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The Measurement Of Absolute Helium Ion Density Profiles On The Diii D Tokamak Using Charge Exchange Recombination Spectroscopy
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Book Synopsis The Measurement of Absolute Helium Ion Density Profiles on the DIII-D Tokamak Using Charge Exchange Recombination Spectroscopy by : Daniel Franklin Finkenthal
Download or read book The Measurement of Absolute Helium Ion Density Profiles on the DIII-D Tokamak Using Charge Exchange Recombination Spectroscopy written by Daniel Franklin Finkenthal and published by . This book was released on 1994 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helium Transport and Exhaust Studies of H-mode Discharges in the DIII-D Tokamak by :
Download or read book Helium Transport and Exhaust Studies of H-mode Discharges in the DIII-D Tokamak written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A collaborative program has been initiated to measure helium (He) transport and exhaust on DIII-D in L-mode, ELM-free H-mode, and ELMing H-mode. These diverted plasmas operating in enhanced confinement regimes should provide valuable information for the International Thermonuclear Experimental Reactor (ITER). To simulate the presence of He ash in DIII-D, a 50 ms He puff is injected into a DIII-D plasma, resulting in a He concentration of [approximately] 15%. The time dependence of the He density profiles in the plasma core is measured with charge-exchange recombination spectroscopy and the He spatial distribution on the diverter floor is studied with an impurity monitor array. The dependence of core transport diffusivities as a function of ELM frequency have been studied and the first demonstration made of He exhaust from an H-mode plasma in a diverted tokamak. The exhaust rate of He from these ELMing H-mode plasmas appears to be within the acceptable range for a fusion reactor, like ITER, based on a measured value of [tau]*[sub He]/[tau]E [approx]14.
Book Synopsis Helium Charge Exchange Recombination Spectoscopy on Alcator C-Mod Tokamak by : Kenneth Teh-Yong Liao
Download or read book Helium Charge Exchange Recombination Spectoscopy on Alcator C-Mod Tokamak written by Kenneth Teh-Yong Liao and published by . This book was released on 2014 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Wide-View Charge Exchange Recombination Spectroscopy (CXRS) diagnostic at Alcator C-Mod, originally designed for measurement of boron, has been modified to fit several different roles. By measuring the He1+ (n = 4 [rightwards arrow] 3) emission line at 4686Å and surrounding spectra, we can measure 4He and 3He density, temperature, and velocity profiles and use this information to study turbulent impurity transport. The transport is characterized using a standard ansatz for the radial particle flux: [mathematical equation]. This effort is designated He CXRS. Also, direct measurement of 3He are used to test models of Ion Cyclotron Resonance Heating (ICRH). We look for evidence of fast ion production and the effect of the minority ion profile on fast wave heating. Several modifications were made to the hardware. Light is collected via two optical arrays: poloidal and toroidal. The toroidal array has been upgraded to increase throughput and spatial resolution, increasing the number of toroidal channels from 10 to 22. A new protective shroud was installed on the poloidal array. Additional diagnostics (a 11 channel beam duct view, neutralizer view, duct pressure monitor) were added to the Diagnostic Neutral Beam to improve DNB modeling for CXRS. This work includes investigation of plasmas where helium is at low concentration (1%), acting passively, as well as scenarios with a large fraction (~20%). Using the STRAHL code, time-dependent helium density profiles are used to obtain anomalous transport parameters. Thermodiffusion and curvature pinch terms are also estimated from experimental scaling studies. Results are compared with neoclassical results from the NCLASS code and calculations by the GENE gyrokinetic code. Another focus is verification of power deposition models which are crucially dependent on minority ion density, for which 3He is used. At low 3He fraction, direct absorption by 3He generates fast ions with anisotropic velocity-space distribution functions. At high 3He fraction, mode conversion heating of electrons is dominant. The minority distribution function and predicted wave deposition are simulated using AORSA and CQL3D. This work provides the first measurements of helium transport on C-Mod and expands our understanding of helium transport and fast wave heating.
