Photonuclear Reaction Data Research Articles

DIGITAL STUDY OF THE 14N(γ,2α)6Li REACTION

A digital measurement technique of points coordinates along the tracks was developed for the stereo frame photonuclear reaction data bank created in KIPT. The main procedure is the analysis of pixel intensity in the area of tracks. The 14N(γ,2α)6Li reaction was chosen as a test reaction for measurement. A kinematic scheme for calculating the physical parameters of the reaction was created assuming a two-particle decay mode with the formation of an intermediate excited state. Experimental data and kinematic calculation were compared.

A comparison of calculated β-decay half-lives with photonuclear reaction data and other experiments

We try to give a comparison of the calculated Gamow–Teller [Formula: see text]-decay half-lives for [Formula: see text], [Formula: see text] and [Formula: see text] nuclei with the experimental ones obtained from ([Formula: see text],p), ([Formula: see text],n) and (n,[Formula: see text]) reactions, respectively. The calculations are performed within the framework of quasi-particle phonon nuclear model. The nucleon–nucleon interaction potential is included according to Pyatov’s restoration method. The calculated decay half-lives are also compared with available experimental data in the literature.

Investigation of Double Differential Cross Sections of (γ,p) Reaction for12C Nuclei

Photonuclear reaction data, is important for basic and applied research. In additional to this, double differential data is especially vital in the field of nuclear medicine. The increase in the number of patients, admitted for treatment of cancer with heavy ions, poses a serious problem in terms of the risk of secondary cancer, as a result of exposure to particles of different energy and angle values, released after the nuclear reaction. The main point here is the possibility of damaging organs other than the treated one by the radiation generated in the reactions during the heavy ion therapy. Based on this, in order to assess the risk of secondary cancer the investigations of the double differential cross sections of reaction are required. Double differential cross sections of (γ,p) photonuclear reaction for C nuclei were calculated as functions of incoming photon energy and angle. Nuclear reaction simulation program TALYS 1.2 was used in the calculations. The calculated cross sections were compared with both the experimental cross sections and the evaluated cross sections available in literature.

Angular Distribution of Bremsstrahlung from Copper and Tungsten Targets Bombarded by 18, 28, and 38MeV Electrons

We measured the angular distribution of bremsstrahlung photons between 0 and 120 degrees from copper and tungstentargets bombarded by 18, 28, and 38MeV electrons at the electron linac of Hokkaido University. Activation detectors and two types of dosimeters were applied for the measurement. The measured results were compared with those calculated with the Monte Carlo code MCNP5 to verify the calculated results. The calculated results of both the reaction rates and ambient dose equivalent rates gave good agreement with the measured ones in the case of 18MeV electrons. A good agreement between the measurement and calculation was also observed for relative angular distributions of dose rates from 38MeV electrons; however, the calculation overestimated the measured data by a factor of 1.2 to 2.0. To achieve further accuracy of calculation, improvement of photonuclear reaction data and absorbed dose measurement are necessary for bremsstrahlung radiation dosimetry.

Angular Distribution of Bremsstrahlung from Copper and Tungsten Targets Bombarded by 18, 28, and 38 MeV Electrons

We measured the angular distribution of bremsstrahlung photons between 0 and 120 degrees from copper and tungstentargets bombarded by 18, 28, and 38MeV electrons at the electron linac of Hokkaido University. Activation detectors and two types of dosimeters were applied for the measurement. The measured results were compared with those calculated with the Monte Carlo code MCNP5 to verify the calculated results. The calculated results of both the reaction rates and ambient dose equivalent rates gave good agreement with the measured ones in the case of 18MeV electrons. A good agreement between the measurement and calculation was also observed for relative angular distributions of dose rates from 38MeV electrons; however, the calculation overestimated the measured data by a factor of 1.2 to 2.0. To achieve further accuracy of calculation, improvement of photonuclear reaction data and absorbed dose measurement are necessary for bremsstrahlung radiation dosimetry.

Photonuclear reaction data and γ-ray sources for astrophysics

Direct determination of photoneutron cross sections of astrophysical importance has recently become possible with use of quasi-monochromatic γ beams produced in laser Compton backscattering (LCS) from relativistic electrons at AIST. The astrophysics to be discussed with the photodisintegration cross section are both stellar and big bang nucleosyntheses regarding the production of p-process and s-process nuclei as well as light elements. Synchrotron radiations from a 10 tesla superconducting wiggler (SCW) at SPring-8 serve as an ideal photon source to determine photoreaction rates. This paper covers the latest cross section measurements with the LCS photon beams and a feasibility study of determining (γ,x) (x = n, p, α) reaction rates with the SCW radiation.

Photonuclear reactions: Modern status of the data

Photonuclear reaction data play an important role in basic and applied research. Radiation shielding design, radiation transport analysis, activation analysis, astrophysical nucleosynthesis, safeguards and inspection technologies, human body radiotherapy absorbed dose calculations, beam monitoring in heavy-ion dissociation research at ultrarelativistic energies, etc., could be mentioned. However, there exist quite evident systematic discrepancies in both shapes and magnitudes between photonuclear cross sections measured in various laboratories. These discrepancies noticeably reduce the accuracy and reliability of data. A systematic overview of various types of data contained in the international database is given. The modern status of the data is discussed. The reasons for significant discrepancies between various photonuclear data are analyzed and methods to reduce them are suggested.

