A MICROWAVE PARAPHOTON AND AXION DETECTION EXPERIMENT WITH 300 dB ELECTROMAGNETIC SHIELDING AT 3 GHz

For the microwave equivalent of “light shining through the wall” (LSW) experiments, a sensitive microwave detector and very high electromagnetic shielding is required. The screening attenuation between the axion generating cavity and the nearby detection cavity should be greater than 300 dB, in order to improve over presently existing exclusion limits. To achieve these goals in practice, a “box in a box” concept was utilized for shielding the detection cavity, while a vector signal analyzer was used as a microwave receiver with a very narrow resolution bandwidth in the order of a few micro-Hz. This contribution will present the experimental layout and the results to date. MOTIVATION The axion is a hypothetical elementary particle, which emerged originally from a proposal by Peccei and Quinn, intended to solve the strong CP problem [1] in theoretical physics. The axion is neutral, only interacts weakly with matter, has a low mass (≈ 10 −4 eV /c 2 ), spin zero, and a natural decay constant (to 2 photons) in the order of 10 17 years. The axion belongs to the family of Weakly Interacting Sub-eV Particles (WISP). Another WISP, closely related to the axion is the paraphoton or hidden photon. The existence of these WISPs could not be confirmed yet and all experimental efforts to date have so far produced only exclusion results. Nevertheless there is strong motivation to advance the experimental “low energy frontier” as the axion is the most popular solution for the strong CP-problem. Many WISPs are also excellent candidates for dark matter and explain numerous astrophysical phenomena.