Ray Yield Research Articles

Measurement of the transverse asymmetry of γ rays in the Sn117(n,γ)Sn118 reaction

Largely enhanced parity-violating effects observed in compound resonances induced by epithermal neutrons are currently attributed to the mixing of parity-unfavored partial amplitudes in the entrance channel of the compound states. Furthermore, it is proposed that the same mechanism that enhances the parity-violation also enhances the breaking of time-reversal-invariance in the compound nucleus. The entrance-channel mixing induces energy-dependent spin-angular correlations of individual $\gamma$-rays emitted from the compound nuclear state. For a detailed study of the mixing model, a $\gamma$-ray yield in the reaction of $^{117}$Sn(n,$\gamma$)$^{118}$Sn was measured using the pulsed beam of polarized epithermal neutrons and Ge detectors. An angular dependence of asymmetric $\gamma$-ray yields for the orientation of the neutron polarization was observed.

Beryllium determination in non-optimal matrices using the $^{9}$\textbf{Be(d,n$\gamma )$}$^{10}$\textbf{B}

An alternative method for the detection of beryllium in light element matrices is proposed, implementing the use of a deuteron beam at energies from 1 to 2.1 MeV and the $^{9}$Be(d,n$\gamma )^{10}$B reaction. A HP GE detector of 20{\%} relative efficiency was used to detect the 718 keV gamma ray of $^{10}$B. The minimum detection limits obtained for beryllium, are compared to those taken with other NRA techniques (PIGE, heavy-ion and charged-particle spectroscopy) in complex matrices containing high concentrations of light elements. The absolute $\gamma $-ray yield of the reaction is also compared to absolute $\gamma $-ray yields from literature.

Fluka simulation of PGNAA system for determining heavy metal pollution in the soil sample

Abstract This study presented a self-designed prompt gamma neutron activation analysis (PGNAA) model and used Fluka simulation to simulate the heavy metals (Mn, Cu, Hg, Ni, Cr, Pb) in soil samples. The relationship between the prompt γ -ray yield of each heavy metal and soil thickness, content of heavy metals in the soil, and source distance was obtained. Simulation results show that the prompt γ -ray yield of each heavy metal increases with the increase in soil thickness and reaches saturation at 18 cm. The greater the proportion of heavy metals in the soil, the greater the prompt γ -ray yield. The highest content is approximately 3%, and the change in distance between the neutron source and soil sample does not affect the prompt γ -ray yield of heavy metals.

Collimated ultrabright gamma rays from electron wiggling along a petawatt laser-irradiated wire in the QED regime

Even though high-quality X- and gamma rays with photon energy below mega-electron volt (MeV) are available from large-scale X-ray free electron lasers and synchrotron radiation facilities, it remains a great challenge to generate bright gamma rays over 10 MeV. Recently, gamma rays with energies up to the MeV level were observed in Compton scattering experiments based on laser wakefield accelerators, but the yield efficiency was as low as [Formula: see text], owing to low charge of the electron beam. Here, we propose a scheme to efficiently generate gamma rays of hundreds of MeV from submicrometer wires irradiated by petawatt lasers, where electron accelerating and wiggling are achieved simultaneously. The wiggling is caused by the quasistatic electric and magnetic fields induced around the wire surface, and these are so high that even quantum electrodynamics (QED) effects become significant for gamma-ray generation, although the driving lasers are only at the petawatt level. Our full 3D simulations show that directional, ultrabright gamma rays are generated, containing [Formula: see text] photons between 5 and 500 MeV within a 10-fs duration. The brilliance, up to [Formula: see text] photons [Formula: see text] per 0.1% bandwidth at an average photon energy of 20 MeV, is second only to X-ray free electron lasers, while the photon energy is 3 orders of magnitude higher than the latter. In addition, the gamma ray yield efficiency approaches 10%-that is, 5 orders of magnitude higher than the Compton scattering based on laser wakefield accelerators. Such high-energy, ultrabright, femtosecond-duration gamma rays may find applications in nuclear photonics, radiotherapy, and laboratory astrophysics.

Production potential of medical isotopes from natural uranium fission processes

We present the results of gamma ray yield measurements from the neutron induced fission of natural uranium at a low power research reactor. Our focus is on the quantitative yields of radio activities produced from 99Mo, 132I, 133I and 135Xe. These isotopes are good candidates for applications in medicine. We estimate the saturation activities and likely yields at typical neutrons fluxes of 1013 n/cm2/s and conclude that natural uranium, in conjunction with neutron beam facilities, offer viable production venues.

