Proton-induced Nuclear Reactions Research Articles

Vortex Target: A New Design for a Powder-in-Gas Target for Large-Scale Radionuclide Production

This paper presents a design and working principle for a combined powder-in-gas target. The excellent surface-to-volume ratio of micrometer-sized powder particles injected into a forced carrier-gas-driven environment provides optimal beam power-induced heat relief. Finely dispersed powders can be controlled by a combined pump-driven inward-spiraling gas flow and a fan structure in the center. Known proton-induced nuclear reactions on isotopically enriched materials such as 68Zn and 100Mo were taken into account to be conceptually remodeled as a powder-in-gas target assembly, which was compared to thick target designs. The small irradiation chambers that were modeled in our studies for powdery ‘thick’ targets with a mass thickness (g/cm2) comparable to 68Zn and 100Mo resulted in the need to load 2.5 and 12.6 grams of the isotopically enriched target material, respectively, into a convective 7-bar pressured helium cooling circuit for irradiation, with ion currents and entrance energies of 0.8 (13 MeV) and 2 mA (20 MeV), respectively. Current densities of ~2 μA/mm2 (20 MeV), induces power loads of up to 4 kW/cm2. Moreover, the design work showed that this powder-in-gas target concept could potentially be applied to other radionuclide production routes that involve powdery starting materials. Although the modeling work showed good convective heat relief expectations for micrometer-sized powder, more detailed mathematical investigation on the powder-in-gas target restrictions, electrostatic behavior, and erosion effects during irradiation are required for developing a real prototype assembly.

Calculation of reactions cross section for proton-induced nuclear reactions on Iodine-127 isotope

Radioisotope production for nuclear medicine is tomography devices. Both single photon emissions computed tomography (SPECT) and positron emission tomography (PET) is used for diagnosis in nuclear medicine we have calculated the reaction cross section and investigated the excitation functions for the formation of 127,126 125 I , 126,127,128 Xe , 126,125 Te isotopes in the interactions of proton particle with the nucleus of the iodine-127 isotope. The analysis shows that there is a variation of interaction cross-section with a variation of energy of the incident particle. The result shows that the plots of the 127 I (p,ng), and 127 I (p,2ng), graphs have full excitation curve. The productions confirm the presence of Xenon-127 and Xenon-126 isotopes are possible at the energy range of 0 to 30 MeV from the iodine-127 nucleus. Keywords : Cross-Section; Excitation function; Nuclear Reaction; Radioisotope; Statistical Multistep Reaction

Double differential cross section calculations for 16O and 90Zr elements

Double differential cross sections in proton induced reactions on 90Zr and O2 (inert matrix fuel) is calculated at the bombarding energies between 29 and 300 MeV. The proton-induced nuclear reaction cross section data can be used in technical applications such as the isotope production alternatives, spallation reactions for production of neutrons in spallation neutron source, etc. In this study, the cascade excition model including the effect of preequilibrium is used to calculate the differential cross section. Then, the obtained results are discussed and compared with available experimental data.

Cross sections of proton-induced nuclear reactions on bismuth and lead up to 100 MeV

Cross sections of proton-induced nuclear reactions on bismuth and lead up to 100 MeV

Nuclear in-medium effects on $$\eta $$ η dynamics in proton–nucleus collisions

The dynamics of $\eta$ meson produced in proton-induced nuclear reactions via the decay of N$^{\ast}(1535)$ has been investigated within the Lanzhou quantum molecular dynamics transport model (LQMD). The in-medium modifications of the $\eta$ production in dense nuclear matter are included in the model, in which an attractive $\eta$-nucleon potential is implemented. The impact of the $\eta$ optical potential on the $\eta$ dynamics is investigated. It is found that the attractive potential leads to the reduction of high-momentum (kinetic energy) production from the spectra of momentum distributions and inclusive cross sections and increasing the reabsorption process by surrounding nucleons.

