Fragmentation Cross Sections Research Articles

Fragmentation of stable and neutron-rich 12-16C into boron fragments at approximately 240 MeV/nucleon * *Supported by the National Natural Science Foundation of China (U1732134, U1832205), the Heavy Ion Research Facility in Lanzhou (HIRFL), and the open research project of CAS large research infrastructures

The elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich 12-16C beams with a carbon target were systematically measured at an incident beam energy of approximately 240 MeV/nucleon. The measured cross sections were found to increase as the projectile mass number increases. The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models, including empirical and statistical models. All models agree with the measured cross sections within a factor of 2.

Correlating whole sample EDS and Raman mappings – A case study of a Chelyabinsk meteorite fragment

Whole sample microscopy mappings are of interest in many cases as they provide analytical information of phases varying in size by orders of magnitude and in composition across the sample. These benefits are amplified if more than one microscopic technique is used for the mappings. However, to take full advantage of correlative whole sample mappings, the data of each technique has to be carefully prepared, treated, correlated and evaluated. With this work, we want to present the key steps of our data treatment approach as well as the results on an exemplary sample, the Chelyabinsk meteorite.The most important step in our data treatment approach is to start by evaluating the spectral maps separately as far as possible (at-% quantification for EDS for example) and then generate pseudo spectral maps from this evaluation in the form of image stacks. This allows us to preserve the advantages of specialized software packages and standard work flows for every spectral mapping, whilst also unifying the data format and compressing the data sufficiently for correlation and the application of machine learning tools.We have performed whole sample mappings using SEM, EDS and Raman on a cross-section of a Chelyabinsk meteorite fragment, roughly 1.0cm × 0.8cm large. Combining these mappings into a single “super” spectral map, we were able to produce a uniquely detailed mapping of the composition of the meteorite fragment, as well as perform a quantitative analysis of the elemental composition of several crystallographic phases. The results of our compositional analysis; olivine (Fo72Fa28), pyroxene (≈ 97 % En80Fs20Wo0 and 3 % En56Fs6Wo38), feldspar (albite), troilite, FeNi (taenite and kamacite), merrillite, chromite and hydroxyapatite; agree qualitatively with other reports from literature.

Applicability of composite materials for space radiation shielding of spacecraft

Energetic ion beam experiments with major space radiation elements, 1H, 4He, 16O, 28Si and 56Fe, have been conducted to investigate the radiation shielding properties of composite materials. These materials are expected to be used for parts and fixtures of space vehicles due to both their mechanical strength and their space radiation shielding capabilities. Low Z materials containing hydrogen are effective for shielding protons and heavy ions due to their high stopping power and large fragmentation cross section per unit mass. The stopping power of the composite materials used in this work is intermediate between that of aluminum and polyethylene, which are typical structural and shielding materials used in space. The total charge-changing cross sections per unit mass, σUM, of the composite materials are 1.3–1.8 times larger than that of aluminum. By replacing conventional aluminum used for spacecraft with commercially available composite (carbon fiber / polyether ether ketone), it is expected that the shielding effect is increased by ∼17%. The utilization of composite materials will help mitigate the space radiation hazard on future deep space missions.

Enhancing the understanding of fragmentation processes in hadrontherapy and radioprotection in space with the FOOT experiment

During proton and carbon ions cancer treatment, nuclear interactions of the beam nuclei with the patient tissues always occur: the former leads to target fragmentation only, the latter to both projectile and target fragments production. In proton therapy the low-energy, high-charge and therefore short-range fragments produced along the beam path in the target fragmentation process may have higher biological effectiveness compared to protons, resulting in a not negligible effect on the delivered dose in a region before the tumor site. In carbon treatments the long range of projectile fragments results in a dose deposition in the healthy tissues behind the tumor site. Therefore, precise fragmentation cross section data would be of great importance to further optimize treatments. At the same time, such data would help improving the design of the shielding of spaceships, especially in view of long distance travels (i.e. Mars human exploration). In fact, nuclear fragmentation occurring between the space background radiation and spacecrafts materials changes the composition of the radiation field and thus the dose received by the astronauts. The FOOT (FragmentatiOn Of Target) experiment has been designed to investigate nuclear fragmentation processes of interest for particle therapy and space radiation protection with a precision in the cross section measurements around 5%. In this work the physics motivations of FOOT and the final design of the experiment will be presented. A performances study of the electronic setup based on FLUKA Monte Carlo simulations and a preliminary analysis of experimental data are reported as well.

