First Cool Down for ORANGE-Cryostat

Legend


0. Evacuate outer vacuum container (OVC)

  1. Connect turbo pump to vacuum valve (4)
  2. Evacuate connected tube below p = 10-4 mbar
  3. Open vacuum valve (4) (~ five complete rotations)
  4. Pump OVC at least for 1h (better is over night) p < 10-6 mbar
  5. Close vacuum valve (4) and replace vacuum tube to TP with a KF 25 blank flange.

1. Rinse Cryostat with GHe      

  1. Prepare GHe supply to be connected to Helium recovery line (below ball flow meter), do NOT connect yet
  2. Close V3 and V5; open V1, V2 and V4.
  3. Open needle valve (5), Close warm valve (6), 3-way X-gas valve (blue lever, 15) in straight up position.
  4. Open evaporator valve (7) and Helium overpressure valve (red lever, 11).
  5. Insert cryostat part of the transfer line into the cryostat Helium fill port (9) up to the bottom of the helium tank.
  6. Switch on helium pump and pump out until you reach p< 1 mbar (DIAVAC).
  7. Close V4.
  8. Connect GHe supply to Helium recovery line (below ball flow meter); fill GHe into cryostat until safety valve of the LHe-port opens up.
  9. Interrupt GHe supply; open V4 and pump out until p < 1 mbar (DIAVAC).
  10. Repeat procedure (1.6- 1.8) twice; afterwards close needle valve (5).

2. Check GHe-Flow through needle valve and evaporator

  1. Close V4 and fill GHe into cryostat until safety valve opens up (as in 1.8).
  2. Interrupt GHe supply; Check that V2 is open, Check that evaporator valve (7) is open, open (slowly) needle valve (5).
  3. Optimal GHe-rate of flow results in approximately p = 10-15 mbar (DIAVAC).
  4. Close needle valve (5); continue pumping via V2 for p < 1 mbar (DIAVAC).
  5. Close evaporator valve (7) or/and V2.

3. Rinse Sample Tube with GHe

  1. Check that V4 is closed; fill GHe into cryostat until safety valve opens up (as in 1.8).
  2. Interrupt GHe supply; Open V3.
  3. Open sample tube X-gas valve (16); 3-way X-gas valve (blue lever, 15) must be straight up.
  4. Pump out sample tube until p = 0 mbar at X-gas pressure gauge (14) (EDWARDS 25 mbar capsule gauge).
  5. Close sample tube X-gas valve (16)
  6. Turn straight down 3-way X-gas valve (blue lever, 15) for GHe-recovery line; fill sample tube with p = 1 atm GHe (down position of 3-way X-gas valve (blue lever, 15) for approx. 3 s, not visible on X-gas pressure gauge (14).
  7. Repeat procedure (3.3-3.6) twice; adjust to approximately p = 15 mbar for cool-down with sample tube by carefully open sample tube X-gas valve (16).
  8. Wait for two minutes and check that pressure is not increasing. If pressure is increasing by 1 mbar or more check all O-rings and clamps on sample tube and sample stick.

4. Fill cryostat with LHe and LN2and Cool Down to T < 4 K

  1. For a last time: Check that V4 is closed; fill GHe into cryostat until safety valve opens up (as in 1.8); disconnect GHe supply from Helium recovery line.
  2. Open carefully V5; check that Helium overpressure valve (red lever, 11) is open.
  3. Check that cryostat part of the transfer line is inserted into the cryostat (LHe-Port, 9) up to the bottom of the helium tank.
  4. Prepare LHe-vessel and have GHe return and GHe supply tubes at hand. Please wear your protective gloves and goggle.
  5. Insert LHe transfer syphon slowly into LHe-can.
  6. Wait approximately 30 sec for the air-GHe-exchange in transfer line; then insert transfer line into the cryostat part.
  7. Open V2, evaporator valve (7). Adjust needle valve (5) to a pressure of
    - approximately p = 100 mbar (DIAVAC) for an immediate cooldown or
    - approximately p = 15 mbar (DIAVAC) for insert the sample later.
  8. Transfer LHe with approximately p = 0.1 - 0.2 bar.
  9. During begin of LHe transfer, start transfer of LN2 into cryostat Nitrogen fill port (8) (duration approximately 5 min).
  10. Close Nitrogen fill port (8) with rubber stoppers after LN2-transfer.
  11. LHe is collecting in the cryostat after approximately 10 min and LHe-level meter shows increasing height (adjust length of probe at 16 inch = 40.6 cm!).
  12. Adjust needle valve (5) until approximately p = 100 mbar (DIAVAC) is reached.
  13. Stop LHe-transfer at H = 35 cm.
  14. Pull out LHe transfer syphon; close Helium fill port (9); close Helium overpressure valve (red lever, 11).
  15. T_regulation and T_sample decrease (with approximately p = 100 mbar (DIAVAC)); from 300 K with about 0.5 K/sec and from 150 K with about 5 K/min.
  16. For T < 50 K, close needle valve (5) slightly until approximately p = 30 mbar.
  17. After approximately 2h T = 4 K should be reached and needle valve (5) should be adjusted to approximately p = 2 - 5 mbar.