Showing papers in "Review of Scientific Instruments in 2011"

Invited review article: Single-photon sources and detectors

Abstract: We review the current status of single-photon-source and single-photon-detector technologies operating at wavelengths from the ultraviolet to the infrared. We discuss applications of these technologies to quantum communication, a field currently driving much of the development of single-photon sources and detectors.

A high temperature apparatus for measurement of the Seebeck coefficient

Abstract: A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.

A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS

Abstract: We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 μeV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.

A precise method for visualizing dispersive features in image plots

Abstract: In order to improve the advantages and the reliability of the second derivative method in tracking the position of extrema from experimental curves, we develop a novel analysis method based on the mathematical concept of curvature. We derive the formulas for the curvature in one and two dimensions and demonstrate their applicability to simulated and experimental angle-resolved photoemission spectroscopy data. As compared to the second derivative, our new method improves the localization of the extrema and reduces the peak broadness for a better visualization on intensity image plots.

The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.

Abstract: The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Note: Integration of trapped ion mobility spectrometry with mass spectrometry

Abstract: The integration of a trapped ion mobility spectrometer (TIMS) with a mass spectrometer (MS) for complementary fast, gas-phase mobility separation prior to mass analysis (TIMS-MS) is described. The ion transmission and mobility separation are discussed as a function of the ion source condition, bath gas velocity, analysis scan speed, RF ion confinement, and downstream ion optical conditions. TIMS mobility resolution depends on the analysis scan speed and the bath gas velocity, with the unique advantage that the IMS separation can be easily tuned from high speed (~25 ms) for rapid analysis to slower scans for higher mobility resolution (R > 80).

Rapid consolidation of powdered materials by induction hot pressing

Abstract: A rapid hot press system in which the heat is supplied by RF induction to rapidly consolidate thermoelectric materials is described. Use of RF induction heating enables rapid heating and consolidation of powdered materials over a wide temperature range. Such rapid consolidation in nanomaterials is typically performed by spark plasma sintering (SPS) which can be much more expensive. Details of the system design, instrumentation, and performance using a thermoelectric material as an example are reported. The Seebeck coefficient, electrical resistivity, and thermal diffusivity of thermoelectric PbTe material pressed at an optimized temperature and time in this system are shown to agree with material consolidated under typical consolidation parameters.

High-energy x-ray backlighter spectrum measurements using calibrated image plates

Abstract: The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji™ MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver Kα x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device.

High-temperature materials testing with full-field strain measurement: experimental design and practice.

Abstract: Experimental characterization of the thermomechanical response of ceramic composites at very high temperatures is plagued by challenges associated with imaging and strain measurement. The problems involve illumination, heat haze, and surface contrast. Techniques that address these challenges have been developed and implemented in a laser heating facility, enabling non-contact strain measurement via digital image correlation. The thermomechanical characterization of both a Ni-based superalloy and a C/SiC composite are used to demonstrate the efficacy of experimental practices in realizing such measurements at temperatures up to 1500 °C.

The double electrostatic ion ring experiment: A unique cryogenic electrostatic storage ring for merged ion-beams studies

Abstract: We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate “rings” and merged over a common straight section The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology

A high-repetition rate scheme for synchrotron-based picosecond laser pump/x-ray probe experiments on chemical and biological systems in solution

Abstract: We present the extension of time-resolved optical pump/x-ray absorption spectroscopy (XAS) probe experiments towards data collection at MHz repetition rates. The use of a high-power picosecond laser operating at an integer fraction of the repetition rate of the storage ring allows exploitation of up to two orders of magnitude more x-ray photons than in previous schemes based on the use of kHz lasers. Consequently, we demonstrate an order of magnitude increase in the signal-to-noise of time-resolved XAS of molecular systems in solution. This makes it possible to investigate highly dilute samples at concentrations approaching physiological conditions for biological systems. The simplicity and compactness of the scheme allows for straightforward implementation at any synchrotron beamline and for a wide range of x-ray probe techniques, such as time-resolved diffraction or x-ray emission studies.

