A new look at the PPAC

The Parallel Plate Avalanche Counter (PPAC) has been used mostly for measuring the energy loss of single, heavily ionizing particles. A PPAC is even more effective with high-energy showers for which a single event causes hundreds of electrons to pass through it. For operation at reduced pressures, the alkanes such as isobutane, C4H10 are excellent PPAC gasses with the quality of performance increasing with the size of the molecule. Under some circumstances the perfluoroalkanes such as perfluoropropane, C3F8, may be preferred. For operation at atmospheric pressure, CF4 and mixtures containing Ar and CO2 work well. (author)