Design of the ALPS II optical system

The Any Light Particle Search II (ALPS II) is an experiment currently being built at DESY in Hamburg, Germany, that will use a light-shining-through-a-wall (LSW) approach to search for axion-like particles. ALPS represents significant step forward these types of experiments as it 24 superconducting dipole magnets, along with dual, high-finesse, 122 m long optical cavities. This paper gives the first comprehensive recipe realization idea, proposed over 30 years ago, cavities before and after wall increase power regenerated photon signal. designed achieve sensitivity coupling between particles photons down g???=2×10?11GeV?1 masses below 0.1 meV, more than three orders magnitude beyond previous laboratory experiments. layout main components define are discussed plans reaching design sensitivity. An accompanying (Hallal et al., (2021)) offers in-depth description heterodyne detection scheme, two independent systems be implemented II.