Relativistic Abrasion–Ablation De-excitation Fragmentation (RAADFRG) model

Astronauts are exposed to ionizing radiation that may pose significant health risks from missions to low Earth orbit (LEO) and beyond. The National Aeronautics and Space Administration (NASA) uses the deterministic radiation transport code, High charge (Z) and Energy TRaNsport (HZETRN), to estimate particle fluxes inside shielded vehicles to evaluate risk of radiation exposure to crew members. Highly efficient radiation transport algorithms and cross section models are needed to perform calculations in realistic vehicles with complex geometrical configurations. The HZETRN code uses the NUClear FRaGmentation (NUCFRG) model to evaluate fragmentation cross section products from nucleus–nucleus collisions. Although highly efficient, the NUCFRG model has some limitations that are based on its unique implementation of the abrasion–ablation formalism. NUCFRG performs well in predicting fragmentation cross sections on the average when compared to experimental data; however, even–odd nuclear structure effects observed in laboratory measurements are absent. The aim of the present work is to formulate a self-consistent theory that produces accurate nuclear fragmentation cross sections while maintaining numerical efficiency. To that end, the Relativistic Abrasion–Ablation FRaGmentation (RAADFRG) model has been developed. The theoretical framework for nuclear interaction is multiple scattering theory (MST), where relativistic kinematics may be included in the momentum–space representation of the Lippmann–Schwinger equation. The nuclear abrasion model employs the Eikonal (Eik) approximation and is used to predict prefragment cross sections. A novel approach is utilized for the excitation energy of prefragment, where in addition to differences of binding energies between two nuclei, energy is transferred to the prefragment from subsequent multiple scattering of abraded nucleons with the spectator nucleon constituents of the prefragment. Next, the excited prefragment liberates particles through the nuclear ablation process, and a nuclear coalescence model that forms aggregate particles for each prefragment channel is included in the yield. The ElectroMagnetic Dissociation FRaGmentation (EMDFRG) model is also included for peripheral interactions that stimulates particle emission via nuclear-photon field interactions. When compared to NUCFRG3, uncertainty quantification analysis shows that RAADFRG is better able to predict experimental nuclear fragmentation cross sections. RAADFRG is also shown to produce the even–odd nuclear structure effects, which is achieved by modification of isospin pairing correction in the prefragment excitation energy model.

Fragmentation of carbon on elemental targets at 290AMeV

The total charge-changing cross-sections and the partial cross-sections for projectile fragments (PFs) production for the fragmentation of 12C on C, Al, Cu, Pb and CH2 targets at the highest energy of 290[Formula: see text]A[Formula: see text]MeV were studied. It was found that the total charge-changing reaction cross-sections and the partial reaction cross-sections of PFs production were independent of the beam energy, and increased with increase of mass of target for the same beam energy. The total charge-changing reaction cross-section was the same as the prediction of Bradt–Peters semi-empirical formula, PHITS and NUCFRG2 simulation models. The partial cross-section of PFs production increased with the increase of the mass of target, and it was the same as the prediction of NUCFRG2 models. The mean scattering angle of projectile particle was smaller than the average emission angle of PF, and the width of scattering angle distribution of projectile particle was smaller than that of emission angle distribution of PFs. The mean emission angle of PFs does not obviously depend on the target mass and beam energy in our studied beam energy regions.

20Ne ion range and fragmentation cross-sections in various targets for space shielding and hadrontherapy applications: A Monte Carlo simulation study

The computational study of projectile range and partial fragmentation cross-section (PFXS) has been executed for 20Ne ion using Geant4 Monte Carlo simulation toolkit. The interaction of heavy semi-symmetric system for energy range 290 MeV/n−670 MeV/n has been researched on various targets: carbon (C), aluminium (Al), copper (Cu), tin (Sn), lead (Pb), and tantalum (Ta). The range simulated via Geant4 and SRIM software shows an agreement of ~ 99%. The PFXS simulation has been conducted using three models of Geant4: the Binary Cascade (BIC), Liege Intranuclear cascade (INCL++), and Quantum Molecular Dynamics (QMD). The PFXS is computed for heavy (Z = 5–9) and light (Z = 2–4) fragments. These models have been validated by analysing simulation data with experimental and semi-empirical nuclear fragmentation model data. The QMD model provides the best data for PFXS following an odd–even effect for all targets. The BIC and the INCL++ behave in similar manner for high Z target.

The Discovery of a Low-energy Excess in Cosmic-Ray Iron: Evidence of the Past Supernova Activity in the Local Bubble.

