This PDF file contains the front matter associated with SPIE Proceedings Volume 7021, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Proc. SPIE 7021, Teledyne Imaging Sensors: silicon CMOS imaging technologies for x-ray, UV, visible, and near infrared, 702102 (16 July 2008); doi: 10.1117/12.792316
Teledyne Imaging Sensors develops and produces high performance silicon-based CMOS image sensors, with associated
electronics and packaging for astronomy and civil space. Teledyne's silicon detector sensors use two technologies:
monolithic CMOS, and silicon PIN hybrid CMOS. Teledyne's monolithic CMOS sensors are large (up to 59 million
pixels), low noise (2.8 e- readout noise demonstrated, 1-2 e- noise in development), low dark current (<10 pA/cm2 at
295K) and can provide in-pixel snapshot shuttering with >103 extinction and microsecond time resolution. The QE
limitation of frontside-illuminated CMOS is being addressed with specialized microlenses and backside illumination. A
monolithic CMOS imager is under development for laser guide star wavefront sensing. Teledyne's hybrid silicon PIN
CMOS sensors, called HyViSITM, provide high QE for the
x-ray through near IR spectral range and large arrays
(2K×2K, 4K×4K) are being produced with >99.9% operability. HyViSI dark current is 5-10 nA/cm2 (298K), and further reduction is expected from ongoing development. HyViSI presently achieves <10 e- readout noise, and new high speed
HyViSI arrays being produced in 2008 should achieve <4 e- readout noise at 900 Hz frame rate. A Teledyne 640×480
pixel HyViSI array is operating in the Mars Reconnaissance Orbiter, a 1K×1K HyViSI array will be launched in 2008 in
the Orbiting Carbon Observatory, and HyViSI arrays are under test at several astronomical observatories. The
advantages of CMOS in comparison to CCD include programmable readout modes, faster readout, lower power,
radiation hardness, and the ability to put specialized processing within each pixel. We present one example of in-pixel
processing: event driven readout that is optimal for lightning detection and x-ray imaging.
We present the design and test results of a prototype 4T CMOS image sensor fabricated in 0.18-μm technology
featuring 20 different 6.5 μm pixel pitch designs. We review the measured data which clearly show the impact of the
pixel topologies on sensor performance parameters such as conversion gain, read noise, dark current, full well capacity,
non-linearity, PRNU, DSNU, image lag, QE and MTF. Read noise of less than 1.5e- rms and peak QE greater than
70%, with microlens, are reported.
Electronic coupling effects such as Inter-Pixel Capacitance (IPC) affect the quantitative interpretation of image data
from CMOS, hybrid visible and infrared imagers alike. Existing methods of characterizing IPC do not provide a map of
the spatial variation of IPC over all pixels. We demonstrate a deterministic method that provides a direct quantitative
map of the crosstalk across an imager. The approach requires only the ability to reset single pixels to an arbitrary
voltage, different from the rest of the imager. No illumination source is required. Mapping IPC independently for each
pixel is also made practical by the greater S/N ratio achievable for an electrical stimulus than for an optical stimulus,
which is subject to both Poisson statistics and diffusion effects of photo-generated charge. The data we present illustrates
a more complex picture of IPC in Teledyne HgCdTe and HyViSi focal plane arrays than is presently understood,
including the presence of a newly discovered, long range IPC in the HyViSi FPA that extends tens of pixels in distance,
likely stemming from extended field effects in the fully depleted substrate. The sensitivity of the measurement approach
has been shown to be good enough to distinguish spatial structure in IPC of the order of 0.1%.
The Pan-STARRS project has completed its first 1.4 gigapixel mosaic focalplane CCD camera using 60 Orthogonal Transfer
Arrays (OTAs). The devices are the second of a series of planned development lots. Several novel properties were
implemented into their design including 4 phase pixels for on-detector tip-tilt image compensation, selectable region logic
for standby or active operation, relatively high output amplifier count, close four side buttable packaging and deep depletion
construction. The testing and operational challenges of deploying these OTAs required enhancements and new approaches
to hardware and software. We compare performance achieved with that which was predicted, and discuss on-sky results,
tools developed, shortcomings, and plans for future OTA features and improvements.
We present characterization methods and results on a number of new devices produced specifically to address LSST's
performance goals, including flatness, QE, PSF, dark current, read noise, CTE, cosmetics, and crosstalk. The results
indicate that commercially produced, thick n-channel over-depleted CCDs with excellent red response can achieve tight
PSF at moderate applied substrate bias with no evidence of persistent image artifacts. We will also report ongoing
studies of mosaic assembly techniques to achieve chip-to-chip
co-planarity, high fill factor, and thermal stability.
DECam is a 520 Mpix, 3 square-deg FOV imager being built for the Blanco 4m Telescope at CTIO. This facility
instrument will be used for the "Dark Energy Survey" of the southern galactic cap. DECam has chosen 250 μm thick
CCDs, developed at LBNL, with good QE in the near IR for the focal plane. In this work we present the characterization
of these detectors done by the DES team, and compare it to the DECam technical requirements. The results demonstrate
that the detectors satisfy the needs for instrument.
As is only fitting, the largest Optical/Infrared Telescope (the Large Binocular Telescope, LBT) has the two largest
telescope-mounted spectrographs (MODS) and the MODS's have the four largest scientific CCDs. We describe herein
the design, fabrication and early use of the e2v CCD231-68 8k × 3k 15 micron back-illuminated detector designed
specifically for low and intermediate resolution multi-object spectroscopy on large telescopes. The 123 mm length of
the CCD231-68 is the largest of any scientific CCD. The device can be read out in full frame mode to cover the whole
6 arc-min slit length of MODS, in full frame mode for multi-object spectroscopy with short slits, or in split frame
transfer mode to allow readout while integrating subsequent exposures. The four very low noise (<2 e- RMS at 100
kPixels/second) outputs are located at the ends of the four 4k serial registers. Excellent CTE (five-9s5 per Pixel)
insures good photometric accuracy across the device. Backthinned red and blue optimized variants are used on the
corresponding channels of both MODS.
