Long-Hold-Time Liquid-Helium Dewar for Cooling of a SQUID ELF Antenna.

摘要

An extremely-low-frequency (ELF) receiving antenna that uses superconducting quantum interference devices (SQUIDs) as the sensing elements must be cooled to cryogenic temperatures for proper operation. The simplest and most reliable cooling technique consists of mounting the SQUID sensors in a dewar whose liquid-helium hold time is long enough to exceed the duration of a typical submarine deployment. To verify that such an approach is feasible, a fiberglass dewar capable of fitting into the operational AN/BRA-8 towed communication buoy was procured and tested. The dewar is constructed of fiberglass and uses vapor-cooled shields to achieve a low rate of liquid-helium boiloff. The dewar was designed to hold liquid helium for at least 90 days; an actual hold time of 102 days was measured. No major problems are anticipated in adopting the basic design of the tested dewar to a version suitable for operational use.