The LSST project has embarked on an aggressive new program to develop the next generation of silicon imagers for the visible and near-IR spectral regions. In order to better understand and solve some of the technology issues prior to development and mass-production for the huge LSST focal plane, a number of contracts have been written to imager firms to explore specific areas of technology uncertainty. We expect that these study contracts will do much toward reducing risk and uncertainty going into the next phase of development, the prototype production of the final large LSST imager.

Large area focal planes for the next generation of astronomical instruments require very flat imaging surfaces (< 10 μm peak-valley) over significant sizes (20 - 100 cm), accurate alignment of detector height, stable operation at low temperature, and fully-buttable packaging with large I/O requirements to connect multiple amplifiers per detector. These requirements are often mutually exclusive and therefore difficult to obtain in a single focal plane. In this paper we discuss the hybridization or flip chip bonding technique and associated focal plane mounting methods to achieve these goals. Specifically, we describe a technique to hybridize CCD detectors onto high thermal conductivity ceramic with vias that lead to the I/O signals underneath the detectors. Packaging methods to mount such devices with a total flatness non-uniformity of less than 10 microns are presented. The requirements of achieving sub-5 microns flatness are also discussed.

Following successful manufacture of small-format trial devices we have now designed and manufactured large-format scientific CCDs in high resistivity silicon ('high-rho'). These devices are intended for 'full depletion' operation as backside illuminated sensors for very high red wavelength sensitivity and X-ray imaging spectroscopy at extended energies. Devices of 2k*512 and 2k*4k format, with both single and dual stage output circuits have been manufactured and tested. Design considerations, test results, and commercial manufacturing considerations will be addressed.

In this paper, we present an overview of large area detector arrays and new sensor technologies currently under development at Fairchild Imaging. We discuss on-going development efforts aimed at satisfying the increasing need for large format, scientific grade detectors, and review significant progress in achieving higher spatial resolution in large area back-illuminated CCDs. We also present the performance characteristics of a new prototype CCD/CMOS hybrid sensor designed for low light level imaging and capable of high speed, low power, and very low noise.

We report on the early progress of the Active Pixel Sensor (SWIR, Optical and UV/EUV) industrial developments for the European Space Agency Bepi Colombo and Solar Orbiter missions and present preliminary results of tests performed in our laboratory on an existing optical rad-hard APS, the STAR1000, presently in prequalification phase.

For the past 25 years Charge Coupled Devices (CCDs) have been used as the preferred detector for ground based astronomy to detect visible photons. As an alternative to CCDs, silicon-based hybrid CMOS focal plane array technology is evolving rapidly. Visible hybrid detectors have a close synergy with IR detectors and are operated in a similar way. This paper presents recent test results for a Rockwell 2K x 2K silicon PIN diode array hybridized to a Hawaii-2RG multiplexer, the Hybrid Visible Silicon Imager (HyViSI). Since the capacitance of the integrating node of Si-PIN diodes is at least a factor of two smaller than the capacitance of the Hawaii-2RG IR detector pixel, lower noise was expected. However, those detectors suffer from interpixel capacitance which introduces an error to the value of the conversion factor measured with the photon transfer method. Therefore QE values have been overestimated by almost a factor of two in the past. Detailed test results on QE, noise, dark current, and other basic performance values as well as a discussion how to interpret the measured values will be presented. Two alternative methods, direct measurement of the nodal capacity and the use of Iron-55 X-rays to determine the actual nodal capacitance and hence the conversion factor will be briefly presented. PSF performance of this detector was analyzed in detail with an optical spot and single pixel reset measurement.

The Dark Energy Survey Camera focal plane array will consist of 62 2k x 4k CCDs with a pixel size of 15 microns and a silicon thickness of 250 microns for use at wavelengths between 400 and 1000 nm. Bare CCD die will be received from the Lawrence Berkeley National Laboratory (LBNL). At the Fermi National Accelerator Laboratory, the bare die will be packaged into a custom back-side-illuminated module design. Cold probe data from LBNL will be used to select the CCDs to be packaged. The module design utilizes an aluminum nitride readout board and spacer and an Invar foot. A module flatness of 3 microns over small (1 sqcm) areas and less than 10 microns over neighboring areas on a CCD are required for uniform images over the focal plane. A confocal chromatic inspection system is being developed to precisely measure flatness over a grid up to 300 x 300 mm. This system will be utilized to inspect not only room-temperature modules, but also cold individual modules and partial arrays through flat dewar windows.

Photon transfer curve is one of the most valuable tools for calibrating, characterizing, and optimizing the performance of CCDs. Its primary purpose is to determine the conversion gain of the CCD system, from which many of the other performance parameters such as read noise, dark current, QE, full well etc. are determined. Recent measurements on CCDs from different manufacturers have revealed that the photon transfer curve is non-linear (in excess of 15%) with the variance progressively becoming less at high signal levels than that predicted by simple photon shot noise. The puzzling thing is that the signal linearity is excellent and unaffected. This paper reports on the investigation which has isolated the source of the non-linearity to the CCD image area. Additionally, spatial autocorrelation analysis shows that the mechanism behind the non-linearity is due to spreading or sharing of charge between pixels in the image area. The authors only have a description of the phenomenon and invite all to help with an explanation.