We present the design and performance of the prototype Visible Integral-field Replicable Unit Spectrograph
(VIRUS-P) camera. Commissioned in 2007, VIRUS-P is the prototype for 150+ identical fiber-fed integral field
spectrographs for the Hobby-Eberly Telescope Dark Energy Experiment. With minimal complexity, the gimbal
mounted, double-Schmidt design achieves high on-sky throughput, image quality, contrast, and stability with novel
optics, coatings, baffling, and minimization of obscuration. The system corrector working for both the collimator
and f / 1.33 vacuum Schmidt camera serves as the cryostat window while a 49 mm square aspheric field flattener sets
the central obscuration. The mount, electronics, and cooling of the 2k × 2k, Fairchild Imaging CCD3041-BI fit in
the field-flattener footprint. Ultra-black knife edge baffles at the corrector, spider, and adjustable mirror, and a
detector mask, match the optical footprints at each location and help maximize the 94% contrast between 245
spectra. An optimally stiff and light symmetric four vane stainless steel spider supports the CCD which is thermally
isolated with an equally stiff Ultem-1000 structure. The detector/field flattener spacing is maintained to 1 μm for all
camera orientations and repeatably reassembled to 12 μm. Invar rods in tension hold the camera focus to ±4 μm
over a -5-25 °C temperature range. Delivering a read noise of 4.2 e- RMS, sCTE of 1-10-5 , and pCTE of
1-10-6 at
100 kpix/s, the McDonald V2 controller also helps to achieve a 38 hr hold time with 3 L of LN2 while maintaining
the detector temperature setpoint to 150 μK (5σ RMS).
The Las Cumbres Observatory Global Telescope Network (LCOGT) is an ambitious project to build and operate,
within 5 years, a worldwide robotic network of 50 0.4, 1, and 2 m telescopes sharing identical instrumentation and
optimized for precision photometry of time-varying sources. The telescopes, instrumentation, and software are all
developed in house with two 2 m telescopes already installed. The LCOGT Imaging Lab is responsible for assembly
and characterization of the network's cameras and instrumentation. In addition to a fully equipped CNC machine
shop, two electronics labs, and a future optics lab, the Imaging Lab is designed from the ground up to be a superb
environment for bare detectors, precision filters, and assembled instruments. At the heart of the lab is an ISO class 5
cleanroom with full ionization. Surrounding this, the class 7 main lab houses equipment for detector
characterization including QE and CTE, and equipment for measuring transmission and reflection of optics.
Although the first science cameras installed, two TEC cooled e2v 42-40 deep depletion based units and two
CryoTiger cooled Fairchild Imaging CCD486-BI based units, are from outside manufacturers, their 18 position filter
wheels and the remainder of the network's science cameras, controllers, and instrumentation will be built in house.
Currently being designed, the first generation LCOGT cameras for the network's 1 m telescopes use existing
CCD486-BI devices and an in-house controller. Additionally, the controller uses digital signal processing to
optimize readout noise vs. speed, and all instrumentation uses embedded microprocessors for communication over
ethernet.
Proc. SPIE 7021, ULTRASPEC: an electron multiplication CCD camera for very low light level high speed astronomical spectrometry, 70210B (22 July 2008); doi: 10.1117/12.790376
We present the design, characteristics and astronomical results for ULTRASPEC, a high speed Electron Multiplication
CCD (EMCCD) camera using an E2VCCD201 (1K frame transfer device), developed to prove the performance of this
new optical detector technology in astronomical spectrometry, particularly in the high speed, low light level regime. We
present both modelled and real data for these detectors with particular regard to avalanche gain and clock induced charge
(CIC). We present first light results from the camera as used on the EFOSC-2 instrument at the ESO 3.6 metre telescope
in La Silla. We also present the design for a proposed new 4Kx2K frame transfer EMCCD.
ESO and JRA2 OPTICON have jointly funded e2v technologies to develop a custom CCD for Adaptive Optic Wave
Front Sensor (AO WFS) applications. The device, called CCD220, is a compact Peltier-cooled 240×240 pixel frametransfer
8-output back-illuminated sensor. Using the electron-multiplying technology of L3Vision detectors, the device
is designed to achieve sub-electron read noise at frame rates from 25 Hz to 1,500 Hz and dark current lower than 0.01
e-/pixel/frame. The development has many unique features. To obtain high frame rates, multiple EMCCD gain registers
and metal buttressing of row clock lines are used. The baseline device is built in standard silicon. In addition, two
speculative variants have been built; deep depletion silicon devices to improve red response and devices with an
electronic shutter to extend use to Rayleigh and Pulsed Laser Guide Star applications. These are all firsts for L3Vision
CCDs.
These CCD220 detectors have now been fabricated by e2v technologies. This paper describes the design of the device,
technology trade-offs, and progress to date. A Test Camera, called "OCam", has been specially designed and built for
these sensors. Main features of the OCam camera are extensively described in this paper, together with first light images
obtained with the CCD220.
Teledyne Imaging Sensors develops and produces high performance infrared sensors, electronics and packaging for
astronomy and civil space. These IR sensors are hybrid CMOS arrays, with HgCdTe used for light detection and a
silicon integrated circuit for signal readout. Teledyne manufactures IR sensors in a variety of sizes and formats.
