Detailed observations on the dynamics and heating of a linear theta-pinch

A detailed study is presented of the characteristics of a theta-pinch plasma formed in pre-ionised hydrogen with initial electron density in the range 2 - 5 x 1020m-3 corresponding to filling densities in the range 0.7 - 1.4 x 1021m-3 [10 - 20 mtorr]. The observations reported here are consistent with those reported previously. The onset of microinstabilities in the initial current sheath leading to anomalously high resistivity and electron heating, allows rapid field diffusion and leads to a fast implosion which sweeps up only a fraction of the initial filling gas. The origin of the radial filamentary structure which also appears at this time is not known. The subsequent compression dynamics are consistent with magnetohydrodynamic oscillations followed by a slow adiabatic compression leading to a final compression ratio eta of approximately 2.5. (U.K.)