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. We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with a kappa-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain. |
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| THP152 | Calibration of Spectrometers with Undulator Radiation | 2402 |
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Funding: This work is supported in part by the U.S. Department of Energy, Office of Nuclear Physics under grant number DE-FG02-97ER41033 A well-calibrated spectrometer is critical for measuring the real spectra of spontaneous radiation of an electron beam in undulators (i.e. undulator radiation), which is important for FEL research. A calibration method of spectrometers based upon the known undulator radiation spectrum has been developed at Duke FEL Laboratory (DFELL). It has been used to provide a precise calibration for spectrometers from infrared (IR) to ultraviolet (UV). This calibration method is expected to be useful for the calibration of spectrometers working in the extreme ultraviolet (EUV) and X-ray region. In this work, we present the details of the calibration method and illustrate the usefulness of the method using a portable spectrometer in the visible region as an example. |
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| THP153 | Manipulating the FEL gain process with an In-cavity Aperture System | 2405 |
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Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. The 53.73 meters long free-electron laser (FEL) resonator at Duke University consists of two concave mirrors with the similar radius of curvature. The downstream mirror receives not only the fundamental but also higher order harmonic radiation (typically in the UV and VUV range) emitted by relativistic electrons in the magnetic field of wigglers. The power load of wiggler radiation on this mirror can thermally deform and permanently damage the multi-layer coating of the mirror, therefore, limiting the maximum power of the FEL operation and reducing the mirror lifetime. To mitigate these problems, a water-cooled aperture system has been installed inside the FEL resonator. This aperture system has been used to prevent most of off-axis helical wiggler radiation from reaching the downstream FEL mirror. It has also been used to manipulate the FEL gain process by increasing the FEL beam diffraction loss inside the resonator. In principle, this aperture system can be used as an independent FEL gain control device for FEL operation. This paper reports our preliminary study of the FEL operation using the in-cavity apertures to manipulate the FEL gain process. |
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| THP155 | Experience of FEL Mirror Degradation at the Duke FEL and HIGS Facility | 2408 |
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Funding: This work is supported by the US DoE grant #DE-FG02-97ER41033 The Duke FEL and High Intensity Gamma-ray Source (HIγS) are operated in the range of electron beam energies of 0.24 - 1.2 GeV and photon beam wavelengths of 190-1060 nm. The range of gamma-beam energies currently produced by HIγS facility is from 1MeV to about 100 MeV, with the maximum total gamma-flux of up to 3*1010 gammas per second around 10 MeV. Production of this high level gamma-ray flux requires an average FEL photon beam power inside the FEL resonator at one kilowatt or more. The high power FEL operation causes degradation of the FEL mirrors, especially when operating the FEL in the UV and VUV region at a high electron beam energy. To ensure reliable HIγS operation, we developed a comprehensive program to continuously monitor the performance of the FEL mirrors. This program enabled us to use a particular set of FEL mirrors for a few hundreds hours of high gamma-flux operation with predictable performance. In this work, we discuss sources and consequences of the mirror degradation for a variety of wavelengths. We also present estimates of the mirror life time as a function of the FEL wavelength, photon and gamma-ray polarization, and total gamma-flux. |
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| THP156 | Converting CESR into a Frontier Hard X-ray Light Source | 2411 |
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Funding: NSF, DMR-0936384 The relatively large horizontal emittance εx of CESR, an electron storage ring designed for colliding beam operation, does not limit its performance after its conversion into a frontier x-ray source, CESR-X. Its flexible lattice optics permits the production of hard x-ray beams competitive with any in the world by exploiting the fact that the conditions required for Liouville’s theorem to be valid are applicable to charged particle focusing but not to x-ray focusing. X-ray focusing (with currently available devices) causes an increase in electron beam “effective” emittance that would prevent even a fourth generation source, such as an ERL, from outperforming the existing CESR-X ring as a source of hard x-rays. As x-ray focusing devices are improved this will become less true and it will be important for CESR-X to keep pace. A plan for doing this is described. |
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| THP162 | Design Studies of Coherent Prebunching and Emittance Reduction for the MaRIE XFEL | 2414 |
