The Application-Specific Integrated Circuit (ASIC) development plan of the astronomical CCD control system is a special chip development project launched officially by the National Astronomical Observatory of the Chinese Academy of sciences. One of the scientific objectives: Bias and Clock Driver ASIC (CDA), has been designed and manufactured twice. The test shows the performance of CDA completely reach the design requirement. Now this chip can be mass produced at low cost. We claim the CDA is successfully developed in our laboratory. CDA provides bias voltage and clock drives for CCD working. 48 DACs which produce pulse at any amplitude can be used for most CCD controller. The combination of CDA and ASIC lead to integrated multi-CCD system or sub-mini single CCD controller. This high integrated chip make the CCD controller smaller, lower power consumption, more stable and easier to be developed.
Astronomical instrumentation, in many cases, especially the large field of view application while huge mosaic CCD or CMOS camera is needed, requires the camera electronics to be much more compact and of much smaller the size than the controller used to be. Making the major parts of CCD driving circuits into an ASIC or ASICs can greatly bring down the controller's volume, weight and power consumption and make it easier to control the crosstalk brought up by the long length of the cables that connect the CCD output ports and the signal processing electronics, and, therefore, is the most desirable approach to build the large mosaic CCD camera. A project endeavors to make two ASICs, one to achieve CCD signal processing and another to provide the clock drives and bias voltages, is introduced. The first round of design of the two ASICs has been completed and the devices have just been manufactured. Up to now the test of one of the two, the signal processing ASIC, was partially done and the linearity has reached the requirement of the design.
This paper is intended primarily for the LAMOST UCAM CCD systems. The illustrations given here
show the prototype LAMOST UCAM systems. Designed as a universal CCD controller, the UCAM
system has variety options of readout modes, sampling speeds, binning options and charge clean. Its
main components, architecture and technical design are introduced here. Some important performance
characteristics about the UCAM controller and the e2v-203-82 CCD (4K by 4K, blue CCD) are tested
under laboratory conditions, such as readout noise and gain at different sampling modes and readout
speeds, CTE, dark current, QE, and fringing. Perfect CTE and less than 3 electrons / pixel system
readout noise prove that the UCAM CCD controller system meets the requirement of the LAMOST
A mosaic of two 2k x 4k fully depleted, high resistivity CCD
detectors was installed in the red channel of the Low Resolution
Imaging Spectrograph for the Keck-I Telescope in June, 2009 replacing
a monolithic Tektronix/SITe 2k x 2k CCD. These CCDs were fabricated
at Lawrence Berkeley National Laboratory (LBNL) and packaged and
characterized by UCO/Lick Observatory. Major goals of the detector
upgrade were increased throughput and reduced interference fringing
at wavelengths beyond 800 nm, as well as improvements in the
maintainability and serviceability of the instrument. We report on
the main features of the design, the results of optimizing detector
performance during integration and testing, as well as the
throughput, sensitivity and performance of the instrument as
characterized during commissioning.
The Lawrence Berkeley National Laboratory has been developing fully-depleted high resistivity CCDs. These CCDs exhibit very high red quantum efficiency, no red fringing, and very low lateral charge diffusion, making them good candidates for astronomical applications that require better red response or better point spread function than can typically be achieved with standard thinned CCDs. For the LBNL 2Kx4K CCD we have developed a four-side mosaic package fabricated from aluminum nitride. Our objectives have been to achieve a flatness of less than 10 micrometers peak-to-valley and a consistent final package thickness variation of 10 micrometers or less in a light-weight package. We have achieved the flatness objective, and we are working toward the thickness variation objective.
The new UCO/Lick Observatory CCD camera uses a 200 MHz fiber optic cable to transmit image data and an RS232 serial line for low speed bidirectional command and control. Increasingly RS232 is a legacy interface supported on fewer computers. The fiber optic cable requires either a custom interface board that is plugged into the mainboard of the image acquisition computer to accept the fiber directly or an interface converter that translates the fiber data onto a widely used standard interface. We present here a simple USB 2.0 interface for the UCO/Lick camera. A single USB cable connects to the image acquisition computer and the camera's RS232 serial and fiber optic cables plug into the USB interface. Since most computers now support USB 2.0 the Lick interface makes it possible to use the camera on essentially any modern computer that has the supporting software. No hardware modifications or additions to the computer are needed. The necessary device driver software has been written for the Linux operating system which is now widely used at Lick Observatory. The complete data acquisition software for the Lick CCD camera is running on a variety of PC style computers as well as an HP laptop.
