Fig. 2From: Straightening of superconducting HERA dipoles for the any-light-particle-search experiment ALPS IISchematic layout of the experiment. The probability for the generation of an ALP by a photon gets increased in an optical resonator. Behind the light tight wall a second optical resonator increases the probability of re-conversion to a photon in the magnetic field. (Figure from Aaron Spector)Back to article page