High-energy Transport Research Articles

Proton lateral broadening distribution comparisons between GRNTRN, MCNPX, and laboratory beam measurements

Recent developments in NASA’s deterministic High charge (Z) and Energy TRaNsport (HZETRN) code have included lateral broadening of primary ion beams due to small-angle multiple Coulomb scattering, and coupling of the ion-nuclear scattering interactions with energy loss and straggling. This new version of HZETRN is based on Green function methods, called GRNTRN, and is suitable for modeling transport with both space environment and laboratory boundary conditions. Multiple scattering processes are a necessary extension to GRNTRN in order to accurately model ion beam experiments, to simulate the physical and biological-effective radiation dose, and to develop new methods and strategies for light-ion radiation therapy. In this paper we compare GRNTRN simulations of proton lateral broadening distributions with beam measurements taken at Loma Linda University Proton Therapy Facility. The simulated and measured lateral broadening distributions are compared for a 250 MeV proton beam on aluminum, polyethylene, polystyrene, bone substitute, iron, and lead target materials. The GRNTRN results are also compared to simulations from the Monte Carlo MCNPX code for the same projectile-target combinations described above.

Fragmentation Calculations for Energetic Ions in Candidate Space Radiation Shielding Materials

Calculations have been carried out to evaluate the effectiveness of a range of carbon- and hydrogen-rich materials for shielding against energetic heavy ions relevant to the galactic cosmic ray spectrum. Experimental work integrated with the calculations included both preparation and characterization of physical properties of candidate materials and measurements of fragmentation (breakup) of ion beams of 16O and 40Ar in the tens of GeV energy range in these materials. We have simulated the fragmentation experiments using both the HETC-HEDS and PHITS high-energy particle transport codes. The purposes of these computational simulations were to investigate the effectiveness as spacecraft personnel shielding of various novel as well as commercially available materials for future lunar and interplanetary missions and to validate the codes against experimental data. In the present contribution we report results of the fragmentation simulations and compare them with examples of the experimental measurements.

Robust modelling, measurement and analysis of human and animal metabolic systems

Modelling human and animal metabolism is impeded by the lack of accurate quantitative parameters and the large number of biochemical reactions. This problem may be tackled by: (i) study of modules of the network independently; (ii) ensemble simulations to explore many plausible parameter combinations; (iii) analysis of 'sloppy' parameter behaviour, revealing interdependent parameter combinations with little influence; (iv) multiscale analysis that combines molecular and whole network data; and (v) measuring metabolic flux (rate of flow) in vivo via stable isotope labelling. For the latter method, carbon transition networks were modelled with systems of ordinary differential equations, but we show that coloured Petri nets provide a more intuitive graphical approach. Analysis of parameter sensitivities shows that only a few parameter combinations have a large effect on predictions. Model analysis of high-energy phosphate transport indicates that membrane permeability, inaccurately known at the organellar level, can be well determined from whole-organ responses. Ensemble simulations that take into account the imprecision of measured molecular parameters contradict the popular hypothesis that high-energy phosphate transport in heart muscle is mostly by phosphocreatine. Combining modular, multiscale, ensemble and sloppy modelling approaches with in vivo flux measurements may prove indispensable for the modelling of the large human metabolic system.

PARAMETERIZATIONS OF INCLUSIVE CROSS SECTIONS FOR KAON, PROTON, AND ANTIPROTON PRODUCTION IN PROTON-PROTON COLLISIONS

Inclusive kaon, proton, and antiproton production from high-energy proton-proton collisions is studied. Various available parameterizations of Lorentz-invariant, differential cross sections, as a function of transverse momentum and rapidity, are compared with experimental data. This paper shows that the Badhwar parameterization provides the best fit for charged kaon production. For proton production, the Alper parameterization is best and for antiproton production the Carey parameterization works best. The formulae for these cross sections are suitable for use in high-energy cosmic ray transport codes.

An analytical model for the prediction of a micro-dosimeter response function

A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (δ ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCRs) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 s/ion. The ionizing radiation environment at LEO is represented by O’Neill’s GCR model (2004), covering charged particles in the 1 ⩽ Z ⩽ 28 range. O’Neill’s free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge ( Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy ( y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that, even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux between STS 51 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations at low to mid range y values. This underestimation is partly related the exclusion of the secondary pion particle production from the current version of HZETRN.