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Funding: Supported by US Department of Energy Grant LDRD 20110067DR. There are several schemes currently being investigated which use modulator and dispersive sections to step the coherent bunching of the electron beam up to higher harmonics. X-ray FELs generally operate in a regime where the FEL parameter ρ is equal to or less than the effective energy spread introduced from the emittance in the electron beam. Because of this large effective energy spread, the energy modulation introduced from harmonic generation schemes would seriously degrade FEL performance. This problem can be mitigated by incorporating the harmonic generation scheme at an electron kinetic energy lower than the energy at the final undulator. This will help because the effective energy spread from emittance is reduced at lower energies, and can be further reduced by making the beam transversely large. Then the beam can be squeezed down slowly enough in the subsequent accelerator sections so that geometric debunching is avoided. Here we show analytical results that demonstrate the feasibility of this harmonic pre-bunching scheme. |
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| THP163 | Pre-Conceptual Design Requirements for an X-Ray Free Electron Laser for the MaRIE Experimental Facility at LANL | 2417 |
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Funding: Work performed under the auspices of the U.S. Department of Energy, under contract DE-AC52-06NA25396. The MaRIE (Matter-Radiation Interactions in Extremes) experimental facility will be used to advance materials science by providing the tools scientists need to develop materials that will perform predictably and on demand for currently unattainable lifetimes in extreme environments. The MaRIE facilities, the Multi-Probe Diagnostic Hall (MPDH), the Fission and Fusion Materials Facility (F3), and the Making, Measuring, and Modeling Materials (M4) Facility will each have experimental needs for one or more high-energy X-ray beam probes. MPDH will also require access to an electron beam probe. These probe beams can be created using a 20-GeV electron linac, both to serve as a source of electrons and as a driver for a set of up to five X-ray undulators for the high-energy X-rays. Because of space considerations at the facility, a high-gradient design is being investigated that will use a normal-conducting linac and X-band RF systems. Experimental requirements are also calling for relatively long pulse lengths, as well as interleaving high- and low-charge electron bunches. This paper will provide an overview of how an XFEL would address the scientific requirements for MaRIE. |
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| THP164 | Orbital Angular Momentum Light Generated via FEL at NLCTA | 2420 |
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| A scheme to create coherent light with orbital angular momentum (OAM) using Free Electron Laser (FEL) at NLCTA is proposed. An 795 nm light co-propagating with relativistic unmodulated electron beam is fed through a helical undulator tuned to the second harmonic of the laser, which acts as a pre-buncher that helically micro-bunches the beam, modulating it in energy. The energy modulation is transferred to helical density modulation by propagating through a longitudinally dispersive section, such as a chicane. Finally the helical density 3-D modulated electron beam is sent through a second undulator resonant at light’s fundamental frequency, causing the electron beam to radiate OAM light. NLCTA facility has everything to make this experiment, including a planar undulator tuned to the fundamental frequency, except for a helical pre-bunching undulator, which can be easily constructed and installed to generate OAM light at NLCTA. According to simulations generated with Mathematica 7 and Genesis 1.3 a 3 period long pre-buncher will be enough to get out 140 MW of laser power from a seeded 10 MW, after transversing a 1.5 m long planar radiator using electron beam generated by NLCTA. | ||
| THP168 | FEL Beam Stability in the LCLS* | 2423 |
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Funding: *This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 During commissioning and operation of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center electron and x-ray beam size, shape, centroid motion have been studied. The studies, sources, and remediation are summarized in this paper. |
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| THP170 | Observation and Characterization of Coherent Optical Radiation and Microbunching Instability in the SLAC Next Linear Collider Test Accelerator | 2426 |
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The NLC Test Accelerator (NLCTA) at SLAC is currently configured for a proof-of-principle echo-enabled harmonic generation (EEHG) experiment using a 120 MeV beam. During commissioning, unexpected coherent optical undulator radiation (CUR) and coherent optical transition radiation (COTR) was observed when beam is accelerated off-crest and compressed after the chicanes. The CUR and COTR is likely due to a microbunching instability where initial small modulations in the cathode drive laser pulse are compressed and amplified. In this paper we present the observation and characterization of the CUR, COTR and microbunching instability at NLCTA.
