sPHENIX discussion of the superconducting solenoid

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

Powerpoint (Carl Schultheiss) : https://indico.bnl.gov/event/5935/ 

 

 

1. Carl with his presentation got us to discuss about two different of works related to voltage taps.  First, since we have many spare channels left at the MPF

connectors at the bottom of the doghouse/junction-box attached to the Valvebox, he proposed that we re-route some of the voltage tap signals from the
magnet which originally went up to the chimney and came out of the connectors at the top of the Valvebox,  to now be connected directly to the MPF connectors
at the bottom of the junction-box.   There is a small chance that the flaky VT11 is due to connection in the chimney/Valvebox and this re-routing may solve a problem. 
Even if rerouting doesn’t solve a problem, this is still almost like a no-brainer.   There weren’t too many questions about it after people understood what Carl meant.

2. For the second part, the voltage-tap VT11 was one that showed intermediate circuit-opening during the high-field test and we abandoned it at the end.   So far, we
   haven’t found any fault about it but we haven’t actually reached it.  To reach it or to add spare close to it, we have to open more on the magnet junction-box.
   If we add spare for VT11, we may as well add it to VT05.
   
   
3. Joe D’ambra pointed out that we should talk to Ray Ceruti.   I then walked to the 902 floor and found Ray (whose hand was still dirty and dark) and
   brought him up to the conference room.  We talked with Ray and after a few back and forth, Ray felt that he could do it without too much risk.   It’s just a matter of
   time.  He’ll try at least to open one side (VT11 side or the VT5 side) and hopefully we could reach the other side.   He estimated that it may be a day or two to open it up and

another 2 days to close it back.  All in all, it may be a week of his time.   He’ll send us an email when he can find a time to do it.  This is OK as it’s not really that urgent.

4. It’s not clear whether there are still unused wires which go through the Extension.  Joe said that he’ll look for them after Ray finishes opening the junction-box.
   If there is no spare or not enough unused wires, we’ll use some sort of snake to put wires through the Extension.

 

5. David Phillips got us to talk about the long cable/bus connecting the power supply to the Magnet current leads.   Carl and I were advocating for lower total resistance
   to prevent the initial di/dt being too large to cause quench.  ( You may see my email sent yesterday : https://lists.bnl.gov/mailman/private/sphenix-magnet-l/2019/000902.html )
   Even with the small resistance of 0.666 mOhm, the ramp-down time was like just almost one hour, compared to 40.5 minutes
   Dave was worried that too low resistance would cause the ramp-down time to be too long.  Carl said that we could always add some resistance though Dave said that it’s
   not as easy as people thought.   But other than David, people generally worried about the quench more than the ramp-down time being too long.

 

6. After the meeting, I discussed about the above addition of spare voltage taps and the works involving Ray Ceruti (with the presence of Jim).   He also agreed that we should do it
   as long as the expert like Ray doesn’t feel there is any significant risk, which was the case.  

 

7. When I discussed with Ed in another occasion about the lower resistance and lower di/dt vs longer ramp-down time, Ed also didn’t worry too much about the one hour vs 4x minutes.
   And in fact, Ed pointed out that even if we don’t ramp down the Magnet, there are only a few spots close to the poles which are at 100 G or so and we may enter the Experimental Hall
   even when the Magnet full current is on.   Whenever I emphasized the risk of quenching, people seemed to be threatened by that more.
   
   
   

 

Kin