Fluctuation measurements on the Wendelstein 7-AS stellarator by means of repetitive lithium laser blow-off

We present a method of beam emission spectroscopy (BES) using an atomic Li beam that is generated by means of laser blow-off for the investigation of electron density fluctuations in the edge and scrape-off layer plasmas of fusion devices. We discuss the operational limits of this technique and compare them to those of other atomic Li beam diagnostics. Furthermore, we apply this method to different Wendelstein 7-AS discharges and study the influence of the line integrated electron density and the direction of the main magnetic field on the fluctuations inside and outside the last closed flux surface, and especially on their movement. The information we obtain on the influence of the main magnetic field on the fluctuations gives some insight into the possible origin of certain features of their spatial structure.

[1]  G. Ross,et al.  Use of laser‐ablated fast particle beams for the measurement of ne and Te profiles in the TEXTOR boundary layer , 1988 .

[2]  N. Bretz.  Diagnostic instrumentation for microturbulence in tokamaks , 1997 .

[3]  L. Wirtz,et al.  Laboratory studies of metal atomic beams produced by means of UV-laser radiation , 1997 .

[4]  M. Endler,et al.  Density, temperature, and potential fluctuation measurements by the swept Langmuir probe technique in Wendelstein 7‐AS , 1994 .

[5]  Characterization of the frequency ranges of the plasma edge fluctuation spectra , 1999 .

[6]  S. Zoletnik,et al.  Determination of electron density fluctuation correlation functions via beam emission spectroscopy , 1998 .

[7]  F. J. Smith,et al.  Recommended Data on the Electron Impact Ionization of Atoms and Ions: Fluorine to Nickel , 1988 .

[8]  M. E. Shaer,et al.  Temporal behavior of the electron density profile in the scrape-off layer of neutral-beam-heated ASDEX plasmas , 1984 .

[9]  J. Schweinzer,et al.  DATABASE FOR INELASTIC COLLISIONS OF LITHIUM ATOMS WITH ELECTRONS, PROTONS, AND MULTIPLY CHARGED IONS , 1999 .

[10]  G. Kocsis,et al.  Investigation of laser blow-off atomic beams by electron impact excitation , 1991 .

[11]  J. F. Friichtenicht.  Laser‐generated pulsed atomic beams , 1974 .

[12]  A. Wootton,et al.  Fluctuations and anomalous transport in tokamaks , 1990 .

[13]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[14]  G. Kocsis,et al.  Absolute measurement of velocity distribution of neutrals in sodium laser blow-off beam , 1990 .

[15]  J. L. Cecchi,et al.  System for rapid injection of metal atoms into plasmas , 1975 .

[16]  Paul,et al.  Observation of a localized transition from edge to core density turbulence in the TFTR tokamak. , 1993, Physical review letters.

[17]  Douglass E. Post,et al.  Steady-state radiative cooling rates for low-density, high-temperature plasmas , 1977 .

[18]  J. Bendat,et al.  Random Data: Analysis and Measurement Procedures , 1971 .

[19]  T. Morisaki,et al.  Numerical study of neutral beam probe spectroscopy for edge fluctuation measurements , 1990 .

[20]  S. Zoletnik,et al.  Density fluctuation phenomena in the scrape-off layer and edge plasma of the Wendelstein 7-AS stellarator , 1999 .

[21]  W. Hecq,et al.  Low energy neutral beam production by laser vaporization of metals , 1980 .

[22]  G. Ross,et al.  Density determination in the TEXTOR boundary layer by laser‐ablated fast lithium atoms , 1988 .

[23]  G. Ross,et al.  Recent developments for plasma edge diagnostics using atomic beams , 1989 .

[24]  G. Kocsis,et al.  Transport of impurity ions along the field lines in magnetized plasma , 1996 .

[25]  Bill Scott,et al.  E x B Shear Flows and Electromagnetic Gyrofluid Turbulence , 1999 .

[26]  P. Liewer.  Measurements of microturbulence in tokamaks and comparisons with theories of turbulence and anomalous transport , 1985 .

[27]  B. Schweer,et al.  Space resolved fluctuations of electron density measured by means of two thermal Li-beams in TEXTOR-94 , 1999 .

[28]  M. Endler,et al.  The spatial structure of edge fluctuations in the Wendelstein 7-AS stellarator , 2002 .

[29]  J. Drake,et al.  Three‐dimensional fluid simulations of tokamak edge turbulence , 1996 .

[30]  L. Giannone,et al.  Measurements and modelling of electrostatic fluctuations in the scrape-off layer of ASDEX , 1995 .

[31]  J. F. Friichtenicht,et al.  Atomic and ionic beam source utilizing pulsed laser blow off , 1976 .