sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi,

I know you're probably busy with your test today ...

Have you been able to solve electrical diagram model problem (when Dave and I were in your office) ??

Please let us know how long you've got for the current to decay.

Our cable resistance (in the high field test) of 0.25 mOhm (not BaBar's 1.25 mOhm) and L= 2.36 H (that in our Magnet simulation) --- slightly smaller than BaBar's 2.58 H,

the time-constant (tau) would be 9440 second (2.622... hours).

If I use Martin Berndt methodology in  "\\bnl.gov\c-adnas\babar\BaBar P.S. Manual\Babar P.S. Section1.pdf" (p.15), and

and assuming -1 V on the diode's forward voltage drop (instead of -0.7 V),

=> i(t) = 8600*exp(-t/tau) - 4000 (Amperes)

it'd take 4569.5 seconds or 1.27 hours to get to   ~1300 A   (where we may do fast discharge).

Kin