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Ramp-up of CHI Initiated Plasmas on NSTX

Description: Experiments on the National Spherical Torus (NSTX) have now demonstrated flux savings using transient coaxial helicity injection (CHI). In these discharges, the discharges initiated by CHI are ramped up with an inductive transformer and exhibit higher plasma current than discharges without the benefit of CHI initiation.
Date: October 29, 2009
Creator: Mueller, D.; Bell, R. E.; LeBlanc, B.; Roquemore, A. L.; Raman, R.; Jarboe, T. R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Three-dimensional Reconstruction of Dust Particle Trajectories in the NSTX

Description: Highly mobile incandescent dust particles are routinely observed on NSTX using two fast cameras operating in the visible region. An analysis method to reconstruct dust particle trajectories in space using two fast cameras is presented in this paper. Position accuracies of a few millimeters depending on the particle's location have been achieved and particle velocities between 10 and 200 m/s have been observed. 2008 American Institute of Physics. __________________________________________________ more
Date: March 6, 2009
Creator: Boeglin, W. U.; Roquemore, A. L. & Maqueda, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Edge Recycling and Heat Fluxes in L- and H-mode NSTX Plasmas

Description: Introduction Edge characterization experiments have been conducted in NSTX to provide an initial survey of the edge particle and heat fluxes and their scaling with input power and electron density. The experiments also provided a database of conditions for the analyses of the NSTX global particle sources, core fueling, and divertor operating regimes.
Date: August 5, 2003
Creator: Soukhanovskii, V. A.; Maingi, R.; Raman, R.; Kugel, H.; LeBlanc, B.; Roquemore, A. L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Confinement of Neutral Beam Ions in the National Spherical Torus Experiment

Description: The loss of neutral-beam ions to the wall has been measured in the National Spherical Torus Experiment (NSTX) by means of thermocouples, an infrared (IR) camera, and a Faraday cup probe. The losses tend to exhibit the expected dependences on plasma current, tangency radius of the injector, and plasma outer gap. However, the thermocouples and the Faraday cups indicate substantially different levels of loss and this difference has yet to be understood.
Date: December 18, 2001
Creator: Darrow, D. S.; Medley, S. S.; Roquemore, A. L. & Rosenberg, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Diagnostic Development on NSTX

Description: Diagnostics are described which are currently installed or under active development for the newly commissioned NSTX device. The low aspect ratio (R/a less than or equal to 1.3) and low toroidal field (0.1-0.3T) used in this device dictate adaptations in many standard diagnostic techniques. Technical summaries of each diagnostic are given, and adaptations, where significant, are highlighted.
Date: December 16, 1999
Creator: Roquemore, A.L.; Johnson, D.; Kaita, R. & al, et
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The H-mode Pedestal and Edge Localized Modes in NSTX

Description: The research program of the National Spherical Torus Experiment (NSTX) routinely utilizes the H-mode confinement regime to test and extend beta and pulse length limits. As in conventional aspect ratio tokamaks, NSTX observes a variety of edge localized modes (ELMs) in H-mode. Hence a significant part of the research program is dedicated to ELMs studies.
Date: July 16, 2004
Creator: Maingi, R.; Fredrickson, E. D.; Menard, J. E.; Nishino, N.; Roquemore, A. L.; Sabbagh, S. A. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neutral Particle Analyzer Diagnostic on NSTX

Description: The Neutral Particle Analyzer (NPA) diagnostic on the National Spherical Torus Experiment (NSTX) utilizes a PPPL-designed E||B spectrometer that measures the energy spectra of minority hydrogen and bulk deuterium species simultaneously with 39 energy channels per mass specie and a time resolution of 1 ms. The calibrated energy range is E = 0.5-150 keV and the energy resolution varies from AE/E = 3-7% over the surface of the microchannel plate detector.
Date: March 16, 2004
Creator: Medley, S. S. & Roquemore, A. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The TFTR E Parallel B Spectrometer for Mass and Energy Resolved Multi-Ion Charge Exchange Diagnostics

Description: The Charge Exchange Neutral Analyzer diagnostic for the Tokamak Fusion Test Reactor was designed to measure the energy distributions of both the thermal ions and the supra thermal populations arising from neutral-beam injection and ion cyclotron radio-frequency heating. These measurements yield the plasma ion temperature, as well as several other plasma parameters necessary to provide an understanding of the plasma condition and the performance of the auxiliary heating methods. For this applica… more
Date: January 1, 1998
Creator: Roquemore, A. L. & Medley, S. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Precision metrology of NSTX surfaces using coherent laser radar ranging

Description: A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 {micro}m laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100{micro}m at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and … more
Date: July 13, 2000
Creator: Kugel, H.W.; Loesser, D.; Roquemore, A. L.; Menon, M. M. & Barry, R. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Local scrape-off layer control using biased electrodes in NSTX

Description: An experiment was designed to test the theory that biased electrodes can affect the local scrape-off layer (SOL) width by creating a strong radial ExB drift [Cohen, R.H. and Ryutov, D.D, Nucl. Fusion 37, 621 (1997)]. These electrodes were located near the outer midplane in the SOL of the National Spherical Torus Experiment (NSTX). The electrodes were biased at up to �100 Volts, and the radial profile of the plasma between them was measured by an array of Langmuir probes. The biasing caused larg… more
Date: April 24, 2009
Creator: Zweben, S. J.; Maqueda, R. J.; Roquemore, A. L.; Bush, C. E.; Kaita, R.; Marsala, R. J. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Large Aperture Electrostatic Dust Detector

