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- Front Matter: Volume 7742
- EM CCDs
- CCDs I
- CCDs II
- CMOS
- CCDs III
- Cryogenic Detectors
- X-Ray Detectors I
- X-Ray Detectors II
- Radiation Damage
- Electronics for Imagers
- Visible Imagers
- X-Ray Detectors III
- IR Detectors I
- IR Detectors II
- Poster Session
Front Matter: Volume 7742
Front Matter: Volume 7742
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 7742, including the Title Page, Copyright information, Table of Contents, introduction (if any), and the Conference Committee listing.
EM CCDs
High-speed, photon-counting CCD cameras for astronomy
Show abstract
The design of electron multiplying CCD cameras require a very different approach from that appropriate for slow scan
CCD operation. This paper describes the main problems in using electron multiplying CCDs for high-speed, photon
counting applications in astronomy and how these may be substantially overcome. With careful design it is possible to
operate the E2V Technologies L3CCDs at rates well in excess of that claimed by the manufacturer, and that levels of
clock induced charge dramatically lower than those experienced with commercial cameras that need to operate at unity
gain. Measurements of the performance of the E2V Technologies CCD201 operating at 26 MHz will be presented
together with a guide to the effective reduction of clock induced charge levels. Examples of astronomical results
obtained with our cameras are presented.
The darkest EMCCD ever
Show abstract
EMCCDs are devices capable of sub-electron read-out noise at high pixel rate, together with a high quantum efficiency
(QE). However, they are plagued by an excess noise factor (ENF) which has the same effect on photometric measurement
as if the QE would be halved. In order to get rid of the ENF, the photon counting (PC) operation is mandatory, with the
drawback of counting only one photon per pixel per frame. The high frame rate capability of the EMCCDs comes to the
rescue, at the price of increased clock induced charges (CIC), which dominates the noise budget of the EMCCD. The CIC
can be greatly reduced with an appropriate clocking, which renders the PC operation of the EMCCD very efficient for faint
flux photometry or spectroscopy, adaptive optics, ultrafast imaging and Lucky Imaging. This clocking is achievable with
a new EMCCD controller: CCCP, the CCD Controller for Counting Photons. This new controller, which is now commercialized
by Nüvü cameras inc., was integrated into an EMCCD camera and tested at the observatoire du mont-M'egantic.
The results are presented in this paper.
AO wavefront sensing detector developments at ESO
Show abstract
The detector is a critical component of any Adaptive Optics WaveFront Sensing (AO WFS) system. The required
combination of fast frame rate, high quantum efficiency, low noise, large number and size of pixels, and low image lag
can often only be met by specialized custom developments.
ESO's very active WFS detector development program is described.
Key test results are presented for newly developed detectors: a) the e2v L3Vision CCD220 (the fastest/lowest noise AO
detector to date) to be deployed soon on 2nd Generation VLT instruments, and b) the MPI-HLL pnCCD with its superb
high "red" response.
The development of still more advanced laser/natural guide-star WFS detectors is critical for the feasibility of ESO's EELT.
The paper outlines: a) the multi-phased development plan that will ensure detectors are available on-time for EELT
first-light AO systems, b) results of design studies performed by industry during 2007 including a comparison of
the most promising technologies, c) results from CMOS technology demonstrators that were built and tested over the
past two years to assess and validate various technologies at the pixel level, their fulfillment of critical requirements
(especially read noise and speed), and scalability to full-size. The next step will be towards Scaled-Down Demonstrators
(SDD) to retire architecture and process risks. The SDD will be large enough to be used for E-ELT first-light AO WFS
systems. For full operability, 30-50 full-scale devices will be needed.
CCDs I
A study of electron-multiplying CCDs for use on the International X-ray Observatory off-plane x-ray grating spectrometer
Show abstract
CCDs are regularly used as imaging and spectroscopic devices on space telescopes at X-ray energies due to their
high quantum efficiency and linearity across the energy range. The International X-ray Observatory's X-ray
Grating Spectrometer will also look to make use of these devices across the energy band of 0.3 keV to 1 keV.
At these energies, when photon counting, the charge generated in the silicon is close to the noise of the system.
In order to be able to detect these low energy X-ray events, the system noise of the detector has to be minimised
to have a sufficient signal-to-noise-ratio. By using an EM-CCD instead of a conventional CCD, any charge that
is collected in the device can be multiplied before it is read out and as long as the EM-CCD is cool enough to
adequately suppress the dark current, the signal-to-noise ratio of the device can be significantly increased,
allowing soft X-ray events to be more easily detected.
This paper will look into the use of EM-CCDs for the detection of low energy X-rays, in particular the effect
that using these devices will have on the signal to noise ratio as well as any degradation in resolution and
FWHM that may occur due to the additional shot noise on the signal caused by the charge packet amplification
process.
Study of pixel area variations in fully depleted thick CCD
Show abstract
Future wide field astronomical surveys, like Large Synoptic Survey Telescope (LSST), require photometric precision
on the percent level. The accuracy of sensor calibration procedures should match these requirements. Pixel
size variations found in CCDs from different manufacturers are the source of systematic errors in the flat field
calibration procedure. To achieve the calibration accuracy required to meet the most demanding science goals
this effect should be taken into account.
The study of pixel area variations was performed for fully depleted, thick CCDs produced in a technology
study for LSST. These are n-channel, 100μm thick devices.
We find pixel size variations in both row and column directions. The size variation magnitude is smaller in
the row direction. In addition, diffusion is found to smooth out electron density variations. It is shown that the
characteristic diffusion width can be extracted from the flat field data.
Results on pixel area variations and diffusion, data features, analysis technique and modeling technique are
presented and discussed.
PSF and MTF measurement methods for thick CCD sensor characterization
Show abstract
Knowledge of the point spread function (PSF) of the sensors to be used in the Large Synoptic Survey Telescope (LSST)
camera is essential for optimal extraction of subtle galaxy shape distortions caused by gravitational weak lensing. We
have developed a number of techniques for measuring the PSF of candidate CCD sensors to be used in the LSST camera,
each with its own strengths and weaknesses. The two main optical PSF measurement techniques that we use are the
direct Virtual Knife Edge (VKE) scan as developed by Karcher, et al.1 and the indirect interference fringe method after
Andersen and Sorensen2 that measures the modulation transfer function (MTF) directly. The PSF is derived from the
MTF by Fourier transform. Other non-optical PSF measurement techniques that we employ include 55Fe x-ray cluster
image size measurements and statistical distribution analysis, and cosmic ray muon track size measurements, but are not
addressed here.
The VKE technique utilizes a diffraction-limited spot produced by a Point-Projection Microscope (PPM) that is scanned
across the sensor with sub-pixel resolution. This technique closely simulates the actual operating condition of the sensor
in the telescope with the source spot size having an f/# close to the actual telescope design value. The interference fringe
method uses a simple equal-optical-path Michelson-type interferometer with a single-mode fiber source that produces
interference fringes with 100% contrast over a wide spatial frequency range sufficient to measure the MTF of the sensor
directly. The merits of each measurement technique and results from the various measurement techniques on prototype
LSST sensors are presented and compared.
CCDs II
Commissioning of the CCD231 4Kx4K detector for PMAS
Show abstract
The PMAS integral field spectrophotometer, operated at the Calar Alto Observatory 3.5m Telescope, is one of the most
demanded instruments of its kind. The optical system was designed for a camera field of view to accommodate a 4K×4K
detector with 15μm pixels. However, due to a failure of one of the initially foreseen 2K×4K CCDs in a mosaic
configuration, only half of the available field of view could be covered to date. Owing to the high demand from the user
community, an upgrade to the full complement of 4K×4K pixels was envisaged, based on the availability of the new e2v
CCD231 device. We describe the specification, implementation, test, and commissioning of this new detector for PMAS.
Characterization of a Σ∆-based CMOS monolithic detector
Show abstract
This paper is a progress report of the design and characterization of a monolithic CMOS detector with an on-chip ΣΔ
ADC. A brief description of the design and operation is given. Backside processing steps to allow for backside
illumination are summarized. Current characterization results are given for pre- and post-thinned detectors.
Characterization results include measurements of: gain photodiode capacitance, dark current, linearity, well depth,
relative quantum efficiency, and read noise. Lastly, a detector re-design is described; and initial measurements of its
photodiode capacitance and read noise are presented.
