Subject: 5B03-1 and 5B04-1 back in ACQ
Ioanni.Katsavounidis@lngs.infn.it
Date: Thu Dec 23 1999 - 10:37:26 EST
Ciao a tutti,
Tanks ends 5B03-1 and 5B04-1 have been opened yesterday and put
back in ACQ today. These two channels have been flagged during gain
setting as follows:
- 5B03-1: "08NOV99 MO/EK : Needs -1820V for 4mV gain. Open and
replace bases"
- 5B04-1: "08NOV99 MO/EK : variable brightess/bright/filled spe
Open tank end and replace bases"
While working on these tank ends, the following things were
noticed:
(1) 5B03-1 has its tank-end oil-filling tube shorter than normal.
As a result, roughly 1cm of oil remains in the tank even when
oil stops coming out of the tankend.
(2) 5B04-1 had the pin-20 to magnetic shield resistor chains (both
for 5B04-10 and 5B04-11) severely damaged. In fact, when changing
the corresponding bases, these chains broke and they were replaced.
(3) 5B04-1 had no -10 to -11 continuity between magnetic shields.
By fastening clips, it was brought to ~ 7 Ohm.
(4) After changing bases, big differences in the operating HVs were
found as follows:
5B03-10 : -1465 V
5B03-11 : -1610 V
5B04-10 : -1425 V
5B04-11 : -1610 V
For this reason, we decided to swap tubes in order to match their
HVs.
PMT serial # 6927 was previously on 5B03-10, now on 5B04-11
PMT serial # 7678 was previously on 5B04-11, now on 5B03-10
(5) After performing the above mentioned swap, continuity problems
among magnetic shields requested re-installing all relevant
clips and related tank end material on 5B03-1 (the one with
1cm of oil...)
Final result: ~ 4 Ohm between 5B03-10 and 5B03-11. +
1 white lab coat trashed
(6) Checking the resulting signals, the following bases and HVs were
found:
5B03-10 : -1610V , R(base) = 9.4 MOhm
5B03-11 : -1610V , R(base) = 9.3 MOhm
5B04-10 : -1490V , R(base) = 9.5 Mohm
5B04-11 : -1465V , R(base) = 9.4 Mohm
It is quite strange that 3 out of the 4 HV values are identical
(taking into account the above mentioned swap), but the 4th one
(5B04-10) according to Erik needed -1425V for 4mV gain and according
to Massimo needed -1490V for 4mV gain. Could it be a consequence of
the fact that Erik was using the handheld unit to set HV value while
Massimo was using the HV program on SCINTSOFT ??
Resulting splitter box values:
5B03-1 : 0
5B04-1 : 160 KOhm on side -11 (theoretical), 164 Kohm (measured)
(7) Checklists, PMTHV.DAT files and paper PMT logbook have been
updated and these channels are now back in ACQ.
(8) The 4 bases taken out from these 2 tank ends were all "old" (non HV)
bases and in addition had their 2.2 Mohm resistor way off tolerance
(measuring anywhere from 3.0 to 5.0 Mohm). These 4 bases, and all
other bases on the soldering bench have now been modified and are
ready to be used.
A presto,
Ioannis
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