The next UV/O/IR flagship observatory mission recommended by the 2020 Decadal Survey on Astronomy and Astrophysics requires detector performance beyond what many devices deliver; i.e., lower dark current, lower read noise, higher QE, photon counting capability, etc. We evaluate how detector performance parameters affect the ability of an instrument to satisfy the science goals described in the LUVOIR concept study. We compare the requirements to performance in relevant metrics for current state-of-the-art devices. Current UV/O devices (specifically photon-counting CMOS ones) already perform at a level that meet most of the requirements of the upcoming flagship mission. We find that CMOS devices provide performance characteristics that exceed the requirements and exist in formats that demonstrate scalability beyond tens of mega-pixels. EMCCDs have demonstrated scalability to this size as well, though the excess noise factor introduced by the gain mechanism presents significant issues. MKIDs can resolve photon energy, but have yet to demonstrate scalability to mega-pixel formats. SNSPDs do not currently have readout architectures beyond the kilo-pixel level.
Single-photon sensing and photon-number resolving image sensors are key to enabling projects that are not possible today. We present detector characterization results for four single-photon sensing and photon-number resolving backside illuminated complementary metal-oxide semiconductor (CMOS) image sensors. Eric R. Fossum and his team at Dartmouth College led early detector development and continues through Gigajot Technology Inc. The CMOS image sensors have pixels (1.1 μm pitch) that use small-capacitance floating diffusions to achieve deep sub-electron read noise (<0.5 e− RMS). Characterization results include dark current, read noise, quantum efficiency, persistence, linearity, well depth. We also report on our ongoing work to use the image sensors for astronomical observations. We compare the performance of the four CMOS image sensors to that of state-of-the-art detectors, particularly with respect to the large UV/O/IR space telescope recommended by the 2020 Decadal Survey on Astronomy and Astrophysics.
We describe progress developing infrared detectors with HgCdTe grown on silicon substrates using Molecular Beam Epitaxial growth. The project is a collaboration between the RIT Center for Detectors and Raytheon Vision Systems (RVS). NASA and NSF jointly funded the program, known as SATIN (Short-wave infrared Advanced Technologies and Instrumentation program funded by NASA and NSF). We present detector characterization results for detectors made in the final lot of devices made by RVS. A full suite of characterization results, including for dark current, read noise, spectral response, persistence, linearity, full well, and crosstalk probability, are presented. The performance satisfies requirements for astronomy imaging applications. We plan to use the design to make HELLSTAR (HgCdTe Extremely Large Layout Sensor Technology for Astrophysics Research), a 4K×6K infrared detector with the highest number of pixels ever made for infrared astronomy.
The Water Recovery X-ray Rocket (WRXR) mission was a sounding rocket flight that targeted the northern part of the Vela supernova remnant with a camera designed to image the diffracted X-rays using a grating spectrometer optimized for OVII, OVIII, and CVI emissions. The readout camera for WRXR utilized a silicon hybrid CMOS detector (HCD) with an active area of 36.9 36.9 mm. A modified H2RG X-ray HCD, with 1024 1024 active silicon pixels bonded to the H2RG read-out integrated circuit, was selected for this mission based on its characteristics, technology maturation, and ease of implementation into the existing payload. This required a new camera package for the HCD to be designed, built, calibrated, and operated. This detector and camera system were successfully operated in-flight and its characteristics were demonstrated using the on-board calibration X-ray source. In this paper, a detailed description of this process, from design concept to flight performance, will be given. A full integrated instrument calibration will also be discussed, as well as the temperature dependency measurements of gain variation, read noise, and energy resolution for the HCD.
X-ray Hybrid CMOS Detectors (HCDs) have advantages over X-ray CCDs due to their higher readout rate abilities, flexible readout, inherent radiation hardness, and low power, which make them more suitable for the next generation large-area X-ray telescope missions. The Penn State high energy astronomy laboratory has been working on the development and characterization of HCDs in collaboration with Teledyne Imaging Sensors (TIS). A custom-made H2RG detector with 36 μm pixel pitch and 18 μm ROIC shows an improved performance over standard H1RG detectors, primarily due to a reduced level of inter-pixel capacitance crosstalk (IPC). However, the energy resolution and the noise of the detector and readout system are still limited when utilizing a SIDECAR at non-cryogenic temperatures. We characterized an H2RG detector with a Cryo-SIDECAR readout and controller, and we find an improved energy resolution of ∼2.7 % at 5.9 keV and read noise of ∼6.5 e- . Detections of the ∼0.525 keV Oxygen Kα and ∼0.277 keV Carbon Kα lines with this detector display an improved sensitivity level at lower energies. This detector was successfully flown on NASA’s first water recovery sounding rocket flight on April 4th, 2018. We have also been developing several new HCDs with potential applications for future X-ray astronomy missions. We are characterizing the performance of small-pixel HCDs (12.5 μm pitch), which are important for the development of a next-generation high-resolution imager with HCDs. The latest results on these small pixel detectors has shown them to have the best read noise and energy resolution to-date for any X-ray HCD, with a measured 5.5 e- read noise for a detector with in-pixel correlated double sampling. Event recognition in HCDs is another exciting prospect. We characterized a 64 × 64 pixel prototype Speedster-EXD detector that uses comparators in each pixel to read out only those pixels having detectable signal, thereby providing an order of magnitude improvement in the effective readout rate. Currently, we are working on the development of a large area Speedster-EXD with a 550 × 550 pixel array. HCDs can also be utilized as a large FOV instrument to study the prompt and afterglow emissions of GRBs and detect black hole transients. In this context, we are characterizing a Lobster-HCD system for future CubeSat experiments. This paper briefly presents these new developments and experimental results.
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