Stopping powers and backscattered charge fractions for 20–150 keV H+ and He+ on gold

The stopping powers for 20–150 keV H⁺ and He⁺ in Au have been measured by the backscattering technique. Thin Au layers (∼ 10 nm) on Be substrates were used. The Au thickness (NΔt) was determined using Rutherford backscattering with 1 MeV He and a well calibrated detector geometry. An electrostatic analyser was used to determine the energy loss of the keV ions in penetrating the Au layer. This energy loss measurement was corrected for the neutral component of the backscattered ions using the measured charged fraction and its energy dependence with a thin window solid state detector. The estimated accuracy of the results is <5% and they are compared to previous published data and interpolated best estimates.     

Stopping of ∼0.2–3.4 MeV/amu 1H+ and 4He+ ions in polyvinyl formal

The stopping powers of polyvinyl formal resin for protons and alpha particles have been measured over the energy range ～(0.2–3.4) MeV/amu with an overall relative uncertainty of less than 2.5% using the ion beam transmission method. The obtained results are discussed in comparison to scarce experimental data from the literature and to values calculated by the SRIM-2008 computer code assuming Bragg-Kleeman’s additivity rule of stopping powers. Departures from additivity attaining ～5.5% and ～3.0% for the proton and alpha particle data, respectively, are observed at moderate projectile velocities, increasingly as one evolves towards the stopping power maximum dominated by charge exchange effects. They are presumed to be mainly due to valence structure effects involving the C–H bonds of the studied polymer compound. The less pronounced deviation for alpha particles is probably due to the projectile screening effect that occurs in distant collisions tending to reduce the contribution of valence electrons in the low projectile velocity regime.     

Stopping force and straggling of 0.6–4.7 MeV H,He and Li ions in the polyhydroxybutyrate foil

Stopping force and straggling of 0.6–3.5 MeV ¹H ions, 2.0–4.7 MeV ⁴He ions and 1.4–4.4 MeV ⁷Li ions in the polyhydroxybutyrate (PHB) foil were measured by means of a transmission technique. The measured stopping forces are in well agreement with the SRIM 2008 calculation and the ICRU Report tables, except for the lower energy region. The obtained energy loss straggling deviates from the Bohr’s value by as much as 23.6% for the energies under study. The validity of the Bragg’s rule has also been demonstrated in the stopping force and straggling for ¹H, ⁴He and ⁷Li ions in the PHB foil.     

Non-invasive optical characterization and estimation of Zn porosity in gas tungsten arc welding of Fe–Al joints using CR model and OES measurements

In this study, we employed a non-invasive approach based on the collisional radiative(CR) model and optical emission spectroscopy(OES) measurements for the characterization of gas tungsten arc welding(GTAW) discharge and quantification of Zn-induced porosity during the GTAW process of Fe–Al joints. The OES measurements were recorded as a function of weld current, welding speed, and input waveform. The OES measurements revealed significant line emissions from Zn-I in 460–640 nm and Ar-I in 680–80...     

Self-Shielding Factors for Neutron Capture Reactions of Uranium-238 and Thorium-232 in Energy Range of 1–35 keV

Self-shielding factors for the neutron capture reactions of ²³⁸U and ²³²Th were measured in the resonance energy region of 1–35 keV, using a neutron time-of-flight method with an electron linear accelerator. The self-shielding factors for arbitrary dilution cross sections were obtained from sets of neutron transmission ratios and self-indication ratios measured with several transmission samples of different thicknesses. The maximum experimental errors for ²³⁸U and ²³²Th were about 3 and about 7%, respectively.

The experimental results were compared with calculations based on JENDL-2, JENDL-3 and ENDF/B-IV. For ²³⁸U, an energy dependent structure was observed in the experimental self- shielding factors. The calculations based on JENDL-2 and ENDF/B-IV did not show this structure in the unresolved resonance region and were smaller than the experimental values from 4 to 6 keV. The calculation based on the resolved resonance parameters in JENDL-3 showed better agreement with the experiment from 4 to 6 keV, but discrepancies still remained in other energy ranges.

