Analysis procedure for calculation of electron energy distribution functions from incoherent Thomson scattering spectra

Incoherent Thomson scattering (ITS) provides a nonintrusive diagnostic for the determination of one-dimensional (1D) electron velocity distribution in plasmas. When the ITS spectrum is Gaussian its interpretation as a three-dimensional (3D) Maxwellian velocity distribution is straightforward. For more complex ITS line shapes derivation of the corresponding 3D velocity distribution and electron energy probability distribution function is more difficult. This article reviews current techniques and proposes an approach to making the transformation between a 1D velocity distribution and the corresponding 3D energy distribution. Previous approaches have either transformed the ITS spectra directly from a 1D distribution to a 3D or fitted two Gaussians assuming a Maxwellian or bi-Maxwellian distribution. Here, the measured ITS spectrum transformed into a 1D velocity distribution and the probability of finding a particle with speed within 0 and given value v is calculated. The differentiation of this probability function is shown to be the normalized electron velocity distribution function. (C) 2003 American Institute of Physics.

Thomson scattering system at the Tokyo electron beam ion trap

A Thomson scattering system has been installed at the Tokyo electron beam ion trap for probing characteristics of the electron beam. A YVO4 green laser beam was injected antiparallel to the electron beam. The image of the Thomson scattering light from the electron beam has been observed using a charged-coupled device camera. By using a combination of interference filters, the spectral distribution of the Thomson scattering light has been measured. The Doppler shift observed for the scattered light is consistent with the beam energy. The beam radius dependence was investigated as a function of the beam energy, the beam current, and the magnetic field at the trap region. The variation of the measured beam radius against the beam current and the magnetic field were similar to those in Herrmann's prediction. The beam radius as a function of the beam energy was also similar to Herrmann's prediction but seemed to become larger at low energy. (C) 2002 American Institute of Physics.

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