Detector Chip Research Articles

Heat release in the cryogenic system of a superconducting integrated detector and the influence of heat on its operation

Heat release in the cryogenic system of a subterahertz-range superconducting integrated detector at ≈4.2 K is studied, and the influence of the released heat on its main characteristics is estimated. The detector chip mounted on a silicon lens is connected to a bias board by aluminum wires 25 μm in diameter, which are fixed by ultrasonic bonding. They are necessary for setting a bias current through the working components of the detector and represent an integral part of the system. The contact resistance between the wires and contact pads of the microchip is measured. The contact resistance is found to considerably exceed the resistance of the aluminum wire and, hence, makes a major contribution to heat release in the system. A “multipoint contact with one wire” technique is suggested. Tests show its efficiency: the contact resistance decreases considerably compared with the standard approach.

DEPFET Macropixel Detectors for MIXS: Integration and Qualification of the Flight Detectors

The Mercury imaging X-ray spectrometer (MIXS) on board of ESA's fifth cornerstone mission BepiColombo will be the first space instrument using DEpleted P-channel FET (DEPFET) based detectors. The MIXS spectrometer comprises two channels with identical focal plane detectors and is dedicated to energy resolved imaging of X-ray fluorescence from the mercurial surface. We report on the characterization, integration, and spectroscopic qualification of MIXS flight detectors. Detector chips were precharacterized at die level in order to select the best dies for integration and to do homogeneity and yield studies. Then, the detector chips were integrated to MIXS Detector Plane Arrays (DPAs), a complicated process due to the sophisticated mechanical structure, which allows the thermal decoupling of the detector from its readout and control chips. After integration, spectroscopic qualification measurements were done in order to analyze the detector performance and to prove the excellent spectroscopic performance of the DEPFET Macropixel detectors over a wide temperature range. The integration and spectroscopic qualification of all flight grade modules is now successfully completed.

Ultra Small Integrated Optical Fiber Sensing System

This paper introduces a revolutionary way to interrogate optical fiber sensors based on fiber Bragg gratings (FBGs) and to integrate the necessary driving optoelectronic components with the sensor elements. Low-cost optoelectronic chips are used to interrogate the optical fibers, creating a portable dynamic sensing system as an alternative for the traditionally bulky and expensive fiber sensor interrogation units. The possibility to embed these laser and detector chips is demonstrated resulting in an ultra thin flexible optoelectronic package of only 40 μm, provided with an integrated planar fiber pigtail. The result is a fully embedded flexible sensing system with a thickness of only 1 mm, based on a single Vertical-Cavity Surface-Emitting Laser (VCSEL), fiber sensor and photodetector chip. Temperature, strain and electrodynamic shaking tests have been performed on our system, not limited to static read-out measurements but dynamically reconstructing full spectral information datasets.

Prokaryotic communities and operating metabolisms in the surface and the permafrost of Deception Island (Antarctica)

In this study we examined the microbial community composition and operating metabolisms on the surface and in the permafrost of Deception Island, (Antarctica) with an on site antibody microarray biosensor. Samples (down to a depth of 4.2 m) were analysed with LDChip300 (Life Detector Chip), an immunosensor containing more than 300 antibodies targeted to bacterial and archaeal antigens. The immunograms showed positive antigen-antibody reactions in all surface samples (lichens, pyroclasts) and the top layer of the permafrost. The results indicated the presence of exopolysaccharides, bacteria belonging to the Alpha-, Delta- and Gammaproteobacteria, Bacteroidetes, Gram-positive Actinobacteria and Firmicutes, as well as archaeal species, most probably Methanobacterium spp. Positive reactions with antibodies to proteins and peptides revealed the presence of nitrogen fixation (NifHD, GlnB, HscA), methanogenic (McrB), iron homeostasis and iron scavenging (ferritins and DPS proteins) proteins, as well as ABC transporters, which indicated that these processes were operating at the time of sampling. These results were validated with other molecular ecology techniques such as oligonucleotide microarrays, 16S bacterial rRNA gene sequence analysis, aerobic viable counts and microscopy. Molecular ecology results showed a differentiated pattern along the depth of the drill, being the top active layer the most diverse, with Acidobacteria, Actinobacteria, Proteobacteria, Bacteroidetes and the phototrophs Cyanobacteria and Chloroflexi as dominant groups. Actinobacteria and Firmicutes were dominant in depths from 0.5 to 2 m, and Betaproteobacteria from 3 to 4.2 m. The geochemical analysis revealed the presence of low molecular weight organic acids (acetate, formate) which could be used by microorganisms as energy sources for sulfate, nitrate and metal reduction under anaerobic conditions.