A 16K x 16K, 1 degree x 1 degree field, detector system was developed by ESO for the OmegaCAM instrument for use on the purpose built ESO VLT Survey Telescope (VST). The focal plane consists of an 8 x 4 mosaic of 2K x 4K 15um pixel e2v CCDs and four 2K x 4K CCDs on the periphery for the opto-mechanical control of the telescope. The VST is a single instrument telescope. This placed stringent reliability requirements on the OmegaCAM detector system such as 10 years lifetime and maximum downtime of 1.5 %. Mounting at Cassegrain focus required a highly autonomous self-contained cooling system that could deliver 65 W of cooling power. Interface space for the detector head was severely limited by the way the instrument encloses the CCD cryostat. The detector system features several novel ideas tailored to meet these requirements and described in this paper: Key design drivers of the detector head were the easily separable but precisely aligned connections to the optical field flattener on the top and the cooling system at the bottom. Material selection, surface treatment, specialized coatings and in-situ plasma cleaning were crucial to prevent contamination of the detectors. Inside the cryostat, cryogenic and electrical connections were disentangled to keep the configuration modular, integration friendly and the detectors in a safe condition during all mounting steps. A compact unit for logging up to 125 Pt100 temperature sensors and associated thermal control loops was developed (ESO's new housekeeping unit PULPO 2), together with several new modular Pt100 packaging and mounting concepts. The electrical grouping of CCDs based on process parameters and test results is explained. Three ESO standardized FIERA CCD controllers in different configurations are used. Their synchronization mechanism for read-out is discussed in connection with the CCD grouping scheme, the shutter, and the integrated guiding and image analysis facility with four independent 2K x 4K CCDs. An illustration of the data chain performance from CCD output to storage on hard-disk gives an impression of the challenge to shift 512 MB of data within 45 seconds via the standardized hierarchical ESO data acquisition network. Finally the safety and emergency features of the overall system are presented.

We describe charge-coupled device (CCD) development activities at the Lawrence Berkeley National Laboratory (LBNL). Back-illuminated CCDs fabricated on 200-300 μm thick, fully depleted, high-resistivity silicon substrates are produced in partnership with a commercial CCD foundry. The CCDs are fully depleted by the application of a substrate bias voltage. Spatial resolution considerations require operation of thick, fully depleted CCDs at high substrate bias voltages. We have developed CCDs that are compatible with substrate bias voltages of at least 200V. This improves spatial resolution for a given thickness, and allows for full depletion of thicker CCDs than previously considered. We have demonstrated full depletion of 650-675 μm thick CCDs, with potential applications in direct x-ray detection. In this work we discuss the issues related to high-voltage operation of fully depleted CCDs, as well as experimental results on high-voltage-compatible CCDs.

At MPI Halbleiterlabor, pnCCDs have been continuously developed to improve readout noise, readout speed, charge transfer efficiency and energy resolution. Pixel sizes of 75μm, 51μm and 36μm were realized in addition to the original 150μm pixel design. Reduction of the pixel size evidently changes the electric fields in the pixel structure. This leads to the question of how scaling of the pixel size affects the charge collection at subpixel dimensions. We used the "mesh-method" to measure the amount of signal charge deposited in a pixel depending on the position of X-Ray photon incidence within the pixel. In this experiment, a mesh with a rectangular hole pattern was mounted above the entrance window or structured front side of the detector. A slight rotation of the mesh ensures that every hole has a different position relative to the pixel below. It corresponds to scanning of a single pixel. Measurements were done with pnCCDs of 150μm, 75μm and 51μm pixel size at photon energies from 0.7keV to 5.4keV. We also used a setup with front side illumination of a pnCCD with 75μm pixel size to investigate the absorption of X-ray photons in the register structure of the device. Numerical simulations delivered results for signal charge distribution into pixels along the charge transfer direction. We analyzed the charge collection in a pixel and the absorption properties of the register structure with a spatial resolution below 5μm and could investigate the accuracy of numerical device simulations.

A high speed CCD camera has been completed at the National Astronomical Observatories of China (NAOC). A Kodak CCD was used in the camera. Two output ports are used to read out CCD data and total speed achieved 60M pixels per second. The Kodak KAI-4021 image sensor is a high-performance 2Kx2K-pixel interline transfer device. The 7.4μ square pixels with micro lenses provide high sensitivity and the large full well capacity results in high dynamic range. The inter-line transfer structure provides high quality image and enables electronic shuttering for precise exposure control. The electronic shutter provides a method of precisely controlling the image exposure time without any mechanical components. The camera is controlled by a NIOS II family of embedded processors, which is Altera's second-generation soft-core embedded processor for FPGAs. The powerful embedded processors make the camera with splendid features to satisfy continuously appearing new observational requirements. This camera is very flexible and is easy to implement new special functions. Since FPGA and other peripheral logic signals are triggered by a single master clock, the whole system is perfectly synchronized. By using this technique the camera cuts off the noise dramatically.

Since adaptive optics on large telescopes provides almost diffraction limited resolution, Nyquist sampling of moderate fields requires large format arrays. Because of limited substrate sizes there is a tendency to shrink the pixel size to extend the array format beyond 2Kx2K. However, with smaller pixel sizes the coupling capacitance between neighboring pixels becomes more important and its effect on performance and basic parameters of large format arrays has to be analyzed. Therefore, techniques to measure the effect of the coupling capacitance on the conversion gain will be presented. The capacitance comparison method and the autocorrelation technique will be discussed and compared quantitatively. It will be shown that the "noise squared versus signal" method which is in common use to obtain the conversion gain, can only be applied for negligible interpixel capacitance. The X-ray decay of Fe55 is a well established calibrator for silicon and can be applied to Si-PIN diode arrays in order to verify the different methods. Finally, a new technique called single pixel reset will be presented, which directly measures the impulse response or point spread function generated by the inter-pixel capacitance. The measured PSF impulse response can be used for the deconvolution of images to compensate the degradation of spatial resolution induced by the interpixel capacitance. The difference of interpixel capacitance measured in infrared hybrid arrays and Si-PIN diode arrays hybridized to the same multiplexer will be discussed. Keywords:, interpixel capacitance, conversion gain, point spread function, single pixel reset, CMOS hybrid, Hawaii- 2RG, HgCdTe, Si-PIN, HyViSI.

