sPHENIX discussion of the superconducting solenoid

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

Hi Dave and Rob,

 

I don’t think you have too much of a choice … but if there is a choice, please have the Water-Cooled-Busses as short as possible and of course as “cold” as

possible.   This way, the resistance of the entire path will be low.    WE want the resistance to be as low as possible.

 

 In Dave Phillips’ email, he’s got:

 

• Resistance at 20C = 3.11 micro-Ohms/ft
• Resistance at 65C = 3.59 micro-Ohms/ft
• Resistance at 350’ (at 65C) = 0.0013 Ohms

 

At that time, we had cables running to the floor and going back up to the platform and he’s being “conservative”.  I measured it myself a couple times

(one time with a laser pointer and I walked from 1008B to 1008 (across the berm) and measure … it’s ~200 ft.

So, at 65 C and it’s ~0.000718 Ohm (or 0.718 mOhm).     ( There are two pairs in parallel … so you multiple by 2 and divide by 2 = 1. )

 

From my webpage :  https://www.c-ad.bnl.gov/kinyip/sPHENIX_Ramp_Down.html (at the bottom), the di/dt (time=0) when you ramp down,  is -1.70 A/s if you assume (diode voltage=0.7 V) or -1.78 A/s (diode voltage=0.9) .  

{ It also depends on the actual inductance … }

 

But if it’s 20 C, the total resistance is  0.622 mOhm, di/dt (t=0)  (if 0.7 V diode voltage) is -1.51 A/s  or -1.59 A/s (if diode voltage of 0.9 V).   

 

{ I remember Dave Chan told me a number which is much closer to 20 C than 65 C 😊 }

 

Carl and I have been calculating these for a while.  The point is that we want this di/dt to be as small as possible.   Because if its absolute value is higher than 2 A/s or something like that, we

may quench every time when we ramp down.    Shorter distance and colder water will help.

 

Kin

 

 

From: Phillips, David B <phillips AT bnl.gov>
Sent: Thursday, April 19, 2018 1:43 PM
To: Schultheiss, Carl <carls AT bnl.gov>
Cc: Streckenbach, Brian <bstreckenbach AT bnl.gov>; Yip, Kin <kinyip AT bnl.gov>; Rosas, Pablo J <rosas AT bnl.gov>; Giannotti, Paul <gia AT bnl.gov>; Mills, James A <mills AT bnl.gov>
Subject: PHENIX existing WCB

 

There are 4 pairs of copper water cooled bus from 1008B to 1008-IR.

2 pairs of 2” extra strong

2 pairs of 2” double extra strong

 

2” extra strong:

OD = 2.375”

ID = 1.933”

Wall thickness = 0.221”

Area = 1.49 sq in

Resistance at 20C = 5.53 micro-Ohms/ft

Resistance at 65C = 6.38 micro-Ohms/ft

Resistance at 350’ (at 65C) = 0.0022 Ohms

 

2” double extra strong:

OD = 2.375”

ID = 1.503”

Wall thickness = 0.436”

Area = 2.66 sq in

Resistance at 20C = 3.11 micro-Ohms/ft

Resistance at 65C = 3.59 micro-Ohms/ft

Resistance at 350’ (at 65C) = 0.0013 Ohms

 

I think the actual length will be less than 350’.

Actual operating temperature should be below 50C.

For one set of 2” double extra strong WCB the required water flow at 4800A and 20F temperature rise is 10.3 gpm (this flow is achievable, velocity is 1.9 ft/s).

 

Photo of the WCB where it exits 1008B attached.

The cooling water has two paths in the bus, one direction cools the bus from 1008B to the magnet, the other direction cools the bus from the wall of 1008B to the power supply and is the cooling water for the power supply. This can be modified for sPHENIX.

 

David Phillips

Building 911B

Upton, NY 11973

631-344-4671, Fax 631-344-5954, Cell 631-804-9477

On site pager 344-3456 then 4267 then your number