[Previous] | [Session 72] | [Next]
M. E. Levi (LBNL), SNAP Collaboration
Based on a radiation tolerant, fully-depleted, high-resistivity CCD technology, a one billion pixel imager is envisioned for the Supernova Acceleration Probe (SNAP) satellite currently in early planning. The imager is comprised of over one hundred large format CCD's at the focal plane of an approximately 2-meter telescope. The diffraction-limited optics is achieved with a three-mirror anastigmat and provides a 1-square degree field of view. With a complementary small near-IR imager and visible and near-IR spectrographs, the SNAP mission can discover over 2000 Type Ia supernovae in a year at redshifts between z=0.1 and 1.7, and follow their evolution with high-signal-to-noise light-curves and spectra.
A key technological innovation in the SNAP instrumentation is a large one billion pixel camera, GigaCAM. In order to maximize the sensitivity of SNAP to discover high redshift supernova this camera requires excellent sensitivity in the I and Z optical bands. We have successfully developed a new type of large-format CCD on n-type high-resistivity silicon. The back-illuminated CCD's are fabricated on a 300 mm thick substrate and are fully depleted by the application of an independent voltage through an optically transparent backside contact. With back illumination, the QE at 900 nm is >90% (at T=150 K). Early measurements indicate that as expected this technology results in significantly improved radiation tolerance of the CCD. The CCD's are self-supporting since the devices do not need to be thinned. This allows for four-sided abutment, making these CCD's ideal for a wide-field mosaic array.
This technology development has been supported in part by DOE Office of Science High Energy Physics, NSF AST, and NASA Space Astrophysics Detectors.