Angular Distribution Of Secondary Particles Research Articles

New developments in the MCUNED-Plus code for radiation transport and coupled transport-activation computational simulations in accelerator-based facilities

The radiation hazard is one of the major aspects of concern in the design of a facility where it exists a risk of exposure to ionizing radiation. The nuclear analysis for radioprotection purposes requires an accurate description of the radiation fields. This is especially true in accelerator-based facilities where several types of particles are producing the radiation fields. Radiation fields exist during the accelerator operation, but delayed radiation may also be significant for a long time after operation ends. The radiation fields of concern present during the operation are due to the secondary neutrons and photons emitted by the interaction of accelerated particles with the accelerator components (beam leakage) or with the target. The radiation present after the operation is the residual photon field produced by activated materials, these materials being activated by both accelerated particles and secondary neutrons. This residual radiation field is relevant in high intensity accelerators like IFMIF-DONES.In order to address these complex radiation transport simulations, the D1SUNED code has been updated and the new code release renamed as MCUNED-Plus. The new developments include improvements in the light-ion transport like the implementation of a variance reduction for the production of secondary particles, and a new kinematics to reproduce the angular distribution of secondary particles emitted after deuteron breakup reaction. The calculation of the residual photon field in accelerator facility has also been improved by allowing to evaluate both light-ions and secondary neutrons induced shutdown dose rate in a single coupled simulation.

Radiation Environment at the Surface and Subsurface of the Moon: Model Development and Validation

AbstractA comprehensive understanding of the lunar radiation environment is essential in preparing for future human exploration of the Moon. The radiation environment on the Moon includes primary space radiation and secondary radiation, which is induced in the lunar soil. Both primary and secondary radiation may pose severe health issues to future crews on the Moon. In this work, we build a detailed radiation environment model “Radiation Environment and Dose at the Moon (REDMoon)” for the lunar surface and subsurface. We use the GEANT4 (GEometry ANd Tracking) Monte‐Carlo code and “response function” approach to calculate type‐, energy‐, angular‐, depth‐, and time‐dependent particle spectra induced by galactic cosmic rays at the surface and subsurface of the Moon. Calculated radiation particle fluxes on and beneath the surface are in good agreement with previous experimental and numerical results while offering more details on the lunar radiation fields, such as angular and depth information. The depth profile of secondary particle spectra in the lunar soil has a maximum between 0.5 and 1 m below the surface, depending on particle type and energy. The angular distribution of secondary particles (in particular neutron, ‐rays, electrons) with energy 1 MeV is mostly isotropic, while higher energy particles preferentially propagate downward. Our model provides full coverage of the spatial, directional, and energy information of the radiation field at the surface and subsurface of the Moon, which can serve for designing future human bases on the Moon.

Investigation of Ion and Neutral Atom Scattering Processes with Neutral Particle Facility

Abstract—This article presents the results of an experiment on the processes of scattering of ions and neutral atoms on targets from polished tungsten obtained using a neutral particle facility. The neutral particle facility is a laboratory instrument designed to study the processes of reflection and scattering of charged particles and neutral atoms on the surfaces of targets made of various materials. The facility allows one to record the energy and angular distributions of secondary particles formed as a result of the interaction of a stream of ions of different energies or neutral atoms with a target installed at different angles.

NDPlot - A plotting tool for nuclear data

NDPlot is an efficient plotting tool for nuclear data. It is not only a plotting tool, but also an integrated application system. The first beta version of NDPlot was released in October 2018. The current version is 0.94 beta. NDPlot can plot experimental and evaluated data of reaction cross sections, angular distributions of secondary particles, energy distributions of secondary particles and product energy-angle distributions etc. It also provides data processing functions such as curve summation capability to meet user’s requirements.

