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We investigated the probability distribution of thermal neutron capture cross sections ($\sigma_{\rm th}$) deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large $\sigma_{\rm th}$ side due to a resonance happening to be close to the thermal energy, the multiresonance contribution considerably reduces the probability on the small $\sigma_{\rm th}$ side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei and found a good agreement between them., 共鳴パラメータの統計的性質を使って求められた熱中性子捕獲断面積$\sigma_{\rm th}$の統計的不定性について調べた。本研究では、乱数を用いて生成された共鳴パラメータから、$\sigma_{\rm th}$の確率密度分布を数値的に導出した。この結果、熱中性子エネルギーに最も近い最初の共鳴の統計的ゆらぎによって、熱中性子捕獲断面積が広い範囲に分布することが分かった。また、平均共鳴幅が平均崩壊幅と比較して十分に大きな値を持つ原子核においては、それぞれの$\sigma_{\rm th}$の確率密度分布が似た形状をしていることも分かった。計算された確率密度分布は、193核種の熱中性子捕獲断面積の実験データと比較され、両者が良い一致を示していることが分かった。

Water Cherenkov detectors are notable for their large masses and their charge particle detection capabilities. These two properties have been exploited in depth in many searches with outstanding results at Super-Kamiokande. On the other hand, neutrons are usually captured on protons and produce a single 2.2 MeV gamma. The Compton scattered electron that is being produced does not yield enough Cherenkov light for the PMT coverage (40\%) of Super-Kamiokande to be efficiently detected. However, detecting neutrons would be an important improvement in most of our analyses to either improve our signal event selection (for processes that produce neutrons) or background event rejection (for processes that do not produce any neutron). Gadolinium (Gd) has the largest thermal neutron capture cross section. In this process, it emits a gamma cascade with a total energy of about 8 MeV which would be possible to detect with high efficiency. The EGADS project demonstrated that it is possible to safely add Gd to Super-Kamiokande and the collaboration approved in June 2015 the SuperK-Gd project. The necessary refurbishment of the Super-Kamiokande detector started in June 2018 and finished in early 2019. In this talk, we will report about this work and the project outlook.

The thermal neutron cross section of 71Ga(n,$ \gamma$)72Ga reaction was measured with respect to the 197Au(n,$ \gamma$)198Au and 55Mn(n,$ \gamma$)56Mn monitor reactions using neutrons from an Am-Be source placed inside a concrete bunker. A covariance analysis was performed to obtain the off-diagonal weighted mean of the results determined with the two monitor reactions. The thermal neutron cross section obtained in the present study is $ 4.05 \pm 0.27$ b. The present result is lower than the data measured under neutron fields having broad neutron spectra in general, but more consistent with the thermal neutron cross sections extrapolated from the cross sections measured under monoenergetic neutron fields according to the $ 1/v$ -law. The current status of the 71Ga(n,$ \gamma$)72Ga reaction cross section in the nuclear databases is briefly reviewed in the relation with the Maxwellian spectrum averaged cross section for s -process calculation.

The use of smart proppants traced with gadolinium and samarium was evaluated in a realistic model by Monte Carlo simulations. The addition of compounds with high thermal neutron capture cross section, such as gadolinium oxide (Gd₂O₃) and samarium oxide (Sm₂O₃) into ceramic proppants, makes them detectable after placement in induced fractures. Proppants traced with different oxide concentrations were studied in a generic borehole-formation-tool configuration, modeled with MCNP. The Vaca Muerta formation model was constructed based on measured geochemical data. A theoretical formation of water-saturated limestone with 20% porosity was also used as a reference case of study. The minimum concentration of gadolinium and samarium oxides needed, in order to make them detectable by logging tools, was determined. In the case of gadolinium, results are in agreement with previous reported values for Gd₂O3 addition of about 0.4% by weight of proppant. In the case of samarium, a minimum concentration of 1.25% by weight of Sm₂O₃ addition could be detected in both Limestone and Vaca Muerta formations., Centro de Tecnología de Recursos Minerales y Cerámica

The neutron capture cross section of Be9 for stellar energies was measured via the activation technique using the Karlsruhe Van de Graaff accelerator in combination with accelerator mass spectrometry at the Vienna Environmental Research Accelerator. To characterize the energy region of interest for astrophysical applications, activations were performed in a quasistellar neutron spectrum of kT=25 keV and for a spectrum at En=473±53 keV. Despite the very small cross section, the method used provided the required sensitivity for obtaining fairly accurate results of 10.4±0.6 and 8.4±1.0μb, respectively. With these data it was possible to constrain the cross section shape up to the first resonances at 622 and 812 keV, thus allowing for the determination of Maxwellian-averaged cross sections at thermal energies between kT=5 and 100 keV. In addition, we report a new experimental cross section value at thermal energy of σth=8.31±0.52 mb.