The DEIMOS spectrograph is a multi-object spectrograph being built for Keck II. DEIMOS was delivered in February 2002, became operational in May, and is now about three-quarters of the way through its commissioning period. This paper describes the major problems encountered in completing the spectrograph, with particular emphasis on optical quality and image motion. The strategies developed to deal with these problems are described. Overall, commissioning is going well, and it appears that DEIMOS will meet all of its major performance goals.
The remarkable sensitivity of depleted silicon to ionizing radiation is a nuisance to astronomers. 'Cosmic rays' degrade images because of struck pixels, leading to modified observing strategies and the development of algorithms to remove the unwanted artifacts. In the new-generation CCD's with thick sensitive regions, cosmic-ray muons make recognizable straight tracks and there is enhanced sensitivity to ambient gamma radiation via Compton-scattered electrons ('worms'). Beta emitters inside the dewar, for example high-potassium glasses such as BK7 , also produce worm-like tracks. The cosmic-ray muon rate is irreducible and increases with altitude. The gamma rays are mostly by- products of 40K decay and the U and Th decay chains; these elements commonly appear as traces in concrete and other materials. The Compton recoil event rate can be reduced significantly by the choice of materials in the environment and dewar and by careful shielding. Telescope domes appear to have significantly lower rates than basement laboratories and Coude spectrograph rooms. Radiation sources inside the dewar can be eliminated by judicious choice of materials. Cosmogenic activation during high-altitude fights does not appear to be a problem. Our conclusion are supported by tests at the Lawrence Berkeley National Laboratory low-level counting facilities in Berkeley and at Oroville, California (180 m underground).
We have developed an optical approach for modeling the quantum efficiency (QE) of back-illuminated CCD optical imagers for astronomy. Beyond its simplicity, it has the advantage of providing a complete fringing description for a real system. Standard thin-film calculations are extended by (a) considering the CCD itself as a thin film, and (b) treating the refractive index as complex. The QE is approximated as the fraction of the light neither transmitted nor reflected, which basically says that all absorbed photons produce e-h pairs and each photoproduced e or h is collected. Near-surface effects relevant to blue response must still be treated by standard semiconductor modeling methods. A simple analytic expression describes the QE of a CCD without antireflective (AR) coatings. With AR coatings the system is more easily described by transfer matrix methods. A two-layer AR coating is tuned to give a reasonable description of standard thinned CCDs, while the measured QE of prototype LBNL totally depleted thick CCDs is well described with no adjustable parameters. Application to the new LBNL CCDs indicates that these device swill have QE > 70 percent at (lambda) equals 1000 nm and negligible fringing in optical system faster than approximately f4.0.
In this paper we present new results from the characterization of a fully depleted CCD on high resistivity silicon. The CCD was fabricated at Lawrence Berkeley National Laboratory on a 10-12 K(Omega) -cm n-type silicon substrate. The CCD is a 200 by 200 15-micrometers square pixel array. The high resistivity of the starting material makes it possible to deplete the entire 300 micrometers thick substrate. This results in improved red and near IR response compared to a standard CCD. Because the substrate is fully depleted, thinning of the CCD is not required for backside illumination, and the result presented here were obtained with a backside illuminated device. In this paper we present measured quantum efficiency as a function of temperature, and we describe a novel clocking scheme to measure serial charge transfer efficiency. We demonstrate an industrial application in which the CCD is more than an order of magnitude more sensitive than a commercial camera using a standard CCD.
