| R. Gobin, O. Delferrière, R. Ferdinand, F. Harrault,
CEA/Saclay, DSM/DAPNIA, 91191 Gif sur Yvette, France
K. Benmeziane,
CEA/Saclay and LPGP Paris-Sud, Orsay
G. Gousset,
LPGP (Associé au CNRS), Université de Paris-Sud, 91405 Orsay Cedex, France
J. D. Sherman,
LANL, Los Alamos, N.M. 87 545, USA |
ECR plasma generators have demonstrated their efficiency, reproducibility and long life time for the
production of light positive ions like protons or deuterons. These sources generally work in CW mode. A new
2.45 GHz ECR test stand based on a pure volume H- ion production is currently under development. This
negative ion source is working in pulsed mode, 1ms at 10 Hz. The first H- ions have been observed at the
beginning of 2002 with a poor efficiency. Only a few µA were produced. To avoid negative ions destruction by
non absorbed microwave close to the extraction aperture, a stainless steel grid was installed in the rectangular
plasma chamber. As a result, the chamber is now effectively separated in 2 zones, the ECR plasma generator
and the H- production zone. By plotting the extracted current versus the production zone length, the H- ion
intensity reached more than 100 µA with the grid located 25 mm from the aperture. A voltage difference of the
order of ten volts can be applied between the two parts of the plasma chamber in order to modify the electron
energy entering the production zone. In parallel, a theoretical approach has been undertaken to improve the
knowledge of electron-gas interaction.
This work is supported by the European Commission under contract n°: HPRI-CT-2001-50021. |
