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WG1011 |
Performance of the ALICE ERL Photoinjector Photocathode Gun | |
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| Accelerators and Lasers In Combined Experiments (ALICE) is a 35 MeV energy-recovery linac at Daresbury Laboratory. The ALICE electron beam drives an IR-FEL and THz light sources. The ALICE photoinjector gun is a variant of the JLab IR-FEL design, operating at 350 kV DC with a GaAs cathode. Photocathode activation is carried out in-situ, normally using caesium and oxygen, though nitrogen triflouride (NF3) has been used for a limited period. An upgrade to the ALICE photoinjector gun has been designed and partially constructed. Based on an external state-of-the-art Photocathode Preparation Facility (PPF), it offers an excellent environment for photocathode preparation, activation and operation. This paper reviews the current ALICE photocathode gun performance, presenting beam parameters obtained with GaAs photocathodes and outlines future plans for improving the gun beam quality. We will also compare photocathode performance in the ALICE gun when activated using both O2 and NF3 as the oxidant to that demonstrated in the PPF. | ||
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Slides WG1011 [4.542 MB] | |
WG1017 |
Photocathode R&D for High Average Current ERL Photoinjectors at Daresbury Laboratory | |
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| Significant effort has been expended over several years at Daresbury on R&D in the procedures underlying the preparation of the GaAs photocathode family for use as electron sources in ERL injectors. Having established robust chemical and thermal cleaning processes, and carried out lifetime studies on activated photocathodes by deliberately poisoning them, we will present data showing the different levels of quantum efficiency achievable using a heterostructure photocathode when activating with both oxygen and nitrogen-triflouride. The next goal in our research programme is to investigate the ultimate emittance achievable from the GaAs photocathode family. One option under consideration is the cooling of photocathodes to Liquid Nitrogen (LN) temperature, and two experimental programmes have been instigated on this basis. The first is intended to measure the energy spread of electrons emitted from the photocathode, and observe how the energy spread evolves during photocathode degradation. The second programme aims to characterise photocathode emittance and response time in a relatively low energy 160 kV photocathode gun. | ||
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Slides WG1017 [1.586 MB] | |