Calorimetric measurement of electron stopping power of aluminum and copper between 11 and 127 keV

Abstract

The stopping powers of aluminum and copper have been measured for electrons between 11 and 127 keV. Evaporated foils of about 200-nm thickness were stretched across rings and inserted into a short cylinder which was supported by thermocouple wires. Peltier heating and cooling by one thermopile were used to control foil temperature, while another thermopile measured its temperature. Calibration was accomplished by reducing beam energy until complete absorption was obtained. Delta rays produced in the foil were returned to it by repelling electrodes. Corrections were made for increased path length in the foil due to multiple elastic small-angle scattering and for spurious heating by scattered electrons striking the ring holding the foil. After correcting for these effects, good agreement with the Bethe-Bloch formula was found.