![\"Figure](\"https:\/\/www.europesays.com\/uk\/wp-content\/uploads\/2025\/06\/e79_1.png\")
<\/a><\/p>\nM. Cao and P. H. Diamond [1<\/a>]<\/p>\n Like all fusion reactor designs, tokamaks\u2015donut-shaped machines that confine plasma using magnetic fields\u2015offer challenges for theorists. One such challenge is understanding why numerical simulations sometimes underpredict the width of a turbulent region between the edge and the core of the plasma. Using a first-principles model, Mingyun Cao and Patrick Diamond at the University of California, San Diego, have attributed the discrepancy to instabilities at the plasma\u2019s outer boundary, which have not been fully accounted for until now [1<\/a>]. The researchers say that controlling these instabilities could improve plasma confinement and help to bring sustained fusion closer to reality.<\/p>\n In an ideal tokamak, the plasma\u2019s outer boundary is defined by a sharp gradient in temperature and density. Cao and Diamond considered a boundary instability known as a gradient relaxation event, in which the edge plasma breaks up into outward-moving \u201cblobs\u201d and inward-moving \u201cvoids.\u201d Blobs have been studied extensively in the context of plasma\u2013wall interactions, but only recently have advances in experimental diagnostics made it possible to track the inward motion of voids.<\/p>\n The researchers constructed a model in which these voids were treated as large, coherent particles. As the particle-like voids move through the plasma, they generate oscillations known as plasma drift waves. This wave generation is analogous to the emission of electromagnetic radiation by a charged particle moving faster than the speed of light in a medium. Cao and Diamond found that these drift waves can energize local turbulence, leading to the formation of a broad turbulent layer. Using their model, the researchers calculated the width of this turbulent layer. They are now working on comparing their calculations with experimental data.<\/p>\n \u2013Rachel Berkowitz<\/p>\n Rachel Berkowitz is a Corresponding Editor for\u00a0Physics Magazine<\/a> based in Vancouver, Canada.<\/p>\n References<\/p>\n Subject AreasRelated Articles
\nM. Cao and P. H. Diamond [1<\/a>]<\/p>\n\n
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