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DOE OSTI2013

Nuclear Data Sheets for A = 89

The evaluated experimental data are presented for 14 known nuclides of mass 89 (Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh). New data on high–spin excitations are available for {sup 89}Kr, {sup 89}Rb, {sup 89}Sr, {sup 89}Tc and {sup 89}Ru, including a superdeformed structure in {sup 89}Tc. Fluorescence studies in {sup 89}Y have revealed a large number of new levels in 7–11 MeV range. New two–neutron transfer data are available for {sup 89}Zr. New direct and precise measurement of atomic masses of {sup 89}Se, {sup 89}Br, 89{sup K}r, {sup 89}Rb, {sup 89}Mo and {sup 89}Tc have greatly improved the Q value landscape in this mass region. This work supersedes previous A=89 evaluation published in 1998Si31, and also the older ones 1989Si20, 1975Ko21, and M.W. Johns et al., Nuclear Data Tables A 8, 373 (1970). In spite of extensive experimental work on the isobaric nuclei of this mass chain several deficiencies remain. The identification of {sup 89}Rh isotope remains unconfirmed. The half–lives of ground states of {sup 89}Ge, {sup 89}As and {sup 89}Rh have not been measured, only the lower limits are estimated from time–of–flight in a reaction and experimental arrangement, where produced and identified. The decay schemes of {sup 89}Ge, {sup 89}As, {sup 89}Se, {sup 89}Ru and {sup 89}Rh are not known, and those for {sup 89}Tc and {sup 89}Mo are incomplete. High–lying (neutron unbound) levels in {sup 89}Kr, expected to be populated in the decay of {sup 89}Br, have not been investigated. The spins and parities for levels in {sup 89}Kr are largely unassigned, while for {sup 89}Tc and {sup 89}Ru, only few low–spin excitations are established. For {sup 89}Rb, little information is available for high–spin structures. Detailed gamma–ray data are available for {sup 88}Sr(n,γ){sup 89}Sr reaction, but most of these γ rays remain unassigned in a level scheme. Excited state data are nonexistent for {sup 89}Ge, {sup 89}As, {sup 89}Se, {sup 89}Br and {sup 89}Rh. The {sup 89}Y and {sup 89}Zr are the most extensively studied nuclei in A=89.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Benchmarking of activation rate in special core in LR-0 reactor

The experiments focused on the determination of activation reaction rates of selected IRDFF materials activated in a well-defined special core assembled in the LR-0 reactor are presented in the paper. The used core is designed and verified for IRDFF library testing by reactivity characterization, fission rates distribution and also neutron spectra measurement at the center of the core. {sup 23}Na(n,2n), {sup 75}As(n,2n), {sup 89}Y(n,2n) and {sup 90}Zr(n,2n) reaction cross sections were measured in this special core. The presented neutron cross sections were derived from experimentally determined reaction rates of irradiated samples of NaF, As{sub 2}O{sub 3}, Y{sub 2}O{sub 3}, and ZrO{sub 2}. These reaction rates are derived from gamma activities of the activation products of studied activation reactions. Net Peak Areas (NPA) of photons accompanying decay were measured using a semiconductor High Purity Germanium (HPGe) detector. Despite the fact that mentioned reactions have a threshold above 10 MeV, where the neutron spectrum in the special LR-0 core is nearly undistinguishable from {sup 235}U prompt fission neutron spectrum, the measured integral cross sections averaged in LR-0 spectrum were corrected for spectral shift. The obtained values of {sup 235}U spectral average cross section are: (3.84 ± 0.19) μb for {sup 23}Na(n,2n); (0.320 ± 0.015) mb for {sup 75}As(n,2n); (0.171 ± 0.006) mb for {sup 89}Y(n,2n); (0.107 ± 0.005) mb for {sup 90}Zr(n,2n). (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2022

Beam particle identification and tagging of incompletely stripped heavy beams with HEIST