Experimental cross-sections for proton-induced nuclear reactions on natMo

In the framework of the Co-ordinated Research Project of the IAEA, we measured in detail cross-sections of the nuclear reactions natMo(p,x)93gTc, 93mTc, 93m+gTc, 94gTc, 94mTc, 95gTc, 95mTc, 96m+gTc, 97mTc, 99mTc, 90Mo, 93mMo, 99Mo, 88gNb, 88mNb, 89gNb, 89mNb, 90m+gNb, 90m+gNbcum, 91mNb, 92mNb, 95gNb, 95mNb, 95m+gNb, 96Nb, 97m+gNb, 88m+gZrcum and 89m+gZrcum in the energy range of 6.9–35.8MeV. The data for formation of 97mTc, 88gNb, 88mNb and 89mNb are reported for the first time. The obtained results were compared to the prediction of the nuclear reaction model code TALYS adopted from the TENDL-2015 library and to the previously published cross-sections. The thick target yields for all the radionuclides were calculated from the measured data. We suggest recommended cross-sections and thick target yields for the 100Mo(p,2n)99mTc, 100Mo(p,x)99Mo and natMo(p,x)96m+gTc nuclear reactions deduced from the selected experimental data.

A Compton camera prototype for prompt gamma medical imaging

A Compton camera prototype for a position-sensitive detection of prompt gamma rays from proton-induced nuclear reactions is being developed in Garching. The detector system allows to track the Compton-scattered electrons. The camera consists of a monolithic LaBr3:Ce scintillation absorber crystal, read out by a multi-anode PMT, preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The LaBr3:Ce crystal has been characterized with radioactive sources. Online commissioning measurements were performed with a pulsed deuteron beam at the Garching Tandem accelerator and with a clinical proton beam at the OncoRay facility in Dresden. The determination of the interaction point of the photons in the monolithic crystal was investigated.

Nuclear in-medium effects of strange particles in proton-nucleus collisions

The dynamics of strange particles produced in proton-induced nuclear reactions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics transport model. The in-medium modifications on particle production in dense nuclear matter are considered through corrections on the elementary cross sections via the effective mass and the mean-field potentials. It is found that the attractive antikaon-nucleon potential enhances the subthreshold $\overline{K}$ production and influences the structure of inclusive spectra. The strangeness production is strongly suppressed in proton-induced reactions in comparison to heavy-ion collisions. The kaon-nucleon and antikaon-nucleon potentials change the structures of rapidity and transverse momentum distributions and the inclusive spectra. The measured ${K}^{\ensuremath{-}}/{K}^{+}$ ratios in collisions of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C},\phantom{\rule{0.28em}{0ex}}{}^{197}\mathrm{Au}+{}^{197}\mathrm{Au},\phantom{\rule{0.28em}{0ex}}p+{}^{12}\mathrm{C}$, and $p+{}^{197}\mathrm{Au}$ from the KaoS Collaboration have been well explained with the inclusion of the in-medium potentials.

The excitation functions of 100Mo(p,x)99Mo and 100Mo(p,2n)99mTc

Proton-induced nuclear reactions for generation of 99Mo and 99mTc radionuclides were investigated using the stacked-foil activation technique on 99.05% enriched 100Mo targets at energies up to Ep=21MeV. Excitation functions of the reactions 100Mo(p,x)99Mo and 100Mo(p,2n)99mTc have been measured.

7Be-recoil radiolabelling of industrially manufactured silica nanoparticles.

Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with 7Be, which exhibits a physical half-life of 53.29 days and emits γ-rays of 478 keV energy, and is suitable for most radiotracer studies. 7Be is produced via the proton-induced nuclear reaction 7Li(p,n)7Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of 7Be atoms gives them a range that allows the 7Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO2 nanoparticles. The process can be controlled in such a way that no alterations of the 7Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17–18 MeV that are available in most medical research centres could be used for this purpose.

Evaluated Activation Cross Section Data for Proton Induced Nuclear Reactions on W up to 3 GeV Incident Energy

Evaluated cross-section data files were prepared for stable tungsten isotopes with the objective to provide reliable and sound nuclear data for activation and inventory calculations of the European Spallation Source, which utilizes a tungsten target. The data files contain yields of radionuclides produced by proton induced reactions with incident energies up to 3 GeV. The calculations of cross-sections were performed using the intranuclear cascade model, the pre-equilibrium exciton model, and the Hauser-Feshbach model. The available experimental information, results of calculations and systematics were applied for the evaluation of yields of residual nuclei using statistical methods implemented in the computer code package BEKED developed at KIT.

