Sub-nanosecond Resolution Research Articles

Recovering temporal PSF using ToF camera with delayed light emission

Recovering temporal point spread functions (PSFs) is important for various applications, especially analyzing light transport. Some methods that use amplitude-modulated continuous wave time-of-flight (ToF) cameras are proposed to recover temporal PSFs, where the resolution is several nanoseconds. Contrarily, we show in this paper that sub-nanosecond resolution can be achieved using pulsed ToF cameras and an additional circuit. A circuit is inserted before the illumination so that the emission delay can be controlled by sub-nanoseconds. From the observations of various delay settings, we recover temporal PSFs of the sub-nanosecond resolution. We confirm the effectiveness of our method via real-world experiments.

The Development of an EM-Field Probing System for Manual Near-Field Scanning

This research was conducted to visualize the frequency-dependent electromagnetic field distribution for electromagnetic compatibility (EMC) applications and the time evolution of the current flow induced by an electrostatic discharge (ESD) on complex-shaped electronic systems. These objectives were achieved by combining magnetic field probing with a system that automatically records the probe's position and orientation. The local magnetic field associated with the probe location was recorded and displayed at near real time on the captured 3-D geometry. Consequently, a field strength map was obtained for EMC applications. Also, a video showing the spreading of the ESD-induced current with subnanosecond resolution was captured for ESD applications after the ESD-induced surface current density associated with the probe location was recorded.

Electric field development in γ-mode radiofrequency atmospheric pressure glow discharge in helium

Time development of electric field strength during radio-frequency sheath formation was measured using Stark polarization spectroscopy in a helium γ-mode radio-frequency (RF, 13.56 MHz) atmospheric pressure glow discharge at high current density (3 A cm−2). A method of time-correlated single photon counting was applied to record the temporal development of spectral profile of He I 492.2 nm line with a sub-nanosecond temporal resolution. By fitting the measured profile of the line with a combination of pseudo-Voigt profiles for forbidden (2 1P–4 1F) and allowed (2 1P–4 1D) helium lines, instantaneous electric fields up to 32 kV cm−1 were measured in the RF sheath. The measured electric field is in agreement with the spatially averaged value of 40 kV cm−1 estimated from homogeneous charge density RF sheath model. The observed rectangular waveform of the electric field time development is attributed to increased sheath conductivity by the strong electron avalanches occurring in the γ-mode sheath at high current densities.

Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolvedin situLaue diffraction

We report direct lattice-level measurements of plastic relaxation kinetics through time-resolved, in situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27--210 GPa. For a 50-GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points ($l0.6$ ns), and the average shear strain relaxes to a near steady state over $\ensuremath{\sim}1$ ns. For 80- and 125-GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure $\ensuremath{\sim}65$ GPa. The relaxation rate and shear stresses are used to estimate the dislocation density, and these quantities are compared to the results of other high-pressure work, flow stress models, and molecular dynamics simulations.

Measuring excited state lifetime of Rb atoms with pump-probe technique

A technique for measuring the excited state lifetime τex of optical transitions in alkali atoms is presented. It is a form of pump-probe technique based on time-resolved optical transmission through the atomic vapor cell. This technique can serve as an alternative to the traditionally used time-resolved photofluorescence methods when measuring alkali vapor cells with heavily quenched fluorescence, where the τex is expected to be on the order of a few nanoseconds, and the highly sensitive fluorescence detectors with sub-nanosecond temporal resolution that are required may not be available. We use this technique to measure the τex of Rb atoms in vapor cells with different buffer gas pressures.

Electrical Analysis of Cell Membrane Poration by an Intense Nanosecond Pulsed Electric Field Using an Atomistic-to-Continuum Method

Pulsed electric fields of sufficient magnitude and duration trigger functional responses and modifications in biological cells. Transient nanometer-sized pores are believed to form within nanoseconds in cell membranes exposed to high-intensity (MV/m) nanosecond pulsed electric fields (nsPEFs), and while it is clear that polar water molecules play a key role in electroporation, no signature for pore initiation has yet been identified. To address this, we combine molecular dynamics simulations and quasi-static 3-D finite-difference analysis to investigate the electrostatic interactions that drive pore formation in homogenous lipid bilayers exposed to intense nsPEFs. The developed methodology uniquely enables the extraction of 3-D spatiotemporal profiles of electric potentials, electric fields, and electric field gradients in biological membranes with atomistic detail and sub-nanosecond resolution. As a result, this study captures and elucidates several dynamic phenomena observed experimentally and provides a fundamental framework for further development.

Prototyping the PANDA Barrel DIRC

The design of the Barrel DIRC detector for the future PANDA experiment at FAIR contains several important improvements compared to the successful BABAR DIRC, such as focusing and fast timing. To test those improvements as well as other design options a prototype was build and successfully tested in 2012 with particle beams at CERN. The prototype comprises a radiator bar, focusing lens, mirror, and a prism shaped expansion volume made of synthetic fused silica. An array of micro-channel plate photomultiplier tubes measures the location and arrival time of the Cherenkov photons with sub-nanosecond resolution. The development of a fast reconstruction algorithm allowed to tune construction details of the detector setup with test beam data and Monte-Carlo simulations.

