Cold-start effects in experiments on the implosion of plasma liners in theAngara-5-1 facility

A study is made of the cold-start effects in plasma liners that implode und er the action of a 4-MA current and are produced by the current itself from microheterogeneous (foam) and homogeneous (gas) substances. For a wide ran ge of experimental parameters, it is shown that, for a sufficiently rapid c urrent rise, dl/dt similar to (0.5-1) x 10(14) A/s, which is necessary for the efficient acceleration of a 100-mu g/cm plasma to a velocity of similar to 5 x 10(7)cm/s on a 1-cm spatial scale, the plasma formation in the init ially cold liner is not completed by the time the magnetic force [jH] comes into play. The influence of the magnetic force on the plasma nonuniformiti es is discussed. The rearrangement of plasma nonuniformities during the tra nsition from the stage of plasma formation to the acceleration of the plasm a liner is analyzed. It is shown that, in the cold-start regime, the format ion of a plasma in a still immobile liner can be accompanied by the onset o f an axial nonuniformity due to azimuthal nonuniformity of the discharge cu rrent. The effect of fast penetration of the azimuthal magnetic flux into t he imploding liner near the cathode is considered. It is found that the low -density plasma produced from a solid foam in the current-rise stage drifts out of the plasma production region under the action of the jH force. Both the time delay in the plasma formation and the plasma nonuniformities resu lting from the rapid current rise in the cold-start regime of homogeneous a nd heterogeneous liners are considered to be important Factors affecting th e implosion.