Characterization of a Transition-Edge Sensor for the ALPS II Experiment

The ALPS II experiment, Any Light Particle Search II at DESY in Hamburg, will look for light (m< 10-4 eV) new fundamental bosons (e.g., axion-like particles, hidden photons and other WISPs) in the next years by the mean of a light-shining-through-the-wall setup. The ALPS II photosensor is a Transition-Edge Sensor (TES) optimized for lambda = 1064 nm photons. The detector is routinely operated at 80 mK, allowing single infrared photon detections as well as non-dispersive spectroscopy with very low background rates. The demonstrated quantum efficiency for such TES is up to 95% at lambda =1064 nm. For 1064 nm photons, the measured background rate is < 10-2 sec-1 and the intrinsic dark count rate in a dark environment was found to be of 1,0.10-4 sec-1. Latest characterization results are discussed.