A new use for a 2-dimensional position sensitive diode (PSD) is described. A duolateral PSD was used with a microchannel plate image intensifier as a proof-of-concept photon counting (event driven) imager for astronomical imaging and photometry. This produced an imager capable of counting 25-30 kcps over the astronomical bands B, V & R, with an overall efficiency of ~19%.

ESO and JRA2 OPTICON have funded e2v technologies to develop a compact packaged Peltier cooled 24 μm square 240x240 pixels split frame transfer 8-output back-illuminated L3Vision CCD3, L3Vision CCD for Adaptive Optic Wave Front Sensor (AO WFS) applications. 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, multi-output EMCCD gain registers and metal buttressing of row clock lines are used. The baseline device is built in standard silicon. In addition, a split wafer run has enabled two speculative variants to be 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. The designs of the CCD and Peltier package have passed their reviews and fabrication has begun. This paper will describe the progress to date, the requirements and the design of the CCD and compact Peltier package, technology trade-offs, schedule and proposed test plan. High readout speed, low noise and compactness (requirement to fit in confined spaces) provide special challenges to ESO's AO variant of its NGC, New General detector Controller to drive this CCD. This paper will describe progress made on the design of the controller to meet these special needs.

A system is described which makes best use of the high quantum efficiency and high count rate capability of avalanche photodiodes for high time resolution observations of optical pulsars. The use of three APDs allows simultaneous photometry of the target and a reference star, and the monitoring of the sky background. By minimising the optical components in the light path the optical efficiency of the system is maximised. The TRIFFID¹ and OPTIMA² have shown that fibre-fed APD arrays can produce excellent results. This, new, system was used on the 6m BTA in November 2003-results on the Crab pulsar are presented.

The Infrared Array Camera (IRAC) is a four-channel camera on the Spitzer Space Telescope, one of three focal plane science instruments. IRAC uses two pairs of 256×256 pixel InSb and Si:As IBC detectors to provide simultaneous imaging at 3.6, 4.5, 5.8, and 8 μm. IRAC experiences a flux of cosmic rays and solar protons that produce transient effects in science images from each of the arrays, with 4-6 pixels per second being affected during each integration. During extreme solar flares, IRAC experiences a much higher rate of transients which affects the science data quality. We present cosmic ray rates and observed detector characteristics for IRAC during the first two years of science operation, and rates observed in a period of elevated solar proton flux during an intense solar flare in January 2005. We show the changes to the IRAC detectors observed since launch, and assess their impacts to the science data quality.

This paper describes a qualification programme for Electron-Multiplication Charge Coupled Devices (EMCCDs) for use in space applications. While the presented results are generally applicable, the programme was carried out in the context of CCD development for the Radial Velocity Spectrometer (RVS) instrument on the European Space Agency's cornerstone Gaia mission. We discuss the issues of device radiation tolerance, charge transfer efficiency at low signal levels and life time effects on the electron-multiplication gain. The development of EMCCD technology to allow operation at longer wavelengths using high resistivity silicon, and the cryogenic characterisation of EMCCDs are also described.

Since 1974 we develop photon-counting imaging devices for high angular resolution in the visible by means of speckle and optical interferometry. Our last generation photon-counting camera, CPNG, has been built to benefit from the recent advances in photonic commercial components. CPNG is an ICCD which uses electron multiplication in microchannel plates to overcome the readout noise of fast CCD. We achieve optimal performances (sensitivity and resolution) by proper optical design, by cooling of the first stage photocathode and by careful data processing. Thanks to the power of current workstations, the processing of the CCD signal can be done by elaborated real-time software at frame rates as high as 262 Hz (72 Mpixel/s). The real-time software is in charge of detecting occurences of photon-events and estimating their positions. We explain how our dedicated processing improves the detection sensitivity to reach an effective quantum efficiency of 35%. We also show that our unbiased recentering of detected photons can avoid spurious high-energy events and nevertheless achieve sub-pixel resolution. In practice, our resolution is limited by the size of a microchannel to about 2000×2000 effective pixels for our 516×532 CCD. The very good performances of CPNG open us new classes of objects and have proven to be useful for other applications. For instance, several versions of our camera have been developped (with different spectral ranges) to cover the common needs in Astronomy and biological imaging for an extremely low-light level and fast imaging detector.

In depth characterization of CMOS arrays is unveiling many characteristics not observed in CCD imagers. This paper is the first of a series of papers that will discuss unique CMOS characteristics related to fundamental performance differences between CMOS and CCD imagers with emphasis on scientific arrays. The first topic will show that CMOS read noise is ultimately limited by a phenomenon referred to as random telegraph signal (RTS) noise. RTS theory and experimental data discuss its creation, time and frequency domain characteristics, wide variance from pixel to pixel and magnitude on the sensor's overall read noise floor. Specific operating parameters that control and lower RTS noise are identified. It is shown how correlated double sampling (CDS) signal processing responds to RTS noise and demonstrate that sub electron CMOS read noise performance is possible. The paper also discusses CMOS sensitivity (V/e-) nonlinearity, an effect not familiar to CCD users. The problem plays havoc on conventional photon transfer analysis that leads to serious measurement errors. New photon transfer relations are developed to deal with the problem. Nonlinearity for custom CMOS pixels is shown to be beneficial for lowering read noise and extending dynamic range. The paper closes with a section on the high performance CMOS array used to generated data products presented.