Book Synopsis Helium Transport in Enhanced Confinement Regimes on the TEXTOR and DIII-D Tokamaks by :
Download or read book Helium Transport in Enhanced Confinement Regimes on the TEXTOR and DIII-D Tokamaks written by and published by . This book was released on 1992 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparisons of helium (He) transport and exhaust in L-mode and in an enhanced confinement regime (H-mode), which is induced by a polarizing electrode, have been made for the TEXTOR tokamak. The results show an increased tendency for He accumulation when bulk plasma energy and particle confinement are improved during the polarization induced H-mode. Since these results imply that a high He pumping efficiency may be necessary for H-mode burning plasmas, we have begun exploring He transport in a divertor H-mode, similar to that proposed for International Thermonuclear Experimental Reactor (ITER). A collaborative program has been initiated to measure He transport and scaling on DIII-D during L-mode, H-mode, and ELMing H-mode plasma conditions. To simulate the presence of He ash in DIII-D, a 25 ms He puff is injected into a DIII-D plasma resulting in a He concentration of (almost equal to)5%. The time dependence of the He{sup 2+} density profiles in the plasma core is measured by charge-exchange recombination spectroscopy at 11 radial locations.
Book Synopsis American Doctoral Dissertations by :
Download or read book American Doctoral Dissertations written by and published by . This book was released on 1994 with total page 800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1993 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Doppler Measurements in the Edge of the Alcator C-Mod Tokamak Using a High-resolution Visible Spectrometer by : Alexander Turner Graf
Download or read book Doppler Measurements in the Edge of the Alcator C-Mod Tokamak Using a High-resolution Visible Spectrometer written by Alexander Turner Graf and published by . This book was released on 2008 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Charge Exchange Recombination Diagnostic System on the DIII-D Tokamak by :
Download or read book The Charge Exchange Recombination Diagnostic System on the DIII-D Tokamak written by and published by . This book was released on 1991 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The charge exchange recombination (CER) diagnostic system on the DIII-D tokamak is used to make spatially and temporally resolved measurements of the ion temperature and toroidal and poloidal rotation velocities. This is performed through visible spectroscopic measurements of the Doppler broadened and Doppler shifted HE II 468.6 nm, the CVI 529.1 nm, and the BV 494.5 nm spectral lines which have been excited by charge exchange recombination interactions between the fully stripped ions and the neutral atoms from the heating beams. The plasma viewing optics comprises 32 viewing chords spanning a typical plasma minor radius of 63 cm across the midplane, of which 15 spatial chords span 4.2 cm at the plasma edge just within the separatrix and provide a chord-to-chord spatial resolution of 0.3 cm. Fast camera readout electronics can provide a temporal resolution of 260 [mu]s per time slice, but the effective minimum integration time, at present, is 1 ms which is limited by the detected photon flux from the plasma and the decay times of the phosphors used on the multichannel plate image intensifiers. Significant changes in the edge plasma radial electric field at the L-H transition have been observed, as determined from the CER measurements, and these results are being extensively compared to theories which consider the effects of sheared electric fields on plasma turbulence. 13 refs., 10 figs.
Book Synopsis Helium Transport Studies on DIII-D. by :
Download or read book Helium Transport Studies on DIII-D. written by and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The measurement of Helium density profiles in tokamak plasmas is necessary for helium transport studies. These studies are important in predicting the helium ash transport properties for ITER and win have important implications for the design. Poor helium transport in reactors could lead to a buildup of fusion ash, causing fuel dilution and increased radiation that will result in degraded fusion power and possibly quench ignition altogether. Present estimates indicate that He concentrations in the core must be kept below 10% in order to maintain continuous reactor operation. Helium transport studies have begun on the DM-D tokamak using charge exchange recombination (CER) spectroscopy for helium density measurements. Helium transport behavior has been observed by injecting helium gas puffs into DM-D plasmas and measuring the He density profile evolution. The profiles are used to calculate the relevant helium transport properties. This paper covers the results obtained from puffing He gas into L-mode plasmas of various electron densities. The results obtained in DIII-D L-mode plasmas are similar to measurements made at TEXTOR and JT-60.
