Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session V46: Instrumentation IV |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Chuck Mielke, LANL Room: 311 |
Thursday, March 17, 2016 2:30PM - 2:42PM |
V46.00001: Optimum Noise Reduction Methods for the Interior of Vehicles and Aircraft Cabins Hasson M. Tavossi, Ph.D. The most effective methods of noise reduction in vehicles and Aircraft cabins are investigated. The first goal is to determine the optimal means of noise mitigation without change in external shape of the vehicle, or aircraft cabin exterior such as jet engine or fuselage design, with no significant added weight. The second goal is to arrive at interior designs that can be retrofitted to the existing interiors, to reduce overall noise level for the passengers. The physical phenomena considered are; relaxation oscillations, forced vibrations with non-linear damping and sub-harmonic resonances. The negative and positive damping coefficients and active noise cancelations methods are discussed. From noise power-spectrum for a prototype experimental setup, the most energetic vibration modes are determined, that require the highest damping. The proposed technique will utilize the arrangement of uniformly distributed open Helmholtz resonators, with sound absorbing surface. They are tuned to the frequencies that correspond to the most energetic noise levels. The resonators dissipate noise energy inside the vehicle, or aircraft cabin, at the peak frequencies of the noise spectrum, determined for different vehicle or aircraft cabin, interior design models. [Preview Abstract] |
Thursday, March 17, 2016 2:42PM - 2:54PM |
V46.00002: A Noninvasive In Vivo Glucose Sensor Based on Mid-Infrared Quantum Cascade Laser Spectroscopy Alexandra Werth, Sabbir Liakat, Laura Xu, Claire Gmachl Diabetes affects over 387 million people worldwide; a number which grows every year. The most common method of measuring blood glucose concentration involves a finger prick which for some can be a harrowing process. Therefore, a portable, accurate, noninvasive glucose sensor can significantly improve the quality of life for many of these diabetics who draw blood multiple times a day to monitor their glucose levels. We have implemented a noninvasive, mobile glucose sensor using a mid-infrared (MIR) quantum cascade laser (QCL), integrating sphere, and thermal electrically (TE) cooled detector. The QCL is scanned from 8 - 10 microns wavelength over which are distinct absorption features of glucose molecules with little competition of absorption from other molecules found in the blood and interstitial fluid. The obtained absorption spectra are analyzed using a neural network algorithm which relates the small changes in absorption to the changing glucose concentration. The integrating sphere has increased the signal-to-noise ratio from a previous design, allowing us to use the TE-cooled detector which increases mobility without loss of accuracy. [Preview Abstract] |
Thursday, March 17, 2016 2:54PM - 3:06PM |
V46.00003: Temperature Coefficient of Secondary Electron Emission: A Novel Thermal Metrology Md. Imran Khan, Sean Daniel Lubner, David Frank Ogletree, Ed Wong, Chris Dames State of the art nanoscale temperature mapping techniques include Scanning Thermal Microscopy (SThM) and optical thermoreflectance, though these have the challenges of requiring sample contact and being diffraction limited, respectively. Near field scanning optical microscopy (NSOM) can beat the diffraction limit but still cannot measure temperature at 10s of nanometer resolution. SEM is well known for topographic imaging but has not been previously used for thermal mapping. Past literature suggested that secondary electron yields might have a small temperature dependence due to electron-phonon scattering and/or temperature dependence of work function. We previously measured the temperature coefficient of secondary electron emission of several group IV and III-V semiconductors and found it to range from around 100 to 1000 ppm/K. Here, we utilize this to map a spatial temperature gradient in an SEM image. We implement a double-heater structure to produce a temperature gradient along the plane of a substrate. The primary electron beam is scanned across the sample's surface while the emitted (secondary plus backscattered) electron current and net absorbed sample currents are simultaneously recorded. The results demonstrate the ability to map a spatial temperature gradient. [Preview Abstract] |
Thursday, March 17, 2016 3:06PM - 3:18PM |
