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At least 1,549 records · Page 86

In-situ High-energy X-ray Diffraction Study of the Local Structure of Supercooled Liquid Si

While changes in the coordination number for liquid silicon upon supercooling, signaling an underlying liquid-liquid phase transition, have been predicted, x-ray and neutron measurements have produced conflicting reports. In particular some studies have found an increase in the first shell coordination as temperature decreases in the supercooled regime, while others have reported increases in the coordination number with decreasing temperature. Employing the technique of electrostatic levitation coupled with high energy x-ray diffraction (125 keV), and rapid data acquisition (100ms collection times) using an area detector, we have obtained high quality structural data more deeply into the supercooled regime than has been possible before. No change in coordination number is observed in this temperature region, calling into question previous experimental claims of structural evidence for the existence of a liquid-liquid phase transition.

Lee, G. W.↗

Advanced methods for preparation and characterization of infrared detector materials

Crystal growth of Hg sub 1-x Cd sub x Te and density measurements of ingot slices are discussed. Radial compositional variations are evaluated from the results of infrared transmission edge mapping. The pseudo-binary HgTe-CdTe phase diagram is examined with reference to differential thermal analysis measurements. The phase equilibria calculations, based on the 'regular association solution' theory (R.A.S.) are explained and, using the obtained R.A.S. parameters, the activities of Hg, Cd, and Te vapors and their partial pressures over the pseudo-binary melt are calculated.

Lehoczy, S. L.↗

Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-{sup 3}He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Probing the top-Higgs Yukawa CP structure in dileptonic t t &#x00AF;<!-- ¯ --> h with M 2 -assisted reconstruction

Constraining the Higgs boson properties is a cornerstone of the LHC program. We study the potential to directly probe the Higgs-top CP-structure via the t t &#x00AF;<!-- ¯ --> h channel at the LHC with the Higgs boson decaying to a bottom pair and top-quarks in the dileptonic mode. We show that a combination of laboratory and t t &#x00AF;<!-- ¯ --> rest frame observables display large CP-sensitivity, exploring the spin correlations in the top decays. To efficiently reconstruct our final state, we present a method based on simple mass minimization and prove its robustness to shower, hadronization and detector effects. In addition, the mass reconstruction works as an extra relevant handle for background suppression. Based on our results, we demonstrate that the Higgs-top CP-phase (α) can be probed up to cos α < 0.7 at the high luminosity LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Recent Results and Methods on Higher Order and Off-diagonal Cumulants of Identified Net particle Multiplicity Distributions in Au+Au Collisions at STAR

We present recent results on the cumulants of net-particle distributions in Au+Au collisions at the STAR experiment. Beam energy dependence of net-Delta cumulants and off-diagonal cumulants are measured. These measurements provide additional constraints on the chemical freeze-out conditions. The sixth-order cumulant of net-charge and net-proton distributions is measured at psNN =200 GeV to search for the signal of the crossover phase transition. Finally, an unfolding technique is developed and applied to the net-proton distributions at 19.6 GeV to account for the non-binomial effects of the detector.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Recent constraints on axion-photon and axion-electron coupling with the CAST experiment

The CERN Axion Solar Telescope (CAST) is a helioscope looking for axions arising from the solar core plasma and arriving to Earth. The experiment, located in Geneva (Switzerland) is able to follow the Sun during sunrise and sunset. Four x-ray detectors mounted on both ends of the magnet wait for photons from axion-to-photon conversion due to the Primakoff effect. Up to date, with the completion of Phases I and II, CAST has been looking for axions that could be produced in the Sun by both, hadronic and non-hadronic mechanisms.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Quantum-limit phenomena and band structure in the magnetic topological semimetal EuZn 2 As 2

The interplay between magnetism and electronic topology in the quantum limit is a forefront subject of condensed matter physics. Here, we show the electronic and magnetic properties of layered antiferromagnet EuZn 2 As 2 in pulsed magnetic fields up to 60 T and temperatures down to 0.6 K. By analyzing the quantum oscillations observed in the magnetoresistance (MR) and proximity detector oscillator (PDO) frequency, we find that (1) the oscillation frequency F = 46 ± 6 T for H // c and 42 ± 2 T for H // ab; (2) the corresponding Berry phase is close to π for H // c, implying a nontrivial topology; and (3) the large linear MR occurs beyond the first Landau level, without any sign of saturation. From these observations, we conclude that the linear MR can be understood by considering diffusing cyclotron centers due to compressed Landau wavefunction, an emergent behavior in the quantum limit.

