• Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi, A. Takagi
  KEK, Ibaraki
• D. Bayley, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
  STFC/RAL/ISIS, Chilton, Didcot, Oxon
• J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf
  ANL, Argonne
• T. Oki
  Tsukuba University, Ibaraki

A low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by collaboration between Argonne National Laboratory (US), KEK (Japan) and Rutherford Appleton Laboratory (UK). The system has less than 30 Ω of output impedance over wide frequency range of 2.7-6.2 MHz. However, distortions of voltage waveform in the driver stage have been a long-standing issue. It was found such distortions were generated depending upon the higher-order-modes of the anode-choke impedance. In this report, method to realize the smooth sinusoidal waveform in the wideband system is presented.

• E.R. Moog, M. Abliz, K.D. Boerste, T.W. Buffington, D. Capatina, R.J. Dejus, C. Doose, Q.B. Hasse, Y. Ivanyushenkov, M.S. Jaski, M. Kasa, S.H. Kim, R. Kustom, E. Trakhtenberg, I. Vasserman, J.Z. Xu
  ANL, Argonne
• N.A. Mezentsev, V.M. Syrovatin
  BINP SB RAS, Novosibirsk

A number of prototype magnetic structures for a superconducting undulator have been successfully built and tested. The field quality of a test device was measured in a vertical dewar; the phase errors were 7.1 deg. at the maximum design current with no phase shimming. The Advanced Photon Source (APS) specification for overall trajectory was met using the end compensation coils. Several Hall probes have been calibrated at cryogenic temperatures. The design for a cryostat to hold the undulator for installation in the APS storage ring is nearing completion, and a cryogenic measurement facility to measure the magnetic field of the completed undulator is under development.