Recent developments in linear theta-pinch and laser-heated solenoid research

At LASL, the experimental results from the high energy (T/sub e/ + T/sub i/ = 3.3 keV, n/sub e/ = 1.5 x 1016 cm-3) 5-m Scylla IV-P theta pinch support the following: (1) single mode m = 1 ''wobble'' instability rotation frequencies of approximately 180 kHz are associated with axial wavelengths of 400 to 800 cm; (2) ion thermal conduction is an unimportant loss mechanism; (3) evidence of rarefaction-like waves is seen; (4) the normalized end-loss time is independent of the plasma beta and collisionality regime; (5) plasma flow from the ends remains collimated and convects magnetic fields; (6) LiD end plugs produce a three-fold increase in energy containment time over the open-ended configuration. Theoretical work at LASL has demonstrated the following: (1) an explanation of the m = 1 ''wobble'' instability has been formulated; (2) a correct description of end-loss must include the magnetic curvature term in the axial momentum equation. Mirrors increase the lifetime of a collisional plasma less than guiding center theory predicts; (3) magnetic field gradient drift can reduce the growth rate of the universal drift instability; (4) collisionless magnetoacoustic heating can be an effective heating mechanism in theta pinches. At MSNW-UW, CO2 laser heating of low energy (T/sub e/ approximately equal to T/sub i/ approximately equal to 2 eV, n/sub e/ approximately equal to 2 x 1017 cm-3) plasmas is accomplished over a one-meter column length. Maintenance of an on-axis density minimum is demonstrated