Applications Proportional counter

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1 applications

1.1 spectroscopy
1.2 photon detection
1.3 radioactive contamination detection
1.4 guidance on application use





applications
spectroscopy

the proportionality between energy of charged particle travelling through chamber , total charge created makes proportional counters useful charged particle spectroscopy. measuring total charge (time integral of electric current) between electrodes, can determine particle s kinetic energy because number of ion pairs created incident ionizing charged particle proportional energy. energy resolution of proportional counter, however, limited because both initial ionization event , subsequent multiplication event subject statistical fluctuations characterised standard deviation equal square root of average number formed. however, in practice these not great predicted due effect of empirical fano factor reduces these fluctuations. in case of argon, experimentally 0.2.


photon detection

proportional counters useful detection of high energy photons, such gamma-rays, provided these can penetrate entrance window. used detection of x-rays below 1 kev energy levels, using thin walled tubes operating @ or around atmospheric pressure.


radioactive contamination detection

proportional counters in form of large area planar detectors used extensively check radioactive contamination on personnel, flat surfaces, tools , items of clothing. in form of installed instrumentation because of difficulties of providing portable gas supplies hand-held devices. constructed large area detection window made such metallised mylar forms 1 wall of detection chamber , part of cathode. anode wire routed in convoluted manner within detector chamber optimise detection efficiency. used detect alpha , beta particles, , can enable discrimination between them providing pulse output proportional energy deposited in chamber each particle. have high efficiency beta, lower alpha. efficiency reduction alpha due attenuation effect of entry window, though distance surface being checked has significant effect, , ideally source of alpha radiation should less 10mm detector due attenuation in air.


these chambers operate @ slight positive pressure above ambient atmospheric pressure. gas can sealed in chamber, or can changed continuously, in case known gas-flow proportional counters . gas flow types have advantage tolerate small holes in mylar screen can occur in use, require continuous gas supply.


guidance on application use

in united kingdom hse has issued user guidance note on selecting correct radiation measurement instrument application concerned [1]. covers radiation instrument technologies, , useful comparative guide use of proportional counters.








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