Large-area near-infrared focal-plane detector arrays constructed from one and four Rockwell Science Center HAWAII- 2RG HgCdTe detectors have been characterized for use in the NIFS and GSAOI instruments recently developed for the Gemini telescopes by the Australian National University. We present details of the detector characterization and compare the performance of five distinct devices with respect to read noise, dark current, and stability in systems based on ARC/SDSU Gen-3 controllers. Advanced operating modes of the H2RG were implemented including enhanced clocking and independent On-Detector Guide Windows for GSAOI. Detector performance using these features and the impact of multiple guide-window reads on long integrations are explored. We also discuss measurement of intra-pixel coupling and its impact on pixel-well capacity, gain, and image quality for these devices.

The next generation of Radial Velocity Spectrometers for 8 metre class telescopes will require very high resolution spectroscopy in the near infrared 1-2.5μm regime. One of the main engineering goals for such an instrument design is to readout at high speed, multiple windows, which are concurrently imaging bright reference arc lines whilst also integrating very faint source spectra on the rest of the detector. The Hawaii-1RG/2RG readout multiplexers offer a programmable window readout mode which allows non-destructive readout of multiple regions which are programmable in any size and location on the array. We present results from the characterisation of an engineering grade H1RG detector using an SDSU III controller and the effects of the multiple window readout, if any, on the noise and cross-talk performance of the rest of the detector. The detector performance results will also include quantum efficiency measurements in J, H and K pass bands, dark generation, noise, full well, linearity, inter-pixel capacitance and persistence.

Large format (1k × 1k and 2k × 2k) near infrared detectors manufactured by Rockwell Scientific Center and Raytheon Vision Systems are characterized as part of the near infrared R&D effort for SNAP (the Super-Nova/Acceleration Probe). These are hybridized HgCdTe focal plane arrays with a sharp high wavelength cut-off at 1.7 μm. This cut-off provides a sufficiently deep reach in redshift while it allows at the same time low dark current operation of the passively cooled detectors at 140 K. Here the baseline SNAP near infrared system is briefly described and the science driven requirements for the near infrared detectors are summarized. A few results obtained during the testing of engineering grade near infrared devices procured for the SNAP project are highlighted. In particular some recent measurements that target correlated noise between adjacent detector pixels due to capacitive coupling and the response uniformity within individual detector pixels are discussed.

We present the results of a detailed study of the noise performance of candidate NIR detectors for the proposed Super-Nova Acceleration Probe. Effects of Fowler sampling depth and frequency, temperature, exposure time, detector material, detector reverse-bias and multiplexer type are quantified. We discuss several tools for determining which sources of low frequency noise are primarily responsible for the sub-optimal noise improvement when multiple sampling, and the selection of optimum fowler sampling depth. The effectiveness of reference pixel subtraction to mitigate zero point drifts is demonstrated, and the circumstances under which reference pixel subtraction should or should not be applied are examined. Spatial and temporal noise measurements are compared, and a simple method for quantifying the effect of hot pixels and RTS noise on spatial noise is described.

We present the results of a study of the performance of InGaAs detectors conducted for the SuperNova Acceleration Probe (SNAP) dark energy mission concept. Low temperature data from a nominal 1.7um cut-off wavelength 1kx1k InGaAs photodiode array, hybridized to a Rockwell H1RG multiplexer suggest that InGaAs detector performance is comparable to those of existing 1.7um cut-off HgCdTe arrays. Advances in 1.7um HgCdTe dark current and noise initiated by the SNAP detector research and development program makes it the baseline detector technology for SNAP. However, the results presented herein suggest that existing InGaAs technology is a suitable alternative for other future astronomy applications.

We present the design, construction, and test observations of a new infrared (IR) photon-counting photometer for astronomy based on the edge-illuminated solid-state photomultiplier (EISSPM). The EISSPM has a photon-counting capability over the 0.4-28 μm range with a nanosecond-scale intrinsic detector time resolution. Its quantum efficiency (QE) peaks greater than or equal to 30 % in the near-IR, which is much higher than the previous SSPM with back illumination. After characterizing the dark noise of the EISSPM at its operational temperature range, we develop an EISSPM-based IR photon-counting photometer for astronomical observations. This includes the design and construction of a full optical, cryo-mechanical, and electronics system as well as the software for operating the instrument on telescopes. We report the results of our test observations of the Crab Nebula pulsar using this new instrument on the Palomar Hale 5-m telescope with 10-μs time resolution.

Current adaptive optic systems are limited by the read noise and sensitivity of their wavefront cameras. Recent advances in substrate thinning are producing focal plane arrays with high quantum efficiencies and extended spectral response over 0.5 to 1.6 microns. Infra Red Laboratories have developed and tested a new ultra-low noise readout integrated circuit (ROIC) that has a performance of 2 electrons (r.m.s.) per pixel read. We combine these two technologies to produce a new detector capable of dramatically increasing the number of available natural guide stars across the sky (and hence increased sky coverage), even in heavily obscured regions near the Galactic plane.

We present the design for a new detector configuration, specifically tailored to suit the needs of prospective Laue Lens Gamma-ray astronomy missions in the 10keV to 1MeV energy range. A Laue Lens uses transmission diffraction through crystal planes to focus the incoming gamma-rays. Diffraction is highly energy dependant and in order to recreate high resolution images, very accurate measurements of the total energy of the incident photon are necessary, as well as good spatial resolution. The aim is to absorb all the Compton scattered products of the incoming photons. The design uses a cavity geometry with the main germanium pixilated imaging detector embedded position sensitive cavity. The germanium is then enclosed in a veto to reduce background and to clean the imaging of unwanted non-photopeak events. This allows the majority of backscattered photons to be captured producing a detector with a photopeak efficiency of ~90% at 511keV and millimetric spatial resolution. The detector system has the added advantage that it functions extremely efficiently as a gamma-ray polarimeter.

