Measurements Of Nuclear Cross Sections Research Articles

First 70Zn(p,x) nuclear cross section measurements for theranostic 67Cu radionuclide production extended up to 100 MeV

In this work the nuclear reaction routes 70Zn(p,x)64,67Cu, 66,67Ga, and 65,69mZn, induced by a high-energy proton beam up to 100 MeV have been investigated. Demand for 67Cu is increasing worldwide because it is known to be one of the best radionuclides having theranostic properties. Thus, efforts to improve its global production are underway. In previous studies, experimental data about nuclear cross-section measurements on 70Zn-enriched targets induced by proton beams were limited to an energy range of up to 70 MeV. Our goal was to extend nuclear data on 70Zn over a wider and unexplored so far region from 42 MeV to 98 MeV. As a result, our data turned out to be in good agreement with the literature ones in the overlapping energy range. In addition, to the best of our knowledge, new nuclear data exceeding 70 MeV were provided, demonstrating an excellent analytical method for producing 67Cu in the extended energy range.

Proton-induced reactions for 47Sc (and 46Sc) production: new nuclear cross section measurements on enriched titanium targets

47Sc is a theranostic radionuclide under the spotlight of the scientific community thanks to its potential for SPECT imaging and therapeutic applications. This work presents the recent measurements of proton-induced nuclear reaction cross-sections aimed at 47Sc production using enriched 48Ti, 49Ti and 50Ti targets from 23 up to 70 MeV. Since the co-production of contaminant isotopes is a key issue, and 46Sc is the main one having a longer half-life than 47Sc, the 48/49/50Ti(p,x)47Sc and 46Sc cross sections are presented and compared with the scarce literature data and TALYS estimations.

Cryomilling of Isotope-Enriched Ti Powders for HIVIPP Deposition to Manufacture Targets for Nuclear Cross Section Measurement.

The realization of isotopically enriched Ti targets for nuclear cross-section measurements requires particular attention, from the starting material preparation up to the deposition technique. In this work, a cryomilling process was developed and optimized, aimed at reducing the size of 49,50Ti metal sponge as provided by the supplier (size up to 3 mm), to the optimal size of 10 µm, to fit the High Energy Vibrational Powder Plating technique used for target manufacturing. The optimization of the cryomilling protocol and the HIVIPP deposition using natTi material was thus performed. The scarce amount of the enriched material to be treated (about 150 mg), the need to obtain a non-contaminated final powder and a uniform target thickness of about 500 µg/cm2 were taken into account. The 49,50Ti materials were then processed and 20 targets of each isotope were manufactured. Both powders and the final Ti targets produced were characterized by SEM-EDS analysis. The amount of Ti deposited was measured by weighing, indicating reproducible and homogeneous targets, with an areal density of 468 ± 110 µg/cm2 for 49Ti (n = 20) and 638 ± 200 µg/cm2 for 50Ti (n = 20). The uniformity of the deposited layer was also confirmed by the metallurgical interface analysis. The final targets were used for the cross section measurements of the 49Ti(p,x)47Sc and 50Ti(p,x)47Sc nuclear reaction routes aimed at the production of the theranostic radionuclide 47Sc.

Demonstrative measurement of proton-nuclear reaction by deconvolving the prompt gamma-ray spectra

In proton therapy, there has been an increasing demand for measuring the employed dose distribution to improve treatment accuracy and quality. One method of estimating radiation dose in real time is to visualize the prompt gamma rays emitted during nuclear reactions between protons and nuclei in the patient’s body. However, this is difficult without accurate measurements of nuclear cross sections, that cover a 10–100 MeV energy range. Herein, we propose a novel method for determining cross section of low-energy protons with 12C and 16O by measuring the prompt gamma rays emitted from stacked slab phantoms placed along the proton path. These emitted gamma rays provide direct information on the nuclear reactions occurring at different proton energies. By applying an iterative inference using the response matrix, the contamination of various prompt gamma rays can be resolved; thus, the cross sections of various reactions were obtained at arbitrary proton energies. As a first step to this study, we applied this method to measure the nuclear reaction of protons with 12C and 16O nuclei, which are the major elements constituting the human body. The cross section of the 12C(p,p)12C∗ reaction, which produces a prominent gamma-ray peak at 4.4 MeV, reproduced the one in literature well, supporting the validity of the proposed method. Furthermore, we show that even weak prompt gamma rays can be resolved for a wide range of proton energies below 70 MeV, for which no cross sectional data have been reported so far.

