Integrated Readout Research Articles

2nd generation ASICs for CALICE/EUDET calorimeters

Imaging calorimetry depends heavily on the development of high performance, highly integrated readout ASICs embedded inside the detector which readout the millions of foreseen channels. Suitable ASICs prototypes have been fabricated in 2006-2007 and show good preliminary performance.

First results from the HEPAPS4 active pixel sensor

Active pixel sensors are monolithic solid state devices based on CMOS technology with the sensing element and front-end electronics integrated in the same substrate. The HEPAPS4 active pixel sensor is designed specifically for charged particle detection with future e + e - colliders as one possible application in high energy physics. The sensor has an array of 1024×384 pixels of size 15 × 15 μ m 2 , with the conventional design of three NMOS transistors implemented in the 20 μ m epi-layer. The signal of each pixel is multiplexed out on four ports and sampled by an off-chip ADC. The readout system developed for the chip features different reset modes, variable readout region and integration time, with the possibility of external triggering. This paper reports on the first characterisation of this device, using photonic methods to measure gain, linearity, dynamic range and dark current.

Line integration HgCdTe focal plane array

Line integration 384 × 288 Focal Plane Array (FPA) consists of HgCdTe (MCT) photodiodes array formed in the mercury cadmium telluride p-type epitaxial layers grown both by liquid phase epitaxy (LPE) or molecular beam epitaxy (MBE). Grown by these methods MCT layers have multilayer compound structure. Silicon readout integration circuit (ROIC) performs the photocurrents integration during one line signals output (one row of pixels) period, and signals multiplexing in two output channels from the focal plane. The photodiodes array pitch in each direction is 28 μm. The influence of MCT surface irregularities and imperfections of MCT epitaxial layers on number of defective elements is investigated.

Imaging detectors for 20–100 keV x-ray backlighters in high-energy-density experimental science petawatt experiments

We are developing a petawatt laser for use as a high-energy backlighter source in the 20–100 keV range on the National Ignition Facility (NIF). High-energy x-ray backlighters will be essential for radiographing high-energy-density experimental science (HEDES) targets, especially to probe implosions and high areal density planar samples. For these high energy backlighter imaging experiments, we are developing two types of detectors: a columnar grown CsI scintillator coupled to a 2 K×2 K charge-coupled device camera, and a CdTe crystal with special application specific integrated circuit readout electronics in a 508×512 format array. We characterized these sensors using Cd109 and Am241 radioactive isotopes. In addition, we employed them to measure the Sm Kα source size generated by the short pulse laser, JanUSP, at Lawrence Livermore National Laboratory. The CsI camera performed well, allowing a measurement of the Sm Kα source size. Calibration of this camera has shown that it has low noise and good resolution. The new CdTe camera performed well, however the noise level was too high for single photon counting. Some modifications to the camera will also be necessary in order to meet the needs of future hard x-ray experiments. Both cameras showed considerable promise as diagnostic tools for future high-energy x-ray backlighters for NIF HEDES experiments. This article will present the results of our characterizations of these detectors, and initial results from the JanUSP experiments.

Method for expanding the dynamic range of the readout integration circuits for uncooled microbolometer sensors

A simple and robust method for expanding the dynamic range of the readout circuits for uncooled microbolometer infrared sensor arrays is presented. The proposed method allows a reduction in the number of bits required for microbolometer nonuniformity compensation, significantly reducing the complexity of the pre-integration compensation circuity.

The magic cube and the pixel ionization chamber: detectors for monitor and dosimetry of radiotherapy beams

Tumor therapy takes advantage of the energy deposition of radiation to concentrate high doses in the target while sparing healthy tissue. Elective pathologies for highly conformal radiotherapies such as photon Intensity Modulated Radiotherapy (IMRT) and radiotherapy with hadrons are head and neck, eye, prostate and in general all tumors that are either deep or located close to critical organs. In the world there are several centers that are using such techniques and a common problem that is being experienced is the verification of treatment plans and monitoring of the beam. We have designed and built two detectors that allow 2D and 3D measurements of dose and fluence of such beams. The detectors allow measurements on big surfaces, up to 25∗25 cm2. The active media are parallel plate, strip and pixel segmented ionization chambers with front-end Very Large Scale Integration (VLSI) readout and PC based data acquistion. The description of dosimeter, chamber and electronics will be given with results from beam tests and therapy plan verification.

