A NEW TYPE OF MULTIPARTICLE IMAGING DETECTOR

The foil-induced dissociation of molecular ions can provide a direct image of the stereochemical structures of small molecules. Such experiments require high-resolution measurements of the relative momenta of all dissociation fragments. In order to improve and extend previous studies of this type to a larger variety of molecules and clusters, we have developed a new type of low-pressure multiwire proportional counter. The novel feature of this large-area (25×50 cm2) multiparticle detector is that all the signals are recorded from a single two-level printed circuit board which serves as the anode. This segmented anode consists of three families of nonintersecting "wires" which are interwoven on the rear surface of the board. By redundantly determining positions and arrival times, the new segmented anode multiparticle detector provides good time resolution (100-200 ps) and high spatial resolution (0.2 mm) for detecting as many as six simultaneous particles.