Diagnostic Systems on Alcator C-Mod

Diagnostic Systems on Alcator C-Mod
Author: Nils Plesner Basse
Publisher:
Total Pages: 92
Release: 2005
Genre:
ISBN:

An overview of the diagnostics installed on the Alcator C-Mod tokamak [I. H. HUTCHINSON et al., Phys. Plasmas, Vol. 1, p. 1511 (1994)] is presented. Approximately twenty-five diagnostic systems are being operated on C-Mod. The compact design of the machine and the cryostat enclosing the vacuum vessel and magnetic field coils make access challenging. Diagnostics are used to study four focus areas: Transport, plasma boundary, waves and macrostability. There is significant overlap between these topics and they all contribute towards the burning plasma and advanced tokamak thrusts. Several advanced and novel diagnostics contribute to the investigation of C-Mod plasmas, e.g. electron cyclotron emission, phase-contrast imaging, gas-puff imaging, probe measurements and active magnetohydrodynamic antennas.

Diagnostics for Experimental Thermonuclear Fusion Reactors 2

Diagnostics for Experimental Thermonuclear Fusion Reactors 2
Author: Peter E. Stott
Publisher: Springer Science & Business Media
Total Pages: 615
Release: 2012-12-06
Genre: Science
ISBN: 1461553539

This book of proceedings collects the papers presented at the workshop on "Diagnostics for Experimental Fusion Reactors" held at Villa Monastero, Varenna (Italy) September 4-12, 1997. This workshop was the seventh organized by the International School of Plasma Physics "Piero Caldirola" on the topic of plasma diagnostics and the second devoted to the diagnostic studies for the International Thermonuclear Experimental Reactor (ITER). The proceedings of the first workshop on ITER diagnostics were published by Plenum Press in 1996 with the title "Diagnostics for Experimental Thermonuclear Fusion Reactors". While many of the ideas and studies reported in the first workshop remain valid, there has been sub stantial progress in the design and specification of many diagnostics for ITER. This moti vated a second workshop on this topic and the publication of a new book of proceedings. ITER is a joint venture between Europe, Japan, Russia and USA in the field of con trolled thermonuclear fusion research. The present aim of ITER is to design an experimental fusion reactor that can demonstrate ignition and sustained burn in a magnetically confined plasma. To achieve this goal, a wide range of plasma parameters will have to be measured reliably. It is also anticipated that diagnostics will be used much more extensively as input to control systems on ITER than on present fusion devices and this will require increased relia bility and long-term stability.

Impurity Transport Studies on Alcator C-Mod Tokamak Using Charge Exchange Recombination Spectroscopy

Impurity Transport Studies on Alcator C-Mod Tokamak Using Charge Exchange Recombination Spectroscopy
Author: Igor Olegovich Bespamyatnov
Publisher:
Total Pages: 322
Release: 2008
Genre: Charge exchange
ISBN:

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

Helium Charge Exchange Recombination Spectoscopy on Alcator C-Mod Tokamak

Helium Charge Exchange Recombination Spectoscopy on Alcator C-Mod Tokamak
Author: Kenneth Teh-Yong Liao
Publisher:
Total Pages: 704
Release: 2014
Genre:
ISBN:

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.