Progress on the momentum-rich ion beam concept for ICF

In the momentum rich beam (MRB) approach to inertial confinement fusion, ions from a low emittance source are electrostatically accelerated to 30-1000 keV, neutralized, and then propagate first collisionlessly then, at a few cm radius, collisionally to target. Encouraging experimental and theoretical results have changed the MRB approach to inertial fusion since the last report¹⁾. Measurements on a cesium ion source show extremely low divergence beams with transverse beam temperature of only 0.leV, the source thermal temperature. Neutralization adds very little divergence to beam. Using collimated argon and xenon plasma sources accelerated to 50ke V, we found the rms resonant scattering angle proportional to √I/m_i. The scattering angle is halved by neutralizing an argon beam with cesium, rather than argon gas. During the collisionless collapse a precursor is formed which can implode the target more adiabatically. Calculations of the collisional collapse show 3/4 or more of the beam thermal energy will be radiated away. Since this energy arose from the compression of initial transverse velocities, higher emittance ion sources can be used. Targets containing DT calculate to ignite and achieve moderate gain (20) with beam energies below lMJ. DD targets also calculate to burn at similar beam energies, avoiding the need for tritium breeding in a reactor.