Effect of sample density in prompt γ-ray analysis

A high-accuracy analytical method is broadly required to obtain reliable research results. Thus, prompt γ-ray analysis (PGA), one of the most accurate non-destructive analytical methods, has been employed in various fields. However, the measurement accuracy of PGA is also known to degrade in hydrogenous samples. The degradation is caused by variation in the measurement sensitivity (counts per milligram) following the change in neutron energy due to scattering with hydrogen nucleus. Number of scatterings is well known to depend on the hydrogen content in a sample. However, considering multiple scatterings, hydrogen density, which has not been taken into account as yet, may also lead to the accuracy degradation. Here, we show the effect of the hydrogen density in PGA by evaluating the measurement sensitivity of samples with the same hydrogen content and different densities. We find that the measurement sensitivity varies by more than 30% depending on the hydrogen density even at the same hydrogen content. The variation is a particularly serious problem for PGA requiring a few percent accuracy in most cases. Additionally, although the variation is apparently observed in hydrogenous samples, the similar phenomenon can occur in other nuclides with a large scattering cross section; it may affect nuclear cross-section measurements using neutrons in such fields as astrophysics and nuclear energy.

Electrochemical co-deposition of Ni–Gd2O3 for composite thin targets preparation: Production of 155Tb as a case study

In the last years, 155Tb has attracted enormous interest due to its potential role in theranostics in nuclear medicine. To estimate its production yield, the aim of this study was to develop a method to prepare thin Gd-enriched-containing targets aimed at the 155Gd(d, 2n)155Tb nuclear cross section measurement. To this end, the electrochemical co-deposition method has been chosen to manufacture Ni–Gd2O3 composite targets. Several process parameters that have an impact on the deposit quality, have been investigated to increase the incorporation of Gd mass (up to 3 mg). To validate the concept, seven targets made by natural Gd were irradiated with deuteron beams at the GIP ARRONAX facility cyclotron, with an energy range ranging from 8 MeV to 30 MeV to extract the cross section values by using the stacked-foils method. Results obtained turned out to have great consistency with existing published data thus validating the proposed method. Therefore, an alternative target manufacturing concept aimed at cross section measurement is presented in this work.

The FragmentatiOn Of Target (FOOT) Experiment and Its DAQ System

The FragmentatiOn mymargin Of Target (FOOT) experiment aims to provide precise nuclear cross section measurements for two different fields: hadrontherapy and radio-protection in space. The main reason is the important role the nuclear fragmentation process plays in both fields, where the health risks caused by radiation are very similar and mainly attributable to the fragmentation process. The FOOT experiment has been developed in such a way that the experimental setup is easily movable and fits the space limitations of the experimental and treatment rooms available in hadrontherapy treatment centers, where most of the data takings are carried out. The trigger and data acquisition system needs to follow the same criteria and it should work in different laboratories and different conditions. It has been designed to acquire high statistics samples to fulfill the accuracy requirements of the physics analysis. Data-taking is being monitored online to allow the shift crew to verify the correct functioning of the system.

Multi-objective design optimization of a fast spectrum nuclear experiment facility using artificial intelligence

Nuclear experimental design is often a balance between competing objectives or goals for the experiment. The Fast Neutron Source (FNS) at the University of Tennessee would be a unique platform for building targeted integral nuclear cross section measurement experiments to reduce nuclear data uncertainty on future reactor designs. In this paper we apply a genetic algorithm using non-dominated sorting, elitism, and crowding distance heuristics to explore the design space of a simplified 1D approximation of the FNS, and from this data, we present correlations in the final suite of designs which will be the basis of heuristics for more complex optimizations and geometries in the future. In this analysis, we show that a multi-objective genetic algorithm can be used to design nuclear experiments with the dual objective of spectrum matching and flux maximization.