* D. Xiang et al., "Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers", PRL 105, 114801, 2010. |
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| THP171 | Demonstration of 3D Effects with High Gain and Efficiency in a UV FEL Oscillator | 2429 |
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Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences, the Office of Naval Research, and Joint Technology Office We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency. |
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| THP172 | Operation and Commissioning of the Jefferson Lab UV FEL using an SRF Driver ERL | 2432 |
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Funding: Supported by the US Dept. of Energy under DoE contract number DE-AC05-060R23177. We describe the operation and commissioning of the Jefferson Lab UV FEL using a CW SRF ERL driver. Based on the same 135 MeV linear accelerator as the Jefferson Lab 10 kW IR Upgrade FEL, the UV driver ERL uses a bypass geometry to provide transverse phase space control, bunch length compression, and nonlinear aberration compensation necessitating a unique set of commissioning and operational procedures. Additionally, a novel technique to initiate lasing is described. To meet these constraints and accommodate a challenging installation schedule, we adopted a staged commissioning plan with alternating installation and operation periods. This report addresses these issues and presents operational results from on-going beam operations. |
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| THP173 | Design of the SRF Driver ERL for the Jefferson Lab UV FEL | 2435 |
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Funding: Support by DoE Contract DE-AC05-060R23177. We describe the design of the SRF ERL providing the CW electron drive beam at the Jefferson Lab UV FEL. Based on the same 135 MeV linear accelerator as – and sharing portions of the recirculator with – the Jefferson Lab 10 kW IR Upgrade FEL, the UV driver ERL uses a novel bypass geometry to provide transverse phase space control, bunch length compression, and nonlinear aberration compensation (including correction of RF curvature effects) without the use of magnetic chicanes or harmonic RF. Stringent phase space requirements at the wiggler, low beam energy, high beam current, and use of a pre-existing facility and legacy hardware subject the design to numerous constraints. These are imposed not only by the need for both transverse and longitudinal phase space management, but also by the potential impact of collective phenomena (space charge, wakefields, beam break-up (BBU), and coherent synchrotron radiation (CSR)), and by interactions between the FEL and the accelerator RF system. This report addresses these issues and presents the accelerator design solution that now successfully supports FEL lasing. |
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| THP174 | A Single Cavity Echo Scheme | 2438 |
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Funding: This work was supported by the DIrector, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The possibility of implementing echo-enabled harmonic generation* (EEHG) within a single optical resonance cavity is explored both analytically and with numerical simulations. Two modulators of the same frequency are used so that the cavity radiation replaces the two seed lasers of conventional EEHG. Such a scheme has potential** to produce tunable radiation as in EEHG, but with the high repetition rate, longitudinal coherence, and narrow spectral bandwidth of an oscillator. These benefits, however, come with the complication that the beam must generate the radiation that modulates it. Analysis and GINGER simulations are presented for a specific example that takes advantage of robust multilayer mirror performance at 13.4 nm to produce radiation near or possibly even below 1 nm. * G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009). ** J. Wurtele et al., Proc. of the 2010 FEL Conference, TUOC12. |
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| THP175 | The Effects of Mirror Surface Error on Coherent X-Ray Propagation in XFELO Cavity | 2441 |
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We study the propagation of coherent X-ray mode through optical cavity of X-ray FEL oscillator (XFELO) including rough grazing incidence mirror.
References * K-J Kim, Y Shvyd'ko and S Reiche, Phys. Rev. Lett 100, 24802(2008) ** S. K. Sinha, E. B Sirota, S. Garoff, Phys. Rev. B38 2297 ((1988) *** G. Park in preparation |
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| THP176 | Progress Toward the Wisconsin Free Electron Laser | 2444 |
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Funding: NSF Award No. DMR-0537588 DOE Award No. DE-SC0005264 The University of Wisconsin-Madison/Synchrotron Radiation Center is advancing its design for a seeded VUV/soft X-ray Free Electron Laser facility called WiFEL. To support this vision of an ultimate light source, we are pursuing a program of strategic R&D addressing several crucial elements. This includes development of a high repetition rate, VHF superconducting RF electron gun, R&D on photocathode materials by ARPES studies, and evaluation of FEL facility architectures (e.g., recirculation, compressor scenarios, CSR dechirping, undulator technologies) with the specific goal of cost containment. Studies of high harmonic generation for laser seeding are also planned. |
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| THP178 | Design of the MAX IV Ring Injector and SPF/FEL Driver | 2447 |
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| The MAX IV linac will be used both for injection and top up into two storage rings, and as a high brightness injector for a Short Pulse Facility (SPF) and an FEL (in phase 2). Compression is done in two double achromats with positive R56. The natural second order momentum compaction, T566, from the achromats is used together with weak sextupoles to linearise longitudinal phase space, leaving no need for a linearising harmonic cavity. The design of the linac focuses on flexibility, simplicity and stability, while keeping the costs low. The accelerator structures have been ordered, as well as modulator/klystrons. The linac will be the first accelerator to be assembled and commissioned in the MAX IV project, starting mid 2012. | ||
| THP180 | Studies of a Linac Driver for a High Repetition Rate X-ray FEL | 2450 |
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Funding: Work carried out under Department of Energy contract No. DE-AC02-0SCK11231 We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a point-design for a 1.8 GeV machine tuned for 300~pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines. |
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| THP181 | Low Intensity Nonlinear Effects in Compton Scattering Sources | 2453 |
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The design and optimization of a Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering source are presented. A new precision source with up to 2.5 MeV photon energies, enabled by state of the art laser and x-band linac technologies, is currently being built at LLNL. Various aspects of the theoretical design, including dose and brightness optimization, will be presented. In particular, while it is known that nonlinear effects occur in such light sources when the laser normalized potential is close to unity, we show that these can appear at lower values of the potential. A three dimensional analytical model and numerical benchmarks have been developed to model the source characteristics, including nonlinear spectra. Since MEGa-ray sources are being developed for precision applications such as nuclear resonance fluorescence, assessing spectral broadening mechanisms is essential.
