In this work we present an elegant solution for a scintillation counter to be integrated into a cryogenic system. Its distinguishing feature is the absence of a continuous light guide coupling the scintillation and the photodetector parts, operating at cryogenic and room temperatures respectively. The prototype detector consists of a plastic scintillator with glued-in wavelength-shifting fiber located inside a cryostat, a Geiger-mode Avalanche Photodiode (G-APD) outside the cryostat, and a lens system guiding the scintillation light re-emitted by the fiber to the G-APD through optical windows in the cryostat shields. With a 0.8mm diameter multiclad fiber and a 1mm active area G-APD the coupling efficiency of the "lens light guide" is about 50%. A reliable performance of the detector down to 3K is demonstrated.
@article{arxiv.1101.3254,
title = {A lens-coupled scintillation counter in cryogenic environment},
author = {A. Stoykov and R. Scheuermann and A. Amato and M. Bartkowiak and J. A. Konter and J. Rodriguez and K. Sedlak},
journal= {arXiv preprint arXiv:1101.3254},
year = {2015}
}