A challenge preventing successful inverse kinematics measurements with heavy nuclei that are not fully stripped is identifying and tagging the beam particles. For this purpose, the HEavy ISotope Tagger (HEIST) has been developed. HEIST utilizes two micro-channel plate timing detectors to measure the time-of-flight, a multi-sampling ion chamber to measure energy loss, and a high-purity germanium detector to identify isomer decays and calibrate the isotope identification system. HEIST has successfully identified 198 Pb and other nearby nuclei at energies of about 75 MeV/A. In the experiment discussed, a typical cut containing 89% of all 198 Pb 80+ in the beam had a purity of 86%. We examine the issues of charge state contamination. Here, the observed charge state populations of these ions are presented and, using an adjusted beam energy, are well described by the charge state model GLOBAL.

47 OTHER INSTRUMENTATION↗

DOE OSTI2018

Spectral-average cross section validation in LR-0 reactor spectrum of {sup 55}Mn(n,2n), {sup 90}Zr(n,2n) and {sup 127}I(n,2n) reactions - 25362

This article deals with the validation of spectral average cross-sections (SACS) of {sup 55}Mn(n,2n){sup 54}Mn, {sup 90}Zr(n,2n){sup 89}Zr and {sup 127}I(n,2n){sup 126}I reactions in well-defined LR-0 reactor spectrum. The measurement of SACS for selected reactions is of high interest because they are used for the practical reactor dosimetry and also for refinement of prompt fission neutron spectra of {sup 235}U in the region of higher energies. Various experiments for description of neutron field in reactor and detector characterization, which are necessary for validation, are described. The spectral average cross-sections are derived from Net Peak Areas of irradiated samples measured using a semiconductor high purity germanium detector. The spectral average cross section in {sup 235}U prompt fission neutron spectrum was experimentally determined to be 0.239 ± 0.015 mb for {sup 55}Mn, 1.209 ± 0.052 mb for {sup 127}I and 0.107 ± 0.005 mb for {sup 90}Zr. The obtained results were compared with MCNP6 calculations using ENDF/B-VII.0, ENDF/B-VII.1, JEFF-3.1, JEFF-3.2, JENDL-3.3, JENDL-4, ROSFOND-2010, CENDL-3.1 and IRDFF-1.05 nuclear data libraries. Notable discrepancies were found in {sup 90}Zr(n,2n){sup 89}Zr and {sup 127}I(n,2n){sup 126}I reactions. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2019

Improved Cumulative Fission Yield Measurements with Fission Spectrum Neutrons on 235 U

Two isotopically-characterized targets of high-purity (99.84±0.03%) 235 U-oxide and a neutron dosimetry package were exposed to a pulsed neutron irradiation using the Godiva critical assembly at the National Criticality Experiments Research Center. Following irradiation, the fissioned targets were counted with a broad-energy germanium detector. Estimates of the total fissions for each target were made using measurements of well-known fission products. The total fission values were then used to measure the fission yields of 21 fission products with half-lives between 636 and 119,700 seconds. Mean values of seventeen of the measured fission products fell within the 95% confidence level of the Evaluated Nuclear Data Files VII.1/b (ENDF/B-VII.1) using the larger of the two uncertainties: 84g Br, 89 Rb, 91 Sr, 93 Y, 97 Zr, 101 Mo, 105 Ru, 128 Sn, 129 Sb, 130g Sb, 131 Sb, 131m Te, 133 I, 135 I, 141 Ba, 142 Ba, and 142 La. Seven isotopes were measured to better precision than is listed in the ENDF/B-VII.1 database: 89 Rb, 93 Y, 128 Sn, 129 Sb, 130g Sb, 131m Te, and 133 I. Four of the measured isotopes were found to be statistically different from the ENDF/B-VII.1 database: 94 Y, 134 Te, 134 I, and 138 Xe. Two of the isotopic analyses conducted in this paper fit the parent and daughter data simultaneously. The parent-daughter pairs measured in this way were the 134 Te/I and 142 Ba/La pairs. The fission yield results obtained in this way are unique, especially for 134 I, because the parent and daughter half-lives are so close. Here, given the limited number of direct measurements of the 134 Te/I pair from fast neutron induced fission and the seemingly high estimate for 134 Te from previous work, it is likely that the value in this paper is more accurate; however, additional measurements of this pair are needed to validate this assertion.

