Transcript JANIS CYROSTAT COOLING DOWN PROCEDURE MBE Optoelectronics Group

JANIS CYROSTAT COOLING
DOWN PROCEDURE
MBE Optoelectronics Group
Operation Procedures
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1. Outside jacket of Dewar pump down
2. He reservoir pre-cooling
3. Liquid Nitrogen transfer
4. Liquid Helium transfer
5. Sample cooling
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Reference
• 1. Operating Instructions for the Janis Model SVT
Research Cryostat, Operation Manual
• 2. Manual for the photoluminescence measurements in the
18-132A laboratory, UCLA
• 3. Cool-Down Procedure for 8-CNDT Optical Cryostat, 728-99, Greg Martinez
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Outside jacket of Dewar pump down
• 1. Make sure there is not water in He or LN2 reservoirs
• 2. Evacuate the vacuum jacket.
• The recommended room temperature vacuum level is 10-5
Torr[1],(10-6Torr[2]), so a diffusion pump or a turbo pump is
necessary.
• Based on Dr. Skromme Lab’s setup, a minimum vacuum
level: 1-2mTorr is required for a stable liquid Helium
super-flow.
• Our case: vacuum<5 mTorr
• Baking over 50°C is not allowed by manufacturer
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Outside jacket of Dewar pump down
To Sample tube
To Dewar jacket
To Pump
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Outside jacket of Dewar pump down
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He reservoir pre-cooling
• 1. Pump liquid He reservoir and backfill with
Helium gas
• 2. Pump sample tube and backfill with Helium gas
– Make sure needle valve is not obstructed
– Close the needle valve loosely before the liquid
nitrogen transfer
• 3. Unseal the He venting arm then transfer liquid
nitrogen to He reservoir
• Step 1 is not very necessary, purging with gas
Helium will be enough[3]; Close Dewar vacuum
valve before liquid nitrogen transfer
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He reservoir pre-cooling
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He reservoir pre-cooling
He pumping arm
Liquid Nitrogen
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He reservoir pre-cooling
• 1. Open the liquid Helium valve 2 to 3 turns
while filling the reservoir, make sure the
valve does not freeze.
• 2. Turn off the LN2 switch and immediately
begin to thaw the pumping arm with the
heat gun before resealing it.
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He reservoir pre-cooling
Needle valve
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He reservoir pre-cooling
Thaw the pumping arm
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He reservoir pre-cooling
Seal the liquid Helium
pumping arm
Insert rubber stoppers into the
two/vent ports to prevent air
and moisture from entering
the LHe reservoir
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Liquid Nitrogen Transfer
He gas adapter
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Liquid Nitrogen Transfer
Connect Helium gas to
Helium fill/vent port
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Liquid Nitrogen Transfer
U tube
He siphon tube
adaptor(with O-ring)
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Liquid Nitrogen Transfer
Nitrogen fill/vent
port
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Liquid Nitrogen Transfer
Apply gas He to press liquid nitrogen to LN2 reservior
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Liquid Nitrogen Transfer
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Liquid Nitrogen Transfer
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Liquid Nitrogen Transfer
Rubber stopper
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Liquid Nitrogen Transfer
Fill liquid Nitrogen to
LN2 reservoir
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Liquid Nitrogen Transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Liquid Helium transfer
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Sample Cooling
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