sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi Dave,

From  \\bnl.gov\c-adnas\babar\BaBar P.S. Manual\Babar P.S. Section1.pdf, p.11 (PDF page),

you can see that the cable resistor in BaBar is 1.25 milli-Ohm.   In our high-field test, we've 0.666 milli-Ohm (measured by Carl).

Putting 1.25 mOhm and our inductance ~ 2.4 H (Wuzheng's old sPHENIX model --- which he may update in near future),
into my calculator webpage :  https://www.c-ad.bnl.gov/kinyip/sPHENIX_Ramp_Down.html

it'd take about ~1959 s (more than half an hour) to go from 4600 A to 1300 A.   This is (4600-1300)/1959 ~ 1.7 A/s on average (faster a the beginning than at the end).

Our inductance is slightly less than BaBar's => 1.7 A/s =>  slightly faster than BaBar's 1.6 A/s on average.

So, I'd think that you should make the total cable resistor not more than 1.25 mOhm.   1 mOhm may be even better.   I guess we won't worry about
a few more minutes in "slow discharge"/ramp-down   but it's  good not to ramp down too fast.

Kin