Study of the response of silicon detectors for alpha particles

Numerous radon measurements are carried out using silicon detectors directly in the environment. This new kind of alpha radiation measurement has been developed because the reduced cost makes it possible to replace the usual plastic track detectors. At our laboratory, an alpha particle detector has been designed from a commercial silicon photodiode. This type of detector can determine the device response perfectly in any kind of environment. Different spectrum analyses have been conducted in the laboratory and field to define the exact origin of counted alpha particles. We studied the response for different radon and thoron concentration levels and observed the energy of the detected alpha particles. We carried out some of these experiments with gas flux, and some without, to show the effects of interactions with surfaces to obtain thermodynamic equilibrium in the detection chamber. Finally, the silicon diodes that we tested measure the alpha particles of the decay products (polonium) from the radon and the thoron, but very weakly from the gases themselves. Thus, it is possible to make mistakes when measuring the radon if the count of alpha particles is performed without spectrum analysis. One reason for this is that the decay progenies of the radon are solid radio-elements with thermodynamic proprieties different from gases.