Calibration of detectors of ionizing emissions by means of a subnanosecond runaway electron beam generated by discharge in open atmosphere at high overvoltages

The electric discharge in air at atmospheric pressure under the conditions of multiple overvoltages generates an electron beam of subnanosecond duration. By means of measurements of the resolution time of registration lines including different detectors of ionizing emissions, efficiency is demonstrated of the beam application for calibration of the detectors with the subnanosecond resolution. The basic advantages of such a way of calibration is the absence of the evacuated accelerating tube, small dimensions of the source, and the big resource.

Performance evaluation of multiple (32 channels) sub-nanosecond TDC implemented in low-cost FPGA

NA62 experiment Straw tracker frontend board serves as a gas-tight detector cover and integrates two CARIOCA chips, a low cost FPGA (Cyclon III, Altera) and a set of 400Mbit/s links to the backend. The FPGA houses 16 pairs of sub-nanosecond resolution TDCs with derandomizers and an output link serializer. Evaluation methods, including simulations, and performance results of the system in the lab and on a detector prototype are presented.

QIE10: a new front-end custom integrated circuit for high-rate experiments

We present results on a new version of the QIE (Charge Integrator and Encoder), a custom Application Specific Integrated Circuit (ASIC) designed at Fermilab. Developed specifically for the measurement of charge from photo-detectors in high-rate environments, this most recent addition to the QIE family features 3 fC sensitivity, 17-bits of dynamic range with logarithmic response, a Time-to-Digital Converter (TDC) with sub-nanosecond resolution, and internal charge injection. The device is capable of dead-timeless operation at 40 MHz, making it ideal for calorimetry at the Large hadron Collider (LHC). We present bench measurements and integration studies that characterize the performance, radiation tolerance measurements, and plans for deployment in the Atlas and CMS detectors as part of the Phase 1 and Phase 2 upgrades.

An All-Digital Coincidence-Selection and Coincidence-Trigger Generation for a Small Animal RPC-PET Camera

The time resolution for gamma photon pairs of a detector based on resistive plate chamber technology is close to 300 ps FWHM. This allows a tight time window for coincidence detection, reducing the number of random coincidences observed and the overall noise of the acquired image. We implemented, inside a Xilinx Virtex-5 field programmable gate array, a fully programmable coincidence-trigger system with sub-nanosecond resolution and low latency for a small animal RPC-PET camera being built. An automatic procedure to construct a histogram of coincidences was implemented that helps characterizing the camera and allows compensating for different delays in the time channels. The time window for coincidences can then be placed at the optimal position helping rejecting coincidences from undesired sources.

Development of new photon-counting detectors for single-molecule fluorescence microscopy.

Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and wide field illumination and detection to study surface immobilized or slowly diffusing molecules. Both approaches have common features, but also differ in significant aspects. In particular, they use different detectors, which share some requirements but also have major technical differences. Currently, two types of detectors best fulfil the needs of each approach: single-photon-counting avalanche diodes (SPADs) for point-like detection, and electron-multiplying charge-coupled devices (EMCCDs) for wide field detection. However, there is room for improvements in both cases. The first configuration suffers from low throughput owing to the analysis of data from a single location. The second, on the other hand, is limited to relatively low frame rates and loses the benefit of single-photon-counting approaches. During the past few years, new developments in point-like and wide field detectors have started addressing some of these issues. Here, we describe our recent progresses towards increasing the throughput of single-molecule fluorescence spectroscopy in solution using parallel arrays of SPADs. We also discuss our development of large area photon-counting cameras achieving subnanosecond resolution for fluorescence lifetime imaging applications at the single-molecule level.

Characterisation method for chip card ESD events causing terminal failures

Several dual-interface (DI-) chip cards have been reported to cause a system crash of certain card terminals during the card insertion process. Such terminal failures could be reproduced by inserting charged cards which thus act as ESD/EMI sources. In this work, the cards’ discharge pulses are characterised with sub-nanosecond temporal resolution in a configuration very similar to the one in the field. From the exact pulse forms effective equivalent circuits are extracted, which show a clear correlation to the failure generation capability of the cards. Especially the influence of an absent RF antenna and the missing generation of terminal failures for a certain DI-card can be seen electrically by a lower effective card capacity. The presented test and extraction method is not only able to classify the failure generation capability of chip cards but could also lead to a future “charged card model” (CCM) for testing the ESD susceptibility of terminals.

Implementation of high-resolution time-to-digital converter in 8-bit microcontrollers

This paper will demonstrate how a time-to-digital converter (TDC) with sub-nanosecond resolution can be implemented into an 8-bit microcontroller using so called "direct" methods. This means that a TDC is created using only five bidirectional digital input-output-pins of a microcontroller and a few passive components (two resistors, a capacitor, and a diode). We will demonstrate how a TDC for the range 1-10 μs is implemented with 0.17 ns resolution. This work will also show how to linearize the output by combining look-up tables and interpolation.

