Relative Humidity in Limited Streamer Tubes for Stanford Linear Accelerator Center's BaBar Detector Page: 3 of 26
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Relative Humidity in Limited Streamer Tubes for Stanford Linear Accelerator Center's BABAR
Detector. MARY-IRENE LANG (Massachusetts Institute of Technology, Cambridge, MA
02139) MARK CONVERY (Stanford Linear Accelerator Center, Stanford, CA 94309)
WOLFGANG MENGES (Queen Mary, University of London, London, UK).
The BABAR Detector at the Stanford Linear Accelerator Center studies the decay of B mesons
created in ee- collisions. The outermost layer of the detector, used to detect muons and neutral
hadrons created during this process, is being upgraded from Resistive Plate Chambers (RPCs) to
Limited Streamer Tubes (LSTs). The standard-size LST tube consists of eight cells, where a
silver-plated wire runs down the center of each. A large potential difference is placed between
the wires and ground. Gas flows through a series of modules connected with tubing, typically
four. LSTs must be carefully tested before installation, as it will be extremely difficult to repair
any damage once installed in the detector. In the testing process, the count rate in most modules
showed was stable and consistent with cosmic ray rate over an approximately 500 V operating
range between 5400 to 5900 V. The count in some modules, however, was shown to
unexpectedly spike near the operation point. In general, the modules through which the gas first
flows did not show this problem, but those further along the gas chain were much more likely to
do so. The suggestion was that this spike was due to higher humidity in the modules furthest
from the fresh, dry inflowing gas, and that the water molecules in more humid modules were
adversely affecting the modules' performance. This project studied the effect of humidity in the
modules, using a small capacitive humidity sensor (Honeywell). The sensor provided a humidity-
dependent output voltage, as well as a temperature measurement from a thermistor. A full-size
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Lang, M.I.; /MIT; Convery, M.; /SLAC; Menges, W. & /Queen Mary, U. of London. Relative Humidity in Limited Streamer Tubes for Stanford Linear Accelerator Center's BaBar Detector, report, December 15, 2005; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc873399/m1/3/: accessed November 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.