A high-performance, high-resolution positron annihilation coincidence Doppler broadening spectrometer

We present a simple, high-performance, high-resolution, two-dimensional Doppler broadening spectrometer for positron annihilation experiments. We used a combination of two germanium detectors and a Digital Signal Processor unit as photon detection system. The coincidence circuit and data acquisition circuit are provided by a home-built system. We have investigated the background contributions, resolution and stability.