Instrumentation for a prototype fusion propulsion system

A prototype colliding beam accelerator has been fabricated for the study of a fusion-based propulsion concept for interplanetary exploration. The purpose of this prototype is to demonstrate collider luminosities commensurate with the requirements of this application. While fusion fuels such as p/Li7 and He3/He3 would generate the required thrust characteristics, this prototype currently employs deuterium. Because neutrons are produced via DD fusion with a peak cross section of 0.1 barns, even modest initial luminosities yield event rates suitable for real-time measurements and lifetime monitoring. The proposed luminosity monitor is based on neutron moderation and absorption and subsequent gamma-ray detection. Sodium chloride serves as the moderator, with most neutrons absorbed by chlorine-35 nuclei having a thermal neutron absorption cross section of 43.6 barns. The collider is a linear device employing electrostatic axial confinement and radial focusing. A combination of destructive and nondestructive sensors are employed to monitor various beam parameters such as intensity, energy spectrum, transverse tunes and halo density distribution.