Compound sawtooth study in ohmically heated TFTR plasmas Page: 3 of 26
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
2
1. INTRODUCTION
The sawtooth oscillation was first observed experimentally in the ST
tokamak [1] and a theoretical model describing this oscillation was given by
Kadomtsev [2). Since then, sawtooth activity has been studied in many
tokamaks and discussed in detail in relation to an unstable MHD mode and a
thermal transport model 13).
Simple sawtooth oscillations observed in tokamaks are a series of m = 0,
n = 0 relaxations, each with an m : 1, n = 1 precursor mode, where m and n are
poloidal and toroidal mode numbers, respectively. In contrast, compound
sawtooth activity has been observed recently in large tokamaks [4-7]. Each
compound sawtooth consists of a series of subordinate relaxation followed by a
large (up to 20%) main relaxation with a different inversion radius. These
compound sawteeth are commonly called "double sawteeth" because of their
approximate double period. Compound sawteeth appear frequently in ohmically
heated TFTR plasmas with high plasma current (I > 1.0 MA) and/or high density
(ne > 2.0 x 1019 m3). He.aver, compound sawtaeth do not always appear in
these particular discharge regimes. Instead small sawteeth can be present.
Figure 1 illustrates sawtooth activity observed for TFTR. Figure 1(a) shows
simple sawteeth (Type 1) which are observed in TFTR plasma with small minor
radii (a < 60 cm}. The compound sawteeth (Type 2) shown in Fig. 1(b) 'ce
sometimes observed in bursts accompanied by small sawteeth (Type 3).
Definitions in Fig. 1 are used for illustration purposes only. Table 1
illustrates the main features of the different types of sawteeth observed in
TFTR.
In JET, the compound sawteeth have been observed in high current and high
density discharges as in TFTR [61. In Doublet III, they appear in the limiter
discharges during neutral beam injection [5] and in TEXT they are observed
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Yamada, H.; McGuire, K.; Colchin, D.; Efthimion, P.C.; Fredrickson, E.; Hill, K. et al. Compound sawtooth study in ohmically heated TFTR plasmas, report, September 1, 1985; New Jersey. (https://digital.library.unt.edu/ark:/67531/metadc1055044/m1/3/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.