Interaction Cross Sections Research Articles

Comparison of proton interaction physics models and cross section libraries for proton therapy Monte Carlo simulations by MCNP6.2 code

Proton cross-section libraries and interaction models available in the Monte Carlo code MCNP6.2 were tested and compared for energies relevant to proton radiation therapy (100, 150, 226 MeV), and for three different phantom materials. Proton, neutron, and photon characteristics were studied. Primary proton parameters included proton total deposited energy and Bragg peak position. The results varied within ±0.5%. Secondary neutron characteristics included the number of originated secondary neutrons, their average initial energy, energy spectrum, depth-dose curve, radiation weighting factor, neutron equivalent dose inside phantoms, and neutron spectral fluence and ambient dose equivalent outside phantoms. Neutron radiation weighting factor inside a phantom varied within ±8% and neutron equivalent dose typically within ±30%. Large differences were observed in neutron fluence energy spectra both inside and outside a phantom. Secondary photon characteristics consisted of photon equivalent dose inside phantoms. The study demonstrates that the selection of input proton data may have a large impact on the simulated quantity, especially if the intention is to model secondary particles, particularly neutrons.

A new study on (n, p) cross sections in nuclear interactions of neutrons with dysprosium

Neutron-induced nuclear reaction cross section data on dysprosium (Dy) target material are needed for the development and design of reactors, because of using Dy such as an absorbing material for the control rods in reactors. Furthermore, these data are important in terms of improving the definition of neutron–particle interaction. In this framework, the excitation functions of 156,158,160–164Dy(n, p)156,158,160–164Tb reactions were theoretically calculated using TALYS 1.8 and EMPIRE 3.2 Malta nuclear reaction codes. In addition, effects of different level density models on the reaction cross sections were also investigated. Therefore, the obtained theoretical cross sections are compared with the experimental cross sections found in the literature. Besides, (n, p) cross section systematics, which was proposed in our previous article and in the literature, has been used for obtaining the reaction cross sections at energies of around 14 MeV.

Dibaryons cannot be the dark matter

The hypothetical $SU(3)$ flavor-singlet dibaryon state $S$ with strangeness $\ensuremath{-}2$ has been discussed as a dark-matter candidate capable of explaining the curious 5-to-1 ratio of the mass density of dark matter to that of baryons. We study the early-universe production of dibaryons and find that irrespective of the hadron abundances produced by the QCD quark/hadron transition, rapid particle reactions thermalized the $S$ abundance, and it tracked equilibrium until it ``froze out'' at a tiny value. For the plausible range of dibaryon masses (1860--1890 MeV) and generous assumptions about its interaction cross sections, $S$'s account for at most ${10}^{\ensuremath{-}11}$ of the baryon number and, thus, cannot be the dark matter. Although it is not the dark matter, if the $S$ exists, it might be an interesting relic.

Complete Glauber calculations for proton–nucleus inelastic cross sections

We perform a parameter-free calculation for the high-energy proton–nucleus scattering based on the Glauber theory. A complete evaluation of the so-called Glauber amplitude is made by using the factorization of the single-particle wave functions. The multiple-scattering or multistep processes are fully taken into account within the Glauber theory. We demonstrate that proton-12C, 20Ne, and 28Si elastic and inelastic scattering (Jπ=0+→2+ and 0+→4+) processes are very well described in a wide range of the incident energies from ∼50 MeV to ∼1 GeV. We evaluate the validity of a simple one-step approximation and find that the approximation works fairly well for the inelastic 0+→2+ processes but not for 0+→4+ where the multistep processes become more important. As an application, we quantify the difference between the total reaction and interaction cross sections of proton-12C, 20Ne, and 28Si collisions.

