2n Reaction Research Articles

Cross-section measurement for (n,2n) reaction induced by 14 MeV neutron on platinum isotopes

Neutron induced the (n, 2n) reaction cross sections of platinum isotopes (190Pt, 192Pt, 196Pt and 198Pt) were well measured by the neutron activation and off-line gamma-ray technique around neutron energy of 14 MeV. During the irradiating time, the flux fluctuation of generating neutron was monitored by accompanying α-particle, while the cross section-ratio of 90Zr (n, 2n)89Zr to 93Nb(n, 2n)92mNb reactions were used to determine the neutron energies, which varied with the emission angle. As a result, the cross sections of 190Pt (n, 2n)189Pt, 192Pt (n, 2n)191Pt, 196Pt (n, 2n)195mPt, 198Pt (n, 2n)197mPt and 198Pt (n, 2n)197gPt reactions have been deduced at En = 14.1 ± 0.2 MeV, 14.5 ± 0.2 MeV and 14.7 ± 0.1 MeV, respectively. Meanwhile, the comparisons between this work and the literature date were given, as well as evaluated nuclear data and simulation data (ENDF/B-VIII.0, JEFF 3.3, ROSFOND-2010, JENDL/AD-2017 and Talys 1.9). The results shows an agreement with literature work as a whole, except the 196Pt (n, 2n)195mPt reaction.

Precise resonance energies measured for energy calibration of particle accelerator using thin silicon–nitride foils

In this work resonance parameters of the 28Si(p,p′γ)28Si (Eγ = 1779 keV) and 14N(p,p′γ)14N (Eγ = 2313 keV) reactions were measured between 3 and 4 MeV proton energies for absolute proton beam energy calibration of particle accelerators. For the measurements commercially available self-supporting thin silicon–nitride films and a HPGe gamma-detector were used which are readily available in most accelerator laboratories. Based on our measurement and on the assessment of literature data, the following resonance energies and widths are recommended: 3100.6 ± 0.9 keV (Γ = 11.9 ± 0.4 keV) and 3338.1 ± 1.0 keV (Γ = 11.0 ± 0.5 keV) in 28Si(p,p′γ)28Si and 3903.1 ± 1.7 keV (Γ = 98 ± 1 keV) and 3991.6 ± 1.1 keV (Γ = 10.8 ± 0.5 keV) in 14N(p,p′γ)14N. In addition to the resonance measurements, absolute thick target yields and gamma-ray angular distributions were measured for the 28Si(p,p′γ)28Si (Eγ = 1779 keV) reaction in the vicinity of Ep = 3.10 and 3.34 MeV for ion beam analysis purposes using a thick silicon wafer target.

Cross section of 15N-2D nuclear reactions from 3.3 to 7.0 MeV for simultaneous hydrogen and deuterium quantitation in surface layers with 15N ion beams

The cross section for the combined 2D(15N,p)16N and 2D(15N,nγ)16O nuclear reactions of deuterium (2D) with incident 15N ions is evaluated and found to increase by two orders of magnitude between 3.3 and 7.0 MeV. Detecting the γ-rays at 6.1 and 7.1 MeV from these reactions allows quantifying the depth-integrated 2D content in materials in parallel with nanometer-resolved quantitative hydrogen (1H) depth profiling in surface layers through resonant 1H(15N,αγ)12C nuclear reaction analysis (NRA) using 15N ion beams. The information depth and sensitivity of 15N-2D NRA is estimated through energy loss simulations of the 15N projectiles in the analyzed material. Good agreement of the integral 2D quantitation through 2D(15N,p)16N and 2D(15N,nγ)16O NRA with 2D depth profiles obtained independently via 2D(3He,p)4He NRA is demonstrated at the example of 2D plasma-exposed tungsten samples. The simultaneous quantitation of 2D and depth-resolved 1H profiling with a single 15N ion beam promises application potential to investigate hydrogen-isotope exchange and diffusion processes in surface and thin buried layers.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНАЯ ОЦЕНКА СЕЧЕНИЙ РЕАКЦИЙ 16O(p, α)13N И 12C(p, γ)13N,13C(p, n)13N, УСРЕДНЕННЫХ ПО СПЕКТРУ ПРОТОНОВ ОТДАЧИ ПРИ УПРУГОМ (N, P)-РАССЕЯНИИ 14 МЭВ НЕЙТРОНОВ В ВОДОРОДОСОДЕРЖАЩИХ СРЕДАХ

