RESUMO
A 1000 keV, 5 MW, 1000 s neutral beam injector based on negative ions is being developed in the Budker Institute of Nuclear Physics, Novosibirsk in collaboration with Tri Alpha Energy, Inc. The innovative design of the injector features the spatially separated ion source and an electrostatic accelerator. Plasma or photon neutralizer and energy recuperation of the remaining ion species is employed in the injector to provide an overall energy efficiency of the system as high as 80%. A test stand for the beam acceleration is now under construction. A prototype of the negative ion beam source has been fabricated and installed at the test stand. The prototype ion source is designed to produce 120 keV, 1.5 A beam.
RESUMO
Two-dimensional phase contrast imaging (2D) installed on the large helical device (LHD) is a unique diagnostic for local turbulence measurements. A 10.6 microm infrared CO(2) laser and 6x8 channel HgCdTe 2D detector are used. The length of the scattering volume is larger than plasma size. However, the asymmetry of turbulence structure with respect to the magnetic field and magnetic shear make local turbulence measurements possible. From a 2D image of the integrated fluctuations, the spatial cross-correlation function was estimated using time domain correlation analysis, then, the integrated 2D k-spectrum is obtained using maximum entropy method. The 2D k-spectrum is converted from Cartesian coordinates to cylindrical coordinates. Finally, the angle in cylindrical coordinate is converted to flux surface labels. The fluctuation profile over almost the entire plasma diameter can be obtained at a single moment. The measurable k-region can be varied by adjusting the detection optics. Presently, k=0.1-1.0 mm(-1) can be measured which is expected region of ion temperature gradient modes and trapped electron mode in LHD. The spatial resolution is 10%-50% of the minor radius.
