GAMMA-RAY ANGULAR CORRELATIONS FROM ALIGNED NUCLEI PRODUCED BY NUCLEAR REACTIONS

1961 ◽  
Vol 39 (6) ◽  
pp. 788-824 ◽  
Author(s):  
A. E. Litherland ◽  
A. J. Ferguson
Keyword(s):  
Angular Correlation ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Residual Nucleus ◽  
Incident Beam ◽  
Nuclear Spectroscopy ◽  
Population Parameters ◽  
Axially Symmetric ◽  
Angular Correlations

Two general procedures for the measurement and analysis of angular correlations of gamma radiations from nuclear reactions are described which have wide applications in nuclear spectroscopy for the determination of spins and gamma-ray multipolarities. Cases can be studied by these methods when the reaction proceeds through a compound state too complex to allow the usual analysis to be made, for example where several levels overlap or where direct interaction is dominant. The basis of these procedures is to exploit the simplifications brought about by making the reacting system axially symmetric. A sharp gamma-ray-emitting state formed in such a system can be regarded as aligned and described in terms of a relatively small number of population parameters for the magnetic substates. In the first procedure, a state Y* is prepared by a nuclear reaction X(h1h2) Y* in which h2 is unobserved. The state Y* has axial symmetry about the beam axis. From coincidence angular correlation measurements of two cascade gamma rays from Y*, the unknown population parameters for Y* together with the nuclear spins and gamma-ray multipolarities can be determined. In the second procedure, h2 is measured in a small counter at 0° or 180° relative to the incident beam. It is then shown that the quantum numbers of the magnetic substates of Y* which can be populated do not exceed the sum of the spins of X, h1, and h2. In cases where the sum of the spins does not exceed [Formula: see text], the angular correlation of the gamma rays from the aligned state depends only upon the properties of the states in the residual nucleus. Theoretical expressions for angular correlations from aligned states are given, together with a method whereby existing extensive tables of coefficients can be used to calculate them. The results of two recent experiments are discussed as examples.

AN ILLUSTRATION OF A TYPE OF TRIPLE CORRELATION MEASUREMENT WHICH CAN BE EASILY INTERPRETED

1960 ◽  
Vol 38 (7) ◽  
pp. 927-940 ◽  
Author(s):  
A. E. Litherland ◽  
G. J. McCallum
Keyword(s):  
Angular Correlation ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Residual Nucleus ◽  
Incident Beam ◽  
Electric Quadrupole ◽  
Final States ◽  
Angular Correlations ◽  
Mixing Ratios ◽  
Triple Correlation

The Mg26(He4, nγ)Si29 reaction has been used to illustrate the simplifications introduced in the interpretation of triple angular correlations by choosing a target and bombarding particles of zero spin and by observing the emitted particles, in this case neutrons, in a counter fixed at 0° to the beam. The angular correlations of the gamma rays with respect to the incident beam then depend only upon the properties of the final states in the residual nucleus. The angular correlation of the electric quadrupole 2.03-Mev gamma ray is predicted uniquely by theory and this prediction has been verified experimentally. The angular correlations of the 1.28-Mev and 2.43-Mev gamma rays have yielded for the E2/M1 amplitude mixing ratios +0.25 ± 0.05 or −3.4 ± 0.5 and −0.26 ± 0.08 or −1.10 ± 0.16 respectively. In addition, the experiment provides an illustration of the value of the recently discovered technique of neutron – gamma-ray discrimination in an organic scintillator.

Determination of mixing ratios for some cascades corresponding to 109Ag

1977 ◽  
Vol 55 (2) ◽  
pp. 175-179 ◽  
Author(s):  
H. E. Bosch ◽  
V. M. Silbergleit ◽  
M. Davidson ◽  
J. Davidson
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Angular Correlations ◽  
Mixing Ratios ◽  
Multichannel Analyzer ◽  
Level 3 ◽  
Gamma Ray Detector

An investigation of the gamma–gamma ray angular correlations following the decay of 109Pd was made by using a Ge(Li) semiconductor counter and NaI(Tl) gamma-ray detector. Coincidences measurements at six different angles were made between the 311 keV gamma ray (gated in the movable counter) and 390, 413, 424, 551, and 558 keV gamma rays (displayed in a multichannel analyzer (MCA)). Chance coincidences as well as coincidence background were taken into account. The following spins and mixing ratios were determined: 701 keV level 3/2, δ(390) = 0.19 ± 0.06; 724 keV level 3/2, δ(413) = 0.18 ± 0.05; 735 keV level 5/2, δ(424) = −0.27 ± 0.03; 862 keV level 5/2, δ(551) = −0.28 ± 0.04; 869 keV level 5/2, δ(558) = −0.26 ± 0.05. The result indicates that the anisotropies are consistent with mixing ratios less than 28% in all cases.