42 ENGINEERING↗

DOE OSTI2022

Non‐Linear Optical Properties of the ( RE ) 3 CuGeS 7 Family of Compounds

Abstract Non‐linear optical materials must possess a balanced combination of laser‐induced damage threshold (LDT) and second‐harmonic generation (SHG) and be phase matchable. In our previous work, chiral and polar La 3 CuGeS 7 was identified as a promising non‐linear optical material. Herein, we report the optimization of non‐linear optical properties through replacement of La with smaller lanthanides. It is determined that Gd 3 CuGeS 7 exhibits the best combination of SHG (1.6× AgGaS 2 at 88–105 μm particle size) and LDT (3× AgGaS 2 , 89 MW/cm 2 ) and is phase matchable. Based on changes in metal‐sulfur bond lengths and angles, we further propose structural optimization through solid‐solution formation and doping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Low-energy enhancement in the γ -ray strength functions of Ge 73 , 74

Here, t≤he γ-ray strength functions and level densities of 73,74 Ge have been extracted up to the neutron-separation energy S n from particle-γ coincidence data using the Oslo method. Moreover, the γ-ray strength function of 74 Ge above S n has been determined from photoneutron measurements; hence these two experiments cover the range of Eγ ≈ 1–13 MeV for 74 Ge. The obtained data show that both 73,74 Ge display an increase in strength at low γ energies. The experimental γ-ray strength functions are compared with M1 strength functions deduced from average B(M1) values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in 73,74 Ge are adopted in the calculations of the 72,73 Ge(n,γ) cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2014

Thickness effect on the structural and electrical properties of poly-SiGe films

Graphical abstract: - Highlights: • Stress and Young's modulus of poly-SiGe film are linked to the grain columnar structure. • The above properties remain unchanged for poly-SiGe films thicker than 40 nm. • The point of transition is close to the electron mean free path for SiGe. • Both the resistivity and Hall mobility follow a similar trend. - Abstract: As lateral dimensions of electromechanical devices are scaled down to length scales comparable to electron mean free paths, the influence of thickness effect on their properties becomes sine qua non. This paper presents a detailed study of thickness effect on the Young's modulus, residual stress, resistivity and Hall mobility of ultrathin poly-Si{sub 11}Ge{sub 89} films deposited by low pressure chemical vapour deposition. The Young's moduli for the films thicker than ∼40 nm are close to the bulk value (135 GPa) while those of the thinner films are much lower. The reduction in resistivity and subsequent improved Hall mobility as thickness increases are discussed in light of surface morphology which is evident from atomic microscopy images. The near constant values of Young's modulus, resistivity and Hall mobility for the films thicker than ∼40 nm are attributed to the columnar grain structure as confirmed by the transmission electron microscopy images.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Model-independent determination of the dipole response of 66 Zn using quasimonoenergetic and linearly polarized photon beams

Background: Photon strength functions are an important ingredient in calculations relevant for the nucleosynthesis of heavy elements. The relation to the photoabsorption cross section allows to experimentally constrain photon strength functions by investigating the photoresponse of atomic nuclei. Purpose: Here, we determine the photoresponse of 66 Zn in the energy region of 5.6 MeV to 9.9 MeV and analyze the contribution of the 'elastic' decay channel back to the ground state. In addition, for the elastic channel electric and magnetic dipole transitions were separated. Methods: Nuclear resonance fluorescence experiments were performed using a linearly polarized quasi-monoenergetic photon beam at the High Intensity γ-ray Source. Photon beam energies from 5.6 to 9.9 MeV with an energy spread of about 3% were selected in steps of 200–300 keV. Two high purity germanium detectors were used for the subsequent γ-ray spectroscopy. Results: Full photoabsorption cross sections are extracted from the data making use of the monoenergetic character of the photon beam. For the ground-state decay channel, the average contribution of electric and magnetic dipole strengths is disentangled. The average branching ratio back to the ground state is determined as well. Conclusions: The new results indicate lower cross sections when compared to the values extracted from a former experiment using bremsstrahlung on 66 Zn. In the latter, the average branching ratio to the ground state is estimated from statistical-model calculations in order to analyze the data. Corresponding estimates from statistical-model calculations underestimate this branching ratio compared to the values extracted from the present analysis, which would partly explain the high cross sections determined from the bremsstrahlung data.

