HYDROGEN AND DEUTERIUM ION SPECIES MIX AND INJECTED NEUTRAL BEAM POWER FRACTIONS OF THE TEXTOR-PINIS FOR 20-60 KV DETERMINED BY DOPPLER-SHIFT SPECTROSCOPY

The ion species fractions of the multimegawatt neutral beam ion sources for Torus Experiment for Technological Oriented Research (TEXTOR) were determined by H(alpha)/D(alpha)-light Doppler shift spectroscopy. The ion sources are modified Joint European Torus (JET) plug in neutral injectors (PINIs) with a three-grid acceleration system and a magnetic field in the plasma box produced by permanent magnets in checkerboard arrangement. The ion species mix of the extracted beam was measured for energies of 20-60 keV and beam currents of 13-100 A of hydrogen and deuterium produced by the two ion sources (PINI) mounted on the neutral beam injectors of TEXTOR. The maximum H+/D+ fraction at full power operation is 66%-69%. No significant difference between the two ion sources was found. The results of the hydrogen ion species mix are in good agreement with prior optical and momentum analysis made on the NI-Testbed. The additionally measured dependence of the extracted species mix from the source gas pressure is small in the pressure range above 3 mubar where the ion sources are usually operated. Measurements over the beam pulse length from 0.1 to 3 s show no change in the species mix. For calculating the deuterium ion species mix at low energies, several cross sections for H(alpha)-light excitation, charge exchange, and dissociation available from the literature were extrapolated to about 3 keV per nucleon. The correction factors used for calculating the ion species fraction from the ratio of the relevant integrated Doppler shift light peaks are given as a function of the gas target density in the neutralizer and of the energy per nucleon. The optical spectrometers specially designed and constructed for neutral beam H(alpha)-light Doppler shift spectroscopy give a sufficient resolution of 1 angstrom and enough light intensity also at smaller beam energies and currents. The subsequent injected neutral beam power fractions H-0(E), H-0(E/2), and H-0(E/3) and the molecular fractions H-2(0)(E) and H-2(0)(2/3E) are given as a function of acceleration voltage considering the beam line transmission and 90% of equilibrium gas target density. The injected full energy neutral beam component at 55 keV is for hydrogen 48% or 0.7 MW and 66% or 1.1 MW for deuterium.