Irradiation of MSGCs with low-energy neutrons

A large part of the inner tracker of CMS will be equipped with Micro Strip Gas Chambers (MSGCs). In addition to a high MIP rate these detectors also will be exposed to highly ionizing particles (HIP), as well as to a considerable flux of low-energy neutrons. We have performed experiments with neutrons in the energy range of 0.3–2 MeV, which covers the main part of the neutron spectrum prevailing within the CMS tracker volume. By means of time-of-flight a clear discrimination of the detector response to photons and neutrons has been achieved. The most probable neutron energy deposit has been found to be equivalent to 30 MIPs with a conversion probability of ε=10−5. Two MSGCs, one based on bare glass and another on diamond-like coated glass, were irradiated with neutrons at high dose (4×107 n/cm2 s). After an integral dose of 1×1013 n/cm2, equivalent to one LHC-year, no indication of damage could be found.