New UV Detector Concepts

BOLD (Blind to the Optical Light Detectors) is an international initiative dedicated to the development of novel imaging detectors for UV solar observations. It relies on the properties of wide-bandgap semiconductor materials (in particular diamond and Al-Ganitrides). This investigation is proposed in view of the Solar Orbiter UV instruments, for which the expected benefits of the new sensors, visible blindness and radiation hardness, will be highly valuable. Despite various advances in the technology of imaging detectors over the last few decades, the present UV imagers based on silicon CCDs or microchannel plates exhibit limitations which are inherent to their actual material and technology. Yet the utmost spatial resolution, fast temporal cadence, sensitivity, and photometric accuracy will all be decisive for forthcoming solar space missions. The advent of imagers made of large wide-bandgap semiconductors would surmount many present weaknesses. This would open up new scientific prospects and, by simplifying their design, would even make the instruments cheaper. As for the Solar Orbiter, the aspiration for wide-bandgap semiconductor-based UV detectors is still more desirable because the spacecraft will approach the Sun where heat and radiation fluxes are high. We describe the motivations leading to such new developments, and present a programme to achieve revolutionary flight cameras within the Solar Orbiter schedule.