Photonuclear Physics in Radiation Transport—II: Implementation

This is the second of two companion papers. The first paper describes model calculations and nuclear data evaluations of photonuclear reactions on isotopes of C, O, Al, Si, Ca, Fe, Cu, Ta, W, and Pb for incident photon energies up to 150 MeV. This paper describes the steps taken to process these files into transport libraries and to update the Monte Carlo N-Particle (MCNP) and MCNPX radiation transport codes to use tabular photonuclear reaction data. The evaluated photonuclear data files are created in the standard evaluated nuclear data file (ENDF) format. These files must be processed by the NJOY data processing system into A Compact ENDF (ACE) files suitable for radiation transport calculations. MCNP and MCNPX have been modified to use these new data in a self-consistent and fully integrated manner. Verification problems were used at each step along the path to check the integrity of the methodology. The resulting methodology and tools provide a comprehensive system for using photonuclear data in radiation transport calculations. Also described are initial validation simulations used to benchmark several of the photonuclear transport tables.

Photonuclear Data

We review the current status of photonuclear data, in particular in the light of recent major progress in developing internationally recognized library of evaluated photonuclear reaction data. The paper covers all aspects of photonuclear data, including experiments, photonuclear reaction theory, evaluation procedures, review of national photonuclear libraries, and description of the major IAEA library as well as its validation. This major library, prepared to suit transport calculations, contains data in the ENDF-6 format for 164 materials evaluated mostly up to 150 MeV.

Present Status of JENDL Photonuclear Data File

Evaluation task of photonuclear reaction cross sections is in progress as an activity under JNDC Photonuclear Data File Compilation Sub-Working Group. The goal of this working group is to construct an evaluated photonuclear reaction data file. The evaluated data is stored using ENDF-6 high-energy format. The data file contains absorption, particle production and nuclide production cross sections up to 140 MeV, which is approximately corresponding to the threshold energy of (γ, π) reactions. In addition, energy-angle double differential cross sections of emitted particles are stored. Theoretical evaluation as well as experimental data evaluation are employed. Nuclear model calculation based on pre-equilibrium and evaporation model is carried out and reproduce experimental data quite well. Evaluation for D, 9Be, 12C, 14N, l6O, 23Na, 24,25,26Mg, 27Al, 28,29,30Si, 40,48Ca, 46,48Ti, 51V, 52Cr, 55Mn, 54,56Fe, 59Co, 58, 60Ni, 63, 65Cu, 64Zn, 90Zr, 93Nb 92,94,96,98,100Mo, 133Cs 181Ta 182,184,186W, 197Au 206,207, 208Pb 209Bi and 235,238U have been completed.

Evaluation of Photonuclear Reaction Data on Tantalum-181 up to 140MeV

Photonuclear cross sections of 181Ta are evaluated up to an incident photon energy of 140MeV which is the threshold energy for pion production. Re-analyses were performed on the (γ, n) and (γ, 2n) data measured at Saclay and Livermore, and reference data were reconstructed. The absorption cross sections were evaluated with the giant electric dipole resonance (GDR) model below 40MeV. The calculation by the statistical model with preequilibrium correction reproduced the reference data of all the photoneutron cross sections consistently. From 40 to 140 MeV, the quasideuteron model (QDM) was adopted to evaluate photoabsorption cross sections and the results are compared with the measurements. The decaying processes including n, p, d, t, 3He, and α particle emission up to 140MeV were theoretically evaluated by the ALICE-F code.

Evaluation of Photonuclear Reaction Data on Tantalum-181 up to 140 MeV.

Photonuclear cross sections of 181Ta are evaluated up to an incident photon energy of 140MeV which is the threshold energy for pion production. Re-analyses were performed on the (γ, n) and (γ, 2n) data measured at Saclay and Livermore, and reference data were reconstructed. The absorption cross sections were evaluated with the giant electric dipole resonance (GDR) model below 40MeV. The calculation by the statistical model with preequilibrium correction reproduced the reference data of all the photoneutron cross sections consistently. From 40 to 140 MeV, the quasideuteron model (QDM) was adopted to evaluate photoabsorption cross sections and the results are compared with the measurements. The decaying processes including n, p, d, t, 3He, and α particle emission up to 140MeV were theoretically evaluated by the ALICE-F code.

Electron scattering from excited states ofO18above 10 MeV

The giant resonance region of /sup 18/O has been investigated by means of inelastic electron scattering at three values of the momentum transfer. The main features of the giant dipole resonance correlate well with photonuclear reaction data. In addition, considerable contribution from quadrupole excitations is apparent in the excitation energy range from 10 to 23 MeV, with some additional strength from 30 to 45 MeV.