Micromegas (particle detector)

The “Micromegas “ (Micro-MEsh Gaseous Structure) detector is a gaseous particle detector coming from the development of wire chamber. Invented in 1992 by Georges Charpak and Ioannis Giomataris, the Micromegas detectors are mainly used in experimental physics, in particular in particle physics, nuclear physics and astrophysics for the detection of ionising particles.

The Micromegas are light detectors in order to minimize the perturbation on the impinging particle. From their small amplification gap, they have fast signals in the order of 100 nanoseconds. They are precise detectors with a spatial resolution below one hundred micrometers. Nowadays, the use of the Micromegas technology is growing over the different fields of experimental physics.

A particle detector is used to detect a passing particle and obtain information such as its position, arrival time and momentum. In experimental physics, the particle is usually coming from a particle accelerator but it can also come from space (cosmic ray) or from a nuclear reactor.

The Micromegas detector, as every gaseous detector, detects particles by amplifying the charges that have been created by ionisation in the gas volume. In a Micromegas detector, this gas volume is divided in two by a metallic micro-mesh (“Micromesh” on the schematic) placed between 25 μm and 150 μm of the readout electrode (Strips on the schematic). The micro-mesh is the key element since it allows, at the same time, a high gain of 10⁴ and a fast signal of 100 ns.

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