| Paper | Title | Page |
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| MO6RFP064 | Stacking Simulations for Compton Positron Sources of Future Linear Colliders | 512 |
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The Compton positron source of a future linear collider must obtain the target bunch population by accumulating a large number of positron packets, arriving either in a number of bursts from a “Compton ring”, with intermediate damping of the scattering electron beam, or quasi-continually from a “Compton energy recovery linac”. We present simulation results for the longitudinal stacking of Compton positrons in the ILC damping ring and the CLIC pre-damping ring, reporting parameter optimization, stacking efficiency, possible further improvements, and outstanding questions. |
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| MO6RFP068 | ERL Parameters for Compton Polarized Positron Sources | 524 |
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One of the main challenges for the future linear colliders projects (ILC and CLIC) is to design an efficient positron source taking into account the constraints imposed by the target heating. At present, different schemes have been analysed to produce high energy gammas and to convert them in an amorphous target. One of them considers the possibility to boost the energy of the backscattered photons of a laser pulse by Compton effect. This method is very attractive since the source is independent from the main Linac and since the photon helicity is conserved in Compton scattering and subsequently transferred to the produced pairs. This allows the physics experiments disposing of both positron and electron polarised sources. Different schemes have been proposed to provide the electron beam for the Compton collisions. taking into account the constraint imposed by the low value of the Thomson cross section. One of the explored possibilities is to design an ERL with relatively low repetition frequency, high charge per pulse and then to stack the produced positrons in an accumulation ring. Different considerations on this scheme will be illustrated and the main constraints discussed. |
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| MO6RFP069 | A Study of Lifetime of GaAs Photocathode for High Brightness Electron Source | 527 |
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High brightness electron source is a key technology for future projects based on advanced accelerators. Although GaAs photo-cathode is very attractive because it can generate highly polarized and extremely high brightness electron beam, the limited operational life time is a technical issue. In Hiroshima University, a photo-cathode test bench is implemented for various studies of GaAs photo-cathode. Super high vacuum, 9E-9Pa, was achieved and the cathode was successfully activated by processes of heat cleaning technique and the alternate evaporation of Cs and oxygen. The quantum efficiency and its lifetime were investigated as a function of cathode temperature, simulating temperature rise by the high power cathode drive laser. Wavelength dependence was also investigated. |
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| MO6RFP074 | Design and Fabrication of a 500-kV Photocathode DC Gun for ERL Light Sources | 542 |
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A 500-kV, 10-mA photocathode DC gun has been designed and is now under fabrication by the collaboration efforts of JAEA, KEK, Hiroshima Univ. and Nagoya Univ. The Cockcroft-Walton generator and the ceramic insulator are installed upright in the SF6 tank. We have adopted a multiple-stacked cylindrical ceramic insulator, because this type of ceramic insulator has shown good stability and robustness at the 200-kV Nagoya polarized gun and the 250-kV JAEA FEL gun. All the vacuum chambers are made of titanium alloy with very low out-gassing. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chambers will be fabricated by April 2009 and a high-voltage test will be started soon later. Up-to-date status of the gun development will be presented in detail. |
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| TU5RFP081 | Status of the Energy Recovery Linac Project in Japan | 1278 |
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Future synchrotron light source project using an energy recovery linac (ERL) is under proposal at the High Energy Accelerator Research Organization (KEK) in collaboration with several Japanese institutes such as the JAEA and the ISSP. We are on the way to develop such key technologies as the super-brilliant DC photo-injector and superconducting cavities that are suitable for both CW and high-current operations. We are also promoting the construction of the Compact ERL for demonstrating such key technologies. We report the latest status of our project, including update results from our photo-injector and from both superconducting cavities for the injector and the main linac, as well as the progress in the design and preparations for constructing the Compact ERL. |
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| WE6RFP065 | The CLIC Positron Source Based on Compton Schemes | 2945 |
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The CLIC polarized positron source is based on a positron production scheme in which polarized photons are produced by Compton process. Compton backscattering happens in a so-called "Compton ring" where an electron beam of 1.06 GeV interacts with a powerful laser beam amplified in an optical resonator. The circularly-polarized gamma rays are sent on to a target, producing pairs of longitudinally polarized electrons and positrons. An Adiabatic Matching Device maximizes the capture of the positrons. A normal-conducting 2 GHz Linac accelerates the beam up to 2.424 GeV before injection into the Pre-Damping Ring (PDR). The nominal CLIC bunch population is 4.4x109 particles per bunch. Since the photon flux coming out from a "Compton ring" is not sufficient to obtain the requested charge, a stacking process is required in the PDR. Another option is to use a "Compton Energy Recovery Linac" where a quasi-continual stacking in the PDR could be achieved. A third option is to use a "Compton Linac" which would not require stacking. We describe the overall scheme as well as advantages and constraints of the three different options. |