Cryosampler interface

A package that permits the electrical coupling of a cryosampling system with a high temperature device has been constructed and tested. The Faris sampling system has demonstrated 5 ps time resolution and 10 μV sensitivity. The interface couples the sampler at 4.2 K to a higher temperature region, with minimal heat transfer, by means of low inductance contacts to a high quality 50 ohm thin-film transmission line. Initial time domain reflectometry tests using the sampler have been carried out over a range from liquid helium temperature to 210 K. Five reflections have been observed of a step initiated and detected by the sampler at the low temperature end and traversing a 14 cm path to the high temperature end and back, No more than 20 ps was added to the pulse risetime for one roundtrip and signals on the order of 100 μV were detected, We expect to improve this performance and to use the system for experiments on superconductors, gallium arsenide, and semiconductor devices.