The search for life on Earth and other planets

As the NASA rover Curiosity approaches Mars on its quest to look for signs of past or present life there and sophisticated instruments like the space telescopes Kepler and CoRoT keep discovering additional, more Earth-like planets orbiting distant stars, science faces the question of how to spot life on other planets. Even here on Earth biotopes remain to be discovered and explored.

60-GHz Millimeter-Wave Life Detection System (MLDS) for Noncontact Human Vital-Signal Monitoring

A first reported experimental study of a 60 GHz millimeter-wave life detection system (MLDS) for noncontact human vital-signal monitoring is presented. This detection system is constructed by using V-band millimeter-wave waveguide components. A clutter canceller is implemented in the system with an adjustable attenuator and phase shifter. It performs clutter cancellation for the transmitting power leakage from the circulator and background reflection to enhance the detecting sensitivity of weak vital signals. The noncontact vital signal measurements have been conducted on a human subject in four different physical orientations from distances of 1 and 2 m. The time-domain and spectrum waveforms of the measured breathing and heartbeat are presented. This prototype system will be useful for the development of the 60-GHz CMOS MLDS detector chip design.

Optimization of the spectroscopic response of the Timepix detector

The Time over Threshold (TOT) mode of the hybrid semiconductor pixel detector Timepix allows for the direct measurement of the deposited energy in each pixel. Combined with its high spatial resolution the Timepix detector is thus well suited for measurements where the precise position and energy information are required. The energy measurement with the pixel detector is however not easy and the results are degraded by the charge sharing effect. The different electronic response of each pixel requires an energy calibration. Moreover the wide dynamic range (in energy from keV to MeV) which can be registered in each pixel in different applications puts high demands on the analog circuits of the detector chip. The characteristics of the analog circuit of the Timepix are controlled and can be adjusted by a set of detector parameters. The systematic response of the detector with respect to the large number of parameters was not investigated before. In this contribution we present the characterization and optimization of the spectroscopic performance of the Timepix detector by changing and fine tuning the settings of detector parameters using newly developed evaluation method.

A microbial oasis in the hypersaline Atacama subsurface discovered by a life detector chip: implications for the search for life on Mars.

The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5 m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2 m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5 g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260 g kg(-1)) and perchlorate (41.13 μg g(-1) maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14 μg g(-1)) or formate (76.06 μg g(-1)) as electron donors, and sulfate (15875 μg g(-1)), nitrate (13490 μg g(-1)), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.

Influence of electromagnetic interference on the analog part of hybrid Pixel detectors

The analog signal from the sensor of hybrid semiconductor pixel detectors is prone to electro-magnetic interference. The study and diagnosis of induced and common electro-magnetic coupling between the analog part and digital part of these devices is required. The influence of electro-magnetic interference was tested on the setup with a pixel detector Timepix or Medipix and a FITPix read-out interface. Measurements were carried out of external as well as internal interference. We evaluated the influence of both sources of electro-magnetic interference to the noise recorded by pixels. We measured the local spatial intensity distribution and frequency spectrum of the electro-magnetic field originating inside the readout chip during its own operation. In context of this test we exposed the detector chip to a locally generated artificial electro-magnetic field evaluating its sensitivity to induced interference. Consequently, the whole setup of the detector and read-out interface was exposed to a distant source of electro-magnetic radiation, during which we tested efficiency of the electro-magnetic shielding of various arrangements. Further, tests measured the coupling over power supply lines. In particular, the noise generated by the operation of the detector itself was determined. In addition, the detector sensitivity to deliberately induced noise was evaluated. By means of these tests weak points of the setup sensitive to the intrusion of electro-magnetic interference are revealed. When locations of susceptible places are identified proper methods can be applied to increase immunity of the detector setup against the electro-magnetic interference. Experiences gained are planned to be used in development of the EMI shielded version of the FITPIX interface shielded to electro-magnetic interference.