Beam loss issue study on the extraction system of a superconducting cyclotron at HUST

The study of proton therapy equipment has earned more and more attention in China in recent years. A superconducting cyclotron based proton therapy facility is being developed at Huazhong University of Science and Technology (HUST). Since the proton beam is extracted out of the compact, high energy cyclotron by electrostatic deflectors followed by a series of magnetic channels, the fierce interaction between the proton beam and the deflector septum is the main cause of beam loss, leading to unwanted excess radiation and heat. Excess Radiation effect results in activation or damage to superconducting materials and high risk of quench of superconducting magnets, while thermal effect involves temperature rise and deformation of the septum, both of these phenomena put extraordinary demands on high efficiency extraction of the cyclotron. This paper introduces the design of the electrostatic deflector, including the structure optimization and the material selections. Moreover, in order to minimize the damage to the deflector destruction caused by the proton beam loss, numerical simulations of radiation effect and thermal effect have been conducted by applying Monte Carlo Geant4 code and computational fluid dynamics (CFD) on ANSYS respectively. The energy depositions of the proton beam in diverse septum materials are compared. Meanwhile, the energy and angular distributions of secondary particles are obtained. The maximum temperatures and deformations of the septum in various cases of thickness and material are investigated. The results based on these analyses will give us valuable implications for the development of a superconducting cyclotron.

Experiment Design of Secondary Neutron and Charged-Particle Measurement with Stopping Targets Bombarded by 100 and 230 MeV/amu 4He Ions

Stopping target measurements with energetic ion beams are important for building and validating physics models used to predict nuclear fragmentation fields created by interactions between incoming primary ions and target materials. However, the values of the ratio of primary ion range R to target depth d (R/d) are not the same in several of the existing measurements, and as such, this makes the intercomparison between those measurements complicated without corrections for differences in secondary particle transport through differing amounts of target material. Therefore, this work aims to study the influence of the target geometry on the angular distributions of secondary particles. Cases with 100 and 230 MeV/amu 4He ions bombarding stopping water and iron targets with various dimensions were studied by using the transport model code PHITS (Particle and Heavy Ion Transport code System). With increasing target depth, the impact on the attenuation of secondary particles is more significant for lighter target mass and higher-energy projectiles at forward angles. Also, with deeper targets, more interactions occur between the secondary particles and the target nuclei, which results in more targetlike fragments at large and backward angles. With respect to the cross-sectional area of the stopping targets, the forward angular distributions are similar to the system with smaller cross-sectional area of the targets; however, charged particles are significantly attenuated at large angles, whereas no general rule was found for secondary neutrons at large and backward angles. These results indicate that in order to compare the angular distributions from various stopping target measurements, it will be necessary to utilize a radiation transport code to correct the differences caused by target geometry.

SU‐E‐T‐519: Emission of Secondary Particles From a PMMA Phantom During Proton Irradiation: A Simulation Study with the Geant4 Monte Carlo Toolkit

Purpose:Proton therapy exhibits several advantages over photon therapy due to depth‐dose distributions from proton interactions within the target material. However, uncertainties associated with protons beam range in the patient limit the advantage of proton therapy applications. To quantify beam range, positron‐emitting nuclei (PEN) and prompt gamma (PG) techniques have been developed. These techniques use de‐excitation photons to describe the location of the beam in the patient. To develop a detector system for implementing the PG technique for range verification applications in proton therapy, we studied the yields, energy and angular distributions of the secondary particles emitted from a PMMA phantom.Methods:Proton pencil beams of various energies incident onto a PMMA phantom with dimensions of 5 x 5 x 50 cm3 were used for simulation with the Geant4 toolkit using the standard electromagnetic packages as well as the packages based on the binary‐cascade nuclear model. The emitted secondary particles are analyzed .Results:For 160 MeV incident protons, the yields of secondary neutrons and photons per 100 incident protons were ~6 and ~15 respectively. Secondary photon energy spectrum showed several energy peaks in the range between 0 and 10 MeV. The energy peaks located between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (~ 4.4 MeV) and 16O (~ 6 MeV), respectively. Most of the escaping secondary neutrons were found to have energies between 10 and 100 MeV. Isotropic emissions were found for lower energy neutrons (<10 MeV) and photons for all energies, while higher energy neutrons were emitted predominantly in the forward direction. The yields of emitted photons and neutrons increased with the increase of incident proton energies.Conclusions:A detector system is currently being developed incorporating the yields, energy and angular distributions of secondary particles from proton interactions obtained from this study.