We have developed a high speed, flexible, data acquisition system and targeted it to astronomical imaging. The system is based on Field Programmable Gate Arrays (FPGAs) and provides a gigabit/sec fiber optic link between the electronics located on the instrument and the host computer. The FPGAs are reconfigurable over the fiber optic link for maximum flexibility. The system has initially been targeted at DRS Technologies' 256x256 Si:As and Si:Sb detectors used in FORCAST¹, a mid-IR camera/spectrograph built by Cornell University for SOFIA. The initial configuration provides sixteen parallel channels of six Msamples/second 14-bit analog to digital converters. The system can coadd 256x256 images at over 1000 frames per second in up to 64 different memory positions. Array clocking and sampling is generated from uploaded clocking patterns in two independent memories. This configuration allows the user to quickly create, on the fly, any form of array clocking and sampling (destructive, non-destructive, sample up the ramp, additional reset frames, Fowler, single frames, co-added frames, multi-position chop, throw away frames, etc.) The electronics were designed in a modular fashion so that any number of analog channels from arrays or mosaics of arrays can be accommodated by using the appropriate number of FPGA boards and preamps. The preamp/analog to digital converter boards can be replaced as needed to operate any focal plane array or other sensor. The system also provides analog drive capability for controlling an X-Y chopping secondary mirror, nominal two position chopping, and can also synchronize to an externally driven chop source. Multiple array controllers can be synchronized together, allowing multi-channel systems to share a single chopping secondary, yet clock the focal planes differently from each other. Due to the flexibility of the FPGAs, it is possible to develop highly customized operating modes to maximize system performance or to enable novel observations and applications.

High performance large infrared detector arrays that meet the demanding requirements of the astronomy and civil space communities are available at Raytheon Vision Systems (RVS). This paper describes multiple detector materials in array formats larger than 1k × 1k developed by RVS for low-background applications. Raytheon features low noise readouts that have been demonstrated with a variety of detector materials: Si PIN, HgCdTe, InSb, and Si:As IBC. All of these detector materials have demonstrated excellent QE uniformity over wavelengths ranging from visible (optical) to 28 μm. RVS packaging capabilities address reliability, precision alignment and flatness requirements for both ground-based and space applications. Summary performance data of each of these materials on arrays with more than one million detector elements are presented. A look into the future will include "plug and play" mosaic packaging concepts; focal plane electronics; and increasing array formats to 4k × 4k and beyond.

We developed the new readout system for the pixel-readout μ-PIC (micro pixel chamber), which is one of the micro-pattern gas detectors that have been developed as a X-ray polarimeter so far. By using this system, we succeeded in achieving the sensitivity predicted by the simulation, i.e, the modulation factors, which is one of the most important factors for X-ray polarimeter as defined later in this paper, 0.24±0.08 at 8 keV, 0.18±0.07 at 15 keV in the neon-based gas mixture, and 0.18±0.04 in the argon-based gas although there still remain problems such as the pitch size among pixels and the non-uniformity of the response.

DEPMOSFET based Active Pixel Sensor (APS) matrices are a new detector concept for X-ray imaging spectroscopy missions. They can cope with the challenging requirements of the XEUS Wide Field Imager and combine excellent energy resolution, high speed readout and low power consumption with the attractive feature of random accessibility of pixels. From the evaluation of first prototypes, new concepts have been developed to overcome the minor drawbacks and problems encountered for the older devices. The new devices will have a pixel size of 75 μm × 75 μm. Besides 64 × 64 pixel arrays, prototypes with a sizes of 256 × 256 pixels and 128 × 512 pixels and an active area of about 3.6 cm² will be produced, a milestone on the way towards the fully grown XEUS WFI device. The production of these improved devices is currently on the way. At the same time, the development of the next generation of front-end electronics has been started, which will permit to operate the sensor devices with the readout speed required by XEUS. Here, a summary of the DEPFET capabilities, the concept of the sensors of the next generation and the new front-end electronics will be given. Additionally, prospects of new device developments using the DEPFET as a sensitive element are shown, e.g. so-called RNDR-pixels, which feature repetitive non-destructive readout to lower the readout noise below the 1 e^- ENC limit.

We have developed X-ray charge-coupled devices (CCD) for the next Japanese X-ray astronomical satellite mission, NeXT (Non-thermal energy eXploration Telescope). The hard X-ray telescope(HXT) onboard the NeXT can focus X-rays above 10 keV. Therefore, we need to develop an X-ray CCD for a focal plane detector to cover the 0.3-25 keV band in order to satisfy the capability of the telescope. We newly developed an n-type CCD fabricated on an n-type silicon wafer to expand the X-ray energy range as a focal plane detector of the HXT. It is possible to have a thick depletion layer of approx. 300μm with an n-type CCD because it is easy to obtain high resistivity with an n-type silicon wafer compared to a p-type silicon wafer. We developed prototypes of n-type CCDs and evaluated their X-ray performance, energy resolution, charge transfer inefficiency(CTI) and the thickness of the depletion layer of two devices, designated Pch15 and Pch-teg. We measured the thickness of the depletion layer of Pch15 to be 290±33μm. For Pch-teg, the energy resolution was 152±3eV full width at half maximum (FWHM) at 5.9 keV and the readout noise was 7.3 e^-. The performance of the n-type CCDs was comparable to that of p-type CCDs, and their depletion layer were much thicker than those of p-type CCDs.

