Non-linearities and entrance window effects in large solid-angle gas ionization detectors

The performance of a large solid-angle, position-sensitive, gas ionization detector used for elastic recoil detection analysis with heavy ions has been investigated in detail. In particular, a front electrode in the anode, that was intended for measurements of the initial energy loss of incident heavy ions, proved especially valuable as a means of understanding the non-linearities inherent to the methods of spatial determination employed by a widely used type of detector, and the influence of the window on the collection of electrons at the anode. Alternative design features are proposed to remove the non-linearities and to allow the measurement of the energy loss near the detector entrance.