Light-ion Production Research Articles

DDFRG2: Double-Differential FRaGmentation model for pion production in high energy nuclear collisions

A set of Double-Differential FRaGmentation (DDFRG) models for production of fragments from nucleon–nucleus and nucleus–nucleus collisions, relevant to space radiation, is currently being developed. DDFRG1 was a previous model developed for production of protons and light ions. A new model for pion production is developed in the present work and is called DDFRG2, which is based upon thermal production of pions from a central fireball source. The Lorentz-invariant double-differential cross section is calculated in the central fireball frame, and is Lorentz transformed to the laboratory frame, which results in a closed-form analytic formula involving no numerical integration, and which can be run very efficiently in radiation transport codes. The Lorentz-invariant double-differential cross section is then integrated over angle to give the single-differential energy spectral distribution. The calculated Lorentz-invariant double-differential cross sections are compared to an extensive data set containing over 1000 data points. Agreement between model calculations and data is found to be excellent.

A multi-detector experimental setup for the study of space radiation shielding materials: Measurement of secondary radiation behind thick shielding and assessment of its radiobiological effect

Space agencies have recognized the risks of astronauts’ exposure to space radiation and are developing complex model-based risk mitigation strategies. In the foundation of these models, there are still significant gaps of knowledge concerning nuclear fragmentation reactions which need to be addressed by ground-based experiments. There is a lack of data on neutron and light ion production by heavy ions, which are an important component of galactic cosmic radiation (GCR). A research collaboration has been set up to characterize the secondary radiation field produced by GCR-like radiation provided by a particle accelerator in thick shielding. The aim is to develop a novel method for producing high-quality experimental data on neutron and light ion production in shielding materials relevant for space radiation protection. Four complementary detector systems are used to determine the energy and angular distributions of high-energy secondary neutrons and light ions. In addition to the physical measurement approach, the biological effectiveness of the secondary radiation field is determined by measuring chromosome aberrations in human peripheral lymphocytes placed behind the shielding. The experiments are performed at the heavy ion

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.

Design study of compact EBIS for light-ion production using low-energy hollow electron beams

A new compact electron-beam ion source (EBIS) with a low-energy hollow electron beam has been designed to produce ions for use in heavy-ion therapy. Numerical analyses of the electron beam using the three-dimensional particle-in-cell method determine the appropriate shape of the inner electrodes to realize a compact size and a sufficient number of confined ions for heavy-ion therapy. The analyses also show that the undesirable instability of the hollow electron beam is mitigated by the reflection mode with an electron repeller. Experimental tests were performed on the assembled EBIS to assess the validity of its design. The results of an electron-beam test show that the electrodes have been designed appropriately. Additionally, the results of an ion-beam test show that ions can be produced and confined in the newly developed compact EBIS and the number of extracted ions is just shy of the target value, showing the prospects of modifications aimed at realizing a compact EBIS specialized for the production of ions used in heavy-ion therapy.

Double-Differential FRaGmentation (DDFRG) models for proton and light ion production in high energy nuclear collisions

A new set of Double-Differential FRaGmentation (DDFRG) models for proton and light ion production from high energy nucleus–nucleus collisions, relevant to space radiation, is introduced. The proton model employs thermal production from the projectile, central fireball and target sources, as well as quasi-elastic direct knockout production. The light ion model uses a hybrid coalescence model. The data show a prominent quasi-elastic peak at small angles which becomes highly suppressed at large angles. The models are able to describe this wide range of experimental data with only a limited set of model parameters. Closed form analytic formulas for double-differential energy and angle cross-sections as well as single-differential spectral cross-sections are developed. These analytic formulas enable highly efficient computation for radiation transport codes.

