Check this EVERY TIME before closing the UHV chamber and bake out and cooling down.

Download here PDF version: uhv-he3-stm-check-list.pdf. Every time a major cool down procedure is started, the operators should print out the check list, and go through it carefully. This is STRICTLY NECESSARY, in order to avoid “expensive” mistakes.

Checklist UHV 300mK STM Version 1.7 – modified june 12, 2007

Date:……………………………………………………………………………………

Operator(s):…………………………………………………………………………

Starting position: Insert with scanner and 1K-shield attached is suspended in cryostat. Top flange is closed.

   I.  Scanner, Insert and Cryostat

O Check STM wirings (bias, signal, piezo's, CERNOX thermometer)
O Check HELIOX wirings (thermometers, heater, see manual)
O Connect 1K capillary Swagelok. Don't forget capillary fixing screw (“borgschroefje”).
O Move insert (retract in highest position and extend fully down and retract back). Check for jamming.
O Mount N2 shield such that it does not touch the capillary and the sides. Check again for insert motion and that the insert won't jam the N2-shield doors.
O Pump OVC.

Remarks: ……………………………………………………………………………………………………………………

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   II.	UHV Chamber

O Raise cryostat to its highest position on air-pillars and PUT wooden SAFETY BLOCKS in place.
O Mount water cooling ring and make sure you mount a loop for manual opening of N2 shield doors.
O Put new CF gasket and move chamber under cryostat. Check for wires being sqeezed.
O Remove safety blocks. Lower air-pillars, close chamber and mount suspension blocks.
O Raise again cryostat (air-pillars risen till middle). Remove car.
O Check pre-pump rotation direction and water cooling for turbo.
O Start pumping.

Remarks: ……………………………………………………………………………………………………………………

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III. Bakeout

O Test vertical motion of insert.
O Leak-test flanges that have been changed. Leak-test 1K capillary by flushing helium.
O When pressure is less then 10-4 mbar, open ion pump and all metal valves on sputtering line.
O Remove Pfeiffer P-gauge and QMS-200. Cover windows with foil.
O Mount bakeout panels. Connect heaters and thermometers.
O Degas filaments (RGA, Bayard-Alpert, annealing filament), sublimate Ti and burst ion pump.
O Cool down slowly, regularly degasing filaments. Remove bakeout panels.

Remarks: ……………………………………………………………………………………………………………………

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  IV.	Cool-down to 4K

O Flush needle-valves (both 1K and sock) with He-gas.
O Close needle-valves and apply some He pressure (via return line) on 1K and sock pumping lines.
O Stop pumping on OVC before cooling.
O Fill both N2 and He-tanks with liquid N2. Use restrictor while magnet is above 77 K.
O Blow out N2 from He-bath using N2 gas and pump bath to remove the remanent liquid.
O Flush bath with He-gas and check the flow in the capillaries through the needle-valves. Leave 1K needle-valve open while filling.
O Fill liquid He. Bath should be at overpressure before inserting transfer tube.
O When magnet is cold (~4 kOhm) and liquid He level increases, raise transfer tube a bit and increase pressure on He vessel to 400 mbar.

Remarks: ……………………………………………………………………………………………………………………

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  V.	Cool-down to 300 mK

O Start flow through 1K capillary and sock. Adjust needle valves to match prescribed flow rates.
O When 1K-pot is cold, open 'V1' on he3-dump.
O When pressure in dump does not drop anymore, close 'V1' and set sorb heater above 50K.
O When he3-pot temp. matches 1K-pot, turn off the sorb heater. Re-open 'V1' to condense last He3. NOTE: between measurements, turn on sorb heater and keep 'V1' closed.

Remarks: ……………………………………………………………………………………………………………………

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