(Georgia Institute of Technology, 2008-05-05)
Seltzman, Andrew
Traditional inertial electrostatic confinement (IEC) fusion reactor designs utilize an ion accelerating grid fabricated out of a refractory metal capable of operating at high temperatures to radiate off heat imparted by ion-grid collisions. Unfortunately, the high gird temperature allows for a substantial thermionic electron emission current, requiring a high power draw and significantly reducing reactor efficiency. Further, electrons emitted from the grid are accelerated into the reactor shell where they generate a significant amount of bremsstrahlung x-rays requiring additional shielding and increasing system size and weight.
Presented is a novel modification to the traditional implementation of IEC fusion reactor, designed to improve operating efficiency by reducing electron emission from the grid. A liquid cooled grid design is utilized to reduce thermionic electron emission, allowing for higher plasma densities, and greater input power while improving system efficiency and reducing x-ray output. The resulting low grid temperatures substantially reduce thermionic electron emission and greatly improve reactor efficiency by reducing current draw from the central grid. The reduction of thermionic electron emission will eliminate the majority of bremsstrahlung x-ray generation thereby reducing shielding requirements.
By measuring the heat deposited into the coolant, the grid cooling system may also be used as a diagnostic tool to study the physics involved in IEC reactors. In this manner, grid transparency may be directly measured as a function of ion bombardment heating. By modifying the confinement scheme of the reactor and subsequently evaluating the energy flux to the grid through ion collisions, greater energy and particle confinement times may be obtained.