Design of microwave electric field diagnostics (LAPPS) in MTX tokamak plasma

Summary form only given. A new method has been developed to measure the spatially resolved microwave electric field in the MTX (Microwave Tokamak Experiment) plasma. This method combines laser-induced fluorescence spectroscopy with a neutral particle beam. Laser-Aided Particle Probe Spectroscopy (LAPPS). One of the most difficult problems is to provide a sufficient density of the radiating atoms in the center of the (burned-out and highly collisional) plasma. Computer simulation calculations indicate that a sufficient density of radiating atoms can be obtained at the center of the MTX plasma with a helium diagnostic neutral beam (energy=50 keV, current (metastable triplet)=80 mA). The metastable helium atoms will be produced when they traverse a Xe charge exchange chamber (about 10% conversion efficiency). A dye laser will be used to pump the helium atoms from the metastable level. The microwave electric field in the MTX plasma is expected to be several hundred kilovolts per centimeter. Therefore. the forbidden line will be strongly excited by the Stark effect of the microwave electric field. The emission from the excited atoms will be measured to estimate the absolute value of the spatially resolved microwave electric field