The paper describes the calculation-and-experimental method used to measure σO, σC cross-sections of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions when these cross-sections were averaged over the spectrum of recoil protons in hydrogen-containing media. Measurements were performed with the help of the ∼14 MeV neutron source. As a result, cross-sections were determined to be σO=17,2 Mbarn, σC =2,59 Mbarn and this fairly well agrees with the sufficiently limited data available on the energy dependence of cross-sections from the above reactions in the proton energy region E≤10 MeV. Cross-sections of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions in the region of small and medium proton energies E≤10 MeV are of interest for the fundamental science when studying the CNO - cycle of hydrogen burning in rather large stars and also for applied sciences when it is necessary to solve certain problems like (i) considering "false" nitrogen formation when protein content is determined in grain crops using the neutron activation analysis and the 14 MeV neutron source; (ii) studying applicability of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions to produce the shortlived β+-radioactive isotope 13N directly in water and alcohol solutions of preparations for positronemission tomography (PET) with high-energy sources of (D,T)-neutrons; and (iii) studying applicability of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions with the formation of the β+-radioactive isotope 13N to determine actual distribution of absorbed doses in the patient body or in the phantom thereof based on the annihilation radiation after a session of neutron therapy with the 14 MeV neutron source or after a proton therapy session.

Characterization of an electrically cooled BEGe detector till E[formula omitted] MeV

An electrically cooled Broad Energy Germanium (BEGe) detector has been characterized in the energy range Eγ∼0.122 - 7 MeV by utilizing the γ-rays emitted by a short-lived resonance state in 15O populated through 14N(p, γ) reaction and standard radioactive source (152Eu). The experimental results have been reproduced through simulations with GEANT4 code, including vendor specified detector geometry along with the detailed construction of the target holder flange, to delineate the effects of the holder at various energies and detector position. Later the efficiency with a bare point source has been simulated. It has been found that the electrically cooled BEGe detector is suitable for usage in the γ-ray spectroscopy as well as for the study of resonance phenomena in nuclear astrophysics.

Nuclear spectrometry of 9.6 h 196Aum2 and the reaction of 197Au with fast neutrons

The neutron activation of gold is the basis of an implosion performance diagnostic at the National Ignition Facility at Lawrence Livermore National Laboratory. In support of this diagnostic, a series of γ-ray spectrometric measurements of the decay of 196Aum2 (Jπ = 12−) was performed to improve the currently accepted literature values of the nuclear data associated with its half-life, γ-ray energies, and γ-ray intensities. It was determined that 196Aum2 decays with a half-life of 9.603 h ± 0.23%. The relative intensities of the γ rays emitted during its decay were also measured, and an absolute decay branch of 0.3352 ± 2.9% was determined for the emission of the 188.2 keV photon, which arises from a nuclear transition whose multipolarity is predominantly M1. Properties of other products arising in the reaction of 197Au with fast neutrons were measured, as were selected production cross sections. The 196Aum2/196Aug isomer ratio measured in the 197Au(n, 2n) reaction at 14.1 MeV was found to be 0.0731 ± 2.6%.

Comparison between measurement and calculations for a 14 MeV neutron water activation experiment

The nuclear heat loads due to gamma rays emitted from the decay of 16N and delayed neutrons from17N, generated by the activation of water in cooling circuits, are critical for ITER design. The assessment of nuclear heating from activated water is complex; it requires temporal and spatial dependent transport and activation calculations taking into account variation of irradiation, water flow conditions and cooling circuits’ parameters. A water activation experiment has been recently conducted at the14 MeV Frascati Neutron Generator (FNG) in order to validate the methodology for water activation assessment used for ITER and to reduce the safety factors applied to the calculation results, which have a large impact on the schedule, commissioning and licensing. Water circulating inside an ITER First Wall (FW) mock-up was irradiated with 14 MeV neutrons and then measured using a large CsI scintillator detector. The system consists of a closed water loop where the cooling water, transiting through an ITER FW mock-up, is irradiated by FNG. The induced 16N activity via 14 MeV neutrons interactions with 16O via the 16O(n,p)16N reaction is measured in a dedicated counting station via an expansion volume. The water then passes to a much larger holding delay tank, and after several 16N half-lives decay time, it is then recirculated and exposed again to neutrons in the ITER First Wall (FW) mock-up. The measured 16N activity is obtained measuring the emitted characteristic 6.13 and 7.12 MeV gamma-rays. Calculations were performed in an accurate model of the FW mock-up using the MCNP Monte Carlo code and FENDL-3.1 nuclear data library to obtain the predicted flux impinging on the water. The EASY-2007 inventory code was used to predict the 16N activity. In this work, a comparison between measurements and calculations is reported together with associated uncertainty analysis.

