Condition

• The magnet already contains LHe, i.e. the magnet LHe level > 0%.
• The fridge valves (i.e. run and bypass valves) are fully closed.
• You can access the QT HMI and the Cryo Control Panel (CCP).
• You can access the strip charts on the data-summary page, particularly these preset pages;
  
  • Transfer-Line Cool Down:  https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/cool_down.php
  • LHe Transfer:  https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/transfer.php

Procedure

Steps 3 will take a long time.  You have to start the procedure well in advance in order to make carry out step 4 at the time you need.

1. Select a QT liquefier ("Liq") for the magnet filling.  Liq should contain at least 200 L of Helium.
2. Change the mode of Liq to Auto + Idle.
3. Change the pressure set point of Liq to 42.0 5 psi.  It will take >1 hour for the pressure to go down to the set point.
4. Start to cool down the transfer line by opening VPC and VJVAVJVA/B.
   1. This is the start time of the transfer.  Record the time, the magnet level and the Liq level.
5. Monitor TX1 and wait until it reaches below 100K and becomes flat (for ~10 5-10 minutes). 
   1. Usually TX1 first rises slightly (by 1-2 K).
6. Disable the auto control of the MagRetBypass valve. , using "MagRetBypass_Main.vi" in CCP.
7. Open the MagRetBypass valve fully.
8. Open VJVT and close VPC.
9. Change the mode of Liq to Manual + Idle.
10. Close SVNA/B (outlet valve).
11. Open SV501A/B (inlet valve).
12. Set FC501A/B at 60 SLM.
    1. If the actual inflow (FC501A/BI) is lower than its set point (FC501A/BQ), change the mode of the other liquefier to "Idle" so that PT501A/B rises.
13. Turn off all the five cold heads of Liq. 
    1. Confirm that the pressure of Liq is increasing.
    2. If it isn't, turn on all the five heaters of Liq until the pressure differential (between Liq & Mag) becomes 3.0 psi.  Then turn them off.
14. Wait until the pressure differential (between Liq & Mag) becomes 3.5 psi.
    1. Usually the magnet pressure (PTMR3) goes up to 2.0 psi and then down slowly to 1.5 psi.
15. Set FC501A/B at 55 SLM.
16. Maintain the pressure differential at 3.0-3.5 psi, by adjusting FC501A/B.
    1. Usually you change FC501A/B with a step of 5 SLM down to 40 SLM (i.e. 50 → 45 → 40 SLM).
    2. You have to increase FC501A/B when the pressure differential becomes smaller than 3.0 psi.
17. Keep until the magnet level reaches 40% (135 L).
18. Close VJVA/B.  Open VPC.  Close VJVT.
    
    1. This is the end time of the transfer.  Record the time, the magnet level and the Liq level.
19. Enable the auto control of the MagRetBypass valve.  Change the set point to 1.5 psi if needed.
20. Turn on all the five cold heads of Liq. 
21. Wait until the cold-head temperature becomes <10 K.
22. Change the Liq settings as follows:
    1. The pressure set point is the original value that was set before you started this procedure.
    2. The outlet flow is 40 SLM.
    3. The Liq mode is Auto + Liquefy.
    4. If you change the mode of the other liquefier, change it back to Liquefy.
23. Wait until the inlet flow becomes 60 SLM (i.e. max).
24. Lower the outlet flow to 30 SLM and wait until the inlet flow becomes 60 SLM.  If the Liq pressure goes up, increase the outlet flow and wait until the pressure goes down.
25. Repeat step 23 with outlet flow = 20, 10 and 2 SLM.
26. Confirm that the Liq pressure stays around the set point.

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