E18 dilution fridge/magnet combination

Chris Lawson has brought up an "E18" dilution fridge/superconducting magnet system, which may be being made available to beamlines at some point.

It definitely contains a Triton (maybe modified with extra commands?) and a [Mercury IPS](https://github.com/ISISComputingGroup/IBEX/issues/4224), but it is not entirely clear exactly what interactions are in place between these two bits of kit, and whether it also uses any extra ancillary equipment.

Original email:

> [...] there is a magnet which goes with the E18 dilution fridge system which also uses this newer type of power supply [the mercury IPS]. (E18 is a bit of an oddball machine, still uses Kelvinox software… but slightly differently I expect. I’m hoping to run it in the next month or so, I’ll probably get in touch when it’s cold so you can have a look!)
> It hasn’t been used since it was commissioned some years ago, but there is significant interest in using it in anger at some point this year on WISH. We have no hard timescales on this yet.

Follow up asking for clarification:

> 1. E18 was bought from a company called Vericold, but delivered by Oxford Instruments (they bought Vericold halfway through its manufacture), hence the possibility of strangeness. It uses the Oxford Instruments Triton software (which should be a fairly recent version, as the control PC was upgraded a couple of years ago) and I believe the IOC will work for temperature control. However it may have a couple of extra values that it reports (or not). I hope that it would be a case of tweaking the Triton IOC to handle that. A SECI driver already exists… I’m not sure if that’s helpful.
> 2. I need to see if the Triton software connects to the Mercury IPS in any way. If so then it makes everything more complicated as E18 will need an entirely separate driver I assume. If not then it will look like any other magnet.
> 3. Similar to point 2. I guess it depends what the Triton software does. If it’s separate then it might be good to be able to check if the E18 fridge is below a certain temperature before allowing the magnet to energise, though this is probably not a hard necessity as the power supply will obey its voltage limit and refuse to ramp if everything is not superconducting.
>
> If it’s easier to keep them separate then I see no harm in just doing that.

This ticket is mainly just a placeholder for now, cryogenics will get in touch with further details if it is confirmed to be going on a beamline.

Further thoughts from cryogenics:
- We can probably treat the systems as independent
- A single Mercury IPS is used, this should look and be controlled like any other magnet, and should not need anything special

Iniziare confermando con il team di criogenia il software E18 Triton, la connessione Mercury IPS e qualsiasi valore aggiuntivo segnalato o apparecchiatura ausiliaria. Esaminare il supporto esistente per Triton IOC e Mercury IPS una volta disponibili questi dettagli; questa issue è completata quando sono confermati l’ambito di integrazione richiesto e la necessità della beamline.

Scritto dal modello di indicizzazione a partire dal testo della issue.