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
photomultiplier tubes.
-
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run 2 implementation of the BBC have been replaced by STAR standard digitizer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.
-
all components of the BBC are grounded to the south electronics
platform of 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.
|
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
phototube box. |
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°
C