CCID20 CCDs are designed and produced by personnel at MIT/Lincoln Laboratory. The CCDs are thinned, back illuminated, 4096 X 2048 15-micrometer square pixel, three- side buttable devices. Some CCDs have been made on high- resistivity bulk silicon and others have been made on standard resistivity epitaxial silicon. Recently many devices from the first round of production of these CCDs have been tested at the UCO/Lick Observatory Detector Development Laboratory. In this paper we present the results of the measurements of horizontal and vertical charge transfer efficiency, low- temperature dark current, localized charge traps, full well, responsive quantum efficiency, and fringing. We present performance measurements of the on-chip amplifier including measurements of read-out noise, gain and linearity with different bias voltages. Cross-talk between the two on-chip amplifiers is discussed. High resistivity CCDs made by MIT/Lincoln show higher QE and less QE variation at long wavelengths than regular thin CCDs. However, they are subject to additional lateral charge diffusion and cosmic-ray effects. We will give a comparison between the two kinds of CCID20 CCDs. CCID20 CCDs are not MPP devices. It is much more difficult to get high full well, low spurious charge, low dark current and low residual image, simultaneously. We present optimized parallel clocks and a special erasing procedure to help solve these problems. Devices from this first round of CCID20 CCDs exhibit a rectangular pattern of QE variations caused by backside surface treatment problems.
Most scientific CCD imagers are fabricated on 30-50 (Omega) - cm epitaxial silicon. When illuminated form the front side of the device they generally have low quantum efficiency in the blue region of the visible spectrum because of strong absorption in the polycrystalline silicon gates as well as poor quantum efficiency in the far red and near infrared region of the spectrum because of the shallow depletion depth of the low-resistivity silicon. To enhance the blue response of scientific CCDs they are often thinned and illuminated from the back side. While blue response is greatly enhanced by this process, it is expensive and it introduces additional problems for the red end of the spectrum. A typical thinned CCD is 15 to 25 micrometers thick, and at wavelengths beyond about 800 nm the absorption depth becomes comparable to the thickness of the device, leading to interference fringes from reflected light. Because these interference fringes are of high order, the spatial pattern of the fringes is extremely sensitive to small changes in the optical illumination of the detector. Calibration and removal of the effects of the fringes is one of the primary limitations on the performance of astronomical images taken at wavelengths of 800 nm or more. In this paper we present results from the characterization of a CCD which promises to address many of the problems of typical thinned CCDs. The CCD reported on here was fabricated at Lawrence Berkeley National Laboratory (LBNL) on a 10-12 K$OMega-cm n-type silicon substrate.THe CCD is a 200 by 200 15-micrometers square pixel array, and due to the very high resistivity of the starting material, the entire 300 micrometers substrate is depleted. Full depletion works because of the gettering technology developed at LBNL which keeps leakage current down. Both front-side illuminated and backside illuminated devices have been tested. We have measured quantum efficiency, read-noise, full-well, charge-transfer efficiency, and leakage current. We have also observed the effects of clocking waveform shapes on spurious charge generation. While these new CCDs promise to be a major advance in CD technology, they too have limitations such as charge spreading and cosmic-ray effects. These limitations have been characterized and are presented. Examples of astronomical observations obtained with the backside CCD on the 1-meter reflector at Lick Observatory are presented.
This paper will describe in some detail tow new large area CCD image sensors designed specifically to be used either as a single imager or assembled in mosaics of CCDs. The devices have 2048 X 4096, 15 micrometers pixels; the difference being the orientation of the serial register. Performance data are presented on both front- and back-illuminated parts. In addition, a new production camera test system will also be described which is being used to screen test the Advanced Camera CCDs for the wide field and high resolution channels.
A new CCD based field acquisition and telescope guiding camera is being designed and built at UCO/Lick Observatory. Our goal is a camera which is fully computer controllable, compact in size, versatile enough to provide a wide variety of image acquisition modes, and able to operate with a wide variety of CCD detectors. The camera will improve our remote-observing capabilities since it will be easy to control the camera and obtain images over the Observatory computer network. To achieve the desired level of operating flexibility, the design incorporates state-of-the-art technologies such as high density, high speed programmable logic devices and non-volatile static memory. Various types of CCDs can be used in this system without major modification of the hardware or software. Though fully computer controllable, the camera can be operated as a stand-alone unit with most operating parameters set locally. A stand-alone display subsystem is also available. A thermoelectric device is used to cool the CCD to about -45c. Integration times can be varied over a range of 0.1 to 1000 seconds. High speed pixel skipping in both horizontal and vertical directions allows us to quickly access a selected subarea of the detector. Three different read out speeds allow the astronomer to select between high-speed/high-noise and low-speed/low-noise operation. On- chip pixel binning and MPP operation are also selectable options. This system can provide automatic sky level measurement and subtraction to accommodate dynamically changing background levels.
