Superconducting electronics requirements for single-photon, energy resolving detectors

Development of single photon sensors capable of determining the energy ("color") of each photon incident on a pixelated focal plane in real time is a central activity of many groups worldwide developing state-of-the-art hardware for the space astrophysics community. Terrestrial applications in materials analysis are also being targeted. The most successful class of approaches uses "hot-electron" microbolometers in which the energy of the photon elevates the electronic temperature in a metallic absorber and a dedicated thermometer measures this excursion. In a class of devices called thermoelectric microbolometers the temperature sensor utilizes the Seebeck effect. Estimates of theoretical performance for a complete megapixel array are quite positive and the prototype single-pixel devices are under test. Superconducting electronics is a critical part of the signal acquisition chain. Three different types of SQUID-array amplifiers coupled to our detector pixels have been tested. The parameters of optimized SQUID-array preamplifiers are discussed.