The Fusion and Astrophysical Plasma Physics Group within the Physics Department and the Center for Astrophysics and Space Sciences at the University of California, San Diego is led by Professor Patrick H. Diamond and consists of two research scientists-- Mikhail Malkov, Fred Hinton, and four graduate student researchers-- and is managed by an administrative assistant.
Linking the Micro and Macro: L-H Transition Dynamics and Threshold Physics - M.A. Malkov, P.H. Diamond, K. Miki, J.E. Rice and G.R. Tynan
The links between the microscopic dynamics and macroscopic threshold physics of the L → H transition are elucidated. Emphasis is placed on understanding the physics of power threshold scalings and especially on understanding the minimum in the power threshold as a function of density P thr (n). By extending a numerical 1D model to evolve both electron and ion temperatures including collisional coupling we find that the decrease in P_thr (n) along the low-density branch is due to the combination of an increase in collisional electron-to-ion energy transfer and an increase in the heating fraction coupled to the ions. Both processes strengthen the edge diamagnetic electric field needed to lock in the mean electric field shear for the L→H transition. The increase in P_thr (n) along the high-density branch is due to the increase with ion collisionality of damping of turbulence-driven shear flows. Turbulence driven shear flows are needed to trigger the transition by extracting energy from the turbulence. Thus we identify the critical transition physics components of the separatrix ion heat flux and the zonal flow excitation. The model reveals a power threshold minimum in density scans as a crossover between the threshold decrease supported by an increase in heat fraction received by ions (directly or indirectly from electrons) and a threshold increase supported by the rise in shear flow damping. The electron/ion heating mix emerges as important to the transition in that it together with electron-ion coupling regulates the edge diamagnetic electric field shear. The importance of possible collisionless electron-ion heat transfer processes is explained.
The memory of Professor Marshall N. Rosenbluth- an American plasma physicist and member of the National Academy of Sciences- who passed away on September 23, 2003.
We are working primarily on the theory of fusion plasma including: