Dynamics of magnetically driven plasma jets : an instability of an instability, gas cloud impacts, shocks, and other deformationsud

摘要

The Caltech experiment described here produces plasmas relevant to both astrophysical and fusion energy studies. A disk-shaped set of electrodes mounted on the inside of a meter-scale vacuum chamber provides the energy to break a neutral gas, provided at the electrodes only, down into a plasma. The plasma starts as eight loops, and then self-organizes into a single magnetically driven collimated plasma jet. This thesis explores the dynamic evolution of that plasma jet and how changes made to the jet power source or environment alter the evolution. The most significant finding is the discovery that a series of instabilities can lead to magnetic reconnection. The jet undergoes a first, primary instability, called the kink instability. The exponential growth of kink amplitude provides an acceleration that drives a smaller scale, secondary instability, called the Rayleigh–Taylor instability. The Rayleigh–Taylor instability can drop the diameter of the plasma to a small enough scale to allow magnetic reconnection. A second set of experiments explores the range of collision interactions between the plasma jet and a cloud of neutral gas in its path. A final set of experiments shows the dependence of jet radius on a time-changing current. A new power supply that led to the observation of some of these new dynamics is also described.ud