[Halld-cal] BCAL update

[Elton Smith]

Hi all,

I thought it is worth sending a brief update on the status of BCAL 
checkout, especially since the GlueX meeting was cut short.

A week ago we started turning on the BCAL and immediately found that 
most (~75%) of all channels would not hold HV (i.e. 75 V), This problem 
was traced to the cables that run from a distribution panel to the 
module and deliver the HV and LV power to the module. The specific 
problem was a rubber sleeve inside the connector assembly that made the 
connectors "splash proof." This sleeve often turned out to be conductive 
with a resistance in the range of 50-100 kOhm and caused leakage from HV 
to LV and vice-versa. Fernando will be consulting with the factory 
regarding the specifications of the sleeve and whether the conductivity 
is from a bad batch or a known problem. In any case, the good news is 
that the sleeve is not needed for our purpose and they have been cut out 
of the cables on the upstream modules (the downstream will be 
scheduled). Following the fixing of the cables, I have checked signals 
on all upstream modules. Here is a quick status for the upstream 
(downstream is not yet ready for testing):

* The upstream chiller has been operating for about a week now and is 
keeping the upstream cooling plates at about 18 deg C.
* The RTDs on the cooling plates read within 1 degree of each other 
(except for 3 problems)
* The N2 system is keeping the system dry. The humidity ranges from 1.3% 
to 20% (corresponding dew points: -34 degC and -3 degC)
* The EPICS slow control GUIs are working correctly with the expected 
map between HV and LV levels and detector elements.
* M33 has the "sleeve" symptom and must have been missed. (Will be 
repaired Monday).
* M46, V1 trips and M13, V2 trips. Neither trip when the module is 
disconnected. We will investigate these further on Monday and may need 
to remove the readout assemblies to fix the problem.
* Signals A0-A7 of every module were checked on the scope for noise. 
Three signals were missing.

Cheers, Elton.



-- 
Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave STE 16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax