Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake

摘要: Advanced divertors are magnetic geometries where a second X-point is added in the divertor region to address serious challenges of burning plasma power exhaust. Invoking physical arguments, numerical work, and detailed model field analysis, we investigate structure advanced physically relevant for exhaust—the scrape-off layer. A primary result our analysis emergence “metric,” Divertor Index DI, which quantifies flux expansion increase as one goes from main strike point. It clearly separates three with distinct consequences physics—the Standard (DI = 1), two geometries—the X-Divertor (XD, DI > 1) Snowflake < 1). The XD, therefore, cannot be classified variant Snowflake. By this measure, recent National Spherical Torus Experiment DIIID experiments X-Divertors, not Snowflakes.