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Measurement of ionization produced by 254 eVnr nuclear recoils in germanium

Physical Review D 2024年第8期110卷 083043页

作者： A. R. L. Kavner I. Jovanovic Applied Physics Program Department of Nuclear Engineering and Radiological Sciences

Ionization produced by low-energy nuclear recoils is among the primary direct signatures of dark matter interactions. Despite the urgency of dark matter detection and the recent measurements of coherent elastic neutrino-nucleus scattering, detector response to nuclear recoils is not well characterized in the keVnr and sub−keVnr regime across a variety of materials. We have reperformed a measurement of the ionization produced by monoenergetic 254 eVnr nuclear recoils in Ge with improved digital electronics and additional systematic studies. Our results indicate an ionization yield of 64±8 eVee corresponding to a quenching factor of 25%±3%, greater than the 14% predicted by the Lindhard model. This ionization enhancement could greatly improve the sensitivity of high-purity Ge detectors in dark matter detection and measurement of neutrinos via coherent scattering.

关键词： Dark matter Dark matter direct detection Energy levels Neutron physics nuclear astrophysics Particle dark matter

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Computational Modeling of Radiation Effects in Carbon Fiber-Reinforced Polyethylene Composites 38

Computational Modeling of Radiation Effects in Carbon Fiber-...

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38th Technical Conference of the American Society for Composites, ASC 2023

作者： Li, Fuyue Woodrough, Mary Deo, Chaitanya School of Materials Science and Engineering Georgia Institute of Technology North Avenue AtlantaGA30332 United States Nuclear and Radiological Engineering Program GWW School of Mechanical Engineering Georgia Institute of Technology North Avenue AtlantaGA30332 United States

ISBN: (纸本)9781605956916

Radiation effect in carbon fiber-filled polyethylene composites are of importance in space and aircraft applications. A two-fold approach is employed to study radiation effects in carbon nanotube polyethylene as the exemplar. First, a radiation transport model is created with a single-wall carbon nanotube (SWCNT) as thin carbon slab superimposed on a slab of medium-density polyethylene matrix. Different weight fractions of SWCNT are examined and compared with an integrated model for the shielding abilities of galactic cosmic radiation. Second, molecular dynamics simulation with bond-order force field are conducted for 350 eV carbon recoil cascade simulation. Preliminary results discuss the effect of SWCNT on the radiation damage of crystalline polyethylene. Transport simulation demonstrate the efficacy of the slab model in predicting the shielding abilities and concluded that the dose increases with increasing SWCNT filler. Molecular dynamics simulations demonstrate that adding SWCNT enhances the radiation resistance with fewer free molecules produced. © 2023 by DEStech Publications, Inc. and American Society for Composites. All rights reserved.

关键词： Single-walled carbon nanotubes (SWCN)

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A Comprehensive Measurement of Bubbly Flow in a 30 mm × 10 mm Rectangular Channel 20

A Comprehensive Measurement of Bubbly Flow in a 30 mm × 10 ...

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20th International Topical Meeting on nuclear Reactor Thermal Hydraulics, NURETH 2023

作者： Wang, Dewei Fu, Yucheng Sun, Hanxing Liu, Yang Liu, Qingqing Liu, Yang Sun, Xiaodong Worosz, Ted Buchanan, John Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Price Fork Road BlacksburgVA24061 United States Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd Ann ArborMI48109 United States Naval Nuclear Laboratory PO Box 79 West MifflinPA15122 United States

