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Progress in the development of a RF Driven D- Ion Source for ITER NBI
P. McNeely, H.D. Falter, U. Fantz, P. Franzen, B. Heinemann, W. Kraus, Ch. Martens,
R. Riedl, E. Speth
Max-Planck-Institut fur Plasmaphysik, EURATOM Association, Postfach 1533, D-85740
Garching, Germany
Abstract: Research and development has been going on for the past two years under a contract with EFDA to develop a RF driven ion source as an alternative to the current ITER reference design arc source based on the KAMABOKO sources developed at JAERI. This paper will detail the developments that have taken place on the BATMAN test facility since the start of 2005. During this time period the Type VI-1 RF ion source[1] has routinely reached or exceeded the ITER design requirements that are not precluded by technical limitations of the test facility.
The test facility has a 150 kW RF generator capable of 10 second operation. The high voltage is provided by the central power-supply group of IPP. The voltage and current is limited due to the 750 ohm voltage divider to 30 kV, 40 A for 4 seconds. The voltage divider is used to provide both extraction and acceleration voltage, but has the limitation of not
allowing independent variation of their values. The main vacuum tank is pumped by Ti pumps and in which is mounted the calorimeter. The calorimeter is a water-cooled copper panel which has specially designed thermally isolated areas which are read by thermocouple. Software allows for an evaluation of the power on the calorimeter both from the change in water temperature and from a fit to the thermocouple profiles. Recently added is an array of optic fibres, which allow for Hƒ¿ spectroscopy of the negative ion beam. The ion source has a number of diagnostics mounted on it either specifically for an experimental campaign or routinely in operation [2]. In addition the walls of the expansion body are designed to accept
external magnet holders so that the effect of magnetic confinement can be studied easily. Control of the test facility is via a computer controlled Simatic S7 system and the data is collected via a CAMAC based DAQ and analysed and displayed via in house developed software.
This paper will cover four topics: the current status of results from BATMAN as compared to the ITER requirements, the results of our investigations in to the effects of magnetic confinement on extracted ion current, a discussion on our empirically derived process to maximise negative ion current, and finally the new Hƒ¿ beam spectroscopy.
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Synopsis (pdf)