Ps Time Resolution Research Articles

Targeted transfer of self-assembled CdSe nanoplatelet film onto WS2 flakes to construct hybrid heterostructures

Colloidal CdSe nanoplatelets are thin semiconductor materials with atomic flatness surfaces and one-dimensional strong quantum confinement, and hence they own very narrow and anisotropic emission. Here, we present a polydimethylsiloxane (PDMS) assisted transferring method that can pick up single layer CdSe nanoplatelet films self-assembled on a liquid surface and then precisely transfer to a target. By layer-by-layer picking up and transferring, multiple layers of CdSe films can be built up to form CdSe stacks with each single layer having dominant in-plane transition dipole distribution, which both material and energic structures are analogous to traditional multiple quantum wells grown by molecular-beam epitaxy. Additionally, with the great flexibility of colloidal nanoplatelets and this transferring method, CdSe nanoplatelets films can be combined with other materials to form hybrid heterostructures. We transferred a single-layer CdSe film onto WS2 flakes, and precisely studied the fast energy transfer rate with controlled CdSe nanoplatelet orientation and by using a streak camera with a ps time resolution.

MATRIX16: A 16-Channel Low-Power TDC ASIC with 8 ps Time Resolution

This paper presents a highly configurable 16-channel TDC ASIC designed in a commercial 180 nm technology with the following features: time-of-flight and time-over-threshold measurements, 8.6 ps LSB, 7.7 ps jitter, 5.6 ps linearity error, up to 5 MHz of sustained input rate per channel, 9.1 mW of power consumption per channel, and an area of 4.57 mm2. The main contributions of this work are the novel design of the clock interpolation circuitry based on a resistive interpolation mesh circuit and the capability to operate at different supply voltages and operating frequencies, thus providing a compromise between TDC resolution and power consumption.

A ring-oscillator based multi-mode time-to-digital converter on Xilinx Kintex-7 FPGA

Taking the system clock as the reference, a ring-oscillator based Vernier-type time stamping method is proposed for the implementation of time-to-digital converters (TDCs) on field programmable gate array (FPGA). A module with this method called time-marker is implemented on a Xilinx Kintex-7 FPGA and tested with 43 ps time resolution and less than 50 ns measurement dead time. To illustrate this time-marker can be used as the building block for TDC construction to provide high time measurement performance with low resource consumption, a multi-mode TDC using eight time-markers is implemented with performance evaluation. The TDC has three flexible configuration modes for performance enhancements in three aspects. In the multi-channel mode, it becomes eight independent TDC channels with average 34 ps time interval RMS precision and 50 ns measurement dead time; in the high-precision mode, it is one TDC channel with 14 ps RMS precision and 50 ns measurement dead time; and in the high-throughput mode, it is one TDC channel with 33 ps RMS precision and 6.25 ns measurement dead time. In addition, the temperature dependence of the performance is evaluated.

A time-of-flight-based reconstruction for real-time prompt-gamma imaging in proton therapy

We propose a novel prompt-gamma (PG) imaging modality for real-time monitoring in proton therapy: PG time imaging (PGTI). By measuring the time-of-flight (TOF) between a beam monitor and a PG detector, our goal is to reconstruct the PG vertex distribution in 3D. In this paper, a dedicated, non-iterative reconstruction strategy is proposed (PGTI reconstruction). Here, it was resolved under a 1D approximation to measure a proton range shift along the beam direction. In order to show the potential of PGTI in the transverse plane, a second method, based on the calculation of the centre of gravity (COG) of the TIARA pixel detectors’ counts was also explored. The feasibility of PGTI was evaluated in two different scenarios. Under the assumption of a 100 ps (rms) time resolution (achievable in single proton regime), MC simulations showed that a millimetric proton range shift is detectable at 2σ with 108 incident protons in simplified simulation settings. With the same proton statistics, a potential 2 mm sensitivity (at 2σ with 108 incident protons) to beam displacements in the transverse plane was found using the COG method. This level of precision would allow to act in real-time if the treatment does not conform to the treatment plan. A worst case scenario of a 1 ns (rms) TOF resolution was also considered to demonstrate that a degraded timing information can be compensated by increasing the acquisition statistics: in this case, a 2 mm range shift would be detectable at 2σ with 109 incident protons. By showing the feasibility of a time-based algorithm for the reconstruction of the PG vertex distribution for a simplified anatomy, this work poses a theoretical basis for the future development of a PG imaging detector based on the measurement of particle TOF.

