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DOE OSTI2018

Multiparticle Photonuclear Reactions in the p-Process at Temperatures between 1 and 10 GK

The role of (γ, 2n), (γ, pn), and (γ, 2p) multiparticle photonuclear reactions in processes that lead to the nucleosynthesis of p-nuclides is considered. The library of rates of multiparticle photonuclear reactions that was developed for the temperature range between 1 and 10 GK and which is intended for use in stellar-evolution models and in calculations of nucleosynthesis is described. A simulation of the p-process in the course of an SN-IIa core-collapse event reveals that, within the scenario being considered, a dominant effect of multiparticle photonuclear reactions consists in enhancing the rate of photodisintegration of p-nuclides at temperatures above 6 to 7 GK.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2014

Photonuclear reaction based high-energy x-ray spectrometer to cover from 2 MeV to 20 MeV

A photonuclear-reaction-based hard x-ray spectrometer is developed to measure the number and energy spectrum of fast electrons generated by interactions between plasma and intense laser light. In this spectrometer, x-rays are converted to neutrons through photonuclear reactions, and the neutrons are counted with a bubble detector that is insensitive to x-rays. The spectrometer consists of a bundle of hard x-ray detectors that respond to different photon-energy ranges. Proof-of-principle experiment was performed on a linear accelerator facility. A quasi-monoenergetic electron bunch (N{sub e} = 1.0 × 10{sup −6} C, E{sub e} = 16 ± 0.32 MeV) was injected into a 5-mm-thick lead plate. Bremsstrahlung x-rays, which emanate from the lead plate, were measured with the spectrometer. The measured spectral shape and intensity agree fairly well with those computed with a Monte Carlo simulation code. The result shows that high-energy x-rays can be measured absolutely with a photon-counting accuracy of 50%–70% in the energy range from 2 MeV to 20 MeV with a spectral resolution (Δhν/hν) of about 15%. Quantum efficiency of this spectrometer was designed to be 10{sup −7}, 10{sup −4}, 10{sup −5}, respectively, for 2–10, 11–15, and 15–25 MeV of photon energy ranges.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Formation of medical radioisotopes {sup 111}In, {sup 117m}Sn, {sup 124}Sb, and {sup 177}Lu in photonuclear reactions

The possibility of the photonuclear production of radioisotopes {sup 111}In, {sup 117m}Sn, {sup 124}Sb, and {sup 177}Lu is discussed. Reaction yields were measured by the gamma-activation method. The enriched tin isotopes {sup 112,} {sup 118}Sn and Te and HfO{sub 2} of natural isotopic composition were used as targets. The targets were irradiated at the linear electron accelerator of Alikhanian National Science Laboratory (Yerevan) at the energy of 40 MeV. The experimental results obtained in this way reveal that the yield and purity of radioisotopes {sup 111}In and {sup 117}mSn are acceptable for their production via photonuclear reactions. Reactions proceeding on targets from Te and HfO{sub 2} of natural isotopic composition and leading to the formation of {sup 124}Sb and {sup 177}Lu have small yields and are hardly appropriate for the photoproduction of these radioisotopes even in the case of enriched targets.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions

Prompt and β-delayed fission observables, such as the average number of prompt and delayed neutrons, the independent and cumulative fission product yields, and the prompt γ-ray energy spectra for the photonuclear reactions on 235,238 U and 239 Pu, are calculated with the Hauser-Feshbach fission fragment decay (HF 3 ⁢D) model and compared with available experimental data. Further, in the analysis of neutron-induced fission reactions to the case of photo-induced fission, an excellent reproduction of the delayed neutron yields supports a traditional assumption that the photo fission might be similar to the neutron-induced fission at the same excitation energies regardless of the spin and parity of the fissioning systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2016

SU-F-T-376: The Efficiency of Calculating Photonuclear Reaction On High-Energy Photon Therapy by Monte Carlo Method

