Development of the MICROMEGAS detector for measuring the energy spectrum of alpha particles by using a 241 Am source

We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting a particles emitted from an 241 Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of a particles from the 241 Am source can be varied by changing the flight path of the a particle from the 241 Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the a particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for a particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that a particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGAS detector for a particles under the present conditions is found to be ~97.3%.