Development of low temperature atomic force microscopy with an optical beam deflection system capable of simultaneously detecting the lateral and vertical forces
In this study, we developed a low-temperature, frequency-modulationAFM using an optical beam deflectionsystem to simultaneously measure the vertical and lateral forces. In thissystem, the heat sources, such as alaser diode and a current-to-voltage converter, for measuring the photocurrent of the four-segmentedphotodiode are located outside the observation chamber to avoid a temperature increase of theAFM unit. The focused optical beam is three-dimensionally adjustable on the back side of the cantilever. We demonstrate low-noise displacement measurement of the cantilever and successful atomic resolutionimaging using the ver...
Source: Review of Scientific Instruments - September 27, 2016 Category: Physics Authors: Eiji Arima, Huanfei Wen, Yoshitaka Naitoh, Yan Jun Li and Yasuhiro Sugawara Source Type: research
Using VISAR to assess the M-band isotropy in hohlraums
In laser basedradiation flow experiments, drive variability can often overwhelm the physics sensitivity that one seeks to quantify.Hohlraums can help by providing a more symmetrized, Planckian-like source. However, at higher temperatures, the hohlraum ’s actual emission can deviate significantly from a truly blackbody, Lambertian source. At the National Ignition Facility (NIF), Dante provides the best quantification ofhohlraum output. Unfortunately, limited diagnostic access coupled with NIF ’s natural symmetry does not allow for Dantemeasurements at more than two angles. As part of the CEPHEUS campaign on NIF, proof-o...
Source: Review of Scientific Instruments - September 27, 2016 Category: Physics Authors: N. E. Lanier, J. L. Kline and J. Morton Source Type: research
Feasibility of line-ratio spectroscopy on helium and neon as edge diagnostic tool for Wendelstein 7-X
A beamemission spectroscopy system on thermal helium (He) and neon (Ne) has been set up at Wendelstein 7-X tomeasure edge electrontemperature and density profiles utilizing the line-ratio technique or its extension by the analysis of absolutely calibrated line emissions. The setup for a first systematic test of these techniques of quantitative atomic spectroscopy in the limiter startup phase (OP1.1) is reported together with firstmeasured profiles. This setup and the first results are an important test for developing the technique for the upcoming high density, lowtemperature islanddivertor regime. (Source: Review of Scientific Instruments)
Source: Review of Scientific Instruments - September 27, 2016 Category: Physics Authors: T. Barbui, M. Krychowiak, R. K önig, O. Schmitz, J. M. Muñoz Burgos, B. Schweer, A. Terra and W7-X Team Source Type: research
Ion gyroscale fluctuation measurement with microwave imaging reflectometer on KSTAR
Ion gyroscaleturbulent fluctuations with the poloidal wavenumberkθ∼ 3 cm−1 have beenmeasured in the core region of the neutral beam (NB) injected low confinement(L-mode) plasmas on Korea superconducting tokamak advanced research. Theturbulence poloidal wavenumbers are deduced from the frequencies and poloidal rotation velocities in the laboratory frame,measured by the multichannel microwave imaging reflectometer. Linear and nonlineargyrokinetic simulations also predict the unstable modes with the normalized wavenumberkθρs∼ 0.4, consistent with themeasurement. Comparison of themeasured frequencies with the intrinsi...
Source: Review of Scientific Instruments - September 27, 2016 Category: Physics Authors: W. Lee, J. Leem, G. S. Yun, H. K. Park, S. H. Ko, W. X. Wang, R. V. Budny, N. C. Luhmann Jr. and K. W. Kim Source Type: research
Measurement of deuterium density profiles in the H-mode steep gradient region using charge exchange recombination spectroscopy on DIII-D
Recent completion of a thirty two channel main-ion (deuterium)charge exchange recombination spectroscopy (CER)diagnostic on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion42, 614 (2002)] enables detailed comparisons between impurity and main-ion temperature, density, and toroidal rotation. In aH-mode DIII-D discharge, these newmeasurement capabilities are used to provide the deuterium density profile, demonstrate the importance of profile alignment between Thomson scattering and CERdiagnostics, and aid in determining the electron temperature at the separatrix. Sixteen sightlines cover the core of the plasma and another sixte...
