Download or read book Impurity Transport in the Divertor of the Alcator C Mod Tokamak written by G. M. McCracken and published by . This book was released on 1994 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scaling and Transport Analysis of Divertor Conditions on the Alcator C Mod Tokamak written by Brian LaBombard and published by . This book was released on 1994 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Comparison of Impurity Screening Between Limiter and Divertor Plasmas in the Alcator C Mod Tokamak written by Robert Seth Granetz and published by . This book was released on 1996 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Plume Experiments in the Edge Plasma of the Alcator C Mod Tokamak written by Sanjay Gangadhara and published by . This book was released on 2003 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The physics of impurity transport in response to a local gas injection in the scrape-off-layer (SOL) of Alcator C-Mod is investigated. Carbon "plumes'' are formed at variable locations in the SOL -- up to the separatrix -- by puffing deuterated ethylene gas (C2D4) through the end of a reciprocating fast-scanning probe. CCD cameras are used to simultaneously record C+1 and C+2 emission patterns from two near-perpendicular views. The plume dispersal patterns are found to yield direct qualitative information about plasma flow, including the direction of VExB near the separatrix. Impurity transport and plasma-surface interaction physics implicit in the 3-D plume structure is explored in detail using a Monte Carlo impurity transport code, with the aim of extracting background plasma-flow quantities. A number of important local effects involving plasma-probe interaction have been identified: a vertical ExB drift near the probe surface, a parallel electric field above the probe tip arising from plasma recycling off the probe surface, and sputtering of a carbon layer that dynamically forms on the probe surface. The emission patterns are also found to yield important information on flows in the SOL: radial electric field (Er) in the near SOL and volume-averaged values of the parallel Mach number in the far SOL. Er values obtained from plume data compare favorably with estimates of Er based on the poloidal propagation velocity of edge plasma fluctuations measured by the scanning probe. Comparisons between parallel Mach numbers obtained from the plume data and probe measurements indicate that the probe over-estimates the parallel flow towards the divertor in the far SOL. This result supports the picture of particle balance in the SOL of Alcator C-Mod being dominated by main-chamber recycling, with weak plasma flow into the divertor.

Download or read book Energy and Impurity Transport in the Alcator C Tokamak written by Alcator Group and published by . This book was released on 1982 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Transport Studies on Alcator C Mod Tokamak Using Charge Exchange Recombination Spectroscopy written by Igor Olegovich Bespamyatnov and published by . This book was released on 2008 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Charge-Exchange Recombination Spectroscopy (CXRS) diagnostic has been installed on Alcator C-Mod to study the transport of light impurities in plasma. The system provides spatially (1 cm) and temporally (12.5 msec) resolved measurements of the impurity density, temperature and flow velocities of the particular impurity. Two optical arrays: poloidal (19 channels) and toroidal (10 channels), collect the light emitted from excited impurity ion populated by charge exchange process from the Diagnostic Neutral Beam (DNB) particle. The attention of this dissertation is focused on the B4 (n = 7 [-->] 6) spectral line emitted by B4 ion formed in the following charge exchange reaction (H0 + B5+ [-->] H+ + B4+*). A complex spectral model was developed to simulate emission. The high magnetic fields of C-Mod result in broad Zeeman patterns which must be taken into account for the interpretation of the line shift and broadening in terms of impurity ion velocity and temperature. After the spectral line fitting and careful identification of the charge exchange component, the calculated Doppler broadening and shifts of the spectral line profile yield information on the ion temperature and rotation. Together with the calculation of the beam density, the absolute calibration of the CXRS optical system provides us with B5+ density measurement capabilities. One of the main objectives of this work was to use the acquired impurity density, temperature and flow velocity profiles to investigate plasma transport behavior and infer the radial electric field E[subscript R] from plasma force balance equation. The focus here was placed on the region of the Internal Transport Barrier (ITB) formation 0.35

Download or read book Measurement of Impurity Ion Densities and Energies in the Divertor and Edge Regions of Alcator C Mod Tokamak Lab for Plasma Research Univ of Maryland College Park written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study to investigate impurity production and transport in the divertor and edge regions of the Alcator C-Mod tokamak through spectroscopic techniques is described. A 0.75-meter Czerny-Turner spectrometer with a 1200-g/mm grating and a 35-meter quartz optic bundle transmission line were tested. A high-resolution 2-meter spectrometer will be ordered. Data acquisition considerations are being addressed. (RWR).

Download or read book Understanding of Neutral Gas Transport in the Alcator C Mod Tokamak Divertor written by D. P. Stotler and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Impurity Ion Densities and Energies in the Divertor and Edge Regions of Alcator C Mod Tokamak Final Progress Report March 1994 January 1995 written by and published by . This book was released on 1995 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors are investigating impurity production and transport in the divertor and edge regions of the Alcator C-Mod tokamak through spectroscopic techniques. The emphasis is on the low ionization states found in the edge and divertor regions which are indicative of the physical processes related to impurity generation and particle and energy transport in this region. The authors are using a high-resolution visible/ultraviolet spectrograph capable of measuring the Doppler shifts associated with neutral and ion flows and the Doppler broadening associated with neutral and ion temperatures.

