Performance and Radiation-Tolerance of Honeywell LOHET-II Hall-Effect Sensors

MICE, the international Muon Ionization Cooling Experiment, is a project to design, construct, operate and test a cell of a muon ionisation cooling channel that may be used for a future Muon Collider or Neutrino Factory.<br>The object of the MICE experiment is to take a beam of muons created from protons from the ISIS accelerator hitting a titanium target and to show that it is possible to create a narrow intense beam, using detector techniques from particle physics.The MICE Muon Beamline[1] can be set to deliver beams of either positive or negative muons. This is achieved by physically swapping over the current leads for each of the conventional magnet power supplies. Ensuring the actual operating polarity of the beamline is correctly recorded as a manual step was at risk of error or omission.We have deployed a simple system ("POMPOMs", [2]) for monitoring the operating polarity of the two bending magnets by placing in each dipole bore a Honeywell LOHET-II Hall-effect sensor (SS94A1E) that operates past saturation at nominal field strengths, and thus returns one of two well-defined voltages corresponding to the two possible polarities of the magnet.The environment in the experimental hall is monitored by an AKCP securityProbe 5E system integrated into our EPICS-based controls and monitoring system. We read out the beamline polarity sensors using a voltmeter module, and translate the output voltage into a polarity (or alarm) state within EPICS whence it can be accessed by the operators and stored in the output datastream.This spreadsheet contains the data from the LOHET-II sensor initial characterisation, radiation-tolerance testing, and in-situ performance monitoring[3] programmes.<br>1. "The MICE Muon Beam on ISIS and the beam-line instrumentation of the Muon Ionization Cooling Experiment" Journal of Instrumentation (2012). doi:10.1088/1748-0221/7/05/P050092. J.J. Nebrensky and P.M. Hanlet: "POMPOMs: Cost-Efficient Polarity Sensors for the MICE Muon Beamline" TUPD90 at DIPAC'11 - 10th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators pp. 518-520 (2011)3. H. Nebrensky: "Routine POMPOM sensor test procedure" (2013)