As the imaging devices increase in complexity so the development of electronic to interface those detectors due to their high level of flexibility and programmability. Referred to as Front End Electronics (FEE) it is often the bottleneck in new developments. It became clear that developing the FEE platform solution along aside the detector gave a critical advantage to the mission development time and therefore cost. Also providing a solution including FEE that can interface with the rest of the payload/instrument without further integration work reduces the integration time and cost. This is an area where Teledyne-e2v has worked and invested to develop an effective FEE platform solution for a range of imaging detectors from VUV to IR. In order to supply effective imaging solutions, it is clear it is critical to keep investing in developing state-of-the-art detectors but also to combine those detectors with FEE to interface those complex detectors and ease further their integration at instrument level. The presentation will cover innovations at Teledyne-e2v in both detector and FEE areas.
A Medium Wave Infrared (MWIR) image sensor developed by Teledyne e2v UK is studied for potential use in the International Mars Ice Mapper mission (I-MIM). Featuring a 640×512 array with a 15μm pixel pitch and a cutoff wavelength of 5μm, the sensor employs Ga-free InAsSb/InAs Type 2 Super Lattice (T2SL) and bariode (XBn) technologies. The study focuses on characterizing the sensor’s quantum efficiency (QE), dark current (DC), and radiation hardness under cryogenic conditions down to 130K. A system allowing in situ measurements pre- and post-irradiation was developed. The first QE measurements were conducted before and after irradiation with a 10MeV proton (p+) equivalent end-of-life fluence of 5×109 p+cm−2 and a double end-of-life fluence of 1×1010 p+cm−2 into the absorber layer, while the device was kept cryogenically cooled.
As space agencies consider the next generation of large space telescopes, it is becoming clear that high performance Ultraviolet (UV) imaging will be a key requirement. High-performing CMOS image sensors that are optimised for UV detection performance will therefore be essential for these missions to be able to fulfil their science requirements. The CASTOR mission, a 1m UV space telescope project, will be utilising the large format CIS303 and CIS120 detectors from Teledyne e2v for three large focal planes covering the UV , u ′ and g ′ bands, respectively. Typically, silicon sensors have a very low quantum efficiency (QE) in the UV band between 150- 300 nm, and the 2d-doping technology from NASA/JPL will therefore be utilised to improve the quantum efficiency. The Open University will perform electro-optical testing and space qualification of the CIS303 and CIS120 detectors, including a comparison of different UV coating and enhancement technologies. This paper covers the specification of radiation testing of the CIS303 and CIS120 detectors at the Open University, and characterisation of the QE-enhancing surface treatments.
CMOS image sensors traditionally have used a pinned photodiode with a transfer gate to achieve low dark signal and noise. One drawback of the pinned photodiode is the inability to achieve good Modulation Transfer Function (MTF) as the sensor thickness is increased beyond epitaxial thicknesses greater than 10μm as required for higher red response. This is due to the pinned photodiode providing only a very small voltage to deplete the silicon, which results in significant lateral charge diffusion and poor resolution. The limitation in device thickness means that the QE at longer wavelengths (>600nm) is limited for conventional CMOS pixel technologies. A way to increase the depletion depth is to apply a back bias from the rear of the device, however if one were to do this on standard CMOS image sensors then there would be significant leakage current between the back bias and components on the device causing it to not function. A new patented DDE (Deep Depletion Extension) implant helps diode depletion regions to merge laterally creating a “pinch-off” and prevent leakage from in-pixel transistors. This enables epitaxial thickness of up to 50μm to be fully depleted with negligible leakage. The CIS220 is a new ESA GSTP funded derivative of the CIS120 Capella Space Imager platform which incorporates this patented HiRho back bias structure allowing full depletion of the sensor thickness. This paper will present initial results from back-thinned CIS220 devices with 17μm and 33μm thicknesses and will explore the effect of the back bias on electro-optical test results.
