科研之友
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摘要
Divertor tokamaks such as ITER also need limiters for startup and rampdown, as well as protection of the main wall from normal and off-normal plasma loads during the diverted phase. Analysis of the optimum shape with regard to power handling of the plasma-facing surface is typically carried out using numerical procedures. This can make it difficult to identify underlying shaping principles. It is also important to have methods for conveniently and quickly checking the correctness of numerical results, approximately, using readily available analytic expressions. This paper provides such expressions together with their derivations for the case of multiple limiters at the outer wall, low-field side of a tokamak, illustrated here for the case of ITER. Analytic expressions are developed for the near-optimal toroidal shaping of individual limiters which, while distributing the deposited power on the limiter face as uniformly as possible, also provides adequate protection of the limiter edges against over-heating-for a range of plasma shapes and conditions and for a specified number of limiters, limiter sizes, sizes of gaps between limiters and relative radial misalignment between adjacent limiters. The effect of shadowing of one limiter by another is included, for shadowing of both edges and faces. Analytic expressions are developed for the magnitude and location of the peak power flux density deposited on the face and edges of the limiters. There are sufficient important differences in the shaping required for wall regions on the low- and high-field sides and in the secondary divertor region at the top of the vessel to warrant separate treatments of each of the three cases. In subsequent papers analytic expressions will be developed for the inner wall and the top wall.
- 出版日期2011-10