ISBN: (纸本)9780894487934

One major obstacle hindering the advancement of modeling and simulation capabilities of two-phase flows is the lack of high-quality, high-resolution experimental data for model development and model/code validation. To close this gap, this study aims to obtain a high-fidelity local two-phase flow dataset in a vertical 30 mm × 10 mm rectangular channel. A system combining the double-sensor conductivity probe and high-speed imaging technique is utilized to obtain the gas-phase data. The double-sensor conductivity probe measures the local time-averaged two-phase flow parameters over the cross-section, while a multi-camera imaging system captures the bubble shape, orientation, and size information. This information is then used as the input to a Monte Carlo reconstruction program to evaluate and eliminate the known systematic uncertainties in the probe measurement. The Particle Image Velocimetry and Planar Laser-Induced Fluorescence (PIV-PLIF) technique is employed as the main tool for the liquid-phase measurement. The acquired dataset covers three bubbly flow conditions measured at three axial locations to capture the flow development. The superficial gas and liquid velocities range from 0.03 to 0.25 m/s and from 0.8 to 3 m/s, respectively. The measured local data include the time-averaged void fraction, bubble velocity, interfacial area concentration, bubble frequency, liquid velocity, and turbulence quantities. The data show that the void fraction distributions for each run can exhibit quite different profiles which also evolve along the test section. However, both the gas-phase and liquid-phase velocity data show quite uniform distributions across much of the cross-sectional plane and show little dependence on the void fraction distribution for the two-phase flows studied in this paper. © 2023 Proceedings of the 20th International Topical Meeting on nuclear Reactor Thermal Hydraulics, NURETH 2023. All rights reserved.

关键词： Two phase flow

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A 3-D Imaging System for Bubbly Flow Measurement 20

A 3-D Imaging System for Bubbly Flow Measurement

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20th International Topical Meeting on nuclear Reactor Thermal Hydraulics, NURETH 2023

作者： Fu, Yucheng Wang, Dewei Liu, Yang Sun, Xiaodong Worosz, Ted Buchanan, John Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Price Fork Road BlacksburgVA24061 United States Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd Ann ArborMI48109 United States Naval Nuclear Laboratory PO Box 79 West MifflinPA15122 United States

ISBN: (纸本)9780894487934

Image processing algorithms capable of extracting two-phase flow quantities automatically from high-speed images have been under continuous development over the past few decades. In a typical imaging setup, a single high-speed camera is used to capture the two-phase flow information projected to the imaging plane. However, the bubble depth information is not recorded in the images with this configuration, and the bubble volume and surface area need to be estimated with additional shape assumptions. To address such limitations, a stereo imaging system has been developed in this study to acquire 3-D bubbly flow information without the need for bubble depth or shape assumptions. The newly developed system positions three high-speed cameras at different angles, which allows for accurate measurements of the 3-D location of bubbles in a flow field. The previously developed 2-D image processing algorithm is used to obtain three projected silhouettes of individual bubbles from three cameras. The realistic shape of each bubble is then reconstructed from the silhouettes using the 3-D space carving method, which in turn gives accurate measurements of bubble volume and surface area. The time-averaged number density, void fraction, and interfacial area concentration distributions over the cross-sectional plane can be then obtained with a measurement lasting a few tens of seconds by the imaging system. Using this system, three bubbly flow tests have been carried out in a 30 mm × 10 mm rectangular channel with varying superficial liquid and gas velocities. The system could capture both wall-peaked and center-peaked void fraction distributions. The comparison with gas flowmeter measurement shows a reasonable agreement in measuring the area-averaged superficial velocities. This work demonstrates several advantages of the newly developed imaging system such as high temporal and spatial resolutions, great measurement efficiency, and improved accuracy due to its non-intrusive nature. ©

关键词： Two phase flow

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Experimental Study and CFD Simulation of Air-Water Bubbly Flow in a Rectangular Channel 20

Experimental Study and CFD Simulation of Air-Water Bubbly Fl...

