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The neutral beam injection system of ASDEX Upgrade consists of two almost identical beam lines with four sources each. The main difference is the ion source: conventional arc sources are used for the first beam line, whereas the second beam line is equipped with new RF sources. Both types of sources deliver a mixture of atomic and molecular ions of hydrogen and deuterium. Hence the injected neutral beam consists not only of full energy neutral atoms, but also of atoms with half and third energy. The distribution of the different hydrogenic particles (protons and molecular ions) in the extracted beam, the species distribution, and the distribution of the neutral hydrogen atoms with the different energies in the injected neutral beam, the power distribution, of both beam lines have been measured byHa Doppler shift spectroscopy in the neutralizers as will as in the duct between the injection box and the ASDEX Upgrade torus vessel for hydrogen and deuterium beams.
The RF sources yield a higher proton fraction than the arc sources. Accordingly, a higher fraction of full energy atoms is injected into the plasma: in the Case of 60 kV deuterium operation this amounts to about 72% of the total injected power for the RF sources, compared to about 65% for the arc sources. The agreement between the power distributions derived from the duct and the neutralizer measurements is satisfactory; the fact that the full energy fraction revealed from the duct measurements is slightly higher especially at higher energies may be related to the simplifying assumption of an infinitely thick neutralizer target in the calculations.

Additional information

Authors: FRANZEN P, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE);VOLLMER O, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE);STABLER A, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE)
Bibliographic Reference: Article: IPP-Report, 4(1998)278, 1-35
Record Number: 199910405 / Last updated on: 1999-03-19
Original language: en
Available languages: en