High Sensitivity HEH Monitor

The most critical failure mode of HV semiconductors exposed to radiation is Single Event Burnout (SEB). The probability of this catastrophic failure mode is strongly dependent on the applied bias voltage and is triggered by either heavy ions or High Energy Hadrons (HEH). The Large Hadron Collider (LHC) Beam Dumping System (LBDS) comprises 50 pulse generators operating at up to 28 kV and contains 800 HV GTOs and 480 HV IGBTs for the triggering system. All generators are installed underground in the galleries parallel to and shielded from the LHC tunnel but some HEH leak from the tunnel into the galleries via interconnecting cable ducts. Failure of a HV semiconductor due to SEB can lead to system malfunction and potential deterioration of downstream equipment. Shielding of the cable ducts has been done in the past, HEH flux is most likely well under 106HEH/cm2/year, and therefore below the sensitivity of presently used neutron SRAM SEU monitors, showing zero counts until now. Future operation with increased beam energy will result in increased voltage applied to the GTOs and consequently higher SEB probability. In order to improve the accuracy of the failure rate estimation necessary for preparing mitigation measures, more sensitive HEH flux measurements are necessary.