Radiation from thin, structured targets (CERN NA63)

Experimental results from the CERN NA63 experiment concerning radiation from thin, structured targets will be presented. When the targets are thin, the LPM effect on the bremsstrahlung vanishes, and other mechanisms such as the TSF effect (Ternovskii, Shul'ga, Fomin) and interference from the thin plates come in to the scene. The interference originates from an interplay between the formation length of photons and the geometry of the target. Experiments performed up to now with projectile energies of the order of 100GeV show that both theories can explain the excess in the soft part of the radiation as long as each thin target acts separately. To get a detailed description of the observations new experiments are planned which will concentrate on the very soft part of the spectrum.