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  • 1
    Electronic Resource
    Electronic Resource
    Dither-free stabilization of CH3OH pumping sources (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1997-1997 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A dither-free stabilization scheme was reported recently1 in which the optical transmission through an absorption cell filled with CH2F2 provided an error signal necessary to stabilize the 214-μm line of CH2F2. Measurements have indicated that this technique is difficult to apply to the 119-μm line of CH3OH due to a lack of contrast in the absorption features of CH3OH over the tuning range of the pump. Efforts to find a nonlasant gas with the required absorption features and to develop a similar technique based on the photoacoustic technique will be described. This research was supported by the Office of Fusion Energy, U.S. DOE, under Contract No. DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138766
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  • 2
    Electronic Resource
    Electronic Resource
    Development of a FIR interferometer for ATF: Part I—High-power FIR laser development (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1998-1998 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A FIR interferometer system for the Advanced Toroidal Facility (ATF) at Oak Ridge National Laboratory has been developed with some major modifications to previous designs used at ORNL. Due to the highly elliptical cross section of the plasma and the projected plasma densities, a 15-channel interferometer was designed to operate at 119 μ. The large number of channels necessitated the construction of a high-power FIR laser with a fundamental mode Gaussian output over 500 mW. Also, laser stability has been significantly improved. The final design of the pump laser is modular to the extent that any single optical component can be removed and replaced without changing the optical alignment. The FIR cavity was modified by changing to a smaller bore, using gold-coated end mirrors, and using curved internal reflectors. The addition of buffer gas to the cavity provided a significant improvement in output power. Research supported by the Office of Fusion Energy, U.S. DOE, under Contract No. DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138767
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of Faraday rotation in TFTR plasmas (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1994-1996 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent results of simultaneous measurements of line electron density and poloidal field-induced Faraday rotation on the multichannel far infrared (FIR) interferometer/polarimeter on tokamak fusion test reactor (TFTR) are presented. The procedures and results of the calibration are described in detail. The effects of various errors in the measurement, as well as the problem of cross-coupling laser beams, are studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138764
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  • 4
    Electronic Resource
    Electronic Resource
    Development of a FIR interferometer for ATF: Part II—System design (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1998-1998 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Because of the highly elliptical cross section of the Advanced Toroidal Facility (ATF) plasma, a large number of interferometer channels are required to determine the radial density profile by Abel inversion. A 15-channel system is being developed using a single fan-shaped beam through the plasma and observing the phase shift across the profile with a 15-element detector array. The laser output at 119 μ will be transmitted about 10 m from the laser to the plasma device via an oversized dielectric waveguide. A surface grating will be used to redistribute the Gaussian power distribution to a sinc-type distribution. The beam will then be expanded in one dimension and focused through the plasma. It will then be combined with the local oscillator and focused on the detector array. Commercial Schottky diodes mounted in corner cube reflectors will be used as mixers. The entire system will be controlled by computer including the lasers and the data-acquisition system. Research supported by the Office of Fusion Energy, U.S. DOE, under Contract No. DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138768
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  • 5
    Electronic Resource
    Electronic Resource
    Development of sequence and regular band lasers for use as local oscillators in Thomson scattering alpha particle diagnostics (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1126-1126 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Heterodyne detection will be used to measure the scattered signal from a 100-MW pulsed CO2 laser Thomson scattered from energetic alpha particles. This measurement requires local oscillators displaced from the pump line by 6 to 21 GHz. We are developing cw sequence and regular band N2O and CO2 lasers which provide many lines in the required frequency range. The sequence lines are obtained by using a small in-cavity hot cell. Operating characteristics will be discussed for a variety of experimental arrangements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138190
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  • 6
    Electronic Resource
    Electronic Resource
