Highly stable inverted methylammonium lead tri-iodide perovskite solar cells achieved by surface re-crystallization
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99 GENERAL AND MISCELLANEOUS↗
Engineering topics
Kim, Y.
Publications and source records attributed to Kim, Y..
Hidden structural transition in epitaxial Ca0.5Sr0.5IrO3/SrTiO3 thin film
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99 GENERAL AND MISCELLANEOUS↗
Enhanced direct-drive implosion performance on NIF with wavelength separation
Cross-beam energy transfer (CBET) can significantly affect the energy coupling and symmetry of direct-drive implosions. Here, we report on a series of direct-drive shots with 2.1 mm outer diameter capsules conducted on NIF for diagnostic development and calibration in which the wavelength separation (Δλ) between the inner and outer cone beams was varied. We observe a strong improvement in performance as Δλ is applied, with the nuclear yield increasing by up to a factor of 4×. Other data including the nuclear bang time and implosion symmetry suggest that increasing Δλ suppresses CBET and improves both the energy coupling and drive symmetry. These results provide a strong and important benchmark for CBET models applicable to direct-drive ignition designs.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Solid Cherenkov detector for studying nucleosynthesis in inertial confinement fusion
Measuring gamma rays emitted from nuclear reactions gives insight into their nuclear structure. Notably, there are several nuclear reactions that produce gamma rays at ~1 MeV–3 MeV energies such as T( 4 He, γ) 7 Li, 4 He( 3 He, γ) 7 Be, and 12 C(p, γ) 13 N, which may solve questions lingering about big-bang nucleosynthesis and stellar nucleosynthesis. To observe 1 MeV–3 MeV gamma rays in an inertial confinement fusion system, a new style of the Cherenkov detector was developed using aerogel and fused silica as a Cherenkov medium. Utilizing the OMEGA laser facility, both aerogel and fused silica media were compared with the existing gas-medium Cherenkov detector to validate the concept. Furthermore, gamma ray measurements from high yield inertial confinement fusion implosions (deuterium–tritium and deuterium– 3 He) demonstrated that aerogel and fused silica were viable Cherenkov media, paving the way for a potential optimized detector to make these cross section measurements on OMEGA or the National Ignition Facility.
47 OTHER INSTRUMENTATION↗
Proton form factor ratio μ p G E p / G M p from double spin asymmetry
We report the ratio of the electric and magnetic form factor of the proton, $\mu_p G_E^p/G_M^p$, has been measured for elastic electron-proton scattering with polarized beam and target up to four-momentum transfer squared, $Q^2=5.66$ (GeV/c)$^2$ using the double spin asymmetry for target spin orientation aligned nearly perpendicular to the beam momentum direction. This measurement of $\mu_p G_E^p/G_M^p$ agrees with the $Q^2$ dependence of previous recoil polarization data and reconfirms the discrepancy at high $Q^2$ between the Rosenbluth and the polarization-transfer method with a different measurement technique and systematic uncertainties uncorrelated to those of the recoil-polarization measurements. The form factor ratio at $Q^2$=2.06 (GeV/c)$^2$ has been measured as $\mu_p G_E^p/G_M^p = 0.720 \pm 0.176_{stat} \pm 0.039_{sys}$, which is in agreement with an earlier measurement with the polarized target technique at similar kinematics. The form factor ratio at $Q^2$=5.66 (GeV/c)$^2$ has been determined as $\mu_p G_E^p/G_M^p=0.244\pm0.353_{stat}\pm0.013_{sys}$, which represents the highest $Q^2$ reach with the double spin asymmetry with polarized target to date.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Effective interactions in the s d shell