Calculation of reactions cross section for proton-induced nuclear reactions on Iodine-127 isotope

Radioisotope production for nuclear medicine is tomography devices. Both single photon emissions computed tomography (SPECT) and positron emission tomography (PET) is used for diagnosis in nuclear medicine we have calculated the reaction cross section and investigated the excitation functions for the formation of 127,126 125 I , 126,127,128 Xe , 126,125 Te isotopes in the interactions of proton particle with the nucleus of the iodine-127 isotope. The analysis shows that there is a variation of interaction cross-section with a variation of energy of the incident particle. The result shows that the plots of the 127 I (p,ng), and 127 I (p,2ng), graphs have full excitation curve. The productions confirm the presence of Xenon-127 and Xenon-126 isotopes are possible at the energy range of 0 to 30 MeV from the iodine-127 nucleus. Keywords : Cross-Section; Excitation function; Nuclear Reaction; Radioisotope; Statistical Multistep Reaction

A deformed Doppler Broadening Function considering the Tsallis speed distribution

The Doppler Broadening Phenomenon provides a good description for the effects of thermal agitation on the cross-section of the neutron-nucleus interaction and has its theoretical basis on Quantum Mechanics through the Single Level Breit-Wigner Formalism, as well as on Statistical Mechanics, with the Maxwell Boltzmann distribution. In this paper, the consequences of replacing the Maxwell Boltzmann speed distribution by the non-extensive Tsallis distribution in the evaluation of the absorption cross section in three-dimension is discussed. The Tsallis speed distribution introduces a deformation parameter q that measures the deviation from the Maxwellian speed distribution and, by taking the limit q→1, the deformation is removed. In this context, and considering the Tsallis distribution, an integral form is obtained for a deformed Doppler Broadening Function in the scope of the single-level Breit-Wigner formalism and Bethe-Placzek approximations. This deformed Doppler Broadening Function reproduces the well-established conventional Doppler Broadening Function at the limit when q→1 in which the deformation is removed. In order to study the range of values where the effect is significant, numerical tests were carried out considering several values for the q parameter.

The photon interaction cross sections of blood

The photon interaction cross sections which contain the photoelectric absorption, coherent (Rayleigh) and incoherent (Compton) scattering are calculated for blood in the energy range of 1–150 keV. The molecular photoelectric absorption cross section is achieved from atomic cross section data. The molecular coherent (Rayleigh) and incoherent (Compton) scattering cross sections are estimated using relativistic modified form factor and incoherent scattering function approximation, respectively. The molecular form factors updated including molecular interference effects and incoherent scattering functions were also calculated. With the inclusion of the molecular interference effects in the coherent (Rayleigh) scattering, the more accurate data of radiation scattered from blood will be provided. The results are compared with references values in literature. It is found that the theoretical attenuation coefficients are in good agreement with experimental values.

Measurement of the real dielectric permittivity ϵr of glacial ice

Owing to their small interaction cross-section, neutrinos are unparalleled astronomical tracers. Ultra-high energy (UHE; E > 10 PeV) neutrinos probe the most distant, most explosive sources in the Universe, often obscured to optical telescopes. Radio-frequency (RF) detection of Askaryan radiation in cold polar ice is currently regarded as the best experimental measurement technique for UHE neutrinos, provided the RF properties of the ice target can be well-understood. To that end, the Askaryan Radio Array (ARA) experiment at the South Pole has used long-baseline RF propagation to extract information on the index-of-refraction (n=ϵr) in South Polar ice. Owing to the increasing ice density over the upper 150–200 m, rays are measured along two, nearly parallel paths, one of which refracts through an inflection point, with differences in both arrival time and arrival angle that can be used to constrain the neutrino properties. We also observe (first) indications for RF ice birefringence for signals propagating along predominantly horizontal trajectories, corresponding to an asymmetry of order 0.1% between the ordinary and extra-ordinary birefringent axes, numerically compatible with previous measurements of birefringent asymmetries for vertically-propagating radio-frequency signals at South Pole. Qualitatively, these effects offer the possibility of redundantly measuring the range from receiver to a neutrino interaction in Antarctic ice, if receiver antennas are deployed at shallow (z ∼ −25 m) depths. Such range information is essential in determining both the neutrino energy, as well as the incident neutrino direction.

New version of library of dose kernels of photons pencil beam and their analytical approximation

A new version of dose kernels library of photon pencil beams for water has been created to calculate a more perfect description and modelling of the physical processes of photons and charged particles' interaction with matter, with more adequate data on the interaction cross sections and significantly lower values of the statistical uncertainties of the results. The library includes data for monoenergetic photons in the energy range of 0.25-19.75 MeV, data for bremsstrahlung photons with a maximum energy of 4.0 MeV, 6.0 MeV, 10.0 MeV, 15.0 MeV, 18.0 MeV, and data for the spectrum of the ROKUS therapeutic apparatus. Dose kernels were calculated using the Monte-Carlo method by the EGSnrc code. Depths in water from 1.0 to 40 cm and along the radius from 0.02 to 46.0 cm were studied. A convenient mathematical approximation model of dose kernel of a pencil beam is proposed.