HZETRN radiation transport validation using balloon-based experimental data

The deterministic radiation transport code HZETRN (High charge (Z) and Energy TRaNsport) was developed by NASA to study the effects of cosmic radiation on astronauts and instrumentation shielded by various materials. This work presents an analysis of computed differential flux from HZETRN compared with measurement data from three balloon-based experiments over a range of atmospheric depths, particle types, and energies. Model uncertainties were quantified using an interval-based validation metric that takes into account measurement uncertainty both in the flux and the energy at which it was measured. Average uncertainty metrics were computed for the entire dataset as well as subsets of the measurements (by experiment, particle type, energy, etc.) to reveal any specific trends of systematic over- or under-prediction by HZETRN. The distribution of individual model uncertainties was also investigated to study the range and dispersion of errors beyond just single scalar and interval metrics.The differential fluxes from HZETRN were generally well-correlated with balloon-based measurements; the median relative model difference across the entire dataset was determined to be 30%. The distribution of model uncertainties, however, revealed that the range of errors was relatively broad, with approximately 30% of the uncertainties exceeding ± 40%. The distribution also indicated that HZETRN systematically under-predicts the measurement dataset as a whole, with approximately 80% of the relative uncertainties having negative values. Instances of systematic bias for subsets of the data were also observed, including a significant underestimation of alpha particles and protons for energies below 2.5 GeV/u. Muons were found to be systematically over-predicted at atmospheric depths deeper than 50 g/cm2 but under-predicted for shallower depths. Furthermore, a systematic under-prediction of alpha particles and protons was observed below the geomagnetic cutoff, suggesting that improvements to the light ion production cross sections in HZETRN should be investigated.

Designing an upgrade of the Medley setup for light-ion production and fission cross-section measurements

Measurements of neutron-induced fission cross-sections and light-ion production are planned in the energy range 1–40MeV at the upcoming Neutrons For Science (NFS) facility. In order to prepare our detector setup for the neutron beam with continuous energy spectrum, a simulation software was written using the Geant4 toolkit for both measurement situations. The neutron energy range around 20MeV is troublesome when it comes to the cross-sections used by Geant4 since data-driven cross-sections are only available below 20MeV but not above, where they are based on semi-empirical models. Several customisations were made to the standard classes in Geant4 in order to produce consistent results over the whole simulated energy range.Expected uncertainties are reported for both types of measurements. The simulations have shown that a simultaneous precision measurement of the three standard cross-sections H(n,n), 235U(n,f) and 238U(n,f) relative to each other is feasible using a triple layered target. As high resolution timing detectors for fission fragments we plan to use Parallel Plate Avalanche Counters (PPACs). The simulation results have put some restrictions on the design of these detectors as well as on the target design. This study suggests a fissile target no thicker than 2μm (1.7mg/cm2) and a PPAC foil thickness preferably less than 1μm. We also comment on the usability of Geant4 for simulation studies of neutron reactions in this energy range.

Measuring Light-ion Production and Fission Cross Sections Normalised to H(n,p) Scattering at the Upcoming NFS Facility

The Medley detector setup is planned to be moved to and used at the new neutron facility NFS where measurements of light-ion production and fission cross-sections are planned at 1-40 MeV. Medley has eight detector telescopes providing ΔE-ΔE-E data, each consisting of two silicon detectors and a CsI(Tl) detector at the back. The telescope setup can be rotated and arranged to cover any angle. Medley has previously been used in many measurements at The Svedberg Laboratory (TSL) in Uppsala mainly with a quasi-mono-energetic neutron beam at 96 and 175 MeV. To be able to do measurements at NFS, which will have a white neutron beam, Medley needs to detect the reaction products with a high timing resolution providing the ToF of the primary neutron. In this paper we discuss the design of the Medley upgrade along with simulations of the setup. We explore the use of Parallel Plate Avalanche Counters (PPACs) which work very well for detecting fission fragments but require more consideration for detecting deeply penetrating particles.

Light-ion Production in 175 MeV Neutron-induced Reactions on Oxygen

We have measured double-differential cross sections for 175 MeV quasi-monoenergetic neutrons on oxygen. The detector setup used in MEDLEY consists of eight Si-Si-CsI telescopes designed to detect light ions (up to A=4), with a low-energy threshold and over an angular domain ranging from 20∘ to 160∘, in steps of 20∘. The ΔE−E technique is used to identify the light ions. Suppression of events induced by neutrons in the low-energy tail of the neutron field is achieved by time-of-flight techniques. The data are normalised relative to elastic np scattering measured in one of the telescopes at 20∘. We present preliminary double-differential production cross sections for protons, deuterons and α particles and compare them with theoretical reaction model calculations.