Electron screening in nickel

In order to investigate the interplay between nuclei and their surroundings, we studied proton-induced nuclear reactions over an energy range from 0.86 to 3.08MeV for different environments: Ni metal and NiO insulator. The measurements were based on the observation of the yields of 59, 61, 63, 64, 65Cu and 58, 60, 62Ni de-excitation $ \gamma$ -rays. Shifts in the resonance energy for the metallic target relative to the insulator one were not observed. Electron screening potential of $ U_{e}=31\pm 13$ keV was deduced for 64Ni $ (p,n\gamma )$ 64Cu reaction, while $ U_{e}=19\pm 4$ keV was deduced for 58Ni $(p,\gamma )$ 59Cu and 60Ni $(p,\gamma )$ 61Cu reactions. The observed electron screening potentials for (p,n) and (p, $\gamma$ ) reactions are the same within error bars, but the comparison with previous measurements raises the question of the independence of the electron screening from the reaction exit channel.

Simulation of prompt gamma-ray emission during proton radiotherapy

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector designs. Also, the gamma production cross-sections may be incorporated as prior knowledge in the reconstruction of the proton range from the measurements. In this work, we performed simulations of proton-induced nuclear reactions with the main elements of human tissue, carbon-12, oxygen-16 and nitrogen-14, using the nuclear reaction models of the GEANT4 and MCNP6 Monte Carlo codes and the dedicated nuclear reaction codes TALYS and EMPIRE. For each code, we made an effort to optimize the input parameters and model selection. The results of the models were compared to available experimental data of discrete gamma line cross-sections. Overall, the dedicated nuclear reaction codes reproduced the experimental data more consistently, while the Monte Carlo codes showed larger discrepancies for a number of gamma lines. The model differences lead to a variation of the total gamma production near the end of the proton range by a factor of about 2. These results indicate a need for additional theoretical and experimental study of proton-induced gamma emission in human tissue.

MO-A-213AB-06: Validation of Nuclear Reaction Models to Simulate Proton Therapy Range Verification Using Prompt Gamma-Rays.

The impact of nuclear reaction model differences on simulation of prompt gamma-ray imaging for proton therapy range verification was assessed. Four nuclear reaction models were used to simulate gamma emission in proton beams, and were validated against experimental cross-sections. Proton-induced nuclear reactions on carbon, oxygen, nitrogen and calcium were investigated with the Monte Carlo toolkits GEANT4 9.5 and MCNPX 2.7, and the dedicated nuclear reaction codes TALYS 1.4 and EMPIRE 3.1. Absolute cross-sections of discrete prompt gamma lines and the total gamma production were obtained for the 1-200 MeV incident proton energy range. They were compared to 34 discrete line measurements reported in literature. Using these cross-sections, we analyzed the gamma production along the path of proton beams passing through various tissues. The differences in absolute discrete line cross-sections as predicted by the models ranged from almost zero to an order of magnitude, depending on the gamma line and incident proton energy. Overall, the dedicated nuclear reaction codes provided a better fit to most experimental excitation functions. For a 150 MeV proton beam stopping in soft tissue, these differences amount to a variation by a factor of 4 of the gamma emission around the Bragg peak location. The maximum of gamma production near the end of proton range differed by 7 mm, and the change of the 50% emission fall-off position was 4 mm. There is a clear need for improvement of nuclear reaction models to accurately simulate proton range verification using prompt gamma-rays. Current simulation codes show large uncertainties in both the total gamma yield and the correlation of gamma emission with the proton Bragg peak. GEANT4 and MCNPX in particular appear to have limited predictive power.

