[Dsg-hallc_controls] Fwd: Hall C - SHMS and HMS Dipole field regulation (using NMR probes)

[Brian Eng]

Just forwarding to the mailing list so everyone has the information.

----- Forwarded Message -----
> From: "Steve Lassiter" <lassiter at jlab.org>
> To: "Ruben Fair" <rfair at jlab.org>
> Cc: "Brian Eng" <beng at jlab.org>, "Pablo Campero Rojas" <campero at jlab.org>, "Michael Fowler" <fowler at jlab.org>, "Eric
> Sun" <qsun at jlab.org>, "Sandesh Gopinath" <gopinath at jlab.org>, "Probir Ghoshal" <ghoshal at jlab.org>
> Sent: Thursday, July 5, 2018 9:17:51 AM
> Subject: Re: Hall C - SHMS and HMS Dipole field regulation (using NMR probes)

> Hi,
> 
> The approach outlined is a little like putting the cart before the horse.
> Location of the sweet spot that is accessible and non-intrusive will dictate
> the design of the field shunt and then which type and range of field probe is
> chosen. GMW can provide custom range NMR probes on request. The five standard
> ranges for the new model 1226 probes are:
> 
> 0.19 - 0.52T
> 0.42 - 1.29T
> 1.13 - 3.52T What we have now.
> 3.29- 10.57T
> 8 - 22.8T
> 
> 
> 1. Using Tosca models, is there a convenient location that a field shunt can be
> added to the Dipole magnets that will allow for high resolution field control
> of the magnet using as few NMR probes as needed, either old generation , new
> generation and with or with out field compensation coils. See the attached work
> in process word document for the SHMS dipole and old style NMR probes for some
> key values.
> 
> Field regulation should be from ~0.1Gev/C to full current excitation of the
> magnets.
> 
> The field homogeneity at this location must be sufficiently high to allow the
> NMR control electronics to lock onto the developed (resonant) NMR signal.
> If necessary, iron pole pieces may have to be designed to create this region of
> high field uniformity.
> Probes cannot reside in regions where scattered particles will transverse.
> Resolution between external field readings to the central field should be such
> as to maintain 1E-7 to 1E-6 central field regulation .
> Accessibility and position reproducibility should be considered.
> 
> 2. If the new generation NMR probe is chosen (very likely the case), then
> software/hardware to allow control of the PSU from the NMR signal is needed.
> 
> 
> 3. Design, fabricate and install suitable fixture to mount the probes.
> 
> 
> The Excel spreadsheet shows the HMS dipole gap coverage using the 1060 NMR
> probes, internal to the magnet. Gaps due to the loss of NMR probe being able to
> locked due to large field gradients.
> 
> Steven
> ----- Original Message -----
> 
> From: "Ruben Fair" <rfair at jlab.org>
> To: "Eric Sun" <qsun at jlab.org>, "Sandesh Gopinath" <gopinath at jlab.org>, "Probir
> Ghoshal" <ghoshal at jlab.org>
> Cc: "Steven Lassiter" <lassiter at jlab.org>, "Brian Eng" <beng at jlab.org>, "Pablo
> Campero Rojas" <campero at jlab.org>, "Michael Fowler" <fowler at jlab.org>
> Sent: Thursday, July 5, 2018 8:16:06 AM
> Subject: Hall C - SHMS and HMS Dipole field regulation (using NMR probes)
> 
> 
> 
> All,
> 
> 
> 
> Let me know if I have missed anything or have got it wrong.
> 
> 
> 
> Summary of our discussion on Tuesday:
> 
> 
> Requirements
> 
> 
> 
> 1. Select suitable NMR probe to allow tracking of 'full range' of field on the
> dipoles for both the HMS and SHMS
> 
> ('Full range' = from a few hundred amps to full operating current)
> 
> 
> 
> 2. Select suitable mounting location for these NMR probes.
> 
> The field homogeneity at this location must be sufficiently high to allow the
> NMR control electronics to lock onto the developed (resonant) NMR signal.
> 
> If necessary, iron pole pieces may have to be designed to create this region of
> high field uniformity.
> 
> 
> 
> 3. Design, fabricate and install suitable fixture to mount the probes.
> 
> 
> 
> 4. Software/hardware to allow control of the PSU from this NMR signal.
> 
> 
> 
> Timeline
> 
> 
> 
> 1. Ideally install on both the HMS and SHMS dipoles before the 2018 Fall Run and
> monitor in parallel with the existing probe systems.
> 
> 
> 
> 2. Otherwise, we will have to wait till the next available shutdown period to
> install the new probes.
> 
> However, in this case, work should carry on in the background to complete the
> calcs and design of mounting fixtures etc. to be ready for installation.
> 
> 
> 
> I would suggest that Eric leads the work.
> 
> 
> 
> Requirements : Items 1,2 and 3 - Magnet Group
> 
> Eric - TOSCA modeling to determine suitable location for probes and pole piece
> design (with help from Probir as necessary)
> 
> Sandesh - Selection of NMR probe (if not already identified), design, fab and
> installation of any mounting fixtures.
> 
> 
> 
> Note: Need to evaluate forces on any fixtures and pole pieces and any reciprocal
> forces on dipole coils.
> 
> 
> 
> Requirements : Item 4 - DSG
> 
> 
> 
> regards
> 
> 
> 
> Ruben
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