Plasma and Fusion Research

Volume 2, S1110 (2007)

Regular Articles

Comparison between Laser Thomson Scattering and Spectroscopic Measurements in Low Temperature Helium Plasmas in Divertor/Edge Simulator MAP-II

Filippo SCOTTI, Shinichiro KADO¹⁾, Atsushi OKAMOTO²⁾, Taiichi SHIKAMA, Yosuke KUWAHARA, Kiminori KURIHARA, Kyu-Sun CHUNG³⁾ and Satoru TANAKA

School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
1): High Temperature Plasma Center, The University of Tokyo, Kashiwa 277-8568, Japan
2): School of Engineering, Tohoku University, Sendai 980-8579, Japan
3): Electric Probe Applications Lab (ePAL), Hanyang University, Seoul 133-791 Korea

(Received 4 December 2006 / Accepted 8 May 2007 / Published 20 November 2007)

Abstract

Electron temperature and density measurements of low temperature Helium plasmas are performed in the divertor/edge plasma simulator MAP-II, by means of Laser Thomson Scattering (using a ND:YAG Laser, a double monochromator and an ICCD detector) and optical emission spectroscopy (using a spectrometer and a CCD detector). The recent upgrades of our LTS system (reduction of the level of stray light and reduction of the band width of the notch filter) allowed the measurement of temperatures as low as 0.1 eV and the investigation of Electron Ion Recombination (EIR) processes in He plasma. Spatial profiles of electron temperature and density along the plasma column have been taken moving the plasma recombination front across the measurement point by controlling the gas pressure from 80 to about 145 mTorr. A comparison between LTS results and spectroscopic analysis based on a He I CR model including radiation trapping is shown in order to confirm the consistency of the diagnostics. CR model results, obtained fitting the excited state populations with principal quantum number n = 3,4, are consistent with those from LTS. The discrepancies are found to be attributable to the mixing of the ionization and recombination regimes over the line of sight of the optics.

Keywords

Thomson scattering, CR model, divertor, detached plasma, recombining plasma, electron ion recombination (EIR) process

DOI: 10.1585/pfr.2.S1110

Full Text

PDF format (1.3Mbytes) PDF Download

References

[1] S.I. Krasheninnikov, A.Y. Pigarov and D.J. Sigmar, Phys. Rev. Lett. A 214, 285 (1996).
[2] S. Kado, H. Kobayashi, T. Oishi and S. Tanaka, J. Nucl. Mater. 313-316, 754 (2003).
[3] A. Okamoto, S. Kado, S. Kajita and S. Tanaka, Rev. Sci. Instrum. 76, 116106 (2005).
[4] F. Scotti, S. Kado et al., Plasma Fusion Res. 1, 054 (2006).
[5] S. Kado, Y. Iida, S. Kajita et al., J. Plasma Fusion Res. 81, 810 (2005).
[6] T. Fujimoto, J. Quant. Spectrosc. and Radiat. Tranf. 21, 439 (1979).
[7] M. Goto, J. Quant. Spectrosc. and Radiat. Tranf. 76, 331 (2003).
[8] M. Otsuka, R. Ikee and K. Ishii, J. Quant. Spectrosc. Radiat. Transf. 21, 41 (1979).
[9] Y. Iida, S. Kado et al., J. Plasma Fusion Res. SERIES 7, 123 (2006).
[10] B. Schweer, G. Mank, A. Pospieszczyk, B. Brosda and B. Pohlmeyer, J. Nucl. Mater. 196-198, 174 (1992).
[11] S. Kajita, N. Ohno et al., Phys. Plasmas 13, 013301 (2006).

This paper may be cited as follows:

Filippo SCOTTI, Shinichiro KADO, Atsushi OKAMOTO, Taiichi SHIKAMA, Yosuke KUWAHARA, Kiminori KURIHARA, Kyu-Sun CHUNG and Satoru TANAKA, Plasma Fusion Res. 2, S1110 (2007).