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  • 1
    Online Resource
    Online Resource
    A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes
    AIP Publishing ; 2008
    In:  Review of Scientific Instruments Vol. 79, No. 9 ( 2008-09-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 79, No. 9 ( 2008-09-01)
    Abstract: An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry–Perot interferometer under an angle inside the electron cyclotron wave (ECW) beam. ECE measurements are obtained during high power ECRH operation. This demonstrates the successful operation of the diagnostic and, in particular, a sufficient suppression of the gyrotron component preventing it from interfering with ECE measurements. When integrated into a feedback system for the control of plasma instabilities this line-of-sight ECE diagnostic removes the need to localize the instabilities in absolute coordinates.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.2976665
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 2
    Online Resource
    Online Resource
    Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization
    AIP Publishing ; 2009
    In:  Review of Scientific Instruments Vol. 80, No. 10 ( 2009-10-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 80, No. 10 ( 2009-10-01)
    Abstract: A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136–140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.3244091
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control
    AIP Publishing ; 2011
    In:  Review of Scientific Instruments Vol. 82, No. 6 ( 2011-06-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 82, No. 6 ( 2011-06-01)
    Abstract: An intermediate frequency (IF) band digitizing radiometer system in the 100–200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototype system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.3594101
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2011
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 4
    Online Resource
    Online Resource
    Modification of the collective Thomson scattering radiometer in the search for parametric decay on TEXTOR
    AIP Publishing ; 2012
    In:  Review of Scientific Instruments Vol. 83, No. 11 ( 2012-11-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 83, No. 11 ( 2012-11-01)
    Abstract: Strong scattering of high-power millimeter waves at 140 GHz has been shown to take place in heating and current-drive experiments at TEXTOR when a tearing mode is present in the plasma. The scattering signal is at present supposed to be generated by the parametric decay instability. Here we describe the heterodyne detection system used to characterize the newly discovered signal measured at TEXTOR, and we present spectral shapes in which the signal can appear under different conditions. The radiation is collected by the receiver through a quasi-optical transmission line that is independent of the electron cyclotron resonance heating transmission line, and so the scattering geometry is variable. The signal is detected with 42 frequency channels ranging from 136 to 142 GHz. We demonstrate that the large signal does not originate from gyrotron spurious radiation. The measured signal agrees well with independent backscattering radiometer data.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.4768668
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2012
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 5
    Online Resource
    Online Resource
    Texture analysis of smooth i n   s i t u laser ablated YBa2Cu3O7 thin films on (100) SrTiO3
    AIP Publishing ; 1990
    In:  Journal of Applied Physics Vol. 68, No. 12 ( 1990-12-15), p. 6507-6509
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 68, No. 12 ( 1990-12-15), p. 6507-6509
    Abstract: The texture of YBa2Cu3O7 thin films on (100) SrTiO3, grown by in situ laser ablation, was investigated by x-ray diffraction. The surface morphology is smooth with only 105 cm−2 particulates of about 0.1 μm in diameter. High-resolution x-ray diffraction shows that the c-axis of YBa2Cu3O7 is epitaxially aligned with the [001] direction of SrTiO3 irrespective of the misorientation. The {018} pole figure of YBa2Cu3O7 shows a fourfold symmetry which indicates that the films are ordered with respect to the substrate lattice. Moreover, the alignment in the {018} pole figure of the (220) reflections of SrTiO3 and the (018) reflections of YBa2Cu3O7 indicates that over the whole surface of the film the a- and b-axes of YBa2Cu3O7 are aligned along the [100] and [010] direction of SrTiO3. The epitaxial nature of the films, the low density of particulates, and the lack of interdiffusion as concluded from secondary ion mass spectrometry measurements, allows for the preparation of heteroepitaxial stacks containing high-Tc superconductors.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.346851
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1990
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    Online Resource
    Online Resource
    Magnetoresistance in Chalcogenide Spinels
    AIP Publishing ; 1969
    In:  Journal of Applied Physics Vol. 40, No. 3 ( 1969-03-01), p. 958-963
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 40, No. 3 ( 1969-03-01), p. 958-963