CMOS
Fundamental performance differences between CMOS and CCD imagers, part IV
Show abstract
This paper is a continuation of past papers written on fundamental performance differences of scientific CMOS and
CCD imagers. New characterization results presented below include: 1). a new 1536 × 1536 × 8μm 5TPPD pixel CMOS
imager, 2). buried channel MOSFETs for random telegraph noise (RTN) and threshold reduction, 3) sub-electron noise
pixels, 4) 'MIM pixel' for pixel sensitivity (V/e-) control, 5) '5TPPD RING pixel' for large pixel, high-speed charge
transfer applications, 6) pixel-to-pixel blooming control, 7) buried channel photo gate pixels and CMOSCCDs, 8)
substrate bias for deep depletion CMOS imagers, 9) CMOS dark spikes and dark current issues and 10) high energy
radiation damage test data. Discussions are also given to a 1024 × 1024 × 16 um 5TPPD pixel imager currently in
fabrication and new stitched CMOS imagers that are in the design phase including 4k × 4k × 10 μm and 10k × 10k × 10
um imager formats.
Hybridization of a sigma-delta-based CMOS hybrid detector
Show abstract
The Rochester Imaging Detector Laboratory, University of Rochester, Infotonics Technology Center, and Jet Process
Corporation developed a hybrid silicon detector with an on-chip sigma-delta (ΣΔ) ADC. This paper describes the process
and reports the results of developing a fabrication process to robustly produce high-quality bump bonds to hybridize a
back-illuminated detector with its ΣΔ ADC. The design utilizes aluminum pads on both the readout circuit and the
photodiode array with interconnecting indium bumps between them. The development of the bump bonding process is
discussed, including specific material choices, interim process structures, and final functionality. Results include
measurements of bond integrity, cross-wafer uniformity of indium bumps, and effects of process parameters on the final
product. Future plans for improving the bump bonding process are summarized.
Gamma radiation damage study of 0.18 µm process CMOS image sensors
Show abstract
A 0.18 μm process CMOS image sensor has recently been developed by e2v technologies plc. with a 0.5
megapixel imaging area consisting of 6 × 6 μm 5T pixels. The sensor is able to provide high performance in a
diverse range of applications including machine vision and medical imaging, offering good low-light
performance at a video rate of up to 60 fps. The CMOS sensor has desirable characteristics which make it
appealing for a number of space applications. Following on from previous tests of the radiation hardness of the
image sensors to proton radiation, in which the increase in dark-current and appearance of bright and RTS pixels
was quantified, the sensors have now been subjected to a dose of gamma radiation. Knowledge of the
performance after irradiation is important to judge suitability for space applications and radiation sensitive
medical imaging applications. This knowledge will also enable image correction to mitigate the effects and
allow for future CMOS devices to be designed to improve upon the findings in this paper. One device was
irradiated to destruction after 120 krad(Si) while biased, and four other devices were irradiated between 5 and
20 krad(Si) while biased. This paper explores the resulting radiation damage effects on the CMOS image sensor
such as increased dark current, and a central brightening effect, and discusses the implications for use of the
sensor in space applications.
CCDs III
Space-qualified, abuttable packaging for LBNL p-channel CCDs, part II
Show abstract
Fully depleted, back-illuminated, p-channel CCDs developed at Lawrence Berkeley National Laboratory exhibit high
quantum efficiency in the near-infrared (700-1050nm), low fringing effects, low lateral charge diffusion (and hence
small, well-controlled point spread function), and high radiation tolerance. Building on previous efforts, we have
developed techniques and hardware that have produced space-qualified 4-side abuttable, high-precision detector
packages for 10.5μm pixel, 3.5k x 3.5k p-channel LBNL CCDs. These packages are built around a silicon carbide
mounting pedestal, providing excellent rigidity, thermal stability, and heat transfer. Precision fixturing produces
packages with detector surface flatness better than 10μm P-V. These packages with active areas of 36.8mm square may
be packed on a detector pitch as small as 44mm. LBNL-developed Front End Electronics (FEE) packages can mount
directly to the detector packages within the same footprint and detector pitch. This combination, along with identically
interfaced NIR detector/FEE packages offers excellent opportunities for high density, high pixel count focal planes for
space-based, ground-based, and airborne astronomy.
Characterization and absolute QE measurements of delta-doped N-channel and P-channel CCDs
Show abstract
In this paper we present the methodology for making absolute quantum efficiency (QE) measurements from the vacuum
ultraviolet (VUV) through the near infrared (NIR) on delta-doped silicon CCDs. Delta-doped detectors provide an
excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for
measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other
things, the use of a vacuum monochromator, and good camera vacuum to prevent chip condensation, and more stringent
handling requirements. The system used for these measurements was originally designed for deep UV characterization
of CCDs for the WF/PC instrument on Hubble and later for Cassini CCDs.
Improving the red wavelength sensitivity of CCDs
Show abstract
The demand for higher red wavelength sensitivity is being met by various technological developments of modern CCDs.
We discuss techniques for achieving higher red wavelength sensitivity by using thicker silicon to make backthinned
CCDs, which combines with very low read noise for enhanced sensitivity. Thicker devices requires higher resistivity
material including bulk (non epitaxial) silicon. An extended wavelength range also places more demand on the antireflection
coatings which benefit from corresponding optimisation.
Characterization of deep-depletion Hamamatsu CCDs for the Gemini multi-object spectrograph
Show abstract
We have performed some initial characterization of back-illuminated deep-depletion CCDs from Hamamatsu Photonics.
Three of these 2048×4096, three-side buttable devices will replace the current CCDs in the Gemini Multi-Object
Spectrograph to improve the performance of the instrument in the red and near-infrared wavelengths. We describe our
testing campaign and report on the results.
Cryogenic Detectors
Imaging soft x-ray spectrometers based on superconducting tunnel junctions
Show abstract
X-ray detectors based on superconducting tunnel junctions (STJs) have demonstrated good energy resolution in the soft
X-ray energy range 0.1-6 keV. In particular DROIDS (Distributed Read Out Imaging Devices), consisting of a
superconducting absorber strip with superconducting tunnel junctions as read-out devices on either end, could combine
this high resolving power with a large sensitive area and good soft X-ray detection efficiency.
In this paper we present results on the spectroscopic performance of Al and Ta/Al DROIDs with different
absorber materials (Ta, Re) and with variations in absorber configurations: our standard absorber integrated with the
read-out structure is compared with absorbers deposited after definition of the read-out structure. The latter allows
maximising the detection efficiency through thicker layers and different absorber materials. Also, absorbers which are
electrically coupled to the readout structure are compared to insulated absorbers which couple to the readout structure by
phonon exchange across a thin dielectric layer. New process routes have been designed for all new configurations.
Whilst not all these structures have been fabricated successfully yet, our integrated absorber sofar exhibits the best
performance, with 2.45 eV FWHM at 400 eV and 16.6 eV FWHM at 5.9 keV.
X-Ray Detectors I
In-orbit performance of avalanche photodiode as radiation detector onboard a pico-satellite Cute-1.7+APD II
Show abstract
Cute-1.7+APD II is the third pico-satellite developed by students at the Tokyo Institute of Technology. One of
the primary goals of the mission is to validate the use of avalanche photodiodes (APDs) as a radiation detector
for the first time in a space experiment. The satellite was successfully launched by an ISRO PSLV-C9 rocket
in Apr 2008 and has since been in operation for more than 20 months. Cute-1.7+APD II carries two reversetype
APDs to monitor the distribution of low energy particles down to 9.2 keV trapped in a Low Earth Orbit
(LEO), including South Atlantic Anomaly (SAA) as well as aurora bands. We present the design parameters
and various preflight tests of the APDs prior to launch, particularly, the high counting response and active
gain control system for the Cute-1.7+APD II mission. Examples of electron/proton distribution, obtained in
continuous 12-hour observations, will be presented to demonstrate the initial flight performance of the APDs in
orbit.
