Galactic Cosmic Ray Spectrum Research Articles

Shielding effectiveness of different polymers and low-density hydrides in a combined radiation shield for crewed interplanetary space missions

Exposure to Galactic cosmic rays (GCR) and solar particle events (SPE) has been identified as one of the critical barriers for long term space missions that impose both immediate and delayed health hazards on the astronauts. There are two types of protective shields available namely active and passive shields, and combining these two shields can be a useful strategy. The study aims to present the effectiveness of a combined radiation shield containing an active toroidal shield with a layer of passive shield made of different polymers or low-density hydrides. The active shield is capable of deflecting protons (Z < 1) with energies below 700 MeV/n and for Alpha, and Fe ions (Z > 1) it can deflect up to 200 MeV/n and 175MeV/n respectively. The shielding effectiveness of polymers and hydrides with different thicknesses was investigated with Monte Carlo simulations performed by means of Geant4/MULASSIS. The shielding properties were studied using proton, alpha, and Fe ions with energies of 1 GeV/n. Nuclear stopping power and Fast Neutron Removal Cross Section (FNRCS) were calculated using SRIM and PHY-X/PSD. For the 20 gm/cm2 thick layer made of polymers, the reduction of dose equivalent for proton, alpha, and Fe ion of 1GeV/n are 5.44%, 54.34%, and 63.76% respectively and in the case of Low-density Hydrides with the same dimension, the rates are 4.12%, 55.3%, and 76.88%. Low-density hydrides demonstrated better radiation shielding capability than the polymers. The results are compared with OLTARIS for GCR spectra of 2010 solar minimum. The downsides of this type of shield are also briefly covered.

Evaluating the effects of low-dose simulated galactic cosmic rays on murine hippocampal-dependent cognitive performance.

Space exploration has advanced substantially over recent decades and plans to increase the duration of deep space missions are in preparation. One of the primary health concerns is potential damage to the central nervous system (CNS), resulting in loss of cognitive abilities and function. The majority of ground-based research on space radiation-induced health risks has been conducted using single particle simulations, which do not effectively model real-world scenarios. Thus, to improve the safety of space missions, we must expand our understanding of the effects of simulated galactic cosmic rays (GCRs) on the CNS. To assess the effects of low-dose GCR, we subjected 6-month-old male BALB/c mice to 50 cGy 5-beam simplified GCR spectrum (1H, 28Si, 4He, 16O, and 56Fe) whole-body irradiation at the NASA Space Radiation Laboratory. Animals were tested for cognitive performance with Y-maze and Morris water maze tests 3 months after irradiation. Irradiated animals had impaired short-term memory and lacked spatial memory retention on day 5 of the probe trial. Glial cell analysis by flow cytometry showed no significant changes in oligodendrocytes, astrocytes, microglia or neural precursor cells (NPC's) between the sham group and GCR group. Bone marrow cytogenetic data showed a significant increase in the frequency of chromosomal aberrations after GCR exposure. Finally, tandem mass tag proteomics identified 3,639 proteins, 113 of which were differentially expressed when comparing sham versus GCR exposure (fold change > 1.5; p < 0.05). Our data suggest exposure to low-dose GCR induces cognitive deficits by impairing short-term memory and spatial memory retention.

Constraining the Position of the Knee in the Galactic Cosmic-Ray Spectrum with Ultra-high-energy Diffuse γ-Rays

The diffuse γ-ray emission was measured up to 957 TeV by the Tibet-ASγ experiment recently. Assuming that it is produced by the hadronic interaction between cosmic-ray nuclei and the interstellar medium, it requires that the cosmic-ray nuclei should be accelerated well beyond PeV energies. Measurements of the cosmic-ray spectra for different species show diverse results at present. The Tibet experiments showed that the spectrum of proton plus helium has an early knee below PeV. If this is correct, the diffuse γ-ray emission would suggest an additional component of Galactic cosmic rays above PeV energies. This second component may originate from a source population of so-called PeVatrons revealed by recent ultra-high-energy γ-ray observations and could contribute to the cosmic-ray fluxes up to the energy of the second knee. On the other hand, the KASCADE measurement showed that the knee of protons is higher than PeV. In this case, the diffuse γ-rays observed by Tibet-ASγ can be well accounted for by only one cosmic-ray component. These two scenarios (i.e., the Tibet and KASCADE knees) could be distinguished by the spectral structures of diffuse γ-rays and cosmic-ray nuclei. Future measurements of spectra of individual nuclei by HERD and LHAASO experiments and diffuse γ-rays by LHAASO can jointly constrain these two scenarios.

