Beam loss monitor (BLM) systems at ISIS have been designed to protect accelerator components from radiation damage and ensure that activation of the synchrotron is kept low enough to permit hands-on maintenance. The ISIS BLM system uses 3 m and 4 m long Argon-filled ionisation tubes sited along the beam line (at a distance of 2-3 m) in the injector, the accelerator ring and both target beam lines. Repeated radiation damage to a dipole in the accelerator prompted the construction of a scintillator based BLM system to operate alongside the original argon gas system. Twelve plastic scintillators (each 150 x 100 mm) were spaced out along the length of the ceramic vacuum vessel of the dipole. The (blue) light from the scintillators, produced as a result of beam loss, was carried to photomultipliers using fibre optic bundles. The results showed that beam loss patterns could be resolved down to 300 mm and loss not seen by the Argon tubes could be detected and removed.
SJ Payne (ISIS)
Contact: Steve Payne, Steve.Payne@stfc.ac.uk
Research date: May 2008
SJ Payne, SA Whitehead, Proc. of EPAC 2006, Edinburgh