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. |
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| THP182 | Overview of Current Progress on the LLNL Nuclear Photonics Facility and Mono-energetic Gamma-ray Source | 2456 |
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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 A new class of gamma-ray light source based on Compton scattering is made possible by recent progress in accelerator physics and laser technology. Mono-energetic gamma-rays are produced from collisions between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linear accelerator designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable gamma-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. The source will be used to conduct nuclear resonance fluorescence experiments and address a broad range of current and emerging applications in nuclear photoscience. Users include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications. |
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| THP183 | Measurement of Femtosecond LCLS Bunches Using the SLAC A-line Spectrometer* | 2459 |
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| We describe a novel technique and the preliminary experimental results to measure the ultrashort bunch length produced by the LCLS low-charge, highly compressed electron bunch. The technique involves adjusting the LCLS second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result, the time coordinate of the bunch is directly mapped onto the energy coordinate at the end of the linac. A high-resolution energy spectrometer located at an existing transport line (A-line) is then commissioned to image the energy profile of the bunch in order to retrieve its temporal information. We present measurements of the single-digit femtosecond LCLS bunch length using the A-line as a spectrometer and compare the results with the transverse cavity measurement as well as numerical simulations. | ||
| THP184 | Tuning of the LCLS Linac for User Operation | 2462 |
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Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. With the Linac Coherent Light Source (LCLS) now in its third user run, reliable electron beam delivery at various beam energies and charge levels has become of high operational importance. In order to reduce the beam tuning time required for such changes, several diagnostics and feed-forward procedures have been implemented. We report on improved lattice diagnostics to detect magnet, model, and diagnostics errors as well as on measurements of transverse RF kicks and static field contributions and corresponding correction procedures to facilitate beam energy changes. |
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| THP186 | Lattice Design for ERL Options at SLAC | 2465 |
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Funding: Work supported by the U.S. Department of Energy under Contract number DE-AC02 76SF00515. SLAC is investigating long-range options for building a high performance light source machine while reusing the existing linac and PEP-II tunnels. One previously studied option is the PEP-X low emittance storage ring. The alternative option is based on a superconducting Energy Recovery Linac (ERL) and the PEP-X design. The ERL advantages are the low beam emittance, short bunch length and small energy spread leading to better qualities of the X-ray beams. Two ERL configurations differed by the location of the linac have been studied. Details of the lattice design and the results of beam transport simulations with the coherent synchrotron radiation effects are presented |
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| THP187 | Design Concept for a Compact ERL to Drive a VUV/Soft X-Ray FEL | 2468 |
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Funding: Support by US DOE contract #DE-AC05-060R23177 We explore possible upgrades of the existing Jefferson Laboratory IR/UV FEL driver to higher electron beam energy and shorter wavelength through use of multipass recirculation to drive an amplifier FEL. The system would require beam energy at the wiggler of 600 MeV with 1 mA of average current. The system must generate a high brightness beam, configure it appropriately, and preserve beam quality through the acceleration cycle - including multiple recirculations - and appropriately manage the phase space during energy recovery. The paper will discuss preliminary design analysis of the longitudinal match, space charge effects in the linac, and recirculator design issues, including the potential for the microbunching instability. A design concept for the recirculator and a lattice solution will be presented. |
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| THP189 | Low Horizontal Beta Function in Long Straights of the NSLS-II Lattice | 2471 |
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Funding: Work supported by U.S. DOE, Contract No. DE-AC02-98CH10886 The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 shorter straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this note, we explore the possibility of maintaining three long straights with large horizontal beta function while providing the other 12 long straights with smaller horizontal beta function to optimize the brightness of insertion devices. Our study considers the possible linear lattice solutions as well as characterizing the nonlinear dynamics. Results are reported on optimizations of dynamic aperture required for good injection efficiency and adequate Touschek lifetime. |
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| THP190 | Additional Quadrupoles at Center of Long Straights in the NSLS-II Lattice | 2474 |
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Funding: Work supported by U.S. DOE, Contract No. DE-AC02-98CH10886 The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 shorter straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this note, we explore the possibility of installing additional quadrupoles at the center of selected long straight sections in order to provide two low-beta source locations for undulators. The required modification to the linear lattice is discussed as well as the preservation of adequate dynamic aperture required for good injection efficiency and adequate Touschek lifetime. |