We describe the high resolution echelle spectrometer (HIRES) now in operation on the Keck Telescope. HIRES, which is permanently located at a Nasmyth focus, is a standard in-plane echelle spectrometer with grating post dispersion. The collimated beam diameter is 12', and the echelle is a 1 x 3 mosaic, 12' by 48' in total size, of 52.6 gr mmMIN1, R-2.8 echelles. The cross disperser is a 2 x 1 mosaic, 24' by 16 ' in size. The camera is of a unique new design: a large (30' aperture) f/1.0, all spherical, all fused silica, catadioptric system with superachromatic performance. It spans the entire chromatic range from 0.3 (mu) to beyond 1.1 (mu) , delivering 12.6-micron (rms) images, averaged over all colors and field angles, without refocus. The detector is a thinned, backside-illuminated, Tektronix 2048 x 2048 CCD with 24-micron pixels, which spans the spectral region from 0.3 (mu) to 1.1 (mu) with very high overall quantum efficiency. The limiting spectral resolution of HIRES is 67,000 with the present CCD pixel size. The overall 'throughput' (resolution x slit width) product achieved by HIRES is 39,000 arcseconds. Peak overall efficiency for the spectrograph (not including telescope and slit losses) is 13% at 6000 angstrom. Some first-light science activities, including quasar absorption line spectra, beryllium abundances in metal-poor stars, lithium abundances in brown-dwarf candidates, and asteroseismology are discussed.
Results are presented on the fabrication and characterization of a 4Kx2K three-side buttable CCD produced by Orbit Semiconductor, a silicon foundry in San Jose, California. This first run of wafers was produced to test the ability of Orbit to produce high quality scientific CCDs with the characteristics required for detectors to be used in optical instruments of the Keck Observatory. Also on the wafer are two 2Kx2K devices. Similar devices have been fabricated for us by Loral/Fairchild. Extensive characterization of the Loral devices has taken place over the past few years, so interest is high about the possibility that Orbit might become a second source for similar detectors. This paper presents the first results on the 4Kx2K CCDs, and those preliminary results include measurements of charge transfer efficiency, low-temperature dark current, on-chip amplifier read- out noise, localized charge traps, full well, and responsive quantum efficiency.
Results are presented on the fabrication and characterization of a 4 K X 2 K three-side buttable CCD produced by Orbit Semiconductor. This first run of wafers was produced to test the ability of Orbit to produce high-quality scientific CCDs with the characteristics required for detectors to be used in optical instruments of the Keck Observatory. Also on the wafer are two 2 K X 2 K devices. Similar devices have been fabricated for us previously by Loral/Fairchild. Extensive characterization of the Loral devices has taken place over the past few years, so interest is high about the possibility that Orbit might become a second source for similar detectors. This paper presents the first results on the 4 K X 2 K CCDs, including measurements of charge transfer efficiency, low-temperature dark current, on-chip amplifier readout noise, localized charge traps, full well, and responsive quantum efficiency.
A full frame, four million pixel CCD area array has been developed for high performance applications. The device consists of 2048(H) by 2048(V) active elements with four outputs, and is fabricated using a triple poly, buried n-channel CCD process. Design features which enhance array performance include a Multi-Pinned Phase (MPP) pixel design for reduced dark current, low noise output amplifiers, and a phosphor coating to extent the spectral response. Excellent performance is demonstrated with a dynamic range of 93 dB, a read noise of 2.5 electrons (r.m.s.) and dark current of 20 pA cm-2 (25 degree(s)C).
Ongoing experiments using thin electrically conducting transparent layers of Indium Tin Oxide to control the surface potential of thinned CCDs are described. The results are very encouraging with good uniform ultraviolet sensitivity being obtained from CCDs of different types and thinned by different processes. The enhanced response is stable in air and in vacuum for periods longer than a year. 2.
Results obtained in fabricating and testing of large CCD image sensors are reported. The emphasis is on high quantum efficiency, excellent charge transfer efficiency at low signal level, large pixel count, low readout noise, and very low dark current. The focus is on the use of the devices for optical astronomy where these parameters are most important. Test results for CCDs fabricated by Ford Aerospace and by EG Experiments to demonstrate the feasibility of a reproducible biased-gate using transparent indium tin oxide as a conducting layer over a silicon oxide insulating layer are discussed. Quantum efficiency of bias-gate thinned CCDs is compared with results obtained from a phosphor-coated front- illuminated CCD.