Disclosed herein is a device defining a generally closed volume therein, henceforth known as a “shuttle”, not permanently fixed to a probe or other surface inside the cryostat, into which gas and/or liquid—most preferably helium gas or liquid—can pass into or out of in a controlled and predictable manner. The passage of gas or liquid into the shuttle is preferably via a porous barrier so that sterile conditions can be maintained in the interior of the shuttle.