Purpose: Secondary-neutrons having harmful influences to a human body are generated by photonuclear reaction on high-energy photon therapy. Their characteristics are not known in detail since the calculation to evaluate them takes very long time. PHITS(Particle and Heavy Ion Transport code System) Monte Carlo code since versions 2.80 has the new parameter “pnimul” raising the probability of occurring photonuclear reaction forcibly to make the efficiency of calculation. We investigated the optimum value of “pnimul” on high-energy photon therapy. Methods: The geometry of accelerator head based on the specification of a Varian Clinac 21EX was used for PHITS ver. 2.80. The phantom (30 cm * 30 cm * 30 cm) filled the composition defined by ICRU(International Commission on Radiation Units) was placed at source-surface distance 100 cm. We calculated the neutron energy spectra in the surface of ICRU phantom with “pnimal” setting 1, 10, 100, 1000, 10000 and compared the total calculation time and the behavior of photon using PDD(Percentage Depth Dose) and OCR(Off-Center Ratio). Next, the cutoff energy of photon, electron and positron were investigated for the calculation efficiency with 4, 5, 6 and 7 MeV. Results: The calculation total time until the errors of neutron fluence become within 1% decreased as increasing “pnimul”. PDD and OCR showed no differences by the parameter. The calculation time setting the cutoff energy like 4, 5, 6 and 7 MeV decreased as increasing the cutoff energy. However, the errors of photon become within 1% did not decrease by the cutoff energy. Conclusion: The optimum values of “pnimul” and the cutoff energy were investigated on high-energy photon therapy. It is suggest that using the optimum “pnimul” makes the calculation efficiency. The study of the cutoff energy need more investigation.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2014

SU-E-T-26: A Study On the Influence of Photonuclear Reactions On the Biological Effectiveness of Therapeutic High Energy X-Ray Beam

Purpose: Photons from a modern high-energy therapeutic linear accelerator used in X-ray radiotherapy causes photonuclear reactions in an accelerator or patient's body. The aim of this study is to evaluate the biological effectiveness including these particles by Microdosimetric Kinetic Model (MKM) based on microdosimetry. Methods: A linear accelerator operating at 15 MV was used. CR-39 was used to obtain LET spectra of secondary ions selectively, as CR-39 is regarded insensitive to photons. CR-39 was put on the central axis of the X-ray beam at depths of 0, 5 and 10 cm in plastic phantom at a source to detector distance of 100 cm. Pits formed by the traversal of ions were etched then analyzed to obtain restricted LET distribution. Frequency-mean and dose-mean lineal energy was evaluated from the relationship between the restricted LET and the lineal energy required to evaluate the biological effectiveness by MKM. The relationship was calculated by Monte Carlo simulations with GEANT4. Results: Restricted LET distributions of secondary particles showed broad distributions that decreases exponentially with increasing LET. Frequency-mean and dose-mean lineal energy were determined uniquely within the scope of the energies of secondary particles generated from photons of 15 MeV. The frequency-mean lineal energies at the depth of 0, 5 and 10 cm were 15.1, 16.0 and 19.7 keV/μm respectively, and the dose-mean lineal energies were 18.6, 20.5 and 19.6 keV/μm, respectively. RBE of secondary particles for HSG cell evaluated by MKM was about 2.0 at all depths, and RBE of all particles including photons was evaluated 1.0. Conclusion: We investigated the biological effectiveness of secondary particles by photonuclear reactions. The method to evaluate RBE by MKM was established with measurements and simulations. However, the influence of these secondary ions on RBE was found negligible in the entire biological effectiveness of the high-energy X-ray. This study has been supported by JSPS KAKENHI Grant Number 25861144.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2017

Production of medical {sup 99m}Tc isotope via photonuclear reaction

{sup 99m}Tc with a 6 hour half-life is one of the most important medical isotopes used for the Single-Photon Emission Computed Tomography (SPECT) inspection in hospitals of US, Canada, Europe and Japan. {sup 99m}Tc isotopes are extracted by the milking method from parent {sup 99}Mo isotopes with a 66 hour half-life. The supply of {sup 99}Mo isotopes now encounters a serious crisis. Hospitals may not suitably receive {sup 99}Mo medical isotopes in near future, due to difficulties in production by research nuclear reactors. Many countries are now looking for alternative ways to generate {sup 99}Mo isotopes other than those with research reactors. We discuss a sustained availability of {sup 99m}Tc isotopes via the {sup nat}Mo(γ, n) photonuclear reaction, and discuss to solve technical problems for extracting pure {sup 99m}Tc isotopes from other output materials of photonuclear reactions.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2018

