A SUBMILLIMETER-WAVE ALPHA PARTICLE THOMSON SCATTERING DIAGNOSTIC FOR THE COMPACT INGNITION TOKAMAK

A SUBMILLIMETER-WAVE COLLECTIVE THOMSON SCATTERING SYSTEM ISBEING DEVELOPED IN THIS PROJECT AS A DIAGNOSTIC SYSTEM FOR THE ALPHA PARTICLE DISTRIBUTION FUNCTION IN THE COMPACT IGNITION TOKAMAK (CIT). CALCULATIONS OF THE CYCLOTRON EMISSION AND ABSORPTION COEFFICIENTS IN THE PLASMA, AND CONSIDERATIONS OF SCATTERING ANGLE, SPATIAL RESOLUTION, AND ACCESS TO THE PLASMA INDICATE THAT WAVELENGTHS IN THE RANGE 100-150 MUM ARE OPTIMAL FOR SCATTERING FROM A CIT PLASMA. AN AVERAGE POWER IN THE RADIATION BEAM OF AT LEAST 0.1 MW IS REQUIRED FOR A SUCCESSFUL DIAGNOSTIC MEASUREMENT. THE PHASE I EFFORT WILL EXAMINE THE FEASIBILITY OF A HIGH POWER FREE ELECTRON LASER (FEL) AS A SUBMILLIMETER-WAVE RADIATION SOURCE FOR THOMSON SCATTERING FROM ALPHA PARTICLES IN CIT. FREE ELECTRON LASERS HAVE BEEN SHOWN TO BE EFFICIENT GENERATORS OF HIGH POWER RADIATION AT SUBMILLIMETER WAVELENGTHS. THE FEL WILL BE DRIVEN BY A COMPACT, LOW COST INDUCTION LINEAR ACCELERATOR BASED ON AN ALL SOLID STATE DRIVER. THE FEL WILL BE CONFIGURED AS A SINGLE PASS, HIGH GAIN AMPLIFIER OF A NARROW BAND INJECTED SIGNAL FROM A GAS LASER. PHASE I WILL CONCENTRATE ON THE PHYSICS AND TECHNOLOGICAL ISSUES OF THE FEL AMPLIFIER AND WILL CULMINATE IN A DESIGN FOR A COLLECTIVE SUBMILLIMETER-WAVE THOMSON SCATTERING DIAGNOSTIC. A DETAILED DESIGN OF THE SOURCE, INCLUDING THE INDUCTION LINAC AND WIGGLER MAGNET WILL BE PROVIDED.