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20th International Topical Meeting on nuclear Reactor Thermal Hydraulics, NURETH 2023

作者： Liu, Qingqing Liu, Yang Sun, Xiaodong Wang, Dewei Liu, Yang Buchanan, John Worosz, Ted Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd Ann ArborMI48109-2104 United States Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Price Fork Road BlacksburgVA24061 United States Naval Nuclear Laboratory PO Box 79 West MifflinPA15122 United States

ISBN: (纸本)9780894487934

This paper presents an experimental study that measures the liquid-phase velocity and turbulence in upward air-water two-phase flow using a particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) system. The test section is a vertical 30 mm × 10 mm rectangular channel with a height of 3.0 m. Experimental data were collected at three instrumentation ports along the test section with the normalized axial distances of z/Dh = 8.8, 72.4, and 136.0 from the exit of a two-phase flow injector. Three bubbly flow conditions were studied with the gas and liquid superficial velocities ranging from 0.03 to 0.25 m/s and from 0.8 to 3.0 m/s, respectively. The void fraction was measured by double-sensor conductivity probes. The two-dimensional (2-D) distributions of the local time-averaged liquid velocity, Reynolds stress, turbulence kinetic energy (TKE), and turbulence intensity were obtained from the PIV-PLIF measurements. This study adds a dataset of 2-D liquid-phase velocity and turbulence measurements in bubbly flows to the literature, which could assist with two-phase turbulence model development as well as two-phase high-fidelity computational model/code assessment and validation. In addition, multiphase computational fluid dynamics (MCFD) simulations were performed using ANSYS FLUENT for the three bubbly flows in the rectangular flow channel. The Eulerian-Eulerian multiphase approach with the k-ω shear stress transport turbulence model was used in the MCFD simulations. In general, the relative differences between the experimental data and simulation results for the local liquid velocity are less than 10% in the central region of the flow channel but can be up to 25% near the wall region. The MCFD code predicts the Reynolds normal stress in the spanwise direction more accurately than that in the streamwise direction. It also predicts the Reynolds shear stress relatively well in the central region but not as good in the near-wall region. © 2023 Proceedings of

关键词： Computational fluid dynamics

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Ultrafast Excitation of Xenon in Tight and Loose Focusing Configurations

Ultrafast Excitation of Xenon in Tight and Loose Focusing Co...

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2023 Conference on Lasers and Electro-Optics, CLEO 2023

作者： Burger, M. Latty, K.S. Hartig, K.C. Jovanovic, I. Department of Nuclear Engineering and Radiological Sciences University of Michigan Ann ArborMI48109 United States Gerard Mourou Center for Ultrafast Optical Science University of Michigan Ann ArborMI48109 United States Nuclear Engineering Program University of Florida GainesvilleFL32611 United States

We report the spectral signatures induced by ultrafast laser excitation of Xe. There is no significant difference in the number of observable Xe transitions regardless of the focusing condition, suggesting the possibi... 详细信息

ISBN: (纸本)9781957171258

关键词： Remote sensing

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Integrating XR Technologies to Teach the Socially Engaged Design of nuclear Energy Systems

Integrating XR Technologies to Teach the Socially Engaged De...

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2023 Transactions of the American nuclear Society Winter Conference and Expo, ANS 2023

作者： Verma, Aditi Snyder, Katie Nuclear Engineering and Radiological Sciences 2355 Bonisteel Boulevard Ann ArborMI48109 United States Program in Technical Communication 2609 Draper Drive Ann ArborMI48109 United States

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A hybrid few-group homogenization approach for coupled nodal diffusion-thermal hydraulic analysis of nuclear thermal propulsion reactors

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Annals of nuclear Energy 2025年 222卷

作者： Smith, Jacob D. Kotlyar, Dan Nuclear and Radiological Engineering and Medical Physics Program George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA30332-0405 United States

