FUSION REACTIVITY CHARACTERIZATION OF A SPHERICALLY CONVERGENT ION FOCUS

The deuterium-deuterium (D-D) fusion reaction rate in a spherically co nvergent ion focus is observed to significantly exceed the rate predic ted by a collisionless flow model. However, a careful consideration of ion-neutral collisions and the trapped neutral density in the cathode account for the extra reactivity without invoking anomalous ion trapp ing in the converged core region. This conclusion is supported by prot on collimation measurements, which indicate that the bulk of the obser ved reactivity originates outside the core region. In addition, a clas sical flow model, where charge exchange collisional effects on the ion and fast neutral distributions are included, provides fusion rate est imates that we quantitatively consistent with the observed D-D fusion neutron production rate.