CURRENT DENSITY PROFILE DIAGNOSTIC SYSTEM ANALYSIS AND AN ATOMIC BEAM SOURCE FOR THE COMPACT IGNITION TOKAMAK

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 SHOT-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.