    Abstract: The consequences of a simple type of exchange interaction between charge carriers in a broad energy band and localized magnetic moments will be discussed for a ferromagnetic semiconductor. The interaction causes (1) a splitting of the energy band into two bands for the different spin directions, (2) spin disorder scattering of the charge carriers. The calculated temperature and field dependence of the magnetoresistance are compared with experimental data of CdCr2Se4. The magnetoresistance of compounds MeCr2S4, Me=Fe, Co, Cd was measured. For n-type CdCr2S4 and for p-type FeCr2S4 and p-type CoCr2S4, the magnetoresistance −Δρ/ρ0 was found to be 0.78, 0.05, and 0.05, respectively, at 12 kOe near Tc, whereas n-type FeCr2S4 and CoCr2S4 show no effect. The magnetoresistance of the system Fe1−xCdxCr2S4 was also measured. The temperature dependence of the polar magneto-optical Kerr effect of CdCr2Se4 is discussed in connection with the described model for the energy bands.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1657802
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1969
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 7
    Online Resource
    Online Resource
    Ground State of Divalent Co Ions in Cs3CoCl5 and Cs3CoBr5
    AIP Publishing ; 1966
    In:  The Journal of Chemical Physics Vol. 44, No. 10 ( 1966-05-15), p. 3719-3725
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 44, No. 10 ( 1966-05-15), p. 3719-3725
    Abstract: The 4A2 ground state of tetrahedrally coordinated divalent cobalt ions in Cs3CoCl5 and Cs3CoBr5 is investigated with magnetic-susceptibility measurements and paramagnetic resonance in pulsed magnetic fields up to 90 kOe at frequencies in the 70- and 120-Gc/sec bands. The first excited state (4T2) which lies ∼3000 cm−1 above the ground state is studied optically on Cs3Zn0.9Co0.1Cl5. The sign of the splitting of the 4T2 state is opposite to that expected from the observed negative zero-field splitting of the ground state.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1726525
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1966
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 8
    Online Resource
    Online Resource
    Ferromagnetism in Compounds with Pyrochlore Structure
    AIP Publishing ; 1967
    In:  Journal of Applied Physics Vol. 38, No. 3 ( 1967-03-01), p. 944-945
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 38, No. 3 ( 1967-03-01), p. 944-945
    Abstract: The compounds (RE)23+Cr3+Sb5+O7 (RE=Y or a rare earth except Ce, Pm, Lu) with pyrochlore structure have asymptotic Curie temperatures between 4° and 16°K; Ho2CrSbO7 and Dy2CrSbO7 are ferromagnetic below Tc=10°K and Tc=16°K, respectively. The moments of the chromium and the rare-earth ions are oriented parallel in these latter two compounds. The positive Cr3+–Cr3+ interaction in the pyrochlore structure is compared to the interaction between chromium ions in other compounds.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1709693
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1967
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 9
    Online Resource
    Online Resource
    Miniaturized ultrasound scanner by electrowetting
    AIP Publishing ; 2010
    In:  Applied Physics Letters Vol. 97, No. 6 ( 2010-08-09)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 97, No. 6 ( 2010-08-09)
    Abstract: An ultrasound imaging technology based on electrowetting has been developed and integrated in a miniaturized ultrasound scanner. The feasibility of scanning the ultrasound beam of a single-piston transducer in a three-dimensional space by using electrowetting is demonstrated. The technology has a high potential to be embedded in devices where size restrictions do not allow the use of traditional ultrasound phased-array transducers.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.3478455
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2010
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 10
    Online Resource
    Online Resource
    Infrared Faraday Rotation in Ferrites
    AIP Publishing ; 1969
    In:  Journal of Applied Physics Vol. 40, No. 3 ( 1969-03-01), p. 1230-1231
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 40, No. 3 ( 1969-03-01), p. 1230-1231
    Abstract: The absorption and Faraday rotation of crystals of the spinel ferrites Li0.5Fe2.5O4, NiFe2O4, and MgFe2O4 and of the hexagonal ferrites BaFe12O19 and Ba2Zn2Fe12O22 have been measured at 300°K between 1 and 8 μ. The rotation consists of a nearly wavelength-independent term θM arising from the magnetic resonance and of a strongly dispersive term θd originating mainly from electronic transitions of Fe3+. As in YIG, the Fe3+ ions in tetrahedral and octahedral coordination contribute differently to θd. The experimental curves of the Faraday rotation of YIG, Li0.5Fe2.5O4 and MgFe2O4 can be described rather accurately with the same constants for the rotary powers of Fe3+ in tetrahedra and of Fe3+ in octahedra. Also the contribution of Ni2+ to θd in NiFe2O4 at 80°, 300°, and 373°K has been determined.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1657604
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1969
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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