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| THP191 | Recent Progress in Injector Improvement of SPEAR 3 | 2477 |
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| The frequent injection and high current operation of SPEAR 3 storage ring requires high stability of the injector system at the Stanford Synchrotron Radiation Laboratory (SSRL). The lattice of linac-to-booster (LTB) transport line was not well understood and controlled prior to this work. In this paper, we discuss the significant efforts that have been made to improve the performance of the LTB. A method to correct the distortion of the closed orbit in the booster by moving 2 quadrupoles is also presented. | ||
| THP192 | Effect of Surface Roughness on the Emittance from GaAs Photocathode | 2480 |
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Funding: This work is supported by NSF under Grant No. DMR- 0807731 and DOE under Grant No. DE-SC0003965. The surface roughness of GaAs photocathodes used in the injector prototype for the ERL at Cornell University was measured and compared to that of the atomically polished GaAs crystal surface using the atomic force microscopy (AFM) technique. The results show at least an order of magnitude rise in the GaAs surface roughness after subjecting it to heat cleaning, prior to activation. An analytical model for photoemission that takes into account the effect of surface roughness has been developed. This model predicts emittance values close to the experimental observations, explains the experimentally observed variation of emittance with incident light wavelength and reconciles the discrepancies in experimental data. |
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| THP193 | Study of Single and Coupled-Bunch Instabilities for NSLS-II | 2483 |
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| We study single and coupled-bunch instabilities for the NSLS-II storage ring with a recently developed parallel tracking code. For accurate modelling of the coupled-bunch instability, we investigate improvements to current point-bunch models to take into account finite bunch-size effects. | ||
| THP196 | High Power Beam Test of a 1.6-cell Photocathode RF Gun at PAL | 2486 |
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Funding: This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST) (grant No. 2008-0059842) The photocathode RF gun with four holes at the side of the full cell will be tested soon at the gun test stand which consists of a 1.6 cell cavity, a solenoid magnet, beam diagnostic components and auxiliary systems such as ICT, spectrometer, YAG scintillator and screens, Faraday cup, etc. Basic diagnostics such as the measurements of charge, energy and its spread, transverse emittance will be performed. It is expected that these diagnostics will confirm a successful fabrication of the RF gun. In this presentation, we will show the status of the RF gun aging in PAL and detail plan of measurements on various beam parameters. The results with the simulation code PARMELA will be presented to prepare measurement devices properly. |
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| THP198 | Upgrade of the RF Photo-Injector for the Duke Storage Ring | 2489 |
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Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. The accelerator facility for the Duke FEL and High Intensity Gamma-ray Source (HIGS) consists of a linac pre-injector, a top-off booster injector, and the storage ring. The S-band RF gun with the LaB6 cathode was initially operated in the thermionic mode, producing a long electron beam pulse and a large radiation background. In 1997, the thermionic RF gun was converted to a photo-cathode operation using a nitrogen drive laser for single bunch injection into the storage ring. The photo-cathode operation typically delivers 0.1 nC of charge in a 1 ns long pulse to the linac. Since 2006, substantial improvements have been made to the photo-cathode and the linac, including improvements of the nitrogen drive laser, development of driver laser optical transport and beam monitoring system, and optimization of the cathode heater current to minimize the thermionic emission. In addition, two electron beam charge measurement systems using Faraday cup detectors and sample and hold electronics have been developed. In this work, we will present these new developments and discuss the impact of these upgrades on everyday operation of the linac pre-injector. |
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| THP199 | Raising Photoemission Efficiency with Surface Acoustic Waves | 2492 |
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Funding: Supported in part by Muons, Inc. Current and future synchrotron radiation light sources and free electron laser facilities are in need of improvements in Electron Gun Technology, especially regarding the cost and efficiency of photoinjectors. The generation of Surface Acoustic Waves (SAW) on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the surface of the material. These fields significantly reduce the recombination probability of electrons and holes which can result in enhanced quantum efficiency of photoemission. Additional advantages are provided by the mobility of charge carriers that can be controlled by SAW. It is expected that this novel feature will result in enhanced efficiency of photocathode operation, leading to the production of intense, low emittance electron bunches at a high repetition rate using laser excitation. |
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| THP200 | Photoinjector Beam Dynamics for a Next Generation X-Ray FEL | 2495 |
