A NUMERICAL STUDY OF THE DEPENDENCE OF AN MHD EQUILIBRIUM CONFIGURATION ON VARIATIONS OF P AND Q PROFILES
A new MHD equilibrium code, ESCO has recently been developed at ENEA, Bologna, as a part of a free boundary 1-1/2-D transport code; it permits to compute free boundary MHD equilibria for prescribed profiles of pressure, p, and safety factor, q. ESCO is particularly suitable to investigate the problem of determining the current density profile in a Tokamak plasma (or equivalently the q profile) from external magnetic measurements. (A brief review of the work in this field is given). The attempt is made to clarify to some extent, by means of a new mathematical formulation, the well-known difficulties connected with the solution of the problem. These considerations and the numerical results from code ESCO applied to JET, indicate that: a) external magnetic measurements alone are not sufficient to determine the internal q profile to a (+- 15%) degree of accuracy in the internal plasma. The q profiles determined by existing MHD identification codes are strongly dependent upon the class of functions chosen to represent the current density in the Grad-Schluter-Shavranov equation. b) The knowledge of pressure profile and external magnetic measurements, could allow, in principle, the determination of the entire q profile, but that the uncertainties in the experimental results introduce again a large inaccuracy in q in the central plasma.
Bibliographic Reference: WRITE TO THE PUBLICATIONS OFFICER, JET JOINT UNDERTAKING, ABINGDON, OXON, OX14 3EA (UK), MENTIONING REPORT JET-R(86)03, 1986
Record Number: 1989125058800 / Last updated on: 1987-11-01
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