In this paper we are proposing a re-evaluation of the thermal-neutron induced capture cross section of 147Nd. A unique measurement exists from which this cross section was calculated in 1974. This original calculation is based on an assumed value for a specific gamma-ray fraction (called F2), taken from the neighboring nucleus 145Nd. With the availability of reaction codes such as TALYS, such fraction can nowadays be calculated using specific reaction models and parameters. The new value of F2 indicates a decrease of the thermal cross section by 45%, leading to 243 barns, instead of the 440 barns previously reported. This new cross section impacts the calculation of the number density for the well-known burn-up indicator 148Nd, but as shown, the change is close to the usual experimental uncertainties for the 148Nd number densities, thus having a limited impact on burn-up calculation.

Evaluated nuclear structure and decay data for all nuclides with mass number A=183 (Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb) are presented here. At, Po and Fr have not yet been observed, but for prediction of ground state and/or isomer properties see, e.g., 2015Bh08 (At, Fr), 2013Ba41 (Tl), 2013Ho05 (Po). This evaluation includes structure and decay data information available by 15 April 2015 and supersedes that by R.B. Firestone published in Nuclear Data Sheets 65, 589 (1992) (literature cutoff 9 January 1991), and subsequent revisions by C.M. Baglin for 183Au in ENSDF database (literature cutoff 13 March 1999), 183Hg in Nuclear Data Sheets 91, 117 (2000) (literature cutoff 25 September 2000), 183Tl in Nuclear Data Sheets 95, 49 (2002) (literature cutoff 1 January 2002) and 183Pb in ENSDF (literature cutoff 6 January 2003). Since the prior Nuclear Data Sheets publication of this mass chain: 183Yb (2012Ku26) and 183Pb (2006An11, 2006Se18, 2007De09, 2009Se13) have been observed; our knowledge of high–spin states has been significantly expanded for 183Ta (2009Sh17), 183W (1999Sa60), 183Re (1998Ha51, 2001Sh41), 183Au (2002Jo18, 2005So01) and 183Tl (2001Mu26, 2004Ra28); a large amount of new structure information for 183W has been obtained from transfer reactions (1997Pr02, 2011Bo09), (n,n'γ) (1993Pr09) and thermal neutron capture (1993Pr09, 1997Pr02, 2011Bo09, 2014Hu02), as well as from the two–photon cascade study by 2005Su29.

Aim to present the most important aspects of Microdosimetry, a research field in radiation biophysics. Background microdosimetry is the branch of radiation biophysics that systematically studies the spatial, temporal and spectral aspects of the stochastic nature of the energy deposition processes in microscopic structures. Materials and Methods we briefly review its history, the people, the formalism and the theories and devices that allowed researchers to begin to understand the true nature of radiation action on living matter. Results and Conclusions we outline some of its applications, especially to Boron Neutron Capture Therapy, attempting to explain the biological effectiveness of the boron thermal neutron capture reaction.

A complete-spectroscopy investigation of low-lying, low-spin states in the one-proton-hole and one-neutron-hole nucleus 206Tl has been performed by using thermal neutron capture and γ-coincidence technique with the FIPPS Ge array at ILL Grenoble. The new experimental results, together with data for the one-proton-particle and one-neutron-particle nucleus 210Bi (taken from a previous study done at ILL in the EXILL campaign), allowed for an extensive comparison with predictions of shell-model calculations performed with realistic interactions. No phenomenological adjustments were introduced in the calculations. In 210Bi, state energies, transition multipolarities and decay branchings agree well with theory for the three well separated multiplets of states which dominate the low-lying excitations. On the contrary, in 206Tl significant discrepancies are observed: in the same energy region, six multiplets were identified, with a significant mixing among them being predicted, as a consequence of the smaller energy separation between the active orbitals. The discrepancies in 206Tl are attributed to the larger uncertainties in the determination of the off-diagonal matrix elements of the realistic shell-model interaction with respect to the calculated diagonal matrix elements, the only ones playing a major role in the case of 210Bi. The work points to the need of more advanced approaches in the construction of the realistic interactions. Keywords: Nuclear structure 206Tl, 210Bi, γγ-coin. 206Tl, Branching ratios 206Tl, Deduced levels and Jπ 206Tl, Comparison with shell-model calculations