Currently, the most advanced sensors are based on the Hawaii-2RG (H2RG), 2K×2K array with 18 μm pixel pitch. The
HgCdTe detector achieves very low dark current (<0.01 e-/pixel/sec) and high quantum efficiency (80-90%) over a wide
bandpass. Substrate-removed HgCdTe can simultaneously detect visible and infrared light, enabling spectrographs to
use a single focal plane array (FPA) for Visible-IR sensitivity. The SIDECARTM ASIC provides focal plane electronics
on a chip, operating in cryogenic environments with very low power (<11 mW). The H2RG and SIDECARTM have been
qualified to NASA Technology Readiness Level 6 (TRL-6). Teledyne continues to advance the state-of-the-art and is
producing a high speed, low noise array designed for IR wavefront sensing. Teledyne is also developing a 4K×4K, 15
µm pixel infrared array that will be a cost effective module for the large focal planes of the Extremely Large Telescopes
and future generation space astronomy missions.
Proc. SPIE 7021, Development of non-hybridised HgCdTe detectors for the next generation of astronomical instrumentation, 70210I (22 July 2008); doi: 10.1117/12.787500
The superb image quality that is predicted, and even demanded, for the next generation of Extremely Large Telescopes
(ELT) presents a potential crisis in terms of the sheer number of detectors that may be required. Developments in
infrared technology have progressed dramatically in recent years, but a substantial reduction in the cost per pixel of these
IR arrays will be necessary to permit full exploitation of the capabilities of these telescopes. Here we present an outline
and progress report of an initiative to develop a new generation of astronomical grade Cadmium Mercury Telluride
(HgCdTe) array detectors using a novel technique which enables direct growth of the sensor diodes onto the Read Out
Integrated Circuit (ROIC). This technique removes the need to hybridise the detector material to a separate Silicon
readout circuit and provides a route to very large monolithic arrays. We present preliminary growth and design
simulation results for devices based on this technique, and discuss the prospects for deployment of this technology in the
era of extremely large telescopes.
Image persistence can produce systematic errors, which remain significant in some applications even when buried in
noise. Ideally the image persistence amplitude, linearity and decay over time could be calibrated independently for each
pixel to levels well below the noise floor, however averaging multiple measurements to characterize persistence to this
accuracy is impractical due to the long time scales for the decay and the need to emulate the exposure and readout timing
of the observations to be calibrated. We examine a compromise where the initial persistence response is characterized
independently for each pixel but the latter parts of the decay are assumed to follow the mean decay curve. When
averaged spatially, persistence increases monotonically with stimulus amplitude until the photodiodes approach forward
bias. For several Teledyne 1.7 μm cutoff HgCdTe detectors tested, persistence is linear over most of the normal signal
range. We characterize the temporal response, and examine the dependence of charge emission time constants on total
stimulus duration. We describe the suppression of persistence by signal in the current frame and begin to examine the
superposition of the decay curves from multiple stimuli.
Image persistence can produce systematic errors, which remain significant in some applications even when buried in
noise. Ideally the image persistence amplitude, linearity and decay over time could be calibrated independently for each
pixel to levels well below the noise floor, however averaging multiple measurements to characterize persistence to this
accuracy is impractical due to the long time scales for the decay and the need to emulate the exposure and readout timing
of the observations to be calibrated. We examine a compromise where the initial persistence response is characterized
independently for each pixel but the latter parts of the decay are assumed to follow the mean decay curve. When
averaged spatially, persistence increases monotonically with stimulus amplitude until the photodiodes approach forward
bias. For several Teledyne 1.7 μm cutoff HgCdTe detectors tested, persistence is linear over most of the normal signal
range. We characterize the temporal response, and examine the dependence of charge emission time constants on total
stimulus duration. We describe the suppression of persistence by signal in the current frame and begin to examine the
superposition of the decay curves from multiple stimuli.
High detector quantum efficiency (QE) can greatly improve speed and performance of wide field instruments
that strive for fast precision photometry. SNAP, a proposed satellite mission dedicated to exploring the nature
of the dark energy will employ a very large focal plane instrumented with about equal number of CCD and
NIR sensors totaling more than 600 million pixels covering roughly 0.7 square degrees on the sky. To precisely
characterize the NIR detector QE, the SNAP project has put in place a test set-up capable of measuring absolute
QE at the 5% level with the goal of ultimately reaching a precision better than 2%. Illumination of the NIR
detectors is provided by either a quartz tungsten halogen lamp combined with a set of narrow band filters or
a manually tunable monochromator. The two light sources feed an integrating sphere at a distance of roughly
60 cm from the detector to be tested and a calibrated InGaAs photodiode, mounted adjacent to the NIR
detector provides absolute photon flux measurements. This paper describes instrumentation, performance and
measurement procedures and summarizes results of detailed characterization of the QE on several SNAP devices
as a function of wavelength.
We present the development of a Focal Plane Module (FPM) for the Mid-Infrared Instrument on JWST. MIRI will
include three FPMs, two for the spectrometer channels and one for the imager channel. The FPMs are designed to
support the detectors at an operating temperature of 6.7 K with high temperature stability and precision alignment while
being capable of surviving the launch environment. The flight units will be built and will undergo a rigorous test
program in the first half of 2008. This paper includes a description of the full test program and will present the results.
The Mid-Infrared Instrument (MIRI) is a 5 to 28 micron imager and spectrometer that is slated to fly aboard the JWST in
2013. Each of the flight arrays is a 1024×1024 pixel Si:As impurity band conductor detector array, developed by Raytheon
Vision Systems. JPL, in conjunction with the MIRI science team, has selected the three flight arrays along with their spares.
We briefly summarize the development of these devices, then describe the measured performance of the flight arrays along
with supplemental data from sister flight-like parts.