Multiphysics coupled analysis for nuclear Thermal Propulsion (NTP) systems are important for producing accurate core safety margins as the operation dependent thermal–hydraulic (T/H) parameters vary drastically across the core. Through the range of coupled physics model's fidelities, neutronics solutions for NTP reactors are primarily found using Monte Carlo (MC) transport solvers, which produce accurate results at the cost of high computational expense. The motivation for this research is to avoid the computational bottleneck of obtaining high-fidelity, neutronics solutions at every iteration by replacing the MC code with a reduced-order nodal diffusion code. Nodal diffusion analysis is widely used for Light Water Reactors (LWRs) with a standard method that involves pre-generated group constants for unique fuel types homogenized on the assembly level. A series of publications from the authors has detailed the efforts devoted to conducting steady-state, isothermal neutronics modeling of a NERVA-derived NTP reactor core using the nodal diffusion code, DYN3D, with homogenized two-group constant generated with the MC code Serpent and uniform discontinuity factors (UDFs) found using a Jacobian-Free Newton Krylov method (JFNK). The work presented in this paper is the culmination of these efforts, featuring the first demonstration of the finalized hybrid cross section generation approach and the subsequent use in full core simulations. The hybrid approach uses both full core and infinite lattice MC models to efficiently generate two-group homogenized parameters with unique T/H fields representative of a power ramp-up, interpolating on both cross sections and discontinuity factors as a function of control drum angle, fuel temperature, moderator temperature, and moderator coolant density. The results show that the hybrid approach to pre-generating group constants and correction parameters produces a set of data that can be used to obtain accurate – in comparison to the refe

关键词： Importance sampling

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Insights into Calculating Reference Discontinuity Factors with Serpent Monte Carlo Code

SSRN

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SSRN 2024年

作者： Fridman, Emil Smith, Jacob D. Kotlyar, Dan Dresden Germany Nuclear and Radiological Engineering and Medical Physics Program George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA30332-0405 United States

This study explores the calculation of Reference Discontinuity Factors (RDFs) using Serpent, focusing on the methodology and potential pitfalls. In two-step reactor analyses, consistently generated RDFs are crucial for aligning homogeneous nodal diffusion results with the reference heterogeneous transport solution. However, the Serpent internal diffusion solver, based on the Analytic Function Expansion Nodal (AFEN) method, may not be compatible with other nodal methods such as NEM. Additionally, the solver can suffer from instabilities, particularly in multi-group calculations, leading to erroneous RDFs. Despite these challenges, Serpent can generate the necessary raw data for RDF calculation, which can be accurately processed using external diffusion solvers. Two numerical examples - a 1D fuel-reflector model and a 2D SMR core model - illustrate the effects of consistent and inconsistent RDFs on simulation accuracy. The study underscores the importance of using compatible diffusion solvers and thoroughly assessing RDFs to avoid errors in reactor simulations. © 2024, The Authors. All rights reserved.

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Characterizing a Research Reactor Based Fast Neutron Beam with Organic Scintillators

Characterizing a Research Reactor Based Fast Neutron Beam wi...

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IEEE Symposium on nuclear Science (NSS/MIC)

作者： T. E. Maurer N. D. Stubblefield O. Pakari M. Bisbee L. R. Cao S. Clarke S. A. Pozzi Department of Nuclear Engineering and Radiological Sciences University of Michigan Ann Arbor Michigan United States of America Nuclear Engineering Program Ohio State University Columbus Ohio United States of America

Organic scintillators remain underexplored and underutilized in high radiation field characterization and monitoring experiments, with no recent examples found in literature. nuclear reactor monitoring, nuclear safeguards, and other nonproliferation activities may benefit from the dual particle detection capabilities of organic scintillators. To address this knowledge gap, we recently performed experiments in the fast neutron beam of the Ohio State University Research Reactor (OSURR), a light water moderated 500 kWth materials testing reactor. This work is a new experiment providing new results. We used two types of detectors, namely organic glass scintillators (OGS) and stilbenes, to investigate their performance for pulse shape discrimination (PSD), efficiency, and gamma-ray versus neutron pulse integral distributions. We further compared different detector sizes, specifically a 50.8 mm diameter stilbene, a 25.4 mm diameter OGS, and 6 mm edge stilbene and OGS cubes. We show that the gamma pulse integral distributions show distinct Compton edges that may correspond to gamma-ray emission lines from the reactor, for example H(n,g).

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