Introduction

After the discovery of the first extra-solar X-ray source in 1962 with a gaseous detector, the proportional counter became the workhorse instrument of soft X-ray astronomy for nearly four decades. The origin of gaseous detectors dates back to the early twentieth century, when Rutherford and Geiger published in 1908: "An electrical method of counting the number of a-particles from radioactive substances" [23]. Cosmic rays were discovered in 1912 with a gaseous detector by V. Hess. During the first half of the twentieth century much progress was made in the technology of gaseous detectors in the fields of nuclear and cosmic-ray physics [8]. For instance, the discovery of the effect of quench gases allowed a stable operation of gas detectors [28]. Ionization-dependent output signals of gas counters were observed first by Geiger and Klemperer [7]. About 10 years later, proportional counters were developed [13]. First attempts to operate multiwire detectors were carried out in conjunction with the Manhatten project [22]. In 1968, Charpak and collaborators succeeded in the development and operation of multiwire proportional counters (MWPC) [4]. These detectors combine the advantages of a large sensitive area with multidimensional event parameter sensing. Many innovative ideas arose from the group around Charpak. The development of gaseous detectors is still going on. New detector types like the micro strip gas chamber (MSGC) [15] and micro pattern gas detectors (MPGD) like the gas electron multiplier (GEM) have been described [25].

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