TSV processing of Medipix3 wafers by CEA-LETI: a progress report

The next generation of hybrid pixel detectors in particle physics experiments require reduced material budget, increased interconnection density and, ideally, they should be tileable to cover large areas seamlessly. These criteria cannot be fulfilled with present day interconnection techniques. As a result the particle physics community has recently put in a lot of effort to investigate and evaluate a variety of novel interconnection technologies.This paper focuses on describing a recently launched Through Silicon Via process development project with CEA-LETI. The project aims to use Medipix3 wafers and an existing ``via last'' TSV process made available by CEA-LETI to demonstrate the feasibility of TSVs on functional detector chips. The status of the project, TSV design and future plans are presented.

AlGaN-on-Si-Based 10-$\mu\hbox{m}$ Pixel-to-Pixel Pitch Hybrid Imagers for the EUV Range

We report on the fabrication of extreme ultraviolet (EUV) hybrid imagers with backside-illuminated detector chip based on aluminum gallium nitride (AlGaN) layers grown on silicon and integrated with CMOS readout chip. The focal plane array (FPA) size is 256 × 256 pixels with 10-μm pixel-to-pixel pitch. The devices were characterized at wavelengths from 300 down to 1 nm using synchrotron radiation. An upper cutoff wavelength of 280 nm was observed, as expected from the AlGaN active layer composition (40% Al). Thus, the imagers have a high rejection ratio of the near UV and visible radiation. Moreover, no degradation due to proton irradiation was observed for 60-MeV energy and 5 ·1010 protons/cm2 dose. Furthermore, devices with thin silicon substrate layer that is intentionally left were fabricated, and response only in the EUV range was observed. These results demonstrate the possibility of achieving high-resolution EUV imaging with AlGaN-based FPAs, which is very promising for high-end industrial, scientific, and space applications.

Characterization of CdTe X-Ray Sensor Layer on Medipix Detector Chips

We have been characterizing various sensor layers bump-bonded to Medipix detector chips. We report here characterizationthe leakage current variations of a cadmium telluride (CdTe) assembled-Medipix2 assemblyat different temperatures.Medipix detectors are being used in small animal computed tomography (CT) scanner systems known as MARS-CT. The spectroscopic imaging of a mouse and human atheroma using this system has previously been reported [1-2]. In those reports, Medipix2 detectors were used with Si and GaAs sensor layers, respectively. Cadmium telluride (CdTe) is expected to be a useful sensor layer for clinical CT imaging detectors because of its good detection efficiency for x-rays in the energy range up to 120 keV. However, Aan understanding of the detection characteristics of these sensor layers is vital to high-quality imaging. This work presents the results of inhomogeneities within the CdTe sensor, temperature variations and wrinkle pattern instability.We present leakage current variations with temperature and sensitivity inhomogeneity across the detector. This is an extension of the tests previously reported in Aamir R et al [1][3].

ASIC Implementation of Soft-Input Soft-Output MIMO Detection Using MMSE Parallel Interference Cancellation

Multiple-input multiple-output (MIMO) technology is the key to meet the demands for data rate and link reliability of modern wireless communication systems, such as IEEE 802.11n or 3GPP-LTE. The full potential of MIMO systems can, however, only be achieved by means iterative MIMO decoding relying on soft-input soft-output (SISO) data detection. In this paper, we describe the first ASIC implementation of a SISO detector for iterative MIMO decoding. To this end, we propose a low-complexity minimum mean-squared error (MMSE) based parallel interference cancellation algorithm, develop a suitable VLSI architecture, and present a corresponding four-stream 1.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> detector chip in 90 nm CMOS technology. The fabricated ASIC includes all necessary preprocessing circuitry and exceeds the 600 Mb/s peak data-rate of IEEE 802.11n. A comparison with state-of-the-art MIMO-detector implementations demonstrates the performance benefits of our ASIC prototype in practical system-scenarios.