HIVIPP deposition and characterization of isotopically enriched 48Ti targets for nuclear cross-section measurements

Thin targets of isotopically enriched 48Ti metallic powder on Al foil substrates for the nuclear cross-section measurements were manufactured using the HIgh energy VIbrational Powders Plating method in vacuum. The target areal thickness of 0.2–2 mg/cm2 was achieved as measured by weighing as well as by Elastic Backscattering Spectroscopy (EBS) analysis. The quality of the targets, in particular the deposit uniformity, was evaluated by Scanning Electron Microscope (SEM) assisted by the Energy Dispersive Spectroscopy (EDS). The microstructure of the HIVIPP deposited targets was analyzed for the first time. SEM analysis showed that the coating microstructure was strongly related to the original powder microstructure. It was also observed that the coating was not a powder monolayer. The smaller powder particles, which were the first to move in the electric field, remained attached to the substrate and created the first layers of the deposit. Further layers of bigger particles were then attached to the first layer. The information about the deposit microstructure was utilized to model the EBS analysis results. The subset of the prepared 48Ti enriched targets was successfully used for the nuclear cross-section measurement campaign up to 40 MeV using the proton beam (115 nA) available at the C70 cyclotron in ARRONAX (Nantes, France).

Scrutinizing the evidence for dark matter in cosmic-ray antiprotons

Global fits of primary and secondary cosmic-ray (CR) fluxes measured by AMS-02 have great potential to study CR propagation models and search for exotic sources of antimatter such as annihilating dark matter (DM). Previous studies of AMS-02 antiprotons revealed a possible hint for a DM signal which, however, could be affected by systematic uncertainties. To test the robustness of such a DM signal, in this work we systematically study two important sources of uncertainties: the antiproton production cross sections needed to calculate the source spectra of secondary antiprotons and the potential correlations in the experimental data, so far not provided by the AMS-02 Collaboration. To investigate the impact of cross-section uncertainties we perform global fits of CR spectra including a covariance matrix determined from nuclear cross-section measurements. As an alternative approach, we perform a joint fit to both the CR and cross-section data. The two methods agree and show that cross-section uncertainties have a small effect on the CR fits and on the significance of a potential DM signal, which we find to be at the level of $3\sigma$. Correlations in the data can have a much larger impact. To illustrate this effect, we determine possible benchmark models for the correlations in a data-driven method. The inclusion of correlations strongly improves the constraints on the propagation model and, furthermore, enhances the significance of the DM signal up to above $5\sigma$. Our analysis demonstrates the importance of providing the covariance of the experimental data, which is needed to fully exploit their potential.

Astrophysical neutrino production and impact of associated uncertainties in photo-hadronic interactions of UHECRs

High energy neutrinos can be produced by interactions of ultra-high energy cosmic rays (UHECRs) in the dense radiation fields of their sources as well as off the cosmic backgrounds when they propagate through the universe. Multi-messenger interpretations of current measurements deeply rely on the understanding of these interactions. In order to efficiently produce neutrinos in the sources of UHECRs, at least a moderate level of interactions is needed, which means that a nuclear cascade develops if nuclei are involved. On the other hand, the available cross-section data and interaction models turn out to make poor predictions for most nuclei heavier than protons. We show the impact of these uncertainties in state-of-the-art photo-disintegration models and motivate nuclear cross-section measurements. Further, we discuss extensions for photo-meson models currently used in astrophysics and demonstrate the importance of understanding the details of UHECR interaction with the Glashow resonance.

