Author: Ruber, R.J.M.Y.
Paper Title Page
TUPB108 Uppsala High Power Test Stand for ESS Spoke Cavities 711
  • R.A. Yogi, T.J.C. Ekelöf, V.A. Goryashko, L. Hermansson, M. Noor, R. Santiago Kern, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  • D.S. Dancila, A. Rydberg
    Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
  • K.J. Gajewski, T. Lofnes, R. Wedberg
    TSL, Uppsala, Sweden
  • R.J.M.Y. Ruber
    CERN, Geneva, Switzerland
  The European Spallation Source (ESS) is one of the world’s most powerful neutron source. The ESS linac will accelerate 50 mA of protons to 2.5 GeV in 2.86 ms long pulses at a repetition rate of 14 Hz. It produces a beam with 5 MW average power and 125 MW peak power. ESS Spoke Linac consists of 28 superconducting spoke cavities, which will be developed by IPN Orsay, France. These Spoke Cavities will be tested at low power at IPN Orsay and high power testing will be performed at a test stand which will be set up at Uppsala University. The test stand consists of tetrode based RF amplifier chain at 352 MHz, 350 kW power and related RF distribution. Outputs of two tetrodes shall be combined with the hybrid coupler to produce 350 kW power. Preamplifier for a tetrode shall be solid state amplifier. As the spoke cavities are superconducting, the test stand also includes horizontal cryostat, Helium liquefier, test bunker etc. The paper describes features of the test stand in details.  
TUPB107 Amplitude and Phase Control of the Accelerating Field in the ESS Spoke Cavity 708
  • V.A. Goryashko, R.J.M.Y. Ruber, R.A. Yogi, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  We report about numerical simulations of the accelerating field dynamics in the ESS spoke cavity in the presence of the beam loading and Lorentz detuning. A slow feedforward is used to cure the Lorentz detuning whereas a fast feedback through a signal oscillator and cavity pre-detuning technique are applied to eliminate the beam loading effect. An analysis performed with a Simulink model shows that a combination of feedforward, feedback and cavity pre-detuning result in a substantially shorter stabilization time of the field voltage and phase on a required level as compared to a control method using only the feedforward and feedback. The latter allows one to obtain smaller magnitude but longer duration of deviations of the instantaneous voltage and phase from the required nominal values. As a result, a series of cavities only with feedforward and feedback needs an extra control technique to mitigate a cumulative systematic error rising in each cavity. In addition, a technique of adiabatic turning off of the RF power in order to prevent a high reflected power in the case of a sudden beam loss is studied.