Design and performance of a vertical drift chamber for heavy ion applications

Abstract

A vertical drift chamber has been specifically designed and constructed as a focal plane detector for heavy ion applications. Tests were performed with 12C(129 MeV), 14N(176 MeV) and 16O(140 MeV) ions and a magnetic spectrometer. The operating characteristics at 50, 100 and 200 Torr were investigated using isobutane as the counter gas. The intrinsic precision of the drift cells was determined to be about 75 μm at 200 Torr with isobutane. This value is indicative of an intrinsic detector resolution of 0.1 mm (fwhm) in track position and 7 mrad (fwhm) in track angle, for angles between 30 and 44°. Slightly larger values were measured at the lower pressures. Measurements of the electron drift times, the wire identification resolution and the counter efficiency were made from multiple sweeps of the elastic peak across the counter by ramping the magnetic field of the spectrometer. Details of the detector design, operation and performance are presented.