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We have developed a new readout ASIC for high-resolution gamma-ray spectroscopy, which can be flip-chip bonded directly to a two-dimensional solid-state pixel array. This chip, called DANA-3 (Detector Array for Nuclear Applications), has a 16 × x16 array of anode readout channels with a pitch of 0.5 mm × 0.5 mm, plus an extra channel optimized for the cathode signals. To minimize power consumption, the ASIC was designed in a 0.18 µm process. To further reduce power dissipation, we incorporated automatic switching between different modes of operation (Watchdog, Counting, and Spectroscopy) depending on user-selectable radiation level thresholds, an ability to power down unused channels, and a low-power, low-noise differential I/O interface. Power dissipation ranges from 7 mW in watchdog mode to 50 mW with all channels enabled in spectroscopy mode. In the latter mode, the circuit features low-noise, high-energy resolution performance and allows for depth-of-interaction optimization using the cathode signal. The ASIC layout is three-side abuttable, so individual circuits can be combined into larger arrays. For optimal performance of the ASIC in different applications the main parameters of the analog channels can be programmed (globally or individually) over a wide range. In this paper we describe the ASIC design details and preliminary results of lab testing and characterization, including noise measurements and testing with pulser signals.

We have developed a pixel detector hybrid called DANA-2 (Detector Array for Nuclear Applications). DANA-2 consists of a two-dimensional, monolithic Cadmium Zinc Telluride (CZT) detector array flip-chip bonded directly to a readout IC designed for high energy resolution. Both the detector and the IC have 16 × 16 pixels with a pitch of 0.5 mm × 0.5 mm; the detector thickness is 3 mm. Each readout channel features a low-noise, charge-sensitive input amplifier with continuous-reset feedback and two selectable energy ranges; a gain amplifier with a five-bit gain adjustment and eight-bit offset DAC; a shaper with eight selectable shaping times ranging from 0.5 μs to 4 μs; a peak detector; and a trigger comparator. The data readout is controlled by a programmable token logic, which affords the user a high degree of flexibility in the selection of nearest-neighbor channels to be read out to account for charge sharing between pixels. To process the signals from the detector cathode, one of the readout channels, which is normally connected to a corner pixel, can instead be connected to the cathode through a dedicated I/O pad. The different characteristics of these cathode signals are accommodated through user configuration options for the signal polarity and input FET size. Other features of DANA-2 include the ability to disable the trigger on any channel and thus turn off “hot” pixels, and several test features such as an AC-coupled test signal input and the option to operate any peak detector in follower mode and connect it to the analog output to continuously monitor the shaper signal. We present below details of the DANA-2 design and first results from its performance characterization.

The RENA-3 (Readout Electronics for Nuclear Applications) is a 36-channel self-resetting, charge sensitive amplifier/shaper IC with trigger output, wide energy range and sparse readout designed for use with position-sensitive, spectroscopy-grade radiation detectors. It has in recent years been favored to provide the front-end electronics in prototype instruments for various applications — from space physics research through medical imaging to homeland security — that employ CZT or CdTe in the form of planar sensor assemblies or monolithic pixel/strip arrays. We will present a summary of spectroscopic data drawn from the body of RENA-3-based results obtained in our laboratories and by other RENA-3 users. Spectroscopic performance metrics will be discussed relative to the requirements of the specific application targeted in each case as well as from the general standpoint of what may be achievable within this detector-array/RENA-3 approach. A method to automate the test and calibration of RENA-3 ICs will also be described.

We have developed a new, improved version of the XENA (X-ray ENergy-binning Applications) readout IC for solid-state x-ray detector arrays, which we call XENA-2. This IC consists of 32 readout channels, each with charge-sensitive input amplifier, two-stage gain amplifier, and five comparators followed by 16-bit pulse counters. The resistive feedback of the input amplifier is provided by a transconductance circuit with continuously variable, user-controlled transconductance, which allows the amplifier’s shaping time to be varied between 100 to 150 ns and 4 μs. Two input amplitude ranges, 7 fC and 30 fC nominal (200 keV and 800 keV, respectively, for Cadmium Zinc Telluride), can be selected by switching different capacitors into the feedback path. The gain amplifier design includes a five-bit gain adjustment and a ten-bit R-2R offset DAC. The five comparator threshold voltages are supplied externally and are common to all channels; digitally controlled threshold adjustments at each comparator allow to compensate for process variations. Readout of the counters, over a 16-bit data bus, takes approximately 20 μs. Two additional analog-only channels (that is, without the comparators and counters) are provided, one at each end of the channel array; they are used for test purposes and to improve the uniformity of the full channels. Compared to XENA, this new IC’s main improvement is significantly reduced noise, which allows for lower comparator thresholds and increased count rates. XENA-2 is fully pin-compatible with XENA and replaces it as the readout IC used in NOVA’s NEXIS detector system.