High definition X-ray microtomography using a conventional impact X-ray source

Although superior in most aspects, synchrotron (as opposed to laboratory) X-ray microtomography (XMT) scanners are not available or appropriate for all types of application. Scanners based on laboratory X-ray generators tend to produce images with poor signal to noise ratio (SNR) because of the relatively low output power of the micro-focus source. Such systems, in common with synchrotron XMT systems, are also susceptible to ring artefacts because of their third generation geometry. We have overcome both of these limitations by designing a laboratory scanner with a high dynamic range CCD X-ray camera, employing time delay integration readout for ring artefact elimination. A further advantage of this readout method is that the recorded image length (in terms of number of pixels) can exceed the length of the CCD. Prior to reconstruction, projections are corrected for beam hardening by use of a 5 th order calibration curve derived from a 7 stage Al step wedge. Use of this system is illustrated with an embedded human femoral head specimen, approximately 6 cm in diameter, imaged with 30 μm cubic voxels. The resultant 3D image showed good SNR, in spite of the specimens large diameter (in pixels).

Smart TDI readout circuit for long-wavelength IR detector

A smart time delay and integration (TDI) readout circuit is suggested which performs background suppression, cell-to-cell non-uniformity compensation, and dead pixel correction. Using the smart TDI readout circuit, the integration capacitor area occupying almost the whole area of a unit-cell can be reduced to one-fifth and transimpedance gain can increase by five times. From measurement results, it is found that the skimming current error for a few hundred nA background current is <1.25 nA corresponding to LSB/2 of ADC and the non-uniformity introduced by cell-to-cell background current variation is reduced to 1.02 nA.

Microsensor techniques for cardiovascular systems

Summary. Progress in semiconductor technology has been very fast in the last few years. One important fabrication process is the CMOS (Complementary Metal Oxide Semiconductor) process. This technology has been developed for the fabrication of electronic circuits, but is now also used for the fabrication of microsensors and microsystems by adding some compatible process steps. This contribution reports upon some examples for the application of CMOS-compatible physical microsensors with on-chip integrated read-out electronics in a cardiovascular ambient. Especially monolithically integrated pressure sensors and flow sensors for blood pressure and blood flow measurement are presented, representing the state-of-the-art techniques of CMOS-compatible surface micromachining and bulk micromachining. Due to the flexible design possibilities, the surface micromachined pressure sensor with a chip size of 0.7 mm × 7 mm or even smaller can be placed in a heart catheter with a diameter of 1 mm for blood pressure measurement in arterial vessels. Additionally a temperature sensor is integrated on the chip. In the same catheter application a flow sensor chip based on a hot-film anemometry principle measures blood flow dynamically with a fast response and low power consumption combined with small dimensions. A system with integrated circuits used for data acquisition with wireless data transfer of cardiovascular sensor signals from inside the body is also discussed.

A second generation charge integrator and encoder ASIC

A second generation charge integrator and encoder ASIC (QIE5) has been designed for the KTeV experiment at Fermilab. It is intended to be used in conjunction with a FADC (typically eight bits) to digitize photomultiplier tube (PMT) current pulses at a fast rate, with variable resolution over a 16 bit dynamic range. QIES integrates pulses of up to 30 ma peak on eight nonoverlapping binary scaled ranges. A system clock of up to 53 MHz controls the integration period and readout rate. The device is pipelined so that there is no signal deadtime. For each clock period, one range is selected depending on the signal magnitude, and the output of that range is routed to the QIES analog output and fed to the FADC to form the mantissa. The selected range is encoded and output as a three bit digital exponent. With this method, the measurement resolution is a relatively constant fraction of the signal over a large dynamic range. Previous reports have described a single ended device (QIE2) which had inherent limitations. The QIES is a fully differential design and contains numerous other features which provide significant performance improvements. The new design philosophy and test results are presented for the first time.

Focal Plane Array Sensor for Imaging Infrared Seeker of Antitank Guided Missile

Technological issues and Processes for fabrication of mercury cadmium telluride detector arrays, charge coupled device readout arrays and integration of these into a focal plane array sensor have been discussed. Mini arrays of 16 X 16 size have been realised and tested to prove the technology and process schedule with a view to scaling up this for larger arrays to be used in the antitank guided missile.

An ultra low noise multi-channel integrated readout for X-rays multi-detectors

The characteristics of a very general readout for X-rays multi-detectors are presented. This readout is composed of two integrated circuits of ten identical channels. The analog circuit provides an input equivalent noise charge of less than 70 e rms at room temperature that allows the elimination of scattered X-rays and other background in fluorescence excitation mode experiments, for photons energy higher than 10 keV interacting with a silicon detector. The typical full width at half maximum of the output pulse is 2.2 μs and the gain is 125 mV/fC for a total dc power consumption of about 35 mW/channel. The digital circuit is composed of a high accurate window comparator followed by a 16 bits counter and by a 16 bits buffer. It can be directly read by a computer through a parallel bus without interrupting the photons counting. The whole system provides a significant improvement in X-rays detector readout and will open new opportunities in experiments which require one or several of these three performances: high counting rate, high spatial resolution and high energy resolution.

