Crystal spectroscopy and exotic atoms

Recent developments in crystal spectroscopy of X-rays emitted from exotic atoms have concentrated on the measurement of the ground state level shift and width in pionic hydrogen. An increase of the pion beam intensity, together with a sophisticated stopping technique combined with newly developed reflection spectrometers, as well as with large area focal CCD detectors, resulted in a gain of luminosity of three orders of magnitude. The potential of these achievements for improved measurement of the vacuum polarization contribution in exotic atoms is discussed. (Author)