MERLIN: IOC and OPI for new SKF Fermi chopper

[kjwoodsISIS]

As a MERLIN scientist I want IBEX to control the new SKF Fermi chopper that will be installed on MERLIN during the long shutdown.

Acceptance Criteria

1. Using the IBEX client, I can control the new SKF Fermi chopper
2. Using genie_python, I can control the new SKF Fermi chopper

Notes

1. At the time of writing (January 2021):
   • The new SKF Fermi chopper is expected to use a G5 controller.
     • see Comment 1
   • It is expected to be similar to the MB350 (G3) model on EMMA (see EMMA: Fermi Chopper #2397).
     • not quite correct - see Comment 1
   • liaise with the Chopper Group for details of the new design and timescales.
   • update this ticket as new information becomes available.

[kjwoodsISIS]

From: Carter, Tim
Sent: 18 January 2021 11:33
To: Galsworthy, Peter, Woods, Kevin
Cc: Brind, Mike; Johnson, Erik; Basham, Abigail
Subject: RE: Chopper Plans for Long Shutdown

MERLIN
We have a project to replace all the Julich FERMI Choppers with SKF FERMI Choppers. This involves the three instruments; MERLIN, MARI and MAPS. The plan is to convert MERLIN first followed by the others. Yes, you and David are correct the Controllers will be of the SKF G5 type and the set up will be the same as EMMA. In fact if I remember correctly EMMA Controller was changed over to a G5 type. Tim Carter should be able to give you info on the controls/comms needed. Erik Johnson is the Project Manager and I will ask him to include you in the Project Team and keep you updated on the requirement and programme.

In fact, EMMA’s Fermi chopper is still running on an obsolete SKF G3 controller, but at some stage (possibly before April now we have extra time) it will need to be changed to a SKF G5 controller which we now have in stock. We should discuss what this means in terms of the IBEX work required on EMMA – As the controller is identical to both IMAT and LET G5 controllers, I am assuming there will be little impact on IBEX?

From my understanding the IBEX control would be almost identical to a single disc chopper such as the G5 controllers on LET Choppers 3 & 4 or the ones on IMAT.

[davidkeymer]

Successful tests have been performed on EMMA (27/04/2021). The existing disc chopper IOC and OPI (as used on IMAT and LET) were used to control the newly upgraded G5, with independent verification via SKF software. All functions operated correctly, except that there is no rotor position readback from the fermi controller (continuously returns "0") or "Parking" functionality, so this display and control on the OPI is redundant.

[davidkeymer]

Suggest completing ticket #3985 at same time as this.

[davidkeymer]

Suggest using the existing SKF chopper OPI with a method to determine whether or not the controller in use is for a disk or Fermi to (en/dis)able functionality. This OPI also needs to be updated as it doesn't conform to the current style.