Quantification of Various Factors Influencing the Precision of Thermoluminescent Detector Calibrations for New and Used Chip Sets

Factors affecting the random and systematic error in calibrating three sets of 100 LiF:Mg,Ti thermoluminescent detector chips were investigated. The chips were held in a polymethyl methacrylate plate with 0.3 cm deep wells covered with a thin top plate, affixed to a polymethyl methacrylate phantom 150 cm from a 3.2 × 10(10) GBq 137Cs source, used to irradiate the chips to 4.52 mGy. Three sets of chips were used: one new, one heavily used, and one having relatively high degrees of visible physical damage. Variations in the exposure rate across the plate were measured with an ion chamber. Experimental drift was judged by performing successive calibrations on subsequent days, while always reading the chips in the same order. The chips were subject to manual examination to determine variations in mass and physical quality. This study indicates that more accurate calibrations can be obtained by accounting for the error caused by nonuniformity in the delivered dose, which was in this study as high as 4.4% from the center to the edges of the target. Making use of more than three calibrations only reduces the standard deviation as a percentage of the mean of a set by less than 1%. Desirable dosimeters in commercially rejected sets were identified by comparing each dosimeter's standard deviation of response across all calibrations to a commercially acceptable control set. Up to 50% variations in mass and visual quality, including opacity, fracture, and surface scratches to chips, showed little to no correlation with their response.

IR Microspectrometers based on Linear-Variable Optical Filters

This paper presents the design, fabrication and characterization of Infra-Red (IR) Linear Variable Optical Filter (LVOF)-based micro-spectrometers. Two LVOF microspectrometer designs have been realized: one for operating in the 1400nm to 2500nm wavelength range and another between 3000nm and 5000nm. The IR LVOFs have been fabricated in an IC-Compatible process using resist reflow. The LVOF provides the possibility to have a small size, robust and high-resolution micro-spectrometer in the IR on a detector chip. Such IR microspectrometers can be fabricated at low-cost in high volume production and have huge potential in applications such as liquid identification (e.g. water in alcohol, water in oil) and gas sensing.

Classification of Modern and Old Río Tinto Sedimentary Deposits Through the Biomolecular Record Using a Life Marker Biochip: Implications for Detecting Life on Mars

The particular mineralogy formed in the acidic conditions of the Río Tinto has proven to be a first-order analogue for the acid-sulfate aqueous environments of Mars. Therefore, studies about the formation and preservation of biosignatures in the Río Tinto will provide insights into equivalent processes on Mars. We characterized the biomolecular patterns recorded in samples of modern and old fluvial sediments along a segment of the river by means of an antibody microarray containing more than 200 antibodies (LDCHIP200, for Life Detector Chip) against whole microorganisms, universal biomolecules, or environmental extracts. Samples containing 0.3-0.5 g of solid material were automatically analyzed in situ by the Signs Of LIfe Detector instrument (SOLID2), and the results were corroborated by extensive analysis in the laboratory. Positive antigen-antibody reactions indicated the presence of microbial strains or high-molecular-weight biopolymers that originated from them. The LDCHIP200 results were quantified and subjected to a multivariate analysis for immunoprofiling. We associated similar immunopatterns, and biomolecular markers, to samples with similar sedimentary age. Phyllosilicate-rich samples from modern fluvial sediments gave strong positive reactions with antibodies against bacteria of the genus Acidithiobacillus and against biochemical extracts from Río Tinto sediments and biofilms. These samples contained high amounts of sugars (mostly polysaccharides) with monosaccharides like glucose, rhamnose, fucose, and so on. By contrast, the older deposits, which are a mix of clastic sands and evaporites, showed only a few positives with LDCHIP200, consistent with lower protein and sugar content. We conclude that LDCHIP200 results can establish a correlation between microenvironments, diagenetic stages, and age with the biomarker profile associated with a sample. Our results would help in the search for putative martian biomarkers in acidic deposits with similar diagenetic maturity. Our LDCHIP200 and SOLID-like instruments may be excellent tools for the search for molecular biomarkers on Mars or other planets.

