MuSR: 3He Fridge decide whether we are using the 1K Pot or He3 Pot Lo sensor

As a MuSR user or scientist, I would like to be able to distinguish whether we are using the 1K Pot or He3 Pot Low-Temperature sensor.

On the 3He Fridge we have 3 ports for sensors 1 is always connected to the Sorb sensor, another always to the He3 Pot High-Temperature sensor. The third is switched between the 1K Pot and He3 Pot Low-Temperature Sensor. Currently, we are defining the sensor as the 1KPOTHE3POTLO sensor and on the diagram, we are always pointing this to the 1K Pot. Cryogenics and the scientist identified this as having caused problems in SECI and said that we can differentiate which sensor we are using by the temperature reading given with the suggestions: IF 1KPOTHE3POTLO < $(Macro=1.4K) THEN 1KPOT = ‘Not Attached’.

This ticket is to separate 1KPOTHE3POTLO into 1KPOT and HE3POTLO PVs in the IOC. The IOC should defined when these are valid by the temperature readings as suggested above and the diagram should point to the 1K Pot or He3 Pot Lo at the relevant times.

Acceptance criteria:

- 1KPOTHE3POTLO is split into 1KPOT and HE3POTLO PVs in the IOC
- IOC defines when 1KPOT and HE3POTLO are valid by the temperature readings as suggested above
- OPI diagram (and any other relevant parts of the OPI) use the mechanisms appropriately