Compact cryogenic hydrogen test environment for small devices and material characterization

Currently, there is a great need for testing capabilities for material samples and components in LH 2 . This includes low temperature compatibility at 20 K, H 2 compatibility and potential degradation or permeation effects. The test environment required for this is challenging and quite costly due to LH 2 supply. Therefore, an alternative test concept was developed whereby the required amount of LH 2 (typically 2–3 L) is generated directly on-site by simple condensation. This is achieved with a power-controlled cryocooler (115 W @ 80 K, 18 W @ 20 K). A cylindrical pressure vessel with an inner diameter of d = 109 mm and a length of approx. 500 mm designed for 2.1 MPa is used to hold the LH 2 bath and the samples. The cryocooler and the sample chamber are installed in a common vacuum cryostat and are thermally coupled at the lower end. At the 20 K level, thermal coupling is achieved by a sophisticated thermosiphon arrangement. Hydrogen is taken from a pressure reservoir, pre-cooled at the cryocooler 80 K level, and then injected and liquefied within a couple of hours.