Effects of Ionization and Magnetic Initial Conditions on a Magnetically Compressed Plasma (Scylla)

Abstract

The effects of strong preionization and the application of steady bias magnetic fields on the operation of the magnetic compression device Scylla are studied. It is shown that both strong preionization and a bias field B₀ antiparallel to the main compression field B_z are necessary to produce neutrons during the first half‐cycle of B_z. Other aspects of the plasma activity are also shown to depend strongly upon the sign of B₀. Application of bias fields with weak preionization leads to production of hard x rays which occur on the half‐cycle of the discharge which precedes that of neutron emission. When hard x rays are produced the plasma is not hydromagnetic. The hard x rays are extinguished when there is strong preionization, leading to a hydromagnetic plasma. In the case of the hydromagnetic plasma it is concluded that antiparallel B₀ plays its role early in a given half‐cycle and affects the plasma primarily during its preheating, ionization phase, rather than during the adiabatic‐compression phase which follows it. An interpretation is given in terms of a plasma sheath which has special properties when it separates magnetic fields of opposite signs.