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  • 1
    Publication Date: 2014-09-10
    Description: The contribution of the phonon drag effect to the Seebeck coefficient of P-doped ultrathin Si-on-insulator (SOI) layers with a thickness of 9–100 nm is investigated for near-room-temperature applications. The contribution is found to be significant in the lightly doped region and to depend on the carrier concentration with increasing carrier concentration above ∼5 × 10 18  cm −3 . Moreover, the contribution is not influenced by SOI thickness above 9 nm. On the basis of phonon mean-free-path calculations considering phonon scattering processes, the phonon drag part of the SOI Seebeck coefficient in the lightly doped region is mainly governed by phonon-phonon scattering. Furthermore, in higher concentration regions, the dependence of phonon drag can be qualitatively explained by the interaction between phonons and doped impurities.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 2
    Publication Date: 2016-10-28
    Description: We propose a basic formula and demonstration for a high-resolution quasi-elastic neutron scattering (QENS) by combining the time-of-flight (TOF) method with Modulation of Intensity by Zero Effort (MIEZE) type neutron spin echo spectroscopy. The MIEZE technique has the potential to develop a unique approach to study on slow dynamics of condensed matter; however, the energy resolution is limited owing to the hypersensitivity of the MIEZE signal contrast to the echo condition, which is strongly affected by the alignment of the instruments and the sample. The narrow allowance of the optimal alignment is a major obstacle to the wide use of this technique. Combining the TOF method with MIEZE (TOF-MIEZE), the hypersensitivity of MIEZE signals is significantly alleviated with a short pulsed beam. This robustness is very useful to optimize experimental alignments and enables accurate measurements of QENS. The experimental results demonstrate the characteristic of the TOF-MIEZE technique and are well described by the formula presented in this study.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We are constructing a diagnostic system to measure the electric field ((approximately-greater-than)100 kV/cm) of a free-electron laser (FEL) beam when injected into the plasma of the Microwave Tokamak Experiment (MTX). The apparatus allows a crossed-beam measurement, with 2 cm spatial resolution in the plasma, involving the FEL beam (with 140 GHz, ≈1 GW ECH pulses), a neutral helium beam, and a dye laser beam. After the laser beam pumps metastable helium atoms to higher excited states, their decay light is detected by an efficient optical system. Because of the Stark effect arising from the FEL electric field (E), a forbidden transition can be strongly induced. The intensity of emitted light resulting from the forbidden transition is proportional to E2. Because photon counting rates are estimated to be low, extra effort is made to minimize background and noise levels. It is possible that the lower E of an MTX gyrotron-produced ECH beam with its longer duration pulses can also be measured using this method. Other applications of the apparatus described here may include measurements of ion temperature (using charge-exchange recombination), edge-density fluctuations, and core impurity concentrations.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A supersonic helium beam source operated in pulse mode was constructed for direct measurement of electric field distribution in the tokamak plasma edge region with the aid of laser-induced fluorescence (LIF) technique. In this technique only the polarization has to be observed of a LIF resulting from a laser-excited forbidden transition due to the Stark effect and the electric quadrupole to determine the electric field strength. No calibration is needed of the absolute intensity of LIF and tunable laser used. The helium atom beam density was obtained (about 1020 He atoms cm−2 s−1) at a distance of 7 cm from the pulsed nozzle. A model-type experiment to make clear the influence of a magnetic field on the LIF is reported. Design study was also made to install the supersonic beam and spectroscopic measurement system on a medium size tokamak. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1036-1037 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method combining the techniques of laser blowoff and laser-induced fluorescence has been developed in order to measure the local electron density below 1013 cm−3. Characteristics of a Li0 beam produced by laser blowoff of a thin Li film are investigated using beam–plasma interactions and laser-induced fluorescence. Such a beam has a near-Maxwellian velocity distribution with a temperature around 4.5 eV and a density of the order of 1010 cm−3 at a distance of about 1 m from the film target. The feasibility of measuring electron density with this Li0 beam and a dye laser is demonstrated with an ECR plasma.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 903-907 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A sensitive and reliable spectroscopic system measuring simultaneously polarized components of time-resolved laser induced fluorescence (LIF) is being developed for determining electric field distribution in transient plasmas under strong magnetic field. In this LIF method which we have already proposed, only the polarization has to be observed of a LIF due to a laser-excited forbidden transition caused by both the Stark effect and the electric quadrupole (QDP) moment in the plasmas. Temporal evolution of both the polarized LIF components is simultaneously observed using a Glan–Thompson polarizing beamsplitter with extinction ratio of 10−5 and a pair of photomultipliers with fast rise time. The polarization components observed in a hollow cathode discharge He plasma under magnetic field of 2.5 kG were successfully analyzed and electric field distribution in the sheath region was accurately estimated using this procedure. It was also shown that electric field strength was determined from the intensity ratio of the Stark and QDP components separated in the strong magnetic field. We briefly discuss the applicability of this spectroscopic system to diagnostic in the edge region of tokamak plasmas. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2351-2356 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To measure local electric field in an rf-plugged sheet plasma in the RFC-XX-M open-ended machine, a spectroscopic system using a combined technique of Li-beam probing (laser blow-off method) and laser-induced fluorescence has been developed. A Li atom in the rf field can be populated to 42F by a stepwise laser pumping (22S→22P→42F) because of the Stark mixing between 42F and 42D. A cascade fluorescence of 610.4 nm (32D→22P) subsequent to the direct transition (42F→32D) was observed to estimate the rf field strength (rms) Erms. To correct the effect of electron collisions in the plasma, we observed a blue fluorescence consisting of two lines: a forbidden line of 460.2 nm (42F→22P) and an allowed line of 460.3 nm (42D→22P) induced by electron collisional transfer (42F→42D). From these intensities, we obtained Erms and electron density ne by solving numerically the rate equations, including the relevant radiative and collisional processes under the experimental conditions. Erms and ne were estimated to be 2.4 kV/cm and 3.1×1011 cm−3 near the center of the sheet plasma, respectively. It was found that the obtained Erms was enhanced by about 2.5 times with respect to the vacuum field (1 kV/cm). The obtained ne agreed well with ones by other methods. A spatial distribution of ne was also obtained from that of the Li0 resonance line (22P→22S) due to electron impact excitation. The present spectroscopic system is applicable to plasmas of ne(approximately-less-than)1013 cm−3 and static or quasi-static electric fields of E(approximately-greater-than)400 V/cm.
    Type of Medium: Electronic Resource
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