We perform here a quantitative study of the microscopic effective shell-model interactions in the valence sd shell, obtained from modern nucleon-nucleon potentials, chiral N3LO, JISP16 and Daejeon16, using No-Core Shell-Model wave functions and the Okubo-Lee-Suzuki transformation. We investigate the monopole properties of those interactions in comparison with the phenomenological universal sd-shell interaction, USDB. Theoretical binding energies and low-energy spectra of O isotopes and of selected sd-shell nuclei, are presented. We conclude that there is a noticeable improvement in the quality of the effective interaction when it is derived from the Daejeon16 potential. We show that its proton-neutron centroids are consistent with those from USDB. We then propose monopole modifications of the Daejeon16 centroids in order to provide an adjusted interaction yielding significantly improved agreement with the experiment. A spin-tensor decomposition of two-body effective interactions is applied in order to extract more information on the structure of the centroids and to understand the reason for deficiencies arising from our current theoretical approximations. The concern of the possible role of the three-nucleon forces is addressed.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Description of Continuum Spectrum States of Light Nuclei in the Shell Model
The SS-HORSE method is applied to describe the scattering of nucleons by light nuclei based on calculations within the No-Core Shell Model with JISP16 and Daejeon16 NN interactions. The resonant states in {sup 5}He, {sup 5}Li, and {sup 7}He nuclei have been investigated. The SS-HORSE method generalized to the case of the democratic decay is also applied to study a four-neutron system (tetraneutron). The calculations with JISP16 and Daejeon16 and with chiral NN interactions indicate the existence of a rather narrow low-energy tetraneutron resonance.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Revealing Color Forces with Transverse Polarized Electron Scattering
The Spin Asymmetries of the Nucleon Experiment measured two double spin asymmetries using a polarized proton target and polarized electron beam at two beam energies, 4.7 and 5.9 GeV. A large acceptance open-configuration detector package identified scattered electrons at 40° and covered a wide range in Bjorken $\mathcal{x}$ (0.3< $\mathcal{x}$ <0.8). Proportional to an average color Lorentz force, the twist-3 matrix element, $\tilde{d}$$p\atop{2}$, was extracted from the measured asymmetries at Q 2 values ranging from 2.0 to 6.0 GeV 2 . The data display the opposite sign compared to most quark models, including the lattice QCD result, and an unexpected scale dependence. Moreover, when combined with the neutron data in the same Q 2 range the results suggest a flavor independent average color Lorentz force.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Nucleon- α scattering and resonances in 5 He and 5 Li with JISP16 and Daejeon16 NN interactions
The approach called the single-state harmonic oscillator representation of scattering equations (SS-HORSE) to analyze resonant states is generalized to the case of charged particle scattering by using the analytical properties of partial scattering amplitudes and is applied to the study of resonant states in the 5 Li nucleus and nonresonant s-wave proton-α scattering within the no-core shell model using the JISP16 and Daejeon16 NN interactions.We present also the results of calculations of neutron-α scattering and resonances in the 5 He nucleus with Daejeon16 and compare with results published previously using JISP16.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Characterization of the Mercury pulsed power x-ray source spectrum using multichannel density aerogel Cherenkov detectors
The Aerogel Cherenkov Detector for Cygnus (ACD/C) is a time-dependent, x-ray spectral detector that uses SiO 2 aerogels spanning an index of refraction (n = 1.02–1.07) corresponding to a 1.1–2.3 MeV x-ray energy threshold. The ACD/C was developed for pulsed power x-ray sources like Cygnus located at the Nevada National Site and Mercury located at the Naval Research Laboratory (NRL). Aerogels sit between the measurement capabilities of gas (>2 MeV) and solids such as fused silica (>0.3 MeV). The detector uses an aluminum converter to Compton scatter incoming x-rays and create relativistic electrons, which produce Cherenkov light in an aerogel or a fused silica medium. The ACD/C was fielded at the NRL when Mercury was tuned to produce up to 4.8 MeV endpoint bremsstrahlung. Despite a high radiation and electromagnetic interference background, the ACD/C was able to achieve high signal over noise across five aerogel densities and fused silica, including a signal to noise for a 1.1 MeV aerogel threshold. Previous experiments at Cygnus observed a signal that was comparable to the noise (1×) at the same threshold. The ACD/C observed time-resolved rise and fall times for different energy thresholds of the photon spectrum. Finally, Monte Carlo simulations of the ACD/C’s aerogel response curves were folded with a simulation of Mercury’s photon energy spectrum and agree within the error to the observed result.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Applying Temporal Data Mining (TDM) on the Baseline Data Acquired by the In-Situ Decommissioning (ISD) Sensor Network Test Bed - 18093
