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  • 1
    Electronic Resource
    Electronic Resource
    Infrared imaging video bolometer (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3696-3701 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new concept for an infrared imaging bolometer is proposed which provides full video (two-dimensional) imaging of the radiated power from the plasma. This concept preserves all the advantages (compared to conventional metal foil resistive bolometers) of the previously proposed and tested segmented mask infrared imaging bolometer (SIB). It avoids the problems associated with the copper mask of the SIB, while giving a full frame video image of the plasma radiation with improved experimental flexibility regarding the pixel size. Analysis of the noise equivalent power shows that compared to a SIB with the same pixel area, the infrared imaging video bolometer is 2–5 times more sensitive with improved spatial resolution. These benefits are gained at the expense of the mechanical support, which the mask provides for the foil in the SIB. A numerical algorithm is used to solve the two-dimensional heat diffusion equation for the foil and determine the time-dependent spatial distribution of incident power on the foil from the infrared (IR) video camera measurements of the foil temperature. Testing the algorithm using a Gaussian model of the incident power shows that it can accurately reproduce the Gaussian model to within 6%. A simple scheme to absolutely calibrate the entire foil is described and several design points are detailed pointing out the range and experimental flexibility of the diagnostic using currently available IR camera technology. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290044
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  • 2
    Electronic Resource
    Electronic Resource
    Aquatic Primary Productivity and the 14C-CO2 Method: A History of the Productivity Problem (1980)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 11 (1980), S. 359-385 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.es.11.110180.002043
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  • 3
    Electronic Resource
    Electronic Resource
    Stable Isotopes in Ecosystem Studies (1987)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 18 (1987), S. 293-320 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.es.18.110187.001453
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  • 4
    Electronic Resource
    Electronic Resource
    Inter-biome comparison of factors controlling stream metabolism (2001)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We studied whole-ecosystem metabolism in eight streams from several biomes in North America to identify controls on the rate of stream metabolism over a large geographic range. The streams studied had climates ranging from tropical to cool-temperate and from humid to arid and were all relatively uninfluenced by human disturbances.2. Rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) were determined using the open-system, two-station diurnal oxygen change method.3. Three general patterns in metabolism were evident among streams: (1) relatively high GPP with positive NEP (i.e. net oxygen production) in early afternoon, (2) moderate primary production with a distinct peak in GPP during daylight but negative NEP at all times and (3) little or no evidence of GPP during daylight and a relatively constant and negative NEP over the entire day.4. Gross primary production was most strongly correlated with photosynthetically active radiation (PAR). A multiple regression model that included log PAR and stream water soluble reactive phosphorus (SRP) concentration explained 90% of the variation in log GPP.5. Ecosystem respiration was significantly correlated with SRP concentration and size of the transient storage zone and, together, these factors explained 73% of the variation in R. The rate of R was poorly correlated with the rate of GPP.6. Net ecosystem production was significantly correlated only with PAR, with 53% of the variation in log NEP explained by log PAR. Only Sycamore Creek, a desert stream in Arizona, had positive NEP (GPP: R 〉 1), supporting the idea that streams are generally net sinks rather than net sources of organic matter.7. Our results suggest that light, phosphorus concentration and channel hydraulics are important controls on the rate of ecosystem metabolism in streams over very extensive geographic areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00773.x
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  • 5
    Electronic Resource
    Electronic Resource
    Multifaceted asymmetric radiation from the edge-like asymmetric radiative collapse of density limited plasmas in the Large Helical Device (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3861-3864 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutral beam injection heated discharges at the density limit in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)] are terminated with asymmetric radiative collapse (ARC) exhibiting several properties in common with the MARFE (multifaceted asymmetric radiation from the edge) phenomenon: (1) A highly poloidally asymmetric radiation profile which is stronger on the inboard side. (2) This asymmetry is well correlated with the signal from the multichord interferometer. (3) Moreover, evidence from several diagnostics at different toroidal locations supports the possibility that ARC may be toroidally symmetric. However in contrast to MARFE, ARC is only observed in the period just prior to the quench of the plasma. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1390330
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  • 6
    Electronic Resource
    Electronic Resource
    Initial long-pulse plasma heating at reduced power with negative-ion-based neutral beam injector in large helical device (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4260-4265 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have achieved long-pulse plasma heating using a negative-ion-based neutral beam injector (NBI) in the large helical device (LHD), where the confinement magnetic field is generated by only external superconducting coils. In the initial long-pulse experiments at lower power than that in short-pulse experiments, 80 keV–1.1 MW NBI heating lasted for 10 s with a little increase in the plasma density at the pulse end. Almost steady-state plasma heating was achieved for 21 s with 66 keV–0.6 MW NB injection. Plasma relaxation oscillation phenomena at a period of 1–2 s were also observed for 20 s. Above 1 keV plasma was easily sustained with a long-pulse NBI heating in LHD, without the current drive nor the disruption in tokamaks. Negative ion source operation was stable and the cooling water temperature rise of beam accelerator grids was nearly saturated with a temperature rise below 10 °C. For a higher power injection, the pulse duration is determined by the beam blocking, where the reionization loss is exponentially increased together with an increase in outgas in the injection port. The port conditioning by a careful repetition of injection is effective to the extension of the injection duration and the plasma maintenance duration. The initial long-pulse NBI heating at the reduced power has demonstrated an ability of steady-state operation in superconducting LHD. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150063
