sPHENIX discussion of the superconducting solenoid

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

Hi,

I made the 19 cm model first to check the B-field uniformity inside the TPC => no visible difference.    Then, I also used it to calculate the force on the poletip,  the main forces
on the poletip for 19 or 30 cm are almost the same, tiny tiny difference --- in the dominant direction (z).  

I still have the email that I sent to Jon Hock and I attach it here (for record).

Kin

PS:  Everybody (including Wuzheng) is in the mailing list anyway and so I don't need to include anyone in particular.

On 10/12/2018 10:50 AM, Meng, Wuzheng wrote:

Hi Jim,

 

In my analysis, the thickness of pole tip is still 30 cm. All my information about the magnet parts are old (before 2015, I guess).  I remember that Kin has done some studies about changing the thickness of pole tip to thinner case, to see if the force (?) on the pole tip changes. I don’t remember details. Kin may remind me.  From my view, if the pole tip is thinner, then the force (the pulling force) on the wheels will be slightly smaller. This is because of the degree of saturation (in steel) is slightly higher, but not much.

 

About the force magnitude, near time=0, it gives 905 N; I think it is not real. If you imagine, during t </= 0, f(t)=1, which means the full operation current; at t > 0, the current drops.

The eddy current is produced by dB/dt (or dφi/dt, here φ is the flux linkage). At the point  t=0, this first derivative does not exist, or it is undefined, based upon the definition of the derivatives, the derivative (at certain point) exists only if you get the same value of the slop when you approach to this point from the left and from the right.

 

In my Excel file, I did not break down the force into parts; I only gave out the total forces on each entire wheel. According to present setting, I am able to get forces on separate parts: forces on Ring 1, 2, 3, 4 (separately), and forces on 12 bars (totally). If you think this will be helpful, I can do it.

 

Please comment.

Wuzheng

 

 

 

From: sPHENIX-magnet-l <sphenix-magnet-l-bounces AT lists.bnl.gov> On Behalf Of Mills, James A
Sent: Friday, October 12, 2018 9:02 AM
To: Yip, Kin <kinyip AT bnl.gov>; Haggerty, John <haggerty AT bnl.gov>
Cc: sphenix-magnet-l AT lists.bnl.gov
Subject: Re: [Sphenix-magnet-l] Forces on the wheels (of TPC)

 

Hi Kin,

 

I am back to work and finally getting a chance to look at Wuzheng’s analysis.  This looks good, but I do have a question and am not sure how it affects his results.  Do you know what value he is using for the pole tip thickness?  If you recall we had been proposing a change, to go with a 7.5-8” design thickness.  The poles in Wuzheng’s model appear to be the original 12” thick versions.  At least from my old eyes, that it how it appears, though I may not be correct and we should verify this.  Does this have an effect on the quench calculations?

 

Also, is the calculated force uniformly distributed across the face of each end wheel?  And, the question of using 600N versus 905N is a good one.  I suspect we should examine both forces.  What do you think?

 

Thanks,

Jim

 

From: sPHENIX-magnet-l <sphenix-magnet-l-bounces AT lists.bnl.gov> On Behalf Of Yip, Kin
Sent: Wednesday, October 10, 2018 9:29 PM
To: Haggerty, John <haggerty AT bnl.gov>
Cc: sphenix-magnet-l AT lists.bnl.gov
Subject: [Sphenix-magnet-l] Forces on the wheels (of TPC)

 

Hi John,

 

Please find here:

https://collab.external.bnl.gov/sites/sPHENIX-Magnet/Shared%20Documents/Dr.%20Meng%20Wuzheng's%20calculations/2018-10-10%20Wheel_eddy_curr_force.pptx

 

Wuzheng’s calculation of the forces on the two wheels here.   Are those hundreds of tons manageable  ??

 

{ By the way, Wuzheng doesn’t charge us the time that the Opera has taken to calculate, many days 😊  }

 

Kin

 

From: Meng, Wuzheng
Sent: Wednesday, October 10, 2018 9:24 PM
To: Yip, Kin <kinyip AT bnl.gov>
Subject: RE: Modified power point file

 

Hi,

 

Thanks for your time!

 

Wuzheng

 

From: Yip, Kin
Sent: Wednesday, October 10, 2018 9:22 PM
To: Meng, Wuzheng <meng AT bnl.gov>
Subject: RE: Modified power point file

 

Hi,

 

Looks good !  Thanks !  … I’ll send it to the sPHENIX Magnet mailing list …

 

Kin

 

From: Meng, Wuzheng
Sent: Wednesday, October 10, 2018 8:08 PM
To: Yip, Kin <kinyip AT bnl.gov>
Subject: Modified power point file

 

Kin,

I modified page 4 and 6. I keep the same file name.

How is the new one?

Wuzheng

Attachment: Forces on the 19cm endcaps ~ as the forces on the 30 cm endcaps.eml
Description: Forces on the 19cm endcaps ~ as the forces on the 30 cm endcaps.eml