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Multiwire proportional counters Westlund, Wayne Arthur


The aim of this work is twofold: first, to develop a multilayered multiwire proportional chamber which would be useful as a position-sensitive detector in tracking the path of a beam of elementary particles and identifying the particles by their energies; and second, to measure the operating characteristics of such a chamber. A chamber has been developed which consists essentially of a stack of printed circuit board frames to which are soldered separately many parallel fine wires. A signal plane at ground potential has on either side planes at high voltage. The chamber is made gas-tight by mylar film on both ends and gas is flowed through at atmospheric pressure. The electrostatics of this type of chamber follows exactly the theory derived for the familiar proportional counter, of which the multi-wire proportional chamber is an extension. The pulse characteristics measured for the chamber agree closely with those values predicted by the theory. Such a chamber with signal wires of .0005 inch (12.7μm) spaced .10 inch (2.5 mm) apart with planes separated by ⅛ inch (3.2 mm) runs well at 1800 volts with a gas amplification factor of about 10⁴, giving a pulse 5 mv high with risetime of 25 nsec. The energy resolution shows a FWHM of 1 kev for the 5.9 kev x-ray of Fe⁵⁵, while the time resolution is at least 25 nsec. The positional sensitivity is at least as fine as the wire spacing.

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