Geometric Focusing of 20-GW Proton Beams with Use of a Magnetically Insulated Diode

We have obtained initial geometric-focusing results using a high-current (≳ 100 kA) magnetically insulated diode. At the line focus, current densities over 300 A/${\mathrm{cm}}^2$ have been obtained with a radial compression of about 10. Results for propagation of the intense beams are in excellent agreement with geometric single-particle predictions.