Measurements of Si hybrid CMOS x-ray detector characteristics
Show abstract
The recent development of active pixel sensors as X-Ray focal plane arrays will place them in contention with
CCDs on future satellite missions. Penn State University (PSU) is working with Teledyne Imaging Sensors
(TIS) to develop X-Ray Hybrid CMOS devices (HCDs), a type of active pixel sensor with fast frame rates,
adaptable readout timing and geometry, low power consumption, and inherent radiation hardness. CCDs have
been used with great success on the current generation of X-Ray telescopes (e.g. Chandra, XMM, Suzaku, and
Swift). However, their bucket-brigade readout architecture, which transfers charge across the chip with discrete
component readout electronics, results in clockrate limited readout speeds that cause pileup (saturation) of bright
sources and an inherent susceptibility to radiation induced displacement damage that limits mission lifetime. In
contrast, HCDs read pixels through the detector substrate with low power, on-chip readout integrated circuits.
Faster frame rates, achieved with adaptable readout timing and geometry, will allow the next generation's larger
effective area telescopes to observe brighter sources free of pileup. In HCDs, radiation damaged lattice sites
affect a single pixel instead of an entire row. The PSU X-ray group is currently testing 4 Teledyne HCDs,
with low cross-talk CTIA devices in development. We will report laboratory measurements of HCD readnoise,
interpixel-capacitance and its impact on event selection, linearity, and energy resolution as a function of energy.
X-Ray Detectors II
The DEPFET-based focal plane detectors for MIXS on BepiColombo
Show abstract
X-ray detectors based on arrays of DEPFET macropixels, which consist of a silicon drift detector combined with
a detector/amplifier structure DEPFET as readout node, provide a convenient and flexible way to adapt the pixel
size of a focal plane detector to the resolving power of any given X-ray optical system. Macropixels combine the
traditional benefits of an SDD, like scalability, arbitrary geometry and excellent QE even in the low energy range,
with the advantages of DEPFET structures: Charge storage capability, near Fano-limited energy resolution, low
power consumption and high speed readout. Being part of the scientific payload of ESA's BepiColombo mission,
the MIXS instrument will be the first instrument to make use of DEPFET macropixel based FPA detectors in
space. MIXS will perform a complete planetary X-ray fluorescence analysis of Mercury's crust with high spectral
and spatial resolution. MIXS will contain two focal plane detectors consisting of a 64 × 64 macropixel matrix
with 300 × 300 μm2 pixel size. The main challenges for the instrument are the difficult radiation and thermal
environment around Mercury, requiring high speed readout and sophisticated thermal management to reduce
the impact of thermally generated leakage current within an irradiated detector. Dedicated VLSI integrated
readout electronics has been developed for MIXS: a fast, radiation hard, low power, high voltage switch circuit
to control the device, and a low noise, high speed amplifier/shaper IC. Detector assemblies have been built,
electrical screening tests for the flight models and spectroscopical qualification tests are in progress.
The IXO wide-field imager
Show abstract
The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a
large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of
10 × 10 cm² with a format of 1024 × 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of
100 × 100 μm² corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The
WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited
energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier
ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative
prototypes with a format of 256 × 256 pixels are presented.
Quantum efficiency measurements of eROSITA pnCCDs
Show abstract
For the eROSITA X-ray telescope, which is planned to be launched in 2012, detectors were developed and
fabricated at the MPI Semiconductor Laboratory. The fully depleted, back-illuminated pnCCDs have an ultrathin
pn-junction to improve the low-energy X-ray response function and quantum efficiency. The device thickness of
450 μm is fully sensitive to X-ray photons yielding high quantum efficiency of more than 90% at photon energies of
10 keV. An on-chip filter is deposited on top of the entrance window to suppress visible and UV light which would
interfere with the X-ray observations. The pnCCD type developed for the eROSITA telescope was characterized
in terms of quantum efficiency and spectral response function. The described measurements were performed in
2009 at the synchrotron radiation sources BESSY II and MLS as cooperation between the MPI Semiconductor
Laboratory and the Physikalisch-Technische Bundesanstalt (PTB). Quantum efficiency measurements over a
wide range of photon energies from 3 eV to 11 keV as well as spectral response measurements are presented. For
X-ray energies from 3 keV to 10 keV the quantum efficiency of the CCD including on-chip filter is shown to be
above 90% with an attenuation of visible light of more than five orders of magnitude. A detector response model
is described and compared to the measurements.
Development of a 3D CZT detector prototype for Laue Lens telescope
Show abstract
We report on the development of a 3D position sensitive prototype suitable as focal plane detector for Laue lens
telescope. The basic sensitive unit is a drift strip detector based on a CZT crystal, (~19×8 mm2 area, 2.4 mm thick),
irradiated transversally to the electric field direction. The anode side is segmented in 64 strips, that divide the crystal in 8
independent sensor (pixel), each composed by one collecting strip and 7 (one in common) adjacent drift strips. The drift
strips are biased by a voltage divider, whereas the anode strips are held at ground. Furthermore, the cathode is divided in
4 horizontal strips for the reconstruction of the third interaction position coordinate. The 3D prototype will be made by
packing 8 linear modules, each composed by one basic sensitive unit, bonded on a ceramic layer. The linear modules
readout is provided by a custom front end electronics implementing a set of three RENA-3 for a total of 128 channels.
The front-end electronics and the operating logics (in particular coincidence logics for polarisation measurements) are
handled by a versatile and modular multi-parametric back end electronics developed using FPGA technology.
The silicon drift detector for the IXO high-time resolution spectrometer
Show abstract
The High Time Resolution Spectrometer (HTRS) is one of six scientific payload instruments of the International X-ray
Observatory (IXO). HTRS is dedicated to the physics of matter at extreme density and gravity and will observe the
X-rays generated in the inner accretion flows around the most compact massive objects, i.e. black holes and neutron
stars. The study of their timing signature and in addition the simultaneous spectroscopy of the gravitationally shifted and
broadened iron line allows for probing general relativity in the strong field regime and understanding the inner structure
of neutron stars. As the sources to be observed by HTRS are the brightest in the X-ray sky and the studies require good
photon statistics the instrument design is driven by the capability to operate at extremely high count rates.
The HTRS instrument is based on a monolithic array of Silicon Drift Detectors (SDDs) with 31 cells in a circular
envelope and a sensitive volume of 4.5 cm2 × 450 μm. The SDD principle uses fast signal charge collection on an
integrated amplifier by a focusing internal electrical field. It combines a large sensitive area and a small capacitance, thus
facilitating good energy resolution and high count rate capability. The HTRS is specified to provide energy spectra with
a resolution of 150 eV (FWHM at 6 keV) at high time resolution of 10 μsec and with high count rate capability up to a
goal of 2·106 counts per second, corresponding to a 12 Crab equivalent source. As the HTRS is a non-imaging instrument
and will target only point sources it is placed on axis but out of focus so that the spot is spread over the array of 31 SDD
cells. The SDD array is logically organized in four independent 'quadrants', a dedicated 8-channel quadrant readout chip
is in development.
Off-plane x-ray grating spectrometer camera for IXO
Show abstract
The International X-ray Observatory (IXO) is a merger of the former ESA XEUS and NASA Constellation-X missions,
with additional collaboration from JAXA, proposed for launch ~2020. IXO will address the leading astrophysical
questions in the 'hot universe' through its breakthrough capabilities in X-ray spectroscopy. The mission covers the 0.1
to 40 keV energy range, complementing the capabilities of the next generation observatories, such as ALMA, LSST,
JWST and 30 meter ground-based telescopes. An X-ray Grating Spectrometer is baselined to provide science in the
energy range 0.3-1.0 keV at a spectral resolution of E/ΔE > 3,000 with an effective area greater than 1,000 cm2. This
will require an array of soft X-ray enhanced CCDs operating at a modest frame rate to measure the diffracted light in
both position and energy. Here we describe the baseline camera for the Off-plane XGS instrument using mature CCD
technology.
Geant4 simulation studies of the eROSITA detector background
Show abstract
We report on simulation results for the eROSITA instrument background obtained with Monte-Carlo simulations
using the Geant4 toolkit. Besides a brief introduction to the simulation environment created at our institute,
the input particle spectrum and flux as well as the post-simulation event treatment and analysis are explained.
Latest results for the background level and spectral shape induced by interactions of cosmic-ray protons with
the camera housing are given. In addition, we show results from different studies concerning variation of the
background level as a function of the CCD thickness and the composition of the graded shield.
Development of the Simbol-X science verification model and its contribution for the IXO Mission
Daniel Maier,
Florian Aschauer,
Jürgen Dick,
et al.
