Development of a compact thermal lithium atom beam source for measurements of electron velocity distribution function anisotropy in electron cyclotron resonance plasmas.

The anisotropy of the electron velocity distribution function (EVDF) in plasmas can be deduced from the polarization of emissions induced by anisotropic electron-impact excitation. In this paper, we develop a compact thermal lithium atom beam source for spatially resolved measurements of the EVDF anisotropy in electron cyclotron resonance (ECR) plasmas. The beam system is designed such that the ejected beam has a slab shape, and the beam direction is variable. The divergence and flux of the beam are evaluated by experiments and calculations. The developed beam system is installed in an ECR plasma device with a cusp magnetic field, and the LiI 2s-2p emission (670.8 nm) is observed in low-pressure helium plasma. The two-dimensional distributions of the degree and direction of the polarization in the LiI emission are measured by a polarization imaging system. The evaluated polarization distribution suggests the spatial variation of the EVDF anisotropy.

[1]  F. Skiff,et al.  Measurements of parallel electron velocity distributions using whistler wave absorption. , 2012, The Review of scientific instruments.

[2]  T. Hatae,et al.  Principles for local measurement of anisotropic electron temperature of plasma using incoherent Thomson scattering , 2011 .

[3]  T. Lunt,et al.  ECRH-assisted plasma start-up with toroidally inclined launch: multi-machine comparison and perspectives for ITER , 2011 .

[4]  T. Maekawa,et al.  Rapid current ramp-up by cyclotron-driving electrons beyond runaway velocity. , 2010, Physical review letters.

[5]  Jik-Soo Kim,et al.  ECH pre-ionization and assisted startup in the fully superconducting KSTAR tokamak using second harmonic , 2009 .

[6]  M. Lennholm,et al.  First experiments of plasma start-up assisted by ECRH on Tore Supra , 2008 .

[7]  Mizuki Sakamoto,et al.  Two-dimensional density profile measurement with a sheet thermal Li beam on CPD , 2007 .

[8]  R. Prater,et al.  Second harmonic electron cyclotron pre-ionization in the DIII-D tokamak , 2007 .

[9]  D. C. Griffin,et al.  Generalised collisional-radiative model for light elements. A: Data for the Li isonuclear sequence , 2006 .

[10]  T. Morisaki,et al.  Simulation of sheet-shaped lithium beam probe performance for two-dimensional edge plasma measurement , 2006 .

[11]  T. Maekawa,et al.  Spontaneous formation of closed-field torus equilibrium via current jump observed in an electron-cyclotron-heated plasma. , 2006, Physical review letters.

[12]  A. Iwamae,et al.  Anisotropic electron velocity distribution in an ECR helium plasma as determined from polarization of emission lines , 2005 .

[13]  T. Oikawa,et al.  Electron cyclotron heating assisted startup in JT-60U , 2005 .

[14]  P. Mertens,et al.  Results from a double Li-beam technique for measurement of both radial and poloidal components of electron density fluctuations using two thermal beams , 2005 .

[15]  S. Kado,et al.  The Effect of Superthermal Electrons on Mach Probe Diagnostics , 2004 .

[16]  D. C. Griffin,et al.  Electron-impact excitation of Li to high principal quantum numbers , 2003 .

[17]  M. Hasuo,et al.  Zeeman effect on disalignment of excited atoms by radiation re-absorption: neon 2p2 atoms in a discharge plasma , 2003 .

[18]  M. G. O'Mullane,et al.  Dielectronic recombination data for dynamic finite-density plasmas - I. Goals and methodology , 2003, astro-ph/0304273.

[19]  D. Reiter,et al.  Collision processes in low-temperature hydrogen plasmas , 2003 .

[20]  Hitoshi Tanaka,et al.  Electron Cyclotron Resonance Plasma Produced with a Closed Spheroidal Electron Cyclotron Resonance Surface in a Simple Cusp Field , 1999 .

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

[22]  T. Fujimoto.  Plasma polarization spectroscopy , 1999 .

