A TES development and test facility at Cardiff, and a solution to the optical saturation problem of superconducting bolometers

The Astronomical Instrumentation Group at University of Cardiff is already a UK center for submillimetre bolometric detector testing. The next generation of submillimetre astronomical instrumentation will incorporate arrays of transition-edge sensor (TES) bolometers. With the recently expanded facilities and personnel, the University of Cardiff is poised to become a UK centre for TES development and testing. We have undertaken a coordinated programme to develop TES simulation and test capabilities. One aspect of the programme is to address the problem of saturation of TES bolometers at high optical loads. We have developed a "tunable-G" device, which can vary its thermal conductance whilst in operation. For infrastructure, several sub-Kelvin cryogenic testbeds have been specifically designed to suit the requirements of testing submillimetre TES development bolometers. A description of our tunable-G device to solve the optical saturation problem will be given along with a description of the test facilities available at Cardiff