The Twente turbulent Taylor-Couette (T3C) facility: strongly turbulent (multiphase) flow between two independently rotating cylinders.

Abstract: A new turbulent Taylor–Couette system consisting of two independently rotating cylinders has been constructed. The gap between the cylinders has a height of 0.927 m, an inner radius of 0.200 m, and a variable outer radius (from 0.279 to 0.220 m). The maximum angular rotation rates of the inner and outer cylinder are 20 and 10 Hz, respectively, resulting in Reynolds numbers up to 3.4 × 106 with water as working fluid. With this Taylor–Couette system, the parameter space (Rei, Reo, η) extends to (2.0 × 106, ±1.4 × 106, 0.716−0.909). The system is equipped with bubble injectors, temperature control, skin-friction drag sensors, and several local sensors for studying turbulent single-phase and two-phase flows. Inner cylinder load cells detect skin-friction drag via torque measurements. The clear acrylic outer cylinder allows the dynamics of the liquid flow and the dispersed phase (bubbles, particles, fibers, etc.) inside the gap to be investigated with specialized local sensors and nonintrusive optical imaging techniques. The system allows study of both Taylor–Couette flow in a high-Reynolds-number regime, and the mechanisms behind skin-friction drag alterations due to bubble injection, polymer injection, and surface hydrophobicity and roughness

Five-element Johann-type x-ray emission spectrometer with a single-photon-counting pixel detector.

Abstract: A Johann-type spectrometer with five spherically bent crystals and a pixel detector was constructed for a range of hard x-ray photon-in photon-out synchrotron techniques, covering a Bragg-angle range of 60°–88°. The spectrometer provides a sub emission line width energy resolution from sub-eV to a few eV and precise energy calibration, better than 1.5 eV for the full range of Bragg angles. The use of a pixel detector allows fast and easy optimization of the signal-to-background ratio. A concentration detection limit below 0.4 wt% was reached at the Cu Kα1 line. The spectrometer is designed as a modular mobile device for easy integration in a multi-purpose hard x-ray synchrotron beamline, such as the SuperXAS beamline at the Swiss Light Source.

The art of electrochemical etching for preparing tungsten probes with controllable tip profile and characteristic parameters

Abstract: Using custom made experimental apparatus, the art of electrochemical etching was systematically studied for fabricating micro/nano tungsten probes with controllable tip profiles of exponential, conical, multidiameter, and calabashlike shapes. The characteristic parameters of probe including length, aspect ratio, and tip apex radius could also be well defined. By combining of static and dynamic etching, the conical-shape probe with length up to several millimeters, controllable tip apex radius, and cone angle could be fabricated. In addition, by continuously lifting the tungsten wire up during the electrochemical etching with different speeds and distances, the multidiameter shape probe could be fabricated. Finally by controlling the anodic flow, the multiple “neck-in” could be realized creating a calabashlike probe. The aspect ratio of probes depends on (i) the effective contact time between the surrounding electrolyte and the wire, (ii) the neck-in position of immersed tungsten wire. Under the optimized ...

The use of dynamic light scattering and Brownian microscopy to characterize protein aggregation

Abstract: Dynamic light scattering (DLS) is often used to monitor aggregation in protein solutions. Here, we explore the veracity of the aggregate sizes, size distribution widths, concentrations, and lifetime resulting from DLS. We use as an example a solution of the protein lysozyme in which dense liquid clusters of radius about 100 nm reproducibly exist. We compare the results of DLS to those of Brownian microscopy. We show that because of the sixth power dependence of the scattered light intensity on the size of the scatterers, DLS overestimates the mean size of the clusters. The factor of overestimation depends on the shape of the size distribution and is ∼1.6 × in the studied solution. The related underestimate of the cluster concentration is ∼10 ×. The CONTIN algorithm, often employed to process DLS data, may, in some instances, produce non-physical results. We put forth an alternative method to determine the aggregates’ sizes, concentrations, and volume fractions. We show that DLS yields a reliable width of the cluster size distribution only if the cluster concentration is above 109 cm−3 and their volume fraction is above 10−6. DLS yields a lower bound of the cluster lifetime, which may be orders of magnitude lower than the real one.

