Cryogen-free cryostat for neutron scattering sample environment

High-power closed-cycle 4He cryostat with top-loading sample exchange

“…Attached to the top/warm end of the pumping tube is a DN 50 KF T-piece which itself is connected via a DN 63 ISO-K bellow and a DN 100 ISO-K tube (total length of approximately 4 m) to a hermetic pumping set. The set consists of two roots pumps in series, with nominal pumping speeds of 1000 m 3 /h and 300 m 3 suppressed by decoupling them by means of a commercial DN 160 ISO-K bellow 2 with spring suspension and by attaching all thermal anchors using flexible copper braid straps, e.g. two thermal radiation shields are attached to the corresponding two stages of the PTC.…”

“…The shields each consist of a top aluminum lid with the thermal connection, a bottom aluminum cap, and a 2 mm thick aluminum rolled cylinder covered with a 10-layers super-insulation foil. 3 The pumping tube is thermally anchored to the lids of the shields with rigid copper clamp rings. The cryostat employs a closed cooling cycle using helium gas -currently we are using only 4 He.…”

“…In recent years significant progress in the field of dry refrigerator systems has been made, for instance by Godfrin [1,2], Kirichek [3,4], Uhlig [5,6,7], and Wang [8,9] together with their respective co-workers. In the meantime, some of these and similar systems have become commercially available and are now in use in many laboratories employing low temperatures world-wide.…”

A fast-cooling sample-positioning probe for low-temperature neutron scattering experiments

“…In particular, 'top-loading' cryostats, which use an exchange gas to thermalize the sample, are widely used as they allow faster and simpler sample changes compared with 'bottom-loading' cryostats which require that the refrigerator be warmed to ambient temperature and vented to atmosphere. Finally, by combining aspects of these two designs, closed-cycle cryostats can also incorporate a pumped gas flow loop (Chapman et al, 2011) to achieve cryogen-free operation and the ability to reach a base temperature of 1.5 K for extended periods, but with the caveats of a much lower cooling power and thus longer system cool-down time, and a more complicated setup. 'Wet' cryostats with a liquid helium bath, such as the 'orange cryostat' (Brochier, 1977) as shown in Fig.…”