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In this mode, you will need to coordinate with the Target Expert on shift regarding the planned duration of time spent in this mode.
This mode will be alternated with the Production Mode during normal operations with microwaves to keep up with the LHe production from the QT system.

Configuration / Things to maintain

MicrowavesOFF
NMRUsually, it should be on "Take Data" (check with the Target Expert on Shift)
Fridge
  • Only the Backing Pump (Rotary Vane pump) should be running, and the rest of the roots pumps should be OFF
  • 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-run-valve and fridge-bypass-valve
    (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
Magnet
  • Ensure the magnet has enough LHe.
  • Ensure Magnet LN2 level is above 50%, if not refill it.
QT System
  • Ensure the purifier LN2 level is above 50%, if not refill it.
  • 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.


Outlet Flows



How to check and control
Fridge8 slm (should be on the PID controlled for maintaining 100 Torr by Auto Control with Pressure) → How to control the Fridge Return flow
Separator       20 slmHow to control the Separator Return flow
Magnet     ~7 (on pressure PID at 0.9 psi)(link to a page)


Other useful instructions:

Steps for Transitioning from the Hold mode to the Production Mode




################# I think the links below are too much information for the Target Operator manual, can be suitable for the target expert manual ####

Conditions

  1. Fridge parameters when the fridge is in Hold Mode
  2. Magnet conditions when the fridge is in Hold Mode
  3. Cryo-control parameters / conditions when the fridge is in Hold Mode
  4. Microwave parameters / conditions when the fridge is in Hold Mode
  5. Target Lifter conditions when the fridge is in Hold Mode
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