A scanning probe-based pick-and-place procedure for assembly of integrated quantum optical hybrid devices.

Abstract: Integrated quantum optical hybrid devices consist of fundamental constituents such as single emitters and tailored photonic nanostructures. A reliable fabrication method requires the controlled deposition of active nanoparticles on arbitrary nanostructures with highest precision. Here, we describe an easily adaptable technique that employs picking and placing of nanoparticles with an atomic force microscope combined with a confocal setup. In this way, both the topography and the optical response can be monitored simultaneously before and after the assembly. The technique can be applied to arbitrary particles. Here, we focus on nanodiamonds containing single nitrogen vacancy centers, which are particularly interesting for quantum optical experiments on the single photon and single emitter level.

Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center

Abstract: Highly efficient spin- and angle-resolved photoelectron spectrometer named ESPRESSO (Efficient SPin REsolved SpectroScopy Observation) machine has been developed at the beamline BL-9B in Hiroshima Synchrotron Radiation Center. Combination of high-resolution hemispherical electron analyzer and the high-efficient spin detector based on very low energy electron diffraction by the ferromagnetic target makes the high-energy resolution and angular resolution compatible with spin- and angle-resolved photoemission (SARPES) measurement. 7.5 meV in energy and ±0.18° in angular resolution have been achieved with spin resolution. The ESPRESSO machine, combination of quick energy-band dispersion measurement and Fermi surface mapping by two-dimensional electron detector for the spin integrated ARPES and the high-efficient spin analysis by the efficient spin detector realizes the comprehensive investigation of spin electronic structure of materials.

On the implementation of computed laminography using synchrotron radiation.

Abstract: Hard x rays from a synchrotron source are used in this implementation of computed laminography for three-dimensional (3D) imaging of flat, laterally extended objects. Due to outstanding properties of synchrotron light, high spatial resolution down to the micrometer scale can be attained, even for specimens having lateral dimensions of several decimeters. Operating either with a monochromatic or with a white synchrotron beam, the method can be optimized to attain high sensitivity or considerable inspection throughput in synchrotron user and small-batch industrial experiments. The article describes the details of experimental setups, alignment procedures, and the underlying reconstruction principles. Imaging of interconnections in flip-chip and wire-bonded devices illustrates the peculiarities of the method compared to its alternatives and demonstrates the wide application potential for the 3D inspection and quality assessment in microsystem technology.

Invited Article: The coherent optical laser beam recombination technique (COLBERT) spectrometer: Coherent multidimensional spectroscopy made easier

Abstract: We have developed an efficient spectrometer capable of performing a wide variety of coherent multidimensional measurements at optical wavelengths. The two major components of the largely automated device are a spatial beam shaper which controls the beam geometry and a spatiotemporal pulse shaper which controls the temporal waveform of the femtosecond pulse in each beam. We describe how to construct, calibrate, and operate the device, and we discuss its limitations. We use the exciton states of a semiconductor nanostructure as a working example. A series of complex multidimensional spectra—displayed in amplitude and real parts—reveals increasingly intricate correlations among the excitons.

