Elektron-Bremsstrahlungswirkungsquerschnitte von 180- und 380 keV-EIektronen

Abstract

The bremsstrahlung cross sections, differential in photon energy and angle have been determined by measuring the x-rays emitted from thin targets (Al₂O₃: 56,5 and 113 μg/ cm²; Au: 9,7 and 24,4 μg/cm²) for incident electron energies of 180 and 380 keV with a 5×5 inch NaI scintillation spectrometer at angles from 0 to 150 degrees. A response matrix is used to convert the measured pulse height distribution into the spectrum of photons incident on the spectrometer. The results show that in this energy region the Bethe-Heitler-Sauter (Born approximation) theory underestimates the cross sectionsd ² σ/dk · dΩ anddσ/dk. The application of the Elwert factor gives a considerable improvement. For Al₂O₃ the Elwert corrected Born approximation gives values which are generally within the limits of error of the measurements. The experimental values of theHeitler parameter$\Phi _{rad} /\bar \Phi$ are 5,0 (Al₂O₃) and 6,7 (Au) for 180 keV and 5,6 (A1₂O₃) and 7,3 (Au) for 380 keV. The angular distribution of the radiation has been compared with some characteristic angles predicted by the theory ofSommerfeldKulenkampff. Special consideration has been given to the high frequency limit. The cross sections at this energy have been derived from the correctedSauter-Fano theory and are in good agreement with the measurements.