Electron multiplication CCD detector technology advancement for the WFIRST-AFTA coronagraph

The WFIRST-AFTA (Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset) is a NASA space observatory. It will host two major astronomical instruments: a wide-field imager (WFI) to search for dark energy and carry out wide field near infrared (NIR) surveys, and a coronagraph instrument (CGI) to image and spectrally characterize extrasolar planets. In this paper, we discuss the work that has been carried out at JPL in advancing Electron Multiplying CCD (EMCCD) technology to higher flight maturity, with the goal of reaching a NASA technology readiness level of 6 (TRL-6) by early-to-mid 2016. The EMCCD has been baselined for both the coronagraph's imager and integral field spectrograph (IFS) based on its sub-electron noise performance at extremely low flux levels - the regime where the AFTA CGI will operate. We present results from a study that fully characterizes the beginning of life performance of the EMCCD. We also discuss, and present initial results from, a recent radiation test campaign that was designed and carried out to mimic the conditions of the WFIRST-AFTA space environment in an L2 orbit, where we sought to assess the sensor's end of life performance, particularly degradation of its charge transfer efficiency, in addition to other parameters such as dark current, electron multiplication gain, clock induced charge and read noise

Technology advancement of the CCD201-20 EMCCD for the WFIRST coronagraph instrument: sensor characterization and radiation damage

The Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset (WFIRST-AFTA) mission is a 2.4-m class space telescope that will be used across a swath of astrophysical research domains. JPL will provide a high-contrast imaging coronagraph instrument—one of two major astronomical instruments. In order to achieve the low noise performance required to detect planets under extremely low flux conditions, the electron multiplying charge-coupled device (EMCCD) has been baselined for both of the coronagraph’s sensors—the imaging camera and integral field spectrograph. JPL has established an EMCCD test laboratory in order to advance EMCCD maturity to technology readiness level-6. This plan incorporates full sensor characterization, including read noise, dark current, and clock-induced charge. In addition, by considering the unique challenges of the WFIRST space environment, degradation to the sensor’s charge transfer efficiency will be assessed, as a result of damage from high-energy particles such as protons, electrons, and cosmic rays. Science-grade CCD201-20 EMCCDs have been irradiated to a proton fluence that reflects the projected WFIRST orbit. Performance degradation due to radiation displacement damage is reported, which is the first such study for a CCD201-20 that replicates the WFIRST conditions. In addition, techniques intended to identify and mitigate radiation-induced electron trapping, such as trap pumping, custom clocking, and thermal cycling, are discussed

Rapid casting of patterned vascular networks for perfusable engineered three-dimensional tissues

In the absence of perfusable vascular networks, three-dimensional (3D) engineered tissues densely populated with cells quickly develop a necrotic core. Yet the lack of a general approach to rapidly construct such networks remains a major challenge for 3D tissue culture. Here, we printed rigid 3D filament networks of carbohydrate glass, and used them as a cytocompatible sacrificial template in engineered tissues containing living cells to generate cylindrical networks that could be lined with endothelial cells and perfused with blood under high-pressure pulsatile flow. Because this simple vascular casting approach allows independent control of network geometry, endothelialization and extravascular tissue, it is compatible with a wide variety of cell types, synthetic and natural extracellular matrices, and crosslinking strategies. We also demonstrated that the perfused vascular channels sustained the metabolic function of primary rat hepatocytes in engineered tissue constructs that otherwise exhibited suppressed function in their core.National Institutes of Health (U.S.) (Grant EB00262)National Institutes of Health (U.S.) (Grant EB08396)National Institutes of Health (U.S.) (Grant GM74048)University of Pennsylvania (Center for Engineering Cells and Regeneration)American Heart Association (Jon Holden DeHaan Foundation)National Institutes of Health (U.S.). Ruth L. Kirschstein National Research Service Award (DK091007