Measurement of stopping power of UO2 for alpha particles.

Continuous energy spectra of protons and alpha particles have been studied in the deuteron-alpha particle scattering at the incident deuteron energy of 14.2 MeV. In the energy spectra of protons, the evidence for a final state resonance in the neutron and alpha particle system have been obtained and the energy spectrum is compared with the theory of final state interaction. There is a good agreement between the experiment and the theory. The angular dependence of the cross sections at peaks shows a stripping-like feature. The energy spectrum of the alpha particles at the higher energy is mainly affected by the effect of the final state interaction of the triplet S state in the neutron and proton system. The angular dependence of these alpha particles shows a forward peak in the laboratory system and it may be explained by an exchange process.

Depth distribution of boron determined by slow neutron induced lithium ion emission

Absorbed dose delivered by alpha particles calculated in cylindrical geometry

Values of modified Bethe–Bloch stopping power parameters for polysulfone extracted from stopping power measurements with light projectiles

An overview of current stopping power phenomena, measurements, and related topics

Objective.This study aims to comprehensively compare the PENHAN and FLUKA Monte Carlo codes for low-energy alpha particle transport and small-scale dosimetry using alpha-emitting radionuclides, and to assess their suitability for such applications.Approach.Two studies were performed through Monte Carlo simulations. First, monoenergetic alpha particles (3-10 MeV) were distributed in a micrometric water sphere and the dose deposition within it was calculated. Second, a simplified spherical cell model with uniformly distributed alpha-emitting radionuclides was used to computeS-values. PENHAN and FLUKA results were compared, and potential sources of discrepancy between them were analyzed. In addition, both codes were benchmarked against MIRDcell, an analytical tool widely used for dosimetric calculations in Targeted radionuclide therapy.Main results.In the monoenergetic study, the primary source of discrepancy between PENHAN and FLUKA was the stopping powers used for alpha particles. When the same stopping powers were employed, both codes yielded statistically compatible results, except at 3.0 and 3.5 MeV, where FLUKA showed an anomalous behavior. In the cell model, variations were below 3% but not negligible even when using identical stopping powers, suggesting an additional source of discrepancy: differences in the radionuclide emission spectra, particularly in the electron component. In both studies, PENHAN and FLUKA results were overall in good agreement with those from MIRDcell.Significance.This study demonstrates, for the first time, the suitability of PENHAN for low-energy alpha transport and small-scale dosimetry with alpha emitters, provided that accurate stopping powers are employed. It also supports the reliability of FLUKA in these scenarios and shows that both codes yield compatible results when using consistent stopping power datasets and radionuclide emission spectra. This work further highlights the importance of validating Monte Carlo codes in medical physics to ensure the reliability and reproducibility of their results.

The aim of the NUCLEON space experiment was to measure spectra of high-energy cosmic rays. Direct measurements of energy spectra of protons and nuclei of cosmic rays which allow separating particles in charge are required to solve important astrophysical problems. The satellite was launched on December 26, 2014, and operated for three years. Measured spectra of protons and alpha particles in the energy range of 2–500 TeV per particle have been presented. The results have been analyzed and compared to other experimental data for lower energies. The ratio of fluxes of protons and alpha particles is nearly constant in a wide range of magnetic rigidities (3–100 TV). Thus, the behavior of the ratio of the spectra is significantly different from a similar dependence in the region of lower magnetic rigidities measured in other experiments. One of the possible explanation of this effect can be given within a model with one close source.

Stopping power and energy loss straggling of thin Formvar foil for 0.3–2.7 MeV protons and alpha particles

Bethe-bloch stopping power parameters for light projectiles at energies near the stopping power maximum

The classical and quantum theories leading to the asymptotic Bethe formula of the stopping power of matter for charged particles heavier than the electron are briefly reviewed. Models and approximations for the practical calculation of various corrections that extend the validity range of the formula are described. The asymptotic formula and the associated shell correction were determined previously from an extensive database of atomic generalized oscillator strengths, calculated for an independent-electron model with the Dirac-Hartree-Fock-Slater (DHFS) self-consistent potential, with due account for relativistic departures from the Bethe sum rule. The nonrelativistic Bloch correction is extended to the relativistic domain by means of the Lindhard-Sørensen formulation, and an accurate parametrization for point projectiles with small charges is proposed. The density-effect correction and the Barkas correction are obtained from a semiempirical model of the optical oscillator strength (OOS), built from the calculated DHFS contributions of inner electron subshells plus the OOS of outer-shell electrons represented by an analytical expression, which is determined by the composition, mass density, and empirical mean excitation energy, or I value of the material. Inclusion of the shell, density-effect, Lindhard-Sørensen, and Barkas corrections into the asymptotic formula leads to the corrected Bethe formula. A general strategy is proposed to determine the stopping power in terms of only the I value of the material. It is shown that, with the empirical I values recommended in Report 37 of the International Commission on Radiation Units and Measurements, the stopping powers calculated numerically from the corrected formula are in close agreement with available measurements of the stopping power of elemental materials for protons and alpha particles with energies higher than 0.75 and 5 MeV, respectively.

Stopping power for alpha particles in organic liquids and vapours

GaN epitaxial layers are usually grown on sapphire substrates.To avoid disastrous effect of the large lattice mismatch a thin polycrystalline nucleation layer is grown at 500 • C followed by the deposition of thick GaN template at much higher temperature.Remnants of the nucleation layer were visualized by transmission electron microscopy as defect agglomeration at the GaN/sapphire interface and provide a very useful depth marker for the measurement of channeled ions stopping power.Random and aligned spectra of He ions incident at energies ranging from 1.7 to 3.7 MeV have been measured and evaluated using the Monte Carlo simulation code McChasy.Impact parameter dependent stopping power has been calculated for channeling direction and its parameters have been adjusted according to experimental data.For virgin, i.e. as grown, samples, the ratio of channeled to random stopping power is constant and amounts to 0.7 in the energy range studied.Defects produced by ion implantation largely influence the stopping power.For channeled ions the variety of possible trajectories leads to different energy loss at a given depth, thus resulting in much larger energy straggling than that for the random path.Beam energy distributions at different depths have been calculated using the McChasy code.They are significantly broader than those predicted by the Bohr formula for random direction.

The accuracy of ion beam analysis experiments depends critically on the stopping power values available. While for H and He ions accuracies normally better than 5% are achieved by usual interpolative schemes such as SRIM, for heavier ions the accuracy is worse. One of the main reasons is that the experimental data bases are very sparse, even for important materials such as Si. New measurements are therefore needed. Measurement of stopping power is often made with transmission in thin films, with the usual problems of film thickness homogeneity. We have previously developed an alternative method based on measuring bulk spectra, and fitting the yield by treating the stopping power as a fit parameter in a Bayesian inference Markov chain Monte Carlo procedure included in the standard IBA code NDF. We report on improvements of the method and on its application to the determination of the stopping power of 7Li in Si. To validate the method, we also apply it to the stopping of 4He in Si, which is known with 2% accuracy.

Specific luminescence studies of alpha particles in NE-102 scintillator film

The spectra of both protons and alpha particles (1 ≲ E ≲ 7 MeV/nucleon) during 31 recurrent particle streams are fit well by an exponential in particle rigidity. Although the spectra show considerable temporal variation, the proton and alpha particle spectra are correlated such that the e‐folding rigidities Po(α) and Po(p) of the two spectra are in the ratio Po(α)/Po(p) = 1.5 ± 0.1. The consistency of this ratio may be a characteristic of the interplanetary acceleration process.