Book Synopsis Velocity-space Resolved Fast-ion Measurements in the DIII-D Tokamak by : Christopher Michael Muscatello
Download or read book Velocity-space Resolved Fast-ion Measurements in the DIII-D Tokamak written by Christopher Michael Muscatello and published by . This book was released on 2012 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superthermal ions in tokamak plasmas play a critical role in heating and current drive, and their confinement within the core of the plasma is crucial for obtaining ignition and sustaining burn in future reactors. At the DIII-D tokamak, a suite of fast-ion measurements is available to diagnose various properties of the superthermal population. This thesis work involves a contribution to DIII-D's fast-ion diagnostic collection: the 2nd generation fast-ion deuterium alpha (2G FIDA) detector. FIDA works on the principle of measuring the light that is emitted from neutralized fast ions that undergo charge exchange events with injected neutral atoms. 2G FIDA complements the other FIDA installations on DIII-D with its unique velocity-space sampling volume. Output from a synthetic diagnostic code (FIDAsim) that predicts FIDA emission levels is compared with measurements from 2G FIDA. We find that, while the predicted and measured shapes of the FIDA spectra agree well, the absolute magnitude of the spectral amplitudes are inconsistent. Results from various FIDAsim trials are presented adjusting several parameters, and it is hypothesized that mischaracterization of the diagnostic neutral beams is a major source of error. Instabilities in tokamaks can cause fast-ion transport. The sawtooth instability is particularly important because the crash phase has been observed to cause reductions up to 50% in the central fast-ion density. Passing ions of all energies are redistributed, but only low energy trapped ions suffer redistribution. The observations are consistent with transport by flux-attachment. Comparisons with theory suggest that the intensity of sawtooth-induced transport depends on the magnitude of toroidal drift. Instabilities characterized by toroidal and poloidal mode numbers and real frequency can coherently interact with energetic particles through mode-particle resonances. During a sawtooth crash, even fast ions whose energies are above the threshold for flux-attachment can experience transport if their orbits satisfy the bounce-precessional resonance condition. On DIII-D, a spatially localized population of beam ions accelerated above the injection energy by ion-cyclotron radio frequency (ICRF) heating is diminished at a sawtooth crash. Furthermore, fast-ion losses concurrent with sawtooth crashes are observed. Calculations show that mode-particle resonances could be responsible. Transport of energetic particles by resonant interactions pertains to many types of instabilities; other examples besides sawteeth will also be presented. Analysis shows that large amplitude modes cause significant resonant transport of fast particles. Even small amplitude modes can resonantly drive transport if multiple harmonics exist.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Sepculum Monachorum a Dacryano ordinis S. Benedicti abbate conscriptum, antehac nusquam excusum by :
Download or read book Sepculum Monachorum a Dacryano ordinis S. Benedicti abbate conscriptum, antehac nusquam excusum written by and published by . This book was released on 1538 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Plasma Rotation and the Radial Electric Field During Off-axis NBI in the DIII-D Tokamak by :
Download or read book Plasma Rotation and the Radial Electric Field During Off-axis NBI in the DIII-D Tokamak written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments have been carried out on the DIII-D tokamak to investigate whether off-axis NBI can: (a) drive significant perpendicular flow to lead to increased suppression of turbulence and improved confinement, and (b) be used to control the radial electric field profile. Measurements of both impurity ion poloidal and toroidal rotation profiles were made using charge exchange recombination spectroscopy. These experiments used a low current, low elongation (I[sub p]= 0.5 MA, [kappa]= 1.2) plasma whose magnetic axis was shifted 36 cm vertically upward from the vessel midplane and then shifted downward to be centered on the midplane later in the discharge. 10.7 MW of beam power was applied to maximize NBI effect while operating at low target densities and high temperature to minimize poloidal damping. Results from these experiments show a slight increase in impurity ion poloidal rotation velocity during the vertical shifted phase of off-axis NBI discharge. The toroidal rotation profile is more peaked during off-axis NBI. Both these effects lead to a change in the V x B contribution to the radial electric field during off-axis NBI.
Book Synopsis Experimental Tests of the Theory of Poloidal Rotation in the DIII-D Tokamak by : Colin Chrystal
Download or read book Experimental Tests of the Theory of Poloidal Rotation in the DIII-D Tokamak written by Colin Chrystal and published by . This book was released on 2014 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this dissertation was to develop a novel technique for measuring ion poloidal rotation and then using that technique to test poloidal rotation theories. The new poloidal rotation diagnostic has been developed on the DIII-D tokamak. This diagnostic uses charge exchange recombination spectroscopy to measure toroidal rotation on the high- and low-field side of the tokamak midplane to determine the poloidal rotation from a divergence-free description of flow within flux-surfaces. Measurements are made such that no atomic physics calculations are needed to account for the energy dependence of the charge exchange cross section. New techniques for creating magnetic equilibrium reconstructions and performing the spatial calibration have been developed to ensure the accuracy of this new diagnostic. Measurements are made in the core of DIII-D where the spatial resolution is significantly improved when compared to the direct measurement of the poloidal rotation. This diagnostic has been used to investigate impurity poloidal rotation in the core of a variety of plasmas. For the first time on DIII-D, mean poloidal flow spin-up coincident with the formation of an internal transport barrier has been observed. The various measurements of poloidal rotation have been compared with theoretical predictions. Disagreement with neoclassical calculations have been found in H-mode, QH-mode, and the core of internal transport barrier plasmas. The effect of turbulent driven Reynolds stress and fast-ion friction have been investigated as well, and it has been determined that either of these effects, on their own, is insufficient to explain the discrepancy with neoclassical predictions. Modeling results indicate that these effects that are not included in standard neoclassical calculations are important for calculating the poloidal rotation.