In this paper, we present new spectroscopic information on Nb 94 from the Nb 93 ( n t h ,2γ) reaction. The intensities of the two-step gamma cascades in the compound nucleus Nb 94 to the final levels, with excitation energies below 400 keV, were derived from experimental spectra recorded at the PGAA facility of Centre for Energy Research (MTA EK), Budapest, Hungary. The intensities, energies of primary and secondary transitions of 216 energy-resolved cascades as well as intermediate cascade levels were determined. The part of the level scheme of Nb 94 was obtained from analyzing the intensity spectra of the strongest cascades. The results were compared to the existing data in the ENSDF database. We concluded that 27 primary transitions, 29 intermediate cascades levels as well as 183 secondary transitions can be recommended as new nuclear data.

This work provides new data about the level scheme of Mn 25 56 studied by the Mn 25 55 ( n t h ,2γ) reaction. The spectroscopic information were collected using the gamma-gamma coincidence spectrometer at the Technische Universitat Munchen, Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany. The intensities, energies of primary and secondary transitions of 71 energy-resolved cascades, as well as intermediate cascade levels were determined. The updated level scheme of Mn 25 56 was obtained from analyzing the intensity spectra of the strongest cascades. The comparison with the existing data in the ENSDF database shows that 23 primary transitions, 24 intermediate cascades levels as well as 32 secondary transitions determinated in this work can be recommended as new nuclear data.

The Westcott convention was introduced in the early 1990s in k 0-NAA to allow the analysis of nuclides whose thermal neutron capture cross-sections do not follow the “1/v”-law, so called “non-1/v” nuclides. Most affected nuclides are Lu-176, Eu-151 and Yb-169. Westcott introduced a neutron temperature dependent “g(T n )-factor” for the activation by thermal neutrons. Recently the extended Hogdahl convention was introduced in k 0-NAA for “non-1/v” nuclides using the same factor, emphasizing the interest in the analysis using these nuclides. This paper reviews most publications on “g(T n )-factors” for NAA and provides new factors based on the most recent evaluated nuclear database ENDF/B-VII.1.

We have measured the discrete $\gamma$ rays from thermal neutron capture on enriched gadolinium targets ($^{155}$Gd and $^{157}$Gd) using the ANNRI Germanium Spectrometer at JPARC. The photo-peak efficiencies were calibrated from 0.2 to 9 MeV using $\gamma$ rays from the standard radioactive sources ($^{60}$Co, $^{152}$Eu) and prompt $\gamma$ rays from $^{35}$Cl$(n,\gamma)$ reaction. We have calculated the relative intensities of discrete $\gamma$ rays from $^{157}$Gd$(n,\gamma)$ reaction. We found that our data are in fair agreement with the values published by NNDC (CapGam). We present the relative intensities of discrete $\gamma$ rays from $^{155}$Gd$(n,\gamma)$ reaction measured for the first time.

International audience; The low-spin structure of the 206Tl nucleus has been investigated with the FIPPS prompt γ-ray spectrometer of ILL making use of the 205Tl(n,γ)206Tl reaction and the γ-coincidence technique. A large number of excitations up to the neutron binding energy (at 6.5 MeV) in 206Tl were observed. Preliminary results of the data analysis provided the information on the decay scheme of the capture state in 206Tl and on the multipolarities of a number of γ rays. The comparison of the experimental data with shell-model calculations will help describing the proton–hole and neutron–hole couplings near the doubly magic core 208Pb, benchmarking single-particle levels and two-body matrix elements of the residual interaction in this important region of the nuclear chart.

Thermal neutron capture cross section and resonance integral for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction were measured by the activation method using the $^{197}$Au(n,$\gamma )^{198}$Au reaction as a single comparator. The high-purity scandium and gold samples with and without Cd cover with the thickness of 0.5 mm were irradiated in a pulsed neutron field of the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL). The induced activities in the activated foils were measured with a well calibrated HPGe detector. In order to improve the accuracy of the experimental results the effect of the non-ideal epithermal spectrum was taken in to account by determining the neutron spectrum shape factor ($\alpha )$, and the corrections for the thermal (G$_{th})$ and the resonance (G$_{epi})$ neutron self-shielding effects, the $\gamma $-ray attenuation (F$_{g})$ and the $\gamma $-ray coincidence summing effect were made. The thermal neutron cross-section for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction has been determined to be $\sigma _{o}$ = 27.6 $\pm $ 0.8 barn. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction has been determined to be I$_{o}$ = 12.7 $\pm $ 0.7 bar. The present results are compared with the reference data and discussed.

