Pulse Response Time Research Articles

An enhanced gated MCP-PMT for neutron detection in laser fusion experiments

The microchannel plate photomultiplier tube (MCP-PMT) is a photodetector that utilizes microchannel plates for signal amplification, offering rapid pulse response time of sub-nanosecond with a compact design and low dark current. A series of enhanced gated MCP-PMTs have been developed by incorporating a gating electrode between the photocathode and the MCPs, which have been employed in neutron detection during the double-cone ignition laser fusion experiment at the SGII Upgrade laser facilities.

The prediction of the survival in patients with severe trauma during prehospital care: Analyses based on NTDB database.

Traumas cause great casualties, accompanied by heavy economic burdens every year. The study aimed to use ML (machine learning) survival algorithms for predicting the 8-and 24-hour survival of severe traumas. A retrospective study using data from National Trauma Data Bank (NTDB) was conducted. Four ML survival algorithms including survival tree (ST), random forest for survival (RFS) and gradient boosting machine (GBM), together with a Cox proportional hazard model (Cox), were utilized to develop the survival prediction models. Following this, model performance was determined by the comparison of the C-index, integrated Brier score (IBS) and calibration curves in the test datasets. A total of 191,240 individuals diagnosed with severe trauma between 2015 and 2018 were identified. Glasgow Coma Scale (GCS), trauma type, age, SaO2, respiratory rate (RR), systolic blood pressure (SBP), EMS transport time, EMS on-scene time, pulse, and EMS response time were identified as the main predictors. For predicting the 8-hour survival with the complete cases, the C-indexes in the test sets were 0.853 (0.845, 0.861), 0.823 (0.812, 0.834), 0.871 (0.862, 0.879) and 0.857 (0.849, 0.865) for Cox, ST, RFS and GBM, respectively. Similar results were observed in the 24-hour survival prediction models. The prediction error curves based on IBS also showed a similar pattern for these models. Additionally, a free web-based calculator was developed for potential clinical use. The RFS survival algorithms provide non-parametric alternatives to other regression models to be of clinical use for estimating the survival probability of severe trauma patients.

High-uniformity 2 × 64 silicon avalanche photodiode arrays with silicon multiple epitaxy technology

In this paper, high-uniformity 2×64 silicon avalanche photodiode (APD) arrays are reported. Silicon multiple epitaxy technology was used, and the high performance APD arrays based on double-layer epiwafers are achieved for the first time, to the best of our knowledge. A high-uniformity breakdown voltage with a fluctuation of smaller than 3.5 V is obtained for the fabricated APD arrays. The dark currents are below 90 pA for all 128 pixels at unity gain voltage. The pixels in the APD arrays show a gain factor of larger than 300 and a peak responsivity of 0.53 A/W@M = 1 at 850 nm (corresponding to maximum external quantum efficiency of 81%) at room temperature. Quick optical pulse response time was measured, and a corresponding cutoff frequency up to 100 MHz was obtained.

Analysis and Correction of Measurement Error of Spherical Capacitive Sensor Caused by Assembly Error of the Inner Frame in the Aeronautical Optoelectronic Pod.

The ball joint is a multi-degree-of-freedom transmission pair, if it can replace the inner frame in the aviation photoelectric pod to carry the optical load, which will greatly simplify the system structure of the photoelectric pod and reduce the space occupied by the inner frame. However, installation errors in ball joint siting introduce nonlinear errors that are difficult to correct and two degree of freedom angular displacement of the ball joint is difficult to detect, which limits application in the precision control of two degrees of freedom systems. Studies of spherical capacitive sensors to date have not tested sensors for use in an inner frame stabilisation mechanism nor have they analysed the influence of installation error on sensor output. A two-axis angular experimental device was designed to measure the performance of a ball joint capacitive sensor in a frame stabilisation mechanism in an aeronautical optoelectronic pod, and a mathematical model to compensate for ball joint capacitive sensor installation error was created and tested. The experimental results show that the resolution of the capacitive sensor was 0.02° in the operating range ±4°, the repeatability factor was 0.86%, and the pulse response time was 39 μs. The designed capacitive sensor has a simple structure, high measurement accuracy, and strong robustness, and it can be integrated into ball joint applications in the frames of aeronautical photoelectric pods.

Avalanche photodetectors with photon trapping structures for biomedical imaging applications.

Enhancing photon detection efficiency and time resolution in photodetectors in the entire visible range is critical to improve the image quality of time-of-flight (TOF)-based imaging systems and fluorescence lifetime imaging (FLIM). In this work, we evaluate the gain, detection efficiency, and timing performance of avalanche photodiodes (APD) with photon trapping nanostructures for photons with 450 nm and 850 nm wavelengths. At 850 nm wavelength, our photon trapping avalanche photodiodes showed 30 times higher gain, an increase from 16% to >60% enhanced absorption efficiency, and a 50% reduction in the full width at half maximum (FWHM) pulse response time close to the breakdown voltage. At 450 nm wavelength, the external quantum efficiency increased from 54% to 82%, while the gain was enhanced more than 20-fold. Therefore, silicon APDs with photon trapping structures exhibited a dramatic increase in absorption compared to control devices. Results suggest very thin devices with fast timing properties and high absorption between the near-ultraviolet and the near infrared region can be manufactured for high-speed applications in biomedical imaging. This study paves the way towards obtaining single photon detectors with photon trapping structures with gains above 106 for the entire visible range.