For ²³²Th, no remarkable discrepancy was observed in the unresolved resonance region, but JENDL-2 and JENDL-3 tended to give smaller values than the experimental self-shielding factors in the resolved resonance region.     

Electron paramagnetic resonance study of proton implantation induced defects in monocrystalline 4H– and 6H–SiC

Ion implantation is frequently employed in SiC for doping, electrical isolation or in the SiC on isolator technology. The ion implantation process is accompanied by the formation of intrinsic defects, which introduce deep electron and hole traps. They are believed to be mainly multivacancy complexes but the exact microscopic nature of these defects and their distribution versus the ion penetration depth is not well established. We have analyzed by electron paramagnetic resonance spectroscopy the defects introduced by high energy (MeV) proton implantation. In this study we extend the previous investigations on n-type SiC to the case of p-type Al doped bulk samples. Both silicon monovacancy and carbon vacancy related defects are observed. Their nature and introduction rate have been determined. The results obtained will be compared to the published electrical studies in order to correlate the vacancy defects with the known electron and hole traps.     

Stopping power measurements of heavy ions (3 ? Z1 ? 14) in Mylar foil by time-of-flight spectrometry

Heavy ions elastic recoil detection analysis coupled with time of flight spectrometer (HIERDA_ToF-E) have been used to measure energy loss of charged particles in thin absorber. The stopping power of heavy ions has been determined in Mylar for ²⁸Si, ²⁷Al, ²⁴Mg, ¹⁹F, ¹⁶O, ¹²C and ⁷Li ions over a continuous range of energies 0.14-0.80 MeV/nucleon. The ions were recoils from the bombardment of different samples (Si, MgO, Al₂O₃, LiF and C) with a 27.5 MeV Kr⁺ beam. The energy loss of the recoil atoms is measured with and without additional foils placed in front of a Surface Barrier Detector (SBD). The energy of individual ions is determined from its ToF data; the exit energy after the stopping foil is measured using the SBD detector. We have compared our stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables, MSTAR calculations and to the published data from literature. The results show good agreement with limited existing data but indicate a large deviation among the predicted theoretical values at the low energy side of the stopping maximum peak.     

Calculation and Analysis of Neutron Induced Reactions on ~(175, 176)Lu and ~(Nat)Lu in Energy Region 1 keV～20 MeV

A set of neutron optical potential parameters for 1 kev≤E_n≤20 MeV is obtained on the basis of the relevant experimental data, and all cross sections of neutron induced reaction on ~(175,175,Nat)Lu are calculated. The calculated results are compared with experimental data.     

Measurements of activation cross sections of (n,p) and (n, α) reactions in the energy range of 3.5–5.9 MeV using a deuterium gas target

Activation cross sections of (n, p) and (n, α) reactions were measured by means of the activation method in the neutron energy range of 3.5–5.9 MeV using a deuterium gas target. The irradiated target isotopes were ²⁷Al, ^28,29Si, ⁴¹K, ⁵¹V, ⁶¹Ni, ⁶⁵Cu, ^64,67Zn, ⁶⁹Ga, ⁷⁹Br, ⁹²Mo and ⁹³Nb. The cross sections of the ²⁹Si(n, p) ²⁹Al, ⁶⁷Zn(n, p) ⁶⁷Cu, ⁶⁹Ga(n, p) ^69mZn, ⁷⁹Br(n, p) ^79mSe, and ⁶⁹Ga(n, α) ⁶⁶Cu reactions were obtained for the first time in the studied energy range. The d-D neutrons were generated by the deuterium gas target at the Van de Graaff accelerator (KN-VdG) at Nagoya University. All cross section values were determined relative to those of the ¹¹⁵In(n, n′)^115mIn reaction. The activities induced by the low-energy neutrons were corrected. For the corrections, the neutron spectra and mean neutron energies at the irradiation positions were calculated taking into account the energy loss of incident deuterons, the angular differential cross section of the d-D reaction and the solid angle subtended by the sample. The systematics of the (n, p) reactions at the neutron energy of 5.0 MeV in the mass range between 27 and 92 were proposed for the first time. This systematics can predict the cross sections within an accuracy of a factor of 1.6.