Recent improvements to RC-line encoded position-sensitive proportional counters

Conference · Sat Jan 01 04:00:00 EST 1977

OSTI ID:5161454

Borkowski, C J; Kopp, M K

Continuing research on the principles of position encoding with RC lines has advanced the design of position-sensitive proportional counters (PSPCs) to meet the requirements for high count rates (>10/sup 5/ counts/sec) and good spatial resolution (>10/sup 4/ spatial elements) in small-angle scattering experiments with x rays and neutrons. Low-noise preamplifiers were developed with pole-zero cancellation in the feedback circuit and modular linear amplifiers with passive RCL shaping which, compared to previous designs, reduce output saturation at high count rates approx.20 times and shorten the position signal processing time to <1 ..mu..sec. Using resistive self-heating and propylene decomposition, the conductance and film thickness of pyrolytic-carbon anodes were increased to match the RC time-constants of line PSPCs with the linear amplifiers, to reduce the effects of electron erosion of the anodes at high count rates, and to improve the PSPC linearity. A large-area PSPC (480 x 780 mm/sup 2/) for low-energy (<60 keV) photon imaging was developed. The electronic uncertainty in the position measurement of 20-keV photons is <0.5 mm (fwhm) in both dimensions. The technology developed for this PSPC is applicable to the design of large-area detectors (>800 x 800 mm/sup 2/) for the measurement of small-angle scattering with neutrons. The method of electronic thickness discrimination was applied to change the effective thickness of an area PSPC from 12 to 2 cm whenever the molybdenum target of an x-ray generator was changed to a copper target. This thickness adjustment increased the signal-to-background ratio by a factor of approx.6 for the 8-keV photons from the copper target, while maintaining a >90% detection efficiency.

• Research Organization: Oak Ridge National Lab., Tenn. (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5161454
• Report Number(s): CONF-771077-5
• Country of Publication: United States
• Language: English

Related Subjects

440101* -- Radiation Instrumentation-- General Detectors or Monitors &amp; Radiometric Instruments
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
AMPLIFIERS
ANODES
COUNTING RATES
ELECTRODES
ELECTRONIC EQUIPMENT
IONIZATION CHAMBERS
MEASURING INSTRUMENTS
MULTIWIRE PROPORTIONAL CHAMBERS
POSITION SENSITIVE DETECTORS
PREAMPLIFIERS
PROPORTIONAL COUNTERS
RADIATION DETECTORS
READOUT SYSTEMS
RESOLUTION
SCATTERING
SMALL ANGLE SCATTERING
SPATIAL RESOLUTION