Development of an intense neutral beam for the injected internal target technique (IT)2, diagnostic system

The (IT)2 diagnostic beam probe will be used to measure the hot electron density and temperature profiles in the thermal barrier and MHD anchor regions of the TARA tandem mirror experiment. The measurement requires a high-quality beam with current densities > 50 mA/cm2 at beam energies of 50-100 keV. The design of the extractor/accelerator configuration was done using the ORNL ion optic beam code, and studies using the code indicate a beam divergence, Δ Theta ≤ 0.50. The beam will be extracted from a rf generated dense plasma source; and space-charge neutralization of the beam will be accomplished by plasma formed by another rf discharge in the vicinity of the extractor, prior to the charge exchange cell. Measurements of the plasma source performance and details of the design will be presented