Determination of neutral‐beam‐power profiles: Divergences and power fractions of the species from measurements inside the torus of TEXTOR

A set of experiments was carried out with TEXTOR neutral beams inside the torus to obtain detailed knowledge about the beam for later use in experiments such as charge exchange recombination spectroscopy and for energy deposition calculations. A segmented graphite plate and an infrared camera were used to gain information about the total beam power profile for different beams (H, D, He) and particle energies. Spatially resolved measurements of Doppler‐shifted Hα line intensities were used to calculate the relative widths and fractional powers of the three beam species (for H and D) at different energies (this report mainly deals with this method). By these measurements the beams are fully characterized so that charge exchange spectroscopy could be employed to yield impurity concentration profiles in spite of an extended beam and lines of sight not tangential to the plasma surfaces. The results for a 50 keV hydrogen beam are also taking into account the calorimetric measurements inside the injector box. The beamlets are composed of two Gaussian profiles. The broader profile (divergence of 3° and a power fraction of 30%) is mainly scraped off in the injector itself. The composition of the smaller profile, which almost exclusively determines the power to TEXTOR, is calculated from the measured results. The power fractions for the three species (E, E/2, E/3) are 50%, 37.6% and 12.4% respectively. The divergences horizontally are 0.87, 0.92, 0.95 degrees and vertically 0.91, 0.98, 1.02 degrees respectively. The exact position of the beam inside TEXTOR and its direction are determined as well.