Cryostat Mounting

1. Kinematic mount. The cryostats are attached to instruments using a kinematic mount, this mount constrains the six degrees of freedom to ensure mounting stability and repeatability. The mount on the cryostat side consists of 3 ball capstans, on the instrument side the mount consists of a cone, a vee and a flat.

For the kinematic mount to work the capstan clamps must be tightened in this order 1. cone 2. vee 3. flat. 

The capstans are locked with an allen bolt, these must be slackened off using a 3mm allen key to be able to rotate them. It must be tightened again afterwards.

At times it is possible to rotate the capstans without releasing the clamps, this is especially useful when making initial adjustments, for a final check reclamping is recommended.

The capstans have a 1/2 inch whitworth thread, 40 tpi. This means a single rotation of a capstan will give a linear movement of 25 thousandths of an inch. (0.635mm)

2. Micrometers. For the micrometers to give the correct reading they must be fully pushed home, the shoulder of the micrometer must be pushed hard against the faceplate. If this is not the case the allen bolt used to clamp the micrometer must be slackened off with a 2.5 mm allen key to be able to push it home, it must be tightened again afterwards.

At times it is convenient to change the orientation of the micrometer to make it easier to read, there is no problem with this providing it is correctly pushed against the faceplate.

A single rotation of the micrometer gives a change in reading of 0.5mm, the smallest units displayed are 0.01mm

3. Isolation. The SDSU detector systems require a single earth through controller power supply mains cable, both SDSU controller and the cryostat must be electrically isolated from the instrument. Failure to do so will cause an earth loop that more often than not will cause increased noise on the detector.

The easiest way to short the cryostat to the instrument is by leaving the micrometer touching the instrument after a reading, the micrometer must always be left wound away from the instrument.

With some instruments it is also possible to short the cryostat to the instrument via the capstans. Some clamps have rubber boots or insulating tape, if these come off then they should be replaced.

4. Capstan Clamp Adjustment It should not normally be necessary to adjust a capstan clamp. If a clamp feels excessively tight it may well be that the cryostat is not correctly seated. A slightly misplaced cryostat with either the Cone or Vee capstan incorrectly seated will result in a clamp that is very difficult to close. Excessive use of force may damage the clamp, even if the cryostat is focused under these conditions the micrometers readings will be useless for the next run.

If a clamp must be adjusted then a small adjustable spanner will be needed. The clamp is a simple nut and bolt (2 nuts for some clamps ), slacken of the nut(s) and adjust the bolt, then tighten the locking nut(s). Ensure that the clamp is sufficiently tight, a loose clamp risks the cryostat falling off the instrument.



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