When the fridge is in Hold Cold Mode, it means we have a liquid in the fridge nose and holding target material. In that case, we must keep the target material to preserve the paramagnetic centers. In the Hold Cold Mode, you will see the fridge parameters as follows:
We fill the fridge to Heat-Ex Top for the Cold Hold Mode and close the Run and Bypass valves. To reduce LHe consumption in the fridge nose, set the GV bypass opening at 8.1% at the lowest opening to keep the fridge pressure flat. pressure on PID at 100 torr and Set the Separator flow at 20slm.
Keep monitoring the target parameters, say Insert#7, Insert #8, Annealing A, and Annealing B. Where Insert #7 and Insert# 8 are the Cernox (CX-1030) sensors on the Top and Bottom cup of the target insert. Where Annealing A and Annealing B are the metal temperature in the fridge, monitor these four target parameters. Where Insert#7 and Insert# 8 are in resistance (Ohm) and Annealing A and Annealing B are in temperature (K). Please see a screenshot below for these target parameters:
You can see below the conversion table for the Cernox (CX-1030) from resistance to temperature.
- Run and Bypass valves are closed.
- Separator Flow set at 7slm
- The GV bypass can be set at 8% or fully open. It does not matter what the GV bypass opening is.
say Nose LHe Level (%), when it comes to 50% then start filling the filling and replenish the level at Heat-Ex bottom.
Please follow this page to put the fridge in the Cold Hold Mode: Cryo-control parameters / conditions when the fridge is in Hold Cold Mode - Wiki Post Portal - Confluence (virginia.edu)You can see the Fridge Parameters on the Strip Charts Fridge 2x3 (fnal.gov):