Show abstract
Like the International X-ray Observatory (IXO) mission, the Simbol-X mission is a projected X-ray space telescope
with spectral and imaging capabilities covering the energy range from 500 eV up to 80 keV. To detect photons
within this wide range of energies, a silicon based "Depleted P-channel Field Effect Transistor" (DePFET)-
matrix is used as the Low Energy Detector (LED) on top of an array of CdTe-Caliste modules, which act as the
High Energy Detector (HED).
A Science Verification Model (SVM) consisting of one LED quadrant in front of one Caliste module will be set
up at our institute (IAAT) and operated under laboratory conditions that approximate the expected environment
in space. As a first step we use the SVM to test and optimize the performance of the LED operation and data
acquisition chain, consisting of an ADC, an event-preprocessor, a sequencer, and an interface controller. All
these components have been developed at our institute with the objective to handle the high readout rate of
approximately 8000 frames per second. The second step is to study the behaviour and the interactions of LED
and HED operating as a combined detector system.
We report on the development status of the SVM and its associated electronics and present first results of
the currently achieved spectral performance.
Electronic test system for the eROSITA x-ray PNCCDs
Show abstract
The new X-ray telescope eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the main
instrument on the Russian new Spectrum-RG satellite, scheduled for launch in 2012. The primary scientific goal
of eROSITA is the detection of about 100,000 clusters of galaxies in an all sky survey. This allows a systematic
study on the large scale structures in the universe and will give new information about the nature of dark energy.
The focal plane detector is a 5 cm × 3 cm framestore PNCCD, an advanced successor of the XMM-Newton
PNCCD, designed and fabricated at the MPI Halbleiterlabor. It has 384 × 384 pixels of 75 μm × 75 μm in the
image area and will provide high position, time and spectral resolution as well as a high quantum efficiency for
X-ray photons in the energy range from 0.2 keV up to 10 keV. The first flight-like CCDs have been finished in
2008. In order to extensively test these new PNCCDs we developed an electronic test-setup. It is very versatile,
allowing us to test the CCDs under many different conditions and is appropriate to show at the same time
excellent performance of the detector. In this contribution we present in detail the electronic test-setup, some
test results and the conclusions which can be drawn for the eROSITA flight modules.
Radiation Damage
A fast model of radiation-induced electron trapping in CCDs for implementation in the Gaia data processing
Show abstract
The European Space Agency's Gaia mission1 is scheduled for launch in 2012. It will operate at L2 for 5 years,
rotating slowly so that its two optical telescopes will repeatedly observe more than one billion stars. The resulting
data set will be iteratively reduced to solve for the relative position, parallax-distance and proper motion of every
observed star, yielding a three dimensional dynamical model of our galaxy. The focal plane contains 106 large
area silicon CCDs continuously operating in TDI mode at a line rate synchronised with the satellite rotation.2
One of the greatest challenges facing the mission is radiation damage in the CCDs which will cause charge
loss and image distortion. This is particularly severe because the large focal plane is difficult to shield and
because the launch will coincide with solar maximum. Despite steps taken to minimize the effects of radiation
(e.g. regular use of charge injection), the residual distortion will need to be calibrated during the pipeline data
processing. Due to the volume of data involved, this requires a trapping model which is physically realistic, yet
fast enough and simple enough to implement in the pipeline. The current prototype Charge Distortion Model
will be presented. This model was developed specifically for Gaia in TDI mode. However, an imaging mode
version has already been applied to other missions, for example, to indicate the potential impact of radiation
damage on the proposed Euclid mission.
Comparison of a fast analytical model of radiation damage effects in CCDs with experimental tests
Show abstract
ESA's Gaia mission aims to create a complete and highly accurate stereoscopic map of the Milky Way. The
stellar parallaxes will be determined at the micro-arcsecond level, as a consequence the measurement of the
stellar image location on the CCD must be highly accurate. The solar wind protons will create charge traps in
the CCDs of Gaia, which will induce large charge loss and distort the stellar images causing a degradation of
the location measurement accuracy. Accurate modelling of the stellar image distortion induced by radiation is
required to mitigate these effects. We assess the capability of a fast physical analytical model of radiation damage
effects called the charge distortion model (CDM) to reproduce experimental data. To realize this assessment
we developed a rigorous procedure that compares at the sub-pixel level the model outcomes to damaged images
extracted from the experimental tests. We show that CDM can reproduce accurately up to a certain level the test
data acquired on a highly irradiated device operated in time delay integration mode for different signal levels and
different illumination histories. We discuss the potential internal and external factors that contributed to limit
the agreement between the data and the charge distortion model. To investigate these limiting factors further,
we plan to apply our comparison procedure on a synthetic dataset generated through detailed Monte-Carlo
simulations at the CCD electrode level.
Silvaco ATLAS model of ESA's Gaia satellite e2v CCD91-72 pixels
Show abstract
The Gaia satellite is a high-precision astrometry, photometry and spectroscopic ESA cornerstone mission, currently
scheduled for launch in 2012. Its primary science drivers are the composition, formation and evolution of the Galaxy.
Gaia will achieve its unprecedented accuracy requirements with detailed calibration and correction for CCD radiation
damage and CCD geometric distortion. In this paper, the third of the series, we present our 3D Silvaco ATLAS model
of the Gaia e2v CCD91-72 pixel. We publish e2v's design model predictions for the capacities of one of Gaia's pixel
features, the supplementary buried channel (SBC), for the first time. Kohley et al. (2009) measured the SBC capacities
of a Gaia CCD to be an order of magnitude smaller than e2v's design. We have found the SBC doping widths that yield
these measured SBC capacities. The widths are systematically 2 μm offset to the nominal widths. These offsets appear
to be uncalibrated systematic offsets in e2v photolithography, which could either be due to systematic stitch alignment
offsets or lateral ABD shield doping diffusion. The range of SBC capacities were used to derive the worst-case random
stitch error between two pixel features within a stitch block to be ±0.25 μm, which cannot explain the systematic offsets.
It is beyond the scope of our pixel model to provide the manufacturing reason for the range of SBC capacities, so it does
not allow us to predict how representative the tested CCD is. This open question has implications for Gaia's radiation
damage and geometric calibration models.
The effects of radiation damage on the spectral resolution of the Chandrayaan-1 x-ray spectrometer
Show abstract
The Chandrayaan-1 X-ray Spectrometer (C1XS) was launched onboard the Indian Space Research Organisation (ISRO)
Chandrayaan-1 lunar mission in October 2008. The instrument consisted of 24 swept-charge device silicon X-ray
detectors providing a total collecting area of ~24 cm2, corresponding to a 14° field of view (FWHM), with the ability to
measure X-rays from 0.8 - 10 keV. During the 10 months the spacecraft was located in orbit around the Moon a number
of solar flare X-ray events were detected, along with calibration data from X-ray sources housed inside the movable door
of the instrument. This paper presents a study of the degradation in spectral resolution of the measured X-ray calibration
lines, comparing those recorded mid way through the mission lifetime with ground based calibration data collected prior
to the launch of the instrument. The radiation environment the detectors were subjected to is discussed in light of the
actual radiation damage effects on the spectral resolution observed in flight.
Charge trap identification for proton-irradiated p+ channel CCDs
Show abstract
Charge trapping in bulk silicon lattice structures is a source of charge transfer inefficiency (CTI) in CCDs. These
traps can be introduced into the lattice by low-energy proton radiation in the space environment, decreasing the
performance of the CCD detectors over time. Detailed knowledge of the inherent trap properties, including energy
level and cross section, is important for understanding the impact of the defects on charge transfer as a function
of operating parameters such as temperature and clocking speeds. This understanding is also important for
mitigation of charge transfer inefficiency through annealing, software correction, or improved device fabrication
techniques. In this paper, we measure the bulk trap properties created by 12.5 MeV proton irradiation on
p+ channel, full-depletion CCDs developed at LBNL. Using the pocket pumping technique, we identify the
majority trap populations responsible for CTI in both the parallel and serial transfer processes. We find the
dominant parallel transfer trap properties are well described by the silicon lattice divacancy trap, in agreement
with other studies. While the properties of the defects responsible for CTI in the serial transfer are more difficult
to measure, we conclude that divacancy-oxygen defect centers would be efficient at our serial clocking rate and
exhibit properties consistent with our serial pocket pumping data.
