Background: Producing the ideal therapeutic electron beams from a clinical linear accelerator (Linac), is crucial to optimize dose delivery in radiotherapy. The aim of this study was to investigate the properties of electron beams with and without the scattering foil. Materials and Methods: Varian Linac 2100CD head was simulated by means of MCNPX-2. 7 program. After validation with measured data, scattering foils were removed and then different dosimetric properties of 6 and 9 MeV electron beams such as depth dose percentage, dose profile, range, surface dose, dose rate and photon contamination were calculated and compared for field sizes ranging from 0. 25×0. 25 to 10×10 cm2 in three states with primary and secondary scattering foil (SF), without primary scattering foil (PSFF) and without primary and secondary scattering foil (SFF). Results: By removing the scattering foils, dose rates and surface doses were increased more than 25 times in 0. 25×0. 25 cm2 field, and in the bigger fields, it was less in 10×10 cm2 field, almost 4 times and the photon contamination is reduced by 20% times in 0. 25×0. 25 cm2 field. Also, Adjacent organs receive a lower dose, Because the dose profile curve was shrieked, it was almost 1cm in field 2×2 cm2 and less than 1cm in other fields. The dose profile flatness was diminished in scattering foil-free (SFF) mode which is not crucial for the small fields. Conclusion: Removing scattering foil improves dosimetric properties of electron beams specially to treat the superficial tumors and for the small field radiotherapy.

We obtained the local foil properties of the imaging bolometer foil such as the thermal diffusivity, k, and the product of the thermal conductivity, k, and the thickness, t¦, by calibrating some parts of the foil. The parameters are determined by finite element modeling (FEM) of the foil temperature and comparing the solution to the experimental results.Calibration of the foil was made in situ using a He-Ne laser as a known radiation source to heat the foil. The thermal images of the foil are provided by an infrared (IR) camera. In this work we apply this calibration technique to investigate the variation of the foil parameters. Variation in the local temperature rise of the foil due to local heating by the laser beam indicates a variation of the foil parameters k, k and t¦.

In this study, numerical investigations on the energy extraction performance of a flapping foil device are carried out by using a modified foil shape. The new foil shape is designed by combining the thick leading edge of NACA0012 foil and the thin trailing edge of NACA0006 foil. The numerical simulations are based on the solution of the unsteady and incompressible Navier-Stokes equations that govern the fluid flow around the flapping foil. These equations are resolved in a two-dimensional domain with a dynamic mesh technique using the CFD software ANSYS Fluent 16. A User Define Function (UDF) controls the imposed sinusoidal heaving and pitching motions. First, for a validation study, numerical simulations are performed for a NACA0012 foil undergoing imposed heaving and pitching motions at a low Reynolds number. The obtained results are in good agreement with numerical and experimental data available in the literature. Thereafter, the computations are applied for the new foil shape. The influences of the connecting area location between the leading and trailing segments, the Strouhal number and the effective angle of attack on the energy extraction performance are investigated at low Reynolds number (Re = 10 000). Then, the new foil shape performance was compared to those of both NACA0006 and NACA0012 baseline foils. The results have shown that the proposed foil shape achieves higher performance compared to the baseline NACA foils. Moreover, the energy extraction efficiency was improved by 30. 60% compared to NACA0006 and by 17. 32% compared to NACA0012. The analysis of the flow field around the flapping foils indicates a change of the vortex structure and the pressure distribution near the trailing edge of the combined foil compared to the baseline foils.