Assessment of 43,44Sc isotope production in proton- and alpha- induced reactions

We measured the gamma ray yields of proton and alpha induced reactions on natural calcium in the form of CaO target. The production rates of 43Sc, 44Sc isotopes of medical imaging interest are determined. It is found that alpha production for E < 20 MeV are well suited for producing the 43Sc isotope, while proton beams of about 15–20 MeV yield both 43Sc and 44Sc isotopes in comparable amounts to be of use as prospective medical imaging by PET and associated photons.

Research on the self-absorption corrections for PGNAA of large samples

When a large sample is analysed with the prompt gamma neutron activation analysis (PGNAA) neutron self-shielding and gamma self-absorption affect the accuracy, the correction method for the detection efficiency of the relative H of each element in a large sample is described. The influences of the thickness and density of the cement samples on the H detection efficiency, as well as the impurities Fe2O3 and SiO2 on the prompt $ \gamma$ ray yield for each element in the cement samples, were studied. The phase functions for Ca, Fe, and Si on H with changes in sample thickness and density were provided to avoid complicated procedures for preparing the corresponding density or thickness scale for measuring samples under each density or thickness value and to present a simplified method for the measurement efficiency scale for prompt-gamma neutron activation analysis.

Prompt gamma ray evaluation for chlorine analysis in blended cement concrete

Single prompt gamma ray energy has been evaluated to measure chlorine concentration in fly ash (FA), Super-Pozz (SPZ) and blast furnace slag (BFS) cement concrete specimens using a portable neutron generator-based Prompt Gamma Neutron Activation (PGNAA) setup. The gamma ray yield data from chloride concentration measurement in FA, SPZ and BFS cement concretes for 2.86–3.10, 5.72 and 6.11MeV chlorine gamma rays were analyzed to identify a gamma ray with common slope (gamma ray yield/Cl conc. wt%) for the FA, BFS and SPZ cement concretes. The gamma ray yield data for FA and SPZ cement concretes with varying chloride concentration were measured previously using a portable neutron generator-based PGNAA setup. In the current study, new data have been measured for chlorine detection in the BFS cement concrete using a portable neutron generator-based PGNAA setup for 2.86–3.10, 5.72, and 6.11MeV chlorine gamma rays. The minimum detection limit of chlorine in BFS cement concrete (MDC) was found to be 0.034±0.010, 0.032±0.010, 0.033±0.010 for 2.86–3.10, 5.72 and 6.11MeV gamma ray, respectively.The new BFS cement concrete data, along with the previous measurements for FA and SPZ cement concretes, have been utilized to identify a gamma ray with a common slope to analyze the Cl concentration in all of these blended cement concretes. It has been observed that the 6.11MeV chlorine gamma ray has a common slope of 5295±265 gamma rays/wt % Cl concentration for the portable neutron generator-based PGNAA setup. The minimum detectable concentration (MDC) of chlorine in blended cement concrete was measured to be 0.033±0.010wt % for the portable neutron generator-based PGNAA. Thus, the 6.11MeV chlorine gamma ray can be used for chlorine analysis of blended cement concretes.

Gamma Heating Rate Evaluation for Material Irradiation Test in the Joyo Experimental Fast Reactor

The evaluation of the spatial distribution of gamma heating in fast reactors requires consideration of all the gamma intensity components. However, the delayed gamma ray yield data of all actinides are not included in evaluated nuclear data files such as ENDF or JEDNL. In this study, new neutron and gamma cross section constants considering the delayed gamma ray based on JENDL-3.2 and JENDL-4.0 were developed. Neutron and gamma ray coupling calculations for the Joyo experimental fast reactor core revealed that the gamma flux increased by approximately 40% when the delayed gamma intensities in both JENDL-3.2 and JENDL-4.0 were considered. The calculated gamma heating rates were verified by comparison with the measured data obtained by on-line irradiation rigs. It was confirmed that the calculated gamma heating rates agreed with the measurements to within 3–12%.

Observation of Gigawatt-Class THz Pulses from a Compact Laser-Driven Particle Accelerator

We report the observation of subpicosecond terahertz (T-ray) pulses with energies ≥460 μJ from a laser-driven ion accelerator, thus rendering the peak power of the source higher even than that of state-of-the-art synchrotrons. Experiments were performed with intense laser pulses (up to 5×10(19) W/cm(2)) to irradiate thin metal foil targets. Ion spectra measured simultaneously showed a square law dependence of the T-ray yield on particle number. Two-dimensional particle-in-cell simulations show the presence of transient currents at the target rear surface which could be responsible for the strong T-ray emission.

