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Q:
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What are the degrees per turn for the SCM-1 rotator?
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A:
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4.925 degrees per turn for SCM-1.
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Q:
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When running the Lambda Fridge what is the maximum rate that will limit eddy current?
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A:
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1.5 amps/minute.
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Q:
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What is the base operating temperature for SCM-1?
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A:
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About 20 mK.
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Q:
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What is the available sample space for the SCM1 probes?
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A:
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25 mm.
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Q:
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How long does it take to reach base temperature once the probe is fully loaded?
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A:
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After the probe is fully loaded and mK personnel have started circulation, base temperature should be achieved in four hours. It takes rough two hours to load a probe and any additional time users may want to slowly cool their sample.
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Q:
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Is the user allowed to adjust the gas handling system?
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A:
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No. Only mK personnel are allowed access to the gas handling system and the associated software.
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Q:
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What is the temperature of my sample?
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A:
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The mixing chamber temperature is a good indicator of the sample temperature. The mixing chamber thermometer is located within a half inch of the sample. However, local heating can occur from measurement techniques, i.e., passing excessive current through the sample contacts and sample.
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Q:
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How do I control the mixing chamber heater?
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A:
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First notify mK personnel before putting heat into the mixing chamber. The mixing chamber heater is controlled two ways. First, through the gray box labeled "IBM D.R.", pins 17 and 18, using a current source. The maximum amount of current is 8.0 mA. Secondly, through the GPIB bus, using system software, the maximum temperature amount is 650 mK. There is a chart that reflects heat load verses mixing chamber temperature for reference in the mK facility.
Tmax Main Heater = 650 mK
Imax Flow Diverter = 8.0 mA
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Q:
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I have a powder sample. In my proposal (AC susceptibility experiment) I stated, "that we could get a sample of about 10g", but I believe that much less is needed. What are the sample holders like, and how much sample do they hold?
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A:
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You will get best sensitivity if you fill out the space inside one of the coils. This space is a cylinder with 0.1" in diameter and 0.25' in length. It is the volume estimation, please, do the mass estimation yourself. It is better to have extra material for a case of accident during a sample preparation. You should increase your final estimation to 3-5 times, if you do not have problems with the powder preparation. The powder has to be placed in a nonmagnetic container that will fit the coil. The nonmagnetic container we use is a gelatin capsule. It has about 1 mm in diameter and 5 mm in length. You are welcome to use Magnet Lab capsules or make your own container, if you would like to do so. You have to be sure that the container will not open accidentally inside our cryostat.
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Q:
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One of the things we would like to do is the specific heat of a sample exactly at the metamagnetic transition field (20 T) to extend some data we took at 3He temperatures earlier. Is there any chance of doing that, or is getting the magnet to 20 (Lambda Fridge) too big a deal?
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A:
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We can start the lambda frig first thing in the morning and have it ready to get to field 2-3 hours later. Your maximum ramp rate will be reduced from 0.6 T/min to 0.23T /min. The magnet itself generates eddy current heat. We don't run the Lambda Fridge on the weekend because it takes extra helium and a little looking after while running.
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FAQ: SCM1/Probes