Electron multiplying charge-coupled devices (EMCCDs) are a variant of standard CCD technology capable of single-optical photon counting at MHz pixel readout rates. For photon counting, thermal dark signal and clock-induced charge (CIC) are the dominant source of noise and must be minimized to reduce the likelihood of coincident events. Thermal dark signal is reduced to low levels through cooling or operation in inverted mode (pinning). However, mitigation of CIC requires precise tuning of both parallel and serial clock waveforms. Here, we present a detailed study of CIC within Teledyne-e2v EMCCDs with a goal of better understanding the physical mechanisms that dominate CIC production in both noninverted and inverted mode operations (IMO). Measurements are presented as a function of parallel and serial clock timings, clock amplitudes, and device temperature. The effects of radiation damage and annealing are also discussed. A widely accepted view is that CIC is signal generated through impact ionization of energetic holes as the clock phase is driven high. While this explanation holds for IMO, we propose that the majority of CIC generated in noninverted mode is in fact due to a secondary effect of light emission from hot carriers. The information from this study is then used to optimize CIC on Teledyne e2v CCD201s operating at 1-MHz pixel rate in NIMO. For the CCD201, we obtained total CIC levels as low as 6.9 × 10 − 4 e − / pix / frame with ≥90 % detective quantum efficiency. We conclude with proposals to further reduce CIC based upon modifications to clocking schemes and device architecture.
Opto-electronic devices destined for space must be suitably radiation-hard, meaning that they must be resilient to the effects of high energy radiation in space. For high performance IR (infrared) space-based applications, the current material of choice is MCT (Mercury Cadmium Telluride). MCT is difficult and therefore expensive to fabricate and the constituent materials are becoming increasingly restricted by regulation. The new generation of barrier diode detectors based on III-V materials offer a promising alternative to MCT, providing comparable performance whilst offering devices that are compatible with volume manufacturing processes. As part of a DASA Space-to-Innovate Phase 1 funded project we have developed a novel radiation hard unipolar barrierbased ABaT™ III-V MWIR diode detector. The detector is being subjected to gamma and proton radiation testing to demonstrate its suitability for space environments. To compare the radiation performance of this diode, a number of other typical III-V detector diode structures have been fabricated and tested. In this paper we present the results of the project so far and future plans to develop this into detector arrays.
KEYWORDS: Electron multiplying charge coupled devices, Radiation effects, Silicon, Charge-coupled devices, Astronomical telescopes, Synchrotrons, Life sciences, Space telescopes, Signal attenuation
Electron multiplying (EM) CCD technology has been successfully implemented for many ground-based applications (from astronomical telescopes to synchrotrons and life sciences), but has yet to be utilized within the space environment. The technology has the potential to offer superior photon-counting performance compared to competing technologies, however the effects of radiation damage must be understood and mitigated. The primary concern is damage from solar protons that manifests as signal trapping sites within the device. These traps can act to capture and defer signal charge to later pixels, degrading Charge Transfer Efficiency (CTE). With knowledge of the properties of the silicon defects responsible for charge loss, it is possible to optimize transfer performance through customized clocking and illumination patterns. Here, we present techniques to improve the charge transfer performance of irradiated Teledyne e2v CCD201 20 EMCCDs, including optimized clocking and illumination patterns based on the knowledge of silicon defects provided by the “trap pumping” technique following room temperature irradiation.
The Wide Field Infra-Red Survey Telescope (WFIRST) is a NASA observatory scheduled to launch in the next decade that will settle essential questions in exoplanet science. The Wide Field Instrument (WFI) offers Hubble quality imaging over a 0.28 square degree field of view and will gather NIR statistical data on exoplanets through gravitational microlensing. An on-board coronagraph will for the first time perform direct imaging and spectroscopic analysis of exoplanets with properties analogous to those within our own solar system, including cold Jupiters, mini Neptunes and potentially super Earths.
The Coronagraph Instrument (CGI) will be required to operate with low signal flux for long integration times, demanding all noise sources are kept to a minimum. The Electron Multiplication (EM)-CCD has been baselined for both the imaging and spectrograph cameras due its ability to operate with sub-electron effective read noise values with appropriate multiplication gain setting. The presence of other noise sources, however, such as thermal dark signal and Clock Induced Charge (CIC), need to be characterized and mitigated. In addition, operation within a space environment will subject the device to radiation damage that will degrade the Charge Transfer Effciency (CTE) of the device throughout the mission lifetime. Irradiation at the nominal instrument operating temperature has the potential to provide the best estimate of performance degradation that will be experienced in-flight, since the final population of silicon defects has been shown to be dependent upon the temperature at which the sensor is irradiated.