A feasibility study was carried out to evaluate the potential of the thermal neutron capture prompt-gamma activation analysis (PGAA) for the measurement of low levels of boron in selected Canadian and Japanese foods using the PGA facility at the JRR-3 reactor of the Japan Atomic Energy Agency (JAEA) in Tokai. A method was optimized for this purpose. It is rapid and can be used without any chemical separation. The precision and accuracy of the method are good. The detection limit is around 0.5 mg kg−1.

Proceedings of the 19th International Conference on Radionuclide Metrology and its Applications 17–21 June 2013, Antwerp, Belgium; International audience; During reactor operation (148g)Pm and (148m)Pm are formed in large quantities from thermal neutron capture on the fission product (147)Pm. Subsequent neutron capture reactions, on the (148)Pm ground state and isomer, have cross sections differing by a factor of 5 and so precise knowledge of their decay properties is vitally important. New decay scheme evaluations using the DDEP methodology for (148g)Pm and (148m)Pm are presented. The complete data tables and detailed evaluator comments are available through the DDEP website.

Thermal neutron capture cross sections and resonance integrals of 96Ru, 102Ru and 104Ru are measured with reference to a 55Mn monitor. The experiments are carried out using the neutrons from an Am-Be neutron source kept inside a concrete bunker. The thermal neutron capture cross sections measured are in good agreement with the evaluations as well as with one of the recent measurements. The resonance integral of 102Ru measured in the present study is in good agreement with older measurements.

Nitrogen concentration was measured in explosive and narcotics proxy material, e.g. anthranilic acid, caffeine, melamine, and urea samples, bulk samples through thermal neutron capture reaction using 350 keV accelerator based prompt gamma ray neutron activation (PGNAA) setup. Intensity of 2.52, 3.53–3.68, 4.51, 5.27–5.30 and 10.38 MeV prompt gamma rays of nitrogen from the bulk samples was measured using a cylindrical 100 mm×100 mm (diameter×height ) BGO detector. Inspite of interference of nitrogen gamma rays from bulk samples with capture prompt gamma rays from BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays has been obtained. This is an indication of the excellent performance of the PGNAA setup for detection of nitrogen in bulk samples.

Ultrapure hafnium metal (110 ppm zirconium) was neutron activated with a thermal neutron flux of 6:6 · 1012 cm-2s-1 in order to obtain 181Hf for subsequent time differential perturbed angular correlation (TDPAC) experiments using the nuclear probe 181Hf(β-) 181Ta. Apart from the expected nuclear quadrupole interaction (NQI) signal for a hexagonal close-packed (hcp) metal, three further discrete NQIs were observed with a few percent fraction each. The TDPAC spectra were recorded for up to 11 half lives with extreme statistical accuracy. The fitted parameters vary slightly within the temperature range between 248 K and 373 K. The signals corresponding to the three additional sites completely disappear after ‘annealing’ at 453 K for one minute. Based on the symmetry of the additional NQIs and their temperature dependencies, they are tentatively attributed to Frenkel pairs produced by recoil due to the emission of a prompt 5:694 MeV -ray following thermal neutron capture and reported by the nuclear probe in three different positions. These Frenkel pairs are stable up to at least 373 K.

Radiative thermal neutron capture cross sections over the range of thermal energies from 1 keV to 1 MeV are studied in the statistical Hauser-Feshbach formalism. The optical model potential is constructed by folding the density-dependent M3Y nucleon-nucleon interaction with radial matter densities of target nuclei obtained from relativistic-mean-field (RMF) theory. The standard nuclear reaction code talys1.8 is used for calculation of cross sections. The nuclei studied in the present work reside near the $Z=28$ proton shell closure and are of astrophysical interest, taking part in $p,\phantom{\rule{0.16em}{0ex}}s$, and $r$ processes of nucleosynthesis. The Maxwellian-averaged cross-section (MACS) values for energies important for astrophysical applications are presented.

