The Effects of Thermal Cycling on Two Light Guide Technologies and Two Readout Technologies in Liquid Argon

In this investigation two light guide technologies and two readout technologies are tested for the effects of thermal cycling in liquid argon (LAr). The two light guide technologies are the technology developed at Indiana University and the technology developed at MIT and implemented at Fermilab. The two readout technologies are passively and actively ganged 12 Hamamatsu MPPCs. The experiment, mounted in the TallBo dewar facility at Fermilab, measured the scintillation light from through-going, minimum ionizing cosmic muons. Thermal cycling of the experiment's components occured when the dewar was drained after five weeks of running, refilled, and then run again for an additional four weeks. The results show that the MPPCs were unaffected by thermal cycling and there is good evidence that both ganged readout technologies were similarly unaffected. Since the experiment showed that there was a clear degradation of the cosmic signal when the LAr was drained and refilled, it is concluded that it was both light guide technologies that were degraded. Quenching of the scintillation light by contaminants and path length differences in the cosmic tracks through the LAr were considered as causes and but did not play a role.