An experimental assembly for precise measurement of thermal accommodation coefficients

Abstract: An experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations. Results are obtained primarily through measurement of the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Measured heat-flux data are used in a formula based on Direct Simulation Monte Carlo (DSMC) simulations to determine the coefficients. The assembly also features a complementary capability for measuring the variation in gas density between the plates using electron-beam fluorescence. Surface materials examined include 304 stainless steel, gold, aluminum, platinum, silicon, silicon nitride, and polysilicon. Effects of gas composition, surface roughness, and surface contamination have been investigated with this system; the behavior of gas mixtures has also been explored. Without special cleaning procedures, thermal accommodation coefficients for most materials and surface finishes were determined to be near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Surface cleaning by in situ argon-plasma treatment reduced coefficient values by up to 0.10 for helium and by ∼0.05 for nitrogen and argon. Results for both single-species and gas-mixture experiments compare favorably to DSMC simulations.

Pound-Drever-Hall-locked, frequency-stabilized cavity ring-down spectrometer

Abstract: We describe a high sensitivity and high spectral resolution laser absorption spectrometer based upon the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We used the Pound-Drever-Hall (PDH) method to lock the probe laser to the high-finesse ring-down cavity. We show that the concomitant narrowing of the probe laser line width leads to dramatically increased ring-down event acquisition rates (up to 14.3 kHz), improved spectrum signal-to-noise ratios for weak O(2) absorption spectra at λ = 687 nm and substantial increase in spectrum acquisition rates compared to implementations of FS-CRDS that do not incorporate high-bandwidth locking techniques. The minimum detectable absorption coefficient and the noise-equivalent absorption coefficient for the spectrometer are about 2×10(-10) cm(-1) and 7.5×10(-11) cm(-1)Hz(-1/2), respectively.

In situ nanomechanical testing in focused ion beam and scanning electron microscopes.

Abstract: The recent interest in size-dependent deformation of micro- and nanoscale materials has paralleled both technological miniaturization and advancements in imaging and small-scale mechanical testing methods. Here we describe a quantitative in situ nanomechanical testing approach adapted to a dual-beam focused ion beam and scanning electron microscope. A transducer based on a three-plate capacitor system is used for high-fidelity force and displacement measurements. Specimen manipulation, transfer, and alignment are performed using a manipulator, independently controlled positioners, and the focused ion beam. Gripping of specimens is achieved using electron-beam assisted Pt-organic deposition. Local strain measurements are obtained using digital image correlation of electron images taken during testing. Examples showing results for tensile testing of single-crystalline metallic nanowires and compression of nanoporous Au pillars will be presented in the context of size effects on mechanical behavior and highlight some of the challenges of conducting nanomechanical testing in vacuum environments.

A new white beam x-ray microdiffraction setup on the BM32 beamline at the European Synchrotron Radiation Facility

Abstract: A white beam microdiffraction setup has been developed on the bending magnet source BM32 at the European Synchrotron Radiation Facility. The instrument allows routine submicrometer beam diffraction to perform orientation and strain mapping of polycrystalline samples. The setup features large source to optics distances allowing large demagnification ratios and small beam sizes. The optics of the beamline is used for beam conditioning upstream a secondary source, suppressing any possible interference of beam conditioning on beam size and position. The setup has been designed for an easy and efficient operation with position control tools embedded on the sample stage, a high magnification large aperture optical microscope, and fast readout detectors. Switching from the white beam mode to the monochromatic mode is made easy by an automatic procedure and allows the determination of both the deviatoric and hydrostatic strain tensors.

Development of high-repetition-rate laser pump/x-ray probe methodologies for synchrotron facilities

Abstract: We describe our implementation of a high repetition rate (54 kHz-6.5 MHz), high power (>10 W), laser system at the 7ID beamline at the Advanced Photon Source for laser pump/x-ray probe studies of optically driven molecular processes. Laser pulses at 1.06 μm wavelength and variable duration (10 or 130 ps) are synchronized to the storage ring rf signal to a precision of ~250 fs rms. Frequency doubling and tripling of the laser radiation using nonlinear optical techniques have been applied to generate 532 and 355 nm light. We demonstrate that by combining a microfocused x-ray probe with focused optical laser radiation the requisite fluence (with <10 μJ/pulse) for efficient optical excitation can be readily achieved with a compact and commercial laser system at megahertz repetition rates. We present results showing the time-evolution of near-edge x-ray spectra of a well-studied, laser-excited metalloporphyrin, Ni(II)-tetramesitylporphyrin. The use of high repetition rate, short pulse lasers as pump sources will dramatically enhance the duty cycle and efficiency in data acquisition and hence capabilities for laser-pump/x-ray probe studies of ultrafast structural dynamics at synchrotron sources.