New version of library of dose kernels of photons pencil beam and their analytical approximation

A new version of dose kernels library of photon pencil beams for water has been created to calculate a more perfect description and modelling of the physical processes of photons and charged particles' interaction with matter, with more adequate data on the interaction cross sections and significantly lower values of the statistical uncertainties of the results. The library includes data for monoenergetic photons in the energy range of 0.25-19.75 MeV, data for bremsstrahlung photons with a maximum energy of 4.0 MeV, 6.0 MeV, 10.0 MeV, 15.0 MeV, 18.0 MeV, and data for the spectrum of the ROKUS therapeutic apparatus. Dose kernels were calculated using the Monte-Carlo method by the EGSnrc code. Depths in water from 1.0 to 40 cm and along the radius from 0.02 to 46.0 cm were studied. A convenient mathematical approximation model of dose kernel of a pencil beam is proposed.

EAS longitudinal development distribution parameters for different extrapolations of the nuclei intaraction cross section to the very high energy domain

Determination of the primary particle mass using air fluorescence or a Cherenkov detector array is one of the most difficult task of experimental cosmic ray studies. The information about the primary particle mass is a compound of the produced particle multiplicity, inelasticity, interaction cross-section and many other parameters, thus it is necessary to compare registered showers with sophisticated Monte-Carlo simulation results. In this work we present results of the studies of at least three possible ways of extrapolating proton- Nucleus and Nucleus-Nucleus cross sections to cosmic ray energies based on the Glauber theory. They are compared with experimental accelerator and cosmic ray data for the proton-air cross section. We also present results of the EAS development with the most popular high-energy interaction models adopted in the CORSIKA program with our cross section extrapolations. The average position of the shower maximum and the width of its distribution are compared with experimental data and some discussion is given.

GeV-scale messengers of Planck-scale dark matter

If dark matter (DM) originates from physics near the Planck scale it could be directly detected via its multiple scattering signals, yet this requires a large cross section for DM interactions with atoms. Hence, detection of such DM could imply mediation by new low mass messengers. We propose that a dark $U(1)_d$ remnant of the underlying spacetime geometry or a unified theory may survive down to small mass scales $\sim 1$ GeV, connecting low energy Standard Model (SM) and Planck scale phenomena. Typical required cross sections for direct detection of Planck scale DM can be achieved through the $U(1)_d$ interactions of DM with SM quarks. Low energy intense sources may uncover the GeV scale messengers of Planckian physics, allowing for testable predictions. We assume that $U(1)_d$ is gauged baryon number, which implies several new electroweak charged particles are expected to arise near the weak scale to cancel gauge anomalies. The model generically gives rise to kinetic mixing between the $U(1)_d$ gauge boson and the photon, which may be measurable. In this scenario, direct detection of DM and measurements of a low energy messenger, including its kinetic mixing with the photon, can potentially shed light on the high energy character of the scenario. Astrophysical considerations related to white dwarf stability against runaway nuclear fusion potentially disfavor DM heavier than $\sim 10^{17}$ GeV within our assumed messenger model.

Disentangling dark physics with cosmic microwave background experiments

We forecast constraints on dark matter (DM) scattering with baryons in the early Universe with upcoming and future cosmic microwave background (CMB) experiments, for DM particle masses down to 15 keV. In terms of the upper limit on the interaction cross section for a velocity-independent spin-independent elastic scattering, compared to current Planck results, we find a factor of $\sim$6 improvement with CMB-Stage 3, a factor of $\sim$26 with CMB-Stage 4, and a factor of $\sim$200 with a cosmic-variance limited experiment. Once the instrumental noise reaches the proximity of 1 $\mu$K-arcmin, the constraints are entirely driven by the lensing measurements. The constraints benefit from a wide survey, and show gradual improvement for instrumental noise levels from 10 $\mu$K-arcmin to 1 $\mu$K-arcmin and resolution from 5 arcmin to 1 arcmin. We further study degeneracies between DM interactions and various other signatures of new physics targeted by the CMB experiments. In the primary temperature and polarization only, we find moderate degeneracy between the effects of DM scattering, signals from massive neutrinos, and from the effective number of relativistic degrees of freedom. The degeneracy is almost entirely broken once the lensing convergence spectrum is included into the analyses. We discuss the implications of our findings in context of planned and upcoming CMB measurements and other cosmological probes of dark-sector and neutrino physics.