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species ( , e ±, and nuclei, 1H-8O, 10Ne, 12Mg, 14Si) which resulted in a number of breakthroughs. One of the latest long-awaited surprises is the spectrum of 26Fe just published by AMS-02. Because of the large fragmentation cross section and large ionization energy losses, most of CR iron at low energies is local and may harbor some features associated with relatively recent supernova (SN) activity in the solar neighborhood. Our analysis of the new AMS-02 results, together with Voyager 1 and ACE-CRIS data, reveals an unexpected bump in the iron spectrum and in the Fe/He, Fe/O, and Fe/Si ratios at 1-2 GV, while a similar feature in the spectra of He, O, and Si and in their ratios is absent, hinting at a local source of low-energy CRs. The found excess extends the recent discoveries of radioactive 60Fe deposits in terrestrial and lunar samples and in CRs. We provide an updated local interstellar spectrum (LIS) of iron in the energy range from 1 MeV nucleon-1 to ~10 TeV nucleon-1. Our calculations employ the GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR , e -, and nuclei Z ⩽ 28.

Accurate odd-even staggering relations for fragmentation and spallation cross sections

Isotopic cross sections measured in many different fragmentation and spallation reactions display a universal odd-even staggering (OES). On the basis of this universality, four OES relations are proposed for the first time to accurately calculate fragmentation and spallation cross sections. Comparison with extensive experimental data measured in various reaction systems reveals that cross sections calculated by two OES relations agree excellently with 95% measured data within a factor smaller than 1.2, while another two OES relations also show a similar good agreement (within a factor around 1.5). These remarkable agreements, which can hardly be reached by other existing models, strongly support that these simple OES relations open new paths for very accurate and fast calculations of fragmentation as well as spallation cross sections. As an application of these relations, significant discrepancies between some measured cross sections are scrutinized and well resolved by using the OES magnitudes and accurate OES relations first proposed in this work. Finally, based on recent experimental data, small cross sections (down to ${10}^{\ensuremath{-}13}$ mb) of some new isotopes near the drip-lines are accurately extrapolated or interpolated with these OES relations, which will be very useful for exploring undiscovered isotopes.

Measuring the Impact of Nuclear Interaction in Particle Therapy and in Radio Protection in Space: the FOOT Experiment

In Charged Particle Therapy (PT) proton or 12C beams are used to treat deep-seated solid tumors exploiting the advantageous characteristics of charged particles energy deposition in matter. For such projectiles, the maximum of the dose is released at the end of the beam range, in the Bragg peak region, where the tumour is located. However, the nuclear interactions of the beam nuclei with the patient tissues can induce the fragmentation of projectiles and/or target nuclei and needs to be carefully taken into account when planning the treatment. In proton treatments, the target fragmentation produces low energy, short range fragments along all the beam path, that deposit a non-negligible dose especially in the first crossed tissues. On the other hand, in treatments performed using 12C, or other (4He or 16O) ions of interest, the main concern is related to the production of long range fragments that can release their dose in the healthy tissues beyond the Bragg peak. Understanding nuclear fragmentation processes is of interest also for radiation protection in human space flight applications, in view of deep space missions. In particular 4He and high-energy charged particles, mainly 12C, 16O, 28Si and 56Fe, provide the main source of absorbed dose in astronauts outside the atmosphere. The nuclear fragmentation properties of the materials used to build the spacecrafts need to be known with high accuracy in order to optimise the shielding against the space radiation. The study of the impact of these processes, which is of interest both for PT and space radioprotection applications, suffers at present from the limited experimental precision achieved on the relevant nuclear cross sections that compromise the reliability of the available computational models. The FOOT (FragmentatiOn Of Target) collaboration, composed of researchers from France, Germany, Italy and Japan, designed an experiment to study these nuclear processes and measure the corresponding fragmentation cross sections. In this work we discuss the physics motivations of FOOT, describing in detail the present detector design and the expected performances, coming from the optimization studies based on accurate FLUKA MC simulations and preliminary beam test results. The measurements planned will be also presented.

Production of neutron-rich N = 126 nuclei in multinucleon transfer reactions: Comparison between 136Xe + 198Pt and 238U + 198Pt reactions

The production cross sections for primary and residual fragments produced in two reaction systems 136Xe + 198Pt and 238U + 198Pt at incident energy 8 MeV/nucleon are calculated by improved quantum molecular dynamics (ImQMD) model incorporated with the statistical evaporation model (HIVAP code). It is found that the cross sections for n-rich N=126 residual fragments are several times larger in 238U+198Pt than in 136Xe+198Pt due to the larger cross sections and lower excitation energies of primary fragments in 238U induced reactions. In both systems, N=126 semi-magic residues are produced via neutron emission in the decay of primary fragments, which survive in the semi-central collisions and have lower excitation energies.