Light-ion Production from O, Si, Fe and Bi Induced by 175 MeV Quasi-monoenergetic Neutrons

We have measured double-differential cross sections in the interaction of 175 MeV quasi-monoenergetic neutrons with O, Si, Fe and Bi. We have compared these results with model calculations with INCL4.5-Abla07, MCNP6 and TALYS-1.2. We have also compared our data with PHITS calculations, where the pre-equilibrium stage of the reaction was accounted respectively using the JENDL/HE-2007 evaluated data library, the quantum molecular dynamics model (QMD) and a modified version of QMD (MQMD) to include a surface coalescence model. The most crucial aspect is the formation and emission of composite particles in the pre-equilibrium stage.

Light ion production in 175 MeV quasi mono-energetic neutron induced reactions on carbon, oxygen, and silicon

Double-differential cross sections of light ions (p, d, t, 3 He, and α) from carbon, oxygen, and silicon induced by 175 MeV quasi mono-energetic neutrons were measured using the Medley setup at the The Svedberg Laboratory (TSL) in order to benchmark evaluated nuclear data and nuclear reaction models. The Medley is a conventional spectrometer system which consists of eight counter telescopes. Each telescope is composed of two silicon surface barrier detectors as the ΔE detectors and a CsI(Tl) scintillator as the E detector for particle identification. The telescopes are placed at angles from 20° to 160° in steps of 20°. The measured double-differential production cross sections of light ions for oxygen and silicon are compared with PHITS calculations using the following nuclear reaction options: the high-energy nuclear data library (JENDL/HE-2007), the quantum molecular dynamics (QMD) model, the modified quantum molecular dynamics (MQMD) model, and the intra-nuclear cascade (INC) model based on the Bertini Model.

Light-ion production in 175 MeV quasi-monoenergetic neutron-induced reactions on iron and bismuth and comparison with INCL4 calculations

Nuclear data for neutron-induced reactions in the intermediate energy range of 20 to 200 MeV are of importance for several different applications, notably accelerator-driven incineration of nuclear waste. The Medley setup located at The Svedberg Laboratory in Uppsala, Sweden was used for a series of measurements of p, d, t, 3 He and alpha particle production from 175 MeV neutrons on various target nuclei. Medley uses an arrangement of 8 detector telescopes placed at angles from 20 to 160 degrees relative to the neutron beam to register event and discriminate among the particle types. Using the ΔE-ΔE-E technique we were able to measure double-differential cross sections over a wide dynamic range. This paper describes the experimental set-up, summarizes the data analysis and reports on recent changes in the previously reported preliminary data set on bismuth. Experimental data are compared with several different model calculations. In this paper we specifically compare the experimental results with INCL4 intra-nuclear cascade calculations combined with the ABLA de-excitation code. Considering the fact that the experimental data are obtained at an energy normally considered too low for intra-nuclear cascade calculations, we do find some systematic difference but generally reasonable agreement.

Light ion production for a future radiobiological facility at CERN: Preliminary studies

Recent medical applications of ions such as carbon and helium have proved extremely effective for the treatment of human patients. However, before now a comprehensive study of the effects of different light ions on organic targets has not been completed. There is a strong desire for a dedicated facility which can produce ions in the range of protons to neon in order to perform this study. This paper will present the proposal and preliminary investigations into the production of light ions, and the development of a radiobiological research facility at CERN. The aims of this project will be presented along with the modifications required to the existing linear accelerator (Linac3), and the foreseen facility, including the requirements for an ion source in terms of some of the specification parameters and the flexibility of operation for different ion types. Preliminary results from beam transport simulations will be presented, in addition to some planned tests required to produce some of the required light ions (lithium, boron) to be conducted in collaboration with the Helmholtz-Zentrum für Materialien und Energie, Berlin.

