Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P36: Instrumentation and Measurements II |
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Sponsoring Units: GIMS Room: 299 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P36.00001: High-Power Terahertz Photoconductive Antenna with Schottky and Ohmic Contact Electrodes Christopher Kim, Dong Ho Wu, Benjamin Graber Time domain terahertz (THz) spectroscopy (TDTS) has been widely adopted for many applications in science and industry, such as chemical and materials analysis and detection of hazardous materials. TDTS systems regularly use a photoconductive antenna fabricated on a GaAs substrate as the THz source, as it can generate a wideband THz pulse very efficiently. Increasing the coherent THz beam power is essential for high signal-to-noise spectroscopy. However, conventional photoconductive antennas only generate 10 nW- 100 \textmu W. Our experiments show that the power and stability of the coherent THz beam emitted from a photoconductive antenna can be influenced by the qualities of the electrodes' metal-to-semiconductor contact. Therefore, we investigated THz emission from photoconductive antennas fabricated with Schottky and Ohmic contact electrodes. Using a TDTS system, we characterized the THz output for each electrode contact variation and found that Schottky contacts could produce much stronger THz beams, while Ohmic contact electrodes were more prone to damage. Using these contact optimizations, along with other antenna optimizations, we have demonstrated a photoconductive antenna capable up to 3 mW of THz power. [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P36.00002: Development of force-detected THz-ESR measurement system and its application to metal porphyrin complexes Hideyuki Takahashi, Tsubasa Okamoto, Eiji Ohmichi, Hitoshi Ohta Electron spin resonance spectroscopy in the terahertz region (THz-ESR) is a promising technique to study biological materials such as metalloproteins because it directly probes the metal ion sites that play an important role in the emergence of functionality [1]. By combining THz-ESR with force detection, the samples mass is reduced to the order of ng. This feature is of great advantage because the sample preparation process of biological materials is time-consuming. We developed a force-detected THz-ESR system utilizing optical interferometry for precise cantilever displacement measurement. In order to suppress the sensitivity fluctuation and instability of cantilever dynamics under high magnetic field, the tuning of interferometer is feedback-controlled during a measurement[2]. By using this system, we successfully observed the ESR signal of hemin, which is a model substance of hemoglobin and myoglobin, in THz region.\\ $\left[ 1 \right]$ H. Takahashi, E. Ohmichi and H. Ohta, Appl. Phys. Lett. {\bfseries 107}, 182405 (2015).\\ $\left[ 2 \right]$ H. Takahashi, T. Okamoto, E. Ohmichi and H. Ohta, Appl. Phys. Express {\bfseries 9}, 126701 (2016). [Preview Abstract] |
Wednesday, March 15, 2017 2:54PM - 3:06PM |
P36.00003: Coherence and Dynamics of a High-$\beta $ Metallo-dielectric Nanolasers Si Hui Athena Pan Metal-clad nanolasers with high spontaneous emission factors ($\beta )$ represent a class of ultra-compact light emitters with applications in fiber-optic communications, optical computing, imaging and sensing. In-depth studies on both the coherence and dynamical properties of these emitters are necessary before practical applications can be realized. However, the coherence characterization of a high-$\beta $ nanolaser using the conventional measurement of output versus input intensity (L-L curve) is inherently difficult. We conducted the second order intensity correlation measurement, or g$^{2}(\tau )$ --- a more definitive method to confirm coherence --- on a high-$\beta $ metallo-dielectric nanolaser. Our result indicates that full coherence is achieved at three times the threshold conventionally defined by the kink in the L-L curve. Additionally, we observed that the g$^{2}(\tau )$ peak width shrinks below and broadens above threshold. Rate-equation analyses reveal that the above-threshold broadening is due to dynamical hysteresis. We propose that this dynamical phenomenon can be exploited to determine the lasing regimes of a unity-$\beta $ nanolaser, whose threshold is inherently ambiguous and difficult to observe. [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P36.00004: Xi-cam: Flexible High Throughput Data Processing for GISAXS Ronald Pandolfi, Dinesh Kumar, Singanallur Venkatakrishnan, Abinav Sarje, Hari Krishnan, Lenson Pellouchoud, Fang Ren, Amanda Fournier, Zhang