Electronics for Imagers
Fully digital image sensor employing delta-sigma indirect feedback ADC with high-sensitivity to low-light illuminations for astronomical imaging applications
Show abstract
We describe a CMOS image sensor with column-parallel delta-sigma (ΔΣ) analog-to-digital converter (ADC). The
design employs three transistor pixels (3T1) where the unique configuration of the ΔΣ ADC reduces the noise
contribution of the readout transistor. A 128 x 128 pixel image sensor prototype is fabricated in 0.35μm TSMC
technology. The reset noise and the offset fixed pattern noise (FPN) are removed in the digital domain. The
measured readout noise is 37.8μV for an exposure time of 33ms. The low readout noise allows an improved low
light response in comparison to other state-of-art designs. The design is suitable for applications demanding
excellent low-light response such as astronomical imaging. The sensor has a measured intra-scene dynamic range
(DR) of 91 dB, and a peak signal-to-noise ratio (SNR) of 54 dB.
SIDECAR ASIC at ESO
Show abstract
Teledyne Imaging Sensors (TIS) has developed a CMOS device known as the SIDECAR application-specific integrated
circuit (ASIC). This single chip provides all the functionality of FPA drive electronics to operate visible and infrared
imaging detectors with a fully digital interface. A Teledyne 2K ×2K silicon PIN diode array hybridized to a Hawaii-2RG
multiplexer, the Hybrid Visible Silicon Imager (HyViSI) was read out with the ESO standard IR detector controller
IRACE, which delivers detector limited performance. We have tested the H2RG HyViSI detector with the TIS
SIDECAR ASIC in 32 channel readout mode at cryogenic temperatures. The SIDECAR has been evaluated down to 105
Kelvin operating temperature and performance results have been compared to those obtained with external electronics.
Furthermore ESO has developed its own interface card to replace the JADE USB card provided by Teledyne. The ASIC
controller is now being embedded in the ESO standard VLT hard and software environment. This paper provides an
update on the recent development of the new ESO ASIC interface card. We find that the SIDECAR ASIC provides
performance equal to external electronics.
Description of the UCam detector control system with a particular emphasis to a development of 4K X 4K camera systems
Show abstract
This paper describes the features and functionality of the UCam (UKATC Universal Camera Control and Data
Acquisition) detector control system with a particular emphasis on development and testing of two 4K×4K CCD camera
systems built recently at UKATC and delivered to a group of telescopes in India. These two camera systems use two
variants of an e2v CCD203 device; a 4k×4k standard back-thinned device and a deep depleted silicon device. Apart from
the expected differences with the spectral response of these devices, other performance differences have been observed
between the two systems such as conversion gain non-linearity, electrical crosstalk between outputs, fringing etc. which
are thought to be related to the silicon thickness. Both these detectors show charge trapping during device power on or
when saturated. The effects of this charge trapping and a solution implemented to minimise it will be presented. The
configuration of the UCAM system, custom built detector mount and fanout board and the overall performance of these
camera systems will also be presented.
Reducing the read noise of H2RG detector arrays: eliminating correlated noise with efficient use of reference signals
Show abstract
We present a process for characterizing the correlation properties of the noise in large two-dimensional detector
arrays, and describe an efficient process for its removal. In the case of the 2k × 2k HAWAII-2RG detectors (H2RG)
detectors from Teledyne which are being used on the Near Infrared Spectrograph (NIRSpec) on the James Webb
Space Telescope (JWST), we find that we can reduce the read noise by thirty percent. Noise on large spatial
scales is dramatically reduced. With this relatively simple process, we provide a performance improvement that
is equivalent to a significant increase in telescope collecting area for high resolution spectroscopy with NIRSpec.
Visible Imagers
Photon collider: a four-channel autoguider solution
Show abstract
The "Photon Collider" uses a compact array of four off axis autoguider cameras positioned with independent filtering
and focus. The photon collider is two way symmetric and robustly mounted with the off axis light crossing the science
field which allows the compact single frame construction to have extremely small relative deflections between guide and
science CCDs. The photon collider provides four independent guiding signals with a total of 15 square arc minutes of
sky coverage. These signals allow for simultaneous altitude, azimuth, field rotation and focus guiding. Guide cameras
read out without exposure overhead increasing the tracking cadence. The independent focus allows the photon collider to
maintain in focus guide stars when the main science camera is taking defocused exposures as well as track for telescope
focus changes. Independent filters allow auto guiding in the science camera wavelength bandpass. The four cameras are
controlled with a custom web services interface from a single Linux based industrial PC, and the autoguider mechanism
and telemetry is built around a uCLinux based Analog Devices BlackFin embedded microprocessor. Off axis light is
corrected with a custom meniscus correcting lens. Guide CCDs are cooled with ethylene glycol with an advanced leak
detection system. The photon collider was built for use on Las Cumbres Observatory's 2 meter Faulks telescopes and
currently used to guide the alt-az mount.
Flagging and correction of pattern noise in the Kepler focal plane array
Show abstract
In order for Kepler to achieve its required <20 PPM photometric precision for magnitude 12 and brighter stars,
instrument-induced variations in the CCD readout bias pattern (our "2D black image"), which are either fixed or slowly
varying in time, must be identified and the corresponding pixels either corrected or removed from further data
processing. The two principle sources of these readout bias variations are crosstalk between the 84 science CCDs and the
4 fine guidance sensor (FGS) CCDs and a high frequency amplifier oscillation on <40% of the CCD readout channels.
The crosstalk produces a synchronous pattern in the 2D black image with time-variation observed in <10% of individual
pixel bias histories. We will describe a method of removing the crosstalk signal using continuously-collected data from
masked and over-clocked image regions (our "collateral data"), and occasionally-collected full-frame images and
reverse-clocked readout signals. We use this same set to detect regions affected by the oscillating amplifiers. The
oscillations manifest as time-varying moiré pattern and rolling bands in the affected channels. Because this effect
reduces the performance in only a small fraction of the array at any given time, we have developed an approach for
flagging suspect data. The flags will provide the necessary means to resolve any potential ambiguity between
instrument-induced variations and real photometric variations in a target time series. We will also evaluate the
effectiveness of these techniques using flight data from background and selected target pixels.
X-Ray Detectors III
First results from electrical qualification measurements on DEPFET pixel detector
Petra Majewski,
Ladislav Andricek,
Thomas Lauf,
et al.
Show abstract
We report on the first results from a new setup for electrical qualification measurements of DEPFET pixel detector
matrices. In order to measure the transistor properties of all pixels, the DEPFET device is placed into
a benchtest setup and electrically contacted via a probecard. Using a switch matrix, each pixel of the detector
array can be addressed individually for characterization.
These measurements facilitate to pre-select the best DEPFET matrices as detector device prior to the mounting
of the matrix and allow to investigate topics like the homogeneity of transistor parameters on device, wafer
and batch level in order to learn about the stability and reproducibility of the production process. Especially
with regard to the detector development for the IXO Wide Field Imager (WFI), this yield learning will be an
important tool.
The first electrical qualification measurements with this setup were done on DEPFET macropixel detector flight
hardware, which will form the FPAs of the Mercury Imaging X-ray Spectrometer (MIXS) on board of the 5th
ESA cornerstone mission BepiColombo. The DEPFET array consists of 64×64 macropixel for which the transfer,
output and clear characteristics were measured.
Measurement results for an x-ray 3D-integrated active pixel sensor
Show abstract
We have developed a hybrid Active Pixel Sensor for detecting low energy X-rays. The sensor consists of a silicon
diode detector array built on a high resistivity wafer and an SOI CMOS readout circuit, connected together by
means of unique 3D integration technology developed at MIT Lincoln Laboratory. In this paper we will describe
measurements of sense node capacitance and device depletion depth along with corresponding simulations aimed
to optimize device performance. We also describe race condition in the column decoder and identify ways to
eliminate it in order to reduce fixed pattern noise.
IR Detectors I
Extraction of the frequency spectrum of the noise of a HAWAII2RG NIR detector and impact on low-flux measurements
Show abstract
The readout noise of a H2RG HgCdTe NIR detector from Teledyne is measured at a temperature T=110K.