Holocene paleostorms identified by particle size signatures in lake sediments from the northeastern United States

The frequency and timing of Holocene paleofloods in the hilly terrain of New Hampshire and Maine are identified using 14C and high-resolution (cm-by-cm) particle size analysis of sediment cores taken from six post-glacial lakes (~0.1–1.4 km2). A total of nine sediment cores (4.5–6 m long) were taken near the base of stream delta foreslopes. End-member modeling of the particle-size frequency distributions from each core produces 3–5 representative end member distributions, or end members (EMs). Concurrent increases in mean and median particle size, and in the relative abundance of the coarsest EM(s), indicate increased transport capacity of inflowing tributaries, resulting from rainstorms. In all 9 cores, particle size data show clear signs of episodic, high-energy sediment transport events where proxy measurements such as loss-on-ignition and magnetic susceptibility do not, demonstrating the sensitivity of particle size analysis in paleostorm investigations made using lake sediment cores. Floods caused by storms in this region peaked around 1.4, 2.1, 3.0, 3.9, 6.8, 8.2, and 11.5 ka cal BP, and presently appear to be increasing in frequency. Periods of storminess in New Hampshire and Maine correlate well with other records of precipitation and climate in the northeastern United States during the Holocene, further supporting modern records which show tropical air masses as a primary driver of extreme precipitation events in New England (Ludlum 1996; Konrad 2001; Sisson and Gyakum 2004).

エネルギーを有効利用する高効率蓄熱輸送システムの開発(<メカライフ特集>温める,冷やす)

エネルギーを有効利用する高効率蓄熱輸送システムの開発(<メカライフ特集>温める,冷やす)

Harnessing plant biomass for biofuels and biomaterials

Harnessing plant biomass for biofuels and biomaterials

Benchmarking of calculated projectile fragmentation cross-sections using the 3-D, MC codes PHITS, FLUKA, HETC-HEDS, MCNPX_HI, and NUCFRG2

Particles and heavy ions are used in various fields of nuclear physics, medical physics, and material science, and their interactions with different media, including human tissue and critical organs, have therefore carefully been investigated both experimentally and theoretically since the 1930s. However, heavy-ion transport includes many complex processes and measurements for all possible systems, including critical organs, would be impractical or too expensive; e.g. direct measurements of dose equivalents to critical organs in humans cannot be performed. A reliable and accurate particle and heavy-ion transport code is therefore an essential tool in the design study of accelerator facilities as well as for other various applications. Recently, new applications have also arisen within transmutation and reactor science, space and medicine, especially radiotherapy, and several accelerator facilities are operating or planned for construction. Accurate knowledge of the physics of interaction of particles and heavy ions is also necessary for estimating radiation damage to equipment used on space vehicles, to calculate the transport of the heavy ions in the galactic cosmic ray (GCR) through the interstellar medium, and the evolution of the heavier elements after the Big Bang. Concerns about the biological effect of space radiation and space dosimetry are increasing rapidly due to the perspective of long-duration astronaut missions, both in relation to the International Space Station and to manned interplanetary missions in near future. Radiation protection studies for crews of international flights at high altitude have also received considerable attention in recent years. There is therefore a need to develop accurate and reliable particle and heavy-ion transport codes. To be able to calculate complex geometries, including production and transport of protons, neutrons, and alpha particles, 3-dimensional transport using Monte Carlo (MC) technique must be used. Today several particle and heavy-ion MC transport codes exist, e.g. Particle and Heavy-Ion Transport code System (PHITS), High Energy Transport Code-Human Exploration and Development of Space (HETC-HEDS), SHIELD-HIT, GEANT4, FLUKA, MARS, and MCNPX. In this paper, we present an extensive benchmarking of the calculated projectile fragmentation cross-sections from the reactions of 300 – 1000 MeV / u 28Si, 40Ar, and 56Fe on polyethylene, carbon, aluminum, and copper targets (relevant to space radioprotection) using PHITS, FLUKA, HETC-HEDS, and MCNPX, against measurements. The influence of the different models used in the different transport codes on the calculated results is also discussed. Some measured cross-sections are also compared to the calculated cross-sections using NUCFRG2, which are incorporated in the 1-dimensional, deterministic radiation transport code HZETRN.

