Fig. 6.

250 GHz microwave channel and rotor details. a) Enlarged view of the probe with selected components shown. A small groove in the vespel drive-tip is filled with a cryogenic epoxy, Hysol EA 9361 (Loctite) to prevent the drive-tip from coming loose at cryogenic temperatures. The epoxy is also used to seal the top of the rotor. The top Kel-F spacer is threaded, providing a simple and safe way to empty and fill the rotor; the epoxy can be removed with a standard epoxy-stripper, while a 0-80 threaded tool threads into the top spacer, providing a grip to pull the spacer out of the rotor. The microwave power is coupled from the HE₁₁ mode of the corrugated waveguide to the sample by launching the microwaves from the waveguide in the form of a free space propagating Gaussian beam. b) a system of mirrors inside the probe-box focuses the beam delivered by the horizontal corrugated waveguide from the gyrotron onto the vertical waveguide leading to the sample. The red lines trace the trajectory of the microwaves.