Multi-MeV Li/sup 0/ beam as a diagnostic for fast confined alpha particles

We discuss a method of measuring the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a magnetically contained plasma. We calculate the characteristics of the signals to be expected from injecting multi-MeV Li/sup 0/ into the plasma to undergo double charge-exchange reactions with the alpha particles. Neutralized alpha particles then escape from the plasma to be detected by a charge-exchange analyzer. We also examine the feasibility of producing a Li/sup 0/ beam of the required current and energy, and we discuss a conceptual design for an appropriate beam system

Technique for measuring the fast /sub 3/He/sup + +/ distribution during /sub 3/He/sup + +/ minority ICRF heating

A technique for measuring the fast /sub 3/He/sup + +/ distribution during /sub 3/He/sup + +/ minority ICRF heating is discussed. The technique involves the use of 10 to 100 keV neutral helium beams to neutralize the fast /sub 3/He/sup + +/ ions by double charge exchange (/sub 3/He/sup + +/ + /sub 4/He/sup 0/ ..-->.. /sub 3/He/sup 0/ + /sub 4/He/sup + +/). The neutralized fast /sub 3/He atoms then escape from the plasma and are detected by conventional neutral particle analyzing apparatus. By the use of such a technique, the effectiveness of the coupling of the ion cyclotron waves to the /sub 3/He/sup + +/ minority could be measured

Technique for measuring cooling patterns in ion source grids by infrared scanning

Many plasma sources designed for neutral beam injection heating of plasmas now employ copper beam acceleration grids which are water-cooled by small capillary tubes fed from one or more headers. To prevent thermally-induced warpage of these grids it is essential that one be able to detect inhomogeneities in the cooling. Due to the very strong thermal coupling between adjacent cooling lines and the concomitant rapid equilibration times, it is not practical to make such measurements in a direct manner with a contact thermometer. We have developed a technique whereby we send a burst of hot water through an initially cool grid, followed by a burst of cool water, and record the transient thermal behavior usng an infrared television camera. This technique, which would be useful for any system with cooling paths that are strongly coupled thermally, has been applied to a number of sources built for the PLT and PDX tokamaks, and has proven highly effective in locating cooling deficiencies and blocked capillary tubes

Several atomic-physics issues connected with the use of neutral beams in fusion experiments

Energetic neutral beams are used for heating and diagnostics in present magnetic fusion experiments. They are also being considered for use in future large experiments. Atomic physics issues are important for both the production of the neutral beams and the interaction of the beams and the plasma. Interest in neutral beams based on negative hydrogen ions is growing, largely based on advances in producing high current ion sources. An extension of the negative ion approach has been the suggestion to use negative ions of Z > 1 elements, such as carbon and oxygen, to form high power neutral beams for plasma heating