Partial $\ensuremath{\gamma}$-ray production cross sections and the total radiative thermal-neutron capture cross section for the $^{185}\mathrm{Re}(n,\ensuremath{\gamma})^{186}\mathrm{Re}$ reaction were measured using the Prompt Gamma Activation Analysis facility at the Budapest Research Reactor with an enriched $^{185}\mathrm{Re}$ target. The $^{186}\mathrm{Re}$ cross sections were standardized using well-known $^{35}\mathrm{Cl}(n,\ensuremath{\gamma})^{36}\mathrm{Cl}$ cross sections from irradiation of a stoichiometric ${}^{\text{nat}}{\text{ReCl}}_{3}$ target. The resulting cross sections for transitions feeding the $^{186}\mathrm{Re}$ ground state from low-lying levels below a cutoff energy of ${E}_{c}=746\phantom{\rule{4.pt}{0ex}}\text{keV}$ were combined with a modeled probability of ground-state feeding from levels above ${E}_{c}$ to arrive at a total cross section of ${\ensuremath{\sigma}}_{0}=111(6)\phantom{\rule{4.pt}{0ex}}\text{b}$ for radiative thermal-neutron capture on $^{185}\mathrm{Re}$. A comparison of modeled discrete-level populations with measured transition intensities led to proposed revisions for seven tentative spin-parity assignments in the adopted level scheme for $^{186}\mathrm{Re}$. Additionally, 102 primary $\ensuremath{\gamma}$ rays were measured, including 50 previously unknown. A neutron-separation energy of ${S}_{n}=6179.59(5)\phantom{\rule{4.pt}{0ex}}\text{keV}$ was determined from a global least-squares fit of the measured $\ensuremath{\gamma}$-ray energies to the known $^{186}\mathrm{Re}$ decay scheme. The total capture cross section and separation energy results are comparable to earlier measurements of these values.

The cross section of the neutron capture reaction $^{176}\mathrm{Lu}(n,\ensuremath{\gamma})$ has been measured for a wide incident neutron energy range with the Detector for Advanced Neutron Capture Experiments at the Los Alamos Neutron Science Center. The thermal neutron capture cross section was determined to be $(1912\ifmmode\pm\else\textpm\fi{}132)$ b for one of the Lu natural isotopes, $^{176}\mathrm{Lu}$. The resonance part was measured and compared to the Mughabghab's atlas using the $R$-matrix code, sammy. At higher neutron energies the measured cross sections are compared to ENDF/B-VII.1, JEFF-3.2, and BRC evaluated nuclear data. The Maxwellian averaged cross sections in a stellar plasma for thermal energies between 5 keV and 100 keV were extracted using these data.

A subject of this thesis is to gain information on absolute photon strength function below the neutron separation energy. This energy range is known as a "low-tail" energy region of E1 resonance. The absolute photon strength function is obtained by normalizing the total average intensity for several energy ranges to the average intensities from thermal neutron capture spectrum for which an absolute calibration is experimentally known. The absolute photon strength function is investigated by means of statistical method. Everything seems to be compatible with information on studied Gd isotopes. However, disclosed method can potentially lead to rejection of combination of PSF and LD models. Powered by TCPDF (www.tcpdf.org)

Various Li compounds are commonly used at neutron facilities as neutron absorbers. These compounds provide one of the highest ratios of neutron attenuation to $\gamma$-ray production. Unfortunately, the usage of these compounds can also give rise to fast neutron emission with energies up to almost 16 MeV. Historically, some details in this fast neutron production mechanism can be absent from some modeling packages under some optimization scenarios. In this work, we tested Geant4 to assess the performance of this simulation toolkit for the fast neutron generation mechanism. We compare the results of simulations performed with Geant4 to available measurements. The outcome of our study shows that results of the Geant4 simulations are in good agreement with the available measurements for $^6$Li fast neutron production, and suitable for neutron instrument background evaluation at spallation neutron sources., Comment: 6 pages, 3 figures, Proceeding of The Sixth European Conference on Neutron Scattering, Zaragoza Spain, August 30 to September 4 2015

The high value of the cross section of thermal neutron capture by the 113Cd nucleus allows us to regard cadmium-loaded organic scintillators as an alternative to gadolinium-loaded analogues. We report on new plastic and liquid scintillators with maximum metal concentrations of 2 and 1.5 wt %, respectively. Transmission spectra, scintillation characteristics, and efficiencies of the registration of thermal neutrons are given.