259 TIME-OF-FLIGHT METHOD FOR NEUTRON REJECTION IN PROMPT GAMMA IMAGING OF BEAM RANGE AND DENSITY CHANGES IN PROTON THERAPY

A therapeutic proton beam penetrating a patient generates a large number of prompt photons as well as neutrons, resulting from proton-induced nuclear reactions. This allows for obtaining longitudinal beam-profile images via the detection of selected prompt-gamma rays emitted perpendicularly to the beam direction. The significant neutron background on top of the prompt photons signal was observed. Thus, the goal of presented research is to propose the novel in-situ time-of-flight (TOF) technique for neutron background rejection in order to get the optimum signal from prompt-gamma rays escaping the irradiated object. Density heterogeneities within the patient affect the position of the Bragg peak. Due to potential morphological changes the Bragg peak position may vary during the course of treatment, which may lead to clinically significant under-dosage in the tumor or over-dosage in the organs-at-risk. The Bragg peak shifts due to target morphological modifications, whichmay occur in realistic radiotherapy scenarios (e.g. tumor or normal tissue swelling), can be detected with the presented method to within a few millimeters. We show a clinically relevant correlation between the prompt-gamma profiles and the target (patient) density.

Excitation functions of 186,187,188,189,190,192Ir formed in proton-induced reactions on highly enriched 192Os up to 66 MeV

Cross sections of proton-induced nuclear reactions on highly enriched 192Os were measured up to 66 MeV by using the stacked-foil irradiation technique. Excitation functions are presented for the reactions 192Os(p,n) 192Ir, 192Os(p,3n) 190Ir, 192Os(p,4n) 189Ir, 192Os(p,5n) 188Ir, 192Os(p,6n) 187Ir and 192Os(p,7n) 186Ir. No earlier experimental cross-section data could be found in the literature except for the 192Os(p,n) 192Ir process. Our new experimental results are compared with theoretical predictions by means of the theoretical model code ALICE/ASH. Integral thick-target yield calculations were also performed for the 192Os(p,n) 192Ir and 192Os(p,3n) 190Ir reactions to evaluate the 190Ir contamination level, as a function of energy, in the case of 192Ir productions.

A novel method for radiochemical separation of radioyttrium from Sr targets using precipitation technique

Abstract A method is described for separating radioyttrium from strontium within 30−40 min. The yield of radioyttrium amounts to 97% and the strontium impurity occurs at 8.2 ppm level. Radioyttrium (containing 86Y, 87Y and 88Y) was produced by proton-induced nuclear reactions on natSrCO3 deposited on Cu backing. Irradiated target material was removed with acetone and 8 M HCl solution from copper substrate, followed by ethyl cellulose (EC) filter removal. Optimal radioyttrium separations from Cu and 65Zn activities were obtained by loading the mixture on Dowex-1×8 anion exchange resin and eluting with 8 M HCl, followed by precipitation of natSr as SrSO4 while radioyttrium passed through the filter paper.

Excitation functions of the proton-induced nuclear reactions on natSn up to 40 MeV

We have measured the production cross-sections of the residual radionuclides for proton-induced reactions on natural tin by using a stacked-foil activation technique in the energy range from threshold energy to 40 MeV at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The results were compared with the earlier reported experimental data and theoretical calculations based on the TALYS and the ALICE-IPPE codes. The present results are in general good agreement with the available literature data and calculated results by using the computer codes TALYS and ALICE-IPPE. The thick target integral yields were also deduced from the measured excitation functions of the produced radionuclides.

Experimental study of proton-induced nuclear reactions in 6,7Li

The 6Li(p,α)3He and 7Li(p,α)4He reaction cross sections were obtained for E = 90–580 keV and E = 90–1740 keV, respectively. R-matrix and polynomial fits to the bare astrophysical S-factor confirmed, with improved accuracy, previous work data, yielding Sb(0) = 3.52 ± 0.08 MeV b, and 55.6+0.8−1.7 keV b for the 6Li and 7Li reactions, respectively. Therefore, the astrophysical consequences related to these two isotopes remain essentially unchanged. With the present work Sb(E) data, a reanalysis of the low energy data for different environments—Li2WO4 insulator, Li metal, and PdLix alloys—confirms that the large electron screening effects can be explained by the plasma model of Debye applied to the quasi-free electrons in the metallic samples.

Excitation function measurements and integral yields estimation for natZn(p,x) reactions at low energies

Excitation functions have been measured for a number of proton-induced nuclear reactions on natural zinc in the energy range from 27.5 MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions and thick target yield for the reactions leading to the formation of 67Ga, 66Ga, 68Ga, 62Zn and 65Zn are presented and compared with earlier reported experimental data. The experimental cross-sections and the production yields are tabulated; the excitation functions and the thick target yield curves are plotted in graphs.