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Sample cooling

Warning: for manipulation with LN2 always use protective gloves and glasses!

The sample can be cooled down in the analysis chamber to 100-150 K in 20-60 minutes, depending on the manipulator and sample mounting. Cold sample cannot be transferred using the tranfer rod because the electrical contacts are too fragile at low temperaures. In the preparation chamber the sample cannot be cooled down.

The temperature can be observed on the Eurotherm 3508 unit.


Manipulator cooling

  1. Install the grey LN2 tank at the manipulator inlet and the bottle at the outlet. Carefully cover all connection with thermal insulation.
  2. Fill the tank with about 3 litres of LN2 (i.e. 3 polystyrene jugs) and cover it with the pink cap.
  3. Wait until you reach the desired temperature.
  4. Refill the LN2 tank when needed. The consumption of LN2 is about 1 litre per hour.


Manipulator thawing

  1. Check that LEED, electron analyzer, X-ray source, evaporators etc. are off and that the electropneumatic valve 10 towards the beamline is properly closed.
  2. Disconnect the bottle from the manipulator outlet.
  3. Connect the compressed-air line to the manipulator outlet and slightly open the valve in order to blow out LN2 and humidity. It might take several hours. and high peaks on the pressure in the chamber (10-6 mbar or more) might appear.
  4. You can anneal the sample at 300 K or more in order to help thawing.
  5. You can run some titanium sublimation pump cycles in order to help the pressure to recover.




Refilling the dewar

It is necessary to refill the dewar when no liquid comes out of it anymore. You can estimate the lowering amount of nitrogen from the level of the red float in the viewport of the blue indicator:

  1. Disconnect the flexible hose from the LIQUIDO valve and leave it in the laboratory.
      
  2. Bring the dewar to the refilling station (do not forget to take protective gloves and glasses with you). Place it so that the GAS valve is rotated towards the mesh of the fence of nitrogen storage tanks.
  3. Connect the filling flexible hose to the LIQUIDO valve, only by hand. Slightly loosen the nut, as it must not be fastened.
  4. Check that the release valve is closed. Fully open the outlet vave.
  5. Fully open the GAS and LIQUIDO valves.
  6. Set the timer (TEMPO DI CHIUSURA VALVOLA) to 7 minutes and open the electropneumatic valve by pressing the green button (APRE}. N2 starts to blow out of the GAS valve.







  1. Observe the process by checking the red float of the level indicator. If not full when the 7-min timer closes the valve reopen it by pressing the green button (APRE} again.
  2. When the dewar is full LN2 starts splashing out the GAS valve. Close the electropneumatic valve by pressing the red button (CHIUDE).
  3. Close the GAS and LIQUIDO valves.
  4. Close the outlet valve and open the reelase valve.
  5. Disconnect the filling hose from the LIQUIDO valve. It can be done by a gloved hand if you followed properly step 3.
  6. Bring the dewar back to the laboratory.
  7. Connect back the flexible hose to the LIQUIDO valve, as it was in step 1.
  8. The dewar will pressurize itself in several minutes. If you need LN2 immediately, you can pressurize is manually by the MESSA IN PRESSIONE valve.


Last Updated on Tuesday, 19 May 2020 11:35