Recently ESO has commissioned the HAWK-I camera which is equipped with a 2×2 mosaic of λc~ 2.5 µm HAWAII-2RG arrays. The arrays have high quantum efficiency and achieve photon shot noise limited performance on the telescope. Using reference pixels it can be shown that the readout noise for most arrays is limited by the MBE grown
HgCdTe material and not by the multiplexer or the data acquisition chain. Results obtained with the guide window of the
HAWAII-2RG multiplexer will be presented. Inter-channel crosstalk and fringing in the detector substrate will be
discussed. The dynamic range of detectors can be expanded by applying threshold limited integration (TLI) to the
follow-up-the-ramp nondestructive sampling scheme. For substrate removed arrays a calibration technique based on the
X-ray emission of Fe55 will be discussed.
Proc. SPIE 7021, Evaluation of the Teledyne SIDECAR ASIC at cryogenic temperature using a visible hybrid H2RG focal plane array in 32 channel readout mode, 70210Q (22 July 2008); doi: 10.1117/12.788717
Teledyne Imaging Sensors (TIS) has developed a new 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. At the last SPIE conference we presented test and performance
results of a Teledyne 2K×2K silicon PIN diode array hybridized to a Hawaii-2RG multiplexer, the Hybrid Visible
Silicon Imager (HyViSI). This detector was read out with the ESO standard IR detector controller IRACE, which
delivers detector limited performance. We have now tested the H2RG HyViSI detector with the new 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. We find
that the SIDECAR ASIC provides performance equal to optimized external electronics.
We report first results of laboratory tests of Si:As
blocked-impurity-band (BIB) mid-infrared (4 to 28 μm) detectors developed
by IMEC. These prototypes feature 88 pixels hybridized on an integrated cryogenic readout electronics (CRE). They
were developed as part of a technology demonstration program for the future Darwin mission. In order to be able to separate
detector and readout effects, a custom build TIA circuitry was used to characterize additional single pixel detectors.
We used a newly designed test setup at the MPIA to determine the relative spectral response, the quantum efficiency, and
the dark current. All these properties were measured as a function of operating temperature and detector bias. In addition
the effects of ionizing radiation on the detector were studied. For determining the relative spectral response we used a dualgrating
monochromator and a bolometer with known response that was operated in parallel to the Si:As detectors. The
quantum efficiency was measured by using a custom-build high-precision vacuum black body together with cold (T ~ 4K)
filters of known (measured) transmission.
The Low Background Infrared (LBIR) facility at the National Institute of Standards and Technology (NIST) is
responsible for absolute IR radiometric calibrations (SI traceable) in low-background temperature (below 80 K)
environments. IR radiometric test hardware that needs to be operated in cryogenic environments is calibrated in
cryogenic vacuum chambers maintained by the facility to create environments that simulate the low-temperature
background of space. Transfer radiometers have also been developed to calibrate IR radiometric test hardware this is too
large to ship to NIST from their own IR test facilities. The first generation transfer radiometer, the BXR, is a filter-based
radiometer that uses an As-doped Si Blocked Impurity Band detector, and can calibrate IR test chambers to a total
uncertainty of less than 3 % (1 σ ) at powers as low as to 10-14 W/cm2. The BXR has evaluated 9 chambers and the
performance of a subset of these chambers will be discussed to a limited extent to demonstrate the need for calibrating
IR test chambers. The second generation transfer radiometer, the MDXR, and new primary standards allowing absolute
calibrations as low as 10-15 W/cm2 are in the final stages of development. The MDXR will have all the functionality of
the BXR and it will have a cryogenic Fourier transform spectrometer (FTS) for high resolution spectral capability.
Performance specifications and test results from development activity on the new primary standards will be discussed.
Our group has developed the first 1024×1024 high background Si:As detector array, the Megapixel Mid-Infrared array
(MegaMIR). MegaMIR is designed to meet the thermal imaging and spectroscopic needs of the ground-based and airborne
astronomical communities. MegaMIR was designed with switchable capacitance and windowing capability to
allow maximum flexibility. We report initial test results for the new array.
Over the past decade scientists have collected convincing evidence that the content of our universe is dominated
by a mysterious dark energy. Understanding the nature of dark energy is a very difficult task, and requires a
variety of independent experimental approaches. Most of these approaches rely on photometric calibrations over
a wide range of intensities using standardized stars and internal reference sources, and hence on a complete
understanding of the linearity of the detectors. The SNAP near infrared (NIR) instrument team has performed
a comprehensive study of precision photometry on 1.7 micron cut-off HgCdTe detectors. Among those studies
are the count rate dependent detector non-linearity that was recently discovered with the NICMOS array on
the Hubble Space Telescope, and possible pixel size variations seen in quantum efficiency (QE) data. The nonlinearity
on NICMOS exhibits an unexpected behavior, where pixels with high (low) count rates detect slightly
more (less) flux than expected for a linear system. To test this count rate dependent non-linearity a dedicated
setup was built that produces a known amount of light on a detector, and measures its response as a function of
light intensity and wavelength. If the pixel response variations seen in QE data are due to pixel area variations,
standard flat-fielding will degrade photometry precision for point sources in an undersampled telescope. Studies
have been performed to estimate the magnitude of pixel area variations.
The CALICO sensor is a pathfinder for the development of the future infrared high speed low noise detectors for AO.
Low readout noise at high readout speed is accomplished by high gain and signal processing circuitry under each pixel.
The high gain makes the detector very susceptible to instability if the system noise is too high. Lnpix3, the most
promising structure, has a pixel gain of 400. In this paper we will report on test results and different measures we had to
take getting the detector to work.