Time-resolved spectral-domain optical coherence tomography with CMOS SPAD sensors.

We present a first spectral-domain optical coherence tomography (SD-OCT) system deploying a complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode (SPAD) based, time-resolved line sensor. The sensor with 1024 pixels achieves a sensitivity of 87 dB at an A-scan rate of 1 kHz using a supercontinuum laser source with a repetition rate of 20 MHz, 38 nm bandwidth, and 2 mW power at 850 nm centre wavelength. In the time-resolved mode of the sensor, the system combines low-coherence interferometry (LCI) and massively parallel time-resolved single-photon counting to control the detection of interference spectra on the single-photon level based on the time-of-arrival of photons. For proof of concept demonstration of the combined detection scheme we show the acquisition of time-resolved interference spectra and the reconstruction of OCT images from selected time bins. Then, we exemplify the temporal discrimination feature with 50 ps time resolution and 249 ps timing uncertainty by removing unwanted reflections from along the optical path at a 30 mm distance from the sample. The current limitations of the proposed technique in terms of sensor parameters are analysed and potential improvements are identified for advanced photonic applications.

Picosecond timing resolution measurements of low gain avalanche detectors with a 120 GeV proton beam for the TOPSiDE detector concept

This paper presents results that take a critical step toward proving 10 ps timing resolution's feasibility for particle identification in the TOPSiDE detector concept for the Electron-Ion Collider. Measurements of LGADs with a thickness of 35 μm and 50 μm are evaluated with a 120 GeV proton beam. The performance of the gain and timing response is assessed, including the dependence on the reverse bias voltage and operating temperature. The best timing resolution of UFSDs in a test beam to date is achieved using three combined planes of 35 μm thick LGADs at -30°C with a precision of 14.3 ± 1.5 ps.

The High-Rate Sealed MRPC to Promote Pollutant Exchange in Gas Gaps: Status on the Development and Observations

This work reports the latest observations on the behavior of two Multigap Resistive Plate Chambers (MRPC) under wide high-luminosity exposures, which motivate the development and in-beam test of the sealed MRPC prototype assembled with low-resistive glass. The operation currently being monitored, together with previous simulation results, shows the impact of gas pollution caused by avalanches in gas gaps, and the necessity to shrink the gas-streaming volume. With the lateral edge of the detector sealed by a 3D-printed frame, a reduced gas-streaming volume of ~170 mL has been achieved for a direct gas flow to the active area. A high-rate test of the sealed MRPC prototype shows that, ensuring a 97% efficiency and 70 ps time resolution, the sealed design results in a stable operation current behavior at a counting rate of 3–5 kHz/cm2. The sealed MRPC will become a potential solution for future high luminosity applications.

X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector

We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10 nm thin NbTiN film and fabricated on a dielectric substrate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$SiO_{2}$</tex-math></inline-formula> , Nb <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{5}$</tex-math></inline-formula> ) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25 ns temporal recovery time and 82 ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors.

25-GHz Operation of ERSFQ Time-to-Digital Converter

Fast time-to-digital converters (TDCs), used to convert a continuous time interval into discrete number for further processing, serve diverse applications ranging from photon/particle detectors to communication systems employing delay-encoded pulses. Being a multi-rate digital circuit, the TDC is also a good candidate to explore operation of Energy-Efficient Rapid Single Flux Quantum (ERSFQ) circuits at high (>10 GHz) clock frequency. We designed a TDC using ERSFQ cells, targeting the 10-kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> SFQ5ee fabrication process at MIT Lincoln Laboratory. The main elements of the circuit comprise a 9-bit binary ripple counter and a parallel-to-serial converter. A frequency divider and a pulse distribution network with a decision-making element are designed to control the operation. The ERSFQ TDC was operated up to 25 GHz clock frequency (40 ps time resolution) and with a power consumption of around 14 μW for all ERSFQ components. The design specifications such as number of junctions and area will be discussed together with the power delivery technique involving an over-pumped feeding Josephson transmission line (JTL).

