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Single Shot Test

A single shot test will tell you how much $ ^3$ He there is in the mix. It takes advantage of the fact that during the dilution cycle the $ ^3$ He is circulating and the $ ^4$ He is more or less stagnant.

Start this test while the system is $ \lesssim50$ mK. Close V1 and open V4. This will divert the $ ^3$ He from being pumped back into the MC and into the dumps. The fridge will continue to stay cold for the duration of the test. When the $ ^3$ He runs out, the cooling power drops, and the MC temperature will spike and hold around $ \sim300$ mK, the pressure in the dumps will rise much more slowly until the $ ^4$ He runs out as well.

The value of P1 when the slope decreases suddenly and the temperature rises rapidly, gives the amount of $ ^3$ He in the system.

To end this test, you should collect the rest of the mixture.



Jonathan Ouellet 2014-08-26