The Wide-field Infrared Survey Explorer is a NASA Midex mission launching in late 2009 that will survey the entire
sky at 3.3, 4.7, 12, and 23 microns (PI: Ned Wright, UCLA). Its primary scientific goals are to find the nearest stars
(actually most likely to be brown dwarfs) and the most luminous galaxies in the universe. WISE uses three dichroic
beamsplitters to take simultaneous images in all four bands using four 1024×1024 detector arrays. The 3.3 and 4.7
micron channels use HgCdTe arrays, and the 12 and 23 micron bands employ Si:As arrays. In order to make a
1024×1024 Si:As array, a new multiplexer had to be designed and produced. The HgCdTe arrays were developed by
Teledyne Imaging Systems, and the Si:As array were made by DRS.
All four flight arrays have been delivered to the WISE payload contractor, Space Dynamics Laboratory. We present
initial ground-based characterization results for the WISE arrays, including measurements of read noise, dark current,
flat field and latent image performance, etc. These characterization data will be useful in producing the final WISE data
product, an all-sky image atlas and source catalog.
Two new DEPFET concepts are presented motivated by potential applications in adaptive optics and
in synchrotron radiation experiments at the future Free Electron
X-ray Laser (XFEL) in Hamburg.
The gatable DEPFET structure allows the selection of signal charges arriving in a predefined time
interval. Charges produced outside this gate interval are lead to a sink electrode while charge
collected already is protected and kept for later delayed readout.
In synchrotron radiation experiments one faces the challenge of being sensitive enough for single X-ray
photons in some parts of the detector while on other regions a very large charge due to the
superposition of many X-rays has to be measured. A DEPFET with strongly non-linear
characteristics combines naturally excellent energy resolution with high dynamic range, large charge
handling capability and high read out speed.
DEPFET Macropixel detectors, based on the fusion of the combined Detector-Amplifier structure DEPFET with
a silicon drift chamber (SDD) like drift ring structure, combine the excellent properties of the DEPFETs with
the advantages of the drift detectors. As both device concepts rely on the principle of sideways depletion, a
device entrance window with excellent properties is obtained at full depletion of the detector volume.
DEPFET based focal plane arrays have been proposed for the Focal Plane Detectors for the MIXS (Mercury
Imaging X-ray Spectrometer) instrument on BepiColombo, ESAs fifth cornerstone mission, with destination
Mercury. MIXS uses a lightweight Wolter Type 1 mirror system to focus fluorescent radiation from the Mercury
surface on the FPA detector, which yields the spatially resolved relative element abundance in Mercurys crust.
In combination with the reference information from the Solar Intensity X-ray Spectrometer (SIXS), the element
abundance can be measured quantitatively as well. The FPA needs to have an energy resolution better than
200 eV FWHM @ 1 keV and is required to cover an energy range from 0.5 keV to 10 keV, for a pixel size of
300 x 300 μm2. Main challenges for the instrument are the increase in leakage current due to a high level of
radiation damage, and the limited cooling resources due to the difficult thermal environment in the mercury
orbit. By applying an advanced cooling concept, using all available cooling power for the detector itself, and
very high speed readout, the energy resolution requirement can be kept during the entire mission lifetime up to
an end-of-life dose of ~ 3 × 1010 10 MeV p / cm2. The production of the first batch of flight devices has been
finished at the MPI semiconductor laboratory, and first prototype modules have been built. The results of the
first tests will be presented here.
Simbol-X is a French-Italian-German hard energy X-ray mission with a projected launch in 2014. Being sensitive in the
energy range from 500 eV to 80 keV it will cover the sensitivity gap beyond the energy interval of today's telescopes
XMM-Newton and Chandra. Simbol-X will use an imaging telescope of nested Wolter-I mirrors. To provide a focal
length of 20 m it will be the first mission of two independent mirror and detector spacecrafts in autonomous formation
flight.
The detector spacecraft's payload is composed of an imaging silicon low energy detector in front of a pixelated
cadmium-telluride hard energy detector. Both have a sensitive area of 8 × 8 cm2 to cover a 12 arcmin field of view and a pixel size of 625 × 625 μm2 adapted to the telescope's resolution of 20 arcsec. The additional LED specifications are:
high energy resolution, high quantum efficiency, fast readout and optional window mode, monolithic device with 100 %
fill factor and suspension mounting, and operation at warm temperature.
To match these requirements the low energy detector is composed of 'active macro pixels', combining the large, scalable
area of a Silicon Drift Detector and the low-noise, on-demand readout of an integrated DEPFET amplifier. Flight
representative prototypes have been processed at the MPI semiconductor laboratory, and the prototype's measured
performance demonstrates the technology readiness.
Proc. SPIE 7021, Hard x-ray and gamma-ray imaging and spectroscopy using scintillators coupled to silicon drift detectors, 702111 (22 July 2008); doi: 10.1117/12.788803
Silicon Drift Detectors (SDDs) are used as low-capacitance photon detectors for the optical light emitted by scintillators.
The scintillator crystal is directly coupled to the SDD entrance window. The entrance window's transmittance can be
optimized for the scintillator characteristic by deposition of a wavelength-selective anti-reflective coating. Compared to
conventional photomultiplier tubes the SDD readout offers improved energy resolution and avoids the practical
problems of incompatibility with magnetic fields, instrument volume and requirement of high voltage.
A compact imaging spectrometer for hard X-rays and γ-rays has been developed by coupling a large area (29 × 26 mm2)
monolithic SDD array with 77 hexagonal cells to a single
non-structured CsI-scintillator of equal size. The scintillation
light generated by the absorption of an energetic photon is seen by a number of detector cells and the position of the
photon interaction is reconstructed by the centroid method. The measured spatial resolution of the system (≤ 500 μm) is
considerably smaller than the SDD cell size (3.2 mm) and in the order required at the focal plane of high energy
missions. The energy information is obtained by summing the detector cell signals.