It is shown that a Fowler mode with n = 240 allows to reach a noise of 2.63e (single read). A description of
the power spectrum in terms of 3 parameters reproduces the variation of the noise as a function the number
of Fowler samples, as well as its dependence on the periodicity of the sampling. The variance of the noise
decreases with frequency with an effective power of 0.62 in our measurement domain. The behaviour of the
detector under different experimental conditions can then be predicted.
Development of high-speed, low-noise NIR HgCdTe avalanche photodiode arrays for adaptive optics and interferometry
Show abstract
The most promising way to overcome the CMOS noise barrier of infrared AO sensors is the amplification of the photoelectron
signal directly at the point of absorption inside the infrared pixel by means of the avalanche gain. HgCdTe eAPD
arrays with cut off wavelengths of λc ~2.64 μm produced by SELEX-Galileo have been evaluated at ESO. The arrays
were hybridized to an existing non-optimized ROIC developed for laser gated imaging which has a format of 320×256
pixels and four parallel video outputs. The avalanche gain makes it possible to reduce the read noise to < 7 e rms. The
dark current requirements of IR wavefront sensing are also met.
Recent focal plane arrays for astronomy and remote sensing applications at RVS
Show abstract
Raytheon Vision Systems (RVS) arrays are being deployed world-wide in ground based and space based platforms.
RVS has a family of high performance visible through far infrared detector arrays for astronomy and civil space
applications. Unique and off-the-shelf product lines are readily available to the community. Large sensor chip
assemblies using various detector materials like Si PIN, HgCdTe, InSb, and Si:As IBC, covering a detection range from
visible (400nm) to mid-wave infrared (28μm, MWIR) have been demonstrated with excellent quantum efficiency, dark
current, and uniformity. These focal plane arrays have been designed using state-of-the-art low noise, low power, and
radiation hardened readout integrated circuits. Complete with optical filters, opto-mechanical packaging, active thermal
cooling with matching thermal straps, and optional electronics, RVS provides complete solutions for a multitude of
sensor types and mission objectives. This paper describes the recent developments of focal plane assemblies for
upcoming missions and telescope platforms.
IR Detectors II
A method for the characterization of sub-pixel response of near-infrared detectors
Show abstract
Many future space telescope missions are designed as wide-field surveys. The increased area of the survey is often
achieved by increasing the plate scale of the detectors. This can result in under-sampled instruments. Under these
conditions response variations within an individual pixel degrade photometric and shape information of observed
astronomical sources. These effects can be corrected for by mapping the sub-pixel response of all pixels on a detector.
Measuring sub-pixel sensitivity by projecting a single, micron-size spot is effective in understanding intrapixel response
variations, but the time required to create a detector-wide map is prohibitive. The existing Spot-O-Matic single spot
projector concept, has been extended to the design of a multi-spot projector, the Spots-O-Matic, enabling the mapping of
an entire detector. This new projector is under development to achieve the small spot size required for pixel
characterization over the field of view of an entire detector.
Investigating reciprocity failure in 1.7-micron cut-off HgCdTe detectors
Show abstract
Flux dependent non-linearity (reciprocity failure) in HgCdTe NIR detectors with 1.7 μm cut-off was investigated.
A dedicated test station was designed and built to measure reciprocity failure over the full dynamic range of near
infrared detectors. For flux levels between 1 and 100,000 photons/sec a limiting sensitivity to reciprocity failure
of 0.3 %/decade was achieved. First measurements on several engineering grade 1.7 μm cut-off HgCdTe detectors
show a wide range of reciprocity failure, from less than 0.5 %/decade to about 10%/decade. For at least two
of the tested detectors, significant spatial variation in the effect was observed. No indication for wavelength
dependency was found. The origin of reciprocity failure is currently not well understood. In this paper we
present details of our experimental set-up and show the results of measurements for several detectors.
Calibration of ultra-low infrared power at NIST
Show abstract
The Low Background Infrared (LBIR) facility has developed and tested the components of a new detector for calibration
of infrared greater than 1 pW, with 0.1 % uncertainty. Calibration of such low powers could be valuable for the
quantitative study of weak astronomical sources in the infrared. The pW-ACR is an absolute cryogenic radiometer
(ACR) employing a high resolution transition edge sensor (TES) thermometer, ultra-weak thermal link and miniaturized
receiver to achieve a noise level of around 1 fW at a temperature of 2 K. The novel thermometer employs the
superconducting transition of a tin (Sn) core and has demonstrated a temperature noise floor less than 3 nK/Hz1/2. Using
an applied magnetic field from an integrated solenoid to suppress the Sn transition temperature, the operating
temperature of the thermometer can be tuned to any temperature below 3.6 K. The conical receiver is coated on the
inside with infrared-absorbing paint and has a demonstrated absorptivity of 99.94 % at 10.6 μm. The thermal link is
made from a thin-walled polyimide tube and has exhibited very low thermal conductance near 2x10-7 W/K. In tests with
a heater mounted on the receiver, the receiver/thermal-link assembly demonstrated a thermal time constant of about 15 s.
Based on these experimental results, it is estimated that an ACR containing these components can achieve noise levels
below 1 fW, and the design of a radiometer merging the new thermometer, receiver and thermal link will be discussed.
Characterization and performance of the 4k x 4k Hawaii-2RG Mosaic for PANIC
Vianak Naranjo,
Ulrich Mall,
José Ricardo Ramos,
et al.
Show abstract
PANIC, the PAnoramic Near-Infrared Camera for Calar Alto, is one of the next generation instruments for this
observatory. In order to cover a field of view of approximately 30 arcmin, PANIC uses a mosaic of four 2k x 2k
HAWAII-2RG arrays from Teledyne. This document presents the preliminary results of the basic characterization of the
mosaic. The performance of the system as a whole, as well as the in-house readout electronics and software capabilities
will also be briefly discussed.
Performance evaluation of 5 µm cut-off Hawaii-2RG detectors using the fast readout amplifiers
Show abstract
ESO has begun an ambitious mid-IR detector program with the funded development of a new Raytheon detector
(AQUARIUS) and the further development of instruments to use 5 μm cut-off material Teledyne HAWAII-2RG
detectors. Both these detector types are capable of extremely high readout speeds, through multiple readout ports,
resulting in data rates in excess of 250 Mbytes/s. This has required further development of our new detector controller
system (NGC) to allow it to operate at these very high pixel data rates. This has also entailed the development of new
high speed pre-amplifiers which can operate at 60K to allow us to drive the long cable runs typical of an astronomical
instrument. We report on the development and performance of our new higher speed NGC systems with particular regard
to the operation of a Hawaii-2RG detector configured to use its high speed readout stages. We will present data on the
performance of such at device, configured to operate in both slow and fast readout modes, with particular regard to noise
versus pixel speed and also the optimization of the voltages.
Detector characterization for the JWST fine guidance sensor
Show abstract
The James Webb Space Telescope Fine Guidance Sensor makes use of three 2048×2048 five micron cutoff HAWAII-
2RG HgCdTe detectors from Teledyne Imaging Systems. The FGS consists of two Guider channels and one Tunable
Filter Imager (TFI) channel. We report here on our efforts to optimize the performance of the FGS detector sub-system
consisting of the detector arrays, the Teledyne SIDECAR ASIC, and the FGS specific SIDECAR Control Electronics.
The FGS-Guider has a number of unique readout modes which are required to support observatory operations, requiring
different optimizations for these readout modes compared to those required for science observations with the TFI.
Effect of dislocations on dark current in LWIR HgCdTe photodiodes
Show abstract
In recent years, Teledyne Imaging Sensors has begun development of Long Wave Infrared (LWIR) HgCdTe
Detector Arrays for low background astronomical applications, which have a high percentage of low dark current
pixels but a substantial high dark current tail. Characterization of high dark current pixels in these devices has
produced I-V curves with unusual behaviors. The typical theories of diffusion current, tunneling current, and
even surface current have been unable to accurately model the observed I-V curves. By modeling dislocations in
and near the p-n junction as trapping sites and those near the surface as leakage channels, the behavior of these
unusual I-V curves is successfully modeled, pointing to the need to reduce the number of these dislocations in
order to produce LWIR HgCdTe photodiodes exhibiting very low dark current with sufficient well depth.
Curved infrared detectors: application to spectrometry and astronomy
D. Dumas,
M. Fendler,
F. Berger,
et al.
