Radiation induced Single Event Effects in the ATLAS MDT-ASD front-end chip

Single Event Effect (SEE) tests of the MDT-ASD, the ATLAS MDT front-end chip have been performed at the Harvard Cyclotron Lab. The MDT-ASD is an 8-channel drift tube read-out ASIC fabricated in a commercial 0.5um CMOS process (AMOS14TB). The chip contains a 53 bit register which holds the setup information and an associated shift register of the same length plus some additional control logic. 10 test devices were exposed to a 160 MeV proton beam with a fluence of 1.05E9 p.cm-2.s-1 up to >4.4E p.cm-2 per device. After a total fluence of 4.46E13 p.cm-2, 7 soft SEEs (non-permanent bit flips in the registers) and 0 hard/destructive SEE (e.g. latch-ups, SEL) had occurred. The simulated fluence for 10 years of LHC operation at nominal luminosity for worst case location MDT components is 2.67E11 h.cm-2. The rate of SEUs in the ASD setup register for all of ATLAS, derived from these numbers, is 2.4 per day. It is foreseen to update the active registers of the on-detector electronics at regular intervals. Depending on the length of the update intervals, the SEU rate is very manageable and will not cause any significant degradation in performance of the ATLAS muon detector. The worst case impact of one SEU is the loss of eight channels out of 360.000 for the time of one update interval and occurs with a rate of ~ 1 per month.