A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z    

Jordan, K.

Paper Title Page
TOAC004 Experimental Investigation of Beam Breakup in the Jefferson Laboratory 10 kW FEL Upgrade Driver 369
 
  • C. Tennant, D. Douglas, K. Jordan, L. Merminga, E.P. Pozdeyev, H. Wang
    Jefferson Lab, Newport News, Virginia
  • I.V. Bazarov
    Cornell University, Department of Physics, Ithaca, New York
  • G. Hoffstaetter
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • S. Simrock
    DESY, Hamburg
  • T.I. Smith
    Stanford University, Stanford, Califormia
 
  Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, Cornell University and by DOE Contract DE-AC05-84ER40150.

In recirculating accelerators, and in particular energy recovery linacs (ERLs), the maximum current has been limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovered pass. This effect is of particular concern in the design of modern high average current energy recovery accelerators utilizing superconducting technology. Experimental observations of the instability at the Jefferson Laboratory 10 kW Free-Electron Laser (FEL) are presented. Measurements of the threshold current for the instability are presented and compared to the predictions of several BBU simulation codes. To further characterize the instability, beam based measurements were made to determine the orientation of the dangerous HOMs. With BBU posing a threat to high current beam operation in the FEL, several suppression schemes were developed. These include direct damping of the dangerous HOMs and appropriately modifying the electron beam optics. Preliminary results of their effectiveness in raising the threshold current for stability are presented.

 
WPAP050 A High Average Current DC GaAs Photocathode Gun for ERLs and FELs 3117
 
  • C. Hernandez-Garcia, S.V. Benson, D.B. Bullard, H.F.D. Dylla, K. Jordan, C. M. Murray, G. Neil, M.D. Shinn, T. Siggins, R.L. Walker
    Jefferson Lab, Newport News, Virginia
 
  Funding: This work supported by The Office of Naval Research under contract to the Dept. of Energy, the Air Force Research Lab, and the Commonwealth of Virginia.

The Jefferson Lab (JLab) 10 kW IR Upgrade FEL DC GaAs photocathode gun is presently the highest average current electron source operational in the U.S., delivering a record 9.1 mA CW, 350 kV electron beam with 122 pC/bunch at 75 MHz rep rate. Pulsed operation has also been demonstrated with 8 mA per pulse (110 pC/bunch) in 16 ms-long pulses at 2 Hz rep rate. Routinely the gun delivers 5 mA CW and pulse current at 135 pC/bunch for FEL operations. The Upgrade DC photocathode gun is a direct evolution of the DC photocathode gun used in the previous JLab 1 kW IR Demo FEL. Improvements in the vacuum conditions, incorporation of two UHV motion mechanisms (a retractable cathode and a photocathode shield door) and a new way to add cesium to the GaAs photocathode surface have extended its lifetime to over 500 Coulombs delivered between re-cesiations (quantum efficiency replenishment). With each photocathode activation quantum efficiencies above 6% are routinely achieved. The photocathode activation and performance will be described in detail.