Description: Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ν has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particle… more
Date: October 9, 2007
Creator: Skinner, C. H.; Hensley, R. & Roquemore, A. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Objectives and Layout of a High-Resolution X-ray Imaging Crystal Spectrometer for the Large Helical Device (LHD)

Description: A high-resolution X-ray imaging crystal spectrometer, whose concept was tested on NSTX and Alcator C-Mod, is being designed for LHD. This instrument will record spatially resolved spectra of helium-like Ar16+ and provide ion temperature profiles with spatial and temporal resolutions of < 2 cm and ≥ 10 ms. The stellarator equilibrium reconstruction codes, STELLOPT and PIES, will be used for the tomographic inversion of the spectral data. The spectrometer layout and instrumental features are l… more
Date: July 29, 2010
Creator: Bitter, M.; Gates, D.; Monticello, D.; Neilson, H.; Reiman, A.; Roquemore, A. L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neutral Particle Analyzer Measurements of Ion Behavior in NSTX

Description: Initial results obtained with the Neutral Particle Analyzer (NPA) diagnostic on the National Spherical Torus Experiment (NSTX) are presented. Magnetohydrodynamic activity and reconnection events cause depletion of the deuterium energetic ion distribution created by neutral-beam injection. Adding High Harmonic Fast Wave Heating to neutral-beam-heated discharges results in the generation of an energetic ion tail above the beam injection energy. NPA measurements of the residual hydrogen ion temper… more
Date: February 6, 2002
Creator: Medley, S. S.; Bell, R. E.; Darrow, D. S. & Roquemore, A. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neutral Beam Ion Confinement in NSTX

Description: Neutral-beam (NB) heating in the National Spherical Torus Experiment (NSTX) began in September 2000 using up to 5 MW of 80 keV deuterium (D) beams. An initial assessment of beam ion confinement has been made using neutron detectors, a neutral particle analyzer (NPA), and a Faraday cup beam ion loss probe. Preliminary neutron results indicate that confinement may be roughly classical in quiescent discharges, but the probe measurements do not match a classical loss model. MHD activity, especially… more
Date: July 24, 2001
Creator: Darrow, D. S.; Fredrickson, E. D.; Kaye, S. M.; Medley, S. S. & Roquemore, A. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Infrared Camera Diagnostic for Heat Flux Measurements on NSTX

Description: An infrared imaging system has been installed on NSTX (National Spherical Torus Experiment) at the Princeton Plasma Physics Laboratory to measure the surface temperatures on the lower divertor and center stack. The imaging system is based on an Indigo Alpha 160 x 128 microbolometer camera with 12 bits/pixel operating in the 7-13 {micro}m range with a 30 Hz frame rate and a dynamic temperature range of 0-700 degrees C. From these data and knowledge of graphite thermal properties, the heat flux i… more
Date: March 25, 2003
Creator: Mastrovito, D.; Maingi, R.; Kugel, H. W. & Roquemore, A. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Characteristics of solid-target charge-exchange analyzers for energetic ion diagnostics on tokamaks

Description: Compact electrostatic charge-exchange analyzers have been constructed for installation in areas of high magnetic fields and restricted access near tokamak fusion devices. The analyzers employed carbon stripping foils, and have been calibrated for proton energies between 1 and 70 keV. They have been successfully used to study charge-exchange losses in auxiliary-heated tokamak plasmas.
Date: May 1, 1987
Creator: Beiersdorfer, P.; Roquemore, A.L. & Kaita, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Analysis of High-Te Plasmas Heated by HHFW in NSTX

Description: The implementation in TRANSP of a recent version of TORIC capable of calculating power deposition for HHFW conditions is used to analyze NSTX plasma under different operating conditions. The power deposition profile into the electrons is obtained for high-Te conditions - Te ≤ 5keV - obtained in He and D plasmas with ITB. HHFW heating of NBI-induced H-mode plasmas is discussed. At the RF onset the RF power is divided evenly between the electrons and the fast particles, but as the latter thermali… more
Date: June 26, 2009
Creator: LeBlanc, P.; Bell, R. E.; Bonoli, P.; Hosea, J. C.; Mazzucato, E.; Phillips, C. K. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Charge exchange stripping cell measurements over a wide pressure range

Description: The efficiency of the stripping cell incorporated in a charge exchange analyzer has been measured over a pressure range of 1.8 to 130 mtorr and over an energy range of 1 to 130 keV/amu. In these measurements, a beam of hydrogen atoms was ionized by helium gas. As a by-product of the measurements, the scattering cross section was also measured. At the lowest pressure, the scattering cross section compared well with those measured previously; at high pressure, the cross section no longer followed… more
Date: January 1, 1988
Creator: Colchin, R. J.; Roquemore, A. L. & Scott, S. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Prompt Loss of Energetic Ions during Early Neutral Beam Injection in the National Spherical Torus Experiment

Description: Early neutral-beam injection is used in the National Spherical Torus Experiment (NSTX) to heat the electrons and slow current penetration which keeps q(0) elevated to avoid deleterious MHD activity and at the same time reduces Ohmic flux consumption, all of which aids long-pulse operation. However, the low plasma current (I{sub p} {approx} 0.5 MA) and electron density (n{sub e} {approx} 1 x 10{sup 13} cm{sup -3}) attending early injection lead to elevated orbit and shine through losses. The inh… more
Date: March 25, 2005
Creator: Medley, S. S.; Darrow, D. S.; Liu, D. & Roquemore, A. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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