Ordovician paleotopography as evidenced from original dips and differential compaction of dolostone and shale unconformably overlying Precambrian basement on Manitoulin Island, Canada

The Middle to basal Upper Ordovician Lindsay Formation unconformably overlies the Paleoproterozoic Bar River and Lorrain formations on Manitoulin Island (Ontario, Canada), representing a depositional hiatus of at least 1.7 billion years. The Paleoproterozoic inliers currently exposed as basement highs in the Sheguiandah region comprised a 14 km 2 area of quartz arenite archipelago during the Middle to Late Ordovician inland sea transgression of North America. The quartz arenite outcrop collectively covers an area of approximately 1.8 km 2. High-energy transport and reworking during wave and tropical storm activity along a high relief rocky shoreline is indicated by dolostone containing 2.5 m-size rounded to subrounded quartz arenite boulders with percussion marks, up to 4.5 m-size subangular quartz arenite blocks consistent with mechanical breakage along joints, fractures or bedding planes, lenticular conglomerate beds, and cracks in quartz arenite basement containing mixtures of dolostone, quartz granules and fossiliferous debris. With continued transgression, organic-rich carbonate muds were deposited under low energy conditions either on carbonate strata or directly on quartz arenite basement in restricted regions protected from the open sea. Clast size distribution in the dolostone, clast rounding, and the location of the shale/quartz arenite unconformity relative to basement highs are all consistent with a longshore current running from the present northeast to southwest, with the leeward sides of rocky islands protected from high wave and storm energy processes. Subsequent deposition of Upper Ordovician and Silurian strata resulted in burial and differential compaction of the Lindsay Formation units. The compaction may have been associated with fractures through which Mg-rich fluids migrated, locally altering the lowermost Lindsay Formation to dolostone. Evidence for differential compaction is provided by bed thickening down-dip of basement highs and boulder flanks, and higher regional dips in shale beds proximal to basement highs compared with dolostone strata. The relatively high-angle strata of the Lindsay Formation are a result of the combined effects of paleotopography, a high relief rocky shoreline, and differential compaction.

Analysis of the main nuclear-physical characteristics of the interaction of proton beams with heavy metal targets

It is shown that the concept of relativistic heavy-nuclear energy is untenable. Using a large group of different experiments in the proton energy range 0.25–70 GeV, it is demonstrated that the high-energy hadron transport program SHIELD, which is based on modern nuclear models, has predictive power. The interaction of protons with energy ranging from 0.1 to 100 GeV with a simple model system target + blanket, containing heavy elements (lead, thorium, depleted and enriched uranium), is examined. The energy release, neutron production, and production of fissile isotopes in the system are calculated. It is found that for all values of the proton energy which are considered the useful yield of energy in weakly fissile media is inadequate (thorium, depleted uranium) and is completely absent in non-fissile media (lead). A blanket containing enriched uranium will be necessary in order to use the scheme for useful production of energy. In this variant, the optimal proton energy is 1–3 GeV, which corresponds to the conventional concept of electronuclear facilities whose main purpose is to transmute nuclear wastes and produce electricity at the same time.

Monte Carlo studies in accelerator-driven systems for transmutation of high-level nuclear waste

A spallation neutron source was modeled using a high energy proton accelerator for transmutation of 239Pu, minor actinides 237Np, 241Am and long-lived fission products 99Tc, 129I, which are created from the operation of nuclear power reactors for the production of electricity. The acceleration driven system (ADS) is composed of a natural lead target, beam window, subcritical core, reflector, and structural material. The neutrons are produced by the spallation reaction of protons from a high intensity linear accelerator in the spallation target, and the fission reaction in the core. It is used a hexagonal lattice for the waste and fuel assemblies. The system is driven by a 1 GeV, 10 mA proton beam incident on a natural lead cylindrical target. The protons were uniformly distributed across the beam. The core is a cylindrical assembly. The main vessel is surrounded by a reflector made of graphite. The axes of the proton beam and the target are concentric with the main vessel axis. The structural walls and the beam window are made of the same material, stainless steel, HT9. We investigated the following neutronics parameters: spallation neutron and proton yields, spatial and energy distribution of the spallation neutrons, and protons, heat deposition, and the production rates of hydrogen and helium, transmutation rate of minor actinides and fission products. In the calculations, the Monte Carlo code MCNPX, which is a combination of LAHET and MCNP, was used. To transport a wide variety of particles, The Los Alamos High Energy Transport Code (LAHET) was used.