Sample dependent response of a LaCl3:Ce detector in prompt gamma neutron activation analysis of bulk hydrocarbon samples

The response of a LaCl3:Ce detector has been found to depend upon the hydrogen content of bulk samples in prompt gamma analysis using 14MeV neutron inelastic scattering. The moderation of 14MeV neutrons from hydrogen in the bulk sample produces thermal neutrons around the sample which ultimately excite chlorine capture gamma rays in the LaCl3:Ce detector material. Interference of 6.11MeV chlorine gamma rays from the detector itself with 6.13MeV oxygen gamma rays from the bulk samples makes the intensity of the 6.13MeV oxygen gamma ray peak relatively insensitive to variations in oxygen concentration. The strong dependence of the 1.95MeV doublet chlorine gamma ray yield on hydrogen content of the bulk samples confirms fast neutron moderation from hydrogen in the bulk samples as a major source of production of thermal neutrons and chlorine gamma rays in the LaCl3:Ce detector material.Despite their poor oxygen detection capabilities, these detectors have nonetheless excellent detection capabilities for hydrogen and carbon in benzene, butyl alcohol, propanol, propanic acid, and formic acid bulk samples using 14MeV neutron inelastic scattering.

E2Interference Effects in theC(α,γ0)16O12Reaction

The $E1\mathrm{\text{\ensuremath{-}}}E2$ interference sign between the ${E}_{\mathrm{c}.\mathrm{m}.}=2.68\ensuremath{-}\mathrm{MeV}$ $E2$ resonance and an underlying $E1$ strength has been measured for the first time. An $E1\mathrm{\text{\ensuremath{-}}}E2$ asymmetry parameter of $a=0.07\ifmmode\pm\else\textpm\fi{}0.05$ was extracted from the thick-target $\ensuremath{\gamma}$-ray yields of the narrow resonance at angles of 45\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{}. The positive sign of $a$ corresponded to constructive interference at forward angles and, further, allowed the interference between the resonance and an $E2$ background to be identified as constructive below the resonance energy. The $E2\mathrm{\text{\ensuremath{-}}}E2$ interference was then used to evaluate the global ${S}_{E2}$ data within the vicinity of the resonance $2.5\ensuremath{\le}{E}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\le}3.0\text{ }\text{ }\mathrm{MeV}$. An analysis of the global ${S}_{E2}$ data that agreed with the interference scenario has determined the $E2\mathrm{\text{\ensuremath{-}}}E2$ interference scheme of the 4.34-MeV resonance and background, resulting in a value of ${S}_{E2}(300)={62}_{\ensuremath{-}6}^{+9}\text{ }\text{ }\mathrm{keV}\text{ }\mathrm{b}$.

Absoluteβ-to-ground band transition strengths in154Sm

Low-lying collective states of ${}^{154}$Sm are studied via the ${}^{12}$C(${}^{154}$Sm,${}^{154}$Sm${}^{*}$) Coulomb excitation reaction at 85$%$ of the Coulomb barrier (570 MeV) using the Gammasphere Ge-detector array. Absolute transition strengths are obtained from the Coulomb excitation cross sections deduced from the relative $\ensuremath{\gamma}$-ray yields. The results include transition strengths for $E2$ decays of energy levels in the low-spin part of the first excited ${K}^{\ensuremath{\pi}}={0}^{+}$ rotational band of ${}^{154}$Sm. The agreement of these results with the confined $\ensuremath{\beta}$-soft rotor model predictions establishes the assignment of this band as a $\ensuremath{\beta}$ band.

Special nuclear material detection with a mobile multi-detector system

The detection of special nuclear material has been studied with a mobile inspection system used both as a high sensitivity passive neutron/gamma spectroscopic tool and as an active inspection device using tagged neutrons. The detection of plutonium samples seems to be possible with passive interrogation, even for small samples, thanks to the yield of gamma ray and neutrons. Moreover the gamma ray spectrum shows clear signatures related to 239Pu. The passive detection of uranium is much more difficult because of the low neutron yield and of the easiness of shielding the gamma ray yield of highly enriched U samples. However, we show that active interrogation with tagged neutrons is able to provide signatures for the discrimination of uranium against other heavy metals.

