We have dedicated chip resistors installed at different positions above the nose level to identify the liquid helium level in the fridge. At the nose level, we have a superconducting liquid helium-level probe. The level probe in the nose shows the actual level of liquid helium in the nose, whereas the chip resistors show the liquid helium presence in the following manner:
- Chip resistor resistance shows between ~1000 Ohms to 1200 Ohms, which depicts no liquid helium at that place.
- The chip resistor resistance ranges from above 1300 Ohms to ~1450 Ohms, which depicts the liquid helium at that location.
The attached fridge CAD model shows the installation of chip resistors at different positions in the fridge and the liquid helium level probe.
| Sensor # | Sensor 1-1 | Sensor 1-2 | Sensor 1-3 | Sensor 1-4 | Sensor 1-5 | Sensor 1-6 | Sensor 1-7 | Sensor 1-8 |
|---|---|---|---|---|---|---|---|---|
| Fridge Positions | Baffle Top | Baffle Bottom | Separator Top | Separator Bottom | Heat-Ex Top | Heat-Ex Bottom | Ann-Plate Bar | Ann-Plate Top |
Please see the Target Parameters for the Fridge Sensors:
The Separator Bottom and Ann-Plate Bar are not working in the above target parameters because they show wrong numbers.
Besides that, sometimes, Heat-Ex Top also shows abnormal behavior.