New Method for Determination of Recoil Electron Vectors in Electron Tracking Compton Camera (ETCC)

Abstract

The electron tracking Compton camera (ETCC) is expected to visualize and quantify gamma-ray. The feature of the ETCC is that it can uniquely determine the direction of incident gamma-ray by measuring recoil electron tracks. The main difficulty is the analysis method of recoil electron tracks to determine the position where the Compton scattering occurs and the recoil electron vector. Especially in case of low energy recoil electrons of 80 keV or less, it is too difficult to determine the vector because the length of the recoil electron tracks is as short as 40 mm or less. Short electron tracks make difficult to achieve a high resolution of the gamma-ray image which is estimated with the full width at half maximum (FWHM) of 137Cs point source image. We have developed a new method to determine the recoil electron vector and applied it to the 137Cs point source data. As a result, the FWHM of 137Cs point source image has been improved from 56 degrees to 38 degrees.