| Paper | Title | Page |
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| TUPEA006 | Mismatch Induced Oscillations of Space Charge Dominated Beams in a Uniform Focusing Channel | 1336 |
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Space charge effects due to the strong Coulomb interactions expected in high intensity accelerator beams result in undesirable beam degradation and radio-activation of the vacuum tubes through halo formations. Various space charge effects have been studied intensively with particle simulations. This is partly because the analytical formulation of the nonlinear evolution in high intensity beams is not possible in general cases. And the systematic study of space charge effects with the real accelerators is not feasible. Although the development of computation environment is outstanding, some approximations are still necessary so far. Thus, it was proposed to use solenoid traps and linear Paul traps for investigating some properties of space charge dominated beams. The key idea is that the charged particles in these traps are physically equivalent with a beam in a FODO lattice. Some experimental results have been reported with the use of Paul traps. Here, a solenoid trap with a beam imaging system composed of a charge coupled device camera and a phosphor screen was employed to study the mismatch induced oscillations of a space charge dominated beams. |
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| TUPEC009 | Development of a Photocathode RF Gun for the L-band Linac at ISIR, Osaka University | 1728 |
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We conduct research on Free Electron Laser (FEL) in the infrared region and pulse radiolysis for radiation chemistry using the 40 MeV, 1.3 GHz L-band linac of Osaka University. At present, the L-band linac is equipped with a thermionic electron gun. It can accelerate a high-intensity single-bunch beam with charge up to 91 nC but the normalized emittance is large. In order to advance the research, we have begun development of a photocathode RF gun for the L-band electron linac in collaboration with KEK and Hiroshima University. We start the basic design of the RF gun cavity for the L-band linac at ISIR, Osaka University, based on the 1.5 cells, which is a normal conducting photocathode RF gun. A material of the cathode should be Cs2Te, which has the high quantum efficiency of a few percents, to produce a beam with high charge up to 30 nC/bunch. We improve the cooling system of the cavity for high duty operation to suppress the thermal deformation due to the heat load of input rf power. The simulation study has been also performed for the L-band linac at ISIR with a high charge electron beam. In this conference, we describe the details of the L-band photocathode RF gun development. |
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| TUPE086 | A Study of Lifetime of NEA-GaAs Photocathode at Various Temperatures | 2323 |
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We report that a lifetime of GaAs photocathode activated the surface to negative electron affinity (NEA) at various temperatures. An electron source with the NEA-GaAs photocathode is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac, in which a high power laser is illuminated to the photocathode for generation of the electron beam of 100mA. For example, the laser power of 15W should be needed for the quantum efficiency of 1% and the wavelength of 800nm. Consequently the high power laser causes to rise the GaAs temperature. The degradation of photo emission from the cathode is enhanced by a thermal desorption of Cs due to the temperature rise, even if the beam is not extracted. We have measured the cathode lifetime at various temperatures between room temperature and 100 C. |
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| TUPE087 | Development of a Photocathode Test Bench using a Cryo-pump and a NEG Pump | 2326 |
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A NEA-GaAs photocathode is an important component for the next generation light source based on the ERL. Although the NEA-GaAs cathode has high quantum efficiency, deterioration of the NEA surface becomes serious with a high current operation. Therefore improvement of a vacuum in the cathode chamber is essential to get a long lifetime of the NEA-GaAs cathode. We are developing a photocathode test bench consisting of titanium (TP340) chamber, whose outgas rate is 1/1000 smaller than one of a SUS chamber, a cryo-pump (4000l/s) and a NEG pump (1900l/s). We report mainly the vacuum performance of the system. |
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| TUPE093 | High-Voltage Test of a 500-kV Photo-Cathode DC Gun for the ERL Light Sources in Japan | 2341 |
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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. The vacuum chamber, the guard-rings and the support-rod electrode are made of titanium alloy with very low out-gassing and robustness to high voltage performances. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chamber and the guard-rings have been assembled and a high-voltage test has been successfully done with up to 550kV. The high-voltage test and up-to-date status of the gun development will be presented in detail. |
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| TUPE091 | Recent Progress in the Energy Recovery Linac Project in Japan | 2338 |
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Future synchrotron light source using a 5-GeV-class energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting active R&D efforts for that. We are developing super-brilliant DC photocathode guns, two types of cryomodules for both injector and main superconducting linacs, 1.3 GHz high CW-power rf sources, and other important components. We are also constructing a compact ERL for demonstrating the recirculation of low-emittance, high-current beams using those key components. We present our recent progress in this project. |
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| THPEC024 | Development of a High Average Power Laser Generating Electron Beam in ILC Format for KEK-STF | 4098 |
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Aim of Super-conducting Test Facility (STF) at KEK is demonstrating technologies for International Linear Collider. In STF, one full RF unit will be developed and beam acceleration test will be made. In super-conducting accelerator, precise RF control in phase and power is essential because the input RF power should be balanced to beam accelerating power. To demonstrate the system feasibility, the beam accelerating test is an important step in R&D phase of STF and ILC. To provide ILC format beam for STF, we develop an electron source based on photo-cathode L-band RF gun. To generate ILC format beam, we developed a laser system based on Yb fiber oscillator in 40.6 MHz. The pulse repetition is decreased by picking pulses in 2.7 MHz, which meets ILC bunch spacing, 364 ns. The pulse is then amplified by YLF laser up to 8 uJ per pulse in 1 mm. The light is converted to 266 nm by SHG and FHG. Finally, 1.5 uJ per pulse is obtained and 3.2 nC bunch charge will be made. We report the basic performance of the laser system from the accelerator technology point of a view. |