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Ph.D. Thesis - Physics

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Appendix C<br />

How to trap ions in a closed-cycle<br />

cryostat<br />

The purpose of this appendix is to offer a practical guide to the operation of the 4 K<br />

closed-cycle cryogenic ion trap presented in Sec. 7.4. We will present the following items:<br />

• Preparing the cryostat for cooldown.<br />

• Turning on the compressor.<br />

• Pressure and temperature measurement.<br />

• Laser alignment and imaging.<br />

• Shutdown<br />

This appendix will be most useful after reading Sec. 7.4, which contains the basic de-<br />

scription of the cryostat system.<br />

C.1 Preparing the cryostat for cooldown<br />

The cold head (expander) may be mounted in one of two configurations. In the first config-<br />

uration, the cold head is held above the DMX-20 anti-vibration system using four spacers<br />

with bolts that are tightened down. In this position, the cold head is decoupled from the<br />

overhead support structure, and may be rotated up and opened. In the other configura-<br />

tion, the cold head is attached to the overhead structure using four aluminum plates; in this<br />

position, the cold head is vibrationally isolated from the vacuum housing of the experiment.<br />

Before engaging the compressor, which starts the cooldown, it is important to flush and<br />

fill the bellows of the DMX-20 with ultra-high purity (UHP) helium, which is 99.9999%<br />

pure. The recommended procedure is as follows:<br />

241

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