next up previous contents
Next: Poorly Thermalized Cold Mass Up: Trouble During Pre-Cool Previous: Software Triggering   Contents

Poor Circulation

% latex2html id marker 1521
... PT2 cool down normally, while the MC cools {\it very} slowly.}
If the mixture in the pre-cool circuit does not circulate, heat is not carried from the MC plate to the pulse tube. The result is that PT1 and PT2 cool down as usual, but the MC plate cools unbearably slowly.

Possible reasons this might happen include:

Both the compressor bypass being open and a flipped circuit breaker can be seen remotely by looking at the pressure gradient across the compressor while its running. No gradient means no compressor. If you are on site, both of these are easily fixed.

A clog in the pre-cool lines can be diagnosed by warming up, and collecting the mixture. If you see more than the expected pressure in the dumps, there might be a leak. Scrub the mixture (see [sec:maint.scrub.full]§sec:maint.scrub.full).

Jonathan Ouellet 2014-08-26