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Measurement of the Electron Energy Distribution Function by Langmuir Probe in an ITER like Hydrogen Negative Ion Source

B. Crowley¹, D. Homfray¹, S.J. Cox¹, D. Boilson², H P L de Esch³ and R.S. Hemsworth³

¹Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon,. OX14 3DB, UK.
²Association Euratom/DCU, Dublin City University, Dublin 9, Ireland
³Association Euratom-CEA, CEA Cadarache, F-13108, St. Paul lez Durance, France

Abstract: Determining 2 2 dV I d from a traditional Langmuir probe trace using numerical techniques is inherently noisy and generally yields poor results. We have developed a Langmuir probe system based on a method first used in the 1950’s by Boyd and Twiddy. The system measures the 2nd derivative directly. This paper presents an account of the experimental method, apparatus and software used along with some preliminary results from the KAMABOKO III source including a comparison with conventional probe methods.

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