Light ion and multiple nucleon removal due to electromagnetic dissociation

Light ion (H and He isotopes) and neutron production in galactic cosmic ray interactions are important for space radiation analyses. They occur via strong or electromagnetic dissociation (EMD) interactions. A parameterization for single nucleon, multiple nucleon and light ion production in EMD is developed in this paper. It supersedes the previous work in the following ways. Firstly, the calculations are compared to a more extensive set of experimental data. Secondly, EMD calculations for alpha particle production are in better agreement with experiment. Thirdly, a parameterization of multiple nucleon removal is developed and compared to data. Overall, the present work includes more reactions and compares better to experimental data than previous work.

Comparison of models of neutron and residue production in targets heavy elements irradiated by relativistic proton and deuteron beams

The improvement of both the precision of the nuclear models and the Monte Carlo transport requires a comparison of the simulated productions of residues, the spallation of neutrons and their transport, obtained in different scenarios. The calculations of the residue production and corresponding neutron double differential cross sections are performed using the different reaction models in the MCNPX 27d transport code. The aim of this study was to validate the calculation of nuclear spallation by using the latest version of MCNPX code and comparing the results of calculations with experimental data from GSI Darmstadt. This work focuses in particular on the study of generation of residue in uranium and lead during interactions of protons and deuterons. The cross sections of production of light ions and isotopes as a function of mass and atomic number during the impact of protons and deuterons of energy of 1 GeV/nuc. with the uranium and lead was also calculated. Finally the results of calculations obtained by different methods were compared with known experimental data.

NUCFRG3: Light ion improvements to the nuclear fragmentation model

Light ion improvements to the nuclear fragmentation model, NUCFRG, are reported. Improvements include the replacement of the simple light ion production model with a light ion coalescence model and an improved electromagnetic dissociation (EMD) formalism. Prior versions of the model provide reasonable overall agreement with measured data; however, those versions lack a physics-based description for coalescence and EMD. The version reported herein, NUCFRG3, has improved the theoretical descriptions of these mechanisms and offers additional benefits, such as the capability to calculate EMD cross-sections for single deuteron, triton, helion, and alpha particle emission. NUCFRG3 model evaluation and validation show that the predictive capability has been improved and strengthened by the light ion physics-based changes. Based on increased capability and better theoretical grounding, it is recommended that NUCFRG3 replace its predecessors for space radiation assessments and other applications.

Validation of nuclear reaction models relevant to cosmic-ray neutron induced single-event effects in microelectronics

The accuracy of nuclear reaction models used in the PHITS (Particle and Heavy Ion Transport code System) code, i.e., the INC model, the QMD model and the event generator mode (e-mode) with the evaluated nuclear data library JENDL-3.3 are validated to apply it to the simulations on single-event effects in advanced microelectronic devices. The model calculations are compared with available experimental data of light-ion production (i.e., proton and alpha particle) from neutron-induced reactions on natSi and 16O, which are the major constituent elements of silicon semiconductor devices over the wide energy range. Comparisons of calculated and measured data for light-ion production indicate that the e-mode calculation with JENDL-3.3 provides better agreement with the experimental data below 20 MeV, and the QMD model reproduces them reasonably well at energies larger than 20 MeV.

Light-Ion Production in 175 MeV Neutron-Induced Reactions on Oxygen

Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron be ...

Light-Ion Production in The Interaction of 175 MeV Neutrons with Iron and Bismuth

We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, (3)He, and a) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20 degrees to 160 degrees, in steps of 20 degrees. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification, fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, (3)He and alpha particles and compare them with model calculations with TALYS-1.2.

Light-Ion Production from a Thin Silicon Target Bombarded by 175 MeV Quasi Monoenergetic Neutrons

Double-differential production yields of light ions (p, d, t, (3)He, and alpha) from a thin silicon target induced by 175 MeV quasi mono-energetic neutrons were measured using the MEDLEY setup at t ...