TH-E-M100E-05: Energy Deposition Contributions From Secondary Particles in Proton Therapy

Purpose: The purpose of this work was to evaluate the LET energy deposition contribution from primary proton particles versus the contribution of secondary particles. Method and Materials: The energy deposition contribution from primary proton particles versus contribution of secondary particles was calculated using HETC-HEDS (High Energy Transport Code for Human Exploration in Deep Space). HETC-HEDS simulates particle cascades by using Monte Carlo methods to compute the trajectories of the primary particle and all the secondary particles produced in nuclear collisions. For the initial phase of this study, the proton beam was incident on a computer model of a detector that is being designed to measure the LET spectra for proton beams. Simulations were performed using incident proton beams between 90 and 200 MeV/Nucleon in 5 MeV/Nucleon increments incident on 10 g/cm2 of A-150 Tissue Equivalent Plastic. In the second phase, the proton beam will be incident on a computer model of an anthropomorphic RANDO phantom. Simulations will be performed for different patient treatments to determine the LET spectra of the protons and secondary particles. Results: The simulations showed that secondary particles contribution is of significance, and the contribution is about 50% of the total energy deposited into the Tissue Equivalent Plastic. Overall, the results suggested that secondary particles are of concern during proton radiation therapy treatments and need to be investigated, especially at low proton energy, and beyond the Bragg peak point. Conclusion: For proton therapy beams, the simulations presented show a significant contribution of about 50% of total energy deposition originates from secondary particles. Furthermore, a significant fraction of the fluence comes from secondary particles produced beyond the Bragg Peak. The authors are currently developing a model to incorporate the biological effect of the secondary particles in the proton treatment planning process.

Regrowth of diluted magnetic semiconductor GaMnAs on InGaP (001) surfaces to realize freestanding micromechanical structures

Low temperature molecular beam epitaxy regrowths of Ga1−xMnxAs (x≈0.04) diluted magnetic semiconductors on GaAs∕In1−yGayP∕GaAs(001) and In1−yGayP∕GaAs(001) (y≈0.51) heterostructures prepared by metal-organic chemical vapor deposition are described. The resulting Ga1−xMnxAs properties are comparable to epitaxial films grown directly on GaAs (001) substrates from in situ reflection high-energy electron diffraction, x-ray diffraction, magnetometry, and transport measurements with magnetic ordering temperature of as-grown films to range between ∼50 and ∼60K. Postgrowth low temperature annealing enhances both magnetic and transport properties. Perfect etch selectivity between Ga1−xMnxAs∕GaAs and In1−yGayP is utilized to realize suspended Ga1−xMnxAs∕GaAs doubly clamped beam micromechanical freestanding structures.

Weaving Genetically Engineered Functionality into Mechanically Robust Virus Fibers

Despite the increasing need for material multifunctionality in optical and semiconducting fibers, antimicrobial textiles, molecular-filtration membranes, and other applications, the production of functionalized fibers has posed a challenge in materials science and engineering. Here we report the design and synthesis of fibers with genetically controllable and functionalized surfaces using M13 filamentous viruses (or bacteriophages). This work applies genetic engineering, chemical conjugation, and biotemplating methods to produce continuous fibers of centimeter-scale length and micrometer-scale diameter from nanometer-scale virus scaffolds. In addition, we find the virus fibers to be mechanically comparable to synthetic homopolymer fibers. The tunable functionalities and mechanical properties of the virus fibers show the promise of these high-aspect-ratio structures as useful materials for various applications including detection, catalysis, energy storage, and power generation. Increasing demand for tuning the molecular dimensions, structures, and functionalities in nanoscience has driven the search for materials with precisely controllable properties. Fibers are currently used in energy and electronic applications to obtain high energy density, energy capacity, and transportation efficiency, which may all be further improved by using nanostructured materials. [1–4] Synthetic polymers are commonly used as fiber materials; [5,6] however, as it is difficult to

Coupling of multiple Coulomb scattering with energy loss and straggling in HZETRN

The new version of the High Charge and Energy Transport (HZETRN) deterministic transport code based on Green’s function methods, and the incorporation of ground-based laboratory boundary conditions, has lead to the development of analytical and numerical procedures to include off-axis dispersion of primary ion beams due to small-angle multiple Coulomb scattering. In this paper we present the theoretical formulation and computational procedures to compute ion beam broadening and a methodology towards achieving a self-consistent approach to coupling multiple scattering interactions with ionization energy loss and straggling. Our initial benchmark case is a 60 MeV proton beam on muscle tissue, for which we can compare various attributes of beam broadening with Monte Carlo simulations reported in the open literature.

Polyethylene as a radiation shielding standard in simulated cosmic-ray environments

Radiation risk management for human space missions depends on accurate modeling of high-energy heavy ion transport in matter. The process of nuclear fragmentation can play a key role in reducing both the physical dose and the biological effectiveness of the radiation encountered in deep space. Hydrogenous materials and light elements are expected to be more effective shields against the deleterious effects of galactic cosmic rays (GCR) than aluminum, which is used in current spacecraft hulls. NASA has chosen polyethylene, CH2, as the reference material for accelerator-based radiation testing of multi-function composites that are currently being developed. A detailed discussion of the shielding properties of polyethylene under a variety of relevant experimental conditions is presented, along with Monte Carlo simulations of the experiments and other Monte Carlo calculations in which the entire GCR flux is simulated. The Monte Carlo results are compared to the accelerator data and we assess the usefulness of 1GeV/amu 56Fe as a proxy for GCR heavy ions. We conclude that additional accelerator-based measurements with higher beam energies would be useful.