36 MATERIALS SCIENCE↗

Search for Violation of CPT and Lorentz Invariance in $B^0_s$ Meson Oscillations using the D0 Detector

A search is presented for CPT-violating effects in the mixing of $B^0_s$ mesons using the D0 detector at the Fermilab Tevatron Collider. The CPT-violating asymmetry in the decay $B^0_s \rightarrow \mu^{\pm} D_s^{\mp} X$ as a function of sidereal phase is measured. No evidence for CPT-violating effects is observed and limits are placed on CPT- and Lorentz-invariance violating coupling coefficients.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

White Beam Normalization

Raw data used to normalize detector performance on the ARCS instrument For the run cycle starting in June 2023. This is a V cylinder and the T0 chopper is set to 150 Hz and phased for 300 meV. All Fermi Choppers are out of the Beam.

MATERIALS SCIENCE↗

CHIRP-Like Signals: Estimation, Detection and Processing A Sequential Model-Based Approach

Chirp signals have evolved primarily from radar/sonar signal processing applications specifically attempting to estimate the location of a target in surveillance/tracking volume. The chirp, which is essentially a sinusoidal signal whose phase changes instantaneously at each time sample, has an interesting property in that its correlation approximates an impulse function. It is well-known that a matched-filter detector in radar/sonar estimates the target range by cross-correlating a replicant of the transmitted chirp with the measurement data reflected from the target back to the radar/sonar receiver yielding a maximum peak corresponding to the echo time and therefore enabling the desired range estimate. In this application, we perform the same operation as a radar or sonar system, that is, we transmit a “chirp-like pulse” into the target medium and attempt to first detect its presence and second estimate its location or range. Our problem is complicated by the presence of disturbance signals from surrounding broadcast stations as well as extraneous sources of interference in our frequency bands and of course the ever present random noise from instrumentation. First, we discuss the chirp signal itself and illustrate its inherent properties and then develop a model-based processing scheme enabling both the detection and estimation of the signal from noisy measurement data.

42 ENGINEERING↗

Status of ICARUS NUMI Interaction Cross-Section Analysis

The ICARUS experiment, utilizing Liquid Argon Time Projection Chamber (LAr TPC) technology, has been installed at Fermilab in Chicago, Illinois, following its initial operation in Italy and subsequent refurbishment at CERN. ICARUS completed commissioning in June 2022. Currently, the experiment is in the phase of analyzing data from its two runs of physics data acquisition and gearing up for the third run. While its primary objective is to function as the far detector of the Short Baseline Neutrino program (SBN), seeking sterile neutrino signatures, ICARUS also offers diverse physics capabilities, including searches beyond the standard model and measurements of cross-sections. In addition to being exposed to the common Booster Neutrino (BNB) beamline, ICARUS also receives off-axis neutrinos from the Main Injector (NuMI) beam. Due to the off-axis angle between NuMI and ICARUS, coupled with contributions from both pion and kaon decays to neutrino fluxes, interactions of NuMI neutrinos within ICARUS can be detected over a range of several GeV in energy. These interactions present opportunities for crucial cross-section measurements and model tests within an energy range that overlaps both the SBN oscillation search and a portion of the DUNE spectrum. This poster presentation will delve into our efforts to conduct a muon-neutrino cross-section measurement, where the signal is defined by events with no pions produced in the final state of the interaction, along with some preliminary muon-neutrino inclusive measurements. Additionally, it will provide updates on the current status and future plans, including reconstruction, selection, and analysis procedures.

43 PARTICLE ACCELERATORS↗

Bayesian Fit for the NOvA Three Flavor Oscillation Analysis

NOvA is a long baseline neutrino oscillation experiment, using Fermilab's NuMI beam and a functionally identical near and far detector. NOvA measures muon neutrino disappearance and electron neutrino appearance to probe neutrino oscillation parameters, including the large neutrino mixing angle, the mass ordering, and the CP-violating phase. NOvA has developed a Bayesian analysis in addition to its Frequentist analysis, using Markov Chain Monte Carlo. This Bayesian framework allows for measurements previously difficult to make with the Frequentist framework, such as the Jarlskog invariant and the reactor mixing angle. The details and status of the Bayesian Framework will be presented, as well as latest NOvA results on measurements of three-flavor oscillation parameters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Radial diffusion of Io-injected plasma

The paper reexamines the problem of particle injection by Io and subsequent radial diffusion by flux tube interchange using a proper phase space density formulation. The mathematical formalism is developed, and the theoretical results are compared with the observations, taking into account the pitch angle and energy coverage of the detector on Pioneer 10. Two objectives are pursued: (1) to test the hypothesis of Siscoe and Chen (1977) that Io is the source for all of the plasma observed by Frank et al. (1976) inside 10 R(J); and (2) to describe a simple but flexible method intended to analyze the observations of any other plasma instrument flown through the inner Jovian magnetosphere, e.g., those on Voyager 1 and 2 and Galileo.

