MICROMEGAS: A HIGH-GRANULARITY POSITION-SENSITIVE GASEOUS DETECTOR FOR HIGH PARTICLE-FLUX ENVIRONMENTS Y. Giomataris, Ph. Rebourgeard and J.P. Robert, G. Charpak This paper presents a novel gaseous detector, MICROMEGAS, designed for high particle-flux environments. It is a two-stage parallel-plate avalanche chamber with a small amplification gap (100 µm) and a conversion-drift space. The detector uses a thin electroformed micromesh to separate the conversion space from the amplification gap. The micromesh allows for efficient collection of ionized electrons and efficient evacuation of positive ions, resulting in a high gain (up to 10^5) and high granularity. The detector has a high rate capability, with fast signal collection (≤1 ns) and good spatial resolution (inferior to 100 µm). The detector is designed to operate in a stable fashion for long irradiation periods and can achieve higher electron multiplication factors than conventional detectors. The detector is constructed using a combination of microelectronics and gas technology, with a thin Kapton substrate and gold-coated copper anode strips. The detector has been tested with various radioactive sources, including ^254Cf and ^241Am, and has shown good performance in terms of energy resolution and signal-to-noise ratio. The detector is simple to operate, cost-effective, and has the potential for high counting rates beyond 10^6 particles/mm²/s. The detector is a promising candidate for high-rate position-sensitive particle detection in high-flux environments.MICROMEGAS: A HIGH-GRANULARITY POSITION-SENSITIVE GASEOUS DETECTOR FOR HIGH PARTICLE-FLUX ENVIRONMENTS Y. Giomataris, Ph. Rebourgeard and J.P. Robert, G. Charpak This paper presents a novel gaseous detector, MICROMEGAS, designed for high particle-flux environments. It is a two-stage parallel-plate avalanche chamber with a small amplification gap (100 µm) and a conversion-drift space. The detector uses a thin electroformed micromesh to separate the conversion space from the amplification gap. The micromesh allows for efficient collection of ionized electrons and efficient evacuation of positive ions, resulting in a high gain (up to 10^5) and high granularity. The detector has a high rate capability, with fast signal collection (≤1 ns) and good spatial resolution (inferior to 100 µm). The detector is designed to operate in a stable fashion for long irradiation periods and can achieve higher electron multiplication factors than conventional detectors. The detector is constructed using a combination of microelectronics and gas technology, with a thin Kapton substrate and gold-coated copper anode strips. The detector has been tested with various radioactive sources, including ^254Cf and ^241Am, and has shown good performance in terms of energy resolution and signal-to-noise ratio. The detector is simple to operate, cost-effective, and has the potential for high counting rates beyond 10^6 particles/mm²/s. The detector is a promising candidate for high-rate position-sensitive particle detection in high-flux environments.