Hadronic beam models for quasars and microquasars

Most of the hadronic jet models for quasars (QSOs) and microquasars (MQs) found in literature represent beams of particles (e.g. protons). These particles interact with the matter in the stellar wind of the companion star in the system or with crossing clouds, generating gamma-rays via proton-proton processes. Our aim is to derive the particle distribution in the jet as seen by the observer, so that proper computation of the $\gamma$-ray and neutrino yields can be done. We use relativistic invariants to obtain the transformed expressions in the case of a power-law and power-law with a cutoff particle distribution in the beam. We compare with previous expressions used earlier in the literature. We show that formerly used expressions for the particle distributions in the beam as seen by the observer are in error, differences being strongly dependent on the viewing angle. For example, for $\Gamma =10$ ($\Gamma$ is the Lorentz factor of the blob) and angles larger than $\sim 20^o$, the earlier-used calculation entails an over-prediction (order of magnitude or more) of the proton spectra for $E>\Gamma mc^2$, whereas it always over-predicts (two orders of magnitude) the proton spectrum at lower energies, disregarding the viewing angle. All the results for photon and neutrino fluxes in hadronic models in beams that have made use of the earlier calculation are affected. Given that correct gamma-ray fluxes will be in almost any case significantly diminished in comparison with published results, and that the time of observations in Cherenkov facilities grows with the square of the flux-reduction factor in a statistically limited result, the possibility of observing hadronic beams is undermined.

Coulomb excitation of aAm242isomeric target:E2andE3strengths, rotational alignment, and collective enhancement

A $98%$ pure ${}^{242\mathrm{m}}$Am ($K={5}^{\ensuremath{-}}$, ${t}_{1/2}=141$ years) isomeric target was Coulomb excited with a $170.5$-MeV $^{40}\mathrm{Ar}$ beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify $46$ new states up to spin $18\ensuremath{\hbar}$ in at least four rotational bands; $11$ of these new states lie in the isomer band, $13$ in a previously unknown yrast ${K}^{\ensuremath{\pi}}={6}^{\ensuremath{-}}$ rotational band, and $13$ in a band tentatively identified as the predicted yrast ${K}^{\ensuremath{\pi}}={5}^{+}$ band. The rotational bands based on the ${K}^{\ensuremath{\pi}}={5}^{\ensuremath{-}}$ isomer and the ${6}^{\ensuremath{-}}$ bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The $\ensuremath{\gamma}$-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete $\ensuremath{\Delta}K=1$ mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the ${5}^{\ensuremath{-}}$ and ${6}^{\ensuremath{-}}$ bands allows for precise determination of the mixing interaction strength $V$, which approaches the strong-mixing limit; this agrees with the $50%$ attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the ${I}_{K}^{\ensuremath{\pi}}={6}_{6}^{\ensuremath{-}}$ state in the nominal ${6}_{5}^{\ensuremath{-}}$ isomer band state is measured within the PRM as $45.{6}_{\ensuremath{-}1.1}^{+0.3}%$. The $E$2 and $M$$1$ strengths coupling the ${5}^{\ensuremath{-}}$ and ${6}^{\ensuremath{-}}$ bands are enhanced significantly by the mixing, while $E1$ and $E2$ couplings to other low-$K$ bands are not measurably enhanced. The yields of the ${5}^{+}$ band are reproduced by an $E3$ strength of $\ensuremath{\approx}$15 W.u., competitive with the interband $E2$ strength. Alignments of the identified two-particle Nilsson states in $^{242}\mathrm{Am}$ are compared with the single-particle alignments in $^{241}\mathrm{Am}$.

Effect of Sample Moisture and Bulk Density on Performance of the 241Am-Be Source Based Prompt Gamma Rays Neutron Activation Analysis Setup—a Monte Carlo Study

Monte Carlo simulations were carried out using the dependence of gamma ray yield on the bulk density and moisture content for five different lengths of Portland cement samples in a thermal neutron capture based Prompt Gamma ray Neutron Activation Analysis (PGNAA) setup for source inside moderator geometry using an 241Am-Be neutron source. In this study, yields of 1.94 and 6.42 MeV prompt gamma rays from calcium in the five Portland cement samples were calculated as a function of sample bulk density and moisture content. The study showed a strong dependence of the 1.94 and 6.42 MeV gamma ray yield upon the sample bulk density but a weaker dependence upon sample moisture content. For an order of magnitude increase in the sample bulk density, an order of magnitude increase in the gamma rays yield was observed, i.e., a one-to-one correspondence. In case of gamma ray yield dependence upon sample moisture content, an order of magnitude increase in the moisture content of the sample resulted in about 16–17% increase in the yield of 1.94 and 6.42 MeV gamma rays from calcium.