Geant4 systematic study of the FRACAS apparatus for hadrontherapy cross section measurements

In this work, we report on systematic Monte Carlo (MC) studies for the FRACAS apparatus, a large acceptance mass spectrometer that will be used to measure the fragmentation cross sections of 12C ions for hadrontherapy. The apparatus, placed in a 100 mbar reaction chamber, will be made of a beam monitor, trackers surrounding a magnet and a Time-Of-Flight (TOF) wall. In order to determine the required performances of the trackers, Geant4 simulations of the whole system and in-house developed algorithms were used. While keeping the beam monitor and TOF-wall positions fixed, the effects of the tracker positions and spatial resolutions on the trajectory reconstruction and mass identification efficiencies have been extracted. An optimal configuration was found where the upstream trackers should be located 6 cm away from the target and spaced 4 cm apart whereas their spatial resolutions should be close to 100 \ extmu m. The positions of the downstream trackers will have to be changed according to the beam energy to preserve high identification efficiencies. Their spatial resolutions, even though of a lesser importance compared to the upstream trackers, should be around 1 mm or better. In this optimal configuration, an overall fragment identification efficiency above 90% has been obtained for beam energies ranging from 100 to 400 MeV/nucleon.

The Irreplaceable Contribution of Cross Sections Investigation: Painted Plasters from the Sphinx Room (Domus Aurea, Rome)

Fragments and micro-fragments of painted plasters from the Sphinx Room, recently discovered in the Domus Aurea Esquiline wing (Rome, Italy), were studied. They were respectively taken from the debris in the vicinity of the walls and from already damaged edges of the decorated walls. A previous study, mainly based on non-destructive and non-invasive investigations, proved effective in giving a general overview of the employed palette, allowing the comparison with paintings from the same palace and other coeval contexts, and also providing some preliminary hints concerning the pictorial technique. Nevertheless, some issues remained unsolved, concerning the pigment mixtures (e.g., lead-/iron-based yellow to red colors; copper-/iron-based green/greyish areas), and the a fresco/a secco painting technique debate. Therefore, cross sections of the above-mentioned fragments were observed by means of Optical (OM) and Scanning Electron (SEM) Microscopy and analyzed with micro-Raman spectroscopy and Energy Dispersive X-Ray Spectroscopy (EDS), with the aims of: studying the paint layer composition through point analysis and mapping of the elemental distribution; comparing these in relation to what was observed with previously reported non-destructive analyses; studying the stratigraphy of the painted plaster, focusing on the contact between the plaster and the paint.

Performance Evaluation of the TOF-Wall Detector of the FOOT Experiment

The correct quantification of the dose released in charged particle therapy treatments requires the knowledge of the double differential fragmentation cross section of particles composing both the beam and the target. The FragmentatiOn Of Target (FOOT) experiment aims at measuring these cross sections for ions of interest for charged particle therapy applications. This article describes the performance of the time-of-flight (TOF)-wall detector of the experiment. The detector is composed of two layers of 44 cm ×2 cm ×3 mm plastic scintillator bars (20 for each layer), arranged orthogonally and read-out by silicon photomultipliers. The detector is designed to identify the charge of fragments ranging from protons to oxygen ions, with a maximum energy of 700 MeV/u, by measuring the energy released in the scintillators and the TOF with respect to a start counter. In this study, the detector was scanned with carbon ions of energy between 115 and 400 MeV/u and with a 60-MeV proton beam. The measurements show an energy resolution (σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</sub> /μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</sub> ) between 6% and 4% and a contribution of the detector to the TOF system time resolution between 25 and 20 ps (standard deviation) for carbon ions and between 100 and 80 ps for protons.

The Drift Chamber detector of the FOOT experiment: Performance analysis and external calibration

The study that we present is part of the preparation work for the setup of the FOOT (FragmentatiOn Of Target) experiment whose main goal is the measurement of the double differential cross sections of fragments produced in nuclear interactions of particles with energies relevant for particle therapy. The present work is focused on the characterization of the gas-filled drift chamber detector composed of 36 sensitive cells, distributed over two perpendicular views. Each view consists of six consecutive and staggered layers with three cells per layer. We investigated the detector efficiency and we performed an external calibration of the space–time relations at the level of single cells. This information was then used to evaluate the drift chamber resolution. An external tracking system realized with microstrip silicon detectors was adopted to have a track measurement independent on the drift chamber. The characterization was performed with a proton beam at the energies of 228 and 80 MeV. The overall hit detection efficiency of the drift chamber has been found to be 0.929±0.008, independent on the proton beam energy. The spatial resolution in the central part of the cell is about 150±10μ m and 300±10μ m and the corresponding detector angular resolution has been measured to be 1.62±0.16 mrad and 2.1±0.4 mrad for the higher and lower beam energies, respectively. In addition, the best value on the intrinsic drift chamber resolution has been evaluated to be in the range 60−100μ m. In the framework of the FOOT experiment, the drift chamber will be adopted in the pre-target region, and will be exploited to measure the projectile direction and position, as well as for the identification of pre-target fragmentation events.

