Abstract Details

Add files

Plasma Liner Compression of FRCs*

Author: George R Votroubek
Requested Type: Poster Only
Submitted: 2009-12-04 21:17:25

Co-authors: J.Slough, D.Kirtley, C.Pihl

Contact Info:
MSNW, LLC
8551 154th Ave NE
Redmond, WA   98052
USA

Abstract Text:
Magnetic fusion at high energy density requires compression of a magnetized target in a manner that can be repetitively pulsed. One approach being investigated at the MSNW facility is the radial compression of an FRC target by a radially converging plasma liner. The plasma liner is formed by utilizing a set of 32 of MPD plasma sources arranged in two opposing arrays near a dielectric vacuum chamber wall. An axial bias field embedded in the plasma liner is allowed to decrease toward zero, sweeping the magnetized plasma to the wall where it forms a conducting sheath which is highly coupled to the external theta-pinch coils. During this time, an FRC which has been formed in an adjacent chamber is translated into the evacuated area under the plasma liner. The bias field remaining in the liner chamber acts as both a guide field for FRC translation, and as a vacuum boundary between the FRC and the plasma liner. When the FRC is under the liner, fast theta-pinch coils are fired, driving the plasma liner inward, compressing the magnetic field external to the FRC. The liner, acting as an imploding conducting cylinder, increases the compression field acting on the FRC to a level much greater than possible with the theta pinch coils alone. The FRC slows as it translates into a higher field, thermalizing its translational kinetic energy, while the liner’s radial kinetic energy is transferred to the FRC through compression. The result is a hot, dense FRC.

The lifetime of the configuration is determined by the liner dwell time, rather than the FRC lifetime. The dwell time of the liner is governed by the ratio of the square root of the mass of the liner to the external magnetic field. Experimental demonstration of small-scale plasma liner formation and implosion has been completed. Liner masses of 3 mg have been formed in Xenon and have been accelerated to a velocity of 35-50 km/s employing a theta pinch compression coil at 0.5 T, resulting in a dwell time of a few microseconds. Close agreement is found between experimental results and 2D MHD numerical calculations. Efficient coupling between the compression bank and the plasma liner has been demonstrated, with roughly half of the compression bank energy transferred to the liner radial kinetic energy. Details of the liner dynamics will be discussed and initial results of FRC formation and translation into the liner chamber presented.

*Work supported by the US DOE.

Characterization: A1,A2

Comments: