K. Sato

M. Goto

T. Kobuchi

National Institute for Fusion Science (NIFS-Repository)

§45. Study of Charge-exchange Process on C6+ + H in Low Energy Collision in XUV Region Kobuchi, T., Sato, K., Goto, M. The extreme ultraviolet (XUV) spectrum of e VI has been studied in . Large Helical Device (LHD) experiment. In the wavelength region the spectrum by charge-exchange (eX) has observed during Neutral Beam Injection (NBI) plasma. In the case of ex between fully-stripped carbon ion and high energy beam (E > 100 ke V) of hydrogen atom, electron is also captured into highly-excited states n = 7, 8, 9 • • • of each H-like ions. The subsequent transitions 6 n=1 provide long wavelength spectra in visible region, which is quite useful for spectroscopic diagnostics. Though the line-of-sight of our spectrometer was placed not to cross the high-energy neutral hydrogen beam (E > 100 ke V) in NBI experiment, a strong distortion in the C VI Lyman series decrement was observed. This distinctive feature is that e VI 1 s-4p (Ly y ) line is observed as same intense as e VI 1 s-3p (Ly 8) line. Generally, intensity of Ly 8 is larger than of Ly y . This phenomenon can be attributed to a charge-exchange process in low energy collision, ~ because a character of low energy collision process is ~ shown into the observed C VI Lyman series decrement. ; This character is that the efectron is selectively · ~ captured into a single low-excited level of principal ] quantum number n of ions. In the case of ex of e 6+ ion with ground-state hydrogen atom, the capturing level is n = 4. In order to investigate the reacting region for e6+-H charge transfer collision, spatially resolved intensity measurements were tried by shot to shot brightness scan. Emission profiles of e VI Ly a and Ly 8 present hollow shape, and it is expected that the peak of radial profile of e5+ ions is nearly located at the inflection point of this intensity distribution curve. On the other hand, the emission profile of Ly y is different from the one of Ly a and Ly 8 . Using the chordal radiances, the radial intensity profiles have been determined from Abel inversion calculation, defming the vacuum magnetic surface till outside of LeFS. This result is shown in fig.1 . As expected above, it . found that the radial profiles of Ly a and Ly 8 have the same shape and peak at normalized miner radius p =0. 9. The profile of Ly y peaks at outside from the peak positions of Ly a 50 and Ly 8 . We have tried to pick up the ex component (Ly y ex) from the measured Ly y intensity. We defme I(Ly y ex) as following l(LYYcx) ~ l(Lyy)-0.26x!(Lyp), (1) where the value of 0.26 is intensity ratio of Ly y to Ly 8 calculated using Collisional-Radiative Model. The right -hand side of eqn. ( 1) represents the difference between the measured Ly y and the intensity calculated with eRM and can be related to the CX component. This emission profile of Ly y ex is also shown in Fig. 1 . This profile differs from of Ly a and Ly 8 and peaks at outside of Ly a and Ly 8. Spatially resolved measurement shows that the e 6+-H ex process occurs at peripheral region in LHD plasma. Normalized Minor Radius Fig. 1 Radial profiles of observed emission intensity of Ly a , Ly 8 and Ly y . These are calculated using Abel inversion method. Ly y ex has been estimated from the relation between Ly and Ly on eRM. 

Study of Charge-exchange Process on C6+ + H in Low Energy Collision in XUV Region

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)