A 3-step Low-latency Low-Power Multichannel Time-to-Digital Converter based on Time Residual Amplifier

This paper proposes and evaluates a novel architecture for a low-power Time-to-Digital Converter with high resolution, optimized for both integration in multichannel chips and high rate operation (40 Mconversion/s/channel). This converter is based on a three-step architecture. The first step uses a counter whereas the following ones are based on two kinds of Delay Line structures. A programmable time amplifier is used between the second and third steps to reach the final resolution of 24.4 ps in the standard mode of operation. The system makes use of common continuously stabilized master blocks that control trimmable slave blocks, in each channel, against the effects of global PVT variations. Thanks to this structure, the power consumption of a channel is considerably reduced when it does not process a hit, and limited to 2.2 mW when it processes a hit. In the 130 nm CMOS technology used for the prototype, the area of a TDC channel is only 0.051 mm2. This compactness combined with low power consumption is a key advantage for integration in multi-channel front-end chips. The performance of this new structure has been evaluated on prototype chips. Measurements show excellent timing performance over a wide range of operating temperatures (-40{\deg}C to 60{\deg}C) in agreement with our expectations. For example, the measured timing integral nonlinearity is better than 1 LSB (25 ps) and the overall timing precision is better than 21 ps RMS

Design considerations for a new generation of SiPMs with unprecedented timing resolution

The potential of photon detectors to achieve precise timing information is of increasing importance in many domains, PET and CT scanners in medical imaging and particle physics detectors, amongst others. The goal to increase by an order of magnitude the sensitivity of PET scanners and to deliver, via time-of-flight (TOF), true space points for each event, as well as the constraints set by future particle accelerators require a further leap in time resolution of scintillator-based ionizing radiation detectors, reaching eventually a few picoseconds resolution for sub MeV energy deposits. In spite of the impressive progress made in the last decade by several manufacturers, the Single Photon Time Resolution (SPTR) of SiPMs is still in the range of 70-120ps FWHM, whereas a value of 10ps or even less would be desirable. Such a step requires a break with traditional methods and the development of novel technologies. The possibility of combining the extraordinary potential of nanophotonics with new approaches offered by modern microelectronics and 3D electronic integration opens novel perspectives for the development of a new generation of metamaterial-based SiPMs with unprecedented photodetection efficiency and timing resolution.Comment: 16 pages, 6 figures, submitted to JINS

A portable device for time-resolved fluorescence based on an array of CMOS SPADs with integrated microfluidics

[eng] Traditionally, molecular analysis is performed in laboratories equipped with desktop instruments operated by specialized technicians. This paradigm has been changing in recent decades, as biosensor technology has become as accurate as desktop instruments, providing results in much shorter periods and miniaturizing the instrumentation, moving the diagnostic tests gradually out of the central laboratory. However, despite the inherent advantages of time-resolved fluorescence spectroscopy applied to molecular diagnosis, it is only in the last decade that POC (Point Of Care) devices have begun to be developed based on the detection of fluorescence, due to the challenge of developing high-performance, portable and low-cost spectroscopic sensors. This thesis presents the development of a compact, robust and low-cost system for molecular diagnosis based on time-resolved fluorescence spectroscopy, which serves as a general-purpose platform for the optical detection of a variety of biomarkers, bridging the gap between the laboratory and the POC of the fluorescence lifetime based bioassays. In particular, two systems with different levels of integration have been developed that combine a one-dimensional array of SPAD (Single-Photon Avalanch Diode) pixels capable of detecting a single photon, with an interchangeable microfluidic cartridge used to insert the sample and a laser diode Pulsed low-cost UV as a source of excitation. The contact-oriented design of the binomial formed by the sensor and the microfluidic, together with the timed operation of the sensors, makes it possible to dispense with the use of lenses and filters. In turn, custom packaging of the sensor chip allows the microfluidic cartridge to be positioned directly on the sensor array without any alignment procedure. Both systems have been validated, determining the decomposition time of quantum dots in 20 nl of solution for different concentrations, emulating a molecular test in a POC device.[cat] Tradicionalment, l'anàlisi molecular es realitza en laboratoris equipats amb instruments de sobretaula operats per tècnics especialitzats. Aquest paradigma ha anat canviant en les últimes dècades, a mesura que la tecnologia de biosensor s'ha tornat tan precisa com els instruments de sobretaula, proporcionant resultats en períodes molt més curts de temps i miniaturitzant la instrumentació, permetent així, traslladar gradualment les proves de diagnòstic fora de laboratori central. No obstant això i malgrat els avantatges inherents de l'espectroscòpia de fluorescència resolta en el temps aplicada a la diagnosi molecular, no ha estat fins a l'última dècada que s'han començat a desenvolupar dispositius POC (Point Of Care) basats en la detecció de la fluorescència, degut al desafiament que suposa el desenvolupament de sensors espectroscòpics d'alt rendiment, portàtils i de baix cost. Aquesta tesi presenta el desenvolupament d'un sistema compacte, robust i de baix cost per al diagnòstic molecular basat en l'espectroscòpia de fluorescència resolta en el temps, que serveixi com a plataforma d'ús general per a la detecció òptica d'una varietat de biomarcadors, tancant la bretxa entre el laboratori i el POC dels bioassaigs basats en l'anàlisi de la pèrdua de la fluorescència. En particular, s'han desenvolupat dos sistemes amb diferents nivells d'integració que combinen una matriu unidimensional de píxels SPAD (Single-Photon Avalanch Diode) capaços de detectar un sol fotó, amb un cartutx microfluídic intercanviable emprat per inserir la mostra, així com un díode làser UV premut de baix cost com a font d'excitació. El disseny orientat a la detecció per contacte de l'binomi format pel sensor i la microfluídica, juntament amb l'operació temporitzada dels sensors, permet prescindir de l'ús de lents i filtres. Al seu torn, l'empaquetat a mida de l'xip sensor permet posicionar el cartutx microfluídic directament sobre la matriu de sensors sense cap procediment d'alineament. Tots dos sistemes han estat validats determinant el temps de descomposició de "quantum dots" en 20 nl de solució per a diferents concentracions, emulant així un assaig molecular en un dispositiu POC