Book Synopsis Plasma Physics and Controlled Nuclear Fusion Research by :
Download or read book Plasma Physics and Controlled Nuclear Fusion Research written by and published by . This book was released on 1992 with total page 808 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Role of the Radial Electric Field in Confinement and Transport in H-mode and VH-mode Discharges in the DIII-D Tokamak by :
Download or read book The Role of the Radial Electric Field in Confinement and Transport in H-mode and VH-mode Discharges in the DIII-D Tokamak written by and published by . This book was released on 1993 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of the radial electric field, E{sub r}, with high spatial and high time resolution in H-mode and VH-mode discharges in the DIII-D tokamak have revealed the significant influence of the shear in E{sub r} on confinement and transport in these discharges. These measurements are made using the DIII-D Charge Exchange Recombination (CER) System. At the L-H transition in DIII-D plasmas, a negative well-like E{sub r} profile develops just within the magnetic separatrix. A region of shear in E{sub r} results, which extends 1 to 2 cm into the plasma from the separatrix. At the transition, this region of sheared E{sub r} exhibits the greatest increase in impurity ion poloidal rotation velocity and the greatest reduction in plasma fluctuations. A transport barrier is formed in this same region of E x B velocity shear as is signified by large increases in the observed gradients of the ion temperature, the carbon density, the electron temperature and electron density. The development of the region of sheared E{sub r}, the increase in impurity ion poloidal rotation, the reduction in plasma turbulence, and the transport barrier all occur simultaneously at the L-H transition. Measurements of the radial electric field, plasma turbulence, thermal transport, and energy confinement have been performed for a wide range of plasma conditions and configurations. The results support the supposition that the progression of improving confinement at the L-H transition, into the H-mode and then into the VH-mode can be explained by the hypothesis of the suppression of plasma turbulence by the increasing penetration of the region of sheared E x B velocity into the plasma interior.
Book Synopsis Measurement and Simulation of Deuterium Balmer-alpha Emission from First-orbit Fast Ions and the Application to Neutral Density and General Fast-ion Loss Detection in the DIII-D Tokamak by : Nathan Glynn Bolte
Download or read book Measurement and Simulation of Deuterium Balmer-alpha Emission from First-orbit Fast Ions and the Application to Neutral Density and General Fast-ion Loss Detection in the DIII-D Tokamak written by Nathan Glynn Bolte and published by . This book was released on 2015 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectra of the Balmer-alpha radiation of first-orbit fast ions after charge exchange with edge neutrals have been measured in the DIII-D tokamak. Several collimated optics systems view the edge region--while avoiding any active beams--and carry light to a spectrometer tuned to the region of the 656.1 nm deuterium-alpha line. Viewing geometry and the high energy of the lost ions produce Doppler shifts, which effectively separate the fast-ion contributions from the bright, cold edge light. Modulation of the fast-ion source allows for time-evolving background subtraction. A model has been developed for the spectra of these first-orbit fast ions. The passive fast-ion D-alpha simulation (P-FIDAsim) is a forward model consisting of an experimentally- validated beam model, an ion orbit-following code, a collisional-radiative model, and a synthetic spectrometer. Eighty-six experimental spectra were obtained using 6 different neutral beam fast-ion sources and 13 different viewing chords. Parameters such as plasma current, toroidal field, electron density, plasma cross-sectional shape, and number of x-points were varied. Uncalibrated experimental spectra have an overall Spearman rank correlation coefficient with the shape of simulated spectra of 0.58 with subsets of cases rising to a correlation of 0.80. A single set of calibrated spectra (shot 152817) was measured and is used to estimate the neutral density throughout the cross-section of the tokamak. This is done by inverting the simulated spectra in order to nd the best neutral density (in a least squares sense) required to best match the experimental spectra. The resulting 2D neutral density shows the expected increase toward each x-point. The average neutral density is found to be 3.3 x 105 cm ̄3 at the magnetic axis, 2.3 x 108 cm ̄3 in the core, 8.1 x 109 cm ̄3 at the plasma boundary, and 1.1 x 1011 cm ̄3 near the wall. A technique is developed which--after using first-orbit light to calibrate the system--can quantify losses from a wider variety of mechanisms. Fast-ion losses resulting from sawtooth crashes (shot 149941) is estimated to eject 1.2% of the fast-ion inventory, in good agreement with a 1.7% loss estimate made by the TRANSP code.
