A gas ionization counter for heavy ion detection

The design and working of a gas ionization counter developed for detection of low energy heavy ions are described. The counter has an effective depth of 4 cm and is backed by 200 mm2 area Si surface barrier detector of 330 micron thickness. The electric field for charge collection is applied parallel to the incident particles. On account of this axial field, the pulse height is independent of position and no grid is required. The detector has been tested with 5.5. MeV alpha particles using a gas mixture of 90 per cent argon and 10 per cent methane. (M.G.B.)