Improved Cosmic Ray Spectrum and Intensity in Middle Atmosphere (CORSIMA) Model Considering Six Characteristic Energy Intervals

&#x0D; &#x0D; &#x0D; The new model CORSIMA (COsmic Ray Spectrum and Intensity in Mid- dle Atmosphere) is presented in this study. Numerical determinations of the spectrum and intensity of Galactic Cosmic Rays (GCR) for the middle atmo- sphere and the lower altitudes of the ionosphere (30–80 km) are presented. These altitudes are above the Regener–Pfotzer maximum. The primary spec- tra of protons and helium (alpha particles) are used. According to the amount of particles, cosmic rays consist of 92% protons, 6% helium nuclei, 1% heavier elements, and 1% electrons (GINZBURG and SIROVATSKY [19]).&#x0D; We also use the approximation of ionization losses (Bohr–Bethe–Bloch formula) in six characteristic energy intervals, including the charge decrease interval for electron capture. In this way, the accuracy of the obtained results is improved.&#x0D; Analytical expressions for the contributions of the energy intervals are provided. An approximation of the ionization function on six energy intervals is used and the charge decrease interval for electron capture is studied. Numerical calculations are performed using computational algebra systems.&#x0D; The development of this research is important for a better understanding of the processes and mechanisms of space weather. The GCR affect the ionization and electrical parameters in the atmosphere and also the chemical processes (ozone formation and depletion in the stratosphere) in it. These effects can be significantly enhanced during strong and moderately strong solar proton events and geomagnetic storms.&#x0D; &#x0D; &#x0D;

Comparison of the particle flux measured by Liulin-MO dosimeter in ExoMars TGO science orbit with those calculated by models

The knowledge of the space radiation environment in spacecraft transition and in Mars vicinity is of importance for the preparation of the human exploration of Mars. ExoMars Trace Gas Orbiter (TGO) was launched on March 14, 2016 and was inserted into circular Mars science orbit (MSO) with a 400 km altitude in March 2018. The Liulin-MO dosimeter is a module of the Fine Resolution Epithermal Neutron Detector (FREND) aboard ExoMars TGO and has been measuring the radiation environment during the TGO interplanetary travel to Mars and continues to do so in the TGO MSO. One of the scientific objectives of the Liulin-MO investigations is to provide data for verification and benchmarking of the Mars radiation environment models. In this work we present results of comparisons of the flux measured by the Liulin-MO in TGO Mars orbit with calculated estimations. Described is the methodology for estimation the particle flux in Liulin-MO detectors in MSO, which includes modeling the albedo spectra and procedure for calculation the fluxes, recorded by Liulin-MO on the basis of the detectors shielding model. The galactic cosmic rays (GCR) and Mars albedo radiation contribution to the detectors count rate was taken into account. The GCR particle flux was calculated using the Badhwar O'Neil 2014 model for December 1, 2018. Detailed calculations of the albedo spectra of protons, helium ions, neutrons and gamma rays at 70 km height, performed with Atmospheric Radiation Interaction Simulator (AtRIS), were used for deriving the albedo radiation fluxes at the TGO altitude. In particular, the sensitivity of the Liulin-MO semiconductor detectors to neutron and gamma radiation has been considered in order to calculate the contribution of the neutral particles to the detected flux. The results from the calculations suggest that the contribution of albedo radiation can be about 5% of the measured total flux from GCR and albedo at the TGO altitude. The critical effect of TGO orientation, causing different shading of the GCR flux by Mars, is also analysed in detail. The comparison between the measurements and estimations shows that the measured fluxes exceed the calculated values by at least 20% and that the effect of TGO orientation change is approximately the same for the calculated and measured fluxes. Accounting for the ACR contribution, secondary radiation and the gradient of GCR spectrum from 1 AU to 1.5 AU, the calculated flux may increase to match the measurement results. The results can serve for the benchmarking of GCRs models at Martian orbit.

