  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.
