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 x 107 n/cm2 s). After an integral dose of 1 x 1013 n/cm2, equivalent to one LHC-year, no indication of damage could be found. (author)