Proton-induced Reactions Research Articles

Technical note: Implementing MRI/CT-based elemental concentration data to Monte Carlo simulation for yielding positron emitters in proton therapy.

The elemental concentration (especially oxygen and carbon) and mass density must be accurately assigned to perform Monte Carlo (MC) simulations for predicting proton-induced nuclear reactions in the human body. We recently proposed an approach to quantify elemental concentrations and mass densities of human soft tissues from water content (WC) data obtained by quantitative magnetic resonance (MR) imaging (which we called "MRWC"). This study presents the first implementation of MRWC-derived elemental concentrations and mass densities as complementary inputs into MC simulations on a virtual head phantom, and demonstrates the simulation of positron emitter production yields in proton therapy. An MC code, PHITS, was used to simulate proton therapy with a monoenergetic 140 MeV beam for a digital head phantom provided by BrainWeb. Three different head images were synthesized as inputs: a conventional CT image, an ideal CT image as a reference, and a WC image coupled with the bone-only CT image for a hybrid approach (MRWC/CT). Thereafter, the performance of the MRWC/CT method was evaluated by comparing its accuracy in predicting the production yields of positron emitters (11C and 15O) with the gold-standard CT-only method. The MRWC/CT method could predict 11C and 15O production yield maps that closely resembled the corresponding reference maps, while the CT-only method failed. The structural similarity index measures between the reference and CT- or MRWC/CT-derived maps were improved from 0.67 (CT-only) to 0.87 (MRWC/CT) for 11C and 0.76 (CT-only) to 0.93 (MRWC/CT) for 15O. Furthermore, applying post-processing normalizations to account for elemental density variations in the production yields of positron emitters facilitated the determination of distal fall-off positions in depth activity profiles. At least in the head area, the MRWC/CT method demonstrated potential for more precise predictions of proton-induced positron emitter distributions via MC simulations than that of the CT-only method.

Studying the impact of deuteron non-elastic breakup on 93Zr + d reaction cross sections measured at 28 MeV/nucleon

Abstract The deuteron is a loosely bound system that can easily break up into its constituent proton and neutron whilst in the presence of Coulomb and nuclear fields. Previous experimental studies have shown that this breakup process has a significant impact on residual-nucleus production from deuteron bombardment in the high-energy range of 50–210 MeV/nucleon. However, there remains a lack of cross-section data at energies below 50 MeV/nucleon. The current study determined 93Zr + d reaction cross sections under inverse kinematics at approximately 28 MeV/nucleon using the BigRIPS separator, OEDO beamline, and SHARAQ spectrometer. Cross sections from this research were compared with previous measurements and theoretical calculations. The experimental results show a large enhancement of the production cross sections of residual nuclei, especially those produced from a small number of particle emissions, compared to the proton-induced reaction data at similar bombarding energy. The DEURACS calculation, which quantitatively takes deuteron-breakup effects into account, reproduces the data well. As a long-lived fission product, 93Zr remains a challenge for nuclear-waste disposal and treatment. This study’s low-energy data may assist future consideration of nuclear-waste treatment facilities, where 93Zr + d may feasibly transmute the waste into short-lived/stable nuclei.

Proton acceleration with multi-peak energy spectra tailored by vortex laser

A novel flying cascaded acceleration mechanism is proposed to generate energetic proton beams with multi-peak energy spectra using a circularly polarized (CP) Laguerre–Gaussian (LG) laser pulse in three-dimensional particle-in-cell simulations. Simulations show that the protons are initially accelerated and compressed into the beam center via the radiation pressure of the CP LG (σz = −1) laser pulse. Then, they are tailored by flying dipolar electric fields in this LG laser, resulting in a multi-peak energy spectrum. Each shaped proton peak exhibits a narrow energy spread of ∼5% and high flux of ∼2 × 108 protons/MeV at giga-electron volts energy. Such a flying cascaded acceleration mechanism extends the energy spectra of proton beams from monoenergetic to multi-peak structure, thereby potentially enhancing the generation efficiency of monoenergetic proton beams for various applications, such as proton-induced spallation reactions, proton radiography, and proton therapy.