A New Model for Nowcasting the Aviation Radiation Environment With Comparisons to In Situ Measurements During GLEs

AbstractSignificant increases to the atmospheric radiation environment are recorded by a network of ground level neutron monitors as ground level enhancements (GLEs). These space weather phenomena pose a risk to aviation via single event effects in aircraft electronics and ionizing dose to passengers and crew. Under the UK Space Weather Instrumentation, Measurement, Modeling and Risk programme, we have developed a new model to provide nowcasts of the aviation radiation environment, including both the galactic cosmic ray (GCR) background and during GLE events. The Model for Atmospheric Ionising Radiation Effects (MAIRE+) uses multiple data sources to characterize primary GCR and GLE particle spectra and combines these with precalculated geomagnetic and atmospheric response matrices to predict particle fluxes from ground level to 20 km altitude across the entire globe. Two European neutron monitors (located at Oulu in Finland and Dourbes in Belgium) are used as the primary indicators of GLE intensity in order to maximize accuracy over UK airspace. Outputs from MAIRE+ for the historical GLEs in September and October 1989 are compared to recalibrated empirical data from a solid‐state detector that was carried on Concorde in that period. The model will be hosted in the UK and will provide additional capability to the Met Office Space Weather Operations Center (MOSWOC).

Radiobiological damage by space radiation: extension of the BIANCA model to heavy ions up to iron, and pilot application to cosmic ray exposure

Space research seems to be object of a renewed interest, also considering that human missions to the Moon, and possibly Mars, are being planned. Among the risks affecting such missions, astronauts’ exposure to space radiation is a major concern. In this work, the question of the evaluation of biological damage by Galactic Cosmic Rays (GCR) was addressed by a biophysical model called BIophysical ANalysis of Cell death and chromosome Aberrations (BIANCA), which simulates the induction of cell death and chromosome aberrations by different ions. While previously BIANCA has been validated for calculating cell death along hadrontherapy beams up to oxygen, herein the approach was extended up to Fe ions. Specifically, experimental survival curves available in literature for V79 cells irradiated by Si-, Ne-, Ar- and Fe-ions were reproduced, and a reference radiobiological database describing V79 cell survival as a function of ion type (1 ⩽ Z ⩽ 26), energy and dose was constructed. Analogous databases were generated for Chinese hamster ovary hamster cells and human skin fibroblasts, finding good agreement between simulations and data. Concerning chromosome aberrations, which are regarded as radiation risk biomarkers, dicentric data in human lymphocytes irradiated by heavy ions up to iron were reproduced, and a radiobiological database allowing calculation of lymphocyte dicentric yields as a function of dose, ion type (1 ⩽ Z ⩽ 26) and energy was constructed. Following interface between BIANCA and the FLUKA Monte Carlo transport code, a feasibility study was performed to calculate the relative biological effectiveness (RBE) of different GCR spectrum components, for both dicentrics and cell death. Fe-ions, although representing only 10% of the total absorbed dose, were found to be responsible for about 35%–40% of the RBE-weighted dose. Interestingly, the RBE for dicentrics was higher than that for cell survival. More generally, this work shows that BIANCA can calculate RBE values for cell death and lymphocyte dicentrics not only for ion therapy, but also for space radiation.