Fast Ionization Wave Development in Atmospheric-Pressure Air

Pulsed-discharge development in a point-to-plane geometry is investigated with subnanosecond temporal resolution. A short high-voltage pulse with a duration of 400 ps and peak voltage U = 224 kV was applied to a discharge gap of 1-30 mm. The discharge propagated in atmospheric-pressure air. Ultrahigh overvoltage (5-50 times) generates runaway electrons in the front of ionization wave and increases the plasma channel diameter and velocity of ionization wave propagation. Formation of homogeneous atmospheric-pressure nonequilibrium plasma has been demonstrated.

Subnanosecond spectral diffusion of a single quantum dot in a nanowire

We have studied spectral diffusion of the photoluminescence of a single CdSe quantum dot inserted in a ZnSe nanowire. We have measured the characteristic diffusion time as a function of pumping power and temperature using a recently developed technique [G. Sallen et al, Nature Photon. \textbf{4}, 696 (2010)] that offers subnanosecond resolution. These data are consistent with a model where only a \emph{single} carrier wanders around in traps located in the vicinity of the quantum dot.

CdTe-based detectors for recording X-ray pulses with a subnanosecond resolution

Characteristics and manufacturing methods of semiconductor detectors made of pressed cadmium telluride are given. The sensitivity of the detectors is ∼(1–5) × 10−19 A cm2 s/quantum. SPPD29k and SPPD29-02 detectors are calibrated by subnanosecond X-ray pulses generated by the СПИН-2 accelerator. The measured pulse durations are τ0.5 = 0.29 and 0.47 ns, respectively. The X-ray pulse shape of the APCA accelerator is recorded.

S45-03 - Biochemical and biophysical aspects of the pathophysiology of first episode of schizophrenia

IntroductionThe knowledge of pathophysiology of first psychotic episode is still fragmentary.AimTo investigate some biochemical and biophysical parameters in first-episode, drug-naive schizophrenic (FES) patients.Methods26 FES patients (ICD-10; F 20.0 and F 20.3) and 15 age-and gender-match volunteers were investigated. Clinical severity of FES patients were assessed by PANSS scale. Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, middle-mass endotoxic molecules (MMEM) and malondialdehyde (MDA) levels were measured using respective methods. Steady-state and subnanosecond fluorescent spectroscopy were used for the investigation of albumin conformational changesResults Severity of disorder prior the treatment was 75.5 ± 2.2 (PANSS score). FES patients were characterized by significant increase in MAO activity (99%) and MMEM concentration (124%) and significant decrease in SSAO activity (26%) as compared with controls. Changes of albumin conformational and functional parameters (“effective” albumin concentration and“reserve” of albumin binding) estimated by steady-state fluorescent spectroscopy were insignificant. Factor analysis revealed that MAO and SSAO are more tightly connected with pathogenetic mechanisms of FES then MMEM, MDA and albumin functional parameters. Significant conformational changes of albumin of FES patients were detected using pulse fluorescent spectroscopy with subnanosecond resolution. Results are compared with the data received in chronic schizophrenic patients.ConclusionFrom pathophysiological point of view FES is the initial step in development of pathologically disturbed biochemical status characteristic to chronic schizophrenia.The study was supported by grant # 3156 from International Science and Technology Center (ISTC).

P03-348 - Biochemical and biophysical aspects of the pathophysiology of first episode of schizophrenia

IntroductionThe knowledge of pathophysiology of first psychotic episode is still fragmentary.AimTo investigate some biochemical and biophysical parameters in first-episode, drug-naive schizophrenic (FES) patients.Methods26 FES patients (ICD-10; F 20.0 and F 20.3) and 15 age-and gender-match volunteers were investigated. Clinical severity of FES patients were assessed by PANSS scale. Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, middle-mass endotoxic molecules (MMEM) and malondialdehyde (MDA) levels were measured using respective methods. Steady-state and subnanosecond fluorescent spectroscopy were used for the investigation of albumin conformational changes.ResultsSeverity of disorder prior the treatment was 75.5 ± 2.2 (PANSS score). FES patients were characterized by significant increase in MAO activity (99%) and MMEM concentration (124%) and significant decrease in SSAO activity (26%) as compared with controls. Changes of albumin conformational and functional parameters (“effective” albumin concentration and “reserve” of albumin binding) estimated by steady-state fluorescent spectroscopy were insignificant. Factor analysis revealed that MAO and SSAO are more tightly connected with pathogenetic mechanisms of FES then MMEM, MDA and albumin functional parameters. Significant conformational changes of albumin of FES patients were detected using pulse fluorescent spectroscopy with subnanosecond resolution. Results are compared with the data received in chronic schizophrenic patients.ConclusionFrom pathophysiological point of view FES is the initial step in development of pathologically disturbed biochemical status characteristic to chronic schizophrenia. The study was supported by grant # 3156 from International Science and Technology Center (ISTC).