Finite Width Currents, Non-Uniform Magnetic Shear and the Current Driven Ion Cyclotron Instability.
NAVAL RESEARCH LAB WASHINGTON DC
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Our earlier results that non-local effects due to even a small magnetic shear produce a significant reduction of the growth rate of the ion cyclotron instability driven by a uniform current are now generalized to finite width currents. Externally prescribed as well as self-consistent shears are considered. If the current width Lc exceeds the shear length Ls, the previous results are recovered. Shear becomes less effective with reduction of Lc, and for typical parameters, the growth rate attains its shearless local value for LcLs approximately less than 10 to the minus 2. Non-local effects of the finite current width itself come into play if Lc is further reduced to a few ion Larmor radii and can quench the instability.
- Electricity and Magnetism
- Particle Accelerators