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Efficiency calibration of HPGe detector in a PGNAA system for the measurement of aqueous samples
摘要： In this work, a method was proposed for e?ciency calibration of HPGe detector employed in a prompt gamma-ray neutron activation analysis (PGNAA) system for large aqueous sample analysis. Experimental measurements of a reference surface gamma-ray source were combined with e?ciency transfer method to obtain e?ciency of a volumetric source. Then e?ciency curve over the energy range 0.5–8.5 MeV were determined with prompt gamma-rays of chlorine. To evaluate the performance of the calibration curve, an internal standard method was used to determine the aqueous sample containing manganese based on the calibration curve. The 7.058 MeV and 7.243 MeV manganese gamma-ray peaks were used to calculate the mass of manganese. The relative deviations of calculated values and actual value were 5.0% and 6.5%, respectively.
关键词： Prompt gamma-ray neutron activation analysis,E?ective solid angle,Large volumetric sample,Gamma-ray e?ciency calibration
更新于2025-09-04 15:30:14
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films
摘要： Noncollinear magnetism can play an important role in multiferroic materials but is relatively understudied in oxide heterostructures compared to their bulk counterparts. Using variable temperature magnetometry and neutron diffraction, we demonstrate the presence of helical magnetic ordering in CaMn7O12 and Ca1?xSrxMn7O12 (for x up to 0.51) thin ?lms. Consistent with bulk Ca1?xSrxMn7O12, the net magnetization increases with Sr doping. Neutron diffraction con?rms that the helical magnetic structure remains incommensurate at all values of x, while the fundamental magnetic wavevector increases upon Sr substitution. This result demonstrates a chemical-based approach for tuning helical magnetism in quadruple perovskite ?lms and enables future studies of strain and interfacial effects on helimagnetism in oxide heterostructures.
关键词： helical magnetism,oxide heterostructures,magnetometry,Sr-doped CaMn7O12,neutron diffraction
更新于2025-09-04 15:30:14
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Extent of embossing-related residual stress on the magnetic properties evaluated using neutron grating interferometry and single sheet test
摘要： Due to the permanently increasing maximum speed of modern electric machines, the mechanical load on the electrical steel rises. The punched flux barriers of reluctance machines play an increasingly key role in the mechanical design. The weakening of the material and the notching effect can cause local failure due to centrifugal force. In this paper, a method is presented which induces residual stresses by embossing electrical steel laminations, which contribute to the guidance of the magnetic flux and cause a negligible mechanical weakening of the sheet. The aim of this paper is to demonstrate the effectiveness of these embossed flux barriers. This is achieved by using neutron grating interferometry, that allows the density of the magnetic domains to be resolved locally. Furthermore the influence of the embossing is mapped globally by single sheet tests. The finite element analysis of the forming process derives the residual stress distribution which is responsible for the measured magnetic behavior. In order to isolate the influence of the residual stress, non-embossed and stress-relief annealed specimens are used as a reference for both measurement methods.
关键词： Electrical steel,Forming,Electric drives,Neutron grating,Production,Single sheet tester,Mechanical stress,Embossing
更新于2025-09-04 15:30:14
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Reversible Control of Physical Properties via an Oxygen-Vacancy-Driven Topotactic Transition in Epitaxial La <sub/>0.7</sub> Sr <sub/>0.3</sub> MnO <sub/>3?</sub><i> <sub/>δ</sub></i> Thin Films
摘要： The vacancy distribution of oxygen and its dynamics directly affect the functional response of complex oxides and their potential applications. Dynamic control of the oxygen composition may provide the possibility to deterministically tune the physical properties and establish a comprehensive understanding of the structure–property relationship in such systems. Here, an oxygen-vacancy-induced topotactic transition from perovskite to brownmillerite and vice versa in epitaxial La0.7Sr0.3MnO3?δ thin films is identified by real-time X-ray diffraction. A novel intermediate phase with a noncentered crystal structure is observed for the first time during the topotactic phase conversion which indicates a distinctive transition route. Polarized neutron reflectometry confirms an oxygen-deficient interfacial layer with drastically reduced nuclear scattering length density, further enabling a quantitative determination of the oxygen stoichiometry (La0.7Sr0.3MnO2.65) for the intermediate state. Associated physical properties of distinct topotactic phases (i.e., ferromagnetic metal and antiferromagnetic insulator) can be reversibly switched by an oxygen desorption/absorption cycling process. Importantly, a significant lowering of necessary conditions (temperatures below 100 °C and conversion time less than 30 min) for the oxygen reloading process is found. These results demonstrate the potential applications of defect engineering in the design of perovskite-based functional materials.
关键词： La0.7Sr0.3MnO3 films,polarized neutron reflectometry,brownmillerite,oxygen vacancy ordering,magnetism
更新于2025-09-04 15:30:14
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Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility
摘要： A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the 198Au/196Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.
关键词： cryogenic inertial confinement fusion,neutron down scatter ratio,National Ignition Facility,areal densities,fuel-ablator mix,plastic ablator,deuterium-tritium fuel,radiochemical method,Au hohlraum
更新于2025-09-04 15:30:14