• A. Warner, K. Carlson, L.R. Carmichael, J.L. Crisp, R.W. Goodwin, L.R. Prost, G.W. Saewert, A.V. Shemyakin
  Fermilab, Batavia

Abstract The Fermilab Recycler ring employs an electron cooler to store and cool 8.9-GeV antiprotons. The cooler is based on a 4.3MV, 0.1A, DC electrostatic accelerator (Pelletron) for which current losses have to remain low (~10^-5) in order to operate reliably. The Machine Protection System (MPS) has been designed to interrupt the beam in a matter of 1-2 μs when losses higher than a safe limit are detected, either in the accelerator itself or in the beam lines. This paper highlights the various diagnostics, electronics and logic that the MPS relies upon to successfully ensure that no damage be sustained to the cooler or the Recycler ring.

• M. Bousonville
  GSI, Darmstadt
• J. Rausch
  TUD, Darmstadt

Most timing systems used for particle accelerators send their time or reference signals via optical single mode fibres embedded in cables. An important question for the design of such systems is how fast the delay changes in the fibre optic cable take place, subject to the variation of the ambient air temperature. If this information is known, an appropriate method for delay compensation can be chosen, to enable a phase stabilised transmission of the timing signals. This is of interest particularly with regard to RF synchronisation applications. To characterise the velocity of the delay change, the delay behaviour after a sudden temperature change will be described. When trying to determine the step response, two problems occur. On the one hand, the material parameter of the coating, necessary for the calculation, is typically unknown. On the other hand, the measurement of the step response under realistic conditions is very laborious. Thus in this presentation it will be shown how the step response and, accordingly, the velocity of the delay change in a fibre optic cable can be calculated by means of theoretical considerations, utilizing the typical geometry of fibre optic cables.

• J. Harasimowicz
  Cockcroft Institute, Warrington, Cheshire
• J. Harasimowicz, C.P. Welsch
  The University of Liverpool, Liverpool

The Ultra-low energy Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) at GSI, Germany will decelerate antiproton beams of very low intensities from 300 keV down to 20 keV. Such beams can be easily disturbed by standard monitoring devices and the development of new sensitive diagnostic techniques is required. To overcome the limitations related to a very low number of particles, a low signal-to-noise ratio and ultra-low kinetic energies, a resonant capacitive pick-up has been proposed as a beam position monitor. In the planned solution, the signal gain will be realised by the use of a specially designed resonant circuit optimized to meet the requirements of the USR. The current overall design studies of the resonant capacitive pick-up, including simulations of the beam displacement sensitivity and linearity for different pick-up geometries and the equivalent resonant circuit optimisation, will be discussed.