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Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. In this paper, we will present the status of the beam dynamics simulations for a Next Generation Light Source (NGLS) injector, based on a high repetition rate (1 MHz), high brightness design. A multi-stage beam compression scheme is proposed, based on the concepts of velocity bunching and emittance compensation. For the optimization of the design parameters we use a genetic algorithm approach, and we focus on a mode providing charges of 300 pC, with normalized transverse emittance less than 0.6 microns, suitable to operate a next generation light source based on an X-ray FEL. In addition, we discuss the effects of bunch compression and linearity of the transverse and longitudinal phase space of the beam. |
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| THP202 | First Operation of the LANL/AES Normal Conducting Radio Frequency Photoinjector | 2498 |
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Funding: We gratefully acknowledge funding from the Office of Naval Research (ONR) and the High Energy Laser Joint Technology Office (HEL-JTO). The LANL/AES normal-conducting radio-frequency (NCRF) injector has undergone high power testing, confirming field gradients of up to 10 MV/m at the cathode. Most NCRF designs are limited to low-duty-factor operation to constrain rf power consumption and limit ohmic heat generation. This cavity structure utilizes high density micro-channel cooling to successfully remove heat with the option of dynamic temperature control to actively adjust cavity resonance. This first high power rf test demonstrated stable cw (100% duty cycle) operation using resonant frequency tracking and produced intentional dark current emission from a roughened cathode blank. Resulting end-point x-ray measurements confirm the cathode gradient of 9.8 ± 0.2 MV/m required for acceleration of nC bunches to a beam energy of 2.5 MeV. |
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| THP203 | Improved Inverted DC Gun Insulator Assembly | 2501 |
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Funding: Work supported in part by USDOE Contract No. DE-AC05-84-ER-40150. High gradient DC guns are currently being developed with inverted ceramic insulators in order to avoid failure of the insulators from field emission and charge build-up. Our goal is to increase the DC voltages from 250 kV to 500 kV in these inverted ceramic DC Gun insulator assemblies. To achieve reliability, the arc-path gradient along the length of the insulator ceramic at the interface with the dielectric material should be lower than 500 kV/m (13 V/mil). In order to achieve this low arc-path gradient, a novel extended inverted insulator ceramic is being developed. Novel assembly processes are being developed for the high voltage connector, so that the interface between the connector dielectric and the surface of the extended inverted ceramic insulator will be void free. A complete DC Gun Inverted Ceramic Insulator Assembly will be designed and fabricated for reliable 500 kV DC operation. |
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| THP204 | Corrections to Quantum Efficiency Predictions for Low Work Function Electron Sources | 2504 |
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Funding: Funding by the Joint Technology Office and the Office of Naval Research. The Three-Step Model of Spicer, or the analogous Moments-based models, can be used to predict photoemission from metals and cesiated metals. In either, it is a convenient approximation to neglect electrons that have undergone scattering. Using Monte Carlo to follow scattered electrons, we assess the utility of the approximation particularly for low work function (cesiated) surfaces. |
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| THP205 | Modeling the Performance of a Diamond Current Amplifier for FELs | 2507 |
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Funding: We gratefully acknowledge funding by the Joint Technology Office and the Office of Naval Research. A diamond current amplifier concept can reduce demands made of photocathodes under development for high performance Free Electron Lasers (FELs) by augmenting the charge per bunch (i.e., increasing the apparent QE of the photocathode) by employing secondary emission amplification in a diamond flake*. The characteristics of the bunch that emerges from the diamond flake is dependent on properties of the diamond (e.g., impurity concentrations) and the conditions under which it is operated (e.g., voltage drop, space charge, temperature)**. A study of the electron bunches produced by an incident 3-5 keV beam striking a very thin diamond and its transport under bias subject to scattering and space charge forces is considered. The quantities of greatest interest are then the yield, the transit time, emittance, and the rise/fall characteristics of the emerging bunch. These are simulated using Monte Carlo techniques, the application of which shall be described as it applies to the initial generation of the secondary electrons followed by their scattering and transport in the presence of band bending and space charge. *J.E. Yater, et al., IEEE IVNC (2009); J. L. Shaw, et al., ibid. **K.L. Jensen, et al. J. Appl. Phys. 108, 044509 (2010). |
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| THP208 | Development of Alkali-Based High Quantum Efficiency Semiconductors for Dispenser Photocathodes | 2510 |
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Funding: This work is supported by the Office of Naval Research. Photocathodes as electron beam sources can meet the stringent requirements of high performance FELs, but exhibit a lifetime-efficiency tradeoff. High quantum efficiency (QE) cathodes are typically semiconductors, well described by recently enhanced theory*. Cesium dispenser technology, proven to extend lifetime of tungsten cathodes**, can be extended to high QE via the development of semiconductor coatings which are suitable for rejuvenation. Rejuvenation occurs via controlled cesium diffusion through a sintered substrate to resupply the surface (as described by models of pore*** and surface**** diffusion). Compatible coatings must be thermally stable materials with a cesium-based surface layer. Following standard fabrication processes*****, we discuss alkali antimonides and alkali aurides as cesium dispenser photocathode coatings and analyze future prospects. We also describe improvements to experimental techniques. *K.L. Jensen et al., (this conference) **Moody et al., J. Appl. Phys. 102(10), 2010 ***B.C. Riddick et al., (this conference) ****P.Z. Pan et al., (this conference) *****S.A. Khan et al., (this conference) |