Improvements to a quantum mechanical abrasion-ablation model of nuclear fragmentation: Revised nuclear level densities and improved ablation code

Transport codes used for space radiation protection require accurate nuclear fragmentation cross sections as input. The fragmentation process is modeled in two stages: a fast step, called abrasion or knockout, and a slower step, called evaporation or ablation. In this work, the ablation step is calculated via Monte Carlo (MC) methods using the recently modified legacy EVAporation (EVA) code. The code is based on the Weisskopf-Ewing particle emission formalism and has been extensively overhauled and modernized. Updates include a new nuclear mass table and modifications to the nuclear level density expression. The new formulation enables calculated results to exhibit the odd-even effect observed in experimental measurements. The revised ablation code, EVAporation-University of Tennessee, Knoxville (EVA-UTK), has been coupled with the quantum multiple scattering abrasion formalism incorporated in the nuclear fragmentation code, Optical PoTential FRAGmentation (OPTFRAG), and resulted in substantial improvements in agreement between fragmentation cross section estimates and experimental measurements.

A Bayesian-neural-network prediction for fragment production in proton induced spallation reaction * *Supported by the National Natural Science Foundation of China (U1732135, 11975091)

Fragment production in spallation reactions yields key infrastructure data for various applications. Based on the empirical SPACS parameterizations, a Bayesian-neural-network (BNN) approach is established to predict the fragment cross sections in proton-induced spallation reactions. A systematic investigation has been performed for the measured proton-induced spallation reactions of systems ranging from intermediate to heavy nuclei systems and incident energies ranging from 168 MeV/u to 1500 MeV/u. By learning the residuals between the experimental measurements and SPACS predictions, it is found that the BNN-predicted results are in good agreement with the measured results. The established method is suggested to benefit the related research on nuclear astrophysics, nuclear radioactive beam sources, accelerator driven systems, proton therapy, etc.

Threshold collision induced dissociation of pyrene cluster cations.

We report threshold collision induced dissociation experiments on cationic pyrene clusters, for sizes n = 2-6. Fragmentation cross sections are recorded as a function of the collision energy and analyzed with a statistical model. This model can account for the dissociation cascades and provides values for the dissociation energies. These values, of the order of 0.7 eV-1 eV, are in excellent agreement with those previously derived from thermal evaporation. They confirm the charge resonance stability enhancement predicted by theoretical calculations. In addition, remarkable agreement is obtained with theoretical predictions for the two smaller sizes n = 2 and 3. For the larger sizes, the agreement remains good, although the theoretical values obtained for the most stable structures are systematically higher by 0.2 eV. This offset could be attributed to approximations in the calculations. Still, there is an indication in the results of an incomplete description of the role of isomerization and/or direct dissociation upon collisions. Finally, by-product clusters containing dehydrogenated species are found to dissociate at energies comparable to the non-dehydrogenated ones, which shows no evidence for covalent bonds within the clusters.

CRL optics and silicon drift detector for P06 Microprobe experiments at 35 keV

A provisional setup for X-ray microprobe experiments at 35 keV is described. It is based on compound refractive lenses (CRLs) for nanofocusing and a Vortex silicon drift detector with 2 mm sensor thickness for increased sensitivity at high energies. The Microprobe experiment (PETRA III) generally uses Kirkpatrick-Baez mirrors for submicrometer focusing in the energy range of 5–21 keV. However, various types of scanning X-ray microscopy experiments require higher excitation energies. The CRL optics were characterized by X-ray ptychography and X-ray fluorescence (XRF) knife edge scans on a siemens star pattern and showed beam sizes down to 110 nm. The performance of the new setup for microscopic X-ray diffraction (XRD)–XRF scanning X-ray microscopy measurements at 35 keV is demonstrated on a cross-section of a painting fragment.

Source Velocity in Collisions between 3.6 GeV Protons and a Gold Target

Invariant cross sections of carbon fragments are investigated for p(3.6 GeV) + Au collisions in terms of longitudinal versus transversal velocity components. It is found that fragments are emitted by one slowly moving source.