Jiang, Christopher Tassone, Apurva Mehta, James Sethian, Alexander Hexemer With increasing capabilities and data demand for GISAXS beamlines, supporting software is under development to handle larger data rates, volumes, and processing needs. We aim to provide a flexible and extensible approach to GISAXS data treatment as a solution to these rising needs. Xi-cam is the CAMERA platform for data management, analysis, and visualization. The core of Xi-cam is an extensible plugin-based GUI platform which provides users an interactive interface to processing algorithms. Plugins are available for SAXS/GISAXS data and data series visualization, as well as forward modeling and simulation through HipGISAXS. With Xi-cam’s ‘advanced’ mode, data processing steps are designed as a graph-based workflow, which can be executed locally or remotely. Remote execution utilizes HPC or de-localized resources, allowing for effective reduction of high-throughput data. Xi-cam is open-source and cross-platform. The processing algorithms in Xi-cam include parallel cpu and gpu processing optimizations, also taking advantage of external processing packages such as pyFAI. Xi-cam is available for download online. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P36.00005: Abstract Withdrawn
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Wednesday, March 15, 2017 3:30PM - 3:42PM |
P36.00006: New muon source possibilities at the Spallation Neutron Source G. J. MacDougall, T. J. Williams In September, 2016, a workshop was held at Oak Ridge National Laboratories (ORNL) to discuss possibilities for the construction of a dedicated $\mu$SR facility at the Spallation Neutron Source (SNS) to complement the existing neutron scattering program. The meeting was motivated by ongoing design activities for the Second Target Station at the SNS and several reports in recent years showing strong support for a muon source in the United States. Attendees included representatives from all existing $\mu$SR facilities, members of the university-based research community, and experts at ORNL familiar with local accelerator and source designs. In this talk, I will summarize main conclusions from that meeting, which includes consideration of a number of potential muon target positions in the existing or planned accelerator facilities at the SNS. Of particular interest is one source design that uses existing laser stripping technologies to direct a short, tunable proton pulse from the linear accelerator toward a dedicated target. This design is capable of creating a pulsed beam of muons with ideal and variable timing resolution and an intensity many times what is available at the current generation of $\mu$SR facilities. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P36.00007: In-Situ Additive Manufacturing Platform for Neutron, X-ray and Proton Beamlines Jason C. Cooley, Donald B. Brown, John S. Carpenter, Bjorn Clausen, Carl E. Cross, Thomas J. Lienert, John E. Bernal, Adrian S. Losko Advanced manufacturing offers the promise to make high value components with complex shapes without complex machining or significant material waste on short notice. There are however significant technical barriers to overcome with focused research and development. In the case of metallic parts made by melting and depositing wire or powder, additive manufacturing results in repetitive heating and cooling of the deposited material. The thermal gradients imposed are significantly higher than typically encountered during casting. These gradients produce residual stresses we cannot currently predict and can cause the formation of undesirable secondary phases. Efforts to accurately predict the final state of materials manufactured additively will require an understanding of the time evolution of the microstructure which includes intertwined residual stresses, texture, and chemical inhomogeneity. The best way to understand these linked effects is to measure their evolution in-situ during the deposition process. In order to do this a prototype device for making quasi 1-D features while making real time beamline measurements (radiography and diffraction) has been built and recently tested. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P36.00008: Photothermal microfluidic cantilever deflection spectroscopy reflecting clustering mechanism of ethanol water mixtures Maryam Ghoraishi, John Hawk, Thomas Thundat Aqueous mixture of alcohol is a typical prototype for biomolecules, micelle formation, and structural stability of proteins. Therefore, Short chain alcohols such as EtOH have been used as a simple model for understanding of more complex aqueous biomolecules. Here we study vibrational energy peaks of EtOH water binary mixtures using micromechanical calorimetric spectroscopy using bimaterial microfluidic cantilevers (BMC). The IR spectra of EtOH-water are experimentally collected employing a BMC as concentration of EtOH changes from 20--100 wt{\%}. As concentration of EtOH varies in the mixture, considerable shifts in the wavenumber at IR absorption peak maxima are reported. The experimentally measured shifts in the wavenumber at IR absorption peak maxima are related to changes in dipole moment ($\mu )$ of EtOH at different concentration. The relationship between IR absorption wavenumber for both anti and gauche conformers of EtOH, and inverse dipole moment, 1/$\mu $, of EtOH at different concentrations follows a power law dependence. Our technique offers a platform to investigate dipole effect on molecular vibrations of mixtures in confined picoliter volumes, previously unexplored with other analytical techniques due to limitations of volume under study. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P36.00009: Thermal conductivity of actinide materials measured using the 3$\omega $ method Keshav Shrestha, Krzysztof Gofryk The thermal conductivity of nuclear materials governs the conversion of heat produced from fission events into electricity and it is an important parameter in reactor design and safety.~However, it is also a challenging property to measure due to radioactivity and radiotixicity of actinides. Most of the conventional methods require usage of large samples (millimeter size at least) with an appropriate shape. The 3$\omega $-method, developed by Cahill [D. G. Cahill,~\textit{Review of Scientific Instruments},~61, 802 (1990)], is designed to work with small samples and enables to measure thermal conductivity and heat capacity of bulk and thin layered materials. In this work, we have adapted the 3$\omega $~method to measure thermal conductivity and heat capacity of various metallic and insulating samples including small single crystals of UO$_{\mathrm{2}}$~and UN. The validity of this method has been also tested by measuring thermal conductivities of several testing materials (Cu, Pt, Constantan, SiO$_{\mathrm{2}})$. The new measurement setup has been adapted to be compatible with Quantum Design PPMS system. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P36.00010: Johnson noise measurements of a 3.1 k$\Omega$ resistor at mK temperatures using a SQUID-based circuit Vidhi Shingla, Ethan Kleinbaum, G\'abor Cs\'athy The measurement of Johnson noise of resistors of the order of a k$\Omega$ at mK temperatures is a difficult task. Such a measurement is not possible with room temperature amplifiers since the typical amplifier noise exceeds the Johnson noise. Such measurements are, however, possible with circuits based on cooled High Electron Mobility Transistors (HEMTs). We present an alternative circuit for such measurements which is based on a dc SQUID. We demonstrate that our circuit does not contribute appreciable noise to the Johnson noise of a $3.1$ k$\Omega$ resistor down to 16 mK, enabling therefore Johnson noise thermometry. [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P36.00011: Single-charge pump based on a silicon quantum dot Tuomo Tanttu, Alessandro Rossi, Kuan Yen Tan, Kukka-Emilia Huhtinen, Akseli M\"akinen, Kok Wai Chan, Mikko M\"ott\"onen, Andrew S. Dzurak Semiconductor nanoscale single-electron pumps can precisely transport precisely an integer number of electrons at a fixed frequency resulting in a quantized current. The most appealing application for such pumps is the realization of the emerging definition of the SI ampere based on a fixed value of the electron charge. We perform electron counting in a silicon-based single-electron pump that can be operated with high accuracy. Importantly, we show that the electron counting and the output current of the pump agree within the experimental accuracy. The electron counting scheme can be upgraded in our system into an error counting scheme where we detect only the error events, where an undesired number of electrons is transferred. Furthermore, a three waveform pumping protocol is introduced to demonstrate bidirectional pumping, where the pumped current can be reversed simply by tuning the phase of one of the waveforms. We conclude that the sensitivity of our charge sensor should be increased for the future experiments. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P36.00012: Experimental Analysis of Gas Ionization Mechanics for Standoff Isotope Identification Benjamin Graber, Dong Ho Wu Our previous work has established that gas ionization rate by gamma rays is strongly dependent on the type of gas and gamma radiation energies.