FRIB, East Lansing, Michigan, USA
Modern hadron accelerators create and transport beams that carry MW-scale power or store GJ-scale energy. The Machine Protection Systems (MPS) that guard against both catastrophic failures and long-term performance degradation must mitigate errant beam events on time scales as short as several microseconds. Measurement systems must also cope with detection over many orders of magnitude in beam intensity to adequately measure and respond beam halo loss. Other issues, such as radiated signal cross-talk, also confound and complicate delicate measurements. These requirements place enormous demands on the MPS beam diagnostics and beam loss monitors. We will review the current state of MPS diagnostic systems for this class of accelerator, including SNS, ESS, FRIB, LHC, J-PARC, and SPIRAL-II. Specific designs and key performance results will be presented and discussed.
FRIB, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
As a follow-up study to the initial design of FRIB Loss Monitor Ring (previously named Halo Monitor Ring [1]), we present recent results of coupling studies between the FRIB CW beam and the Loss Monitor Ring (LMR). While a ~33 kHz low-pass filter was proposed to attenuate high-frequency AC-coupled signals [1,2], the LMR current signal may still contain low frequency signals induced by the un-intercepted beam, for example, by the 50μs beam notch that repeats every 10ms. We use CST Microwave Studio to simulate the AC response of a Gaussian source signal and benchmarked it to analytical model. A circuit model for beam-notch-induced AC signal is deduced and should put a ~33pA (peak) bipolar pulse on the LMR at 100Hz repetition rate. Although its amplitude falls into our tolerable region, we could consider an extended background integration to eliminate this effect.
FRIB, East Lansing, Michigan, USA
LBNL, Berkeley, California, USA
Recently, Jolly et al. presented an analysis of the rms emittance measurement errors from a first principles approach [1]. Their approach demonstrated the propagation of errors in the single-plane rms emittance determination from several instrument and beam related sources. We have extended the analysis of error propagation and estimation to the fully correlated 4-D phase space emittances obtained from pepperpot measurements. We present the calculation of the variances using a Cholesky decomposition approach. Pepperpot data from recent experiments on the NDCX-II beamline are described, and estimates of the emittances and measurement errors for the 4-D as well as the projected rms emittances in this coupled system are presented.
[1] S. Jolly, et al., “Data Acquisition and Error Analysis for Pepperpot Emittance Measurements”, Proceedings of DIPAC ’09, WEOA03.