Source: Review of Scientific Instruments - September 26, 2016 Category: Physics Authors: S. R. Haskey, B. A. Grierson, K. H. Burrell, C. Chrystal, R. J. Groebner, D. H. Kaplan, N. A. Pablant and L. Stagner Source Type: research
Fast-ion D α spectrum diagnostic in the EAST
In toroidal magnetic fusion devices, fast-ion D-alpha diagnostic (FIDA) is a powerful method to study the fast-ion feature. The fast-ioncharacteristics can be inferred from the Doppler shiftedspectrum of Dα light according to charge exchange recombination process between fast ions and probebeam. Since conceptual design presented in the last HTPD conference, significant progress has been made to apply FIDAsystems on the Experimental Advanced SuperconductingTokamak (EAST). Both co-current and counter-current neutralbeam injectors are available, and each can deliver 2-4 MWbeam power with 50-80 keVbeam energy. Presently, two ...
Source: Review of Scientific Instruments - September 26, 2016 Category: Physics Authors: Y. M. Hou, C. R. Wu, J. Huang, W. W. Heidbrink, M. G. von Hellermann, Z. Xu, Z. Jin, J. F. Chang, Y. B. Zhu, W. Gao, Y. J. Chen, B. Lyu, R. J. Hu, P. F. Zhang, L. Zhang, W. Gao, Z. W. Wu, Y. Yu, M. Y. Ye and EAST Team Source Type: research
Alignment and absolute wavelength calibration of imaging Bragg spectrometers
In the present and the next generation of fusion devices, imaging Braggspectrometers are keydiagnostics tomeasureplasma parameters in the hot core, especially iontemperature andplasma rotation. The latter quantities are routinely obtained using the Doppler-width and -shift of the emittedspectral lines, respectively. Line shiftmeasurements require absolute accuracies Δλ/λ of about 10 ppm, where λ-is the observed wavelength. For ITER and the present fusion devices,spectral lines of He-and H-like argon, iron, and krypton as well as Ne-like tungsten are foreseen for themeasurements. For these lines, K α lines can be found...
Source: Review of Scientific Instruments - September 26, 2016 Category: Physics Authors: G. Bertschinger, O. Marchuk and R. Barnsley Source Type: research
Note: An in situ method for measuring the non-linear response of a Fabry-Perot cavity
The transfercavity is a very important frequency reference forlaser stabilization and is widely used for applications such as precisionmeasurements andlaser cooling of ions or molecules. But the non-linear response of thepiezoelectric ceramictransducer(PZT) in theFabry-Perotcavity limits the performance of thelaser stabilization. Thus,measuring and controlling such non-linearity is essential. Here we report anin situ, optical method to characterize this non-linearity bymeasuring the resonant signals of a dual-frequency laser. The differentialmeasurement makes it insensitive to the laser andcavity drifts, while maintaining ...
Source: Review of Scientific Instruments - September 26, 2016 Category: Physics Authors: Wenhao Bu, Mengke Liu, Dizhou Xie and Bo Yan Source Type: research
A wide-field TCSPC FLIM system based on an MCP PMT with a delay-line anode
We report on the implementation of a wide-field time-correlated singlephoton counting(TCSPC) method forfluorescence lifetimeimaging (FLIM). It is based on a 40 mm diameter crossed delay lineanodedetector, where the readout is performed by three standardTCSPC boards. Excitation is performed by a picosecond diode laser with 50 MHz repetition rate. Thephoton arrival timing is obtained directly from the microchannel plates, with an instrumental response of ∼190 to 230 ps full width at half maximum depending on the position on the photocathode. The position of thephoton event is obtained from the pulse propagation time along ...
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: Wolfgang Becker, Liisa M. Hirvonen, James Milnes, Thomas Conneely, Ottmar Jagutzki, Holger Netz, Stefan Smietana and Klaus Suhling Source Type: research
Design of a high-bunch-charge 112-MHz superconducting RF photoemission electron source
High-bunch-chargephotoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers.Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent ele...