Compared to direct converting pixelated detectors, e.g. CdTe with equal position resolution the scintillator-SDD
combination requires a considerably lower number of readout channels. In addition it has the advantages of
comprehensive material experience, existing technologies, proven long term stability, and practically unlimited
availability of high quality material.
We have developed application specific integrated
circuits(ASICs) for multi-readout X-ray CCDs in order to improve their
time resolution. ASICs with the size of 3mm × 3mm were fabricated by employing a Taiwan
Semiconductor Manufacturing Company(TSMC) 0.35 μm CMOS technology.
The number of channels is 4 and the each channel consists of a
preamplifier, 5-bit DAC and delta-sigma analog-to-digital converters
(ADCs). The measured equivalent input noise at the
pixel rate of 19.5 kHz and 625 kHz are 36 μV and 51 μV,
respectively. The power consumption is about 110 mW/chip at 625 kHz pixel rate,
which is about 10 times lower than that of our existing system.
We now expect to employ an ASIC as the readout system of X-ray CCD camera onboard the next Japanese X-ray astronomy satellite. We tested the
readout of the prototype X-ray CCDs by using ASICs and the total-dose effects of ASICs. We describe the overview of our ASICs and test results.
In the frame of the hard X-ray Simbol-X observatory, a joint CNES-ASI space mission to be flown in 2014, a prototype
of miniature Cd(Zn)Te camera equipped with 64 pixels has been designed. The device, called Caliste 64, is a spectro-imager
with high resolution event time-tagging capability. Caliste 64 integrates a Cd(Zn)Te semiconductor detector with
segmented electrode and its front-end electronics made of 64 independent analog readout channels. This 1 × 1 × 2 cm3
camera, able to detect photons in the range from 2 keV up to 250 keV, is an elementary detection unit juxtaposable on its
four sides. Consequently, large detector array can be made assembling a mosaic of Caliste 64 units. Electronics readout
module is achieved by stacking four IDeF-X V1.1 ASICs, perpendicular to the detection plane. We achieved good noise
performances, with a mean Equivalent Noise Charge of ~65 electrons rms over the 64 channels. Time resolution is better
than 70 ns rms for energy deposits greater than 50 keV, taking into account electronic noise and technological dispersal,
which enables to reject background by anticoincidence with very low probability of error. For the first prototypes, we
chose CdTe detectors equipped with Al-Ti-Au Schottky barrier contacts because of their very low dark current and
excellent spectroscopic performances. So far, three Caliste 64 cameras have been realized and tested. When the crystal is
cooled down to -10°C, the sum spectrum built with the 64 pixels of a Caliste 64 sample results in a spectral resolution of
664 eV FWHM at 13.94 keV and 841 eV FWHM at 59.54 keV.
We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module
Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby
cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 20 TeV and
gamma rays in 20 MeV - several 10 TeV. CALET has a unique capability to observe electrons and gamma rays over 1
TeV since the hadron rejection power can be larger than 105 and the energy resolution better than a few % over 100 GeV.
The detector consists of an imaging calorimeter with scintillating fibers and tungsten plates and a total absorption
calorimeter with BGO scintillators. CALET has also a capability to measure cosmic ray H, He and heavy ionsi up to
1000 TeV. It also will have a function to monitor solar activity and gamma ray transients. The phase A study has
started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 year observation.
We present the first results from the successful fabrication of an optical imaging tube consisting of a pair of MCPs read
out by a CMOS application specific integrated circuit (ASIC) developed for x-ray imaging called the Medipix2. The
Medipix2 is an array of 256×256 pixels, each of which amplifies and counts individual photon stimulated events
amplified by the MCPs. A multi-alkali photocathode installed in proximity focus above the MCP is used for conversion
of incoming photons into photoelectrons.. The Medipix2 integrates these detected photons, and the binary values of these
counters is read fast (~ 1kHz frame rate) and without readout noise. Initial imaging tests of this tube, including QE,
resolution, background, dynamic range and microsecond shutter operation are presented..
The instruments on board the latest gamma observatories (INTEGRAL, SWIFT, AGILE, GLAST) combines
technologies based on solid state and on scintillator detector, the first one being favorite when a low energy threshold
and a good energy resolution is required, the latter being more convenient for large volume when worse performance are
still acceptable. With the developments achieved both with the new scintillator material and even more with new low-noise
light readout devices the differences between the two techniques are narrowing and for some application the
cheaper scintillator detector can compete with solid state devices. Starting from the techniques used in INTEGRAL-IBIS
and AGILE a new generation position sensitive X and gamma ray detector based on scintillator with Silicon Drift
Chamber readout has been developed and tested. The ASIC read-out electronics make it suitable for replication in a large
scale when a great number of pixel is needed. The performance of the detector as well as its applications in new
generation space telescopes are presented and discussed.
In this paper we discuss the design and performance of a new family of swept charge devices intended for X-ray
spectroscopy. The devices were designed to combine large area with good detection efficiency over the 0.5-10 keV band,
and, importantly, to be capable of operation at "warm" temperatures, e.g. room temperature. Three types of device have
been manufactured ranging in detection area from
5-420 mm2 and the paper discusses the initial characterisation of the
detectors over a range of temperatures. Whilst the device leakage current scales with detector area, we demonstrate that
the smallest detector is capable of yielding Fano-limited X-ray spectra at room temperature, whereas the largest requires
modest cooling down to -20°C to achieve this resolution.
After launch, the Advanced CCD Imaging Spectrometer (ACIS), a focal plane instrument on the Chandra Xray
Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's
radiation belts. An effect of the damage was to increase the charge transfer inefficiency (CTI) of the front
illuminated CCDs. As part of the initial damage assessment, the focal plane was warmed from the operating
temperature of -100° C to +30° C which unexpectedly further increased the CTI. We report results of ACIS
CCD irradiation experiments in the lab aimed at better understanding this reverse annealing process. Six CCDs
were irradiated cold by protons ranging in energy from 100 keV to 400 keV, and then subjected to simulated
bakeouts in one of three annealing cycles. We present results of these lab experiments, compare them to our
previous experiences on the ground and in flight, and derive limits on the annealing time constants.