Single-shot beam-position monitor for x-ray free electron laser.

Abstract: We have developed an x-ray beam-position monitor for detecting the radiation properties of an x-ray free electron laser (FEL). It is composed of four PIN photodiodes that detect backscattered x-rays from a semitransparent diamond film placed in the beam path. The signal intensities from the photodiodes are used to compute the beam intensity and position. A proof-of-principle experiment at a synchrotron light source revealed that the error in the beam position is reduced to below 7 μm by using a nanocrystal diamond film prepared by plasma-enhanced chemical vapor deposition. Owing to high dose tolerance and transparency of the diamond film, the monitor is suitable for routine diagnostics of extremely intense x-ray pulses from the FEL.

Demonstration of a room temperature 2.48-2.75 THz coherent spectroscopy source.

Abstract: We report the first demonstration of a continuous wave coherent source covering 2.48-2.75 THz, with greater than 10% instantaneous tuning bandwidth and having 1-14 μW of output power at room temperature. This source is based on a 91.8-101.8 GHz synthesizer followed by a power amplifier and three cascaded frequency triplers. It demonstrates for the first time that purely electronic solid-state sources can generate a useful amount of power in a region of the electromagnetic spectrum where lasers (solid state or gas) were previously the only available coherent sources. The bandwidth, agility, and operability of this THz source have enabled wideband, high resolution spectroscopic measurements of water, methanol, and carbon monoxide with a resolution and signal-to-noise ratio unmatched by any other existing system, providing new insight in the physics of these molecules. Furthermore, the power and optical beam quality are high enough to observe the Lamb-dip effect in water. The source frequency has an absolute accuracy better than 1 part in 10(12) and the spectrometer achieves sub-Doppler frequency resolution better than 1 part in 10(8). The harmonic purity is better than 25 dB. This source can serve as a coherent signal for absorption spectroscopy, a local oscillator for a variety of heterodyne systems and can be used as a method for precision control of more powerful but much less frequency agile quantum mechanical terahertz sources.

Linac Coherent Light Source soft x-ray materials science instrument optical design and monochromator commissioning.

Abstract: We present the x-ray optical design of the soft x-ray materials science instrument at the Linac Coherent Light Source, consisting of a varied line-spaced grating monochromator and Kirkpatrick-Baez refocusing optics. Results from the commissioning of the monochromator are shown. A resolving power of 3000 was achieved, which is within a factor of two of the design goal.

The response of CR-39 nuclear track detector to 1–9 MeV protons

Abstract: The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92–9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. Effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.

Errors in particle tracking velocimetry with high-speed cameras.

Abstract: Velocity errors in particle tracking velocimetry (PTV) are studied. When using high-speed video cameras, the velocity error may increase at a high camera frame rate. This increase in velocity error is due to particle-position uncertainty, which is one of the two sources of velocity errors studied here. The other source of error is particle acceleration, which has the opposite trend of diminishing at higher frame rates. Both kinds of errors can propagate into quantities calculated from velocity, such as the kinetic temperature of particles or correlation functions. As demonstrated in a dusty plasma experiment, the kinetic temperature of particles has no unique value when measured using PTV, but depends on the sampling time interval or frame rate. It is also shown that an artifact appears in an autocorrelation function computed from particle positions and velocities, and it becomes more severe when a small sampling-time interval is used. Schemes to reduce these errors are demonstrated.

Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics

Abstract: This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths