Procedure for preparing the cryostat

1. Before starting cooling the cryostat, pump the isolation vacuum by the vacuum valve to better than 10^-5 mbar. Be sure to use a flexible tube which has NEVER been used for pumping helium.
2. Connect the temperature controller to the regulation socket. Verify that the thermometers indicate the ambient temperature and test that the heating and regulation are working by heating to 310K for example.
3. With all valves closed, connect the cryostat to the He pumping group: recovery valve to the output marked "Bath" and tail pumping line to "Tail".
4. Connect the liquid He level gauge and check the calibration.
5. Flush out the cryostat using pure helium gas from the liquid He dewar, connecting the siphoning port of the cryostat to the gas outlet of the dewar. Close the pressurisation valve and purge the warm and cold valves.
6. Start up the pumping group and pump:
   
   • - the He bath (Bath),
   • - the tail (Tail),
   • - the sample well.
7. Wait 5 minutes, close the valves on the pumping group and assure that there is no pressure rise on the gauge of the pumping group. If the pressure rises, there is a leak in the system. Verify all
   connections and in particular the "0" ring joints.
8. Open the He dewar valve to fill the bath with gas. Open the cold valve of the cryostat and verify that the pressure rises. When the pressure is equal or superior to the atmospheric pressure, switch off the pumping group, open the He recovery valve of the group and the helium counter valve.
9. Connect the liquid nitrogen vessel to the filling port and fill the nitrogen bath.
10. 5 minutes after filling with liquid nitrogen, you may start siphoning.
    
    • - note the He counter reading,
    • - introduce the siphon slowly into the helium dewar,
    • - purge the siphon with helium gas before introducing it into the cryostat,
    • - control the transfer flow by using the pressurization valve so as not to freeze the system up to the helium pumping group.

The cooling of the siphon uses approximately 500ml of helium, 200 to 300 ml are evaporated by the introduction of the siphon. For a transfer of 7 litres of helium the recovery counter should not indicate more than 1.5 m3 of gas.

Procedure for introducing the sample

1. If the temperature is below 10K, change the setpoint to 10K.
2. Connect a primary pump to the sample well and start the pump.
   
3. Turn the 3-way valve in the low position to fill the sample well with helium gas and leave the 3-way vale in the low position.
   
4. Remove the tap and introduce the sample stick into the sample well and pump the well via the 3-way valve in the high position.
5. Close the sample well by turning the 3-way valve with a 1/4 turn (horizontal position).
6. Preview 2cc of exchange helium gas, and introduce it by the same valve. (2cc (1 torr) of exchange gas = the tail of a pressurising bladder).