Two Wireless Imaging Proportional Counters

Abstract

Two types of wireless position sensitive X -ray proportional counters are under development at the Danish Space Research Institute. One detector -the microstrip proportional counter -employs very narrowly spaced conducting strips deposited on an isolating substrate instead of wires. The gas gain is uniform over the entire detector area and the achievable energy resolution is close to or better than the best achievable for single wire proportional counters. The position readout is made using a wedge and strip electrode mounted on the back -side of the insulating glass substrate. The second detector employs a uniform electric field between two parallel electrodes in order to achieve amplification. Parallel electrodes have better energy resolution, better timing resolution and are easier to construct and more durable than multiwire chambers. The parallel gap is formed between an etched Ni mesh and a segmented anode in the form of a wedge and strip electrode. The X -ray photon energy is derived from the mesh electrode, whereas the position information is taken from the anode. Submilimeter position resolutions have been achieved.In both detectors the energy signal has a very fast risetime and background rejection based on pulse shape analysis is, therefore, very efficient. The background rejection efficiencies achieved and the optimum rejection method for spaceborne detectors will be discussed.

JEM–X: The X-ray monitor aboard INTEGRAL

“…Particles which enter through the top or bottom are rejected by a pulse shape analysis technique, (Budtz-Jørgensen et al 1994). The rejection efficiency for these events is augmented by using a "footprint" evaluation.…”

<title>Status of the stellar x-ray polarimeter for the Spectrum-X-Gamma mission</title>

“…The IPc design incorporates three charged particle vetos: a rear anticoincidence layer, a four-sided anticoincidence shield surrounding the active gas volume, and pulse shape discrimination. For pulse shape discrimination we use a technique developed by Budtz-Jorgensen (1989). The pulse from the anode is passed through two shaping amplifiers: one with a slow time constant (4 .tsec), the other with a fast time constant (< 500 ns).…”