Spectral softening in core-collapse supernova remnant expanding inside wind-blown bubble

Context. Galactic cosmic rays (CRs) are widely assumed to arise from diffusive shock acceleration, specifically at shocks in supernova remnants (SNRs). These shocks expand in a complex environment, particularly in the core-collapse scenario as these SNRs evolve inside the wind-blown bubbles created by their progenitor stars. The CRs at core-collapse SNRs may carry spectral signatures of that complexity. Aims. We study particle acceleration in the core-collapse SNR of a progenitor with an initial mass of 60 M⊙ and realistic stellar evolution. The SNR shock interacts with discontinuities inside the wind-blown bubble and generates several transmitted and reflected shocks. We analyse their impact on particle spectra and the resulting emission from the remnant. Methods. To model the particle acceleration at the forward shock of a SNR expanding inside a wind bubble, we initially simulated the evolution of the pre-supernova circumstellar medium (CSM) by solving the hydrodynamic equations for the entire lifetime of the progenitor star. As the large-scale magnetic field, we considered parameterised circumstellar magnetic field with passive field transport. We then solved the hydrodynamic equations for the evolution of a SNR inside the pre-supernova CSM simultaneously with the transport equation for CRs in test-particle approximation and with the induction equation for the magnetohydrodynamics in 1D spherical symmetry. Results. The evolution of a core-collapse SNR inside a complex wind-blown bubble modifies the spectra of both the particles and their emission on account of several factors including density fluctuations, temperature variations, and the magnetic field configuration. We find softer particle spectra with spectral indices close to 2.5 during shock propagation inside the shocked wind, and this softness persists at later evolutionary stages. Further, our calculated total production spectrum released into the interstellar medium demonstrates spectral consistency at high energy (HE) with the injection spectrum of Galactic CRs, which is required in propagation models. The magnetic field structure effectively influences the emission morphology of SNRs as it governs the transportation of particles and the synchrotron emissivity. There is rarely a full correspondence of the intensity morphology in the radio, X-ray, and gamma-ray bands.

Model of galactic cosmic ray spectrum above the Earth’s atmosphere

Abstract Galactic cosmic ray transport in the heliosphere is described by the well-known Parker transport equation. In 1969, Fisk and Axford [1] presented approximate analytical solutions to the cosmic ray transport equation. One of their solutions was later used to construct useful semi-empirical models describing the energy spectra of charged particles during the solar cycle. In this paper, a simplified model of the galactic cosmic ray spectrum is presented. The model can be used to describe the galactic spectra of protons and helium nuclei during the 11-year solar cycle in interplanetary space at about 1 AU.

Advances in the Research on Cosmic Rays and Their Impact on Human Activities

It is well known that the galactic cosmic-ray spectrum extends over 14 orders of magnitudes in energy and about 12 in intensity, and the detection methods can be divided into two classes [...]

Protons Interaction with Nomex Target: Secondary Radiation from a Monte Carlo Simulation with Geant4

The study of suitable materials to shield astronauts from Galactic Cosmic Rays (GCR) is a topic of fundamental importance. The choice of the material must take into account both the secondary radiation produced by the interaction between primary radiation and material and its shielding ability. The physics case presented here deals with the interaction of a proton beam with a Nomex shield, namely, a target material with a mass thickness of 20 g cm−2. The study was conducted with the simulation code DOSE based on the well-known simulation package Geant4. This article shows the properties of secondary radiations produced in the target by the interaction of a proton beam in an energy range characterizing the GCR spectrum. We observed the production of ions of masses and charges lower than the chemical elements that make up Nomex, and also a significant production of neutrons, protons, and 𝛼 particles.

Helium Fluxes Measured by the PAMELA Experiment from the Minimum to the Maximum Solar Activity for Solar Cycle 24

Abstract Time-dependent energy spectra of galactic cosmic rays (GCRs) carry fundamental information regarding their origin and propagation. When observed at the Earth, these spectra are significantly affected by the solar wind and the embedded solar magnetic field that permeates the heliosphere, changing significantly over an 11 yr solar cycle. Energy spectra of GCRs measured during different epochs of solar activity provide crucial information for a thorough understanding of solar and heliospheric phenomena. The PAMELA experiment collected data for almost 10 years (2006 June 15–2016 January 23), including the minimum phase of solar cycle 23 and the maximum phase of solar cycle 24. In this paper, we present new spectra for helium nuclei measured by the PAMELA instrument from 2010 January to 2014 September over a three-Carrington-rotation time basis. These data are compared to the PAMELA spectra measured during the previous solar minimum, providing a picture of the time dependence of the helium-nuclei fluxes over a nearly full solar cycle. Time and rigidity dependencies are observed in the proton-to-helium flux ratios. The force-field approximation of the solar modulation was used to relate these dependencies to the shapes of the local interstellar proton and helium-nuclei spectra.