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  • 7
    Electronic Resource
    Electronic Resource
    Development of imaging bolometers for long-pulse MFE experiments (invited) : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 255-259 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed the concept of an imaging bolometer, capable of operation with 100's of individual channels, while relying on optical (infrared) readout of the temperature rise in a thin foil. A thin gold foil (0.5–5 μm thick) is sandwiched between pieces of copper. The copper mask (a large thermal mass) has a hole pattern drilled into it to form many "individual pixels," effectively forming many separate sensors. This segmented foil/mask combination is exposed on its front side to plasma radiation through a cooled pinhole camera geometry. Simultaneously, a high-resolution infrared camera monitors any temperature change on the backside of the thin foil. A sensitive infrared (IR) camera views the foil through an IR telescope/periscope system, and is shielded from the magnetic and nuclear radiation fields, either by distance and/or material shielding. A simple time-dependent design algorithm, using 1D heat transport to a cold boundary, has been written in MathCad, which allows us to select optimal material and geometries to match the expected plasma conditions. We have built a compact prototype with 149 channels, and tested it successfully both in a vacuum test stand in the laboratory, and on a plasma in the CHS at the National Institute for Fusion Science, subjecting it to electron cyclotron heated and neutral beam injection heated conditions. A water-cooled version has been built for the new LHD. Since the IR imaging bolometer uses only metal parts near the plasma, and has no need for wiring or wiring feedthrus, it is intrinsically radiation hard, and has direct application to ignition device to test engineering concepts (ITER), or ITER-class experiments. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149441
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of ion flows using an "unmagnetized'' Mach probe in the interchangeable module stellarator (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2599-2606 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Mach probe is used to measure poloidal and toroidal flows induced by a biased electrode in IMS. Mach probe theories are reviewed and classified as either magnetized or unmagnetized. A simple geometric model of the IMS Mach probe shows that the variation of the effective probe area as a function of the probe orientation with respect to the magnetic field is 20%–25%, predicting the probe to be only slightly magnetized. Measurements of the variation in the total ion saturation current collected by the probe, as the angle with respect to the magnetic field is varied, demonstrate this level of magnetization only at low neutral pressure at large minor radius, while in other cases the variation in the total collected current is negligible. Based on this result an unmagnetized model [M. Hudis and L. M. Lidsky, J. Appl. Phys. 41, 5011 (1970)] is chosen to analyze the IMS Mach probe data. Comparison of Mach probe poloidal flow measurements as a function of minor radius to calculations of the E×B drift velocity and the ion diamagnetic drift velocity from radial profiles of floating potential and ion saturation current, respectively, shows agreement to within 15%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144658
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  • 9
    Electronic Resource
    Electronic Resource
    Overview of large helical device diagnostics (invited) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 483-491 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Large Helical Device (LHD) is the largest helical machine with superconducting coils. Key diagnostics issues for LHD are: (a) capability for multidimensional measurements because of the nonaxisymmetric toroidal plasma; (b) measurements of the electric field; (c) cross check of fundamental parameters using different methods; (d) advanced measurements appropriate for steady-state operation; and (e) a satisfactory data acquisition system. The design and research and development of plasma diagnostics were carried out taking these issues into consideration. As a result, the present status of diagnostics is described: diagnostics for LHD operation, fundamental diagnostics for plasma performance, diagnostics for physics subjects, innovative diagnostics and diagnostics for long-pulse operation. The LHD experiment started in March, 1998. Since then, the development of diagnostics has kept pace with the experimental campaigns. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310581
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  • 10
    Electronic Resource
    Electronic Resource
    Infrared imaging video bolometer for the large helical device : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 923-926 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of infrared imaging bolometer, known as the infrared imaging video bolometer (IRVB) has been under development at the National Institute of Fusion Science (NIFS) over the last year. A prototype of this diagnostic has been designed and constructed at NIFS and installed on the large helical device (LHD) and successfully operated. This diagnostic utilizes a 66×90×0.001 mm gold foil mounted in a frame to detect the radiation and neutrals from the plasma which are incident on the foil through a 1 cm diameter pinhole. The resulting temperature distribution on the foil is measured using an AGEMA THV 900 LW infrared camera having 136×272 pixels with a frame rate of 15 Hz and a nominal sensitivity of 80 mK. An image of the foil and surrounding frame consisting of 120×160 pixels is resampled down to 12×16 pixels using a linear interpolation scheme. Using a numerical technique the spatial and temporal derivatives of the temperature distribution on the foil are calculated and the incident power density on the foil is determined using a calibration of the foil obtained by means of a HeNe laser. The resulting 10×14 pixel view of the plasma radiation at a 15 Hz frame rate has a noise equivalent power density of 0.5 mW/cm2. The IRVB was mounted on a LHD tangential port for the 1999 campaign. An image of the plasma radiation during a discharge using the inboard vacuum vessel wall as a limiter shows radiation localized near the limiting surface. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319597
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