Secondary particle emission from a ferromagnetic binary compound

Secondary ion emission from an ion-bombarded binary compound in the ferro- and paramagnetic states has been studied using experimental methods and molecular dynamics simulations. The experiments were performed with a widely used NiPd binary compound, which was bombarded by obliquely incident 10-keV Ar ions. It is established that the intensity of Ni+ and Pd+ ion emission from a polycrystalline NiPd sample decreases significantly when it passes from the ferromagnetic to paramagnetic state. This effect is explained by a change in the surface binding energy and density of surface states at the Fermi level and by a cumulative process related to sputtering. The energies and directions of emission of secondary particles from poly- and single-crystalline NiPd samples in the ferromagnetic state have been jointly studied. It is established that the maximum of the polar angular distribution of secondary particles deviates toward the normal to the irradiated surface with a decrease in their energy. A difference in the azimuthal distribution of emitted Ni and Pd particles has been observed during the bombardment of a (001)NiPd crystal face and explained by specific features of correlated collisions. The best agreement of experimental data with the results of molecular dynamics simulations is obtained if the calculations are performed with allowance for an experimentally established modified composition of the three uppermost surface layers [39].

Simulating Makrofol as a detector for neutron-induced recoils

The response of solid-state nuclear track detector is extremely dependent on incident angles of neutrons, which determine the angular distribution of secondary particles. In this paper, the authors present a method to investigate the angular response of Makrofol detectors. Using the C++-based Monte-Carlo tool-kit Geant4 in combination with SRIM and our MATLAB codes, we simulated the angular response of Makrofol. The simulations were based on the restricted energy loss model, and the concept of energy threshold and critical angle. Experiments were carried out with (252)Cf neutrons to verify the simulation results.

Coherent radio emission from cosmic ray air showers computed by Monte-Carlo simulation with SElFAS

We present here the first results of SElFAS (Simulation of Electric Field emitted by Air Shower), a new Monte-Carlo simulation of the radio emission by cosmic ray extensive air shower. The simulation is based on the complete geometrical description of secondary electrons and positrons created in air showers generated by protons above 10 PeV. The energy, position and angular distributions of secondary particles are extracted from CORSIKA simulations [1]. The electric field is then computed for each secondary particle during its travel in the atmosphere using the well-known equation of a moving charge which undergoes an acceleration. The total signal emitted by the air shower is per consequent the superposition of all particles contributions and it is computable for any ground position. We present the results obtained for the east–west and north–south polarizations of the total electric field. These polarizations are usually measured by radio detectors such as CODALEMA, LOPES, RAuger and AERA (Auger Engineering Radio Array). The characteristics and the comprehension of the radio emission of cosmic ray extensive air shower are crucial for the development of large radio detectors array.

Wavelet analysis of angular distributions of secondary particles in high-energy nucleus-nucleus interactions: Irregularity of particle pseudorapidity distributions

Experimental data on interactions of sulfur and oxygen nuclei with photoemulsion nuclei at energies of 200 and 60 GeV/nucleon are analyzed with the help of a continuous wavelet transform. Irregularities in pseudorapidity distributions of narrow groups of the secondary shower particles in these interactions are observed upon application of the second-order derivative of a Gaussian as a wavelet. The irregularities can be interpreted as the existence of preference emission angles of groups of particles. Such an effect is expected during emission of Cherenkov gluons in nucleus-nucleus collisions. Some of the positions of the observed peculiarities on the pseudorapidity axis coincide with those found by Dremin et al. (I. M. Dremin et al., Phys. Lett. B 499, 97 (2001)).

Decoupling of anomalous top-quark-decay vertices in angular distribution of secondary particles

Angular distribution of a secondary particle from top-quark decays is studied in a simple and general manner, paying careful attention to how relevant the top-quark production mechanism is. The conditions that lead to the distribution free from any possible anomalous top-quark-decay interactions are specified. Some approximations adopted in earlier papers are relaxed and their relevance is discussed.

