Measurement of multiple scattering of 13 and electrons by thin foils

Abstract

To model the transport of electrons through material requires knowledge of how the electrons lose energy and scatter. Theoretical models are used to describe electron energy loss and scatter and these models are supported by a limited amount of measured data. The purpose of this work was to obtain additional data that can be used to test models of electron scattering. Measurements were carried out using 13 and 20 MeV pencil beams of electrons produced by the National Research Council of Canada research accelerator. The electron fluence was measured at several angular positions from 0°to 9°for scattering foils of different thicknesses and with atomic numbers ranging from 4 to 79. The angle, 1/e , at which the fluence has decreased to 1 / e of its value on the central axis was used to characterize the distributions. Measured values of 1/e ranged from 1.5°to 8°with a typical uncertainty of about 1%. Distributions calculated using the EGSnrc Monte Carlo code were compared to the measured distributions. In general, the calculated distributions are narrower than the measured ones. Typically, the difference between the measured and calculated values of 1/e is about 1.5%, with the maximum difference being 4%. The measured and calculated distributions are related through a simple scaling of the angle, indicating that they have the same shape. No significant trends with atomic number were observed.

Validation of the MCNP6 electron-photon transport algorithm: multiple-scattering of 13- and 20-MeV electrons in thin foils

“…The characteristics of the experiment are detailed in Ross et al (8) Below we provide sufficient detail to understand the simulation setup and the validation results. For the purposes of this paper, we consider a beam of electrons emerging from an accelerator exit window (see Fig.…”

“…The spatial distribution of the experimental beam in transverse directions did not have cylindrical symmetry, but could be approximated by a gaussian with a full-width at half-max of approximately 1-mm. (8) Immediately upstream of the exit window is the scattering foil that is followed by the remainder of the apparatus including a transmission monitor chamber, a helium bag, and then the detector. To sufficiently resolve the scattered electrons a significant distance between the foil and the detector was required.…”

“…New validation efforts are underway (5) that test the current version of the code containing improvements to the electron-photon transport capabilities. (6,7) The purpose of this paper is to benchmark MCNP6 against the measurements of Ross et al (8) Ross et al measured angular distributions corresponding to electron pencil beams of 13-and 20-MeV normally incident on single-element (with exception of a titanium alloy), thin foils with atomic numbers from 4 to 79. Electron fluence was measured roughly 120 cm from the beam exit window at various radii orthogonal to the beam line.…”

Recent Developments in Geant4

“…The MC/data ratio of angular distribution widths measured at the 1/e level for the Urban model of GEANT4 10.0. Results are shown for a 13 MeV beam on the target materials and thicknesses of the electron scattering benchmark [75]. …”

“…15 illustrates the ratios of simulated to measured angular distribution widths taken at the points where the distribution falls to 1/e of the peak value. The measured data taken from literature [75] include a set of different target materials (Be, C, Al, Ti, Cu, Ta, and Au) with an accuracy of about 1%. Using the G4UrbanMscModel of GEANT4 release 10.0, the predicted angular distribution widths are close to the data with a maximum deviation not exceeding 3% for both test cases of 13 and 20 MeV.…”