Direct measurement of nuclear cross-section of astrophysical interest: Results and perspectives

Stellar evolution and nucleosynthesis are interconnected by a wide network of nuclear reactions: the study of such connection is usually known as nuclear astrophysics. The main task of this discipline is the determination of nuclear cross-section and hence of the reaction rate in different scenarios, i.e. from the synthesis of a few very light isotopes just after the Big Bang to the heavy element production in the violent explosive end of massive stars. The experimental determination of reaction cross-section at the astrophysical relevant energies is extremely difficult, sometime impossible, due to the Coulomb repulsion between the interacting nuclei which turns out in cross-section values down to the fbar level. To overcome these obstacles, several experimental approaches have been developed and the adopted techniques can be roughly divided into two categories, i.e. direct and indirect methods. In this review paper, the general problem of nuclear astrophysics is introduced and discussed from the point of view of experimental approach. We focus on direct methods and in particular on the features of low-background experiments performed at underground laboratory facilities. The present knowledge of reactions involved in the Big Bang and stellar hydrogen-burning scenarios is discussed as well as the ongoing projects aiming to investigate mainly the helium- and carbon-burning phases. Worldwide, a new generation of experiment in the MeV range is in the design phase or at the very first steps and decisive progresses are expected to come in the next years.

Measurement of nuclear reaction cross sections by using Cherenkov radiation toward high-precision proton therapy

Monitoring the in vivo dose distribution in proton therapy is desirable for the accurate irradiation of a tumor. Although positron emission tomography (PET) is widely used for confirmation, the obtained distribution of positron emitters produced by the protons does not trace the dose distribution due to the different physical processes. To estimate the accurate dose from the PET image, the cross sections of nuclear reactions that produce positron emitters are important yet far from being sufficient. In this study, we measured the cross sections of 16O(p,x)15O, 16O(p,x)13N, and 16O(p,x)11C with a wide-energy range (approximately 5–70 MeV) by observing the temporal evolution of the Cherenkov radiation emitted from positrons generated via β+ decay along the proton path. Furthermore, we implemented the new cross sectional data into a conventional Monte Carlo (MC) simulation, so that a direct comparison was possible with the PET measurement. We confirmed that our MC results showed good agreement with the experimental data, both in terms of the spatial distributions and temporal evolutions. Although this is the first attempt at using the Cherenkov radiation in the measurements of nuclear cross sections, the obtained results suggest the method is convenient and widely applicable for high precision proton therapy.

Particle identification technique using grid ionization chamber at China Spallation Neutron Source

Back-n white neutron source at China Spallation Neutron Source facility requires a detector with charged-particle identification ability for measuring nuclear cross sections. Therefore, a grid ionization chamber (GIC) with an adjustable distance between the cathode and grid was designed and built. Moreover, a corresponding particle identification algorithm is proposed in order to use the signals of the anode (QA) and cathode (QC), or the signal (QA) of the anode and the time difference (Δ t) between the cathode and anode signals, based on the interactive behaviors of charged particles and the GIC's working principle. First, the GIC performance was measured using a 241Am α source for preliminary performance testing, which provided an energy resolution of 5.25%. Its good particle identification performance was demonstrated by identifying 3H and 4He from neutron reactions with 6Li using a 2D QC-QA plot and Δ t-QA plot. Furthermore, 3H and 4He can be completely distinguished from the updated 2D QC-QA plot and Δ t-QA plot, in which 3H with a small incident angle is selected. Finally, it was concluded that our GIC with the proposed particle identification algorithm could identify charged particles effectively for the future measurement of nuclear cross sections.

High precision analysis of isotopic composition for samples used for nuclear cross-section measurements

For the accuracy improvement of nuclear data of minor actinides and long-lived fission products in the project of “Research and development for Accuracy Improvement of neutron nuclear data on Minor Actinides”, the isotopic compositions of two Am samples (241 Am sample and 243 Am sample) were analyzed by thermal ionization mass spectrometry. Only the peak of 241 Am was observed in the analysis of 241 Am sample, and level of isotopic impurities were improved from 0.1% to 0.0004%. In the analysis of 243 Am sample, the peak of unreported isotope of 242m Am was observed in addition to the peaks of 243 Am and 241 Am. The mass spectrometry also showed that 243 Am sample has other unreported impurities such as 239 Pu and 240 Pu.