GAMMA-RAY ANGULAR CORRELATION MEASUREMENTS IN Ne22

1964 ◽  
Vol 42 (6) ◽  
pp. 1300-1310 ◽  
Author(s):  
C. Broude ◽  
M. A. Eswaran
Keyword(s):  
Excited State ◽  
Angular Correlation ◽  
Gamma Ray ◽  
Amplitude Ratio ◽  
Spin Assignment ◽  
Primary Radiation ◽  
Angular Correlations ◽  
First Excited State

Coincidence gamma-ray angular correlations of the cascade decays from the 3.34- and 4.47-Mev states in Ne22 through the first excited state have been measured. The levels were excited by the reaction F19 (α, p)Ne22. The correlations give an unambiguous spin assignment of 4 to the 3.34-Mev state; the analysis of the correlations from the 4.47-Mev state is not unique, allowing spin 2 or 3. The quadrupole-to-dipole amplitude ratio for the primary radiation is −0.11 ± 0.03 or −1.07 ± 0.10, respectively, for the spin-2 and spin-3 assignments.

Study of levels in 24Mg

1968 ◽  
Vol 46 (12) ◽  
pp. 1381-1401 ◽  
Author(s):  
R. W. Ollerhead ◽  
J. A. Kuehner ◽  
R. J. A. Levesque ◽  
E. W. Blackmore
Keyword(s):  
Angular Correlation ◽  
Beta Decay ◽  
Rotational Band ◽  
Ground State ◽  
Present Experiment ◽  
Gamma Ray ◽  
Axially Symmetric ◽  
Excitation Energies ◽  
Rotational Model ◽  
Rotational Bands

Nineteen levels in 24Mg have been studied utilizing the reaction 12C(16O, αγ)24Mg. Angular correlation measurements have established the spins and parities of levels at excitation energies of 7.35, 7.56, 7.62, 8.44, 8.65, 9.00, 9.15, and 10.1 MeV as 2+, 1−, 3−, 1−, 2+, 2+, 1−, and 0+ respectively. Levels at 8.12 and 13.18 MeV have been identified as the 6+ and 8+ members of the K = 0 ground-state rotational band; levels at 7.81 and 9.52 MeV have been identified as the 5+ and 6+ members of the K = 2 rotational band based on the 2+ level at 4.23 MeV. The existence of doublets has been established at excitation energies of 8.44 and 9.52 MeV; in each case, one member of the doublet is populated in the beta decay of 24Al, and the present experiment indicates that these two levels have spin and parity 4+. Assignments are also suggested for levels at 7.75 MeV (1+) and 8.36 MeV (2+). Gamma-ray spectra have been obtained for levels at 8.86, 9.28, and 9.46 MeV. The properties of levels assigned to rotational bands are compared to the predictions of the rotational model for an axially symmetric nucleus.

EXCITED STATES OF O18 STUDIED BY THE REACTION

1961 ◽  
Vol 39 (2) ◽  
pp. 276-294 ◽  
Author(s):  
A. E. Litherland ◽  
R. Batchelor ◽  
A. J. Ferguson ◽  
H. E. Gove
Keyword(s):  
Excited States ◽  
Gamma Rays ◽  
Recent Experiment ◽  
Gamma Ray ◽  
Electric Quadrupole ◽  
Angular Correlations ◽  
Small Admixture ◽  
First Excited State ◽  
Cascade Transition ◽  
Crossover Transition