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| THP211 | Design Features and Construction Progress of 500-Mhz Rf Systems for the Taiwan Photon Source | 2513 |
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| The accelerator complex of the Taiwan Photon Source (TPS) consists of two 500-MHz RF systems: one RF system with KEKB-type single-cell SRF modules is used for the 3-GeV storage ring of circumference 518 m, and the other with five-cell Petra cavities at room temperature is for the concentric full-energy booster synchrotron. This overview of the construction of the 500-MHz RF systems for the TPS is presented with emphasis on our strategy to approach the expectation of highly reliable SRF operation of the TPS. How to complete the construction project on time, on budget and on performance is our unique concern. | ||
| THP212 | Superconducting Cavity Design for Short-Pulse X-Rays at the Advanced Photon Source | 2516 |
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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. Superconducting cavities have been analyzed for the short-pulse x-ray (SPX) project at the Advanced Photon Source (APS). Due to the strong damping requirements in the APS storage ring, single-cell superconducting cavities have been designed. The geometry has been optimized for lower-order and higher-order mode damping, reduced peak surface magnetic fields, and compact size. The integration of the cavity assembly, with dampers and waveguide input coupler, into a cryomodule will be discussed. |
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| THP213 | Traveling Wave Electron Linac for Synchrotron Injector | 2519 |
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| In this paper the project design of a travelling wave electron linac used as an injector to synchrotron in Lebedev Physical Institute of the Russian Academy of Sciences (LPI RAS) is presented. The injected beam to the synchrotron should have very small emittance and energy spectrum. Thus, the buncher design is an essential question in this problem. One of the best output beam parameters can be achieved by using a waveguide buncher with the non-uniform parameters. The proposals of optimal buncher design and beam dynamics calculation results are presented. | ||
| THP214 | Pulsed Multipole Injection for the MAX IV Storage Rings | 2522 |
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| The MAX IV facility presently under construction will include two storage rings for the production of synchrotron radiation. The 3 GeV ring will house insertion devices for the production for x-rays while the 1.5 GeV ring will serve UV and IR users. Both rings will be operated at a constant 500 mA of stored current with top-up shots supplied by the 3.5 GeV MAX IV linac acting as a full-energy injector. So far, injection into both storage rings has been designed using a conventional approach: a closed four-kicker injection bump brings the stored beam to the septum blade where the injected bunches are captured in a single turn. Recently, studies have been carried out to investigate the feasibility of using a pulsed multipole for injection into the storage rings. Pulsed multipole injection does not require an injection bump and has the potential to make top-up injection transparent to users. This paper reports on these studies and summarizes requirements for the pulsed sextupole magnet to be installed for injection into the MAX IV storage rings. | ||
| THP215 | Performance of the Diagnostics for NSLS-II Linac Commissioning | 2525 |
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Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron and associated transfer lines. The transfer lines not only provide a means to delivering the beam from one machine to another, they also provide a suite of diagnostics and utilities to measure the properties of the beam to be delivered. In this paper we discuss the suite of diagnostics that will be used to commission the NSLS-II linac and measure the beam properties. The linac to booster transfer line can measure the linac emittance with a three screens measurement or a quadrupole scan. Energy and energy spread are measured in a dispersive section. Total charge and charge uniformity are measured with wall current monitors in the linac and transformers in the transfer line. We show that the performance of the transfer line will be sufficient to ensure the linac meets its specifications and provides a means of trouble shooting and studying the linac in future operation. |
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| THP216 | Progress with NSLS-II Injection Straight Section Design | 2528 |
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Funding: This work is supported by U.S. DOE, Contract No.DE-AC02-98CH10886 NSLS-II injection straight section consists of the pulsed and DC/Slow bumps, septa system, beam trajectory correction and diagnostics systems. In this paper we discuss overall injection straight layout, preliminary element designs, specifications for the pulsed and DC magnets and their power supplies, vacuum devices and chambers and diagnostics devices. |
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| THP217 | Frequent Fill Top-Off Injection at SPEAR3 | 2531 |
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Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76-SF00515 SPEAR3 beam is now delivered to users in a "frequent fill" mode in which beam is injected into the storage ring, with beam-line shutters open, on a periodic schedule so that the beam current is kept constant to within 1% of its average value. This goal was achieved with the constraints of having the SPEAR3 injector run at very high reliability and ensuring that there would be no challenges to the beam containment system in this operational mode. This paper presents the accelerator development, the hardware changes, and the software developed to implement this operational mode. |
