Current status of Proto II
Overview] [TNDC Notes] [Operations
and IR-2 Data Taking] [Test & Commissioning]
[Prototype II] [Mechanical Design] [Safety
Systems] [Internal Information]
Last updated: 30 January 2002 by Jignesh
How Broken Wires were discovered
Checking the High Voltage Power Supply
Putting in the new Bertan [17 Jan 02]
Initially, we tried to ramp up the voltages to see if
the Bertans were working fine. We found that the Bertan labelled "2020V"
was defective. Only one of the two voltages could be turned on. When both
"2020V" & "350V" switched on simultaneously, we couldn't ramp up the
voltage of anyone. So we changed the Bertan, after which it started working
Testing the NIM power supply [18 Jan 02]
We tried testing the NIM power supply. It was not showing
the +12V as it should had showed. Also, while ramping up the voltages,
after sometime none of the voltages could be ramped up or down. They would
stop working. So we changed the power supply & ensured that it was
Tripping [18 Jan 02]
We connected the three HV cables to the chamber and turned
on the Bertans (no voltage, just the "ON" switches). The "335V" supply
started showing current draw up to about 5 uA. On the 1 uA trip range,
it would charge up, trip, charge up, trip, etc. On the 10 uA range, it
would go up to 0.5 on the front panel meter and would stay there. With
the HV cable disconnected from the chamber, the supply would behave perfectly
normally. We knew there was something wrong.
Swapping channels of the High Voltage Power Supply
[18 Jan 02]
We then again connected the three HV cables to the chamber
and turned on the Bertans. We found that "335V" was still tripping. Also,
it was showing some voltage(3V-4V at the output) even when the knob was
at zero. So we exchanged the "335V" channel with the 4th unused channel
and found that it wasn't tripping. Also, now it showed zero voltage
when the knob was at zero.
Connecting the Power Supply to the chamber [18 Jan
We then monitered the three voltage test probes
from the three bertan channels and the current drawn on "1930V" channel
for trips. We increased all the three power supply voltages simultaneously
: The power supply "1930V" channel was increased in steps of 100V upto
300V, "870V" in steps of 50V and "335V" in steps of 15V. For "1930V", we
tried to put meter range at 1 uA, but it tripped. So we tried putting the
meter range at 10 uA, but it was still tripping. So we decided to remove
Front & Rear end hardware & trace if there were broken wires.
Hunt for Broken Wires
Mapping of wires with the design diagram [21
We got a copy of layout of cables, so that we could mark
the cables after checking. We removed the front & rear end hardware.
We even removed the Front End Assembly blocks, so that it would be easier
for us to trace the cables.
Resistance measurement check for continuity on the
same end [22-24 Jan 02]
We started by connecting two field wires on the same
end & seeing what resistance it shows. We got some strange results:
We concluded that there must be some broken wires.
Field wire 1 in superlayer 1 on south front end showed resistance
as 102k with respect to a reference wire on the same side even though
it was not connected and on rear end showed infinite resistance.
Field wires 44 & 78 in superlayer 3 on south front end
showed resistance as 100k with respect to a reference wire on the
same side even though they were not connected . But when we connected the
same wires on rear end they showed infinite resistance.
Continuity Test on front and back end [24-28 Jan 02]
We thought of finding some broken wires externally. So
we marked all unconnected wires on the layout. We then started checking
each unconnected wire's resistance by connecting the same wire on both
ends. We saw some strange observations.
We then connected sense wires of superlayer 3(north front
end). They looked to be working fine beacuse they were showing some resistance.
Field wires of superlayers 2 & 3 were working fine. We didn't know
what to do.
We now connected wire 78 on front & rear end and got
resistance as 14ohms. When we connected wire 44 on both ends, we got infinite
When we connected sense wires of superlayer 2(south front
end) on both ends, they were showing infinite resistance.
Visual Inspection [29 Jan 02]
We then surprisingly came to know that there were small
windows on the front & rear end through which you could see inside
the proto II. We tried to see through the window if we could see any broken
wires. We called Karl Bouldin & Thomas Glanzman to help us. When we
were looking through bottom window of the front end, we saw one broken
wire but couldn't make out the feedthrough. So Tom, with his digital camera
took some pictures of the wire. We saw the pictures on the computer but
couldn't locate the feedthrough. So, We went back to take more pictures.
Karl finally located the feedthrough with his great eyes, looking through
top window of the front end. Tom, tried to take pictures of the feedthrough.
We then saw the pictures on the
computer & found the exact feedthrough. It was wire 35 of superlayer
4, north front end. We were happy to find the broken wire. But now the
bigger problem, what to do next?
List of known Broken Wires [29 Jan 02]
Future Plan [31 Jan 02]
- [Superlayer 2, South Front End]
Wire 222 Wire 225 Wire 375
Wire 319 Wire 372 Wire 278
Wire 272 Wire 275 Wire 328
Wire 369 Wire 325 Wire 231
Wire 322 Wire 228 Wire 378
Wire 281 Wire 234
- [Superlayer 2, South Front End] Wire 29
- [Superlayer 4, North Front End] Wire 35
- [Bottom, South Front End] Wire 1 Wire 3
Swagato, Mike, Karl & I had a meeting where we discussed the possible
options. We agreed upon the fact that replacement of broken wires
would not be advisable till summer. So we stopped monitoring the temperature
& water level. We also stopped gas circulation. We are now going to
work on setting up the Epics panel for monitoring environment variables
in the Proto II.