Gamma rays from the excited states of O18 at 3.63 and 3.92 Mev have been observed using the reaction [Formula: see text] at an incident O16 energy of 14 Mev. Both states were observed to emit gamma rays to the 1.98-Mev 2+ first excited state of O18. No evidence for crossover transitions was found and in each case the crossover transition was estimated to be [Formula: see text] of the cascade transition. Angular correlations of the gamma rays were obtained and these strongly support an assignment of spin 0 to the 3.63-Mev state and a spin of 2 for the 3.92-Mev state. These assignments have been confirmed by a recent experiment on the O16(H3, p)O18 reaction which gives the assignments 0+ and 2+ for these two states. Thus the states at 3.55, 3.63, and 3.92 Mev form a triplet with assignments 4+, 0+, and 2+ which strongly resembles the vibrational spectra found in heavier nuclei. However, the measured angular correlations of the gamma rays from the 3.92-Mev state show only a small admixture of electric quadrupole in the 1.94-Mev gamma ray with relative amplitude +0.1 ±.1. A lower limit of ~10−12 seconds on the lifetime of the 3.63-Mev state was obtained from the absence of a doppler shift of the 1.65-Mev cascade gamma ray.

scholarly journals Gamma-Ray Lines from Solar Flares

1975 ◽  
Vol 68 ◽  
pp. 363-383 ◽  
Author(s):  
R. Ramaty ◽  
R. E. Lingenfelter
Keyword(s):  
Gamma Rays ◽  
Solar Flares ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
The Other ◽  
Line Production ◽  
Absolute Intensities ◽  
Flare Region ◽  
Accelerated Particles

We have treated in detail the theory of gamma-ray line production in solar flares. The strongest line, both predicted theoretically and detected observationally at 2.2 MeV, is due to neutron capture by protons in the photosphere. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear gamma rays. From the comparison of the observed and calculated intensities of the lines at 4.4 or 6.1 MeV to that of the 2.2 MeV line it is possible to deduce the spectrum of accelerated nuclei in the flare region; and from the absolute intensities of these lines it is possible to obtain the total number of accelerated nuclei at the Sun. The study of the 2.2 MeV line also gives information on the amount of He3 in the photosphere. The study of the line at 0.51 MeV resulting from positron annihilation complements the data obtained from the other lines; in addition it gives information on the temperature and density in the annihilation region and on the anisotropy of the accelerated electron beam which produces continuum gamma rays at energies greater than about 1 MeV.

K X-Ray and Gamma-Ray Angular Correlations in the Decay of 113Sn and 133Ba, using a High Efficiency Sum-Peak Coincidence Scintillation Spectrometer

1971 ◽  
Vol 49 (13) ◽  
pp. 1769-1772 ◽  
Author(s):  
K. Venkata Ramana Rao ◽  
V. Lakshminarayana
Keyword(s):  
Angular Correlation ◽  
Beta Decay ◽  
High Efficiency ◽  
Gamma Ray ◽  
X Ray ◽  
Angular Correlations ◽  
Nuclear Environment

K-capture isotopes 113Sn and 133Ba are used with a sum-peak coincidence scintillation spectrometer arrangement to study the K X-ray – gamma-ray angular correlation. The effects of the type of beta decay, the nuclear environment, and three-gamma cascades with intermediate gamma ray unobserved are investigated. No anisotropy could be detected, supporting the theory of Dolginov.

scholarly journals TANGRA multidetector systems for investigation of neutron-nuclear reactions at the JINR Frank Laboratory of Neutron Physics

2021 ◽  
Vol 256 ◽  
pp. 00014
Author(s):  
Ivan Ruskov ◽  
Yury Kopach ◽  
Vyacheslav Bystritsky ◽  
Vadim Skoy ◽  
Dimitar Grozdanov ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Nuclear Research ◽  
Gamma Ray Spectrometry ◽  
Reaction Products ◽  
Science And Engineering ◽  
Neutron Physics ◽  
Gamma Ray Spectrometer ◽  
Crystal Scintillation

