An apparatus to study the energy and angular distributions of electron-bremsstrahlung photons from gaseous targets

Yadav, Namita; Bhatt, Pragya; Singh, R. N.; Singh, B. B.; Quarles, C.A.; Shanker, Rama

doi:10.1016/j.radphyschem.2013.10.013

Cited by 6 publications

(4 citation statements)

References 26 publications

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“…It should be noted that theoretical work related to solid‐target experiments and experimental data obtained from gas‐target experiments both suggest that PB intensity is greatest at low photon energies and that the intensity decreases as photon energies increase. While the extent of the PB contributions to the total bremsstrahlung spectrum in experiments involving electrons incident on solid targets remains somewhat controversial, there is little controversy concerning PB contributions in experiments involving gaseous targets …”

Section: Discussionmentioning

confidence: 99%

Comparison of the bremsstrahlung absolute probability densities produced by experiment and PENELOPE for low‐energy (keV) electrons incident on solid silver

2015

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There has been some recent controversy concerning whether or not polarizational bremsstrahlung (sometimes referred to as 'atomic bremsstrahlung') contributes to the total bremsstrahlung spectrum in experiments involving electrons incident on solid targets. We have compared the bremsstrahlung absolute probability density predictions of the widely used Monte Carlo code, PENELOPE, to the results of experiments involving 17.5-keV and 20-keV electrons incident on a thick silver target. Comparisons of the results of our experiments to the predictions of the PENELOPE code, which is based on ordinary bremsstrahlung alone, suggest that there were no significant polarizational bremsstrahlung contributions to the total bremsstrahlung spectra in our experiments.

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Section: Discussionmentioning

confidence: 99%

Comparison of the bremsstrahlung absolute probability densities produced by experiment and PENELOPE for low‐energy (keV) electrons incident on solid silver

2015

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“…The experimental set-up employed in the present work for studying the angular and energy distributions of BS radiation emitted from 4.0 keV electrons incident on free N 2 molecules is similar to the one used in our previous work of Yadav et al [17] except with few modifications. Briefly, for performing the present measurements, a Pfeiffer turbo-molecular pump (TPH-240) of 240 l s −1 pumping speed coupled with a twostage Edward-8 rotary pump was used.…”

Section: Methodsmentioning

confidence: 99%

Experimental evidence of molecular coherence effects in the bremsstrahlung radiation processes

Prajapati

Kumar

Singh

et al. 2019

J. Phys. B: At. Mol. Opt. Phys.

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The first experimental evidence of Young-type interferences is presented in bremsstrahlung (BS) processes by measuring the double differential cross sections (DDCS) of BS photons emitted from a two-centre N 2 molecule under impact of 4.0 keV electrons. The spectra were recorded for emission of photons in the angular range of 45°-120°and the energy range of 2.0-3.8 keV using a Si PIN photodiode detector (FWHM=165 eV at 5.9 keV). The measured variation of DDCS ratio of N 2 to Ar as a function of photon energy shows no obvious signature of interference structure. However, the measured angular distribution of the intensity ratio of BS photons of N 2 to Ar is found to exhibit the noticeable oscillations. Furthermore, a clear oscillatory structure is observed in the angular distribution of BS photons if the intensity of photons emitted from N 2 molecules at angle θ to the intensity of photons emitted at angle 90°, i.e. I(θ)/I(90°) is plotted as a function of emission angle. Noting the fact that, only one theoretical work on coherence effects in BS processes under low-energy electron impact with homonuclear diatomic molecules is reported in the literature by Borie et al (1970 Phys. Rev. A 2 1443) which fails to explain the observed oscillations and shows orders of magnitude difference in the amplitude and mismatch in the shape of oscillations. The presence of observed oscillations is suggested to arise due to coherent superposition of BS photons of a given energy emitted in scattering of 4.0 keV electrons with a two-centre N 2 molecule. Strong disagreement between our measurements and the calculations from Borie et al theory clearly suggests that a more refined and adequate theoretical model together with additional experimental investigations are needed to verify the present observations.