V46.00004: Tomographic Reconstruction of Circularly Polarized High Harmonic Fields: 3D Attosecond Metrology Cong Chen, Zhensheng Tao, Carlos Hernández-García, Piotr Matyba, Adra Carr, Ronny Knut, Ofer Kfir, Dimitry Zusin, Christian Gentry, Patrick Grychtol, Oren Cohen, Lius Plaja, Andreas Becker, Agnieszka Jaron-Becker, Henry Kapteyn, Margaret Murnane Bright, circularly polarized, extreme ultraviolet (EUV) and soft X-ray high harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. In the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency and polarization. Here, we extend attosecond metrology techniques to circularly polarized light for the first time by simultaneously irradiating a copper surface with circularly polarized high harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date. [Preview Abstract] |
Thursday, March 17, 2016 3:18PM - 3:30PM |
V46.00005: Enhancement of photocurrent on few-layered $p$-WSe$_{\mathrm{2}}$ FET by multi-terminal measurement Carlos Garcia, Nihar Pradhan, Joshua Holleman, Daniel Rhodes, Luis Balicas, Stephen McGill Recently, two dimensional materials particularly transition metal dichalcogenides (TMDs) have been extensively studied because of their strong light-matter interactions and extraordinary electrical and optical properties in field-effect transistors (FETs). We investigated the photocurrent response on few-layered $p$-WSe$_{\mathrm{2}}$ and MoSe$_{\mathrm{2}}$ FETs in a multi-terminal configuration using a 532 nm laser. Photogenerated current $I_{\mathrm{ph}}$ ($=I_{\mathrm{light}}$-$I_{\mathrm{dark}})$ was measured as a function of optical power incident on the sample with varying source-drain bias, $V_{\mathrm{ds}}$, and back gate voltage, $V_{\mathrm{bg}}$. We observed a large enhancement of photocurrent in a four-terminal configuration compared to a two-terminal configuration. The measured two-terminal photoresponsivity ($R)$ and external quantum efficiency (\textit{EQE}) from our \textasciitilde 10 layers $p$-WSe$_{\mathrm{2}}$ at applied $V_{\mathrm{ds}}=$1V and $V_{\mathrm{bg}}=$10V were \textasciitilde 18A/W and \textasciitilde 4000{\%}, respectively. The $R$ and \textit{EQE} values increased to \textasciitilde 85 A/W and \textasciitilde 20000{\%} respectively using a four-terminal configuration. Thus by using a multi-terminal configuration, one can observe an enhanced photocurrent response on few-layered TMDs for potential applications in photo-detection and optoelectronic circuits. [Preview Abstract] |
Thursday, March 17, 2016 3:30PM - 3:42PM |
V46.00006: Cavities for electron spin resonance: predicting the resonant frequency John Colton, Kyle Miller, Michael Meehan, Ross Spencer Microwave cavities are used in electron spin resonance to enhance magnetic fields. Dielectric resonators (DRs), pieces of high dielectric material, can be used to tailor the resonant frequency of a cavity. However, designing cavities with DRs to obtain desired frequencies is challenging and in general can only be done numerically with expensive software packages. We present a new method for calculating the resonant frequencies and corresponding field modes for cylindrically symmetric cavities and apply it to a cavity with vertically stacked DRs. The modes of an arbitrary cavity are expressed as an expansion of empty cavity modes. The wave equation for D gives rise to an eigenvalue equation whose eigenvalues are the resonant frequencies and whose eigenvectors yield the electric and magnetic fields of the mode. A test against theory for an infinitely long dielectric cylinder inside an infinite cavity yields an accuracy better than 0.4\% for nearly all modes. Calculated resonant frequencies are also compared against experiment for quasi-TE011 modes in resonant cavities with ten different configurations of DRs; experimental results agree with predicted values with an accuracy better than 1.0\%. MATLAB code is provided at http://www.physics.byu.edu/research/coltonlab/cavityresonance. [Preview Abstract] |
Thursday, March 17, 2016 3:42PM - 3:54PM |
V46.00007: High magnetic field calibration using de Haas-van Alphen oscillations in polycrystalline copper William A. Coniglio, Alan F. Williams, Anna Yannakopoulos, Audrey Grockowiak, Stan Tozer We provide a calibration for the de Haas-van Alphen (dHvA) frequency in polycrystalline copper, which may be used to standardize the measurement of magnetic fields, particularly in pulsed field environments, where direct observation of NMR is challenging. Using a reliable single-crystal model of the Fermi surface from coefficients that are traceable to a powder Al NMR reference, we computed Fermi surface extremal areas for evenly spaced directions around a sphere. Summing the peaks corresponding to extremal orbits according to the Lifshitz-Kosevich model, we arrive at a dHvA spectrum that corresponds to experimental observation. We find that actual maximum fields reached at the NHMFL-Pulsed Field Facility are slightly larger than previously determined. [Preview Abstract] |