59 ≤ A ≤ 89↗

DOE OSTI2024

Observation of collective modes of excitations in 59 Co, 59 Ni, and 61 Co and the influence of the $g_{9/2}$ orbital

High-spin states in 59 Co (Z = 27), 59 Ni (Z = 28), and 61 Co have been populated by the fusion evaporation reactions, 48 Ti( 14 C, p2n ) 59 Co, 48 Ti( 14 C, 3 n ) 59 Ni, and 50 Ti( 14 C, p2n ) 61 Co. The 9 MV tandem accelerator at the John D. Fox Laboratory, Florida State University (FSU) was used to accelerate the 14 C beam and the deexciting γ rays were detected by the FSU detector array consisting of six high-purity germanium (HPGe) clover detectors and three single crystals. Directional correlation of the $γ$ rays deexciting oriented states (DCO ratios) and polarization asymmetry measurements helped to establish spin and parities of the excited states whenever possible. The level scheme of 59 Co has been expanded with the inclusion of positive-parity states up to 31/2 + at around 11 MeV. The 59 Ni positive-parity states known from previous study were verified with modifications to some of the spins and parities. On the other hand, the negative-parity states were extended to 31/2 at an excitation energy of 12 MeV. No new transition was observed for 61 Co, but one of the major bands has been reassigned as consisting of positive-parity states by reason of this study. Importantly, excitations observed within the f 7/2 , p 3/2 , f 5/2 , and p 1/2 orbitals, and also across the N = 40 subshell closure into the g 9/2 orbital was established by comparison with large-scale shell-model calculations for the three nuclei studied.

59 ≤ A ≤ 89↗

DOE OSTI2019

Multisite event discrimination for the majorana demonstrator

The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay($0\nu\beta\beta$) in 76 Ge using arrays of point-contact germanium detectors operating at the Sanford Underground Research Facility. Background results in the $0\nu\beta\beta$ region of interest from data taken during construction, commissioning, and the start of full operations have been recently published. A pulse shape analysis cut applied to achieve this result, named AvsE , is described in this paper. This cut is developed to remove events whose waveforms are typical of multi-site energy deposits while retaining (90 ± 3.5)% of single-site events. This pulse shape discrimination is based on the relationship between the maximum current and energy, and tuned using 228 Th calibration source data. In conclusion, the efficiency uncertainty accounts for variation across detectors, energy, and time, as well as for the position distribution difference between calibration and $0\nu\beta\beta$ events, established using simulations.

59 ≤ A ≤ 89↗

DOE OSTI2021

Search for double-β decay of 76 Ge to excited states of 76 Se with the Majorana Demonstrator

The M AJORANA DEMONSTRATOR is a neutrinoless double-β decay search consisting of a low-background modular array of high-purity germanium detectors, ~2/3 of which are enriched to 88% in 76 Ge. The experiment is also searching for double-beta decay of 76 Ge to excited states (e.s.) in 76 Se. 76 Ge can decay into three daughter states of 76 Se, with clear event signatures consisting of a ββ-decay followed by the prompt emission of one or two γ rays. This results with high probability in multi-detector coincidences. In this work, the granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9 kg yr of isotopic exposure, the DEMONSTRATOR has set world leading limits for each e.s. decay of 76 Ge, with 90% CL lower half-life limits in the range of (0.75–4.0) × 10 24 yr. In particular, for the 2ν transition to the first 0 + e.s. of 76 Se, a lower half-life limit of 7.5 × 10 23 yr at 90% CL was achieved.

59 ≤ A ≤ 89↗