We have developed a new version of the MARY (MAmmogRaphY) pixel detector with its custom readout integrated circuit (IC) optimized for electron collection in semiconductor detectors such as CdZnTe (CZT), CdTe, a-Se and GaAs. This new pixel detector and readout IC, the MARY-N50, is essentially comprised of a 192 x 384 array of channels at a 50 μm x 50 μm pitch, which can be flip-chip bump-bonded with a matching detector pixel array. A 100 μm pitch pixel detector, the MARY-N100, was also developed, with a 64 x 192 pixel array. Standard features of both versions of MARY-N include: TDI (Time Delay Integration) or “staring” CCD readout capability; low noise and wide dynamic range; internal clock drivers; fat zero input; overflow control; multiple independent readout stages (24 for MARY-N50, 8 for MARY-N100) to accommodate large charge collection due to direct conversion.

Multiple-site interactions initiated by Compton scattering are the primary interaction processes of gamma-rays in CZT in ~0.2 - several MeV range. Thus, exploiting gamma-rays as directional and spectral diagnostic probes requires detectors with 3-D resolution that resolve and measure individual interaction site's locations and energies. Desirable capabilities for Compton telescopes appear to be a spatial resolution of ~1 mm and an energy resolution of ~1 percent. Such capabilities are also important for coded mask imagers above 250 keV, where 3-D resolution can greatly improve the identification of a gamma-ray's initial interaction site, which is crucial for imaging. Significantly improved spectral resolution can be anticipated with CZT when multi-site interactions are resolved. This will allow each site's energy signals to be corrected for the site's specific signal loss characteristics, and the summed energies will then provide an accurate measure of the incident gamma-ray energy. We report on progress toward the development of 5 - 10 mm thick CZT detectors and electronics that are pursuing these objectives. Position sensing is provided by anode pixels with ~1 mm pitch for x-y positions and charge drift times for z-positions. Detectors are read out with the new RENA-2 ASIC. This chip contains preamplifiers, shaping amplifiers, threshold triggering, and peak detection for each of its 36 channels. To optimize energy resolution for various detector types and event rates, the RENA-2's peaking times and other parameters are adjustable. Each channel has a novel fast time stamp function that can record interaction times to ~10 nsec, allowing precise measurements of charge drift times and making PET imaging possible. The detector and ASIC designs are described and results are presented on tests of thresholding, energy resolution, and time resolution

We have developed a multi-channel, mixed-signal integrated circuit (IC) as part of a resource-conserving approach to the design of instruments for missions flown under the Geospace Missions Network (GMN) of NASA's Living With a Star (LWS) program. Specifically, the IC was designed to read out microchannel plates (MCPs) which allow detection of single hot plasma particle by emitting a pulse of charge when struck by the plasma particle. The IC, named AIDA (AlowbarmplIlowbarfier Dlowbariscriminator AlowbarSIC) includes several Charge-Amplifier Discrminators in one package without sacrificing performance, thus simplifying the MCP electronics and saving on space, power and cost. Reduction of power and mass requirements by several tens of percent relative to existing MCP instrument electronics was the primary goal. A secondary goal was to integrate the pulse counting function into the IC, thereby eliminating the need for additional counters and conserving resources further. We present the features and capabilities of the AIDA IC and evaluation system, and initial characterization data for the chip.

A multi-channel front-end readout IC is developed for position sensitive solid-state detectors. It is called RENA-3. It has 36 low noise channels. Each channel has externally selectable input polarity. The channel inputs are optimized for 2 or 9 pF detector capacitance, which is externally selectable. It also has selectable dual energy range, 56K and 338K electrons (250 keV and 1.5 Mev for CZT, respectively). A fast trigger output is provided applications that require timing. A novel circuit produces arrival time difference measurement for each channel. It is developed to serve as front-end readout electronics for a variety of position-sensitive solid-state semiconductor detectors such as CdZnTe, Si, GaAs and HgI2. It also has flexibility for use with other types of solid-state detectors such as Ge, Se, PbI2 and CdTe in a multichannel strip or pixel geometry to detect and image x-rays and gamma-rays with energies up to 1.3 MeV. Also a novel register circuit and process allows nearest neighbor readout capability for pixel detectors. Combination of RENA-3 chips with a variety of semiconductor detectors would be suitable for numerous applications in astrophysics, nuclear physics, nuclear medicine, security and industrial imaging. Some possible applications include gamma camera, SPECT, small animal PET and SPECT, nuclear source detection and spectroscopy, space x-ray and gamma-ray astronomy missions, NDE and NDI.

We have developed custom two-dimensional (2-D) mixed signal readout integrated circuits (ICs) for advanced position sensitive hybrid solid-state radiation detectors. The 2-D readout ICs are an integral part of hybrid semiconductor pixel detectors developed for x-ray, gamma-ray and charged particle imaging. Different detector applications require custom IC, which is typically designed for a specific 2-D detector array. Therefore, it is challenging to develop generic ICs to meet a range of applications in different complementing fields. To approach this aim NOVA has put significant effort on developing its ICs as flexible as possible to address differences in the fields of application. Therefore, these ICs embody versatile and adaptable functions as well as selectable features. An overview of 2-D ICs recently developed at NOVA and their functionality and features will be presented. Preliminary test results will be discussed. These ICs can be used for applications ranging from x-ray astronomy and medical imaging to munitions, security and industrial inspection. Some potential applications are: gamma camera; SPECT; PET; CT; digital mammography & radiography; baggage scanner; NDI and NDE.

In this paper we present the status and preliminary results from a CZT development program of fine pixel detectors. These are to be used at the focus of high-energy grazing-incidence optics (20-75 keV) of the HERO-Experiment under construction at the Marshall Space Flight Center.

A new mixed signal integrated circuit (IC) for front-end readout electronics of position sensitive solid state detectors has been developed. It is called RENA-2 and can be used for readout of position sensitive solid state detectors such as CdTe, CdZnTe, Ge, GaAs, HgI2, PbI2, Se and Si strip, pad and pixel detectors, with large numbers of channels. It is designed to have very low noise and, therefore, high energy resolution. It has numerous possible applications in astrophysics, medical and industrial imaging, security such as baggage inspection and nuclear physics. The RENA-2 chip is a monolithic integrated circuit and has 36 channels with low noise, high input impedance charge sensitive amplifiers. The RENA-2 chip can be optimized for individual applications

We have developed compact detector modules for high-resolution PET imaging. The modules consist of arrays of four by four 20 mm long LYSO crystals whose scintillation signals are read by avalanche photodiode arrays. The scintillator arrays are instrumented at both ends to facilitate depth-of-interaction determination by measuring the pulse-height ratio between the two ends of the LYSO crystal. To process the diode signals, we have developed a custom multi-channel integrated readout chip designed for excellent coincidence time resolution and low power dissipation. The IC offers various configuration options to allow for a high degree of flexibility in the design of the imaging system

As applications of advanced solid-state radiation detector arrays proliferate across disciplines ranging from X-ray astronomy and medical imaging to security and industrial inspection, the relative scarcity of low-noise, multi-channel integrated circuits (ICs) needed to read out these arrays has become increasingly apparent. In fact, readout ICs are now regarded to be an integral part of position-sensitive semiconductor detectors for X-ray and gamma-ray imaging. Because the requirements of various detector applications tend to be diverse, a custom IC is typically designed for a specific detector array. This often lengthens the time and raises the cost of system development. To help close the readout technology gap and facilitate advances in this field, NOVA has been formulating strategies for instrumenting different detectors of a given application category with the same "generic" IC which embodies common functions as well as selectable features. A brief overview of possible approaches to such generic ICs will be given. Within this context, accomplishments and ongoing efforts at NOVA in developing front-end ICs for various detector architectures and signal-processing scenarios will be described. We will especially consider the case of ICs used in conjunction with position-sensitive CZT detectors, implemented in traditional soldered lead or flip-chip connection geometries, to perform spectroscopic, energy-binning or current-mode type measurements

We have been developing custom multi channel mixed signal readout integrated circuits (ICs) for advanced position sensitive solid-state radiation detector arrays for applications ranging from X-ray astronomy and medical imaging to security and industrial inspection. Readout ICs are an integral part of position-sensitive semiconductor detectors for X-ray, gamma-ray and charged particle imaging. Different detector applications require custom IC, which is typically designed for a specific detector array. Therefore, it is important to develop generic ICs to meet a range of applications in different complementing fields. To achieve this aim NOVA has been developing generic ICs for different fields of applications, which embodies versatile and adaptable functions as well as selectable features. An overview of generic ICs developed at NOVA is presented here. Each chip described targets a complementing application field with versatile functions and features.

A wide field-of-view, arcsecond imaging, high energy resolution X-ray and low energy gamma ray detector is proposed for a future space mission. It is specifically designed to detect and find counterparts at other wavelengths for gamma ray bursts (GRBs). Detection of GRBs require wide field-of-view (/spl pi/ to 2/spl pi/ field-of-view) and high sensitivity. This will be achieved by using high quantum efficiency CdZnTe pixel detectors, low energy threshold (few keV) to observe larger flux levels that may be possible at lower energies and large effective area (625 to 1,000 cm/sup 2/) per coded aperture imaging module. Counterpart searches can only be done with ultra high angular resolution (10 to 30 arcsecond FWHM) which gives 1 to 5 arcsecond position determination especially for strong GRBs. A few arcsecond resolution error box is expected to contain only one counterpart observed at another wavelength. This will be achieved by using ultra high spatial resolution pixel detectors (50/spl times/50 to 100/spl times/100 micron) and a similar resolution coded aperture to achieve the required angular resolution. AXGAM also has two other important advantages over similar detectors: (1) excellent low energy response (>1 keV) and (2) high energy resolution (

A mixed signal Application Specific Integrated Circuit (ASIC) chip for front end readout electronics of position sensitive solid state detectors has been developed. The new ASIC is called RENA (Readout Electronics for Nuclear Applications). This chip can be used for large number of channels and high energy resolution astrophysics and nuclear physics detectors, and medical imaging instruments such as solid state gamma camera, Compton SPECT and Intraoperative probes. It can also be used for industrial imaging of X-rays and gamma rays used in nondestructive evaluation (NDE) and inspection (NDI). The RENA chip is a monolithic integrated circuit and has 32 channels with low noise charge sensitive amplifiers followed by a polarity amplifier and a high quality shaper circuit. It works in pulse counting mode with good energy resolution. It also has a self-triggering output which is essential for nuclear applications when the incident radiation arrives at random. Different, externally selectable, operational modes that include a sparse readout mode are available to increase data throughput. It also has externally selectable shaping (peaking) times. A full scale prototype RENA chip has been manufactured. The preliminary results of tests done on the prototype chip are presented.

A Readout Electronics for Nuclear Applications (RENA) Chip has been developed to read out position sensitive solid state detectors for the nuclear instruments. This chip can also be used for medical and industrial imaging of X-rays and gamma rays. It is a multi channel monolithic mixed signal application specific integrated circuit (ASIC) chip. The RENA chip has 32 channels with low noise charge sensitive amplifier inputs. It works in pulse counting mode with good energy resolution. It also has a self triggering output which is essential for nuclear applications when the incident radiation arrive at random. Different, externally selectable, operational modes that includes a sparse readout mode is available to increase data throughput. The design of the chip and the results of tests done on a full scale prototype chip will be presented.

An ASIC-based readout electronics scheme is under development for high resolution, compact PET imagers based on independent readout of all channels of LSO scintillator and avalanche photodiode (APD) arrays. Depth of interaction is obtained by readout of both ends of the LSO crystals. A low power, highly integrated design is critical. We report here on a discrete electronics prototype, running at 22 mW per channel for the preamplifier and discriminator. The measured timing resolution is 3.6 ns FWHM, 9.2 ns full width at one tenth maximum, relative to an LSO/PMT detector, energy resolution is 13.3% FWHM at 511 keV, and depth of interaction position resolution is 2.5 mm FWHM throughout the full length of the crystal. Work is in progress towards an ASIC and a full scale prototype detector module suitable for a high resolution compact PET instrument.

New, high spatial resolution CdZnTe (CZT) and silicon (Si) pixel detectors are developed for high angular and high energy resolution X-ray astronomy. These detectors can be used for wide field-of-view all-sky X-ray, and gamma-ray monitors such as the AXGAM instrument and focusing X-ray imagers such as the high energy detector (HXT) proposed for the CONSTELLATION mission. The high stopping power of CZT detectors combined with low-noise front-end readout electronics ASIC (application specific integrated circuit) makes possible an order of magnitude improvement in spatial (angular) and energy resolution in X-ray detection. If silicon pixel detectors are used the energy threshold can be lowered. The preliminary test results obtained from our first silicon and CZT pixel detectors are presented. These detectors may also be used with or without modification for medical and industrial imaging.

A linear CdZnTe pad detector array with approximately 1 mm/sup 2/ pad area has been developed. The detector has a wide energy range from about 20 to 200 keV. A fast, low-noise monolithic mixed signal ASIC chip has been developed to read out these detector arrays. A prototype X-ray imaging system consisting of the CdZnTe detector array and the monolithic ASIC chip has been fabricated and tested. In this system, the detectors are abutted against each other to form an approximately 1 m long linear array. The system has been used to take preliminary scanned images of complex objects at various energies. New results obtained from this system is discussed.