The requirement on energy resolution for detectors in future X-ray satelite missions such as XEUS (X-ray Evolving Universe Spectroscopy mission) is <2eV in the soft x-ray range of 50-2000 eV, with a detection efficiency >80%. In addition, the requirements for field of view and angular resolution demand a detector array of typically 150x150 micron sized pixels in a 30x30 pixel format. DROIDs (Distributed Read Out Imaging Devices), consisting of a superconducting absorber strip with superconducting tunnel junctions (STJs) as read-out devices on either end, can fulfill these requirements. The amplitudes of the two signals from the STJs provide information on the absorption position and the energy of the incoming photon in the absorber. In this paper we present the development status of Ta/Al 1-D DROIDs, as well as the the short term development program that should result in a full size XEUS array.

The fabrication of GaAs diode arrays for X-ray imaging spectroscopy applications is described. Special attention is paid to the processing of wafers and devices to allow integration with different readout Application Specific Integrated Circuits (ASICs) using flip-chip bump bonding techniques.

We report on our studies of possible configurations for the focal plane of the Constellation-X mission. Taking advantage of new developments in both SQUID multiplexing technology and position-sensitive detectors, we present a viable focal plane intrument design that would greatly enhance the reference Constellation-X configuration of a 32 × 32 array. An order of magnitude increase in the number of pixels of the focal plane array from the current 1024-pixel reference design is achievable.

Until recently the spatial resolution of microchannel plate based photon/particle counting sensors has generally been limited by the accuracy of the readout technique. The accuracy of novel readouts, in particular cross strip anodes, have now reached the 6-10μm scale (the typical size of pores in a microchannel plate) and no longer determine the ultimate resolution limit of the detector. Although there are some issues (e.g. fixed pattern distortions seen on 5 μm scale) to be resolved for the cross strip (XS) anodes, one of the major drawbacks of the previous generation XS readouts is the low counting rate capability (10 KHz), determined by the processing electronics, in particular by the signal amplifier ASICs. In this paper we describe a new signal processing technique which should allow for high counting rates exceeding 1 MHz with the same high spatial resolution (<10 μm FWHM). The slow analog sample and hold signal processing is replaced by a fully parallel signal amplification followed by digital peak detection in each output channel. The charge values in each electrode are calculated from the digitized waveforms passed into a Field Programmable Gate Array (FPGA) where the signal peak detection and event centroiding is performed continuously. A detailed model was developed in order to optimize the digital peak detection algorithms and to determine the acceptable parameters for the electronic elements for a given spatial resolution. The results of our Monte Carlo modeling indicate that the spatial resolution of fast XS anode encoding electronics will still be better than 10 μm FWHM.

The Simbol-X mission, currently undergoing a joint CNES-ASI phase A, is essentially a classical X-ray telescope having an exceptional large focal length obtained by formation flying technics. One satellite houses the Wolter I optics to focus, for the first time in space, X-rays above ~10 keV, onto the focal plane in the second satellite. This leads to improved angular resolution and sensitivity which are two orders of magnitude better than those obtained so far with non-focusing techniques. Tailored to the 12 arcmin field of view and ~15 arcsec angular resolution of the optics, the ~8x8 cm² detection area of the spectro-imager has ~ 500x500 μm² pixels, and covers the full energy range of Simbol-X, from ~0.5 to ~80 keV, with a good energy resolution at both low and high energy. Its design leads to a very low residual background in order to reach the required sensitivity. The focal plane ensemble is made of two superposed spectro-imaging detectors: a DEPFET-SDD active pixel sensor on top of an array of pixelated Cd(Zn)Te crystals, surrounded by an appropriate combination of active and passive shielding. Besides the overall concept and structure of the focal plane including the anti-coincidence and shielding, this paper also emphasizes the promising results obtained with the active pixel sensors and the Cd(Zn)Te crystals combined with their custom IDeF-X ASICs.

An advanced pnCCD type has been developed, based on the concept of the XMM-Newton detector, which has been performing spectroscopy and imaging since 2000. This new detector is designed according to the requirements of eROSITA, a new X-ray astronomy mission, to be launched in 2010. The focal plane for each of the seven individual Wolter telescopes will be equipped with one of these new-type X-ray pnCCDs. In addition to the eROSITA chips, we have developed CCDs for other applications, e.g. for projects which require smaller pixel sizes. The devices that have been produced in the semiconductor laboratory (MPI Halbleiterlabor) of the Max-Planck-Institut fur extraterrestrische Physik are currently subject of systematic quality checks and spectroscopic tests. These tests are performed under standardized conditions on a representative subset of the many devices we have produced. The aim of these tests is to extract the key performance parameters of the individual CCDs like readout noise, energy resolution and the occurrence of bad pixels. The analysis includes the CAMEX analog signal processor, which has been developed for the readout of the CCD signals. After an introduction, we present the motivation for the detector development and give an overview about our CCD design and production, as well as about the CAMEX ASIC. Then device tests, test setups and data analysis are described. We report in detail about the performance of the tested devices. Failures that occurred during device tests are subsequently discussed. Finally, we give a review of the results.