Goertz, C. K.↗

Capsulation Satellite or CapSat: A Low-Cost, Reliable, Rapid-Response Spacecraft Platform

The National Aeronautics and Space Administration (NASA) Goddard's Rideshare Office estimates that between 2013 and 2022, NASA launches of primary satellites will have left unused more than 20,371 kilograms of excess capacity. This equates to hundreds of millions of dollars in launch-vehicle costs going unutilized. To fill this void with a standard CubeSat or SmallSat spacecraft platform, which when required to be more reliable, still will cost in the neighborhood of $1M a kilogram, making it prohibitively expensive. A newly proposed solution, which NASA is pursuing, is called the Capsulation Satellite or CapSat. CapSat is a modularized, pressurized, thermally controlled spacecraft designed to host ruggedized commercially available instrumentation in a terrestrial like environment on orbit. Using a technique that is under review for a patent, CapSat actively manages internal air temperatures in a manner similar to a household thermostat. This gives CapSat high-thermal stability, which, in turn, provides component longevity. CapSat was specifically designed to take advantage of the United States Air Force (USAF) Rideshare Program and the Evolved Expendable Launch Vehicle Secondary Payload Adaptor, or ESPA ring. The ESPA ring comes in two sizes: standard and Grande. CapSat primarily will take advantage of the ESPA Grande to provide a 300-kilogram payload capability per attachment point, with up to four attachment points per ring. This approach combines a high-mass capability with a proven Rideshare mechanical interface and secondary payload management infrastructure. Opportunities for ESPA based co-manifests are continuing to expand. The CapSat program is currently funded to design and build a limited prototype and perform thermal-vacuum testing. CapSat is currently in the concept/study phase for both single missions and constellation of earth- and space-observing missions. One of these studies includes land imaging using state-of-the-art advanced infrared detector technology. This paper will report on the current status of the CapSat hardware design, testing, and results as well as any openly available advanced concept study results. The CapSat solution is intended to be a game-changing paradigm shift. CapSat will repurpose currently available, already-proven technology to reduce spaceflight hardware costs to less than $50,000 per kilogram.

Burt, Joe↗

Scannerless laser range imaging using loss modulation

A scannerless 3-D imaging apparatus is disclosed which utilizes an amplitude modulated cw light source to illuminate a field of view containing a target of interest. Backscattered light from the target is passed through one or more loss modulators which are modulated at the same frequency as the light source, but with a phase delay .delta. which can be fixed or variable. The backscattered light is demodulated by the loss modulator and detected with a CCD, CMOS or focal plane array (FPA) detector to construct a 3-D image of the target. The scannerless 3-D imaging apparatus, which can operate in the eye-safe wavelength region 1.4-1.7 .mu.m and which can be constructed as a flash LADAR, has applications for vehicle collision avoidance, autonomous rendezvous and docking, robotic vision, industrial inspection and measurement, 3-D cameras, and facial recognition.

47 OTHER INSTRUMENTATION↗

The Barrel Calorimeter for the GlueX Experiment at Jefferson Lab

The GlueX experiment at Jefferson Lab will search for exotic hybrid mesons as evidence of gluonic excitations, in an effort to understand confinement in QCD. The key features of this compelling physics program will be presented together with an overview of the detector, focusing on the electromagnetic barrel calorimeter (BCAL). The BCAL is a 'spaghetti calorimeter,' consisting of layers of corrugated lead sheets, interleaved with planes of 1-mm-diameter, double-clad, scintillating fibres, bonded in the lead grooves using optical epoxy. This detector will consist of 48 modules and will be readout using 3,840 large-area Multi-Photon Pixel counter arrays. The experiment is now in the installation phase with data taking expected in 2015.

Papandreou, Zisis↗

First measurement of the CP -violating phase $ {\phi}_s^{d\overline{d}} $ in B s o → (K + π – )(K – π + ) decays

A flavour-tagged decay-time-dependent amplitude analysis of B s o → (K + π – )(K – π + ) decays is presented in the K ± π ∓ mass range from 750 to 1600MeV/c 2 . The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb –1 . Several quasi-two-body decay modes are considered, corresponding to K ± π ∓ combinations with spin 0, 1 and 2, which are dominated by the K o * (800)0 and K o * (1430) o , the K*(892) o and the K 2 * (1430) o resonances, respectively. The longitudinal polarisation fraction for the B 0 s → K*(892)°K¯*(892) 0 decay is measured as f L = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP -violating phase, $ {\phi}_s^{d\overline{d}} $, in b → dd¯s transitions is performed, yielding a value of $ {\phi}_s^{d\overline{d}} $ = –0.10 ± 0.13 (stat) ± 0.14 (syst) rad.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