sPHENIX discussion of the superconducting solenoid

["Yip, Kin" <kinyip AT bnl.gov>]

Hello,

Almost forgot to let this mailing list know what we've found ....   When 
I went to 1008B mezzanine to read the current from the DCCT
this morning, I noticed that it's NOT showing anything ( see the jpg 
picture).   We now think that this is the cause of the ~93 A drop in the
Magnet-Current.  ( A year ago, it dropped several amperes just after we 
just connected some wires to it.  )

Here, I've made (again) the plot of current drop which coincided with 
the the rises of voltage-taps for Neg-GC-Lead and Pog-GC-Lead.
This time, I also included the water-cooled-bus temperature rise.   We 
still don't know why there was fluctuation of voltage taps and
temperature around the time of this ~93 A drop.

But the Cryo's gas flow is based on this Magnet-Current --- hard-wired 
(Brian told me).  So, when this Magnet-Current dropped, the gas flow 
also dropped which resulted in the rises of voltage-tap (voltage) values.

Perhaps, more importantly, not just other current readings have not 
changed, the Hall Probes that John Haggerty has installed inside the Magnet
Bore have all shown no fluctuation/change at all.  John is confident 
that those probes should see a 2% change if there is really a real drop.

We can't/shouldn't fix the DCCT while the magnet is in top 
current/field.   Pablo and his team are busy tomorrow for other works 
that have been planned.

But he agreed to investigate this DCCT in the next Maintenance Day which 
is on June 20.

Kin

PS: We have checked that the large fluctuations water-cooled-bus 
temperatures yesterday afternoon haven't happened daily.


On 6/4/24 00:42, Yip, Kin wrote:
> Hello, Carl, Pablo, and Winston,
>
> Just before I left, I noticed that the so-called "Magnet Current" dropped 
> instantly by almost 90-100 A to only ~4500 A (instead of close to ~4596 A).
> This has been the case since 15:47 this afternoon.
>
> I show you the plot in the 180Hz data.  But all the currents stay about the 
> same, including qfg.8b-sphenix.B0.
>
> Winston:  is it possible that a factor suddenly got changed ???
>
> Tomorrow, I'll go up to the 1008B mezzanine to take a look at the DCCT 
> meter.
>
> Kin
>
> PS:
>
> I checked John Haggerty's hall probes inside the Magnet bore which show no 
> such step.
>

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