Measurement of (n, f) and (n, xn) cross sections with surrogate reaction method

Surrogate reaction method is an important approach to overcome the difficulties meet in the direct measurement of neutron induced nuclear reaction. The current existing surrogate reactions generally employ the peripheral reactions such as inelastic excitation and transfer reaction where the involved angular momenta are much larger than the neutron capture reaction, which causes a difficulty in theoretical correction of spin of compound nucleus. We proposed to use capture reaction of light charged particle as the surrogate reaction, thus the spin distributions of compound nucleus in two reactions are quite similar and therefore the spin correction is not strongly desired. Based on this idea, the 239Pu(n, f) and (n, 2n) cross sections were successfully extracted by using 236U(α,, f) and (α, 2n) reactions as the surrogate reactions. The well coincidence of the present results with the data of ENDFB7 within the error bars shows the reliability of the proposed surrogate capture reaction method.

Activation of the Cooling Circuit Water of the Cyclone 18/9-HC Cyclotron during the Production of 18F

Processes of accumulation of radionuclides in the cooling circuit water of the Cyclone 18/9-HC cyclotron were studied under proton irradiation of the Nirta Fluor target. It is shown that the nature of the water activation reactions in the cooling circuit and the equivalent dose rate from the equipment of the system significantly depend on the dose accumulated by the target. The main source of radionuclides in the cooling circuit water is the 16O(n,p)16N reaction. In targets with high absorbed radiation doses associated with deformation of the target entrance window, the proton-induced 14N(p,α)11C and 18O(p,n)18F reactions take place. Fluoride 18F−, carbonate 11CO32−, and hydrocarbonate H11CO3− anions formed in these reactions precipitate on the ion-exchange resin during the circulation of water in the cooling circuit. It has been ascertained that the average annual radiation exposure dose for the cyclotron operator from the water activation products in the cooling circuit does not exceed 1% of the annual staff exposure limit. Recommendations are given for the application of engineering barriers in the design and reconstruction of nuclear medicine facilities for the case of water leaks from the cyclotron cooling circuit.

Development of an autonomous solvent extraction system to isolate astatine-211 from dissolved cyclotron bombarded bismuth targets

Cyclotron-produced astatine-211 (211At) shows tremendous promise in targeted alpha therapy (TAT) applications due to its attractive half-life and its 100% α-emission from nearly simultaneous branched alpha decay. Astatine-211 is produced by alpha beam bombardment of naturally monoisotopic bismuth metal (209Bi) via the (α, 2n) reaction. In order to isolate the small mass of 211At (specific activity = 76 GBq·µg−1) from several grams of acid-dissolved Bi metal, a manual milliliter-scale solvent extraction process using diisopropyl ether (DIPE) is routinely performed at the University of Washington. As this process is complex and time consuming, we have developed a fluidic workstation that can perform the method autonomously. The workstation employs two pumps to concurrently deliver the aqueous and organic phases to a mixing tee and in-line phase mixer. The mixed phases are routed to a phase settling reservoir, where they gravity settle. Finally, each respective phase is withdrawn into its respective pump. However, development of a phase boundary sensor, placed in tandem with the phase settling reservoir, was necessary to communicate to the system when withdrawal of the denser aqueous phase was complete (i.e., the intersection of the two phases was located). The development and optimization of the autonomous solvent extraction system is described, and the 211At yields from several ~1.1 GBq-level 211At processing runs are reported.