Visualizing Dynamic Processes with rapidFLIMHiRes: Ultra Fast Flim with Outstanding 10 PS Time Resolution

Fluorescence Lifetime Imaging (FLIM) has become an essential tool in Life Sciences over the last decade. However, up to now, users had to choose between high timing precision or fast data acquisition when using Time-Correlated Single Photon Counting (TCSPC) electronics. This was a drawback when investigating fast processes in cells or tissues such as protein interactions, FRET dynamics, or chemical reactions.

A multi-channel x-ray temporal diagnostic for measurement of time-resolved electron temperature in cryogenic deuterium-tritium implosions at OMEGA.

Electron-temperature (Te) measurements in implosions provide valuable diagnostic information, as Te is unaffected by residual flows and other non-thermal effects unlike ion temperature inferred from a fusion product spectrum. In OMEGA cryogenic implosions, measurement of Te(t) can be used to investigate effects related to time-resolved hot-spot energy balance. The proposed diagnostic utilizes five fast-rise (∼15 ps) scintillator channels with distinct x-ray filtering. Titanium and stepped aluminum filtering were chosen to maximize detector sensitivity in the 10 keV-20 keV range, as it has been shown that these x rays have similar density and temperature weighting to the emitted deuterium-tritium fusion neutrons. Initial data collected using a prototype nosecone on the existing neutron temporal diagnostic demonstrate the validity of this diagnostic technique. The proposed system will be capable of measuring spatially integrated Te(t) with 20 ps time resolution and <10% uncertainty at peak emission in cryogenic DT implosions.

A 100–750 MS/s 11-Bit Time-to-Digital Converter With Cyclic-Coupled Ring Oscillator

This paper presents the first measured cyclic-coupled ring oscillator (CCRO) time-to-digital converter (TDC). The CCRO realizes a robust true time-domain delay interpolation with sub-gate-delay resolution. The architecture employs real-time quantization to reduce conversion time and hence maximize bandwidth. Furthermore, the CCRO phase progression is encoded with a bubble error suppression logic, thereby building resilience to delay mismatches from circuit/layout imperfections. The prototype circuit implemented in a 28 nm CMOS process demonstrates a combination of high resolution and high sample rate over wide range of sample rates. The TDC achieves its peak figure-of-merit (FoM) of 0.051 pJ/conv.-step at 100 MS/s while delivering 8.38-bit linear resolution and 15.4 ps time resolution, operating from a 0.55 V supply. The TDC demonstrates the highest reported linear resolution of 9.29 bits among converters operating above 100 MS/s, at 125 MS/s and 0.9 V supply, while achieving 4.4 ps time resolution and 0.16 pJ/conv.-step FoM. Further, the real-time quantizing architecture allows fast operation up to 750 MS/s, where the TDC delivers 6-bit linear resolution and 0.48 pJ/conv.-step FoM operating from 0.9 V supply.

A field-programmable-gate-array based high time resolution arbitrary timing generator with a time folding method utilizing multiple carry-chains

A carry-chain based high time resolution arbitrary timing generator, which is fully implemented using field-programmable-gate-array resources, is reported in this paper. The arbitrary timing generator channel operates with two alternative carry-chains to achieve non-dead-time timing sequence generation, and a 45.3 ps time resolution with a 383 ps minimum pulse width can be obtained. The time resolution is further improved to 11.3 ps by employing four parallel carry-chains in a single arbitrary timing generator channel to realize "time folding." The timing generator has a high time stability, and the time uncertainty is below 12 ps within a wide time range of 1 ns-108 ns. The arbitrary timing generator can be used to generate continuous spike timing sequences with a picosecond time resolution.

