High Quantum Efficiency Photon-Counting Imaging Detector Development for UV (50-320 nm) Astronomical Observations
Abstract
We are currently developing a high-quantum efficiency > 70% (peak), opaque photocathode-based, 2K x 2K pixel, zero-read-noise photon-counting detector system with the goal of enabling the highest possible sensitivity for space-based observations of ultra-faint astronomical targets in the UV.Current missions in the UV, eg HST (COS, STIS), GALEX etc although highly successful, exhibit relatively low quantum efficiency, < 40 % at Ly-a and < 10% in the NUV between 150 and 320 nm.Recent improvements in UV photocathodes using cesiated p-doped GaN, by GSFC and others have obtained QEs of up to 70% at 121 nm and 50% at 180 nm, (a factor 3 - 5 better than the traditional CsI and CsTe based systems) and so are the best hope for sensitivity improvements over most of the FUV and NUV spectral range for new medium and long term missions. However, these QEs are obtained on opaque planar and nanowire photocathodes, and have not been demonstrated in microchannel plate based detectors. The only known way to use these improved photocathodes while maintaining the high QE is to use them in electron-bombarded CCD or CMOS configurations.The detector concept under investigation is based on an opaque (GaN, KBr) photocathode, magnetically focused to a back-thinned CMOS readout stage.We are currently incorporating a QE optimized KBr photocathode deposited on a stainless steel substrate with an Intevac Inc, ISIE11 EBCMOS sensor into a demountable, magnetically focused detector system, designed and built at Rutgers University, NJ in order to demonstrate high quantum efficiency photon-counting imaging performance in the FUV region. We report here progress on integration and evaluate of the system for quantum efficiency, imaging performance, photo-electron counting efficiency and dark count.
- Publication:
-
American Astronomical Society Meeting Abstracts #217
- Pub Date:
- January 2011
- Bibcode:
- 2011AAS...21725419N