The intention is to keep the fridge in production mode for a sustainable polarization study. To perform sustainably polarization studies, we have to keep the polarization at maximum. After reaching maximum polarization, we will turn off the microwave, and when the polarization curve starts decaying down, we will again turn it on. The power cycling of microwaves helps us reduce liquid helium consumption.
For the sustainable polarization studies, the liquid level in the fridge should be at the Heat-Ex bottom and kept there during the Production Mode.
→ What if the Liquid Level drops from the Heat-Ex Bottom:
If the liquid level in the fridge drops from the Heat-Ex bottom, then open the Run valve on the following configurations:
→ When the Microwave Power is OFF:
Keep the run valve at around 0.50 or 0.55 turns when the microwave power is off. Keep watching the fridge sensors, and do not let the liquid above the Heat-Ex Top, which you can monitor from the Heat-Ex Top sensor resistance.
→ What if Heat-Ex Top Resistance Start Rising:
If the Heat-Ex Top resistance starts rising above 1300 Ohm, then start lowering the Run valve turns or close the Run valve at 0.0 turns.
→ What if Heat-Ex Bottom Resistance is still dropping:
If the Heat-Ex Bottom resistance is still dropping even after opening the Run valve at 0.50 or 0.55 turns, open the Run valve at 0.60 or 0.65 to keep the liquid level at the Heat-Ex bottom.
→ When the Microwave Power is ON:
Keep the run valve at around 0.65 or 0.70 turns when the microwave power is on. Keep watching the fridge sensors, and do not let the liquid above the Heat-Ex Top, which you can monitor from the Heat-Ex Top sensor resistance.
→ What if Heat-Ex Top Resistance Start Rising:
If the Heat-Ex Top resistance starts rising above 1300 Ohm, then start lowering the Run valve turns or close the Run valve at 0.0 turns.
→ What if Heat-Ex Bottom Resistance is still dropping:
If the Heat-Ex Bottom resistance is still dropping even after opening the Run valve at 0.65 or 0.70 turns, open the Run valve at 1 or 2 to keep the liquid level at the Heat-Ex bottom. Once the liquid reaches the Heat-Ex Bottom, set the run valve at 0.65 or 0.60, but keep the liquid level at the Heat-Ex Bottom and not let it go above the Heat-Ex Top.
Note: During the Production Mode, the other fridge target parameter configurations are:
- Separator flow set at 20slm
- GV bypass fully closed.
- GV open.
- Root pump boosters are running.
- Fridge pressure is low, around 0.11 torr, and temperature around 1.1 K.