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JLab FEL Gun Test Stand status

JLab FEL Gun Test Stand status. C. Hernandez-Garcia May 1 2007. Single pulse beam is expected this fall in the Gun Test Stand housing the second version of the Upgrade FEL photocathode gun. It will serve as the test bed for:. 500 kV operation with field emission suppression coated electrodes

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JLab FEL Gun Test Stand status

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  1. JLab FEL Gun Test Standstatus C. Hernandez-Garcia May 1 2007

  2. Single pulse beam is expected this fall in the Gun Test Stand housing the second version of the Upgrade FEL photocathode gun. It will serve as the test bed for: • 500 kV operation with field emission suppression coated electrodes • High charge (1-2 nC) single pulse beam characterization • NEG coated chamber for improved vacuum conditions, and • A semi-load lock system for increased productivity during cathode change-out and for testing different cathode materials • Drive Laser R&D

  3. The gun assembly with coated electrodes for field emission suppression was completed in mid September 2006. GTS status

  4. The assembly was moved to the GTS in September 2006 and is currently under vacuum in a temporary chamber while the latest version is completed. GTS status cont’

  5. The latest version of the gun chamber has been machined out from a single ‘bead’ of vacuum arc re-melt, cross forged 316 LN Stainless Steel. The chamber is awaiting vacuum firing for hydrogen desorption before completion. This chamber will be NEG coated using a process tested successfully on the gun temporary chamber. GTS status cont’

  6. The anode plate will be used as a mirror instead of a ligthbox further downstream for illuminating the photocathode with the drive laser. This new anode has been fabricated from a solid Molybdenum block and is currently being polished by hand to better than 1 micron surface finish. Brewster windows are being manufactured. Incoming drive laser beam Anode plate 12 inches GTS status cont’ Electron beam

  7. A design of a semi-load lock system for replacing cathodes without perturbing the gun chamber vacuum has been completed and fabrication awarded to McAllister Inc. This system will also allow re-cesiation without opening the SF6 tank, shortening the process from 3.5 to 0.5 hours. 60 inches 12 inches GTS status cont’ Bellows The bellows are extended to retract the cathode stalk and the valve is closed Valve The bellows are compressed to insert the cathode stalk with the valve open. The compressed bellows fit within the corona shield

  8. The old IR Demo 500 kV, 5 mA DC high voltage power supply (HVPS) will power up the photocathode gun. The SF6 pressurized tank has been refurbished and hydro-tested. It is installed and being fitted with components. GTS status cont’

  9. The GTS vault has been surveyed and the anchoring locations for the gun stand and the HVPS have been marked down. The layout below shows the proposed beam line MS Drift Drift Drift F. C. 11 feet GTS status cont’ Gun SF6 can Diagnostic beam line 500 kV DC HVPS tank

  10. Use existing FEL drive laser Antares. It will be replaced by the Advanced Drive Laser. But need to boost the pulse energy of the existing Antares laser To produce 1.35 nC bunches with 2% cathode QE, we need ~200nJ per pulse at 527 nm and 50 ps FWHM

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