In this paper we present the preliminary results from experiments with Distributed Read Out Imaging Devices (DROIDs) in the optical and in the X-ray regime. For the optical results DROIDs of different lengths ranging from 200 to 700 μm have been used with an STJ lay-up of Ta/Al/AlOx/Al/Ta with thicknesses of 100/30/1/30/100 nm. With this data the behavior with different absorber length has been investigated to determine an optimal absorber size for a DROID array to be used in the optical wavelength regime. The optimum absorber size has been found to be 30x400 um. The X-ray data has been obtained with a similar device structure but with 60 nm aluminium trapping layers to increase the trapping of quasiparticles in the STJs. In this paper we only present the data obtained with the standard DROID size of 400μm. With this device an extensive set of measurements have been performed which involves; a scan in photon energy ranging from 50eV to 1900 eV, a scan in temperature and a scan in bias voltage. We report here only results from the preliminary analysis of the data obtained with readout electronics comprising the normal preamplifier and subsequent shaping stage. For the final analyzes the pulses resulting from the STJs have been digitized and are ready to be analyzed. The pulses have been used to estimate the decay time of the STJs which appear to be very short. This is probably caused by the poor trapping of quasiparticles. Detailed results on this process will be presented however at a later date.

We are presenting the preliminary characterization results of the Rockwell Scientific HgCdTe detector array used in the Near Infrared Camera and Fabry-Perot Spectrograph (NIC-FPS). The detector was fabricated to cover the wavelength range from 0.8 to 2.5 microns and is bonded to a Hawaii-1RG multiplexer. This instrument was designed and built at the University of Colorado in Boulder and is used at the Apache Point Observatory's 3.5 meter telescope.

Thorough numerical simulations were run to test the performance of three processing methods of the data coming out from an electron multiplying charge coupled device (EMCCD), or low light level charge coupled device (L3CCD), operated at high gain, under real operating conditions. The effect of read-out noise and spurious charges is tested under various low flux conditions (0.001 event/pixel/frame< f < 20 events/pixel/frame). Moreover, a method for finding the value of the gain applied by the EMCCD amplification register is also developed. It allows one to determine the gain value to an accuracy of a fraction of a percent from dark frames alone.

A project to upgrade PUEO, the CFHT AO system, was first proposed in 2002. As part of the upgrade effort, a technology project was conceived to evaluate and characterize the backside-illuminated CCID-35 detector as suitable a replacement for the array of avalanche photo diode modules (APDs) in the curvature wavefront sensor. The CCID-35 was envisioned to replace an array of expensive APDs thus providing a cost-effective means of upgrading PUEO to a higher-order system. Work on the project, dubbed FlyEyes, occurred sporadically until Oct 2005 but substantial progress has been made since. This paper was intended to report on the performance of FlyEyes in PUEO but unfortunately the instrument was not ready for tests at the time of this writing. This paper summarizes the progress made on the project thus far and touches upon some of the difficulties encountered.

Sensitive, photon counting array detectors have the potential to dramatically improve the sensitivity of space-based astronomical spectrographs. We present first results from a program evaluating e2v L3 electron-multiplying CCDs as photon counting arrays. We find that L3 CCDs function well as photon counters, and see no show stoppers for our target applications. These include both ground and space-based instruments. Although we do detect spurious charge exceeding the dark current floor of the CCD, we find that physical dark current in the multiplication register is a significant component. This finding is significant because dark current, unlike clock induced charge (another potential culprit), is a problem that CCD designers have solved before.

Charge transfer efficiency (CTE) is a very important characteristic parameter for the CCD in the scientific imaging applications, especially in the imaging systems used to observe very faint objects such as night astronomical cameras. Several popular CTE measurement techniques are introduced briefly in this paper, deficiencies in the techniques are pointed out, and then some improvements are made. The modified algorithm for CTE measurement is based on the x-ray transfer and the MATLAB. When the algorithm begins, an appropriate initial charge transfer line from the x-ray single-pixel-events plot and its interzone for computation are determined by the user-PC interaction, and then a linear fit is performed in the interzone so as to get a more accurate transfer line. Thus a new interzone is obtained and a next linear fit can be done. In this way, a more accurate value of CTE can be obtained. Usually the algorithm stops after 5 to 10 iteration steps. Moreover the accuracy of the algorithm is discussed. Finally, the algorithm is used to estimate the horizontal CTE for 2 KAF-4301E CCDs tested at low temperatures. The results indicate that, when the CCD operating temperature is reduced below its absolute minimum rating, although the dark current performance improves obviously, the CTE performance degrades rapidly. An analysis and discussion for the results at the depth of theory is presented.

In this paper, the feasibility of CMOS imagers for astronomical application was evaluated as well as evaluation methods were studied. A camera based on IBIS5 CMOS sensor was built. Evaluation results of this sensor were also presented including readout noise, gain, linearity, dark current, full well capacity and pixel nonuniformity. Experimental observations of solar flare were carried out with Hα solar telescope in Huairou Solar Observation Station (HSOS), and the solar flare in NOAA AR0742 on March 13, 2005 was successfully observed with this IBIS5 CMOS camera. The results show a favorable aspect of the CMOS imager in large dynamic range astronomical imaging.

In the interest of expanding our ground-based observation to the infrared spectral range, we have built a short wave (SW) infrared imaging system operating in 0.9-2.5μm. It is based on a commercial infrared focal plane array (IRFPA) assembly from Sofradir, France. We have changed the cooling mode of this module from thermoelectric cooler (TEC) to liquid nitrogen to further reduce the dark current of detector. A camera controller based on the soft-core embedded processor and the relevant acquisition software has been also developed. This paper presents each part of the infrared imaging system in detail and the preliminary results of testing and astronomical observation.

Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the focal plane instruments on the Chandra X-ray Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's radiation belts. The primary effect of the damage was to increase the charge transfer inefficiency (CTI) of the eight front illuminated CCDs by more than two orders of magnitude. The ACIS instrument team is continuing to study the properties of the damage with an emphasis on developing techniques to mitigate CTI and spectral resolution degradation. We present the initial temperature dependence of ACIS CTI from -120 to -60 degrees Celsius and the current temperature dependence after more than six years of continuing slow radiation damage. We use the change of shape of the temperature dependence to speculate on the nature of the damaging particles.