The influence of cone-covered surface structures on sputtering and secondary electron emission: Model

Abstract The yield and the polar angular distributions of secondary particles emitted from cone-covered surfaces were studied. A model taking into account both the influence of the local incidence angle I and the blocking of the emitted particles by the surface relief was elaborated. For an emission angle a, the transport effect of the particles generated inside the solid was simulated by the standard relation F(a) = (cos a) n and the emission dependence on the local incidence angle was assumed to behave as E(I) = (cos I) -m . Calculations showed that for m= 1 the surface topography only slightly alters the polar angular distribution shape but the yield of the collected particles is always higher than that from a flat surface when m is more than unity. For n= 2, the shape of the distribution curve is significantly different from that of the corresponding flat surface whatever the m values. For n=0, when E(I) very rapidly increases with the incidence angle both the angular distributions shape and the yield are strongly modified by the surface topography.

Angular distribution of secondary particles produced in the intersecting storage rings at an energy equivalent to 1500 GeV

The angular distribution of secondary relativistic charged particles was measured in the ISR by means of nuclear emulsions used as detectors. The result confirms the cosmic-ray observations of a dip in the angular distribution around 90° in the centre-of-mass system of the colliding protons.

Angular distribution of secondary particles in the thermodynamic model

Angular distributions obtained from the thermodynamic model of multi-particle production are compared with cosmic ray results at 175 GeV/ c and with angular distributions obtained according to parametrizations with Feynman like scaling behaviour.

On the azimuthal effects of two prong πN and three prong DD events produced by 17.2 GeV/c π− mesons

A deviation from isotropy in the azimuthal angular distribution of secondary particles of two and three prong pion-nucleon interactions is observed in emulsion at 17.2 GeV/c. Attempts are made using Monte Carlo calculations to interpret these azimuthal effects on the basis of (i) the kinematics of reactions π− p→pπ− (k π0) and π− p→nπ+π− (k′ π0) and (ii) the diffraction dissociation of pions on nuclei. A new method is given for the selection of the contribution of DD interactions from three prong events. Using this method λDD=(1065±288)m and λDD=(113±13)m are obtained for the mean free path of the diffraction dissociation in emulsion at ∼7 and 17.2 GeV/c, respectively. The possible influence of theDeck effect in the case of three prong events is also investigat

The installation for the study of nuclear interactions at 1012–1013 eV

A description is given of the installation which was constructed at an altitude of 3 200 m for the study of nuclear interactions at energies of 1012–1013 eV. The apparatus, which has an effective area of 10 m2, includes an ionization calorimeter and a Cerenkov total absorption spectrometer for the measurement of the energies of the primary particles, a μ-meson detector consisting of Cerenkov counters and spark chambers, and also a spark chamber for the study of the angular distribution of secondary particles.

Inelastic Interactions of Particles at High Energies. II. (Energy and angular distributions of secondary particles)

Inelastic Interactions of Particles at High Energies. II. (Energy and angular distributions of secondary particles)

Analysis of angular distribution of secondary particles in ultra high energy nucleon-nucleon collisions

Starting from the exact expression for a transition probability in the relativistic angular momentum representation and using some approximations following from the assumed peripherality of collisions we have obtained an expression for the angular distribution of secondary particles. The differential and integral angular distributions calculated for the energies 10 3 GeV, 10 4 GeV, 10 5 GeV, lead to a natural explanation of the appearance of two maxima in the angular distributions.

ANGULAR DISTRIBUTION OF NUCLEAR INTERACTIONS OF HIGH ENERGY COSMIC RAY PARTICLES WITH PARAFFIN

A cloud chamber experiment is described, in which the angular distribution of secondary particles produced in nuclear interaction by high energy cosmic ray particles with paraffin has been studied. Sixty-four ns ≥4 events with average primary energy of 70 BeV have been analysed. The result shows that, in this energy region, the angular distribution in CMS is not isotropic but possesses maxima in the 0° and 180° directions; furthermore, there is already an appreciable fraction ( 20%) of the events with angular distribution exhibiting the features given by the fire-ball model.