Design and Analysis of a Multirate 5-bit High-Order 52 fsrms Δ ∑ Time-to-Digital Converter Implemented on 40 nm Altera Stratix IV FPGA

This paper describes FPGA implementation of a high-order continuous-time multi-stage noise-shaping (MASH) $\Delta \Sigma $ time-to-digital converter (TDC). The TDC is based on Gated Switched-Ring Oscillator (GSRO) and employs multirating technique to achieve improved performance over conventional $\Delta \Sigma $ TDCs. The proposed TDC has been implemented on an Altera Stratix IV FPGA development board. Dynamic and static tests were performed on the proposed design and experimental results demonstrate that it can perform its function without the need of calibration. The built-in clock circuitries of the FPGA board provides sampling clocks and operating frequencies of the GSROs. This work presents a 52 fsrms, 89.7 dB dynamic range and 0.18 ps time-resolution at 200 MHz, 800 MHz, 1600 MHz sampling rate at the first, second and third stage, respectively, which demonstrate that the proposed third-order TDC can play an important role in applications such as ADPLLs and range finders in which accuracy and speed are vital.

A Time-to-Amplitude Converter With High Impedance Switch Topology for Single-Photon Time-of-Flight Measurement

This paper presents a novel time-to-amplitude converter (TAC) for single-photon direct time-of-flight (d-TOF) measurement. An innovative high impedance switch approach is proposed to significantly improve the stability of the integral current and to increase the swing of the timing voltage, enabling high linearity together with low power consumption on TAC. Implemented in a standard $0.18~\mu \text{m}$ CMOS technology, the TAC occupies only an area of $100~\mu \text{m}^{2}$ , featuring a compact configuration. The experimental results indicate that the presented TAC can acquire a 78 ps timing resolution in a 20 ns full-scale range (FSR) under the supply of 1.8 V. In particular, the TAC gains an excellent linearity characteristic with the very low differential nonlinearity (DNL) and integral nonlinearity (INL) within ±0.1 LSB and ±0.15 LSB, respectively. Additionally, the extremely low dynamic power consumption of $20~\mu \text{W}$ and the high pixel fill factor of 16 % are also achieved simultaneously. Thanks to the outstanding advantages of high-performance and compactness, the proposed TAC may be a promising candidate to realize high-density compact TOF-based imagers.

A Small Diameter Ultrasonic Water Meter With Self-Diagnosis Function and Self-Adaptive Technology

Ultrasonic water meters have current widespread problems of poor site adaptability, low measurement accuracy, and poor stability. A high-precision intelligent ultrasonic water meter with self-diagnosis function and adaptive technology was proposed in this paper, which is focus on improving the measurement accuracy and repeatability of the small pipe diameters. The hardware circuit design of the ultrasonic water meter studied in this paper adopts the low-power STM32L053 microcontroller with Cortex-M0 core architecture and the high-precision 11 ps time resolution timing chip TDC-GP30 to complete the metering function. The software combines pulse width ratio and amplitude voltage measurement technology to make the water meter have self-diagnosis function, avoid measurement errors caused by accidental factors, improve adaptability and measurement accuracy, also the application of adaptive measurement period method is used to improve measurement repeatability. The software adopts the moving average filtering algorithm, which effectively reduces the fluctuation of the time-of-flight(ToF) difference and improve the measurement accuracy of the flow point in the low zone (between the minimum flow and the boundary flow). The experimental verification results show that the accuracy of the small-caliber ultrasonic water meter can reach within ±1.5 %, and the repeatability is less than 0.5 %. In the face of fluid disturbances, adaptive technology is used in this water meter to adjust the measurement period and carry out self-diagnostic function research, and automatically respond to deal with abnormal faults, thereby realizing the demand for intelligence.

Noise-tolerant single-photon imaging with a superconducting nanowire camera.