Proc. SPIE 7021, Radiation study of swept-charge devices for the Chandrayaan-1 X-ray Spectrometer (C1XS) instrument, 70211A (22 July 2008); doi: 10.1117/12.791732
The Chandrayaan-1 X-ray Spectrometer (C1XS) will be launched as part of the Indian Space Research Organisation
(ISRO) Chandrayaan-1 payload in September 2008, arriving at the Moon within 7 days to begin a two year mission in
lunar orbit conducting mineralogical surface mapping over the range of 1 - 10 keV. The detector plane of the instrument
consists of twenty four e2v technologies CCD54 swept-charge devices (SCDs). Such devices were first flown in the
Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS) instrument onboard SMART-1 [4, 5]. The detector
plane in each case provides a total X-ray collection area of 26.4 cm2. The SCD is capable of providing near Fano-limited
spectroscopy at -10°C, and at -20°C, near the Chandrayaan-1 mission average temperature, it achieves a total system
noise of 6.2 electrons r.m.s. and a FWHM of 134 eV at Mn-Kα. This paper presents a brief overview of the C1XS
mission and a detailed study of the effects of proton irradiation on SCD operational performance.
Recent progress in Gallium Nitride (GaN, AlGaN, InGaN) photocathodes show great promise for future detector applications
in Astrophysical instruments. Efforts with opaque GaN photocathodes have yielded quantum efficiencies up to
70% at 120 nm and cutoffs at ~380 nm, with low out of band response, and high stability. Previous work with semitransparent
GaN photocathodes produced relatively low quantum efficiencies in transmission mode (4%). We now have
preliminary data showing that quantum efficiency improvements of a factor of 5 can be achieved. We have also performed
two dimensional photon counting imaging with 25mm diameter semitransparent GaN photocathodes in close
proximity to a microchannel plate stack and a cross delay line readout. The imaging performance achieves spatial resolution
of ~50μm with low intrinsic background (below 1 event
sec-1 cm-2) and reasonable image uniformity. GaN photocathodes with significant quantum efficiency have been fabricated on ceramic MCP substrates. In addition GaN
has been deposited at low temperature onto quartz substrates, also achieving substantial quantum efficiency.
Silicon Drift Detectors (SDD) can work both as direct X-ray detectors, exhibiting excellent spectroscopic capabilities in
the 1-30 keV energy range, and as photodetectors for scintillators readout. Both these detector concepts can be combined
in a single compact device by means of the Pulse Shape Discrimination (PSD) technique. A complete detection system
based on a monolithic 20-channels SDD array coupled to CsI(Tl) scintillating pixels operated with PSD technique has
been realized. The instrument description and performance will be presented and discussed, as well as its possible
applications as a detection plane for a wide field monitor for forthcoming gamma-ray burst search missions.
We demonstrated successful operation of an NbN single photon detector in the temperature range from 6 K to 1.2 K
using a 3He sorption refrigerator combined with a pulse-tube mechanical cooler. The detector was read out either by
microwave amplifiers or by a broadband SQUID-amplifier that limited the maximum counting rate to 107 counts per
second. This counting rate was only one third of the maximum rate provided by the detector. Besides an increase in the
quantum efficiency in the visible and near-infrared spectral range with the decrease of the operation temperature, we
found a more than twofold improvement in the energy resolution as compared to earlier demonstrated 1 eV at 6.5 K. The
noise equivalent power estimated at 4.2 K for visible light was better than 10-18 W Hz-1/2. We verified that the lowest
achieved dark count rate was still caused by the harsh electrical conditions in the mechanical cooler.
We have developed a Compton camera with a double-sided silicon strip detector (DSSD) for hard X-ray and
gamma-ray observation. Using a DSSD as a scatter detector of the Compton camera, we achieved high angular
resolution of 3.4° at 511 keV. Through the imaging of various samples such as two-dimentional array sources and
a diffuse source, the wide field-of-view (~ 100°) and the high spatial resolution (at least 20 mm at a distance of
60 mm from the DSSD) of the camera were confirmed. Furthermore, using the List-Mode Maximum-Likelihood
Expectation-Maximization method, the camera can resolve an interval of 3 mm at a distance of 30 mm from the
DSSD.
The evidence of excess noise in the power spectrum of many natural systems that span over the mHz to the THz, such as
biological system, superconductors at dendritic regime, Barkhausen noise of magnetic system and plasma emission from
nanometric transistors, was observed and related to a class of statistical models of correlated processes. Intrinsic or
induced fluctuations of the elementary processes taking place in transport phenomena couple each other giving rise to
time-amplitude correlated avalanches. TES sensors for X-ray microcalorimeters have shown a clear evidence that this
excess noise has typical spectral behavior spanning from 100 Hz to 10 kHz. We present an analysis of the excess noise
using this statistical avalanche model of TES operating on Si substrate and suspended SiN membrane.
X-ray microcalorimeters using magnetic sensors show great promise for use in astronomical x-ray spectroscopy.
We have begun to develop technology for fabricating arrays of magnetic calorimeters for X-ray astronomy. The
magnetization change in each pixel of the paramagnetic sensor material due to the heat input of an absorbed
x-ray is sensed by a meander shaped coil. With this geometry it is possible to obtain excellent energy sensitivity,
low magnetic cross-talk and large format arrays fabricated on wafers that are separate from the SQUID read-out.
We report on the results from our prototype arrays, which are coupled to low noise 2-stage SQUIDs developed
at the PTB Berlin. The first testing results are presented and the sensitivity compared with calculations.