Neutron detection performance of gallium nitride based semiconductors

Neutron detection is crucial for particle physics experiments, nuclear power, space and international security. Solid state neutron detectors are of great interest due to their superior mechanical robustness, smaller size and lower voltage operation compared to gas detectors. Gallium nitride (GaN), a mature wide bandgap optoelectronic and electronic semiconductor, is attracting research interest for neutron detection due to its radiation hardness and thermal stability. This work investigated thermal neutron scintillation detectors composed of GaN thin films with and without conversion layers or rare-earth doping. Intrinsic GaN-based neutron scintillators are demonstrated via the intrinsic 14N(n, p) reaction, which has a small thermal neutron cross-section at low neutron energies, but is comparable to other reactions at high neutron energies (>1 MeV). Gamma discrimination is shown to be possible with pulse-height in intrinsic GaN-based scintillation detectors. Additionally, GaN-based scintillation detector with a 6LiF neutron conversion layer and Gd-doped GaN detector are compared with intrinsic GaN detectors. These results indicate GaN scintillator is a suitable candidate neutron detector in high-flux applications.

Isomeric yield ratio of 196m, gAu in the 197Au(n, 2n) reaction with fast neutron based on the 9Be(p, n) reaction

The isomeric yield ratios (IR) of 196m, gAu in the 197Au(n, 2n) reaction at the average neutron energies ($ \langle E_{n}\rangle$) of 14.4, 21.8 and 29.5 MeV have been measured by using the off-line gamma-ray spectrometric technique. The neutron beams were obtained by using the 9Be(p, n) reaction with the proton energies of 25, 35 and 45 MeV from the MC-50 cyclotron at KIRAMS. The IR values at different neutron energies were also calculated from the cross sections values based on TENDL-2017 library and are found to be in agreement around 10–18 MeV but not at higher energy. The IR values of 196m, gAu at the neutron energies of 21.8 and 29.5 MeV have been measured for the first time. The present data along with the literature data at other energies in the 197Au(n, 2n) reaction are compared with the similar data in the 197Au($ \gamma$, n) reaction to examine the role of entrance channel parameters and occurrence of non-compound or pre-equilibrium process at higher projectile energy.

12C(15N, 14C)13N reaction at 81 MeV. Competition between one and two particle transfers

Angular distributions at both forward and backward angles for the 12C(15N, 14C)13N reaction were measured at the energy Elab(N15)=81 MeV for ground and exited states of 14C and 13N nuclei by detecting both particles at forward angles. Coupled-reaction-channels (CRC) calculations using spectroscopic amplitudes calculated within the translational invariant shell model (TISM) for transferring nucleons and clusters were carried out. These calculations describe the origin of the observed highly oscillatory large angle data as two neutron transfer while the less structured forward angle data is by proton transfer. Multi-step and other nucleon transfers were found to give small contributions to the current data.

Механізми реакції 12С(15N,14С)13N при енергії 81 МеВ та взаємодія ядер 14С + 13N

Механізми реакції 12С(15N,14С)13N при енергії 81 МеВ та взаємодія ядер 14С + 13N

Spectroscopy of low-spin states in Dy157 : Search for evidence of enhanced octupole correlations

Low-spin states of 157Dy have been studied using the JUROGAM II array, following the 155Gd ({\alpha}, 2n) reaction at a beam energy of 25 MeV. The level scheme of 157Dy has been expanded with four new bands. Rotational structures built on the [523]5/2- and [402]3/2+ neutron orbitals constitute new additions to the level scheme as do many of the inter- and intra-band transitions. This manuscript also reports the observation of cross I- to (I-1)- and I- to (I-1)+ E1 dipole transitions inter-linking structures built on the [523]5/2- (band 5) and [402]3/2+ (band 7) neutron orbitals. These interlacing band structures are interpreted as the bands of parity doublets with simplex quantum number s = -i related to possible octupole correlations.

Photoactivation experiment of 197Au(γ, n) performed with 9.17-MeV γ-ray from 13C(p, γ)14N**Project supported by the National Natural Science Foundation of China (Grant No. 11655003).

High energy γ-ray can be used for nuclear waste transmutation by using the giant dipole resonance (GDR). The photonuclear reaction 197Au(γ, n) is known as a standard for studies on photoactivation experiments. The previous experiments on 197Au(γ, n) have been performed with bremsstrahlung, positron annihilation in flight or laser Compton scattering γ-ray. In this work, a new mono-energetic γ-ray source based on 13C(p, γ)14N reaction is used to measure the cross section of 197Au(, n) and the measured value is compared with the results obtained with other ways.