Preliminary Results from the Automated Patrol Telescope CCD Camera

Abstract The University of NSW Automated Patrol Telescope (APT), a modified 0.5 m Baker-Nunn Schmidt telescope situated at Siding Spring Observatory, Coonabarabran, Australia, was opened in June 1989. It features the unique combination of an extremely fast (f/1) optical system with a CCD (Charge-Coupled Device) camera at the prime focus, capable of both fast (50 Hz TV-rate) imaging and slow-scan integrated readout via a low noise Correlated Double Sampling amplifier. This combination of optics and detector gives a wide field (0.9° × 1.4°) suited to observing extended objects including the LMC, SMC and galaxies in the Sculptor group. First images from the APT are presented along with the results of noise, linearity and dark current measurements made to date with a 12-bit analog-to-digital converter. Results were (ADU = Analog-Digital Unit):

Astronomical polarimeter with 2-D detector arrays

It is shown how fast (50–100 kHz) piezoelastic modulation of the full Stokes vector can be used in combination with large CCD-type detector arrays with long integration times. The technique is to use an optical demodulation system (replacing the lockin amplifiers in corresponding single-channel detector systems). This allows the CCD detectors to be used with integration times and readout rates as in ordinary photometry. Including an optical phase switch in the system, the effect of the large pixel-to-pixel sensitivity variations can be removed from the recorded polarization images. The beam splitter that suppresses atmospheric noise can be located immediately before the detectors instead of being part of the polarization analyzer.

A Multiwire Proportional Counter with Integral Readout Delay Line

A new concept for delay line readout of multiwire proportional counters for detecting the position of ionizing particles is described. It significantly reduces the complexity and cost of a multiwire system compared to alternative methods, making it attractive for space flight applications. This integral delay chamber can provide spatial resolution approaching 0.1 mm using Fe55, provided careful consideration is given to geometrical parameters that determine delay line bandwidth and phase distortion. For a chamber of 35 by 35 cm2 a delay of 20 ns/cm and attenuation of 0.05 dB/cm has been obtained. The delay line characteristics and electronic resolution, using a peak detection method, are given as a function of chamber geometry.

A multiwire proportional counter with integral readout delay line

A multiwire proportional counter which has an output signal delay related to ionizing event position is described. A spatial resolution of ±0.2 mm has been measured, using P10 gas and simple electronics. Higher resolutions should be possible with high gas gain mixtures.

Use of integration readout techniques for low absorbance samples in atomic absorption spectroscopy

An analog integrator is described and evaluated for the application of integrator techniques to low absorbing solutions by atomic absorption spectroscopy. Use of solid state operational amplifiers allows a stable, low drift integration of information signals to improve signal-to-noise ratios. The effects of experimental parameters are described and integration working curves are shown for solutions absorbing with 0–4% range.

Long-term Integration of Polarographic Currents and Its Analytical Application

Abstract The integral readout technique was applied to the accurate determination of average polarographic currents. The long-term integration of polarographic currents provides a useful method of compensating residual currents and thus of increasing the sensitivity and accuracy of the d. c. polarographic analysis. The analytical utility of the proposed method was tested with cadmium, lead, and zinc ions in chloride solutions; these ions were found to be determined with reasonable accuracy even at concentrations as low as 10−6 m. Depolarizers at concentrations of the order of 10−4 m can be determined accurately in air-saturated solutions. The present method has the considerable merit that its sensitivity is not affected by the degree of reversibility of the electrode reaction. The integral technique was also applied successfully to the compensation of residual currents by the twin-cell system, in which a pair of dropping mercury electrodes is not necessarily synchronized.

Performance characteristics of pulsed phototransistor structures under various conditions

Measurements are made on linear and area arrays of phototransistors operating in the steady-state and pulsed (integration) modes of operation. Description of the experimental setup is given. A simplified analysis of the pulsed mode of operation is presented. The heart of the study is concerned with measuring parameters critical to pulsed mode performance. The effects of temperature, readout voltage level, integration time, and device configuration on sensor operation are depicted. Increased leakage with temperature is found to change the proportionality constant between output and integration time. Both the saturation level and the dark response show a direct dependence on readout voltage. Varying the frame time (i.e., the integration time) is shown to be equivalent to changing the aperture setting of the optical system used to focus images onto the sensor. The relation between the steady-state photocurrent and the pulsed mode output has been established and is in agreement with analyses of the integration mode. The effects of collector pulse amplitude and temperature were found to match the relations derived from an extended analysis. An integration rate is extrapolated from the data. Images produced by a mechanically scanned line sensor and an area array are shown.