Superconducting absorbers for thermal X-ray microcalorimeters should convert into thermalized phonons and
transfer to the thermal sensor most of the energy deposited by single photons, on a time scale as short as a
few tens of microseconds. Since deposition of X-ray energy in a superconductor produces quasiparticles by
breaking up of Cooper pairs, the thermalization efficiency depends on the time scale on which they survive
within the absorber volume, trapping part of the absorbed energy. According to the predicted values of their
microscopic parameters, in many standard type-I superconducting metals the quasiparticle life time at very
low temperatures results too long to allow for recombination on the relatively short time scale of the thermal
sensors. In type-II superconductors the existence of a mixed state with Abrikosov vortices could speed up
the recombination process and increase the efficiency of thermalization. We discuss this topic by presenting
experimental results of laboratory tests conducted on tantalum and lead-bismuth absorbers in a comparison
with an absorber made of gold, where no trapping is expected.
e2v technologies have recently been developing large area (2k*4k), high resistivity (>8 kΩcm) silicon CCDs intended
for infrared astronomy. The use of high resistivity silicon allows for a greater device thickness, allowing deeper, or full,
depletion across the CCD that significantly improves the red wavelength sensitivity. The increased depletion in these
CCDs also improves the quantum efficiency for incident X-ray photons of energies above 5 keV, whilst maintaining
spectral resolution. The use of high resistivity silicon would therefore be advantageous for use in future X-ray
astronomy missions and other applications.
This paper presents the measured X-ray performance of the high resistivity CCD247 for X-ray photons of energies
between 5.4 keV to 17.4 keV. Here we describe the laboratory experiment and results obtained to determine the
responsivity, noise, effective depletion depth and quantum efficiency of the CCD247.
This paper describes the design of CCD camera that is part of the EUV detector to be used in Space Solar Telescope. It will run at the solar synchronous circular orbit with 735 km height. In this paper, a CCD camera is designed composed of the CCD sensor module, the analog system and the embedded controller with an NIOSII soft-core processor based on FPGA. The analog system is first introduced in detail including power and bias voltage supply circuit, 16 bit A/D converter, power protecting circuit, amplifier circuit, and CCD driving clocks generation circuit. NIOS II embedded system is then presented including system hardware and NIOS II processor. Finally, evaluation results of this camera are also presented including readout noise, gain, linearity, dynamic range and full well capacity.
The Gaia satellite is a high-precision astrometry, photometry and spectroscopic ESA cornerstone mission, currently
scheduled for launch in late 2011. Its primary science drivers are the composition, formation and evolution of the
Galaxy. Gaia will not achieve its scientific requirements without detailed calibration and correction for radiation
damage. Microscopic models of Gaia's CCDs are being developed to simulate the effect of radiation damage, charge
trapping, which causes charge transfer inefficiency. The key to calculating the probability of a photoelectron being
captured by a trap is the 3D electron density within each CCD pixel. However, this has not been physically modelled
for Gaia CCD pixels. In this paper, the first of a series, we motivate the need for such specialised 3D device modelling
and outline how its future results will fit into Gaia's overall radiation calibration strategy.
The Wide-field Camera 3 (WFC3) is a fourth-generation instrument planned for installation in Hubble Space Telescope
(HST). Designed as a panchromatic camera, WFC3's UVIS and IR channels will complement the other instruments onboard
HST and enhance the observatory's scientific performance. UVIS images are obtained via two 4096×2051 pixel
e2v CCDs while the IR images are taken with a 1024×1024 pixel HgCdTe focal plane array from Teledyne Imaging
Sensors. Based upon characterization tests performed at NASA/GSFC, the final flight detectors have been chosen and
installed in the instrument. This paper summarizes the performance characteristics of the WFC3 flight detectors based
upon component and instrument-level testing in ambient and thermal vacuum environments.
National Astronomical Observatories of Chinese Academy of Sciences have successfully developed a universal
astronomical CCD controller, which is called Astronomical Array Control & Acquisition System (AACAS). It behaves
excellent performance and ultra low system noise. In this paper, results of E2V 4K×4K CCD203_82 characterization
using AACAS controller are presented and also the comparison with the specifications E2V supplied is given. It
concludes some important merits, such as dark current, readout noise, CTE and etc. The readout noise is smaller than 3e-
(50KHz) at -100°C working temperature. The system linearity is better than 99.99% and the full well is about 110027e-.
The horizontal and vertical CTE are 0.999993 and 0.999997, measured by Fe55 X-ray source and extended pixel edge
response (EPER) separately.
In order to improve the quantum efficiency (QE) at longer wavelength, we have developed fully-depleted backilluminated
CCDs in collaboration with Hamamatsu Photonics K.K (HPK). Recently, HPK delivered 10 CCDs for Subaru Prime Focus Camera (Suprime-Cam). These CCDs are made on N-type, high resistivity silicon
wafers. Each CCD has a 200 μm thick depletion layer. The CCD format is four-side buttable, 2k × 4k, 15
μm square pixels with 4 low noise output amplifiers. The characteristics of the CCDs have been tested in the
laboratory before they are installed into Suprime-Cam dewar. These CCDs have excellent performance; readout
noise < 5 e-, dark current < 2 e-/hour/pixel, parallel and serial charge transfer efficiency (CTE) > 0.999995,
and full-well ~ 180,000 e-. The QE of λ = 1 μm was 40 % at -100°C. All CCDs have good cosmetics. Surface
flatness is ~ 25 μm peak to value (P-V). The specification was acceptable. We are also developing CCDs for Hype Suprime-Cam (HSC), the next generation instrument for Subaru Telescope. HPK optimized back side process and has developed blue enhanced CCDs for HSC.