MicroMegas detector

Due to an electric field in the order of 400 V/cm, the pair does not recombine, and the electron drifts toward the amplification electrode (the mesh) and the ion toward the cathode.

Nevertheless, the benefits of a reduce amplification gap had been demonstrated and the Micromegas concept was born in October 1992, shortly before the announcement of the Nobel Prize attribution to Georges Charpak for the invention of the wire chambers.

[4] Starting in 1992 at CEA Saclay and CERN, the Micromegas technology has been developed to provide more stable, reliable, precise and faster detectors.

The “bulk” technology consists of the integration of the micro-mesh with the printed circuit board carrying the readout electrodes in order to build a monolithic detector.

For instance, by modifying the micro-mesh in order to make it photo-sensitive to UV light, Micromegas detectors can be used to detect forest fires.

The PICOSEC-Micromegas uses a Cherenkov radiator and a photocathode in front of the gaseous volume and a time resolution of 24 ps is measured with minimum ionizing particles.

A Micromegas detector in function on the COMPASS spectrometer
Working principle of a Micromegas detector. An electron/ion pair is created (1), and electron drifts (2) to the cathode. Close to a mesh (3) is undergoes an avalanche process (4), which is detected in the intended electrode (5).
Signal induced on the readout electrode of a Micromegas detector (simulation). The blue curve shows the part of the signal induced by electrons and the red one by ions.
One of the first experiments with Micromegas detectors: COMPASS. On this 2001 pictures, we see Georges Charpak and the COMPASS Saclay team in front of the large Micromegas chambers.