Accessibility for lower hybrid waves in PBX-M

Abstract

Understanding the wave damping mechanism in the presence of a `spectral gap` is an important issue for the current profile control using Lower Hybrid Current Drive (LHCD). The authors examine a traditional explanation based upon upshifting of the wave parallel refractive index (n{sub {parallel}}) and find that there can be an upper bound in the n{sub {parallel}} upshift. The amount of upshift is not sufficient to bridge the spectral gap completely under some PBX-M LHCD conditions. There is experimental evidence, however, that current was driven even under such conditions. Another mechanism is also considered, based upon the 2-D velocity space dynamics coupled with a compound wave spectrum, here consisting of forward- and backward-running waves. The runaway critical speed relative to the phase speeds of these waves plays an important role in this model.

Related Papers

• → A version of Aldous’ spectral-gap conjecture for the zero range process(2019)18 cited
• → Asymptotics of the spectral gap for the interchange process on large hypercubes(2011)15 cited
• → The spectral gap of the 2-D stochastic Ising model with nearly single-spin boundary conditions(2000)4 cited
• LOWER BOUNDS FOR THE SPECTRAL GAP AND AN EXTENSION OF THE BONNET-MYERS THEOREM(2024)