Plasma and Fusion Research
Volume 2, S1119 (2007)
Regular Articles
- Consorzio RFX, Associazione EURATOM-ENEA sulla fusione, C.so Stati Uniti 4 35127, Padova, Italy
- 1)
- Dipartimento di Fisica, Università di Padova, Padova, Italy
Abstract
In the reversed Field Pinch Experiment RFX-mod a Gas Puffing Imaging Diagnostic (GPID) is used to investigate the turbulence of the edge plasma. The system consists of a gas puffing nozzle and 32 optical channels to measure the HeI (668 nm) line emission. The lines of sight are arranged into three fans intersecting each other in an area normal to the main magnetic field. The diagnostic system provides an analogue bandwidth of 2 MHz and all channels are simultaneously sampled at 10 MSamples/s for the whole discharge duration (350 ms). Different inversion techniques have been applied to the data in order to obtain a 2D tomographic reconstruction of the light emission pattern from the line integrals. Comparison shows that the most suitable method is based on 2D spatial Fourier expansion, applying the Singular Value Decomposition technique with regularisation. The high sampling time allows to obtain a 2D image every 100 ns. It is found that emission structures (“blobs”) emerge from the background turbulence; a characterisation is given by computing the energy of the Fourier modes.
Keywords
edge turbulence, electrostatic structure, gas puff imaging, tomographic reconstruction, reversed field pinch
Full Text
References
- [1] B.A. Carreras, IEEE Trans. Plasma Sci. 25, 1281 (1997).
- [2] B.K. Jha et al., Phys. Rev. Lett. 69, 1375 (1992).
- [3] V. Antoni et al., Phys. Rev. Lett. 87, 045001 (2001); M. Spolaore et al., Phys. Rev. Lett. 93, 215003 (2004).
- [4] G. Rostagni, Fusion Eng. Des. 25, 301 (1995); P. Sonato et al., Fusion Eng. Des. 66-68, 161 (2003).
- [5] R.J. Maqueda et al., Rev. Sci. Instrum. 72, 931 (2001); S.J. Zweben et al., Phys. Plasmas 9, 1981 (2002).
- [6] R. Cavazzana et al., Rev. Sci. Instrum. 75, 4152 (2004).
- [7] M. Agostini, R. Cavazzana, P. Scarin, G. Serianni, Rev. Sci. Instrum. 77, 10E513 (2006).
- [8] F. Natterer, The mathematics of computerized tomography (Stuttgart, Teubner, 1986).
- [9] V. Antoni et al., Phys. Rev. Lett. 79, 4814 (1997).
- [10] P.C. Hansen, SIAM J. Sci. Statist. Comput. 11, 503 (1990).
- [11] P.C. Hansen, SIAM J. Sci. Statist. Comput. 13, 1142 (1992).
- [12] A.N. Tikhonov, Soviet. Math. Dokl. 4, 1035 (1963).
- [13] P.C. Hansen, SIAM Review 34, 561 (1992).
- [14] P.C. Hansen and D.P.O'Leary, SIAM J. Sci. Statist. Comput 14, 1487 (1993).
- [15] F. Benyah and L.S. Jennings, J. Austral. Math. Soc. B 40(E), E138 (1998).
- [16] P. Franz et al., Nucl. Fusion 41, 695 (2001).
This paper may be cited as follows:
Gianluigi SERIANNI, Roberto CAVAZZANA, Matteo AGOSTINI and Paolo SCARIN, Plasma Fusion Res. 2, S1119 (2007).