[BTeam] Follow-up Re: More data on LCW Temperature variations

[Michael Tiefenback]

Kind listeners:

One of the first principles scaling arguments brought to my attention long ago by Leigh Harwood is that, to lowest order, a temperature change in the steel of an iron-dominated magnet will result in expansion (1+a)*L longitudinally by the same fraction as the inverse pole-tip gap 1/[(1+a)*G] changes.  These cancel as they apply as the product (1+a)*L * (1 / [(1+a)*G]), leaving only weaker things like a temperature-dependent permeability in play.  So one _expects_ iron temperature to remain a very weak influence.

I thought you might find this interesting and useful.  I hope I have not fouled up the algebraic representation.

MIchael Tiefenback

________________________________
From: BTeam <bteam-bounces at jlab.org> on behalf of Jay Benesch <benesch at jlab.org>
Sent: Tuesday, September 13, 2022 18:39
To: BTeam <bteam at jlab.org>
Subject: [BTeam] Follow-up Re: More data on LCW Temperature variations

https://logbooks.jlab.org/entry/4041098
Submitted by okumar on Tue, 09/13/2022 - 15:56.

We did more investigation on this issue, so far we are able to verify
that ARC7, ARC9 and RSEP9 shunts voltage fluctuation do coincide with
the beam position change. Plotting all the respect shunt currents with
respect to shunt voltage, LCW temperature & beam positions shows no
shunt current variations (see attached waveforms). Investigation on this
problem will continue tomorrow.

three figures.

Let's hope the heat exchanger swap tomorrow solves the problem.
https://tasklists.jlab.org/atlis/tasks/107471

The coils are not well coupled to the steel, but steel may see some
modest temperature, and therefore thermal expansion/contraction.  Pole
length will clearly change.  Whether pole spacing will change enough to
compensate is beyond my powers of visualization.
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