A Simple Technique for Identifying Natural Alpha Emitters

It is well known that the pulse-height spectrum for the two-electrode parallel plate ionization chamber is rectangular in shape with the lower and upper bounds due to the charged particles making angles 0deg and 90deg respectively with the electric field. Clearly, by allowing charged particles of narrow range of angles only, the pulse-height spectrum can be reduced to a narrow peaking spectrum. We have made Monte Carlo simulation of the pulse-height spectra for alpha particles of energies in the range 3-9 MeV for the above ionization chamber for several electrode separations and for several narrow angular openings and optimized the electrode separation for each angular opening in order to get a linear peak position versus alpha energy plot. Each combination of the electrode separation and angular opening with the linear plot of peak position versus energy then makes the detector an important tool for identifying the alpha activities due to different natural alpha emitters found in the rock samples, sediments and environment. The emission of the charged particles from the source, charge carrier generation in the active volume, transport of the charge carriers, induction of charges on the electrodes, pulse shaping with a simple CR-RC network having pole-zero cancellation, etc. have been incorporated in these simulations. Some of these results have already been verified experimentally. Further experimental work is in progress.