Electron–atom bremsstrahlung cross sections in the 20–100 keV energy region: absolute measurements for $6\leqslant Z\leqslant 79$ and comparison with theoretical databases

Abstract

We report absolute measurements of doubly differential electron-atom bremsstrahlung cross sections for energies in the keV region and elements with atomic numbers 6, 13, 52, 73 and 79. Thin targets were irradiated at the low-energy beam line of the São Paulo Microtron with 20, 50, 75 and 100keV electrons. For each element and energy, the photon spectra were collected simultaneously with three HPGe detectors at the emission angles of 35°, 90°and 131°. The deconvolution of the bremsstrahlung spectra was done adopting an analytical model for the spectrometers' response functions. The resulting doubly differential cross sections are compared with the available partial-wave calculations of ordinary bremsstrahlung. Based on this comparison, we discuss some features of the experimental spectra that might be related to the emission of polarization bremsstrahlung.

Absolute cross sections of ultra-soft x-ray radiation in electron scattering upon atoms and the soft-photons approximation

“…This article also provides references to previous absolute measurements for thin solid targets. The results obtained in [9] are consistent with the theoretical data presented in the Refs. [10][11][12].…”

“…The measurements in Ref. [9] did not observed polarization BS. However, this fact is not surprising, since the atoms of the used targets do not have large polarizabilities in the regions of the BS photon frequencies under consideration.…”

“…However, this fact is not surprising, since the atoms of the used targets do not have large polarizabilities in the regions of the BS photon frequencies under consideration. It is noteworthy that in [9], as in [5], the agreement between theory and experiment worsens as the photon energy decreases. This statement is considered by the authors of Ref.…”

Detetores semicondutores de fótons na investigação das interações dos elétrons e fótons com a matéria

“…Por outro lado, quando se calibra o detetor com fontes radioativas, ou quando se coloca um destes detetores em um arranjo de irradiação, normalmente se considera a posição da cápsula alinhada com o material a medir. No caso específico dos trabalhos de Garcia [30,32,34,33], ao saber como estava localizado o cristal na cápsula, esta foi posicionada de forma a compensar o desalinhamento do cristal.…”

“…HPGe Planar Ortec 1000 Series Hyperpure Germanuim, com um cristal de 12,5 mm de raio e 10 mm de espessura, janela de entrada de Be de 0,25 mm de espessura. Relacionado aos trabalhos das referências [60,30,34,33]. Este detetor trabalhou conectado a uma eletrônica analógica da ORTEC, composta por: uma fonte de tensão; um amplificador 572 e um multicanal (ASPEC 927).…”