A Cryogenic Testbed for Polarization Modulators and Cryogenic Mechanisms

We developed a cryogenic facility to assess the performance of different types of cryogenic mechanisms. The facility can host very large (up to \(\sim {1}\,\hbox {m}^{3}\)) and heavy (up to \(\sim {30}\,\hbox {kg}\)) instrumentation, cooled down below 10 K. The operation of moving components can be visually monitored by means of two webcams looking inside the 4 K volume. In addition a large number of electrical feedthroughs (444 lines) allow the operation of a set of hall and capacitive sensors to measure both the magnetic field, the position of moving devices with an accuracy of tens of microns and their temperatures with an accuracy of few \(\%\). We present the results of the first tests on a large aperture (500 mm diameter) superconducting magnetic bearing for the SWIPE/LSPE experiment currently under test.