Dissecting Differential Complex Behavioral Responses to Simulated Space Radiation Exposures.

This study has established the impact that space radiation exposure has on the capability of rats to successfully negotiate behavioral tasks of increasing complexity. Rats previously exposed to a low dose (10 cGy) of either 4He ions or a cocktail of 6 ions that simulates the galactic cosmic ray spectrum (GCRSim) were screened initially on an attentional set shifting (ATSET) task that provides a measure of executive function. Rats that exhibited superior ATSET performance were then selected for follow up behavioral assessments designed to evaluate how the cohort of "good performers" would fare when presented with a novel behavioral paradigm termed the Associative Recognition Memory and Interference Touchscreen (ARMIT) task. Central to this approach was to discriminate if/how adaptive problem solving would be impacted by changing the options of associative cues presented over several learning sessions to obtain a reward under time constraints using this newly designed touch screen-based task. Data from these studies indicated that when faced with an increased cognitive load, possibly due to interference from prior associative recognition memories, rats exhibited impairments in their capability to negotiate task dynamics and efficiently engage abstract reasoning. Interestingly, while exposure to the GCRSim adversely impacted problem-solving capabilities, single ion exposure did not, pointing to the nuances of space radiation exposure on CNS functionality. Since the selected behavioral paradigms exhibit strong cross-species correlates, data suggest that rodents succumb to increased task rigor as observed in humans, and make similar mistakes when challenged with the interference of overlapping associative memories. Furthermore, data clearly points to the limitations of over-reliance on a single cognitive endpoint that may underestimate global neurocognitive risk due to space radiation exposure.

A Numerical Study of the Solar Modulation of Galactic Protons and Helium from 2006 to 2017

Abstract With continuous measurements from space-borne cosmic-ray detectors such as AMS-02 and PAMELA, precise spectra of galactic cosmic rays over the 11 yr solar cycle have become available. For this study, we utilize proton and helium spectra below 10 GV from these missions from 2006 to 2017 to construct a cosmic-ray transport model for a quantitative study of the processes of solar modulation. This numerical model is based on Parker’s transport equation, which includes four major transport processes. The Markov Chain Monte Carlo method is utilized to search the relevant parameter space related to the drift and the diffusion coefficients by reproducing and fitting the mentioned observed spectra. The resulting best-fit normalized χ 2 is mainly less than 1. It is found that (1) when reproducing these observations the parameters required for the drift and diffusion coefficients exhibit a clear time dependence, with the magnitude of the diffusion coefficients anticorrelated with solar activity; (2) the rigidity dependence of the resulting mean free paths varies with time, and their rigidity dependence at lower rigidity can even have a larger slope than at higher rigidity; (3) using a single set of modulation parameters for each pair of observed proton and helium spectra, most spectra are reproduced within observational uncertainty; and (4) the simulated proton-to-helium flux ratio agrees with the observed values in terms of its long-term time dependence, although some discrepancy exists, and the difference is mostly coming from the underestimation of proton flux.

