February 7, 2018 - Meeting to discuss project write-ups, papers on the near term horizon

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Source Group Projects that need to be Written-up, Feb 7, 2018

Gun Test Stand

1) 300 kV inverted gun, with alkali-antimonide deposition chamber (POCs, Carlos and Yan)

    • Electrostatic design (Yan, Gabriel, Carlos)
    • HV conditioning results (Yan, Carlos)
    • Deposition chamber (Mamun)
    • Beam based evaluation of photocathode - thermal emittance (Yan)
    • Beam based evaluation of electrostatic properties - emittance map (Yan)
    • Lifetime at 4.5mA, dc beam and with rf structure (and with gun magnet ON) (Yan)

2) Magnetized beam from dc high voltage photogun (POCs, Riad and Mamun)

    • Beam magnetization vs gun solenoid field strength, for three laser spot sizes (Mamun)
    • Compare measurement to prediction (Sajini, Mamun)
    • Emittance measurements? (Sajini)
    • Lifetime at 4.5 mA, with rf structure

3) gain switched MO and fiber amplifier at 1064/532nm (POC, Shukui)

    • Describe performance versus rep rate 100 to 3000 MHz, pulsewidth, stability, phase noise, linewidth, doubling efficiency, max power for the GTS system


1) Lifetime studies, polarized beam at mA current (POC, Grames)

    • Lifetime vs beam current for different laser spot sizes
    • For CEBAF conditions, quantify “beam loss that matters”
    • Can you get an estimate of vacuum along the beamline, based on ion pump currents? Molflo prediction?
    • Polarization vs beam current: one beam through variable slit, and with two beams

2) Update the CEBAF photoinjector with focus on PV experiments (POC, Poelker)

    • Beam envelope map (Alicia, Reza)
    • With assistance, validation from Geoff, Mike T., and others
    • Two Wien spin flipper, interesting beam-based observations (Grames)
    • PC fast switch (John)
    • PC alignment procedure (Paschke, Riad, John)
    • Flipping schemes (Riad)
    • Envelope matching for adiabatic damping (Chao or Yves)
    • Much more….

3) 5 MeV Mott paper

    • Joe needs to write the GEANT model section and send to Charlie (Marty can help)

4) Applications of PEPPo (Joe and Eric)

    • Can PEPPo technique be used to provide polarized positron beam at ILC, EIC, CEBAF, etc.,


1) Benefits of NEG coating, toward achieving XHV (POC, Marcy)

    • Paper submitted to JVST, waiting to hear back

2) Potential benefits of cryopumping toward achieving XHV (POCs, Marcy, Anahi)

    • Can you make the BBB gauge read in the -13 Torr range?
    • Any indication that the ion pump limits our ultimate pressure?
    • Assuming pressure is lower with cryopump, can you explain why? Simply better because you provide more H2 pump speed, or Argon pump speed?


1) COMSOL electrostatic modeling of CEBAF inverted guns (POCs, Gabriel, Carlos)

    • Benefits of using COMSOL (eg. more common multipurpose tool, can incorporate conductivity of insulator material and rubber plug)
    • Describe the 200kV gun design
    • Application of voltage from the side, a possible problem: modeling results, together with beam based observation, beam astigmatism vs laser radial placement?
    • Triple point shield at ground potential? helpful?