Magnetized implosions driven by intense ion beams

Intense beams of heavy ions, envisaged for the near future at the Institute for Theoretical and Experimental Physics (Moscow) and Gesellschaft fur Sch werionenforschung (Darmstadt), will be well suited for conducting implosion experiments in cylindrical geometry. In such implosions, the initial press ure generated by the direct beam heating can be enhanced by more than a fac tor of 10. If, in addition, an external magnetic field is introduced, the e ffect of magnetothermal insulation may allow to reach kilovolt temperatures and significant thermonuclear neutron yields in magnetized implosions driv en by the beam heating intensities as low as epsilon similar or equal to1 T W/g. It is shown how the combined effect of the electrical resistivity and thermal conductivity sets a lower limit on the product UR (R is the radius, and U is the velocity of an imploding plasma volume) as a necessary condit ion for the regime of self-sustained magnetized implosion (SSMI). The optim al plasma parameters required for initiation of this regime are evaluated. In cylindrical geometry, the threshold for the SSMI regime is determined by the total driver energy deposition per unit areal density of the cylinder, rho (-1)parallel to dE(b)/dz parallel to (kJ cm(2)/g). The results of one- dimensional magnetohydrodynamic simulations indicate that the advantages of magnetized implosions begin to manifest themselves at a beam energy level of E(b)approximate to 100 kJ. (C) 2000 American Institute of Physics. [S107 0-664X(00)01911-X].