Development of a Method for Measurement of Photonuclear-Reaction Cross Sections with the Aid of Simulated Quasimonoenergetic-Photon Spectra

A procedure for measuring photonuclear-reaction cross sections by employing the method of quasimonochromatization of the bremsstrahlung photon spectrum is developed. This procedure permits determining reaction cross sections via measuring the reaction yield at three fixed values of the electron energy. The procedure is equivalent to measuring the cross section in question for quasimonochromatic photons. Bremsstrahlung-photon spectra are obtained using state-of-the-art simulation means involving the GEANT4 code as applied to a specific experiment with allowance for its geometry, target thicknesses, electron-beam parameters, etc. The results obtained by simulating quasimonochromatic distributions of bremsstrahlung photons are presented for experiments at the LUE-8-5 linear electron accelerator of Institute for Nuclear Research (Moscow, Russian Academy of Sciences). These results are found to be in good agreement with the experimental energy distribution of the cross section for the reaction {sup 111}Cd(γ, γ') in the energy range between 5 and 8 MeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Photonuclear reactions on titanium isotopes

The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes {sup 47,48,49,50}Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes {sup 49,50}Ti.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Study of Photonuclear Reactions near the Threshold at an Electron Accelerator and a Femtosecond Laser

A brief review of the works devoted to studying the photonuclear reactions near the threshold at the LUE-8.5 MeV linear electron accelerator of the Institute for Nuclear Research of the Russian Academy of Sciences and the terawatt femtosecond laser complex of the International Laser Center at Moscow State University is provided. The main focus of attention is the simulation of the experiments using the GEANT-4 code. This allowed us to compare the possibilities of different methods and determine the main directions of future research.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Photonuclear reactions on the cadmium isotopes {sup 106,108}Cd at the bremsstrahlung endpoint energy of 55.5 MeV

The gamma-activation technique was used to measure the absolute yields of photonuclear reactions on the cadmium isotopes {sup 106,108}Cd. The results obtained in this way were compared with the results of the calculations based on the statistical model. For reactions on the isotope {sup 108}Cd, agreement between these theoretical and experimental results is good, but the experimental ratio of the yields of photoproton and photoneutron reactions on the isotope {sup 106}Cd differs substantially from its theoretical counterpart. The results of our present study are discussed from the point of view of the production of bypassed nuclei in the p-process of nucleosynthesis.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1989

Calculation of two-neutron multiplicity in photonuclear reactions

The most important particle emission processes for electromagnetic excitations in nucleus-nucleus collisions are the ejection of single neutrons and protons and also pairs of neutrons and protons. Methods are presented for calculating two-neutron emission cross sections in photonuclear reactions. The results are in a form suitable for application to nucleus-nucleus reactions.

Norbury, John W.↗

NASA NTRS1990

Calculation of two-neutron multiplicity in photonuclear reactions

Norbury, John W.↗

DOE OSTI2024

Photonuclear Reaction Types Map to ENDF Reaction Type Numbers MT

In the ENDF format, photonuclear cross secCons are stored in File = 3 under the NSUB = 0 sub-library. The type of reacCon data and the products resulCng from that reacCon are idenCfied by an integer number from 1 to 999, called MT number. However, the ENDF manual is wriPen with a strong focus on neutron induced reacCons and the meaning of MT numbers in the context of photonuclear reacCons can be at Cmes confusing and the assessment of evaluated photonuclear data may require summing various MT numbers to obtain the desired cross secCons to compare with experimental data. An important step in assessing the quality of evaluated data for photonuclear cross secCons is therefore to clarify the mapping between MT numbers and the nomenclature used to describe photonuclear reacCons in the literature. The intent of this document is to provide such a map.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

A Systematic Study of Photonuclear Reactions for Isotope Production

Overview of RENEW project that facilitates the education and mentorships of underrepresented students in isotope production research.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2021

Cross Section Measurements of Photonuclear Reaction Pathways Towards Promising Medical Radioisotopes

