Diagnostic for fast charged particles at TEXTOR-94

A diagnostic for measuring the energy spectrum of fast charged particles has been developed at TEXTOR-94. It consists of a pair of solid state silicon passivated implanted planar silicon detectors which are actively water cooled. The detectors are mounted on a manipulator and are inserted into the vacuum vessel during plasma operation. The preamplifiers are located just behind the detectors. The noise level is strongly minimized by careful grounding and rf shielding. Collimators placed in front of the detectors allow to obtain radial and pitch angle-resolved measurements. Fast particles coming from the center of the plasma are detected by one detector. The second detector can be used as a background monitor or can provide an additional measurement at another position. Orbit calculations in a realistic magnetic field predict the detection efficiency. The calculated detection efficiency shows good agreement with our experiments. The stable temperature and excellent noise immunity of our system allow to measure the energy spectrum of the 3 MeV protons and 1 MeV tritons produced by the DD fusion reactions in discharges with different heating scenarios. High resolution energy spectra are even obtained in discharges heated with injection of deuterium in a deuterium plasma.