Liquid ionization chamber initial recombination dependence on LET for electrons and photons

Abstract

The possibility of indirect measurements of linear energy transfer (LET) with a liquid ionization chamber (LIC) has been investigated by studying initial recombination losses at different applied voltages. A linear fit is made to the voltage–signal curve and the intersection point of the fit and the voltage-axis is shown to correlate with LET. The LIC applied voltages were 100–700 V, which corresponds to electric field strengths between 0.3 and 2.0 MV m–1. Several different photon and electron beams have been studied, and by using MCNPX™ the respective LET spectra have been determined. The beam qualities in this study were found to have a fluence averaged LET between 0.17 and 1.67 keV µm–1 and a corresponding dose averaged LET between 0.97 and 4.62 keV µm–1. For the experimental data in this study the linear fit method yields consistent results with respect to Monte Carlo simulated LET values. A calibration curve for LET determination is provided for the LIC used in the present work.