Cross Section Measurements for the 23Na(p,γ)24Mg Reaction at LUNA

LUNA, the Laboratory for Underground Nuclear Astrophysics, is an accelerator facility for measurements of nuclear cross sections of astrophysical interest. The greatly reduced cosmic ray background at LUNA's underground location in the Gran Sasso National Laboratory (LNGS) allows direct measurements of weak reactions at low energies.One of the reactions currently under study at LUNA is 23Na(p,γ)24Mg, which links the NeNa and MgAl cycles in stellar burning. The LUNA facility is presented, with a focus on the current experimental efforts to study the reaction 23Na(p,γ)24Mg.

First application of the Trojan horse method with a radioactive ion beam: Study of the18F(p,α)15Oreaction at astrophysical energies

Measurement of nuclear cross sections at astrophysical energies involving unstable species is one of the most challenging tasks in experimental nuclear physics. The use of indirect methods is often unavoidable in this scenario. In this paper the Trojan Horse Method is applied for the first time to a radioactive ion beam induced reaction studying the $^{18}$F($p,{\alpha}$)$^{15}$O process at low energies relevant to astrophysics via the three body reaction $^{2}$H($^{18}$F,${\alpha}^{15}$O)n. The knowledge of the $^{18}$F($p, {\alpha}$)$^{15}$O reaction rate is crucial to understand the nova explosion phenomena. The cross section of this reaction is characterized by the presence of several resonances in $^{19}$Ne and possibly interference effects among them. The results reported in Literature are not satisfactory and new investigations of the $^{18}$F($p,{\alpha}$)$^{15}$O reaction cross section will be useful. In the present work the spin-parity assignments of relevant levels have been discussed and the astrophysical S-factor has been extracted considering also interference effects

Theoretical uncertainties in extracting cosmic-ray diffusion parameters: the boron-to-carbon ratio

PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly reduced statistical uncertainties in experimental measurements of cosmic-ray fluxes. In particular, new determinations of traditional diagnostic tools such as the boron-to-carbon ratio (B/C) are expected to significantly reduce errors on cosmic-ray diffusion parameters, with important implications for astroparticle physics, ranging from inferring primary source spectra to indirect dark matter searches. It is timely to stress, however, that the conclusions obtained crucially depend on the framework in which the data are interpreted as well as from some nuclear input parameters. We aim at assessing the theoretical uncertainties affecting the outcome, with models as simple as possible while still retaining the key dependencies. We compare different semi-analytical, two-zone model descriptions of cosmic-ray transport in the Galaxy. We test for the effect of a primary source contamination in the boron flux by parametrically altering its flux, as well as for nuclear cross section uncertainties. Our study on preliminary results from AMS-02 suggests that, differently for instance from the leptonic case, realistic modelling of the geometry of the Galaxy and of the source distribution are of minor importance to correctly reproduce B/C data at high energies and thus, to a large extent, for the extraction of diffusion parameters. The Ansatz on the lack of primary injection of boron represents the most serious bias, and requires multi-messenger studies to be addressed. If this uncertainty could be lifted, nuclear uncertainties would still represent a serious concern, which degrade the systematic error on the inferred parameters to the 20% level, or three times the estimated experimental sensitivity. In order to reduce this, a new nuclear cross section measurement campaign is probably required.

Radiochemical determination of Inertial Confinement Fusion capsule compression at the National Ignition Facility.

We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,γ) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fuel and, consequently, to the fuel's areal density. The observed ratio of the concentrations of (198m+g)Au and (196g)Au is a performance signature of ablator areal density and the fuel assembly confinement time. We identify the measurement of nuclear cross sections of astrophysical importance as a potential application of the neutrons generated at the NIF.

GCR environmental models I: Sensitivity analysis for GCR environments

Accurate galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z>2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.