The Second Generation of IR detectors for WFC3 Massimo Robberto European Space Agency and Space Telescope Science Institute

1. The Wide Field Camera 3 (WFC3) WFC3 is the last imager built for the Hubble Space Telescope (HST). It is intended to replace the WFPC2 camera. WFC3 provides diffraction limited imaging from the UV (2000 Å) to the near IR (1.7  m) using two different optical channels –UVIS: based on EEV CCD43 4k  2k –IR: based on RSC H1R 1k  1k WFC3 optics deliver –UVIS: 0.04"  0.04" pixel scale ~2.7'  2.7' field of view –IR: 0.135"  0.135" pixel scale ~ 2.3'  2.3' field of view Status of WFC3 WFC3 has successfully conducted thermal vacuum performance characterization test at the NASA Goddard Space Flight Center (GSFC) in September 2004.The instrument is currently at GSFC for partial de-integration and fix of residual liens. The installation on the HST is contingent upon authorization of shuttle-based servicing of HST after successful return-to-flight.

2.1 FPA64 is currently the flight-prime WFC3 IR detector FPA64 is HgCdTe with 1.72  m cutoff produced by Rockwell Scientific Company (RSC) Type: - MBE grown on CdZnTe substrate - Hawaii-1R MUX Operating T: 150K Pixel size: 18  m Format: 1024  1024 pixels  1014 active pixels - 5 outer row/columns with reference pixels

Quantum Efficiency (80% poeak at 1.6  m) Readout noise ~15e (16 read/ramp) 2.2 FPA64 Thermal Vacuum performance Dark current at 150K less than 0.2e/s/pix Linear scale Logarithmic scale

3. Radiation tests on FPA67 at UC Davies Detector radiated with ~900 hits/sec/cm -2 of 62 MeV protons The picture shows: Uniform distribution of proton hits Additional background “glow” The illumination pattern of the radiation-induced background is similar to the short wavelength QE response of the detector! See Poster of B. Hill for details

Adapted from The second generation of WFC3 detectors proton VIS photon IR photon proton First generation (FPA64) Second generation with substrate removed VIS photon IR photon Substrate removal is expected to: 1.Eliminate radiation induced glow 2.Increase the QE and shift the blue cutoff to shorter wavelengths

4.2 QE gain with substrate removed

5.3 Discovery efficiency: speed  field of view (arcmin 2 ) FPA 64 Baseline FPA 64 High CR glow (1e/s/pix) FPA 64 Low CR glow (0.25e/s/pix) New FPA Baseline New FPA High RON (40e DCS) New FPA Low RON (15e DCS) F110W F160W F126N Discovery efficiency Normalized to NIC3/ACS Absolute Discovery efficiency

5.4 Comparative HST discovery efficiency