Direct growth of CdTe thick films on the Medipix2 pixel detector chip

Polycrystalline CdTe layers were directly deposited on the Medipix2 readout chip by physical vapor deposition using a Riber molecular beam epitaxy 2300. Sb2Te3 was evaporated as backside contact material, resulting in an M-π-p diode structure comprising the pixel contact material, the intentionally undoped CdTe, and Sb2Te3. It was possible to achieve x-ray images at 60 kVp. In addition, thermally oxidized Si wafers were coated with a comparable M-π-p structure grown under identical conditions, to investigate electrical properties of the films. The specific resistance of the layers was found to be 3.85×108 Ω cm.

The first beam test of a monolithic particle pixel detector in high-voltage CMOS technology

The results of beam- and irradiation tests preformed on a monolithic particle pixel detector in high-voltage CMOS technology will be presented for the first time. All tested detectors are implemented in a 0.35 μ m technology, they utilize high-voltage n-well/p-substrate diodes as pixel sensors and rely on charge drift in diode depletion layers as the main signal generating mechanism. The detector prototype tested in the beam is a system on a chip that contains a 128×128 matrix with 21 × 21 μ m 2 large pixels, source-follower based- rolling shutter readout and on-chip ADCs that digitize the signal amplitudes with 8-bit precision. Test beam measurements have been performed using EUDET infrastructure. The measured MIP cluster signals are typically 2200 e, spatial resolution approximately 7 μ m (RMS), signal-to-noise ratio of a single pixel is 12.3 and detection efficiency more than 85%. To test the radiation tolerance, several detector chips have been irradiated with neutrons up to 10 14 n eq/cm 2 and with X-rays up to 500 kGy (50 Mrad), they are still functional and the experimental results obtained with these chips will be presented as well.

Development and evaluation of semi-insulating GaAs detectors in hot plasmas diagnostics

This work deals with the evaluation of semi-insulating (SI) GaAs radiation detector applicable in the spectrometry of “soft” X-rays (1–20 keV) emitted by hot plasmas and evaluation of its performance. SI GaAs detector with thin base and sandwich electrodes configuration was fabricated. The detector chip was mounted onto common support together with the input external JFET and feedback elements and cooled down to 255 K by Peltier cooler. The first JFET stage was connected to the PR307SF hybrid charge-sensitive preamplifier. The shaping amplifier was assembled from the set of CREMAT hybrid circuits allowing variation of the shaping time (0.25–8.0 μs). The detector performance was evaluated by the measurement of the 241Am pulse-height spectra. Observed results are demonstrated and discussed.

SU-EE-A4-03: Real Time Imaging of the Stopping Distribution for Antiprotons in Biological Targets

Purpose: To keep the normal tissue complication probability (NTCP) as low as possible, real-time imaging of the irradiation process is highly desirable to detect and correct any deviation from the treatment plan. Using a simple detector setup, the one-dimensional annihilation vertex distribution was reconstructed by evaluating the tracks of charged pions resulting from antiproton annihilation in a water phantom.Methods and materials: A spare ladder of 10 silicon pixel detector chips, normally used as part of the vertex detector in the ALICE experiment at CERN, was used. Each chip has 256 × 320 pixels with 50 μm width and 425 μm height, and a thickness of 200 μm. It was mounted unconventionally, allowing charged particles, especially pions, to traverse it more or less tangentially to the front surface, depending on their place of generation. By interacting with a line of pixels, they leave tracks with a specific length and slope, which are used to back-calculate their origin. FLUKA 2008.3c.0 was used to simulate this set-up and to generate Monte Carlo data to improve the understanding and analysis of real events collected during a run with 500 MeV/c antiprotons at the antiproton decelerator facility at CERN. Results: Reconstruction of the annihilation vertex was achieved with a resolution of 4 cm in the axial direction, limited by the present detector mounting. Based on Monte Carlo simulations, alternative detector orientations and optimized detector geometries are proposed. Conclusion: The principal applicability of the described method was demonstrated. Further investigation needs to be done to improve on the resolution. Rotating the detector by 90 degrees seems beneficial, but might introduce too much material so that the pions interact significantly, disabling a track reconstruction.