Project Objectives: The goal of this project was to generate data relevant to radioisotope production while developing innovative technologies that foster and enhance novel production of radioisotopes, and, also, while providing opportunities for cultivating and training future generations of scientists. This work has provided the foundation for methodologies for determination of photonuclear cross sections over multiple energies in a single irradiation. Simultaneously, the feasibility of electron LINAC production of several in-demand radioisotopes such as 47 Sc, 67 Cu, 77 As, and 186 Re has been demonstrated. To accomplish these objectives a collaboration was formed between two complimentary facilities, the Low Energy Accelerator Facility (LEAF) at Argonne National Laboratory and the High Intensity Gamma-ray Source (HIGS) at Triangular Universities Nuclear Laboratory (TUNL). The involvement of the research group from North Carolina Central University gave students at this Historically Black University experience in forefront nuclear-physics research relevant to addressing a high-priority interdisciplinary issue. Project Description: HIGS provides a nearly monoenergetic gamma-ray beam by intra-cavity Compton backscattering of free-electron photons from electrons circulating in a storage ring. This beam can be collimated to produce a very precise energy beam. If the beam is un-collimated a calculated and precise energy spread of the beam occurs radially. The γ-flux can be evenly distributed over the radial distribution of energy and used to perform activation experiments on concentric ring targets. Thus providing multiple energy ranges in a single irradiation. Each concentric ring target can be counted separately in order to determine activation at the given energy and successively be correlated to the activation cross section. Targets were activated to determine production feasibility using electron beams at LEAF. Potential Impact: The Nuclear Science Advisory Committee recently named production of radioisotopes with electron LINACs as one of the most compelling and largest-impact opportunities for the production of high specific activity radioisotopes. Improving the photonuclear cross sectional data base with experimentally verified results will greatly enhance a researcher’s ability to rationalize electron LINAC production routes towards desired radioisotopes. This work will provide the foundation for methodologies for determination of photonuclear cross sections over multiple energies and multiple targets in a single irradiation. The techniques developed in this project will enable future studies to continue verifying theoretically predicted photonuclear cross section with experimental results. These data will also enable adaptation of models and support more precise theoretical calculation of photonuclear cross sections. This research will involve undergraduates, graduate students, and post-docs to give them a valuable research experience leading towards the next generation of scientists in the field of medical isotopes.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2022

Exploring rapid chemical separations of Sc-47 produced from photonuclear reactions on natural vanadium targets

Scandium-47 ( 47 Sc) production via bremsstrahlung irradiation of natural vanadium targets offers significant advantages for producing high purity 47 Sc; this work evaluates several rapid dissolution and chemical separation techniques for recovering high purity 47 Sc from irradiated vanadium. Here, techniques developed are combined into a simple, gram-scale, semi-automated target processing system that enables 47 Sc recovery from irradiated vanadium targets with chemical yields as high as 93 ± 3% and 47 Sc/V separation factors of 6 ± 3 ·10 11 within 90 min total processing times. Future research into H 2 O 2 resistant separation techniques and their applicability for direct process coupling to chelation are recommended.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2014

Photonuclear reaction studies at HIγS: Developing the science of remote detection of nuclear materials

Development of gamma-ray beam interrogation technologies for remote detection of special nuclear materials and isotope analysis requires comprehensive databases of nuclear structure information and gamma-ray induced nuclear reaction observables. Relevant nuclear structure details include the energy, spin and parity of excited states that have significant probability for electromagnetic transition from the ground state, i.e, the angular momentum transferred in the reaction is Δl ≤ 2. This talk will report recent Nuclear Resonance Fluorescence (NRF) measurements to identify and characterize new low-spin states in actinide nuclei at energies from 1 to 4 MeV, which is the energy range most important for remote analysis methods. Here, these measurements are carried out using the nearly mono-energetic linearly polarized gamma-ray beam at the High Intensity Gamma-ray Source (HIγS) at the Triangle Universities Nuclear Laboratory. Also, studies of the (γ, n) reaction on a variety of nuclei with linearly polarized beams at HIγS indicate that this reaction might be used to discern between fissile and non-fissile materials. This work will be described. In addition, an overview will be given of a concept for a next generation laser Compton-backing scattering gamma-ray source to be implemented as an upgrade to increase the beam intensity at HIγS by more than an order of magnitude.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