Here we present initial findings from pre- and post- cryogenic irradiation testing of the e2v CCD201-20 BI EMCCD sensor, baselined for the WFIRST coronagraph instrument. The motivation for irradiation at cryogenic temperatures is discussed with reference to previous investigations of a similar nature. The results are presented in context with those from a previous room temperature irradiation investigation that was performed on a CCD201-20 operated under the same conditions. A key conclusion is that the measured performance degradation for a given proton fluence is seen to measurably differ for the cryogenic case compared to the room temperature equivalent for the conditions of this study.
e2v continues to evolve its product range of sensors and systems, with CCD and CMOS sensors. We describe recent
developments of high performance image sensors and precision system components. Several low noise backthinned
CMOS sensors have been developed for scientific applications. CCDs have become larger whilst retaining very low
noise and high quantum efficiency. Examples of sensors and sub-systems are presented including the recently completed
1.2 GigaPixel J-PAS cryogenic camera.
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.
Dynamic charge collection effects in thick CCDs have received interest in recent years, due to the performance implications for both ground and space based precision optical astronomy. The phenomena manifest as the "brighter - fatter" effect in Point Spread Function (PSF) measurements, and nonlinearity and signal dependence in spatial autocorrelation and photon transfer measurements. In this paper we present validation results from simple, analytically based predictive models for this effect, using an e2v CCD250. The model is intended to provide estimations for predicting device performance based on design parameters.
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.
WFIRST-AFTA is a 2.4m class NASA observatory designed to address a wide range of science objectives using two complementary scientific payloads. The Wide Field Instrument (WFI) offers Hubble quality imaging over a 0.28 square degree field of view, and will gather NIR statistical data on exoplanets through gravitational microlensing. The second instrument is a high contrast coronagraph that will carry out the direct imaging and spectroscopic analysis of exoplanets, providing a means to probe the structure and composition of planetary systems. The coronagraph instrument is expected to operate in low photon flux for long integration times, meaning all noise sources must be kept to a minimum. In order to satisfy the low noise requirements, the Electron Multiplication (EM)-CCD has been baselined for both the imaging and spectrograph cameras. The EMCCD was selected in comparison with other candidates because of its low effective electronic read noise at sub-electron values with appropriate multiplication gain setting. The presence of other noise sources, however, such as thermal dark signal and Clock Induced Charge (CIC), need to be characterised and mitigated. In addition, operation within a space environment will subject the device to radiation damage that will degrade the Charge Transfer Efficiency (CTE) of the device throughout the mission lifetime. Here we present our latest results from pre- and post-irradiation testing of the e2v CCD201-20 BI EMCCD sensor, baselined for the WFIRST-AFTA coronagraph instrument. A description of the detector technology is presented, alongside considerations for operation within a space environment. The results from a room temperature irradiation are discussed in context with the nominal operating requirements of AFTA-C and future work which entails a cryogenic irradiation of the CCD201-20 is presented.
We present recent development in the technology of silicon sensors for astronomical applications. Novel CCD and CMOS sensors have been designed for low noise and high sensitivity astronomical use. High resistivity sensors allow thicker silicon for higher red sensitivity in several types of new CCD. The capability to manufacture large sets of CCDs to form large focal planes has allowed several very large mosaics to be built for astronomy with increasing formats on the ground and in space. In addition to supplying sensors we discuss increasing capacity and interest in the commercial supply of integrated “camera” systems.
The CCD282 is a large low-light level (L3 - Electron multiplying CCD) imaging sensor developed by e2v technologies for the University of Montreal. The intended use is for photon counting and very low light level imaging. The device will be used on the 3DNTT instrument which is a scanning Fabry-Perot interferometer. There is also the intention to place a device on a 10m class telescope for scanning Fabry-Perot application. This sensor is the largest electron multiplying CCD device produced to date with a 4k×4k backside illuminated frame transfer architecture. The sensor uses 8 parallel EM (Electron Multiplying) amplified outputs to maximize throughput. This paper present the first results and performance measurements of this device, and especially of the clock induced charge (CIC) which is one order of magnitude lower than previous devices thanks to a specific design optimized for photon counting operation.
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