A tokamak plasma near equilibrium can be perturbed with modulated
power sources, such as modulated electron cyclotron heating, or repeated cold
pulse application. Temperature response to cyclical changes in profiles parameters
that are induced by modulated power deposition can be used to test
theoretical transport models as well as improve experimental phenomenology
used to optimize tokamak performance. The goal of this document to discuss
some methods of analyzing electron temperature data in the context of energy
transport. Specific experiments are considered in order to demonstrate
the methods discussed, as well as to examine the electron energy transport
properties of these shots.
Electron cyclotron emission provides a convenient way to probe electron
temperature for plasmas in thermal equilibrium. We can show that in tokamak
devices,barring harmonic overlap, we can associate a particular frequency with a particular location in a tokamak, by carefully selecting the detection frequency
and line of sight of the responsible antenna. ECE radiometers typically
measure temperature at tens of locations at a time with a spatial resolution
on the order of a few centimeters. Tracking the evolution of electron energy
flux depends on careful analysis of the resulting data.
The most straightforward way to analyze temperature perturbations is
to simply consider various harmonics of the driving source and consider the
corresponding harmonics in the temperature. We can analyze the phase and
amplitude of the response to find the effective phase velocity of the perturbation
which can in turn be related to parameters in the selected heat flux
model. The most common example is to determine , the diffusion coefficient
that appears in the linearized energy transport equation. The advantages and
limitation of this method will be discussed in detail in Section 3.
A more involved approach involves using the perturbed temperature
data to compute modulated heat flux at any given point in the perturbation
cycle, rather than using the temperature data directly. As before the heat flux
can then be related to measured profile parameters and theoretical predictions.
The advantages and limitations of this approach will be discussed in more
detail.
Both of the mentioned analysis methods are used to probe electron
energy transport in a quiescent H mode (QH mode) shot conducted at DIIID.
The nature of the internal transport barrier that is present in the shot is
considered in light of the results. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2010-08-2181 |
| Date | 17 February 2011 |
| Creators | Meyerson, Dmitry |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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