MICROMEGAS

Innovative Applications and Developments of Micro-Pattern Gaseous Detectors - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-4666-6014-4.ch004 ◽

2014 ◽

pp. 60-75

Keyword(s):

Parallel Plate ◽

High Energy Physics ◽

High Energy ◽

Gas Mixtures ◽

Gas Mixture ◽

Position Resolution ◽

Gain Rate ◽

Microelectronic Technology ◽

Time Position ◽

Energy Physics

This chapter describes another type of micropattern detector invented in 1995 by G. Charpak and collaborators, a micromesh gaseous detector. This detector is in fact a parallel-plate avalanche counter with a very small gap (50-100 µm) between a special cathode mesh and the anode plate. This feature offers excellent position resolution, down to 30 µm in conventional gas mixtures and close to 14 µm in some special gas mixture in which diffusion of electrons is very low. Initially, small prototypes of MICROMEGAS were made by hand. Later, microelectronic technology was used in their manufacturing, allowing the building of individual modules with active areas up to 40x40 cm2. The results from detailed studies of maximum achievable gain, rate characteristics, time-, position-, and energy resolutions of this detector are presented in this chapter, as well as a comparison with classical parallel-plate avalanche counters. Nowadays, this detector conquers more and more applications in high-energy physics and other applications.

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Comparison between Various Designs of Micropattern Detectors

Innovative Applications and Developments of Micro-Pattern Gaseous Detectors - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-4666-6014-4.ch011 ◽

2014 ◽

pp. 216-227

Keyword(s):

Energy Resolution ◽

High Energy Physics ◽

High Energy ◽

X Rays ◽

Position Resolution ◽

Advantages And Disadvantages ◽

Commercial Applications ◽

Reliability And Robustness ◽

Gas Gain ◽

Energy Physics

In this chapter a comparison between various designs of micropattern detectors is given, describing their specific advantages and disadvantages, which finally determines the fields of their applications. It is shown that at low counting rates the maximum achievable gas gain is determined by the Raether limit, which is about 106-107 electrons, depending on the design. At high counting rates, the maximum achievable gain additionally drops due to the contribution of several other effects (e.g. avalanches overlapping in space and time). Typically, micropattern detectors have a position resolution of ~30 µm, energy resolution of ~ 20% FWHM for 6 keV X-rays, and a time resolutions of ~1 ns. Some advanced designs offer even better characteristics. The diversity of micropattern detectors makes them attractive for many applications. For example, in measurements requiring simultaneously excellent time and position resolutions, mutigap multistrip detectors can be used in high energy physics applications, and hole-type structures are advantageous for the detection of visible photons. In some commercial applications, where reliability and robustness are important, spark protected detectors with resistive electrodes could be useful.

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