A Low-Power Silicon-Photomultiplier Readout ASIC for the CALICE Analog Hadronic Calorimeter

The future e + e − collider experiments, such as the international linear collider, provide precise measurements of the heavy bosons and serve as excellent tests of the underlying fundamental physics. To reconstruct these bosons with an unprecedented resolution from their multi-jet final states, a detector system employing the particle flow approach has been proposed, requesting calorimeters with imaging capabilities. The analog hadron calorimeter based on the SiPM-on-tile technology is one of the highly granular candidates of the imaging calorimeters. To achieve the compactness, the silicon-photomultiplier (SiPM) readout electronics require a low-power monolithic solution. This thesis presents the design of such an application-specific integrated circuit (ASIC) for the charge and timing readout of the SiPMs. The ASIC provides precise charge measurement over a large dynamic range with auto-triggering and local zero-suppression functionalities. The charge and timing information are digitized using channel-wise analog-to-digital and time-to-digital converters, providing a fully integrated solution for the SiPM readout. Dedicated to the analog hadron calorimeter, the power-pulsing technique is applied to the full chip to meet the stringent power consumption requirement. This work also initializes the commissioning of the calorimeter layer with the use of the designed ASIC. An automatic calibration procedure has been developed to optimized the configuration settings for the chip. The new calorimeter base unit with the designed ASIC has been produced and its functionality has been tested

Challenges and Solutions to Next-Generation Single-Photon Imagers

Detecting and counting single photons is useful in an increasingly large number of applications. Most applications require large formats, approaching and even far exceeding 1 megapixel. In this thesis, we look at the challenges of massively parallel photon-counting cameras from all performance angles. The thesis deals with a number of performance issues that emerge when the number of pixels exceeds about 1/4 of megapixels, proposing characterization techniques and solutions to mitigate performance degradation and non-uniformity. Two cameras were created to validate the proposed techniques. The first camera, SwissSPAD, comprises an array of 512 x 128 SPAD pixels, each with a one-bit memory and a gating mechanism to achieve 5ns high precision time windows with high uniformity across the array. With a massively parallel readout of over 10 Gigabit/s and positioning of the integration time window accurate to the pico-second range, fluorescence lifetime imaging and fluorescence correlation spectroscopy imaging achieve a speedup of several orders of magnitude while ensuring high precision in the measurements. Other possible applications include wide-field time-of-flight imaging and the generation of quantum random numbers at highest bit-rates. Lately super-resolution microscopy techniques have also used SwissSPAD. The second camera, LinoSPAD, takes the concepts of SwissSPAD one step further by moving even more 'intelligence' to the FPGA and reducing the sensor complexity to the bare minimum. This allows focusing the optimization of the sensor on the most important metrics of photon efficiency and fill factor. As such, the sensor consists of one line of SPADs that have a direct connection each to the FPGA where complex photon processing algorithms can be implemented. As a demonstration of the capabilities of current lowcost FPGAs we implemented an array of time-to-digital converters that can handle up to 8.5 billion photons per second, measuring each one of them and accounting them in high precision histograms. Using simple laser diodes and a circuit to generate light pulses in the picosecond range, we demonstrate a ubiquitous 3D time-of-flight sensor. The thesis intends to be a first step towards achieving the world's first megapixel SPAD camera, which, we believe, is in grasp thanks to the architectural and circuital techniques proposed in this thesis. In addition, we believe that the applications proposed in this thesis offer a wide variety of uses of the sensors presented in this thesis and in future ones to come