Beryllium Isotopes in the PAMELA Experiment

Analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the orbital experiment of the PAMELA collaboration makes it possible to study the problems of the origin and propagation of cosmic rays in the Galaxy. The data of the PAMELA magnetic spectrometer, due to their high statistical and methodological accuracy, ensured significant progress in the study of the isotopic composition of light nuclei from H to Be in GCR in the energy range ~ 0.1-1 GeV/nucleon and for the first time made it possible to estimate the contribution to GCR of Local Interstellar Sources (LIS) from close (∼ 100 pc) of recent (~ million years) supernova explosions. To date, the isotopic composition of beryllium nuclei in GCR has been measured only for 7Be./9Be, 10Be/9Be ratios in the energy range of ∼ 100 MeV/nucleon in the space experiments IMP 7/8, Voyager, Ulysses, ACE/CRIS and for 10Be/9Be in balloon experiment with a superconducting magnet ISOMAX-98 for energies 0.2-1.0 and 1.1-2.0 GeV/nucleon. In this work, using flight data PAMELA 2006-2014, on the rigidity of the detected nuclei and their velocity (time-of-flight analysis and ionization losses in the multilayer calorimeter of the instrument), a new analysis of the isotopic composition of beryllium nuclei in the energy range of ~ 0.1-1.4 GeV/nucleon has been carried out. The results of isotopic analysis of beryllium nuclei in GCR (spectra 7Be, 9Be, 10Be and 7Be/9Be, 10Be/9Be - ratio depending on the rigidity and energy of nuclei) in comparison with the existing measurement and calculation data will be presented.

Galactic Cosmic Rays, Cosmic-Ray Variations, and Cosmogenic Nuclides in Meteorites

Abstract We present a new generation of model calculations for cosmogenic production rates in various types of solar system bodies. The model is based on the spectra for primary and secondary particles calculated using the INCL++6 code, which is the most reliable and most sophisticated code available for spallation reactions. Thanks to the recent improvements (extending the code to lower and higher energies and considering light charged particles as ejectiles and projectiles), we can for the first time directly consider primary and secondary Galactic α particles. We calculate production rates for 22Na, 10Be, and 26Al in an L-chondrite with a radius of 45 cm and in the Apollo 15 drill core, and we determine the long-term average Galactic cosmic-ray (GCR) spectrum (represented by the solar modulation potential Φ) in the meteoroid orbits at ∼3 au of Φ = 600 MV and at 1 au, i.e., for Earth and Moon of Φ = 660 MV. From this, we calculate a long-term average GCR gradient in the inner solar system of ∼5% au−1. Finally, we discuss the possibility of studying temporal GCR variations and meteoroid orbits using production rate ratios of short- and long-lived radionuclides.

Carbon Isotopes in the PAMELA Experiment

An analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the orbital experiment of the PAMELA collaboration allows us to study the problems of the origin and propagation of cosmic rays in the Galaxy. Due to the high statistical and methodological accuracy, the data of the PAMELA magnetic spectrometer provided significant progress in studying the isotopic composition of light nuclei from H to Be in the GCR in the energy region of ∼ 0.1-1 GeV / nucleon and for the first time made it possible to estimate the contribution of local sources from close ones to the GCR (∼ 100 pc) of recent (∼ 106 yrs) supernova explosions. To date, the isotopic composition of carbon nuclei in the GCR has been measured only for the 13C / 12C ratio in the energy region ∼ 0.05-0.13 GeV / nucleon in the VOYAGER 1.2 space experiment and the upper limit for the 14C / 12C ratio was estimated in the ACE / CRIS experiment for energies 0.12-0.43 MeV / nucleon. In this work, using PAMELA flight data 2006-2014, on the rigidity of the detected nuclei and their speed (time-of-flight analysis and ionization losses in the multilayer calorimeter of the device), an attempt was made to determine the isotopic composition of carbon nuclei in the energy region of ∼ 0.1-1 GeV / nucleon. The half-life of 14C nuclei is 5730 years and can be detected in the case of a supernova explosion in the last ∼ 5 104 years at a distance of ∼ 100 200 pc. The results of isotope analysis of carbon nuclei in GCR (spectra 12C, 13C, 14C and 14C / 12C - ratio depending on the rigidity and energy of the nuclei) in comparison with the existing measurement data will be presented.

