Optical thru X

We outline the basic concepts of the superconducting tunnel-junction detectors (STJs) and the performance limits. The state of present development is presented, along with projections for future developments. The performance approaches the limit due to intrinsic statistics for backtunneling devices, for photon energies E d 1 keV. The performance should soon approach those limits for energies above 1 keV now that the interaction of device properties and amplifier noise, most relevant in that higher energy range, has become understood. Present performance provides a spectral resolving power of E/DE = 25 for the STJ itself at 5 eV, and E/DE = 400 at 6 keV. Count rates e 5,000 s-1 with little degradation of energy resolution have been demonstrated. Further improvement of resolution is expected, with a large numbers of pixels. An STJ camera with 36 pixels has been already demonstrated by ESA researchers on the William Herschel Telescope. Applications are reviewed in a separate presentation by A. Peacock.[1]