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Figure 3
Left (cryostat): liquid helium (LH) enters the cryostat via a transfer line. The helium bath is drawn shaded and the level where the temperature is around 4 K corresponding to the vapour pressure of 1 bar of outlet (c) is indicated (arrows 4 K). In the lower region temperatures around the λ transition at 2.17 K are reached by pumping through a needle valve (v1), which is operated from the top with an actuator wheel (w). This region (arrows 2 K) is pumped off via (b) and the temperature gradient is established by the temperature-dependent density. The superconducting magnet (m), which produces a vertical field, is encapsulated in a metal housing and helium is introduced via a helium line (h). A funnel (f) is used during precooling of the magnet. The windows for the horizontal neutron beam are shown with thicknesses of 0.2 mm. Pumping ports (a) serve to pump the liquid helium bath around the sample in the case where it is mounted onto the insert and introduced via the top opening (i) into the tube (t). Right (insert): The sample (s) is mounted in the microwave cavity (cav) attached to the microwave guide, allowing microwaves (µw) to enter from the top. Gaseous helium (gH) enters through a valve, gets precooled, condenses and cools further in the indicated regions (heat exchanger) if placed in the cryostat with the corresponding temperature distribution. The thermal contact takes place via the evaporating helium gas that streams back and leaves the cryostat by pumping on ports (a) on the cryostat drawing. The flow of the liquid 4He is regulated by means of a needle valve (v2).

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