Detectors for alpha particles and X-rays operating in ambient air in pulse counting mode or/and with gas amplification

Abstract

Ionization chambers working in ambient air in current detection mode are attractive due to their simplicity and low cost and are widely used in several applications such as smoke detection, dosimetry, therapeutic beam monitoring and cetera. The aim of this work was to investigate if gaseous detectors can operate in ambient air in pulse counting mode as well as with gas amplification which potentially offers the highest possible sensitivity in some measurements for example for alpha particle detection or high energy x-ray photon or electron detection. To investigate the feasibility of this method two types of open-end gaseous detectors were build and successfully tested. The first one was a single wire or multiwire cylindrical geometry detector operating in pulse mode at a gas gain of one (pulse ionization chamber). This detector was readout by a custom made wide -band charge sensitive amplifier able to deal with slow induced signals generated by slow motion of negative and positive ions. The multiwire detector was able to detect alpha particles with efficiency close to 22%. The second type alpha detector was an innovative GEM-like detector with resistive electrodes operating in air in avalanche mode at high gas gains (up to 10 4 ). This detector can also operate in a cascaded mode or be combined with other detectors, for example with MICROMEGAS. This detector was readout by a conventional charge -sensitive amplifier and was able to detect alpha particles with 100% efficiency. This detector could also detect x-rays photons or fast electrons. A detailed comparison between these two detectors is given as well as comparison with the commercially available alpha detectors. The main advantages of gaseous detectors operating in air in a pulse detection mode are their simplicity, low cost and high sensitivity. One of the possible applications of these new detectors is alpha particle background monitors which, due to their low cost can find wide application not only in houses, but in public areas: airports, railway station and so on.

Ionization Chamber of New Conception for Enviromental Gas Radon Measurements

“…Similary to Charpak et al method, developed in [4] [5] [6], a preliminary test with α particles at 5.5 MeV of energy was performed, using a 241 Amsource of known activityin order to evaluate the detector voltage characteristic. The amplitude of the observed pulse from the detector plotted versus the voltage applied to the electrodes is shown in Figure 4.…”

Long-distance detection of alpha-radioactivity: Method and device

“…The detector works in air in the counting mode that provides sharp selectivity and high accuracy of measurements (Simakov et al, 1999;Simakov, 2005;Charpak et al, 2008;Charpak et al, 2011). Fig.…”

Open Detector of Alpha Particles based on GEM-like Structure

“…It means that air ionization chambers or open chambers allow to measure ionization without electron multiplication and to test the detectors of this type by means of radioactive sources with the minimum dark current at the level of 10 pA. Detectors of this type find application as in the medical purposes at radiation therapy with use of different types of the ionizing particles, and for scientific experiments in the field of physics of nuclear and elementary particles at measurement of coordinates and losses of energy with an energy threshold up to 0.3 MeV/nucleon [6].…”