~ We exploit such phenomena for the standoff detection and identification of radioactive materials using a set of gas cells, each containing a particular type of gas and a pair of ion counters.~ Recently we performed new experiments to investigate how ion production rate is affected by gas cell pressure, shielding constant of the gas cell, the detection distance, gas cell cross section, and the electric field of the ion counters.~ Optimizing these parameters allows us detection and identification of weak radioactive (\textless 75 uCi) isotopes, such as Am-241, Ba-133, Co-60, Cs-137, and Na-22 at distances over 10m.~ We attempted to combine some theoretical models of gas ionization and molecule models with our experimental data to form a complete picture of the mechanisms of gas ionization.~ We find ionization of argon gas is, in particular, interesting because the gas exhibits a significantly higher ionization rate when exposed to low energy gamma rays than higher energy gamma rays. [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P36.00013: Tandem Gravimetric and Volumetric Apparatus for Methane Sorption Measurements Jacob Burress, Donald Bethea Concerns about global climate change have driven the search for alternative fuels. Natural gas (NG, methane) is a cleaner fuel than gasoline and abundantly available due to hydraulic fracturing. One hurdle to the adoption of NG vehicles is the bulky cylindrical storage vessels needed to store the NG at high pressures (3600 psi, 250 bar). The adsorption of methane in microporous materials can store large amounts of methane at low enough pressures for the allowance of conformable, ``flat'' pressure vessels. The measurement of the amount of gas stored in sorbent materials is typically done by measuring pressure differences (volumetric, manometric) or masses (gravimetric). Volumetric instruments of the Sievert type have uncertainties that compound with each additional measurement. Therefore, the highest-pressure measurement has the largest uncertainty. Gravimetric instruments don't have that drawback, but can have issues with buoyancy corrections. An instrument will be presented with which methane adsorption measurements can be performed using both volumetric and gravimetric methods in tandem. The gravimetric method presented has no buoyancy corrections and low uncertainty. Therefore, the gravimetric measurements can be performed throughout an entire isotherm or just at the extrema to verify the results from the volumetric measurements. Results from methane sorption measurements on an activated carbon (MSC-30) and a metal-organic framework (Cu-BTC, HKUST-1, MOF-199) will be shown. New recommendations for calculations of gas uptake and uncertainty measurements will be discussed. [Preview Abstract] |
Wednesday, March 15, 2017 5:06PM - 5:18PM |
P36.00014: Study of radiation intensity characteristics from Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ high-$T_{c}$ superconducting terahertz emitters. T. Kashiwagi, T. Yuasa, H. Kubo, K. Sakamoto, C. Watanabe, T. Katsuragawa, T. Tanaka, Y. Komori, Y. Tanabe, R. Ota, G. Kuwano, M. Tsujimoto, R. Yoshizaki, T. Yamamoto, H. Minami, R. Klemm, K. Kadowaki According to our previous studies, the efficiency of the THz radiation from a high $T_{c}$ superconducting emitter can be improved greatly when the stand-alone mesa structure of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\, \delta }$ (Bi2212) single crystal and its sandwich structures are used for the emitter$^{1,2)}$. The radiation characteristics obtained from above devices indicate clearly that the thermal management of the THz emitters is most important issue in order to obtain good radiation performance and reproducibility. Recently, we have studied the radiation intensity characteristics of the high $T_{c}$ superconducting emitters, and compared the radiation characteristics of several rectangular mesa devices with different thickness up to \textasciitilde 5 micrometer. The radiation intensity tend to increase with increasing the thickness of the mesa structures. A few tens of micro watt level of output power was observed from the thicker mesa devices. The radiation intensity also strongly depends on the fabrication process of the mesa devices and condition of the single crystal of Bi2212 used for the mesa devices. The detail will be discussed in the meeting. 1) T. Kitamura \textit{et al.}, Appl. Phys. Lett. \textbf{105}, 202603 (2014) 2) T. Kashiwagi \textit{et al.}, Appl. Phys. Lett. \textbf{107}, 082601 (2015) [Preview Abstract] |
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