sPHENIX discussion of the superconducting solenoid

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

Hi,

Pablo and his team checked any change since last Nov.  The only thing they 
added to the Dump Resistor is the DCPT Board (so that Carl
can get a voltage across the Dump Resistor).  

But even after disconnecting that DCPT, the hipot still tripped the same way 
(> 460 V or so).

As we discussed in the 8:30 - 10 am meeting, Carl would like to disconnect 
the connector below the Extension Doghouse.   I understand that
we're installing the baker scaffolding even this afternoon or so, which would 
allow us to do so.

Kin

-----Original Message-----
From: Yip, Kin <kinyip AT bnl.gov> 
Sent: Thursday, April 13, 2023 5:15 PM
To: sphenix-magnet-l AT lists.bnl.gov
Subject: Hipot: trip above 400V (below our target 520 V)

Hi,

Today, Carl and I (my job was just a watching guide to prevent people 
from getting too close to the Current Leads) have been trying to do the 
warm hipot for the Magnet up to the Dump Resistor.

Our target hipot voltage is 520 V as always (from BaBar).  When the 
magnet "quenches", the highest voltage is like 312 V or so and in fact, 
since we put a ground in the middle, it's +/- 156 V really.

Today, below 400 V, we got around 5 MOhm.   But after > 460 V or so --- 
the highest Carl was able to go to was slightly above 480 V or so.

So, this is definitely different from last time we did hipot (cold or 
warm).  For the whole day, Carl tried to make sure that no cable was 
touching any conductor or anything suspicious like that for the whole 
day but there was no breakthrough.

The threat of leakage to ground is that (as Carl explained to me all the 
time) if there are two leakages to grounds and a loop can be developed 
that would burn out the superconducting coil 🙁

Carl would like to disconnect things --- which would involve different 
kinds of works with various difficulties--- in order to find the source 
of problem.  The first thing may be the connector (for voltage taps) 
under the Extension Doghouse (in the South of course).  Frank and Chris 
talked about using a baker scaffolding to get to that connector ...  
We'll discuss in tomorrow's 8:30 am meeting.

At least, we want to tell it's on the Magnet side or the side of 1008B, 
I guess.

Somebody said there was flooding a while ago.  I just went to take a 
picture on the berm (as attached).   All the pipes are kind of sealed 
and the pipes actually go up a slope of the penetration before coming 
down/out of the West Wall Penetration --- no sign of dampness.  We have 
never had water dripping/flowing down from the West Wall.


Kin