Show abstract
The traditional design of optical systems is severely complicated by the curved shape of the image surface which
has to be recorded on a planar retina. This constraint decreases the image quality; optical elements are then
added to avoid aberrations and lead to increase the dimensions of the system. However, miniaturization could be
achieved, without decreasing resolution and sensibility, by recording the image surface on a curved retina. The
optical advantages of curved sensors have been demonstrated; the simplification leads to scale down the entire
system. Moreover, the hemispherical shape increases the field of view (FOV).
In this paper the advantages of curved focal plane will be detailed through two applications: spectrometry and
large FOV telescopes. In astronomy, large FOV and miniaturization with good resolution can only be achieved
by curving the focal plane; the difficulty is to curve in a hemispherical shape large detectors. The advantages are
highlighted by the European Extremely Large Telescope (E-ELT) project.
Despite this high interest in curved detectors, only few articles are dedicated to this hemispherical shape
technology. Some solutions exist, which mainly consist in structuring the die in sub-devices. We propose a
solution to curve an IR sensor with a fill factor equal to 100%. To do so, we developed a dedicated bonding
process which allows curving silicon using its mechanical properties. A curved uncooled infrared detector has
been performed without mechanical and electrical damage.
Poster Session
Cryogenic design of the EMCCD cameras for the Brazilian tunable filter imager
Show abstract
In this paper we present the cryogenic design of the EMCCD (Electron Multiplication Charged Couple Device) cameras
for the Brazilian Tunable Filter Imager instrument for the 4 meters SOAR telescope in Chile. The camera uses a E2V
1600 × 1600 pixels full-frame device, which is controlled by the new CCCP (CCD Controller for Counting Photons), an
EMCCD controller developed by the University of Montreal. We present the design of the camera, its thermal analysis
and cryogenic performance.
New developments for detector controllers at NOAO
Show abstract
The Torrent detector control system is being developed at NOAO as a follow-on to the MONSOON systems that
have been used successfully for instruments at several institutions. The poster will cover the evolution of
MONSOON into Torrent and will cover: Motivations, What's gained/What's lost, Major Technological Differences,
Goals, plans and first users.
Method to implement the CCD timing generator based on FPGA
Show abstract
With the advance of the PFPA technology, the design methodology of digital systems is changing. In recent years we
develop a method to implement the CCD timing generator based on FPGA and VHDL. This paper presents the principles
and implementation skills of the method. Taking a developed camera as an example, we introduce the structure, input
and output clocks/signals of a timing generator implemented in the camera. The generator is composed of a top module
and a bottom module. The bottom one is made up of 4 sub-modules which correspond to 4 different operation modes.
The modules are implemented by 5 VHDL programs. Frame charts of the architecture of these programs are shown in
the paper. We also describe implementation steps of the timing generator in Quartus II, and the interconnections between
the generator and a Nios soft core processor which is the controller of this generator. Some test results are presented in
the end.
Repackaging and characterizing of a HgCdTe CMOS infrared camera for the New Solar Telescope
Show abstract
The 1.6-meter New Solar Telescope (NST) is currently the world's largest aperture solar telescope. The NST
is newly built at Big Bear Solar Observatory (BBSO). Among other instruments, the NST is equipped with
several focal plane instruments operating in the near infrared (NIR). In order to satisfy the diverse observational
requirements of these scientific instruments, a 1024 × 1024 HgCdTe TCM8600 CMOS camera manufactured by
Rockwell Scientific Company has been repackaged and upgraded at Infrared Laboratories Inc. A new ND-5 dewar
was designed to house the TCM8600 array with a low background filter wheel, inverted operation and at least 12
hours of hold time between fills. The repackaged camera will be used for high-resolution NIR photometry at the
NST Nasmyth focus on the telescope and high-precision NIR spectro-polarimetry in the NST Coud´e Lab below.
In March 2010, this repackaged camera was characterized in the Coud´e Lab at BBSO. This paper presents the
design of new dewar, the detailed process of repackaging and characterizing the camera, and a series of test
results.
Reciprocity failure in 1.7 µm cut-off HgCdTe detectors
Show abstract
The Detector Characterization Laboratory at NASA/GSFC has investigated the reciprocity failure characteristics of
1.7μm cut-off HgCdTe devices provided by Teledyne Imaging Sensors to the Hubble Space Telescope (HST) Wide
Field Camera 3 (WFC3) project. The reciprocity failure follows a power law behavior over the range of fluxes tested
(0.1-104 photons/second). The slope of the power law varies among detectors, ranging from ~0.3-1%/dex at 1.0μm,
which is much smaller than the ~6%/dex effect observed with the HST NICMOS 2.5μm cut-off detectors. In addition,
the reciprocity failure exhibits no wavelength dependence, although only a restricted range of wavelengths (0.85-1.0μm)
has been explored to date. Despite its relatively small magnitude, reciprocity failure is nevertheless an important effect in
the calibration of WFC3 data, as well as in other applications in which there is a large difference in flux between the
photometric standards and the scientific sources of interest.
Characterization of multicolor type-II InAs/GaSb strained-layer superlattice photodetectors for use in astronomical observation
Show abstract
We report on the testing of a set of InAs/GaSb multicolor strained-layer superlattice photodetectors and Dotin-
Well detectors grown with InAs dots in InGaAs/GaAs wells fabricated by the Center for High Technology
Materials at the University of New Mexico. These devices are 2-color devices sensitive to near-IR and mid-IR
wavelengths. The wavelength sensitivities of these devices are a function of the applied forward and reverse bias.
We present measurements of the dark current and relative spectral response of these photodetectors measured
at both cryogenic and room temperatures.
Testing of an extended-wavelength InGaAs array in an astronomical spectrograph
Show abstract
We present the integration of a low dark current extended wavelength (2.3μm cutoff) InGaAs array into the
Cornell-Massachusetts Slit Spectrograph (CorMASS) spectrograph. The InGaAs array was fabricated onto a SB-
206 512×512 readout integrated circuit (ROIC) by Goodrich/Sensors Unlimited and subsequently went through a
series of laboratory characterization tests at the University of Virginia demonstrating dark current performance
of better than 10 e-/s. The InGaAs array is adapted for use with the CorMASS to verify its performance in a
proven astronomical instrument, and for eventual deployment to a telescope to test stability and performance.
Radiation hardness studies of InGaAs photodiodes at 30, 52, & 98 MeV and fluences to 10^10 protons/cm^2
Show abstract
We report the effects of radiation damage due to ionizing protons on InGaAs photodiodes. The photodiodes
were irradiated at energies of 30, 52, and 98 MeV and fluences up to 1010 protons/cm2 in experiments at the
Indiana University Cyclotron Facility. The photodiodes were tested for changes in their dark current, their
relative responsivity as a function of wavelength from 1000 - 1600 nm, and their absolute responsivity in narrow
bandpasses spread throughout the same wavelength region. The measurements were all made with detectors
traceable to NIST standards. At these exposures and energies, the most significant effects are seen in the dark
current levels.
The challenge of highly curved monolithic imaging detectors
Show abstract
In a recent optical design study of CODEX - a visible spectrograph planned for the European Extremely Large
Telescope (E-ELT) - it was determined that a significant simplification of the optical design - accompanied by an
improvement of the image quality - could be achieved through the application of large format (90mm square) concave
spherically curved detectors with a low radius of curvature (500 to 250mm).
Current assemblies of image sensors and optics rely on the optics to project a corrected image onto a flat detector. While
scientific large-size CCDs (49mm square) have been produced unintentionally with a spherical radius of convex
curvature of around 5m, in the past most efforts have concentrated onto flattening the light-sensitive detector silicon area
as best as possible for both scientific state-of-the-art systems, as well as commercial low-cost consumer products. In
some cases curved focal planes are mosaicked out of individual flat detectors, but a standard method to derive individual
spherically curved large size detectors has not been demonstrated.
This paper summarizes important developments in the area of curved detectors in the past and their different technical
approaches mostly linked to specific thinning processes. ESO's specifications for an ongoing feasibility study are
presented. First results of the latter are described with a link to theoretical and practical examinations of currently
available technology to implement curved CCD and CMOS detectors for scientific applications.
