A POSITION-SENSITIVE IONIZATION-CHAMBER FOR MEASUREMENT OF FISSION FRAGMENTS AND MEDIUM MASS HEAVY-IONS

A position sensitive ionisation chamber telescope is described with DELTAE(gas)-Eg.s sections which can measure simultaneously the specific energy loss DELTAE, energy E and the position of heavy ion reaction products in the median plane. The position information is derived by having a split DELTAE structure and by adopting the pulse division method for the signals collected by the two DELTAE sections. For on-line angle calibration, the E-part of the anode structure is also split into five segments. The detector was tested with fission fragments from a Cf-252 spontaneous fission source and with heavy ions from the pelletron tandem accelerator. Simultaneous measurement of DELTAE and E gives good separation for heavy and light fission fragment groups. The position resolution is found to be 1.1 mm for fission fragments. The detector has been used in heavy ion reaction studies for measuring fission fragments, providing good separation from projectile-like particles.