Study of spectral and recombination characteristics of HVPE GaN grown on ammono substrates

A comprehensive study of the bulk ~400 µm thick GaN samples, grown by HVPE technology on AT-GaN seeds, and containing different carbon doping is reported. Spectroscopy of point centres has been implemented by combining several contactless/optical techniques: time resolved photoluminescence (TR-PL), microwave probed photoconductivity (MW-PC) transient and pulsed-photo-ionization spectroscopy (PPIS) techniques, together with steady-state PL (SS-PL) and transmission spectral measurements. The dynamics of the non-radiative and radiative recombination dependent on the excess carrier density and incorporated carbon concentration has been revealed. The cross-section of the photon-electron interaction and broadening factors due to electron-phonon coupling have been evaluated for various centres. Profiling of the excess carrier decay transients by scanning a wafer-edge boundary has been employed for estimation of surface recombination velocity. The asymmetry of surface recombination in heavily carbon doped samples has been corroborated by SS-PL intensity changes when comparing spectra recorded by exciting the opposite wafer surfaces using UV light. It has been inferred that the surface and bulk non-radiative recombination with 70 ns carrier lifetime is efficient only within initial stages of MW-PC and TR-PL transients. Several traps, tentatively attributed to CNON, CN, CI, VGa point defects, have been deduced from pulsed photo-ionization spectroscopy. The CN- defect appeared to be the most efficient in redistribution of the radiative recombination. For these centres, the parameters such as the photon-electron interaction cross-section, broadening factor due to electron-phonon coupling, and concentration have been evaluated for GaN samples, carbon doped with different levels. The CNVGa, CICGa, CGaVN complexes have also been implied by considering TR-PL and SS-PL spectra. The conversion from absorption to emission spectra has been revealed and explained based on van Roosbroeck-Shockley approach. The long-tail photoluminescence decay with durations up to tens of ms has been explained by nearly resonant photo-ionization and photoluminescence transitions in sequence of self-sustaining processes when local excitation travels by hopping over the re-absorption lengths.

Quantum-Mechanical Theory of Elastic Scattering and Cross Section Determination of Particle Interactions in Plasma

A quantum-mechanical description of the theory of elastic scattering and a technique for determining the cross sections of particle interactions in plasma are described. An asymptotic solution of the Schrodinger equation for the elastic interaction of plasma particles is presented. Algorithms for determining phase shifts based on the Modified Effective Range Theory (MERT) are given. The Born approximation is considered to determine the amplitude of the scattered waves and the scattering cross section of the particles. Data are presented on the cross sections for scattering of electrons by atoms and ions in argon.

Impact of Powerful Thermal and Neutron Fluxes on the Structural Elements of Fusion and Fission Reactors

Methods for calculating the heat and neutron transport in structural elements of nuclear and fusion power devices are considered in the framework of statistical modeling and physical neutron kinetics based on the cross sections of interaction of neutrons with matter. Statistical modeling makes it possible to establish the nature of the neutron transport and energy in matter. In the extreme cases, within the framework of this approach, the diffusion and ballistic regimes are realized. In the calculation of heat transfer, the heat release associated with gamma quanta is also taken into account. The possibilities of these methods for estimation of the joint thermal effects of these factors are shown.

