About the leak microstructures

The capabilities of a new microstructure, anode point based, for the detection of gas ionizing radiations are presented. For every single detected ionizing radiation it gives a pair of “induced” charges (anodic and cathodic) of the same amount (pulses of the same amplitudes), of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the primary ionization collected. Each pulse of a pair gives the same energy and timing information, thus one can be used for these information and the other for the position. The complete lack of insulating materials in the active volume of this microstructure avoids problems of charging-up and makes its behaviour stable and repeatable. Primary avalanches with a size of more than 2.5×107 electrons (4 pC) giving current pulses with a peak of more than 0.26 mA on 100 Ω and about 30 ns duration are possible with 5.9 keV X-rays of 55Fe working in proportional region and in isobutane gas. Single electrons emitted by a heated filament (Ec<1 eV) were detected in 760 Torr of isobutane; with an estimated gas gain of 1.2×106 a counting rate of up to 800 kpulses/s per single microstructure was achieved. Three different types of sensitive-position two-dimensional read-out detectors, based on these microstructures, in development, as well as the best geometry (height of the tip with respect to the cathode) and the shapes and strengths of the electric field in the active volume of these microstructures, evaluated with Poison Superfish and Mafia programs, are presented.