Supersonic neutral particle beam for tokamak plasma diagnostics

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The main objective of this research is to develop a supersonic helium atomic beam method for diagnosis in the edge region in magnetic confined fusion plasmas by use of spectroscopic techniques. The outline of the present research results is as follows :1.Numerical study of atomic processes of the supersonic helium atomic beam in the plasma edges : The excitation and ionization processes of the helium atomic beam injected into a middle size tokamak plasma (the JFT-2M tokamak at JAERI) was numerically studied in the plasma edges by using a set of the rate equations for the populations of the excited and ionic states of helium. It was shown that the electron density and temperature could be determined from intensity measurements of two different pairs of He I lines, and also that spatial distribution of the electric field induced in the edges could be measured by using a laser-induced fluorescence technique. 2.Atomic collision process between ionized helium atom and hydrogen molecule in plasmas : A numerical study on the basis of a collisional-radiative model was performed on a charge-exchange process between He^<++> and H_2, which could play an important role in the divertor plasmas. 3.A fast numerical calculation method of the rate equation for the plasmas was developed. 4.A supersonic helium atomic beam source was constructed by using a pulsed nozzle and a set of skimmer in a small size vacuum chamber. Spectroscopic measurements revealed this beam could be applicability to torus plasmas. 5.A helium metastable atomic beam was produced using a ECR plasma source. 6.A laser-induced fluorescence method for measurement of electric field distribution in magnetically confined plasmas was developed taking account of the effect of the magnetic field.