Measurement of nuclide production cross sections for proton-induced reactions on [formula omitted]Ti and 93Nb at 0.8 and 3.0 GeV

The nuclide production cross sections for proton-induced reactions on natTi and 93Nb at 0.8 and 3.0 GeV were measured using an activation technique at Japan Proton Accelerator Research Complex. A total of 27 and 94 nuclide production cross sections for the natTi(p,X) and 93Nb(p,X) reactions were obtained, respectively. Cross sections of the natTi(p,X)44Sc, 93Nb(p,X)52Mn, 93Nb(p,X)69mZn, 93Nb(p,X)82mRb, 93Nb(p,X)85mY, 93Nb(p,X)87mY, 93Nb(p,X)90mY, 93Nb(p,X)91mNb, 93Nb(p,X)92mNb, and 93Nb(p,X)93mMo reactions were successfully measured for the first time. In addition, the cross sections of the natTi(p,X)46Sc, 93Nb(p,X)73As, 93Nb(p,X)85Y, and 93Nb(p,X)87Y reactions above about 1 GeV were firstly measured. The present data were compared with the results from nuclear reaction models in PHITS and data retrieved from Japanese Evaluated Nuclear Data Library High Energy file 2007 (JENDL/HE-2007). As the nuclear reaction models, Liège IntraNuclear Cascade (INCL), two versions of JAERI Quantum Molecular Dynamics, and Jet AA Microscopic Transport Model coupled with an evaporation process were applied. The prediction accuracy of JENDL/HE-2007 was the best for the 7Be production cross section of both targets. As an overall trend, underestimation of INCL and all of the models were confirmed for the natTi(p,X) and 93Nb(p,X) reactions, respectively.

Excitation functions of proton-induced nuclear reactions on natCaCO3 up to 60 MeV

47Sc could be used in SPECT imaging and is also suitable for targeted therapy of small tumours. Application of 47Sc is quite promising as theranostic with its diagnostic pair 44Sc or 43Sc. Excitation functions for the production of 47Sc and its accompanying impurities through proton bombardment of natural calcium carbonate (natCaCO3) targets were experimentally evaluated and compared with both previous measurements and TALYS predictions. The integral production yields of 47Sc, as well as the main impurities 44m,46,48Sc, were calculated. The consistency of the results with available experimental data was verified for each reaction. The target yield was determined using the measured activity of the produced radionuclides.

Neutron-production double-differential cross sections of natPb and 209Bi in proton-induced reactions near 100 MeV

The lack of double-differential cross-section (DDX) data for neutron production below the incident proton energy of 200 MeV hinders the validation of spallation models in technical applications, such as research and development of accelerator-driven systems (ADSs). The present study aims to obtain experimental DDX data for ADS spallation target materials in this energy region and identify issues related to the spallation models by comparing them with the analytical predictions. The DDXs for the (p,xn) reactions of natPb and 209Bi in the 100-MeV region were measured over an angular range of 30° to 150° using the time-of-flight method. The measurements were conducted at Kyoto University utilizing the FFAG accelerator. The DDXs obtained were compared with calculation results from Monte Carlo-based spallation models (INCL4.6/GEM, Bertini/GEM, JQMD/GEM, ISOBAR/GEM, CEM03.03, INCL4/ABLA, Bertini/ABLA, ISABEL/ABLA, INCL++/ABLA07, INCL++/GEMINI++, and INCL++/SMM) and the evaluated nuclear data library, JENDL-5. Comparison between the measured DDX and analytical values based on the spallation models and evaluated nuclear data library indicated that, in general, the CEM03.03 model demonstrated the closest match to the experimental values. Additionally, the comparison highlighted several issues that need to be addressed in order to improve the reproducibility of the proton-induced neutron-production DDX in the 100 MeV region by these spallation models and evaluated nuclear data library. To enhance the reproducibility of underperforming spallation models and evaluated nuclear data library, it is recommended to address each of the issues identified in this study.

Production routes analysis of PET agent 72As from alpha and proton induced reaction using different level density models

This study evaluated the production routes of the medically essential radioisotope 72As from the stable isotopes of gallium, germanium, arsenic, and selenium, where four alpha-induced reactions: 69Ga(α, n)72As, 71Ga(α, 3n)72As, 70Ge(α, np)72As, and 72Ge(α, nt)72As and five proton-induced reactions: 72Ge(p, n)72As, 73Ge(p, 2n)72As, 74Ge(p, 3n)72As, 75As(p, nt)72As, and 74Se(p, 2np)72As are evaluated using three phenomenological and one microscopic nuclear level density models in different energy ranges. The investigation compares the calculated results based on the chosen models and the experimental data collected from the EXFOR data library. Statistical factors H, D, and R were also computed to determine the level density model with the best fit to the experimental data. Some level density parameters were adjusted to enrich the fits further, and integral yield vs energy was calculated using the best-fitted models.

