Tokamak Diagnostics Research Articles

Engineering Aspects of JET Diagnostic Systems

The paper presents an outline description of the function of each diagnostic system and then considers in more detail their general engineering aspects and some of the development work that has been incurred in meeting specific requirements. The way in which the engineering has differed from previous tokamak diagnostics is discussed illustrating the effect of the Joint European Torous (JET) environmental factors such as radiation, the need for remote handling, and scale. The techniques for interfacing the various diagnostic control systems to the overall machine computerized control system are presented. Finally, three diagnostic systems are described.

Data structure for the description of tokamak diagnostics

A novel open-ended file structure has been designed to describe ‘‘shot files’’ of a tokamak experiment. Elements of a shot file are data structures, called objects, that describe various aspects of the experiment. A general overview of the data analysis system AMOS/D is presented first, and then a detailed description of the shot file structure and the access procedures to shot data are given.

Calculation of the combined Zeeman and translational Stark effect on the Hα-multiplet

The properties of the combined Zeeman and translational Stark effect on the hydrogen Balmer α line have been studied in detail under various plasma conditions. The applicability of the calculation method proposed here to transitions involving terms of hydrogenic atoms and hydrogen-like ions is suggested. Apart from its relevance for line profile measurements and particle beam diagnostics in Tokamaks some features concerning the application of the translational linear Stark effect in atomic and plasma physics are discussed.

The Texas Experimental Tokamak (Text) Facility User's Facility

The Texas Experimental Tokamak is a medium-scale tokamak operated as a national user facility. Now in operation, it provides a plasma with a 1-m major radius, 28-cm minor radius, and 400-kA nominal plasma current at up to 3-T toroidal field for pulse lengths of 300 to 500 ms. The facility includes all standard tokamak diagnostics and an integrated data system that makes all data available after each shot, as often as once every 2 min. The design is generally conventional and conservative, the vacuum vessel provides numerous large-aperture radial and vertical ports for complete views of the plasma. 5 refs.

An approach to rapid plasma shape diagnostics in tokamaks

A study is made of a diagnostic procedure which allows one to estimate the plasma boundary shape and location in a tokamak by using numerical values of the poloidal magnetic flux function ψ in the vicinity of the plasma. In the case of the Impurity Study Experiment (ISX-B) tokamak, the magnetic sensor coils located around the periphery of the vacuum chamber provide information on ∂BR/∂t and ∂Bz/∂t, which can be processed to obtain data on ψ (and ∂ψ/∂n) through the relation BR = - R-1∂ψ/∂Z and Bz = R-1∂ψ/∂R. This leads to a Cauchy boundary condition for the Grad-Shafranov equation Δ*ψ = 0 in the region between the contour of the sensor coil locations and the plasma boundary flux surface. Numerical equilibria calculated for the ISX-B with different shapes are used to simulate ψ data along the coil locations. Random errors are added to the data to test the efficacy of two different approaches: global fitting and local fitting. Reasonably accurate results are obtained by the method of global fitting of the boundary values, which is based on the expansion of ψ in terms of eigenfunctions of Δ*ψ = 0 in a toroidal ring co-ordinate system. This approach is found to permit a relatively large random error in poloidal B field values at the sensor coils and appears to have the potential of rapidly displaying the plasma shape and location.

NEW TOROIDAL COIL SYSTEM FOR TOKAMAKS

An idea is suggested which leads to a significant reduction in the required number of toroidal field coils and to a dramatic improvement in access for tokamak maintenance and diagnostics. It is found that a two or four coil system may be practical. The basic concept is presently being used for designing RST (Radio Frequency Driven, Steady-State Tokamak) of General Atomic Company.