Delta Sigma digitizers generally have excellent linearity, precision and noise rejection. They are especially well suited for implementation as integrated circuits. However, they are rarely used for time bounded signals like CCD pixels. We are developing a CCD video digitizer chip incorporating a novel variant of the Delta Sigma architecture that is especially well suited for this application. This architecture allows us to incorporate video filtering and correlated double sampling into the digitizer itself, eliminating the complex analog video processing usually needed before digitization. We will present details of a multichannel ASIC design that will achieve spectroscopic precision and linearity while using much less energy than previous CCD digitizers for technical applications such as imaging X-ray spectroscopy. The low conversion energy requirement together with the ability to integrate many channels will enable us to construct fast CCD systems that require no cooling and can handle a much wider range of X-ray intensity than existing X-ray CCD systems.

We report the results of a program to mitigate defect induced (tunneling) dark current which arises from lattice mismatch between In_0.82Ga_0.18As 'extended wavelength' detector material and the InP substrate upon which it is grown. Our goal is to produce material suitable for ground-based broadband astronomical observation by achieving a dark current level in individual 25x25μm array pixels which is less than the atmospheric airglow and telescope thermal emission in the astronomical H (1.50-1.80 μm) and Ks (2.00-2.32 μm) bands. We have cryogenically tested multiple growths of candidate materials, packaged as both individual diodes and focal plane arrays, supplied by Sensors Unlimited, Inc. (SU). Results indicate dark current levels, in the current generation of array materials, surpassing the requirements for broadband imaging, and with the potential to be used for narrow band imaging and low-resolution spectroscopy.

CATAVIÑA is a near-infrared camera system to be operated in conjunction with the existing multi-purpose nearinfrared optical bench "CAMALEON" in OAN-SPM. Observing modes include direct imaging, spectroscopy, Fabry- Perot interferometry and polarimetry. This contribution focuses on the optomechanics and detector controller description of CATAVIÑA, which is planned to start operating later in 2006. The camera consists of an 8 inch LN2 dewar containing a 10 filter carousel, a radiation baffle and the detector circuit board mount. The system is based on a Rockwell 1024x1024 HgCdTe (HAWAII-I) FPA, operating in the 1 to 2.5 micron window. The detector controller/readout system was designed and developed at UNAM Instituto de Astronomia. It is based on five Texas Instruments DSK digital signal processor (DSP) modules. One module generates the detector and ADC-system control, while the remaining four are in charge of the acquisition of each of the detector's quadrants. Each DSP has a built-in expanded memory module in order to store more than one image. The detector read-out and signal driver subsystems are mounted onto the dewar in a "back-pack" fashion, each containing four independent pre-amplifiers, converters and signal drivers, that communicate through fiber optics with their respective DSPs. This system has the possibility of programming the offset input voltage and converter gain. The controller software architecture is based on a client/server model. The client sends commands through the TCP/IP protocol and acquires the image. The server consists of a microcomputer with an embedded Linux operating system, which runs the main program that receives the user commands and interacts with the timing and acquisition DSPs. The observer's interface allows for several readout and image processing modes.

We have been developing fully-depleted CCDs fabricated on N-type silicon wafer in collaboration with HAMAMATSU Photonics K.K.We have made several wafer runs to optimize the basic characteristics of the devices such as the charge transfer efficiency (CTE), the full-well capacity and the amplifier gain, followed by the optimization of the backside treatment to improve quantum efficiency (QE) in blue wavelengths. The optimization process is successfully completed, and Hamamatsu recently started to deliver the 2k × 4k (15 μm pixel) four-side buttable devices for acceptance evaluation at the National Astronomical Observatory of Japan. Based on the measured QE in the X-ray, the depletion depth reaches 200 μm with CTE as good as >0.999995 for serial and parallel directions and with readout noise of < 5 e- for 130 kHz readout. The size of charge diffusion is estimated to be < 7.5 μm (one sigma) for pinhole image at wavelength of 450 nm. The device flatness is < 15-20 μm, and the dark current is a few e-/hour/pixel at -100°C and ~ 20 e-/hour/pixel at -80°C.

Sensors for the LSST camera require high quantum efficiency (QE) extending into the near-infrared. A relatively large thickness of silicon is needed to achieve this extended red response. However, thick sensors degrade the point spread function (PSF) due to diffusion and to the divergence of the fast f/1.25 beam. In this study we examine the tradeoff of QE and PSF as a function of thickness, wavelength, temperature, and applied electric field for fully-depleted sensors. In addition we show that for weakly absorbed long-wavelength light, optimum focus is achieved when the beam waist is positioned slightly inside the silicon.

1K x 1K Si:As Impurity Band Conduction (IBC) arrays have been developed by Raytheon Vision Systems for the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). These devices are also suitable for other low-background applications. The Si:As IBC detectors have a pixel dimension of 25 μm and respond to infrared radiation between 5 and 28 μm. Detector performance results are discussed, including response and dark current as a function of detector bias and relative spectral response. The features of the matching 1024 x 1024 Readout Integrated Circuit (ROIC) features are discussed. Noise data from the University of Rochester are shown with the ROIC operating at 7 K. Sensor Chip Assembly (SCA) data are presented showing noise, response uniformity, and dark current. Design details of a companion 1024 x 1024 array suitable for high-background, ground-based astronomy will also be revealed for the first time. This array will have a large well capacity and be capable of high frame rates.