Long- and Short-term Variability of Galactic Cosmic-Ray Radial Intensity Gradients between 1 and 9.5 au: Observations by Cassini, BESS, BESS-Polar, PAMELA, and AMS-02

Abstract Spatial gradients of galactic cosmic-ray (GCR) fluxes are important for studying charged particle transport in the heliosphere. Little is known so far about how these gradients evolve with time. Here we present how the radial gradient (G r ) evolves between 2006 January and 2017 September using Cassini measurements of &gt;300 MeV protons, which we combine with proton spectra obtained by advanced observatories at Earth (BESS, BESS-Polar, PAMELA, and AMS-02). All gradient calculations were performed for a nearly constant heliocentric distance of Cassini from Earth’s orbit and near the ecliptic, thus revealing only how G r changes with time. The variability patterns of G r are well established as they rely on a single data set for ∼9.5 au and accurately cross-calibrated GCR spectra for Earth at 1 au. We show that over solar-cycle timescales, G r is regulated by both the polarity of the solar magnetic field and the solar-cycle phase. During the negative-polarity phase (A &lt; 0, 2006–2014), gradients are stronger and more stable with an average of G r = 3.5 ± 0.3%/au and with evidence of a minimum around the 2009 solar minimum. The gradient peaks at ∼4%/au around the solar maximum and subsequently experiences a gradual drop to ∼2%/au in the A &gt; 0 phase (2014–2017). Regular G r enhancements over yearly or biennial timescales are also observed, in phase with quasi-biennial oscillations in GCR intensity. While all aforementioned results are based on Cassini measurements that are integral in energy, they are most representative for GCR protons in the low gigaelectronvolt range.

Are Further Cross Section Measurements Necessary for Space Radiation Protection or Ion Therapy Applications? Helium Projectiles

The helium (4He) component of the primary particles in the galactic cosmic ray spectrum makes significant contributions to the total astronaut radiation exposure. 4He ions are also desirable for direct applications in ion therapy. They contribute smaller projectile fragmentation than carbon (12C) ions and smaller lateral beam spreading than protons. Space radiation protection and ion therapy applications need reliable nuclear reaction models and transport codes for energetic particles in matter. Neutrons and light ions (1H, 2H, 3H, 3He, and 4He) are the most important secondary particles produced in space radiation and ion therapy nuclear reactions; these particles penetrate deeply and make large contributions to dose equivalent. Since neutrons and light ions may scatter at large angles, double differential cross sections are required by transport codes that propagate radiation fields through radiation shielding and human tissue. This work will review the importance of 4He projectiles to space radiation and ion therapy, and outline the present status of neutron and light ion production cross section measurements and modeling, with recommendations for future needs.

Inference of the Local Interstellar Spectra of Cosmic-Ray Nuclei Z ⩽ 28 with the GalProp-HelMod Framework.

Composition and spectra of Galactic cosmic rays (CRs) are vital for studies of high-energy processes in a variety of environments and on different scales, for interpretation of γ-ray and microwave observations, for disentangling possible signatures of new phenomena, and for understanding of our local Galactic neighborhood. Since its launch, AMS-02 has delivered outstanding-quality measurements of the spectra of , e ±, and nuclei: 1H-8O, 10Ne, 12Mg, 14Si. These measurements resulted in a number of breakthroughs; however, spectra of heavier nuclei and especially low-abundance nuclei are not expected until later in the mission. Meanwhile, a comparison of published AMS-02 results with earlier data from HEAO-3-C2 indicates that HEAO-3-C2 data may be affected by undocumented systematic errors. Utilizing such data to compensate for the lack of AMS-02 measurements could result in significant errors. In this paper we show that a fraction of HEAO-3-C2 data match available AMS-02 measurements quite well and can be used together with Voyager 1 and ACE-CRIS data to make predictions for the local interstellar spectra (LIS) of nuclei that are not yet released by AMS-02. We are also updating our already-published LIS to provide a complete set from 1H-28Ni in the energy range from 1 MeV nucleon-1 to ~100-500 TeV nucleon-1, thus covering 8-9 orders of magnitude in energy. Our calculations employ the GalProp-HelMod framework, which has proved to be a reliable tool in deriving the LIS of CR , e -, and nuclei 1H-8O.