sPHENIX discussion of the superconducting solenoid

[Edward O'Brien <eobrien AT bnl.gov>]

    Hi Kin,
     So there is a negative voltage dip for about 60 msec followed
    by a positive rise that caused the QLI . I wonder what can cause
    the initial negative voltage dip? How many voltage taps do we
    have inside the magnet? Do they all show this dip at the
    same time? Are the blue data points also from an
    internal voltage tap? Thanks.

    Ed

On 6/7/23 11:52 AM, Yip, Kin wrote:

Hi, Ed,

 

I agree with most of what you said.

 

It is a small voltage     fluctuation as measured by the voltage taps in the magnet that could    be from noise pick up,

 

The previous plot showed small voltage-tap fluctuation in the order of several of 0.01 mV and I showed it when the beam

was on or off.

 

But when we had QLI event, I just attach a plot in which “green” is the quench-interlock signal that was dropped --- from yesterday’s morning event.  The other signals from the voltage taps were large before the quench-interlock signal dropped.  They were volts or ~0.1 volt.

They were not small fluctuations.

 

Kin

 

From: Edward O'Brien <eobrien AT bnl.gov>
Sent: Wednesday, June 7, 2023 11:09 AM
To: Yip, Kin <kinyip AT bnl.gov>
Cc: Morrison, David <morrison AT bnl.gov>; rolandg AT mit.edu; Haggerty, John <haggerty AT bnl.gov>; stefan.bathe AT baruch.cuny.edu; sphenix-magnet-l AT lists.bnl.gov
Subject: Re: [Sphenix-magnet-l] Magnet "tripped" 3 times

 

    Hi Kin,
     I think that we should be careful characterizing what is happening
    to sPHENIX magnet as "magnet trips", which to accelerator physicists
    usually indicates a significant hardware problem. What we are
    experiencing, with the exception of the fuse event, is the quench
    protection system taking down the sPHENIX magnet power supply
    to protect the magnet. It is not a magnet quench, as some called
    it at yesterday's RHIC Coordination meeting. It is a small voltage
    fluctuation as measured by the voltage taps in the magnet that could
    be from noise pick up, a DC baseline shift in the sensor signal, etc.
    It is similar to the QLI events that I have the impression happen to the
    RHIC magnets with some frequency.
     Also in your attached plot of sPHENIX magnet voltage tap signal vs beam
    in RHIC, what causes the slow baseline shift in the voltage tap signal,
    and the apparent  glitches in the signal? Those could be the causes of the
    quench protection generated events.Thanks.

    Ed
   

On 6/6/23 5:01 PM, Yip, Kin wrote:

Hi,

 

Like what Van Kuik suggested, I made a plot of one voltage-tap (which pulled the quench-link from the quench-detector)

vs the sPHENIX ZDC-coincidence.  

 

The readings of the one voltage-tap is magnified in the range of several of 0.01 mV … really not much to do with beam

collision reduction (or increase).

 

Kin

 

From: Van Kuik, Brian <vankuik AT bnl.gov>
Sent: Tuesday, June 6, 2023 2:35 PM
To: Yip, Kin <kinyip AT bnl.gov>
Subject: RE: Magnet "tripped" 3 times

 

Are you able to watch the voltage taps (or other of your signals) before beam is injected, then while filling, ramping and then colliding to see if there are any markers in the data that may indicate radiation?

 

-Brian

 

From: sPHENIX-magnet-l <sphenix-magnet-l-bounces AT lists.bnl.gov> On Behalf Of Yip, Kin
Sent: Tuesday, June 6, 2023 2:09 PM
To: sphenix-magnet-l AT lists.bnl.gov
Subject: [Sphenix-magnet-l] Magnet "tripped" 3 times

 

Hello,

 

Since we turned on the magnet last Wed. (May 31) after 5 pm, the Magnet has tripped 3 times,

last Friday (11:54), last night at 23:05 and this morning 9:25.

 

Last night seems to be related to a blown fuse in the capacitor bank in the power supply.  But the

other two was due to quench-detector doing its job (that when voltage taps pass the threshold,

it’ll pull the quench link and generate fast discharge). 

 

Some of us are thinking that the only explanation is due to the radiation from the beam …

 

Not sure what we can.   Anybody with any ideas, please let me know.

 

I’m just ramping up the magnet again and it’s almost there.

We’ll power down the magnet tomorrow at 5 am for the maintenance work to fix TPC leaks etc.

 

Kin

 

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