The quality of an image is limited to the signal-to-noise ratio of the output from sensors. As the background noise increases much more than the signal, which can be caused by either a huge attenuation of light pulses after a long-haul transmission or a blinding attack with a strong flood illumination, an imaging system stops working properly. Here we built a superconducting single-photon infrared camera of negligible dark counts and 60 ps timing resolution. Combining with an adaptive 3D slicing algorithm that gives each pixel an optimal temporal window to distinguish clustered signal photons from a uniformly distributed background, we successfully reconstructed 3D single-photon images at both a low signal level (∼1 average photon per pixel) and extremely high noise background (background-to-signal ratio = 200 within a period of 50 ns before denoising). Among all detection events, we were able to remove 99.45% of the noise photons while keeping the signal photon loss at 0.74%. This Letter is a direct outcome of quantum-inspired imaging that asks for a co-development of sensors and computational methods. We envision that the proposed methods can increase the working distance of a long-haul imaging system or defend it from blinding attacks.

Phototautomerism of Alloxazine in Acetic acid – Water solvent systems

The photophysics of Alloxazine was studied in Acetic acid – Water solvent systems which included neutral water (pH = 7), pure acetic acid, and their binary mixtures. Alloxazine was found to exhibit tautomerization into Isoalloxazine over a time-scale which depended on the nature of the solvent. While the process was too fast in neutral water to be detected with a ~100 ps time-resolution, it was drastically inhibited on addition of small quantities of acetic acid, displaying a remarkably long time-constant ~700 ps. However, further addition of acetic acid gradually decreased the time-constant, until it finally reached ~280 ps in pure acetic acid. Quantum chemical calculations indicated that the tautomerization occurred via Excited-state Double Proton Transfer (ESDPT) mechanism in cyclic intermolecular H-bonded complexes of Alloxazine with the solvent molecule (water or acetic acid). This involved reorganization of the H-bonded structures in the S1 energy surface, causing effective transfer of the N(1) bound proton of Alloxazine to its N(10) position, producing the Isoalloxazine tautomer. The H-bond reorganization of the complexes were strongly coupled with the solvation dynamics of the solvent concerned, and this helped to explain the large divergence of the tautomerization time-constants in the different solvents and solvent mixtures used in this study.

A 6-bit hierarchal TDC architecture for time-based ADCs

A 6-bit hieratical time-to-digital (TDC) architecture suitable for time-based ADC circuits is presented in this paper. The design consists of similar stages at which each stage recovers one bit. Using the proposed architecture, the total number of bits can be increased without complicating the design as in other conventional TDC architectures. A 6-bit 1.3 Gb/s TDC circuit has been designed and simulated in 28 nm mixed-signal CMOS technology based on the proposed architecture using 5.6 ps time resolution. A Calibration circuit has been designed for each delay line in order to tolerate the variations due to process and mismatch between transistors, which affect the designed delay lines in the design. Monte-Carlo simulations have been done to the designed TDC before and after using the calibration circuit. The calibration circuit corrects the delay line values with an error of ± 2%. The INL and the DNL accuracy of the designed TDC are less than 0.5 LSB and 0.4 LSB. The power consumption of the designed 6-bit TDC circuit is less than 1.3 mW including the calibration circuits.

Design and characterization of the FAST chip: a front-end for 4D tracking systems based on Ultra-Fast Silicon Detectors aiming at 30 ps time resolution

Detectors able to measure the time of flight with very high accuracy (∼10 ps RMS) are becoming fundamental in the design of new High Energy Physics experiments, where accurate time measurements will be used to mitigate pileup effects. The development of such detectors has spurred intense R&D in both silicon sensors and the associated readout electronics, aiming at obtaining silicon-based detectors with a time resolution in the few tens-of-picosecond range. This work presents FAST, a family of three different 20 channel amplifier-comparator chips, tailored to the readout of Ultra Fast Silicon Detectors. These ASICs have been designed optimizing the sensor-readout interplay with the aim of reaching the smallest possible jitter term. The three chips of the FAST family differ in the architecture of the front-end while sharing the channel back-end, consisting of a leading-edge discriminator and a LVDS driver. The goal of these front-ends is to achieve a time resolution of about 30 ps RMS while coupled to a sensor with a few pico-Farad capacitance, keeping the power budget of the single channel below 1.3 mW. This paper reports the description of the FAST design architecture and summarizes the results on the initial characterization of one chip of the FAST family, in a stand-alone test structure and when coupled to a UFSD.