A Design Study of a Large Aperture Gas Threshold Cherenkov Counter Using a Wavelength-Shifter Technique for Light Collection

摘要

Using as a detection surface a POPOP-coated plexiglass sheet viewed by two 6810 phototubes, a He Cherenkov counter with 10 m. of He radiator and operating at atmospheric pressure at 14,000 feet can distinguish positive-pions from p in the energy range 30 - 140 GeV with an efficiency of at least 5% plus or minus 1%. The efficiency can possibly be considerably improved by the selection of photomultiplier tubes with optimum single photoelectron pulse height distributions and by optimizing tube voltages. Although a sample of positive-pion cosmic ray events can be labelled in spite of the small detection efficiency, unless the efficiency can be improved the event rate becomes almost prohibitively small. For Cherenkov counters used in accelerator experiments, the use of POPOP-coated plexiglass sheets for a detection surface has the following merits: A uniform efficiency for photons incident over a large area of arbitrary shape; A fast rise time provided through the use of photomultiplier tubes of small photocathode area, thus enabling the use of the Cherenkov counter in fast timing. (Author)