Model of enhanced energy deposition in a Z-pinch plasma

In numerous experiments, magnetic energy coupled to strongly radiating Z-pi nch plasmas exceeds the thermalized kinetic energy, sometimes by a factor o f 2-3. An analytical model describing this additional energy deposition bas ed on the concept of macroscopic magnetohydrodynamic (MHD) turbulent pinch heating proposed by Rudakov and Sudan [Phys. Reports 283, 253 (1997)] is pr esented. The pinch plasma is modeled as a foam-like medium saturated with t oroidal "magnetic bubbles" produced by the development of surface m=0 Rayle igh-Taylor and MHD instabilities. As the bubbles converge to the pinch axis , their magnetic energy is converted to thermal energy of the plasma throug h pdV work. Explicit formulas for the average dissipation rate of this proc ess and the corresponding contribution to the resistance of the load, which compare favorably to the experimental data and simulation results, are pre sented. The possibility of using this enhanced (relative to Ohmic heating) dissipation mechanism to power novel plasma radiation sources and produce h igh K-shell yields using long current rise time machines is discussed. (C) 2000 American Institute of Physics. [S1070-664X(00)02808-1].