NEUTRAL BEAM PROBE FOR POTENTIAL MEASUREMENT IN TANDEM MIRRORS

THE DEVELOPMENT OF THE TANDEM MIRROR CONCEPT FOR THE CONFINEMENT OF THERMONUCLEAR PLASMAS IS DEPENDENT ON BEING ABLE TO ESTABLISH AND MAINTAIN THE PROPER AXIAL AND RADIAL POTENTIAL PROFILES THROUGHOUT THE SYSTEM. MUCH OF THE PRESENT EXPERIMENTAL EFFORTS IN TANDEM MIRROR RESEARCH ARE DIRECTED TOWARDS SHAPING AND CONTROLLING THE POTENTIAL DISTRIBUTIONS. AT PRESENT, THERE IS NO DEMONSTRATED TECHNIQUE THAT CAN BE GENERALLY APPLIED TO MEASURE THE AMBIPOLAR POTENTIAL IN HOT PLASMAS CONFINED IN COMPLEX MAGNETIC FIELD CONFIGURATIONS. INTERSCIENCE, INC. HAS EVALUATED A NUMBER OF POSSIBLE TECHNIQUES AND PROPOSES TO UNDERTAKE THE DEVELOPMENT OF A NEUTRAL BEAM PROBE SYSTEM AS THE MOST PROMISING APPROACH FOR POTENTIAL MEASUREMENTS IN COMPLEX, NON-AXISYMMETRIC MAGNETIC FIELD CONFIGURATIONS. THE NEUTRAL BEAM PROBE IS BASED ON A VARIATION OF THE HEAVY ION BEAM PROBE THAT HAS BEEN EXTENSIVELY APPLIED FOR POTENTIAL MEASUREMENTS IN SIMPLE, AXISYMMETRIC SYSTEMS. THE PARTICLE TRAJECTORIES ASSOCIATED WITH THE NEUTRAL BEAM PROBE ARE RELATIVELY SIMPLE. IT IS THEREFORE, BETTER SUITED FOR APPLICATION IN COMPLEX FIELD CONFIGURATIONS AND IS CAPABLE OF GREATER RANGE AND SENSITIVITY THAN THE ION BEAM PROBE. IN ORDER TO DEMONSTRATE ITS FULL CAPABILITIES, WE PROPOSE TO DEVELOP SUCH A DIAGNOSTIC FOR THE PHAEDRUS TANDEM MIRROR EXPERIMENT. UNDER PHASE I OF THE SBIR PROGRAM, WE SHALL FORMULATE A SPECIFIC DESIGN BASED ON EXTENSIVE DESIGN CALCULATIONS TO DETERMINE THE RANGE, RESOLUTION AND SENSITIVITY THAT CAN BE REALIZED FROM THE SYSTEM. IF THE PERFORMANCE CAPABILITIES APPEARS ATTRACTIVE, THE DESIGN CAN BE UTILIZED DIRECTLY AS THE BASIS FOR CONSTRUCTION OF A DEMONSTRATION SYSTEM UNDER PHASE II.