For the optimization of tokamak performance, the international fusion energy community generally has a need for current density profile measurements. To accomplish such measurements, it is planned to accelerate unpolarized ground state atoms (hydrogen or helium) along a chord through the plasma to a distant particle detector on the outer wall of the vacuum vessel. Transmitted beam detection makes best diagnostic use of a single penetration in the tokamak radiation shield and avoids losses of solid angle for fluorescence detectors. Collisions with plasma electrons maintain a fraction of these beam atoms in the short-lived first excited state. Polarized light from a scanning laser beam further excites the atoms in the first excited state to higher, rapidly ionized states. The phase angle between the rotating laser polarization and the resulting change in beam attenuation reveals the magnetic field orientation (poloidal field as a fraction of the toroidal field at the point of intersection of the atom and light beams). In Phase I, a laser-scanned atomic beam probe will be analyzed, and the operation of an appropriate neutral beam source concept demonstrated. Complete specifications for a system will be developed in Phase II, together with a source, detector, and auxiliary equipment, which would be supplied to an appropriate fusion laboratory in Phase III for preliminary operation and prototype testing before installation on CIT.Anticipated Results/Potential Commercial Applications as described by the awardee: The commercial application for this project is in fusion energy research programs. It is planned to analyze a diagnostic system, specify the components, and supply fusion laboratories with those subsystems that are not commercially available. The diagnostic system being developed measures the profile of the current density in a heated plasma for use in optimizing tokamak performance for maximum stable beta and energy confinement or in developing methods of controlling a fusion burn.Topic 11: Plasma Diagnostics
