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Neutron yield for 250 MeV protons incident on a tungsten target has been measured using the water bath method. The target was made of many randomly placed tungsten grains. Through analyzing the activity of Au foils, the neutron flux distribution in water was obtained. The neutrons slowing down process shows that the neutrons from tungsten have an a...
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Citations
... Our team has been engaged in experimental research in heavy ion nuclear physics [11,12,13,14], to learn more about the fragmentation reaction of 12 C , 30 we have carried out an experiment of 80.5 MeV/u 12 C beam borbarding on C, W, Cu, Au and Pb targets. The energy spectrums and cross-sections of light particles have been measured at 30 • , 60 • and 120 • away from beam. ...
To get the energy spectrum distribution and cross-sections of emitted light charged particles and explore the nuclear reaction, a experiment of 80.5 MeV/u 12C beam bombarding on C, W, Cu, Au, Pb targets has been carried out at Institute of Modern Physics, Chinese Academy of Science. 30, 60 and 120 degree relative to the incident beam have been detected using three sets of telescope detectors. The results indicate that there is a tendency that heavier targets have larger double differential cross-sections and the emitted fragments are more likely to go forward. Besides, the decrease of cross-sections of fragments producing with the increasing emitted angles may follow some kind of pattern.
... Thus, the nuclear properties of tungsten granular target are of crucial importance to the reactor design of CIADS. Experimental neutronics studies of the tungsten granular target bombarded by high energy protons, i.e., neutron yield, neutron leakage and neutron flux distribution measurement, have been carried (Zhang and Zhang, 2015). However, it is still lack of the experimental studies on the tungsten granular target in the reactor core. ...
In this paper, a benchmark experiment of tungsten granular target worth has been performed on the VENUS-II light water zero-power facility of CIAE in Beijing. The reactivity worth of the tungsten granular target was measured and processed as (-1.007±0.096) mk by a period method. In MCNP simulations, three modeling methods of tungsten grains, i.e., the homogeneous, body center and face center models, were used to calculate the tungsten granular target reactivity worth. Through the comparison, the simulated tungsten granular target reactivity worth values with three modeling methods are in good agreement with the experimental result within errors and the maximum C/E and (C-E) deviations are respectively 3.7% and 0.037 mk. By the perturbation analysis in MCNP and the comparison on the cross sections of tungsten, iron and nickel, the negative reactivity worth of tungsten granular target is mainly caused by the tungsten radiation capture reaction channel. It is recommended to adopt the efficient homogeneous modeling method to simulate the tungsten granular target, which establishes a foundation for the systematic integration design of CIADS.
... For CiADS, the primary goal is to achieve the integration of three systems, i.e. a subcritical lead-bismuth reactor, a heavy metal spallation target and an intense-beam proton linac [2]. During the early stages of ADS projects, some experiments [3][4][5][6][7], which coupled the proton accelerator with the spallation target, have been performed by the researchers. However, the experimental studies about the coupling behaviors between the nuclear reactor and the spallation target have been rarely investigated. ...
Measurement of a cylindrical tungsten target reactivity worth has been performed on the light water zero-power reactor of VENUS-II at China Institute of Atomic Energy (CIAE) in order to verify the neutron evaluated data related to the engineering design of Chinese initiative Accelerator Driven Systems (CiADS). The reactivity worth of the tungsten target was measured and processed as -1.234±0.114mk by a period method. The experimental result was compared with the simulation ones calculated by MCNP with five different libraries, i.e., ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0, CENDL-3.1 and JEFF-3.2. By comparing the results of experiment and simulation, the simulated results from ENDF/B-VII.0, JENDL-4.0 and JEFF-3.2 are higher than the experimental result, however that from CENDL-3.1 is lower. The result from ENDF/B-VII.1 library shows better agreement with the experiment one and the relative deviation is less than 2%. Through the analysis of the differences of the results, non-tungsten elements cross sections in the ENDF/B-VII.1 mainly affect the tungsten radiation capture and elastic scattering reaction rates in the energy range of 10 ⁻⁹ -10 ⁻⁷ MeV, which results in a better simulated tungsten target reactivity worth value. Therefore, it is recommended that the tungsten target reactivity worth should be calculated with the ENDF/B-VII.1.