Researchers at Savannah River National Laboratory (SRNL) have established an In-Situ Decommissioning (ISD) Sensor Network Test Bed-a unique, small scale, configurable environment - for the assessment of prospective sensors on actual ISD system material at minimal cost. The data collected by the ISD sensors are ideal for applying temporal data mining (TDM) technique since they are time-specific, age-specific, and developmental stage-specific. In this research, TDM algorithms were applied on the baseline data collected by ISD test bed in the recent few years to seek frequency episodes in event stream. The tentative results prove that TDM techniques are effective tools for validating ISD performance. Frequent episodes in the data stream have confirmed the daily cycle of the sensor responses and establish sequences of different types of sensors, which was verified by the experimental setup of ISD Sensor Network Test Bed. The abnormal episodes in the data stream may lead to the early indicators of ISD system failures. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
A 5.8 GHz 1.77mW AFSK-OFDM CMOS Backscatter Transmitter for Low Power Internet of Things Applications
This paper presents an AFSK-OFDM (amplitude frequency shift keying-orthogonal frequency division multiplexing) based backscatter transmitter for Internet-of-Things (IoT) applications. The transmitter uses an array of 4 low-power direct digital frequency synthesizers (DDFSs) and DACs to transmit data using both frequency and amplitude symbols on 4 different OFDM subcarriers. The backscatter modulator is demonstrated within a 5.8 GHz wireless link using an 8-symbol OFDM library at a range of 2.7m and shown to consume 1.77 mW when operated at a symbol rate of 4MS/s (corresponds to 12 Mb/s). The modulator chip occupies 0.45mm² of silicon area.
Chang, M-C. Frank↗
Time-Resolved Measurements of Cygnus X-ray Production Using Aerogel Cherenkov Detector
Aerogel Cherenkov Detector for Cygnus (ACD/C) has been developed to provide time-dependent x-ray spectral information from Cygnus – an intense flash x-ray source operated at the Nevada National Security Site. Time-resolved Cygnus x-ray signals were measured at three energy thresholds: 1.3 MeV (by 197 mg/cc aerogel), 1.1 MeV (by 260 mg/cc aerogel), and 0.3 MeV (by quartz). ACD/C data qualitatively suggest that the high-energy x-ray peak exists on a shorter timescale than the Cygnus voltage or current pulse. A time-dependent, x-ray spectral information can improve the understanding of the physics of dense objects radiography.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Ultrafast current imaging by Bayesian inversion
Spectroscopic measurements of current–voltage curves in scanning probe microscopy is the earliest and one of the most common methods for characterizing local energy-dependent electronic properties, providing insight into superconductive, semiconductor, and memristive behaviors. However, the quasistatic nature of these measurements renders them extremely slow. Here, we demonstrate a fundamentally new approach for dynamic spectroscopic current imaging via full information capture and Bayesian inference. This general-mode I–V method allows three orders of magnitude faster measurement rates than presently possible. The technique is demonstrated by acquiring I–V curves in ferroelectric nanocapacitors, yielding >100,000 I–V curves in <20 min. This allows detection of switching currents in the nanoscale capacitors, as well as determination of the dielectric constant. These experiments show the potential for the use of full information capture and Bayesian inference toward extracting physics from rapid I–V measurements, and can be used for transport measurements in both atomic force and scanning tunneling microscopy.
36 MATERIALS SCIENCE↗
Design and performance of the spin asymmetries of the nucleon experiment
The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1 , A 2 , g 1 , g 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.
43 PARTICLE ACCELERATORS↗