In the framework of TANGRA-project at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear research in Dubna (Russia), two experimental setups (Fig. 1) have been designed and tested for investigation of 14-MeV neutron-induced nuclear reactions on a number of important for nuclear science and engineering isotopes. As a source of 14-MeV “tagged” neutrons we are using the VNIIA ING-27 steady-state portable neutron generator with embedded in its vacuum tube 64-pixel charge-particle detector. The “Romashka” system is an array of up-to 24 hexagonal NaI(Tl)-crystal scintillation probes, while the “Romasha” array consists of 18 cylindrical BGO-crystal detectors of neutrons and gamma-rays. In addition to these detectors there is a HPGe gamma-ray spectrometer and a number of Stilbene detectors that can be added for high-resolution gamma-ray spectrometry and neutron-gamma detection. The main characteristics of the neutron-induced nuclear reaction products can be investigated by commissioning the detectors in suitable for these experiments’ geometries. Both setups can be used for doing basic and applied scientific research, because they permit simultaneously to measure the energy, angle and multiplicity distributions of gamma-rays and neutrons, produced in the competitive neutron-induced nuclear reactions (n, n’γ), (n,2n), (n, xnγ) and (n, f) in pure or complex substances.

Vulcanization of SBR in a Thermal Neutron Field

1960 ◽  
Vol 33 (4) ◽  
pp. 1083-1091
Author(s):  
Herbert R. Anderson
Keyword(s):  
Boron Nitride ◽  
Thermal Neutron ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Neutron Field ◽  
Energy Utilization ◽  
Rubber Compound ◽  
Helium Atmosphere ◽  
Residual Radioactivity

Abstract The nuclear reactions B10(n,α)Li7* and Li6(n,α)H3 can be used to generate highly ionizing particles in a pure thermal neutron field to vulcanize an otherwise transparent rubber compound. Vulcanizates have satisfactory physical properties comparable with those produced by other means of vulcanization, e.g., gamma rays and peroxides. Such vulcanizates possessed negligible residual radioactivity. The somewhat analogous initiating systems gave vastly different vulcanizates with the same parent rubber compound in a helium atmosphere, and a possible explanation is presented. The G values for lithium methoxide promotion (ca. 3) are comparable with those obtained with gamma-ray vulcanizates. Promotion is less efficient with boron nitride, the average values of G being approximately 0.9. The irradiation atmosphere has a pronounced influence on the type of vulcanizate produced and on the energy utilization. Substitution of air for helium as the irradiation atmosphere increases net crosslinking of cold rubber with boron nitride promotion, while it decreases it when lithium methoxide is used as the promoter.

scholarly journals First in-core gamma spectroscopy experiments in a zero power reactor

2021 ◽  
Vol 253 ◽  
pp. 04022
Author(s):  
Oskari Pakari ◽  
Vincent Lamirand ◽  
Tom Mager ◽  
Axel Laureau ◽  
Pavel Frajtag ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Power Reactor ◽  
Gamma Spectroscopy ◽  
Reactor Core ◽  
Pulse Height ◽  
Nuclear Data ◽  
Federal Institute ◽  
Institute Of Technology

Gamma rays in nuclear reactors, arising either from nuclear reactions or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic environment, allowing for validation experiments of dose estimates, computed spectra, and prompt to delayed gamma ratios. The resulting data can contribute to models, code validation and photo atomic/nuclear data evaluation. To date, most experiments have relied on flux measurements using TLDs, ionization chambers, or spectrometers set in low flux areas. The CROCUS reactor allows for flexible detector placement in and around the core, and has recently been outfitted with gamma detection capabilities to fulfill the need for in-core gamma spectroscopy, as opposed to flux. In this paper we report on the experiments and accompanying simulations of gamma spectrum measurements inside a zero power reactor core, CROCUS. It is a two-zone, uranium-fueled light water moderated facility operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL). Herein we also introduce, in detail, the new LEAF system: A Large Energy-resolving detection Array for Fission gammas. It consists of an array of four detectors – two large ø 127 254 mm Bismuth Germanate (BGO) and two smaller ø 12 50 mm Cerium Bromide (CeBr3) scintillators. We describe the calibration and characterization of LEAF followed by first in-core measurements of gamma ray spectra in a zero power reactor at different sub-critical and critical states, and different locations. The spectra are then compared to code results, namely MCNP6.2 pulse height tallies. We were able to distinguish prompt processes and delayed peaks from decay databases. We present thus experimental data from hitherto inaccessible core regions. We provide the data as validation means for codes that attempt to model these processes for energies up to 10 MeV. We finally draw conclusions and discuss the future uses of LEAF. The results indicate the possibility of isotope tracking and burn-up validation.

Sign in / Sign up

Export Citation Format

Share Document