... In the circulation loop of the grains of the DGT, a magnetic lifting device instead of mechanical one will be adopted to act as the grains elevator. To meet the requirement on the grains material of the magnetic lifting, the tungsten alloy with 2% Fe and 5% Ni will be used [5]. The adoption of the alloy can overcome the brittleness of the solid grains at the same time. ...
... The estimated neutron flux distribution does not differ too much compared with the one produced by using lead as target: the estimated yield of reaction was 2.02 ± 0.15 neutron for every proton. The only difference is that tungsten is more dense than lead, so the protons stopping power is higher and along the axis of cylinder the flux is lower [46]. ...
Neutron beams serve an important role in many research fields, including nuclear energy, material science and medical applications. Nowadays, the neutron fluxes are mainly provided by research reactors or by conventional accelerators. These latter accelerate light ions against proper converters, in order to exploit nuclear reactions of the types (p,n), (p,p’,n) and (d,n). The neutron fluxes made available from these conventional sources are exploited in order to perform techniques like the crystal lattice analysis, the “neutron activation analysis”, the neutron radiography or the “boron neutron capture therapy” (an innovative medical application of the neutron beam). Until recently, the experimental access to a high neutron flux was exclusive to reactor and accelerator-based facilities. In the past few years, the availability of tabletop particle sources based on high intensity lasers has enabled the realization of an alternative high flux neutron generators. Laser-driven ion acceleration relies on ultra-intense (I > 10^18 W/cm^2 ), ultra-short (∼10 fs - ps) laser pulses interacting with solid targets. Employing a compact table-top laser (∼ tens of TW of power), it is possible to generate proton bunches characterized by an exponential energy spectrum with maximum energy of some MeV. These energies are suitable for inducing proton-neutron reactions in appropriate targets. Beryllium or lithium are the two main converters suggested by the literature, because of the high values of the (p,n) cross section in this range of energy. If compared with the conventional neutron sources, laser-driven sources should offer many advantages: the compactness, which leads to more maneuverability and the possibility to develop a portable sources; the simplification of the experimental set-up; the reduction of radioprotection issues; the reduction of the costs (in particular if compared with the construction and the operation of a nuclear reactor). The purpose of this thesis work is a numerical investigation, performed with the Monte-Carlo code Geant4, on how the variations of the physical parameters of a laser-driven system could affect the generation of neutrons. In particular, in the simulations implemented, low energy proton beams ( ∼ MeV) impinge on beryllium or lithium converters. Since the numerical tool is essential to the development of the work, a detailed investigations of its behaviour and a benchmark between its outputs and the experimental or theoretical data from literature is carried out. After ensuring about the reliability of the code, comparisons between monoenergetic and laser-driven proton beam impinging on the converters are carried out. As a parameter of comparison, the mean energy of the exponential energy spectrum of the laser-driven proton beam is set equal to the energy of the monoenergetic beam. Considering the same number of protons impinging on the converters, a comparison between the neutron yields, energy spectra and angular distributions arising from the two cases is performed. Moreover, a study of how the converter thickness influences the neutron production is accomplished, with the aim of searching for the optimum solution. Finally, considering the obtained neutron fluxes, a list of possible applications that it could be realistic to realize with laser-driven sources are presented, also in sight of the future improvement of the technique.
... We have simulated this production with GEANT4 and FLUKA and we have compared our results with experimental data at various energies up to 100 MeV [39,40] and also with the simulations of Ref. [41] at 250 MeV. In general we have found that the GEANT4 simulations yield 10-20% less neutrons than experimental data and the FLUKA simulations 20-40% less, whereas we found better than 1% agreement with the simulations of Ref. [41]. ...
... We have simulated this production with GEANT4 and FLUKA and we have compared our results with experimental data at various energies up to 100 MeV [39,40] and also with the simulations of Ref. [41] at 250 MeV. In general we have found that the GEANT4 simulations yield 10-20% less neutrons than experimental data and the FLUKA simulations 20-40% less, whereas we found better than 1% agreement with the simulations of Ref. [41]. The deficit in neutron production in FLUKA arises entirely at low energies. ...
