Author: Harkay, K.C.
Paper Title Page
TUPPD070 Kelvin Probe Studies of a Cesium Telluride Photocathode for the AWA Photoinjector 1566
  • E.E. Wisniewski, K.C. Harkay, Z.M. Yusof
    ANL, Argonne, USA
  • L.K. Spentzouris, J. Terry, D.G. Velazquez, E.E. Wisniewski
    Illinois Institute of Technology, Chicago, Illinois, USA
  Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for the new Argonne Wakefield Accelerator (AWA) to produce high charge per bunch (~50 nC). Here, we present a study of the "work function" of a cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the surprising effect of UV exposure on the work function, and the puzzling behavior of the work function during and after photocathode rejuvenation via heating.  
TUPPR063 Investigation into Electron Cloud Effects in the ILC Damping Ring Design 1963
  • J.A. Crittenden, J.V. Conway, G. Dugan, M.A. Palmer, D. L. Rubin
    CLASSE, Ithaca, New York, USA
  • L.E. Boon, K.C. Harkay
    ANL, Argonne, USA
  • M.A. Furman
    LBNL, Berkeley, California, USA
  • S. Guiducci
    INFN/LNF, Frascati (Roma), Italy
  • M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the U.S. Department of Energy DE-SC0006506
We report modeling results for electron cloud buildup in the ILC damping ring lattice design. Updated optics, wiggler magnet, and vacuum chamber designs have recently been developed for the 5-GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effect of photon scattering on the interior of the vacuum chamber. Operational implications of the resulting electron cloud buildup will be discussed.
WEPPR084 Measurement of Coherent Damping Rate of the APS Storage Ring 3126
  • C. Yao, K.C. Harkay, H. Shang, C.-X. Wang
    ANL, Argonne, USA
  Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis.