Determination of energy spectra of proton therapy beams

Bibliography: leaves 151-165.A technique has been developed for measuring the energy spectra of high-energy proton therapy beams in situ under conditions similar to those used for radiotherapy at the South African National Accelerator Centre. The method is based on proton elastic scattering, H(p,p)H, in a thin polyethylene radiator and uses two ΔE-E detector telescopes to detect coincident proton pairs. Measurements have been made to investigate the effect of standard beam modification elements on the energy spectra of proton therapy beams produced by a passive scattering system. Monte Carlo simulations of the spectra were computed with the MCNPX 2.1.5 Monte Carlo code to compare with experimental measurements

Gamma ray production cross sections in proton induced reactions on natural Mg, Si and Fe targets over the proton energy range 30 up to 66 MeV

Gamma-ray excitation functions have been measured for 30, 42, 54 and 66 MeV proton beams accelerated onto C + O (Mylar), Mg, Si, and Fe targets of astrophysical interest at the separate-sector cyclotron of iThemba LABS in Somerset West (Cape Town, South Africa). A large solid angle, high energy resolution detection system of the Eurogam type was used to record Gamma-ray energy spectra. Derived preliminary results of Gamma-ray line production cross sections for the Mg, Si and Fe target nuclei are reported and discussed. The current cross section data for known, intense Gamma-ray lines from these nuclei consistently extend to higher proton energies previous experimental data measured up to Ep ~ 25 MeV at the Orsay and Washington tandem accelerators. Data for new Gamma-ray lines observed for the first time in this work are also reported.Comment: 11 pages, 6 figures. IOP Institute of Physics Conference Nuclear Physics in Astrophysics VII, 28th EPF Nuclear Physics Divisional Conference, May 18-22 2015, York, U

Alpha emission from the interactions of 14-200 MeV neutrons on carbon-12

Summary in English.Bibliography: pages 89-93.Cross-sections for the production of alpha particles from the ¹²C(n,α)⁹Begs and ¹²C(n,n')3α reactions were measured for incident neutrons in the energy range 25 to 52 MeV. The measurements were reduced to absolute cross-sections by simultaneously observing deuteron recoils from n-d elastic scattering in the scintillator using D(n,n)D elastic scattering cross-section as a reference standard. Neutron energy was determined by time-of-flight and pulse shape discrimination (PSD) was used to identify and separate alphas and deuterons from other reaction products. The feasibility of distinguishing different mechanisms for the ¹²C(n,n')3α reaction by means of PSD was also investigated

Search for two-phonon octupole excitations in

The low-spin structure of the nearly spherical nucleus 146Gd was studied using the 144Sm(4He, 2n) fusion-evaporation reaction. High-statistics $\gamma - \gamma$ coincidence measurements were performed at iThemba LABS with 7× 109 $\gamma$-$\gamma$ coincidence events recorded. Gated $\gamma$-ray energy spectra show evidence for the $6^{+}_{2} \rightarrow 3^{-}_{1} \rightarrow 0^{+}_{1}$ cascade of E3 transitions in agreement with recent findings by Caballero and co-workers, but with a smaller branching ratio of $I_{\gamma} = 4.7(10)$ for the $6^{+}_{2} \rightarrow 3^{-}_{1}$ 1905.1 keV $\gamma$ ray. Although these findings may support octupole vibrations in spherical nuclei, sophisticated beyond mean-field calculations including angular-momentum projection are required to interpret in an appropriate way the available data due to the failure of the rotational model assumptions in this nucleus

Nature of low-lying electric dipole resonance excitations in Ge 74

Isospin properties of dipole excitations in Ge-74 are investigated using the (alpha,alpha'gamma) reaction and compared to (gamma,gamma') data. The results indicate that the dipole excitations in the energy region of 6 to 9MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy, being populated by both isoscalar and isovector probes, and the other at high energy, excited only by the electromagnetic probe. Relativistic quasiparticle time blocking approximation (RQTBA) calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy, which is consistent with the measurement

Nature of low-lying electric dipole resonance excitations in Ge 74

Isospin properties of dipole excitations in 74 Ge are investigated using the (α , α ′ γ ) reaction and compared to (γ , γ ′ ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy, being populated by both isoscalar and isovector probes, and the other at high energy, excited only by the electromagnetic probe. Relativistic quasiparticle time blocking approximation (RQTBA) calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy, which is consistent with the measurement