sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi,

This morning, when I was in 912 looking at Gpm reading of voltage taps (voltage diff. between two points in Magnet Coil) with Carl,
when somebody raised the roll-up door, we saw the voltage by some mV.   They closed the door after 20 minutes or so and there are
several mV.   So, temperature affects resistances ...

In attached plot, I show your linear pots' readings since the end of Dec. and the labels are :

LP5 -Axial (north west)
LP6 - Radial (north)
LP7 - Radial (south)
LP8 - Axial (north east)

They dropped gradually and quite sharply after Jan. 6.  3 of the 4 went back to higher values but LP7 didn't.   I think these changes were
due to temperature but I'm not sure why LP7 didn't go back as the others 3.

We'll observe their relative change when we raise the currents.

Winston's code is :   /vobs/ados/kt34972/kt34972Cntrl.rad    in our Control System and you need to use "Clearcase".
( such as "ct setview kinyip").     They're all according to your prescription 0.0078 inches  per delta(kilo-Ohm) for LP5 etc.

I extract the relevant part of his codes :
      case 4:
        newTravel = .0078 * ((newResistance - g_potResistance[lPotNum]) / 1000);
        break;
      case 5:
        newTravel = .0087 * ((newResistance - g_potResistance[lPotNum]) / 1000);
        break;
      case 6:
        newTravel = .0079 * ((newResistance - g_potResistance[lPotNum]) / 1000);
        break;
      case 7:
        newTravel = .0078 * ((newResistance - g_potResistance[lPotNum]) / 1000);
        break;

where the original resistances were measured by Paul Giannotti :
  g_potResistance[4] = 2430;
  g_potResistance[5] = 3000;
  g_potResistance[6] = 2400;
  g_potResistance[7] = 2900;


They all seem correct to me.

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This is what I said that I'd check again.    Could you please pass to me your spreadsheet for your 3 mil calculation for 5 deg. F (due to different expanasion/contraction
of steel and Al) ?


Kin

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