Prussian blue analog with separated active sites to catalyze water driven enhanced catalytic treatments

Chemodynamic therapy (CDT) uses the Fenton or Fenton-like reaction to yield toxic ‧OH following H2O2 → ‧OH for tumoral therapy. Unfortunately, H2O2 is often taken from the limited endogenous supply of H2O2 in cancer cells. A water oxidation CoFe Prussian blue (CFPB) nanoframes is presented to provide sustained, external energy-free self-supply of ‧OH from H2O to process CDT and/or photothermal therapy (PTT). Unexpectedly, the as-prepared CFPB nanocubes with no near-infrared (NIR) absorption is transformed into CFPB nanoframes with NIR absorption due to the increased Fe3+-N ≡ C-Fe2+ composition through the proposed proton-induced metal replacement reactions. Surprisingly, both the CFPB nanocubes and nanoframes provide for the self-supply of O2, H2O2, and ‧OH from H2O, with the nanoframe outperforming in the production of ‧OH. Simulation analysis indicates separated active sites in catalyzation of water oxidation, oxygen reduction, and Fenton-like reactions from CFPB. The liposome-covered CFPB nanoframes prepared for controllable water-driven CDT for male tumoral mice treatments.

Investigation of the Excitation Functions of Proton-Induced Reactions on Natural Gadolinium Using the Nuclear Interaction Codes TALYS 1.96 and EMPIRE 3.2

Investigation of the Excitation Functions of Proton-Induced Reactions on Natural Gadolinium Using the Nuclear Interaction Codes TALYS 1.96 and EMPIRE 3.2

Effective polarization in proton-induced α knockout reactions

The effective polarization of the residual nucleus in the proton-induced $\alpha$ knockout reaction is investigated within the distorted wave impulse approximation framework. The strong absorption of the emitted $\alpha$ particle results in strong selectivity on the reaction "position" depending on the third component of the single-particle orbital angular momentum of the $\alpha$ particle inside a nucleus, hence on the spin direction of the reaction residue. This is caused by a mechanism that is similar to the Maris effect, the effective polarization in the proton-induced proton knockout reactions. However, as a distinct feature of the effective polarization in the $\alpha$ knockout process, the spin degrees of freedom of the reacting particles play no role. The $\alpha$ knockout process with complete kinematics can be a useful polarization technique for the residual nucleus, without actively controlling the spin of the proton.

TENDL-based evaluation and adjustment of p+111Cd between 1 and 100 MeV

Proton induced reaction data are needed in the optimization of various radioisotope production routes, among others. In this work, the evaluation of proton-induced reactions on 111Cd between 1 and 100 MeV using the TALYS code system within an iterative Bayesian Monte Carlo (iBMC) framework, is presented. The method involves the simultaneous variation of a large number of nuclear reaction models included in the TALYS code system as well as their parameters. Each random TALYS calculation yields a vector of calculated values of cross section observables as well as the angular distributions, among others, which were compared with corresponding vectors of carefully selected differential experimental data for reaction channels where data were available. The random nuclear data file with the maximum likelihood function value obtained from combining the individual χ2s computed for the considered reaction channels was chosen as the parent vector and the starting point for the generation of a further set of random TALYS calculations. This was repeated multiple times until a targeted convergence of 5% was reached. The final evaluated file was compared with available experimental data from the EXFOR database as well as with the evaluations from the TENDL-2021 and JENDL5.0 libraries, and found to compare favorably.

A study of proton-induced reactions on natural Silicon targets

Experimental excitation functions of isotopes produced in reactions p + natSi are compared with the results of nuclear reaction program TALYS 1.95 and semi-empirical cross section formulas. We consider excitation functions of 7 isotopes (28Mg, 26Al, 24,22Na, 18F and 10,7Be) produced in reactions at bombarding energies of 20-144 MeV. They are compared with the predictions of the code TALYS 1.95, the semi-empirical formulas of Silberberg-Tsao (code yieldx) and SPACS. Comparisons of the results of the code TALYS 1.95 and previously published results of code ALICE are made. The predictive power of code TALYS 1.95 may be questioned for reaction products with mass number very much smaller than the target and of semi-empirical formulas at lower energies.

