STAR Beam-Beam Counter
Thermal Test of Phototube Box
A beam-beam counter (BBC) trigger detector system was
constructed and commissioned for STAR prior to the RHIC polarized proton
run that occurred between 12/20/01 and 1/23/02. All of the basic
components of that system were in place prior to the polarized proton run
after undergoing a C-AD Safety Review on 10/25/01.
A similar system will be installed in STAR prior to the start of RHIC run
3. Differences between the run 2 and run 3 systems include
the number of photomultiplier tubes (PMT) enclosed in phototube
boxes mounted on the bracket attaching the poletip to the STAR magnet has
been increased from 12 to 24. A similar design for the phototube
box has been used increasing the volume to accomodate the 24 PMT's.
the ETL 9124B used for run 2 were replaced by Burle 83112
the high voltage to the resistive voltage divider bases was
supplied by a LeCroy 4032 in run 2. The high voltage is now supplied
by a LeCroy 1440 for run 3.
commercial CAMAC and NIM readout electronics used for the
run 2 implementation of the BBC have been replaced by STAR standard digitizer
boards and data-storage and manipulation boards used for other trigger
detectors within STAR.
Following the C-AD safety review of STAR, a thermal test
of the new phototube box was requested. A test, similar to the one
completed last year, was conducted as described below.
all components of the BBC are grounded to the south electronics
platform of STAR.
||Thermistor #1: This thermistor is fixed
on the inside wall of the `base side' of the phototube box.
|Thermistor #2: This thermistor is
fixed in the middle of the magnetic support shield at the `base side' of
the phototube box.
Thermistor #3: This thermistor is fixed to
the resistive voltage divider base of PMT 13.
||Thermistor #4: This thermistor is fixed
in the middle of the magnetic support shield at the `fiber side' of the
For the thermal test, the 24 photomultiplier tubes were
each powered by applying 1400 V to their resistive voltage dividers.
These values are expected to be within 10% of those used during routine operation.
Readout of the thermistors was made at various times during the 9 hours
of continuous operation. The temperatures for the four thermistors
are shown below.
The following conclusions can be drawn:
the temperature increase is similar to what was measured
in last year's phototube box.
the resistive voltage divider base warms up in 3.4 hours.
Heat is transported to other points in the box more slowly. The time
constant for warming up the box is 5 hours.
the limiting temperatures are
box wall (thermistor #1): 33° C
middle of the magnetic support shield at the `fiber side'
(thermistor #4): 34° C
middle of the magnetic support shield at the `base side'
of the phototube box (thermistor #2): 35° C
resistive voltage divider base (thermistor #3): 36°