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| THP218 | Design Concept for a Modular In-vacuum Hall Probe Mapper for use with CPMU Convertible In-vacuum Undulators of Varying Magnetic Length | 2534 |
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Funding: NSLS-II, Brookhaven National Laboratory, working under the U.S. DOE, Contract No.DE-AC02-98CH10886. Both In-Vacuum Undulators (IVU) and Cryogenic Permanent Magnet Undulators (CPMU), each important to third generation light sources, are best characterized in their operating environment. To create a precise Hall probe map of an IVU/CPMU (IVU hereafter), an In-Vacuum Magnetic Measurement (IVMM) System is proposed. Point-by-point measurement of field and trajectory error at operating conditions informs corrective tuning. A novel design concept for a universal IVMM System has been developed and explored. The IVMM seals to the rectangular UHV-flange of the IVU and shares its common vacuum space. Moreover, a modular design permits a range of IVU of varying magnetic length to be mapped with a single IVMM System, and is thus cost effective when multiple IVU of different configuration are planned. Here we review aspects of the modular IVMM design concept. |
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| THP222 | Drive Laser System for the Advanced Photo-Injector Project at the LBNL | 2537 |
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Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. The electron photo-gun of the Advanced Photo-injector EXperiment project (APEX) at the LBNL will be driven by a compact fiber laser for different photo-cathode experiments during the initial phase of the project. The fiber laser, developed at the Lawrence Livermore National Laboratory, is designed to deliver μJ/pulse at 1064 nm system that is frequency doubled to deliver light at 532nm with 1MHz repetition rate and 1ps pulse length optimized for photo-emission with multi-alkali antimonide cathodes. For Cs2Te and diamond amplifier cathodes, the 4th harmonic will be generated by doubling frequency again in a non-linear crystal. Due to the requirement of small emittance for the electron beam, the laser pulse will be shaped in space and time for 532nm and UV lights, in general with a constant intensity in cross section with a sharp radial cutoff, and elliptical or rectangular distribution in the longitudinal plane. Diagnostics of the laser beam itself and of the cathode will be integrated with techniques such as cross- correlation, streak camera, and virtual cathode imaging, not only to monitor the laser pulse but also to provide automated feedbacks. |
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| THP223 | Laser Systems for Livermore's Mono-Energetic Gamma-Ray Source | 2540 |
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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. A Mono-energetic Gamma-Ray (MEGa-Ray) source, based on Compton scattering of a high-intensity laser beam off a highly relativistic electron beam, requires highly specialized laser systems. To minimize the bandwidth of the gamma-ray beam, the scattering laser must have minimal bandwidth, but also match the electron beam depth of focus in length. This requires a ~1 J, 10 ps, fourier-transform-limited laser system. Also required is a high-brightness electron beam, best provided by a photoinjector. This electron source in turn requires a second laser system with stringent requirements on the beam including flat transverse and longitudinal profiles and fast rise times. Furthermore, these systems must be synchronized to each other with ps-scale accuracy. Using a novel hyper-dispersion compressor configuration, advanced fiber amplifiers, and diode-pumped Nd:YAG amplifiers, we have designed laser systems that meet these challenges for the x-band photoinjector and Compton-scattering source being built at Lawrence Livermore National Laboratory. |
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| THP224 | Progress Report on Development of Novel Ultrafast Mid-IR Laser System | 2543 |
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| Of particular interest to X-ray FEL light source facilities is Enhanced Self-Amplified Spontaneous Emission (ESASE) technique. Such a technique requires an ultrafast (20-50 fs) high peak power, high repetition rate reliable laser systems working in the mid-IR range of spectrum (2μm or more). The approach of this proposed work is to design a novel Ultrafast Mid-IR Laser System based on optical parametric chirped-pulse amplification (OPCPA). OPCPA is a technique ideally suited for production of ultrashort laser pulses at the center wavelength of 2 μm. Some of the key features of OPCPA are the wavelength agility, broad spectral bandwidth and negligible thermal load. This paper reports on the progress of the development of the Ultrafast Mid-IR Laser System. | ||
| THP225 | Characterization and Suppression of the Electromagnetic Interference Induced Phase Shift in the JLab FEL Photo – Injector Advanced Drive Laser System | 2546 |
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| The new drive laser for the photo-cathode gun used in the JLab FEL facility had been experiencing various phase shifts on the order of tens of degrees (>20° at 1497 MHz or >40ps) when changing the Advanced Drive Laser (ADL) micro-pulse frequencies. These phase shifts introduce multiple complications when trying to setup the accelerator for operation, ultimately inhibiting the robustness and overall performance of the FEL. Through rigorous phase measurements and systematic characterizations, we discovered the problems could be attributed to EMI coupling into the ADL phase control loop system, and subsequently resolved the issue of phase shift to within tenths of a degree (<0.5° at 1497 MHz or <1ps). The diagnostic method developed and the knowledge gained through the entire process will prove to be invaluable for future designs of similar systems. | ||