Activation cross sections of proton-induced reactions on manganese up to 30 MeV

The excitation functions of the 55Mn(p,x)51Cr, 54Mn reactions were measured up to 30-MeV proton energy. The experiment was performed at the RIKEN AVF cyclotron using the stacked-foil activation technique. High-purity germanium (HPGe) detectors were used for the gamma-ray spectrometry. Obtained results were compared with previous experimental data and the prediction of the TALYS nuclear reaction model code available in the TENDL-2021 library. Physical thick target yields of 51Cr and 54Mn were derived from the measured cross sections.

γ-ray emission in proton-induced nuclear reactions on [formula omitted]C and Mylar targets over the incident energy range, Ep = 30 – 200 MeV. Astrophysical implications

We have measured the γ-ray line production cross sections in proton-induced nuclear reactions on various target nuclei (12C, 16O, 24Mg, 28Si, 56Fe) of chemical elements abundant in astrophysical sites (solar flares, the interstellar medium, cosmic compact objects) over the incident energy range of Ep = 30 – 200 MeV. We carried out experimental campaigns in joint collaboration at the K = 200 separated sector cyclotron of iThemba LABS using a high-energy resolution, high-efficiency detection array composed of 8 Compton-suppressed clover detectors comprising 32 HP-Ge crystals for recording the γ-ray energy spectra. In the current paper, we focus on γ-ray de-excitation lines produced in proton irradiations of natC and Mylar targets, in particular, on the prominent 4.439 and 6.129 MeV lines of 12C and 16O which are among the strongest lines emitted in solar flares and in interactions of low-energy cosmic rays (LECRs) with the gas and dust of the inner galaxy. We report new γ-ray production experimental cross section data for ten nuclear γ-ray lines that we compare to previous low-energy data sets from the literature, to the predictions of the TALYS code of nuclear reactions and to a semi-empirical compilation. In the first approach, performing calculations with default input parameters of TALYS we observed substantial deviations between the predicted cross sections and experimental data. Then, using modified optical model potential (OMP) and nuclear level deformation parameters as input data we generated theoretical excitation functions for the above two main lines fully consistent with experimental data. In contrast, the experimental data sets for the other eight analyzed lines from the two proton-irradiated targets exhibit significant deviations with the predicted cross section values. We also report line-shape experimental data for the line complex observed at Eγ = 4.44 MeV in irradiations of the two targets. Finally, we emphasize the astrophysical implications of our results.

Production of 11C, 13N and 15O in proton-induced nuclear reactions up to 200 MeV

Production cross sections of light positron emitters 11C (t1/2=20.36 min), 13N (t1/2=9.97 min) and 15O (t1/2=122 s) have been measured for proton-induced reactions on the main relevant constituents of the human body (C, N and O) from threshold up to 200 MeV of proton incident energy. This has been accomplished by means of two complementary experiments at the clinical proton treatment centers WPE (Essen) and HIT (Heidelberg), both in Germany. In the first case, the multi-foil activation technique was combined with PET imaging, a methodology previously developed at CNA (Seville, Spain). In the second experiment, aimed at energies below 50 MeV, the activation of single foils was measured with conventional LaBr3 detectors. In both cases the IAEA monitor reaction natCu(p,x)63Zn data was used for validation purposes.The most complete and accurate set of excitation functions for the production of light-positron emitters 11C, 13N and 15O in proton induced reactions on human tissue up to 200 MeV is presented. These data are needed for nuclear reaction model development and are extremely important to improve the accuracy of the PET range verification in proton radiotherapy. Seven excitation functions have been measured: 12C(p,x)11C, 14N(p,x)11C, 14N(p,x)13N, 14N(p,γ)15O, 16O(p,x)11C, 16O(p,x)13N and 16O(p,x)15O up to 200 MeV of proton incident energy.