Half-life determination of 77Kr using the reference source method

Samples of 77Kr were produced by (n, 2n) reaction with a DT accelerator, the decay of 77Kr has been tracked by the reference source method with three High-Purity Germanium (HPGe) detectors. Experimental data were recorded at regular time intervals during measurements covering more than 600 min. The determined half-life of 77Kr is 71.25 (42) min, which indicated that the most recent values reported in the 1970s and the value recommended by Evaluated Nuclear Structure Data File (ENSDF) may be biased.

New measurement of thick target yield for narrow resonance at in the 13C()14N reaction**Project supported by the National Natural Science Foundation of China (Grant No. 11655003).

High energy γ-rays can be used in many fields, such as nuclear waste transmutation, flash photographics, and astrophysics. The 13C()14N resonance reaction was used to generate high energy and mono-energetic γ-rays in this work. The thick-target yield of the 9.17-MeV γ-ray from the resonance in this reaction was determined to be (4.7±0.4)/proton, which was measured by a HPGe detector. Meanwhile, the angular distribution of 9.17-MeV γ-ray was also determined. The absolute efficiency of HPGe detector was calibrated using 56Co and 152Eu sources with known radioactive activities and calculated by GEANT4 simulation.

Production of [13N]ammonia from [13C]methanol on a 7.5 MeV cyclotron using 13C(p, n)13N reaction: Detection of myocardial infarction in a mouse model

[13N]Ammonia is commonly produced using 16O(p, α)13N reaction but one of the limiting factor of this reaction is the relatively small nuclear cross-section at proton energies of <10 MeV. An alternative production method using 13C(p, n)13N reaction, which has a higher nuclear cross-section at low proton energies, is more suitable for a preclinical PET imaging facility equipped with a <10 MeV cyclotron. Here, we report a novel method to produce [13N]ammonia from [13C]methanol for preclinical use on a 7.5 MeV cyclotron. A tantalum solution target (80 μl) consisting of a havar window supplied by the cyclotron manufacturer for the production of [18F]fluoride was used without any modifications. The final bombardment parameters were optimized as follow: [13C]methanol concentration in target solution – 10%, bombardment time – 8 min, and beam current – 2.2 μA. These parameters provided doses of [13N]ammonia which were sufficient to conduct preclinical PET imaging studies in a mouse model of myocardial infarction. Under optimized conditions, the operational lifetime of the target was approximately 150 μAmin. Radionuclide identity of the product as 13N was confirmed by measuring the decay half-life and its radionuclide purity was confirmed by γ-ray spectroscopic analysis. Gas chromatography revealed that the final [13N]ammonia dose was not distinguishable from water, showing no traces of methanol. As expected, PET/CT imaging in healthy CD-1 mice indicated the accumulation of [13N]ammonia in myocardial tissue; mice with myocardial infarction created by left ascending coronary ligation showed clear perfusion deficit in affected tissue. This work demonstrates the proof-of-concept of using 13C(p, n)13N reaction to produce [13N]ammonia from [13C]methanol with a <10 MeV cyclotron, and its diagnostic application in imaging cardiac perfusion.

Suprathermal nuclear effects in the solar core: overall view

The present paper completes a series of works on the influence on solar processes of fast charged particles produced in exoergic reactions in the solar core. The general picture of suprathermal effects triggered by the most energetic of them—MeV protons and α-particles—is composed. All reactions in the pp chain and the CNO cycle induced by these particles are examined. It is shown that some opposite suprathermal (p, α) and (α, p) reactions can be balanced, but their rates can exceed the rates of the respective thermal processes, affecting some points of nuclear fusion in the solar core. In particular, the suprathermal channels of p + 17O α + 14N reactions increase the total energy released in these processes by a factor of 1.64, and enhance the mass fractions of 17O and 18O by ∼1–4 times at radii . The same result is also obtained for the 18F abundance, leading to the proportional enhancement of the 18F neutrino emission rate. At the same time, integral characteristics like the total energy production and neutrino generation in the solar core remain unchanged.