DPM as a radiation transport engine for PRIMO

BackgroundPRIMO is a dose verification system based on the general-purpose Monte Carlo radiation transport code penelope, which implements an accurate physics model of the interaction cross sections and the radiation transport process but with low computational efficiency as compared with fast Monte Carlo codes. One of these fast Monte Carlo codes is the Dose Planning Method (DPM). The purpose of this work is to describe the adaptation of DPM as an alternative PRIMO computation engine, to validate its performance against penelope and to validate it for some specific cases.MethodsDPM was parallelized and modified to perform radiation transport in quadric geometries, which are used to describe linacs, thus allowing the simulation of dynamic treatments. To benchmark the new code versus penelope, both in terms of accuracy of results and simulation time, several tests were performed, namely, irradiation of a multi-layer phantom, irradiation of a water phantom using a collimating pattern defined by the multileaf collimator (MLC), and four clinical cases. The gamma index, with passing criteria of 1 mm/1%, was used to compare the absorbed dose distributions. Clinical cases were compared using a 3-D gamma analysis.ResultsThe percentage of voxels passing the gamma criteria always exceeded 99% for the phantom cases, with the exception of the transport through air, for which dose differences between DPM and penelope were as large as 24%. The corresponding percentage for the clinical cases was larger than 99%. The speedup factor between DPM and penelope ranged from 2.5 ×, for the simulation of the radiation transport through a MLC and the subsequent dose estimation in a water phantom, up to 11.8 × for a lung treatment. A further increase of the computational speed, up to 25 ×, can be obtained in the clinical cases when a voxel size of (2.5 mm)3 is used.ConclusionsDPM has been incorporated as an efficient and accurate Monte Carlo engine for dose estimation in PRIMO. It allows the concatenated simulation of the patient-dependent part of the linac and the patient geometry in static and dynamic treatments. The discrepancy observed between DPM and penelope, which is due to an artifact of the cross section interpolation algorithm for low energy electrons in air, does not affect the results in other materials.

Collider Searches for Dark Matter (ATLAS + CMS)

Several searches for dark matter have been performed by the CMS and ATLAS collaborations, using proton-proton collisions with a center-of-mass energy of 13 TeV produced by the Large Hadron Collider. Different signatures may highlight the presence of dark matter: the imbalance in the transverse momentum in an event due to the presence of undetectable dark matter particles, produced together with one Standard Model particle, a bump in the di-jet or di-lepton invariant mass distributions, or an excess of events in the di-jet angular distribution, produced by a dark matter mediator. No significant discrepancies with respect to the Standard Model predictions have been found in data, so that limits on the dark matter couplings to ordinary matter, or limits on the dark matter particles and mediators masses have been set. The results are also re-interpreted as limits on the dark matter interaction cross-section with baryonic matter, so that a comparison with direct detection experiments is allowed.

An Approximation of Cross Sections of Channels of the 9Be(α, n) Reaction on the Basis of the Gamow Interaction Radius

Radiation transport of α-particles requires cross sections of inelastic interaction of α-particles with nuclei. At low energies the inelastic interactions are limited to the 9Be(α, n) reaction, whose channel cross sections are assessed only in the specialized evaluated nuclear data library JENDL/AN-2005. The new TPT (Toolkit for Particle Transport) approximation of the 9Be(α, n) reaction cross sections for different channels takes into account the lowest resonance and, at high energies, relies on the exponential decrease in the S-factor, which is a consequence of the theory of direct nuclear reactions.

Dark Matter that Interacts with Baryons: Density Distribution within the Earth and New Constraints on the Interaction Cross-section

Abstract For dark matter (DM) particles with masses in the 0.6–6m p range, we set stringent constraints on the interaction cross-sections for scattering with ordinary baryonic matter. These constraints follow from the recognition that such particles can be captured by—and thermalized within—the Earth, leading to a substantial accumulation and concentration of DM that interact with baryons. Here, we discuss the probability that DM intercepted by the Earth will be captured, the number of DM particles thereby accumulated over Earth’s lifetime, the fraction of such particles retained in the face of evaporation, and the density distribution of such particles within the Earth. In the latter context, we note that a previous treatment of the density distribution of DM, presented by Gould and Raffelt and applied subsequently to DM in the Sun, is inconsistent with considerations of hydrostatic equilibrium. Our analysis provides an estimate of the DM particle density at Earth’s surface, which may exceed 1014 cm−3, and leads to constraints on various scattering cross-sections, which are placed by (1) the lifetime of the relativistic proton beam at the Large Hadron Collider; (2) the orbital decay of spacecraft in low Earth orbit; (3) the vaporization rate of cryogenic liquids in well-insulated storage dewars; and (4) the thermal conductivity of Earth’s crust. For the scattering cross-sections that were invoked recently in Barkana’s original explanation for the anomalously deep 21 cm absorption reported by EDGES, DM particle masses in the 0.6–4m p range are excluded.