Investigation of the Cross-Sections for the Production of Bromine Isotopes Using Proton-Induced Reactions

We have considered the production of bromine isotopes by studying the cross-sections of nuclear reactions in the selenium enriched target. This is of importance due to the applications in nuclear medicine and radiation therapy. Eight channels are observed in the production of bromine isotopes: 7634Se(p, 2n) 7535Br, 7734Se(p, 3n) 7535Br, 7634Se(p, n) 7635Br, 7734Se(p, 2n) 7635Br, 7734Se(p, n) 7735Br, 7834Se(p, 2n) 7735Br, 8034Se(p, 4n) 7735Br, and 8034Se(p, n) 8035mBr. The energy of the interacting protons ranging from the threshold is 2.20–84.20 MeV and is calculated by using an activation technique. For the proton-induced production of bromine isotopes from selenium target atoms, the stopping power and the yield have been calculated. The Zeigler formula was applied to investigate the cross-sections and to determine the yield for each reaction over the stopping power range. The total energy of each reaction and the corresponding crosssections are statistically analyzed. These energies are reproduced by the incident proton energy with acceptable errors at 0.01 MeV intervals. One of the most significant results of the current calculations is the stopping power of targets evaluated within the Ziegler and SRIM approaches.

Nuclide production cross sections in proton-induced reactions on Bi at GeV energies

Proton-induced nuclide production cross sections for Bi at incident energies of 0.4, 1.5, and 3.0 GeV are measured with the activation method using the proton beams accelerated from the Rapid-Cycling Synchrotron of the Japan Proton Accelerator Research Complex (J-PARC). A total of 127 cross-section data are obtained. The measured data are compared with two types of Monte Carlo-based spallation models (i.e. INCL++ coupled with ABLA07 and INCL4.6 coupled with GEM), and the evaluated nuclear data library, JENDL/HE-2007. The result showed that INCL++/ABLA07 overall agrees with the experimental data, whereas INCL4.6/GEM underestimates the production of fission fragments.

Unravelling the pseudocapacitive origin of graphene oxide-based aerogels by comparative insights.

We reveal the intrinsic pseudocapacitive center of graphene-oxide-based aerogels by investigating different modified graphene skeletons from various approaches. A high proportion of carbonyl groups in carbon networks is shown to optimize the construction of rational pseudocapacitive sites by triggering reversible proton-induced surface reactions, leading to satisfactory electrochemical performance.

A technique for studying (n,p) reactions of astrophysical interest using radioactive beams with SECAR

The formation of nuclei in slightly proton-rich regions of the neutrino-driven wind of core-collapse supernovae could be attributed to the neutrino-p process (νp-process). As it proceeds via a sequence of (p,γ) and (n,p) reactions, it may produce elements in the range of Ni and Sn, considering adequate conditions. Recent studies identify a number of decisive (n,p) reactions that control the efficiency of the νp-process. The study of one such (n,p) reaction via the measurement of the reverse (p,n) in inverse kinematics was performed with SECAR at NSCL/FRIB. Proton-induced reaction measurements, especially at the mass region of interest, are notably difficult since the recoils have nearly identical masses as the unreacted projectiles. Such measurements are feasible with the adequate separation level achieved with SECAR, and the in-coincidence neutron detection. Adjustments of the SECAR system for the first (p,n) reaction measurement included the development of new ion beam optics, and the installation of the neutron detection system. The aforementioned developments along with a discussion on the preliminary results of the p(58Fe,n)58Co reaction measurement are presented.

First (p,n) reaction measurement in inverse kinematics with SECAR

Nucleosynthesis in the νp-process occurs in regions of slightly proton-rich nuclei in the neutrino-driven wind of core-collapse supernovae. The process proceeds via a sequence of (p,γ) and (n,p) reactions, and depending on the conditions, may produce elements between Ni and Sn. Recent studies show that a few key (n,p) reactions regulate the efficiency of the neutrino-p process (νp-process). We performed a study of one of such (n,p) reactions via the measurement of the reverse (p,n) in inverse kinematics with SECAR at NSCL/FRIB.Such proton-induced reaction measurements are particularly challenging, as the recoils and the unreacted projectiles have nearly identical masses. An appropriate separation level can be achieved with SECAR, and along with the incoincidence detection of neutrons these measurements become attainable. The preparation of the SECAR system for accommodating its first (p,n) reaction measurement, including the development of alternative ion beam optics, and the setup of the in-coincidence neutron detection, along with discussion on preliminary results from the p(58Fe,n)58Co reaction measurement are presented and discussed.