Centroid precision as a function of total counts in a windowed CMOS image of a point source
Show abstract
We obtained 960,200 22-by-22-pixel windowed images of a pinhole spot using the Teledyne H2RG CMOS detector
with un-cooled SIDECAR readout. We performed an analysis to determine the precision we might expect in the position
error signals to a telescope's guider system. We find that, under non-optimized operating conditions, the error in the
computed centroid is strongly dependent on the total counts in the point image only below a certain threshold,
approximately 50,000 photo-electrons. The LSST guider camera specification currently requires a 0.04 arcsecond error
at 10 Hertz. Given the performance measured here, this specification can be delivered with a single star at 14th to 18th
magnitude, depending on the passband.
Characterization and performance of hyper Suprime-Cam CCD
Show abstract
Hyper Suprime-Cam (HSC) is a second-generation wide field imaging camera for Subaru telescope with 10 times
wider field of view (FOV) compared with Suprime-Cam (SC) currently being used. HSC makes the survey
speed considerably faster than SC, while maintaining the high image quality of SC. The 1.5 degrees in diameter
FOV is covered with 116 of 2K × 4K fully depleted back-illuminated CCDs with 15 μm pixels developed by
HAMAMATSU Photonics K. K. and National Astronomical Observatory of Japan (NAOJ). The CCDs for HSC
are designed to have higher quantum efficiency than those for SC in a wider range in the visible wavelengths,
especially in the blue region.
We at NAOJ have started acceptance inspection of the CCDs being delivered from HAMAMATSU. We used
the X-ray source of 55Fe and the LED to measure charge transfer efficiency, readout noise, linearity, and full-well
capacity of 33 CCDs. In addition, we measured the quantum efficiency of 7 CCDs. We confirmed all the CCDs
have good performances and quality. In this paper, we report the results from the acceptance inspection and
characterization of these CCDs.
CCD imaging technique for moving objects in the field of view
Show abstract
In the optical position observations to the near earth objects, the differential measurement methods are commonly used to
improve positional accuracy, in which the object positions are calibrated by the star positions. However, due to the
characteristics of motion of the observed object and the restrictions on current CCD imaging technology, single
measurement accuracy of these methods for the object is not high. This is because there is relative motion between the
calibration stars and the observed object in the field of view of the telescope. This paper analyzes characteristics of
relative movement of the space objects on the Geosynchronous Earth Orbit and the stars in the field of view of an
equatorial telescope, and CCD imaging effects for these objects and stars, then present a new CCD imaging technique for
moving objects and stationary objects. One half of the CCD photosensitive area is used to acquire images of the moving
objects in the field of view in drift scan mode, the other half to take simultaneously images of the stationary objects in
the field of view in stare mode. Discussions about possibilities for developing this camera and its applications are
presented. A prototype camera controller has been developed in our laboratory. The paper also describes the structure of
the camera controller, the implementation method and skills, and some experimental results.
Interpixel crosstalk in a 3D-integrated active pixel sensor for x-ray detection
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MIT Lincoln Laboratories and MIT Kavli Institute for Astrophysics and Space Research have developed an
active pixel sensor for use as a photon counting device for imaging spectroscopy in the soft X-ray band. A
silicon-on-insulator (SOI) readout circuit was integrated with a high-resistivity silicon diode detector array using
a per-pixel 3D integration technique developed at Lincoln Laboratory. We have tested these devices at 5.9 keV
and 1.5 keV. Here we examine the interpixel cross-talk measured with 5.9 keV X-rays.
Space-qualified, abuttable packaging for LBNL p-Channel CCDs, Part I
C. Baltay,
W. Emmet,
D. Rabinowitz,
et al.
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We have developed a design for packaging Charged Coupled Devices (CCDs) for use as optical imaging devices for
space applications, although the design is also useful for any large ground-based mosaic. We have constructed and
assembled prototype packages using this design. Testing of these prototypes has demonstrated that these packaged
CCDs are flight worthy. The design, construction, and testing of these prototypes are described in this article.
Radiation testing of CCDs for space applications
C. Baltay,
A. Bauer,
W. Emmet,
et al.
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This article reports the results of radiation resistance tests of fully depleted p-channel Charge Coupled Devices (CCDs)
developed at the Lawrence Berkeley National Laboratory for imaging applications in space. Several such devices were
irradiated by 12 MeV protons at the tandem accelerator at the Wright Nuclear Structure Laboratory at Yale University
by doses up to 8 x 1010 protons/cm2. The equivalent dose at an orbit near L2 for a six year mission in space was
estimated to be an equivalent 7.3 x 108 12.5 MeV protons/cm2. The performance of the CCDs was measured both before
and after irradiation. The charge transfer efficiency CTE was degraded from 0.999999 before irradiation to 0.999996
after the expected six year dose. The dark current, which was 3 electrons/pixel/hour before irradiation, is degraded to an
equilibrium rate of 15 electrons/pixel/hour in orbit. We conclude that the performance of these devices is quite
acceptable for high precision imaging in a space mission.
New optical modalities utilizing curved focal plane imaging detector devices and large arrays for terrestrial and spaceborne telescopes
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As terrestrial and spaceborne astronomical telescopes advance in multi-functional design sophistication,
incorporating greater spectral resolutions, the utilization of curved focal plane ccd and cmos imaging
detectors, contoured to match the telescope's Petzval field of curvature, provides a fundamental and novel
optical simplicity facilitating new imaging frontiers in astronomical research. For space based telescopes,
curved focal plane detector devices require significantly fewer optics than their flat counterparts, which
require field flattening optics, in achieving maximum imaging resolutions for adjoining spectrometers or
imaging cameras. consequently, with fewer optics comes greater room to place other optics within the same
space to accomplish other tasks, providing much greater diversification of observing functions and techniques
reserved simultaneously for the telescope. Included within this is the operational capability of producing
multi-wavelength spectrometers gathering data concurrently at a multitude of selected wavelengths, with
greater sensitivity, reliability, size reduction, and operational longevity of the restructured optical system.
Specialized applications involving optical interferometry are also achievable with further enhancements when
the curved detectors are applied specifically to refine or maximize detection of fringes, and when employing
occulting mask algorithms for existing light paths. for planetary surface mapping space probes, curved focal
plane detection provides real-time 3D multi-perspective image acquisition for streaming 3D data sets,
replacing onboard or remote computationally intensive 3D reconstructions used for examining terrestrial
surface features performed with corresponding flat detectors. For earth based telescopes, where mass of the
telescope's optics are not so constrained, more degrees of freedom are also part of the benefits introduced by
curved focal plane detector device optimization. Associated with the very large Petzval radii of curvature for
very large and extreme telescopes within this class are wide field spatial distortions which are instantaneously
corrected when arrays of curved CCD's or CMOS devices are joined homogeneously and precisely together
along the converging field of curvature, without field flattening optics, insuring complete full field detection
superior to flat facet detectors which compromise the telescope's imaging field curvature detection abilities.
Controller and data acquisition system for SIDECAR ASIC driven HAWAII detectors
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SIDECAR is an Application Specific Integrated Circuit (ASIC), which can be used for control and data acquisition from
near-IR HAWAII detectors offered by Teledyne Imaging Sensors (TIS), USA. The standard interfaces provided by
Teledyne are COM API and socket servers running under MS Windows platform. These interfaces communicate to the
ASIC (and the detector) through an intermediate card called JWST ASIC Drive Electronics (JADE2). As part of an
ongoing programme of several years, for developing astronomical focal plane array (CCDs, CMOS and Hybrid)
controllers and data acquisition systems (CDAQs), IUCAA is currently developing the next generation controllers
employing Virtex-5 family FPGA devices. We present here the capabilities which are built into these new CDAQs for
handling HAWAII detectors. In our system, the computer which hosts the application programme, user interface and
device drivers runs on a Linux platform. It communicates through a hot-pluggable USB interface (with an optional
optical fibre extender) to the FPGA-based card which replaces the JADE2. The FPGA board in turn, controls the
SIDECAR ASIC and through it a HAWAII-2RG detector, both of which are located in a cryogenic test Dewar set up
which is liquid nitrogen cooled. The system can acquire data over 1, 4, or 32 readout channels, with or without binning,
at different speeds, can define sub-regions for readout, offers various readout schemes like Fowler sampling, up-theramp
etc. In this paper, we present the performance results obtained from a prototype system.