[23]  J. Schweinzer,et al.  CROSS SECTIONS FOR COLLISION PROCESSES OF Li ATOMS INTERACTING WITH ELECTRONS, PROTONS, MULTIPLY CHARGED IONS, AND HYDROGEN MOLECULES , 1997 .

[24]  T. Osborne,et al.  Investigation of the formation of a fully pressure‐driven tokamak* , 1994 .

[25]  F. Skiff,et al.  Measurements of electron parallel‐momentum distributions using cyclotron wave transmission* , 1993 .

[26]  Y. Uesugi,et al.  Laser blow‐off lithium beam probing with high temporal resolution for edge plasma diagnostics , 1993 .

[27]  T. Sakoda,et al.  Thomson scattering measurements of electron temperature and density in an electron cyclotron resonance plasma , 1993 .

[28]  A. Unterreiter,et al.  Reconstruction of plasma edge density profiles from Li I (2s-2p) emission profiles , 1992 .

[29]  S. Takamura,et al.  Edge plasma density reconstruction for fast monoenergetic lithium beam probing , 1992 .

[30]  Chaker,et al.  Electron distribution anisotropy in laser-produced plasmas from x-ray line polarization measurements. , 1992, Physical review letters.

[31]  A. Komori,et al.  Reconstruction of Edge-Plasma Density Profiles by Neutral Beam Probe Spectroscopy , 1991 .

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

[33]  R. Kirkwood,et al.  Measurement of suprathermal electron confinement by cyclotron transmission , 1990 .

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

[35]  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 .

[36]  N. Wild,et al.  Directional velocity analyzer for measuring electron distribution functions in plasmas , 1983 .

[37]  E. Haug.  Electron impact polarization of X-ray lines from hydrogen-like ions during solar flares , 1981 .

[38]  Y. Kawasumi,et al.  Plasma diagnostics by neutral beam probing , 1978 .

[39]  S. Kumar,et al.  Glauber calculation of the polarization of the 2p→2s resonance line of lithium , 1976 .

[40]  H. Aikawa.  The Measurement of the Anisotropy of Electron Distribution Function of a Magnetized Plasma , 1976 .

[41]  Chih−shun Lu,et al.  Mass determination with piezoelectric quartz crystal resonators , 1975 .

[42]  A. Gallagher,et al.  Electron excitation of the lithium 6708-Å resonance line , 1974 .

[43]  S. K. Joshi,et al.  On the polarization of the resonance lines of lithium and sodium atoms by electron impact , 1973 .

[44]  L. C. Johnson.  APPROXIMATIONS FOR COLLISIONAL AND RADIATIVE TRANSITION RATES IN ATOMIC HYDROGEN. , 1972 .

[45]  N. Feautrier.  POLARIZATION OF LITHIUM ATOM RESONANCE LINES EXCITED BY ELECTRON IMPACT. , 1970 .

[46]  E. Karule.  POLARIZATION OF LITHIUM AND SODIUM ATOM RESONANCE LINES EXCITED BY ELECTRON IMPACT. , 1970 .

[47]  M. Rudge,et al.  On an approximation in scattering theory , 1970 .

[48]  A. Taylor,et al.  The scattering of electrons by lithium atoms , 1969 .

[49]  W. Lotz,et al.  Electron-impact ionization cross-sections and ionization rate coefficients for atoms and ions from hydrogen to calcium , 1968 .

[50]  H. Kleinpoppen,et al.  Polarization of atomic line radiation , 1967 .

[51]  Wolfgang L. Wiese,et al.  ATOMIC TRANSITION PROBABILITIES. VOLUME 1. HYDROGEN THROUGH NEON , 1966 .

[52]  W. Lotz,et al.  An empirical formula for the electron-impact ionization cross-section , 1966 .

[53]  R. Latter,et al.  Electron Radiative Transitions in a Coulomb Field , 1961 .

[54]  Louis C. Green,et al.  Oscillator Strengths and Matrix Elements for the Electric Dipole Moment for Hydrogen. , 1957 .