Postshock turbulence and diffusive shock acceleration in young supernova remnants

<i>Context. <i/>Thin X-ray filaments are observed in the vicinity of young supernova remnants (SNR) blast waves. Identifying the process that creates these filaments would provide direct insight into the particle acceleration occurring within SNR and in particular the cosmic ray yield.<i>Aims. <i/>We investigate magnetic amplification in the upstream medium of a SNR blast wave through both resonant and non-resonant regimes of the streaming instability. We attempt to understand more clearly of the diffusive shock acceleration (DSA) efficiency by considering various relaxation processes of the magnetic fluctuations in the downstream medium. Multiwavelength radiative signatures originating in the SNR shock wave are used to test various downstream turbulence relaxation models.<i>Methods. <i/>Analytical and numerical calculations that couple stochastic differential equation schemes with 1D spherical magnetohydrodynamics simulations are used to investigate, in the context of test particles, turbulence evolution in both the forshock and post-shock regions. Stochastic second-order Fermi acceleration induced by resonant modes, magnetic field relaxation and amplification, and turbulence compression at the shock front are considered to model the multiwavelength filaments produced in SNRs. The <i>γ<i/>-ray emission is also considered in terms of inverse Compton mechanism.<i>Results. <i/>We confirm the result of Parizot and collaborators that the maximum CR energies should not go well beyond PeV energies in young SNRs where X-ray filaments are observed. To reproduce observational data, we derive an upper limit to the magnetic field amplitude and so ensure that stochastic particle reacceleration remains inefficient. Considering various magnetic relaxation processes, we then infer two necessary conditions to achieve efficient acceleration and X-ray filaments in SNRs: (1) the turbulence must fulfil the inequality 2 - <i>β<i/> - <i>≥<i/> 0; where <i>β<i/> is the turbulence spectral index and is the relaxation length energy power-law index; (2) the typical relaxation length must be of the order the X-ray rim size. We find that Alvénic/fast magnetosonic mode damping fulfils all conditions; while non-linear Kolmogorov damping does not. By confronting previous relaxation processes with observational data, we deducte that among our SNR sample, data for the older ones (SN1006 and G347.3-0.5) does not comply with all conditions, which means that their X-ray filaments are probably controlled by radiative losses. The younger SNRs, Cassiopeia A, Tycho, and Kepler pass all tests and we infer that the downstream magnetic field amplitude is in the range of 200–300 <i>μ<i/>Gauss.

Cross sections forU238(n,n'γ)andU238(n,2nγ)reactions at incident neutron energies between 5 and 14 MeV

Precision measurements of $^{238}\mathrm{U}$$(n,{n}^{'}\ensuremath{\gamma})$ and $^{238}\mathrm{U}$$(n,2n\ensuremath{\gamma})$ partial cross sections have been performed at Triangle Universities Nuclear Laboratory (TUNL) to improve crucial data needed for testing nuclear reaction models in the actinide mass region. A pulsed and monoenergetic neutron beam was used in combination with high-resolution \ensuremath{\gamma}-ray spectroscopy to obtain partial cross sections for incident neutron energies between 5 and 14 MeV. \ensuremath{\gamma}-ray yields were measured with high-purity germanium clover and planar detectors. Measured partial cross-section data are compared with previous results using white and monoenergetic neutron beams and calculations from the GNASH and TALYS Hauser-Feshbach statistical-model codes. Present experimental results are in fair to good agreement with most of the existing data for the $^{238}\mathrm{U}$$(n,{n}^{'}\ensuremath{\gamma})$ reaction. However, significant discrepancies are observed for the $^{238}\mathrm{U}$$(n,2n\ensuremath{\gamma})$ reaction.

X-ray Spectra Excited in Ar~(q+)(q=7—14) Incidence on Au Surface

The Au atomic Mα characteristic Xray spectrum has been measured for the slow highly charged ions Arq+ (q= 7—14) impacting on Au surface. The result shows that as long as the charge state of projectile is higher（q=11）， the characteristic Xrays of heavy atomic can be effectively excited even though the ionic beam is very weak(nA magnitude)， and the single ionic Xray yield is in the order of 10-8 and increases with potential energies of projectiles.