Thursday, March 17, 2016 3:54PM - 4:06PM |
V46.00008: NANONIS TRAMEA -- A Quantum Transport Measurement System Thorsten Kampen, Andreas Thissen, Oliver Schaff, Alessandro Pioda Nanonis Tramea is a quantum leap with respect to increased speed for transport measurements taking research onto a new level. Measurements which took several hours in the past can now be done in minutes without compromising signal quality. Tramea uses its fast, high-resolution, high-precision and ultra-low-noise outputs and inputs to generate and acquire up to 20000 data points per second on 24 channels in parallel. This is not only up to 1000 x faster than typical measurement systems but it is also time deterministic with highest precision. Here, the time separation between points is constant so that artefacts caused by unequal point spacings in non-deterministic measurement systems are avoided. The emphasis here is the real-time relation. Tramea comes with a built-in interface which allows for control of the instruments' basic functions from any programming environment. For users requiring more functionality and higher speeds a full-featured LabVIEW-based programming interface or scripting module are available as add-on modules. Due to the modularity and flexibility of the hardware and software architecture of Tramea upgrades with standardized add-on modules are possible. Non-standard requests can still be handled by the various programming options. [Preview Abstract] |
Thursday, March 17, 2016 4:06PM - 4:18PM |
V46.00009: Construction and $^{13}$C NMR signal-amplification efficiency of a dynamic nuclear polarizer at 6.4 T and 1.4 K Andhika Kiswandhi, Peter Niedbalski, Christopher Parish, Sarah Ferguson, David Taylor, George McDonald, Lloyd Lumata Dissolution dynamic nuclear polarization (DNP) is a rapidly emerging technique in biomedical and metabolic imaging since it amplifies the liquid-state nuclear magnetic resonance (NMR) and imaging (MRI) signals by $>$10,000-fold. Originally used in nuclear scattering experiments, DNP works by creating a non-Boltzmann nuclear spin distribution by transferring the high electron ($\gamma$ = 28,000 MHz/T) thermal polarization to the nuclear spins via microwave irradiation of the sample at high magnetic field and low temperature. A dissolution device is used to rapidly dissolve the frozen sample and consequently produces an injectable “hyperpolarized” liquid at physiologically-tolerable temperature. Here we report the construction and performance evaluation of a dissolution DNP hyperpolarizer at 6.4 T and 1.4 K using a continuous-flow cryostat. The solid and liquid-state $^{13}$C NMR signal enhancement levels of $^{13}$C acetate samples doped with trityl OX063 and 4-oxo-TEMPO free radicals will be discussed and compared with the results from the 3.35 T commercial hyperpolarizer. [Preview Abstract] |
Thursday, March 17, 2016 4:18PM - 4:30PM |
V46.00010: Comparative Analysis of two Methods for High-Resolution Differential Conductance Measurement David Cusick, Michio Naito, Roberto Ramos We compare two methods of differential conductance measurement. The first is a traditional method in which current and voltage data is acquired via four-wire measurement, then averaged and differentiated numerically. The second method calculates $dI/dV$ in real time by superimposing a small DC signal $dI$ on the input step function, alternating between addition and subtraction of the signal with each step, then averaging the small signal voltage response over three steps to obtain $dV$. This requires two instruments: a DC current source and a high-resolution voltmeter. Keithley Instruments has commercially promoted the Keithley 622x current source and 2182A nanovoltmeter as means to achieve this measurement; we therefore refer to it as the Keithley method. We compare the two methods by performing high-resolution measurements of the energy gap of MgB$_{2}$ thin film Josephson junctions. We show that the Keithley method has advantages of cleaner data, easier implementation, and overall faster data collection, but may lack the traditional method's high resolution. [Preview Abstract] |
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