Several experimental collaborations worldwide intend to test sterile neutrino models by measuring the disappearance of antineutrinos produced via isotope decay at rest (IsoDAR). The most advanced of these proposals have very similar setups, in which a proton beam strikes a target yielding neutrons which are absorbed by a high isotopic purity 7Li converter, yielding 8Li whose resulting decay yields the antineutrinos. In this note, we use FLUKA and GEANT4 simulations to investigate three proposed modifications of this standard proposal. In the first, the 7Li is replaced with 7Li compounds including a deuterium moderator. In the second, a gap is placed between the target and the converter to reduce the neutron bounce-back. Finally, we consider cooling the converter with liquid nitrogen. We find that these modifications can increase the antineutrino yield by as much as 50 percent. The first also substantially reduces the quantity of high purity 7Li which is needed.
This work reports the production cross-section data for twenty-five radionuclides produced by 80.5MeV/u carbon ions impinging on the tungsten target. The data were obtained by using the off-line gamma spectroscopy method. We calculated the cross sections for the production of residual nuclides using the PHITS Monte-Carlo code and compared them with measured results. We also studied the calculated results of the tungsten target bombarded by 250MeV protons. Generally, the PHITS calculations give a good tendency of isobaric yield for both heavy ions and protons. The experimental data will be useful for understanding the reaction mechanism and benchmarking Monte-Carlo particle transport models.
As a beta emitter, samarium-153 (Sm-153) has been used in palliative cancer therapy. One of the widely employed methods to produce Sm-153 is by irradiating enriched Sm-152 target with thermal neutrons via ¹⁵²Sm(n,γ)¹⁵³Sm nuclear reaction. In this work, Sm-153 radioisotope production is theoretically proposed using secondary fast neutrons bombarded to enriched Eu-153 target via ¹⁵³Eu(n,p)¹⁵³Sm nuclear reaction. The secondary fast neutron flux calculation was performed using the PHITS 3.20 code, in which, in the simulation, a 10-MeV proton beam was bombarded to a 0.3 mm thick primary titanium (Ti) target to generate secondary fast neutrons. The fast neutrons were then bombarded to the enriched Eu-153 target to produce Sm-153. Based on the PHITS simulation results, the total fast neutron flux generated from the 10-MeV proton bombarded Ti target was 2.16x10¹¹ n/cm²s. With such a neutron flux, Sm-135 radioactivity yield was estimated to be 3.19 kBq/µAh. The most possible beta-emitting radioisotope impurity generated during Sm-153 production was Eu-154, whereas the most possible stable isotope that could be produced during Sm-153 production was Sm-152. This theoretical study highlights that secondary fast neutrons as a result of 10-MeV proton bombardment can be used to produce Sm-153 radioisotope.
To get the energy distributions and cross sections of emitted light charged particles, and to explore the nuclear reaction, experiments of 80.5 MeV/u ¹²C beam bombarding on C, Cu, W, Au, Pb targets have been carried out at Institute of Modern Physics, Chinese Academy of Sciences. 30°, 60°, and 120° relative to the incident beam have been detected using three sets of telescope detectors. The method of ΔE−ΔE−E was used for particle identification. Results indicate that heavier targets have larger double differential cross sections, and the emitted fragments tend to go forward. Besides, the decrease of cross sections of fragments produced with the increasing emitted angles follows a kind of pattern.
As a beta and positron emitter, copper-64 (Cu-64) has been coined a theranostic agent in nuclear medicine. Copper-64 is generally produced by bombarding a nickel-64 target with a proton beam via ⁶⁴ Ni(p,n) ⁶⁴ Cu nuclear reaction. In this work, secondary fast neutrons are proposed to produce Cu-64 radioisotope via ⁶⁴ Zn(n,p) ⁶⁴ Cu nuclear reaction. The secondary fast neutrons were produced by a 10 MeV proton-irradiated primary titanium (Ti) target simulated using the PHITS 3.16 code. In the simulation, the Ti target thickness was varied from 0.01 to 0.1 cm to obtain the optimum secondary fast neutron flux, which was calculated in the rear, radial, and front directions. The Cu-64 radioactivity yield was then computed using the TENDL 2019 nuclear cross-section data. Also, the expected radioactive impurities during Cu-64 production were predicted. The simulation results indicated that the total fast neutron flux resulted from the 10-MeV proton bombarded Be target was 1.70x10 ¹² n/cm ² s. The maximum integrated Cu-64 radioactivity yield was 2.33 MBq/µAh when 0.03 cm thick Ti target was shot with 10-MeV protons. The most significant impurities predicted during the bombardment were radioactive isotopes e.g., Co-61, and Zn-65, with the total radioactivity yield estimated to be 0.28 Bq/µAh.
