1. Gas Scintillation Proportional Counters

In a gas scintillation proportional counter (GSPC) the electron cloud is accelerated through a further chamber where it collisionally excites the atoms of the gas. These recombine with the emission of UV scintillation photons which are detected by a photomultiplier tube. If this is position sensitive an image of the source may be obtained. The GSPC has better resolution than the proportional counter because there is no avalanche so the noise is not amplified by the gas gain G. Also the energy required to produce a scintillation photon is small, giving better counting statistics.