sPHENIX discussion of the superconducting solenoid

["Phillips, David B" <phillips AT bnl.gov>]

Don,

 

I agree, I have no solution, just concern.

 

I see 3 ways forward:

1)      Someone does a heat transfer analysis (do we have the information/time/resources to get it done?).

2)      Go to an excessively long soak time (this could be time consuming, is that an issue?)

3)      Record the soak time and if the magnet quenches, then you know it was too short (this has a small(?) risk of breaking the magnet, and if there is a quench how do you know if it was due to insufficient soak time or some other cause?)

 

As far as I can tell we are moving forward on a combination of paths 2 & 3.

 

Dave

 

 

From: Lynch, Don
Sent: Thursday, January 18, 2018 12:07 PM
To: Phillips, David B; Yip, Kin; sphenix-magnet-l AT lists.bnl.gov
Subject: Re: [Sphenix-magnet-l] Fwd: RE: How long did you soak the Magnet before running high-current ?

 

Hi Dave, “soak time” is still meaningless. Either you have enough temperature sensors or you don’t. If what you say is true about limited temperature sensors, then there could be additional thermal mass that is still changing temperature, so all items have not achieved a constant temperature. Taking a guess at how long to “soak” with out some analyses to back it up does not solve the problem.  

 

Don

 

From: "Phillips, David B" <phillips AT bnl.gov>
Date: Thursday, January 18, 2018 at 11:53 AM
To: Don Lynch <dlynch AT bnl.gov>, "Yip, Kin" <kinyip AT bnl.gov>, "sphenix-magnet-l AT lists.bnl.gov" <sphenix-magnet-l AT lists.bnl.gov>
Subject: RE: [Sphenix-magnet-l] Fwd: RE: How long did you soak the Magnet before running high-current ?

 

Don,

 

I think what you are saying is correct for heat “leaks”, but my concern is the “thermal mass”  coming to equilibrium.

With the limited number of temperature sensors how do you know you have achieved this equilibrium?

 

Dave

 

From: Lynch, Don
Sent: Thursday, January 18, 2018 11:31 AM
To: Phillips, David B; Yip, Kin; sphenix-magnet-l AT lists.bnl.gov
Subject: Re: [Sphenix-magnet-l] Fwd: RE: How long did you soak the Magnet before running high-current ?

 

Dave, Kin,

 

Soak time is meaningless in heat transfer. If you are looking at the temperature of the liquid undergoing phase change, it can be constant while temperatures of the surrounding structure may continue changing. Once all items have achieved a constant temperature, (and not necessarily the same temperature) you have achieved equilibrium; any additional “soak time” does nothing. It is quite correct to say “don’t worry about soak time, check the temperatures". The only question is how long do all of your temperatures need to be constant to validate that you have reached equilibrium. 6 hours with no change in temperature is certainly enough, maybe even excessive.

 

 

-Don

 

From: sPHENIX-magnet-l <sphenix-magnet-l-bounces AT lists.bnl.gov> on behalf of "Phillips, David B" <phillips AT bnl.gov>
Date: Thursday, January 18, 2018 at 10:36 AM
To: "Yip, Kin" <kinyip AT bnl.gov>, "sphenix-magnet-l AT lists.bnl.gov" <sphenix-magnet-l AT lists.bnl.gov>
Subject: Re: [Sphenix-magnet-l] Fwd: RE: How long did you soak the Magnet before running high-current ?

 

Kin,

 

Not sure I would interpret Wes saying “I would guess an extra 6 hours would be prudent” as not worrying about soak time.

 

Dave

 

From: sPHENIX-magnet-l [mailto:sphenix-magnet-l-bounces AT lists.bnl.gov] On Behalf Of Kin Yip
Sent: Wednesday, January 17, 2018 5:26 PM
To: sphenix-magnet-l AT lists.bnl.gov
Subject: [Sphenix-magnet-l] Fwd: RE: How long did you soak the Magnet before running high-current ?

 

Hi,

It seems that Wes and Pasquale didn't worry about the "soak time" too much.  They suggested checking the "thermometers" for
temperature stabilization.   I attach the reply from Wes Craddock and Pasquale below.

Kin

-------- Forwarded Message --------

Subject:	RE: How long did you soak the Magnet before running high-current ?
Date:	Wed, 17 Jan 2018 21:18:02 +0000
From:	Craddock, Wesley W. <wwc AT slac.stanford.edu>
To:	'fabbric' <pasquale.fabbricatore AT ge.infn.it>, Kin Yip <kinyip AT bnl.gov>

We didn’t really spend much thought on soak time for the magnet once it was filled with LHe.  In part this was because there are a number of hours involved in filling the magnet storage vessel in the valve box and checking out the magnet (voltage test to ground, looking at magnet position, etc.).  If there is residual heat in the magnet, it will be difficult to fill the LHe pot.   Also the two magnet layers are mostly high purity aluminum with high thermal conductivity. 

 

I would guess an extra 6 hours would be prudent, but as Pasquale points out the best thing is to look at temperature sensors.

 

Hope this helps.

 

Wes

 

From: fabbric [mailto:pasquale.fabbricatore AT ge.infn.it]
Sent: Wednesday, January 17, 2018 12:28 PM
To: Kin Yip; Craddock, Wesley W.
Subject: Re: How long did you soak the Magnet before running high-current ?

 

I only participated at the magnet commissioning and this question
was not raised. However there are thermometers on the coil
and  one can look at the temperature stabilization.

I think that Wes has much more experience on this magnet after years
of operation and can give a more appropriate answer

Pasquale


Il 17/01/2018 21:20, Kin Yip ha scritto:

Hi,

In the past BaBar operation (or whatever), did you guys need to soak the Magnet at 4.x K for   some nos. of hours before you put in high
current into the Magnet Coils   ??

Kin

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Dr. Pasquale Fabbricatore

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