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Schemes to produce intense sources of high-energy muons, Neutrino Factories, beta beams, and colliders, require collection, rf capture, and transport of particle beams with unprecedented emittances, both longitudinally and transversely. These large initial emittances must be reduced or cooled both in size and in energy spread before the muons can be efficiently accelerated to multi-GeV energies. The acceleration stage becomes critical in formulating and optimizing muon beams; individual stages are strongly interlinked and not independent as is the case in most conventional acceleration systems. Most importantly, the degree of cooling, or cooling channel, depends on the choice of acceleration. This work discusses two basic, but different approaches to a Neutrino Factory and how the optimal strategy depends on beam parameters and method of acceleration.

What's in a beach? Soil micromorphology of sediments from the Lower Paleolithic site of ‘Ubeidiya, Israel

A micromorphological study of archaeological sediments from the early Pleistocene site of ‘Ubeidiya (Jordan Valley, Israel) was conducted to provide microenvironmental detail for the hominin occupation contexts and investigate site formation issues. Previous research shows that the hominin groups occupied the marshes and pebbly beaches at the shores of a lake during a regressive period, but given that some portions of the lithic and faunal assemblages are abraded and others fresh, there remains a question of whether the archaeological assemblages are in situ or reworked, and if reworked, by what mechanisms and from where. The rates of sedimentation within the regressive cycle, by which we can learn about the frequency and duration of exposed surfaces amenable for hominin occupation is also unknown. Finally, the artificial nature of some of the pebbly layers has been questioned. The micromorphological analysis yielded the identification of twelve microfacies; the majority of these represent fluvially derived floodplain soils or distal mudflow deposits, and a minor number are sediments of lacustrine origin: mudflats and shallow subaqueous sediments. These represent the natural habitats of the ‘Ubeidiya hominins and might serve as a reference to similar contexts of other early hominin sites. The sedimentary model proposed here entails the rapid deposition of fluvially derived low-energy sediments at and around the shoreline, followed by prolonged periods of exposure, during which surfaces stabilized within a relatively wet, marshy environment. This interpretation suggests that the abraded portions of the archaeological assemblages are a result of prolonged surface exposure rather than high-energy transport from a distant source or to wave reworking at the shoreline, and supports the consideration of these assemblages as archaeological palimpsests, with locally reworked fresh and abraded elements. No micromorphological evidence supporting anthropogenic agency in the formation of the pebbly layers was found. The entire regressive cycle entailed unvarying climatic conditions with seasonal fluctuations and episodic lacustrine incursions, and with a trend towards arid conditions in the end.

Radiation Shielding Analysis for Various Materials in the Extreme Jovian Environment

ABSTRACTEarlier particle experiments in the 1970s on Pioneer-10 and -11 and Voyager-1 and -2 provided Jupiter flyby particle data, which were used by Divine and Garrett to develop the first Jupiter trapped radiation environment model. This model was used to establish a baseline radiation effects design limit for the Galileo onboard electronics. Recently, Garrett et al. have developed an updated Galileo Interim Radiation Environment (GIRE) model based on Galileo electron data. In this paper, the GIRE model was utilized to generate trapped proton and electron spectra as a function of Rj (Rj = radius of Jupiter = ∼71,400 km). Using these spectra and a high-energy particle transport codes (MCNPX and HZETRN), radiation exposures and dose effects for a variety of shielding materials (Al, polyethylene [PE], and Ta plus several other elemental materials for “Graded-Z” portion of the paper) and thicknesses are presented for the Icy Moon, Europa, Ganymede, and Callisto for several orbital inclinations. In addition, an in-depth discussion and absorbed dose calculations are presented for “Graded-Z” materials and several computer codes were utilized for comparison purposes. We find overall there is generally quite good agreement between the various computer codes utilized in the study: MCNPX (Monte Carlo) vs. HZETRN (deterministic) for slab shielding and the comparison of “Graded-Z” shielding using the CEPXS, NOVICE, and NASA JPL codes. Finally, we conclude that the merits of using “Graded-Z” materials that include PE, due to cost and weight, should aid future Jupiter mission planners and spacecraft designers.