Possibilities for Coincidence Spectroscopy in the Scanning Transmission Electron Microscope

Applied Science

High-resolution multiposition Thomson scattering for the TJ-II stellarator

In this article, the recent installed multiposition Thomson scattering (TS) of the TJ-II stellarator is presented. Light from a pulsed ruby laser is scattered by the free electrons of the plasma and led to a spectrometer for spectral analysis. The Doppler broadened spectrum of the scattered light is analyzed with a spectrometer in the Littrow configuration, detected with a GaAsP image intensifier and recorded with two intensified charged coupled device cameras. Values of the electron temperature (T-e) in the range of 50 eV up to 4 keV can be measured at 160 spatial elements of 2.25 mm along a chord of 360 mm. First results show that the observational error for T-e is close to the expected error of similar to 10% at an electron density (n(e)) of 1 X 10(19) m(-3) using a laser energy of 8 J. (C) 1999 American Institute of Physics. [S0034-6748(99)64101-6]

Plasma Filamentation in the Rijnhuizen-Tokamak Rtp

Evidence for small scale magnetic structures in the Rijnhuizen tokamak RTP is presented. These are manifest through steps and peaks in the electron temperature and pressure, measured with multiposition Thomson scattering. During central electron cyclotron heating, several filaments of high pressure are found in the power deposition region. They live hundreds of microseconds. Near the sawtooth inversion radius a \u27\u27step\u27\u27 in the temperature profile occurs. Further out, quasiperiodic structures are observed, in both Ohmic and heated discharges

Enhanced Transport During Pellet Injection in the Rijnhuizen-Tokamak-Rtp

The evolution of the radial profiles of electron temperature and density in a tokamak plasma during ablation of an injected hydrogen pellet is studied by Thomson scattering with a resolution of 1% of the mirror plasma radius. The energy content is hardly affected until the pellet reaches the sawtooth inversion radius when strongly enhanced transport sets in throughout the plasma. Asymmetric profiles are observed. Peaks of high density are formed, one of which often develops into a density \u27\u27snake.\u27\u2

A high resolution multiposition Thomson scattering system for the Rijnhuizen Tokamak project

A high resolution multiposition Thomson scattering setup to measure the electron temperature (T-e) and density (n(e)) of a hot plasma is described. The system is operational at the Rijnhuizen Tokamak Project. Light from a high power pulsed ruby laser is scattered by the free plasma electrons and relayed to a Littrow polychromator for spectral analysis. The spectrally and spatially resolved light is detected by a GaAsP photocathode. The two-dimensional image is intensified and recorded with a charge-coupled device camera. T-e in the range of 50 eV-6 keV can be measured at 115 spatial elements of 2.6 mm length along the laser beam. The observation error is <6% at n(e)=2 X 10(19) m(-3) and smaller for higher n(e). The high resolution and accuracy enabled the observation of small scale structures in T-e and n(e). (C) 1997 American Institute of Physics

Double pulse Thomson scattering system at RTP

In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10-800 mu s, max. 2x12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator for spectral analysis. The spectrally resolved light is recorded by two ICCD detectors. Simulations show that the system sensitivity will be such that electron temperatures in the range of 100 eV-7 keV can be determined with an accuracy as good as 2%-3% for electron densities of 10(20) m(-3), With a spatial resolution down to 2.6 mm. With this diagnostic the dynamics of small scale structures in the electron temperature profile will be studied. (C) 1997 American Institute of Physics

Evidence for Small-Scale Magnetic-Structures in the Rtp Tokamak

High resolution Thomson scattering measurements of electron temperature and density in RTP show several hot filaments in the plasma centre and sharp gradients near the sawtooth inversion radius under central ECH, and structures outside the sawtooth region both in ohmic and ECH plasmas. These measurements give evidence of a complex magnetic topology. A numerical scheme is proposed which allows computation of the magnetic equilibrium with broken surfaces. Some properties of transport in a inhomogeneous medium are discussed