    Feasibility of alpha-particle measurement by CO2 laser Thomson scattering (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1075-1077 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The feasibility of CO2 laser Thomson scattering from a multicomponent burning plasma has been evaluated for the measurement of the velocity distribution of D–T-produced alpha particles. The density and velocity distribution of the alpha particles from their initial energy of 3.5 MeV down to near-thermal energies may be measured by small-angle (〈1°) Thomson scattering. A computer simulation of the experiment indicates that a 100-MW pulsed laser combined with a bank of heterodyne receivers will be able to measure a scattered signal from the alpha particles with a postdetection signal-to-noise ratio of 75 for an assumed alpha density of 7.5×1011 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138512
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  • 7
    Electronic Resource
    Electronic Resource
    Resonance enhancement of optoacoustic signal for frequency stabilization of CO2 laser pump for CH3OH FIR laser (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 238-241 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The resonance enhancement of an optoacoustic signal, generated in methyl alcohol vapor, is investigated with the objective of obtaining a reliable discriminator at reduced pump power levels. The 9P(36) pump line from a CO2 laser is used throughout the study. The optoacoustic signal strength and resonator Q are measured at the fundamental longitudinal resonant frequency for various resonator geometries and vapor pressures. Resonators of length ranging from 12 to 24 cm are examined for tubes of inner diameter 7.5, 9.5, and 10.6 mm. The maximum vapor pressure for which a reliable discriminator is obtained is found to be 1 Torr. Both the optacoustic signal strength and the resonator Q increase with increasing vapor pressure and decreasing resonator length. The highest Q is obtained for the 10.6-mm-i.d. tubes. Using a resonator of the length 14 cm and 10.6-mm i.d. at a vapor pressure of 1 Torr, it is found that a pump power as low as 0.4 W gives a reliable discriminator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140233
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  • 8
    Electronic Resource
    Electronic Resource
    CO2 laser Thomson scattering diagnostic for fusion product alpha particle measurement (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1556-1558 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A description of a CO2 laser Thomson scattering diagnostic for fusion product alpha particles is presented. Scattering calculations based on CIT plasma parameters are presented and compared to previous work based on TFTR parameters. System components are described and a proof-of-principle test in a nonburning plasma is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140195
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  • 9
    Electronic Resource
    Electronic Resource
    Two-wavelength infrared interferometer/polarimeter system for CIT (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1629-1631 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The results of a feasibility study of a two-wavelength infrared interferometer/polarimeter system for measurements of electron density and plasma current profiles in the Compact Ignition Tokamak (CIT) are presented. The system utilizes CO2 lasers at a wavelength of 10.6 μm, and water-vapor lasers at 28 μm. Both magneto-optic and electro-optic polarization-modulation techniques have been used to determine the sensitivity and time response of the polarimetry at 10.6 μm. Measurement of a simulated plasma Faraday rotation demonstrated a sensitivity of approximately 0.01° for a CO2 laser polarimeter with an electro-optic CdTe crystal modulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140272
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  • 10
    Electronic Resource
    Electronic Resource
    Drift-wave-like density fluctuations in the Advanced Toroidal Facility (ATF) torsatron (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 398-413 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Density fluctuations in low-collisionality, low-beta (β∼0.1%), currentless plasmas produced with electron cyclotron heating (ECH) in the Advanced Toroidal Facility (ATF) torsatron [Fusion Technol. 10, 179 (1986)] have been studied using a 2 mm microwave scattering diagnostic. Pulsed gas puffing is used to produce transient steepening of the density profile from its typically flat shape; this leads to growth in the density fluctuations when the temperature and density gradients both point in the same direction in the confinement region. The wave number spectra of the fluctuations that appear during this perturbation have a maximum at higher k⊥ρs (∼1) than is typically seen in tokamaks. The in–out asymmetry of the fluctuations along the major radius correlates with the distribution of confined trapped particles expected for the ATF magnetic field geometry. During the perturbation, the relative level of the density fluctuations in the confinement region (integrated over normalized minor radii ρ from 0.5 to 0.85) increases from ñ/n∼1% when the density profile is flat to ñ/n∼3% when the density profile is steepened. These observations are in qualitative agreement with theoretical expectations for helical dissipative trapped-electron modes (DTEMs), which are drift-wave instabilities associated with particle trapping in the helical stellarator field; they suggest that trapped-electron instabilities may play a role in constraining the shape of the density profile in ATF, but have little effect on global energy confinement. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870966
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