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“…The only study on the angular distributions of DDCSs of BS radiation produced by electrons of energy in the range 3-15 keV incident on Ar, Kr and Xe was done by Aydinol et al [32]; in these studies, the observed anisotropy of the BS radiation was explained by a modified Sommerfeld formula. Recently, Yadav et al [33] have conducted the measurements of angular and photon energy distributions of the BS photons produced from 4.0 keV electrons incident on free Ar atoms with reasonable reduction (about a factor of 5) of TTB background. They have compared the relative DDCSs of BS photons with the theoretical predictions of the OBS and the SA and have concluded that further reduction of TTB background is necessary to establish the existence of PBS contribution with greater confidence.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, we report on the experimental and theoretical results of absolute DDCSs of BS radiation produced from 4.0 keV electrons incident on free Ar atoms after making a significant reduction of TTB contribution almost by a factor of 30 compared to the one obtained without TTB reduction. This has been made possible by modifying the experimental set-up that was used in our previous work [33] with respect to collimation of the BS photons generated from the electron-Ar collision reaction. In this new configuration, the BS photons generated at the collision center were monitored by a system with a long graphite collimator (30 mm) with end apertures of about 2 mm and the detectors all set to lie exactly in the line of sight of the detector; thus viewing a very small cross section area of the material of the chamber wall relevant to TTB photon contribution.…”

Section: Introductionmentioning

confidence: 99%

Absolute Double Differential Cross Sections of Bremsstrahlung Produced from 4.0 keV Electrons Incident on Free Ar Atoms

Prajapati

Singh

Kumar

et al. 2020

Atoms

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New results are reported on the measurements of absolute double differential cross sections (DDCSs) of bremsstrahlung produced from 4.0 keV electrons incident on free Ar atoms in the angular detection range of 45°–120°. A significant reduction of the thick target bremsstrahlung (TTB) of the chamber wall and of the photon transmission windows has been achieved by modifying the experimental set-up used previously; a large reduction of TTB in the present experiments is supported by the results of our model calculations for the ratio of TTB background to the normal bremsstrahlung (NB) spectrum carried out for the employed geometry of the experimental set-up. The results of photon energy distribution measured at different angles and those of angular distributions of photons of a given energy are compared with theoretical predictions of Kissel–Quarles–Pratt (KQP) theory for ordinary bremsstrahlung and with predictions of total bremsstrahlung including polarization bremsstrahlung (PBS) of the stripping approximation (SA). A satisfactory agreement observed between experiment and predictions using SA theory for absolute DDCSs of bremsstrahlung provides evidence for an appreciable contribution of polarization bremsstrahlung at the considered impact energy of electrons on one hand, while on the other hand, it exhibits a large discrepancy (about a factor of 2) in DDCSs of bremsstrahlung photons obtained by experiment and by KQP theory for photon energy distributions at all detection angles measured in these experiments. In addition, present results of the angular dependence of photons of different energies show anisotropic distributions and they are found to be in reasonable agreement with both KQP and SA theories. The satisfactory agreement between experiment and theory for angular distributions is an indication of a significant reduction of the background produced from TTB photons.

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An apparatus to study the energy and angular distributions of electron-bremsstrahlung photons from gaseous targets

Cited by 6 publications

References 26 publications

Comparison of the bremsstrahlung absolute probability densities produced by experiment and PENELOPE for low‐energy (keV) electrons incident on solid silver

Comparison of the bremsstrahlung absolute probability densities produced by experiment and PENELOPE for low‐energy (keV) electrons incident on solid silver

Experimental evidence of molecular coherence effects in the bremsstrahlung radiation processes

Absolute Double Differential Cross Sections of Bremsstrahlung Produced from 4.0 keV Electrons Incident on Free Ar Atoms

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