Download or read book Understanding of Neutral Gas Transport in the Alcator C Mod Tokamak Divertor written by D. P. Stotler and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Impurity Ion Densities and Energies in the Divertor and Edge Regions of Alcator C Mod Tokamak Progress Report February 1 1992 July 31 1992 written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study to investigate impurity production and transport in the divertor and edge regions of the Alcator C-Mod tokamak through spectroscopic techniques is described. A 0.75-meter Czerny-Turner spectrometer with a 1200-g/mm grating and a 35-meter quartz optic bundle transmission line were tested. A high-resolution 2-meter spectrometer will be ordered. Data acquisition considerations are being addressed. (RWR).

Download or read book Physics and Application of Impurity Plume Dispersal as an Edge Plasma Flow Diagnostic on the Alcator C Mod Tokamak written by Sanjay Gangadhara and published by . This book was released on 2003 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) A Monte Carlo impurity transport code (LIM) was used to simulate the plumes. Results indicate that contributions to the emission from sputtering explain the cross-field plume width, and that the parallel extent of emission generated in the far SOL is well-described using a sputter launch-energy distribution for the impurities. In the near SOL, the presence of a localized parallel electric field arising from background ion recycling off the probe surface is necessary to explain the parallel extent of emission generated in this region. This electric field accelerates impurity ions formed near the probe tip away from the probe, causing jet-like behavior. LIM was also used to investigate causes for the vertical elongation of the impurity emission. Results suggest the existence of a probe-induced E x B drift, of order ca. 1000 m/s in the near SOL. This drift may be responsible for the transport of both impurity and bulk plasma ions down the probe axis. Values for vII in the far SOL and Er in the near SOL have been extracted from the plume structure. A comparison between plume and probe results for Er suggests that calculations which employ a probe-sheath model may be in error, and that measurement of the poloidal propagation velocity of edge plasma fluctuations may be a more reliable means of inferring Er from probe data. Comparisons between plume- and probe-inferred values for the parallel Mach number suggest that the probe over-estimates parallel flow to the divertor in the far SOL, where effects of short field line connection to the divertor are important ...

Download or read book Dissipative Divertor Operation in the Alcator C Mod Tokamak written by B. Lipschultz and published by . This book was released on 1994 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Transport Studies in Tokamak Edge Plasmas Using Visibe Imaging written by Sanjay Gangadhara and published by . This book was released on 2001 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding impurity transport in the scrape-off layer (SOL) of tokamak plasmas is a necessary piece of developing the physics basis for designing next-generation reactors. A system for inferring impurity transport parallel and perpendicular to local magnetic field lines has been developed on Alcator C-Mod using gas-injection "plumes". In this system, impurity gas is injected at a fixed position in the SOL via a reciprocating fast-scanning probe, and the resulting emission is imaged. In this paper visible light emission patterns from C+1 and C+2 ions are presented.

Download or read book Particle Transport on the Alcator C Mod Tokamak written by Cindy R. Christensen and published by . This book was released on 1999 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Asymmetries in the Pedestal Region of the Alcator C Mod Tokamak written by Randy Michael Churchill and published by . This book was released on 2014 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to illuminate the effects of the strong plasma gradients in the pedestal region on impurity transport, research was conducted to measure complete sets of impurity density, poloidal and parallel velocity, and temperature at two separate poloidal locations in the pedestal region of the Alcator C-Mod tokamak. To this end, the diagnostic technique gas puff-CXRS was refined and expanded on, allowing for the first time in a tokamak complete measurements of impurities at the high-field side (HFS). Large in-out B5+ impurity density asymmetries were measured in H-mode plasmas with strong boundary electron density gradients, with a build-up of impurity density at the HFS. Impurity temperatures were also found to be asymmetric in the pedestal region, with larger temperatures at the low-field side (LFS). Such temperature asymmetries suggest a significant asymmetry in electron density near the separatrix. In contrast to these H-mode results, plasmas with low boundary electron density gradients, such as L-mode and I-mode, exhibit constant impurity density on a flux surface, even if strong electron temperature gradients are present. Mechanisms which could drive such poloidal asymmetries are explored. Experiments provide evidence against localized impurity sources and fluctuation-induced transport as primary causes. Particle transport timescales are compared, showing that the radial transport becomes comparable to or faster than the parallel transport in the pedestal region. Additionally, modelling of impurity transport using conventional, one-dimensional neoclassical physics fails to correctly reproduce the measured flux-surface averaged impurity density, suggesting along with the timescale estimates that a more complete two-dimensional treatment of impurity particle transport is required. The measured impurity velocities at the LFS and HFS are compared to the canonical form for particle flow velocity within the flux surface of a tokamak. Within the error bars of the measurement, agreement is found with the canonical form. The implications of exact matches to the canonical form are low radial transport, and the E x B drift dominating the perpendicular impurity flow. Further work is motivated into more precise velocity measurements to determine if the velocities exactly match this canonical form.

Download or read book Impurity Screening Studies in the Alcator C mod Tokamak written by G. M. McCracken and published by . This book was released on 1996 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: