The spherical pinch

This is essentially a review article covering several years of work on the spherical pinch (SP) concept of plasma formation and containment. Central to this concept is the creation of a hot plasma in the center of a sphere, plasma which is then compressed by strong imploding shock waves launched from the periphery of the vessel. The experimental program, which started with the classical cylindrical theta-pinch and continued with the inductive spherical pinch, has taken a turn, in recent times, with the discovery of the scaling laws governing spherical pinch experiments, which prescribe that high gas pressures are required for achieving fusion breakeven conditions. As a consequence, energy deposition in present spherical pinch devices is done through resistive, rather than inductive, discharges. In a pilot experimental program of modest initial condenser bank energy ( 1 KJ), we find that the instantaneous energy deposition in the central plasma can lead to temperatures of the order of 2 KeV, in agreement with the prediction of the Braginskii resistivity for such a plasma, and with the relation to the velocity of the diverging shock wave generated by the sudden deposition of energy into this plasma. Moreover, when the imploding shock waves contain the central plasma, we find the containment time to be as long as 5.4 sec and the plasma to be stable. In discharges in deuterium, neutrons are emitted close to 10⁷ per shot. From the experimental parameters of the plasma, one can derive a particle density for the shocked gas equal to 3.21×10¹⁹ cm^–3, a plasma temperature equal to 730 eV and a productn=1.73 × 10¹⁴ cm^–3· sec.Brief parts of this work are abstracted from previous works of the same author: C.A.S.I. (Canadian Aeronautics and Space Institute)Transaction,2, 21 (1969);Can. J. Phys.,58, 983 (1980);J. Fusion Energy,3, 199 (1983).