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: T. Xin, J. C. Brutus, Sergey A. Belomestnykh, I. Ben-Zvi, C. H. Boulware, T. L. Grimm, T. Hayes, Vladimir N. Litvinenko, K. Mernick, G. Narayan, P. Orfin, I. Pinayev, T. Rao, F. Severino, J. Skaritka, K. Smith, R. Than, J. Tuozzolo, E. Wang, B. Xiao, H. X Source Type: research
A heat-sinking self-referencing fiber optic emission probe
A novel heat-sinking, self-referencingfiber optic emission probe having asapphire fiber probe head is described. Thelaser heating effect in a GaAs wafer (on a polytetrafluoroethylene (PTFE) platform) has beenmeasured with the probe in both the noncontact proximity mode and the contact mode. The GaAs/PTFE composite was selected to simulate thethermal conductivity of animal tissues. It was found that for the same laser power delivered to the wafer, the temperature rise in the contact mode was only 42% of that in the proximity mode. Additionally, a demonstration of the self-referencing capability of the probe is also presente...
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: Nicholas Djeu and Yutaka Shimoji Source Type: research
Quantum limited heterodyne detection of spin noise
Spinnoise spectroscopy is a powerful technique for studying spin relaxation in semiconductors. In this article, we propose an extension of this technique based on opticalheterodyne detection of spinnoise, which provides several key advantages compared to conventional spinnoise spectroscopy:detection of high frequency spinnoise not limited bydetector bandwidth or sampling rates of digitizers, quantum limited sensitivity even in case of very weak probe power, and possible amplification of the spinnoise signal.Heterodyne detection of spinnoise is demonstrated on insulating n-doped GaAs. From measurements of spinnoise spectra ...
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: S. Cronenberger and D. Scalbert Source Type: research
Publisher ’s Note: “Gaseous electron multiplier-based soft x-ray plasma diagnostics development: Preliminary tests at ASDEX Upgrade” [Rev. Sci. Instrum. 87, 11E325 (2016)]
(Source: Review of Scientific Instruments)
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: M. Chernyshova, K. Malinowski, T. Czarski, A. Woje ński, D. Vezinet, K. T. Poźniak, G. Kasprowicz, D. Mazon, A. Jardin, A. Herrmann, E. Kowalska-Strzęciwilk, R. Krawczyk, P. Kolasiński, W. Zabołotny, P. Zienkiewicz, ASDEX Upgrade Team and and Eurofus Source Type: research
Optimization and application of cooled avalanche photodiodes for spectroscopic fluctuation measurements with ultra-fast charge exchange recombination spectroscopy
The Ultra-FastCharge Exchange RecombinationSpectroscopy (UF-CHERS)diagnostic is a highly specializedspectroscopic instrument with 2 spatial channels consisting of 8 spectral channels each and a resolution of ∼0.25 nm deployed at DIII-D tomeasureturbulent iontemperaturefluctuations.Charge exchange emissions are obtained between 528 and 530 nm with 1μs time resolution to studyplasma instabilities. A primary challenge of extractingfluctuationmeasurements from raw UF-CHERS signals is photon and electronicnoise. In order to reduce dark current, theAvalanche Photodiode(APD) detectors are thermo-electrically cooled. State-of-t...
Source: Review of Scientific Instruments - September 23, 2016 Category: Physics Authors: D. D. Truong, R. J. Fonck and G. R. McKee Source Type: research
Determination of relative krypton fission product yields from 14 MeV neutron induced fission of 238U at the National Ignition Facility
Precisely-known fission yield distributions are needed to determine a fissioningisotope and the incidentneutron energy in nuclear security applications. 14 MeVneutrons from DTfusion at the National Ignition Facility induce fission in depleteduranium contained in the target assemblyhohlraum. The fission yields of Krisotopes (85m, 87, 88, and 89) are measured relative to the cumulative yield of88Kr and compared to previously tabulated values. The results from this experiment and England and Rider are in agreement, except for the85mKr/88Kr ratio, which may be the result of incorrectnuclear data. (Source: Review of Scientific Instruments)
Source: Review of Scientific Instruments - September 22, 2016 Category: Physics Authors: E. R. Edwards, W. S. Cassata, C. A. Velsko, C. B. Yeamans and D. A. Shaughnessy Source Type: research
