Hold Mode

• Only the Backing Pump (Rotary Vane pump) should be running, and the rest of the roots pumps should be OFF
  See Roots pumps PLC interface page
• Maintain the fridge LHe level between 50% and Heat-Ex Bottom. In other words, let the fridge level drops down to 50% and then refill it up to Heat-Ex Bottom by opening the run-valve (then close it).
• The fridge pressure should be on PID control at 100 Torr (see the table below).
• Adjust the fridge RUN/Bypass valve between 0.5 turns (for a slow fill) or 2 turns (for a relatively quick fill), and close it when the fridge fill is complete and continue to monitor the fridge level and refill when the level reaches back to 50%.
  See these links
  (a) How to Open or Close Fridge Valves
  (b) How to identify the fridge LHe level is at Heat-Ex Bottom
  
• Discuss with the Target Expert when to switch from the Hold Mode to the Production Mode: Transitioning from the Hold mode to the Production Mode

• Ensure the magnet has enough LHe.
• Ensure Magnet LN2 level is above 50%, if not refill it.

• Ensure the purifier LN2 level and the magnet shield LN2 levels are above 50%, if not refill it.
  See Helium Liquefier (QT) System Summary page to identify where to look at for those LN2 levels.
• Ensure both liquefiers produce LHe with the rate of ~ 4 L/ hr (with an uncertainty +/- 0.3). If not, then contact the Target Expert on shift. You can use https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/target-LHe-prod-rate.php
• Check LCW outlet Temperatures from the cold-head compressors and ensure all those temperatures are below  95 F. If any of those are. > 100 F then, report to the Target Expert immediately and follow Target Expert's instructions.

Check with the Target Expert among the following options:
(1) Set the gv-bypass PID controlled for maintaining 570 Torr by Auto Control with Pressure
(2) Fully open gv-bypass