Design of Faraday Cup Ion Detectors 
Built by Thin Film Deposition

Authors:  G.A. Szalkowski, D.S. Darrow, F.E. Cecil


Abstract:  Thin film Faraday cup detectors can provide measurements of fast ion loss from magnetically confined fusion plasmas.  These multilayer detectors can resolve the energy distribution of the lost ions in addition to giving the total loss rate.  Past detectors were assembled by stacking discrete foils and insulating sheets together.  Outlined here is a design methodology for those detectors using thin film deposition.  The intention is to use detectors created by this method on JET and NSTX-U.  The detectors will consist of alternating layers of aluminum and silicon dioxide.  The thicknesses of the films have been designed to isolate energies of interest.  Thin film deposition offers the advantage of relatively simple and more mechanically robust construction compared to other methods, as well as precise control of film thickness.  Furthermore, this depositional fabricaton technique places the layers in intimate thermal contact, providing for three dimensional conduction and dissipation of the ion-produced heating in the layers rather than the essentially two dimensional heat conduction in the discrete foil stack implementation.
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Submitted to:  Review of Scientific Instruments
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Download PPPL-5179 (pdf 2.2 MB 11 pp)
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