Status of SMs tested :

1
Status of SMs tested

• THE SUPERMODULES(SMs) sent to BNL after testing
  10
• The SMs yet to be sent to BNL 14
• Brief Account of TESTING PROCUDURE
• At first the SM is flushed in Gas for 2 hrs
  (depending on size).
• It is then thoroughly leak tested with Leak
  Detector both on the TOP and BOTTOM.
• Then after flushing for 48 hrs we check with
  shorting connectors if there is any Short
  due to wire breakage.
• The Unit Modules are shorted and HV is applied
  slowly.
• After its seasoned at -1600 volts we test with
  DAQ and Gas- 4 boards.

2
1) SM_ 09 _N _01-------- This was tested with
New RC network and after testing Zone by zone we
found that Zones H and B have high leakage
current. All the Zones have been individually
tested till -1600 Volts and with all seven UM
together (leaving H and B UM) we have tested till
1600 volts until gas finished . The zones H and
B must be checked later by giving more time to
season after we get new gas supply.2) SM
_06_M_01---------This was a very well behaved
module and we gave HV till 1600 volts and all
the six were seasoned together and
satisfactorily. Few sparks were seen in this
SM.3) SM_5_M_01---------This module although
small but tripped at 1250 a number of times and
we feel that next time we need to go fast till
1200 volts and season it at high voltages
slowly.4)SM_8_N_01 ----------tested till -1600
volts.
SMs TESTED SO FAR after BNL despatch
3
NEW RC NETWORK

• The details about new RC network tests is
  We have earlier connected a 1 Mohms resistance on
  the Detector side and the discharge time for old
  HV boxes were 2.2 millisecs. With the new RC
  network where there is one capacitance of 0.22 nF
  and 1Mohm on the Detector side the discharge time
  is 0.22 millisecs.
• We have also connected a LED as a sensor
  for spark monitoring and shorted it to so that
  when there is a spark there is some
  synchronization seen with the separate Leakage
  Current Meter , CAEN HV module current reading
  and LED glow.

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• The SM with new RC network went upto -1400
  volts and even after sparks which were monitered
  did not trip unlike the old RC network which was
  parallely tested in a SM -5. The SM-5 tripped at
  -1200volts and it had the old RC network.
• With old RC Network out of 4-5 Sparks once the
  LV trips whereas with New RC Network out of 20-25
  sparks the LV may trip once if the leakage
  current becomes high.
• So modification is needed for the HV box and
  also needed to incorporate Opto-coupler circuit .

5
Work to be done
Gas Status Two Cylinders in stock. Man power
1JRF 2 S.A 2 more needed time limit to
complete Not known approx time to test one SM
completely 5 days if no problem is there with
the leaky modules and if gas is available.
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• The 5 days which were mentioned earlier
  also includes the time taken for Gas Flushing.
• Besides that while seasoning if certain UM
  has high leakage current then we have to go
  Readout Zone wise to find out which zone has the
  maximum density of bad channels.
• Further we were feeling that even at a sub
  Zonal and single channel level seasoning can be
  done.We had earlier also checked the resistances
  of the Channels with respect to cathode and
  detected a faulty channel.This can then be
  removed.
• In this way before putting boards we can
  maximize the HV seasoning to certain positive
  extent and reduce channel removal(or cutting)
  effectively.

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Some Observations
RF-3

• If a UM is observed to have a leakage
  current of 50Nano Amps then it can be considered
  to be OK on an average.

• WE may have to set the current limit of
  the CAEN HV module to 4-5 micro Amps to hasten
  Seasoning rate.
• Even though we season at high voltages
  the NEW RC NETWORK will help in protecting
  the GAS-4 boards and FEE of the PMD.

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• It has been observed that at times when
  seasoned
• at higher voltages the current becomes high
  suddenly
• and then stays for a considerable time and all of
  a sudden
• drops to normal.
• Possibly this could be due to impurities and
  imperfections inside the honey comb which get
  charred and removed in this process.
• Its been observed that leakage current rises
  with room temp. Also when we warm the UM with a
  200 watt mercury lamp (kept at one feet away from
  the detector)the leakage current rises . When we
  will put all the FEE on the PMD some heat will be
  positively generated and so how that will affect
  the leakage current and pedestal values is a
  matter yet to be observed in the long run of the
  PMD.