Development of alpha particle measurement method by beam neutralization method

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As a realistic and promising method to diagnose alpha particles produced in a DT self-sustaining burning plasma, a "beam probe charge exchange system" was designed applicable to the DT experiments on International Thermonuclear Experimental Reactor (ITER). This method can achieve the desired S/N level if the incident ground state He^0 beam is produced through an auto-detachment of an 1-2 MeV He^- beam of 10 mA. Considering the conversion efficiency from He^+ to He^-, a strong focusing He+ beam was designed and constracted. A beam current of more than 2 A was obtained at acceleration voltages of 20-25 kV with a beam radius about 2cm at the designed beam waist, where a conversion alkali-vapor cell would be located. For the He^0 production, a test stand device was built and a ground state He^0 beam was successfully generated through the "free flight method". In summary, the principle and the engineering feasibility of "beam probe charge exchange system" has been proved.