Beam halo and bunch purity monitoring

Beam halo measurements imply measurements of beam profiles with a very high dynamic range; in transverse and also longitudinal planes. This lesson gives an overview of high dynamic range instruments for beam halo measurements. In addition halo definitions and quantifications in view of beam instrumentation are discussed.Comment: 29 pages, contribution to the CAS - CERN Accelerator School: Beam Instrumentation, 2-15 June 2018, Tuusula, Finland. arXiv admin note: text overlap with arXiv:1303.676

Spectrally and temporally resolved single photon counting in advanced biophotonics applications

Biomedicine requires highly sensitive and efficient light sensors to analyse light-tissue or light-sample interactions. Single-photon avalanche diode (SPAD) sensors implemented with complementary metal-oxide-semiconductor (CMOS) technology have a growing range of applications in this field. Single-photon detection coupled with integrated timing circuits enables us to timestamp each detected photon with high temporal resolution (down to picoseconds). Arrays of SPAD based pixels and CMOS technology offer massively parallel time-resolved single-photon counting for spectrally and temporally resolved analysis of various light phenomena.This thesis examines how time-resolved CMOS SPAD based line sensors with per pixel timing circuits can be utilized to advance biophotonic applications. The study focuses on improving the existing techniques of fluorescence and Raman spectroscopy, and demonstrates for the first time CMOS SPAD based detection in optical coherence tomography (OCT). A novel detection scheme is proposed combining low-coherence interferometry and time-resolved photon counting. In this approach the interferometric information is revealed from spectral intensity measurements, which is supplemented by time-stamping of the photons building up the spectra.Two CMOS SPAD line sensors (Ra-I and its improved version, Ra-II) were characterized and the effect of their parameters on the selected techniques was analysed. The thesis demonstrates the deployment of the Ra-I line sensor in time-resolved fluorescence spectroscopy with indications of the applicability in time-resolved Raman spectroscopy. The work includes integration of the sensor with surrounding electrical and optical systems, and the implementation of firmware and software for controlling the optical setup. As a result, a versatile platform is demonstrated capable of micro- and millisecond sampling of spectral fluorescence lifetime changes in a single transient of fast chemical reactions.OCT operating in the spectral domain traditionally uses CMOS photodiode and charge-coupled device (CCD) based detectors. The applicability of CMOS SPAD sensors is investigated for the first time with focus on the main limitations and related challenges. Finally, a new detection method is proposed relying on both the wave and particle nature of light, recording time-resolved interferometric spectra from a Michelson interferometer. This method offers an alternative approach to analyse luminous effects and improves techniques based on the light’s time of flight. As an example, a proof of concept study is presented for the removal of unwanted reflections from along the sample and the optical path in an OCT setup

Development of a spatially dispersed short-coherence interferometry sensor using diffraction grating orders

Modern manufacturing processes can achieve good throughput by requiring that manufactured products be screened by better quality control exercised at a quicker rate. This trend in the quality control of manufactured products increases the need for process-oriented precision metrology capable of performing faster inspections and yielding valuable feedback to the manufacturing system. This paper presents a spatially dispersed short-coherence interferometry sensor using diffraction orders of the zeroth and first order for a diffraction grating introduced as a new compact system configuration for surface profile measurement. In this modified design, the diffraction grating acts as the beam splitter/combiner. Diffractions for the zeroth and first orders are represented by the reference and measurement arms, respectively, of a Michelson interferometer, which reduces the optical path length. This innovative design has been proven effective for determining the step-height repeatability in the sensor range from 27 nm to 22 nm for profiles spanning the step heights of the tested specimens