Cryogenic IR/Optical/UV fast spectrophotometers for the study of time-variable astronomical sources

Our detectors are superconducting Transition-Edge Sensors (TESs) that have been designed for photon counting in the energy (wavelength) range of 0.5 eV (2.5 mum) to 10 eV (124 nm). Our design consists of a 6 x 6 array of 20 mum by 20 mum pixels, of which four were operated simultaneously at count rates exceeding 30 K-counts/pixel. Each photon is time-tagged to 0.4 mus using a GPS signal processor, and the energy is determined to approximately 0.15 eV FWHM. These results are the best achieved for an energy dispersive spectrometer (EDS) in the optical range. We discuss the detector design and operation, optical coupling, and high-rate data acquisition system. In addition, we discuss the next step toward detectors with improved light collection and higher energy resolution. We also present recent results from latest application of our fast spectrophotometers to the study of highly time-variable sources using the 2.7 m telescope at the McDonald Observatory.