Systematic Analysis of Reliability of Large-Area 4H-SiC Charged Particle Detector Under Harsh He Ion Irradiation

Silicon carbide (SiC) detectors have great potential in nuclear fusion diagnosis and intense irradiation field measurement due to their outstanding irradiation resistance, high charge collection efficiency (CCE), and fast pulse response time. However, the irradiation resistance and the performance degradation of SiC detectors as a result of He ion irradiation remains unclear. In this article, SiC detectors based on 4H-type material with the p-i-n junction structure were prepared, and their I-V characteristics, α-particle spectra, and linearity of energy response were evaluated before and after He ion irradiation at fluences ranging from 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> to 3 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The preirradiated SiC detector exhibited low dark current (<; 1 nA), high CCE (98.5%), and good energy resolution (0.87%). At an He ion irradiation fluence of 1 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , detector performance degradation was negligible, with no increase of dark current, CCE decreased to 85%, and a 2.2% degradation of energy resolution. At a fluence of 3 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , CCE decreased to 19.3%, with an 8.57% degradation in energy resolution, but the dark current was still lower than 2 nA, with good spectra measurement capabilities and high linearity of energy response. These results indicate that the He ion irradiation resistance of 4H-SiC detectors is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> times greater than silicon (Si) detectors.

Emission of diamonds, leucosapphire, and KU-1 quartz in the range of 200–800 nm excited by electron beams with a pulse duration of 0.5 and 12 ns

The paper presents the results of Cherenkov radiation (CR) studies in various crystals excited by nanosecond and subnanosecond electron beams with an electron energy of up to 400 and 200 keV, respectively. These studies are motivated by the need to develop and create calibrated sensors of runaway electrons for tokamak-type installations. The spectral and amplitude-time characteristics of the radiation of different specimens of diamonds, leucosapphire, and KU-1 quartz excited by the electron beams were obtained and compared. These crystals were chosen on the basis of their transparency in the ultraviolet region of the spectrum. CR was observed with a spectrometer. An increase in the radiation energy with decreasing wavelength was observed in synthetic diamonds of IIa type, leucosapphire, and KU-1 quartz. The amplitude-time characteristics of the radiation of crystals, including CR, were measured with a photodiode having a pulse response time of up to ≈80 ps. In chemical vapor deposited high purity diamonds excited by both nanosecond and subnanosecond beams, an exciton radiation with a maximum at 235 nm was observed. Results show that leucosapphire and quartz can be used to create detectors of electrons with energies above 200 keV.

Research on Calibration Method of 7kV Single Voltage Pulse for IGBT Models Test System

Power IGBT module is widely used in high power conversion applications in various fields because of the advantages of high voltage and high current applications. In order to avoid the influence of temperature rise to the device measurement, pulse test method is widely used to test its static and dynamic parameters, So there are single high pulse voltage source and single pulse high current source in power IGBT modules test instruments. For now in the metrology field, how to calibrate its Single High Pulse Voltage source is a difficult problem. Now the amplitude of single high pulse voltage source is above 7kV with the pulse width as 50 microseconds. Based on detailed research on the test principles of the power IGBT modules test instruments, the pulse high voltage divider and the data acquisition unit are used to setup a calibration device for Single High Pulse Voltage source to calibrate the amplitude of Single High Pulse Voltage source. Resistors are usedto develop the pulse high voltage divider, and did carefully research on the pulse response time, voltage dispersion, voltage regulation of the pulse high voltage divider. Also the data acquisition unit with 20MHz bandwidth and 100MS/s acquisition rate is evaluated through tests including vertical accuracy test, bandwidth test, rise time test, comparison test and etc.. Through above relevant test results, with the comprehensive consideration of the influence of each measurement uncertainty component, It have finished that the evaluation of the uncertainties of the amplitude measurement for Single High Pulse Voltage source. The uncertainty of measurement is better than 2% with the coverage factor as 2.

A novel structure of transmission line pulse transformer with mutually coupled windings

A novel structure of transmission line transformer (TLT) with mutually coupled windings is described in this paper. All transmission lines except the first stage of the transformer are wound on a common ferrite core for the TLT with this structure. A referral method was introduced to analyze the TLT with this structure, and an analytic expression of the step response was derived. It is shown that a TLT with this structure has a significantly slower droop rate than a TLT with other winding structures and the number of ferrite cores needed is largely reduced. A four-stage TLT with this structure was developed, whose input and output impedance were 4.2 Ω and 67.7 Ω, respectively. A frequency response test of the TLT was carried out. The test results showed that pulse response time of the TLT is several nanoseconds. The TLT described in this paper has the potential to be used as a rectangle pulse transformer with very fast response time.

AC Bolometer Theory and Measurements of Kinetic Inductance Bolometer-Resonators

AC bolometer theory is built on the established matrix formalism for quantum calorimeters and bolometers. The bolometer is represented by a 3 × 3 matrix with complex valued parameters. The bolometer matrix is used to model the behavior of the devices including the response to signal and noise, feedback, pulse response times, stability, and bolometer impedance. The effects of a current dependent bolometer impedance are included. The matrix simplifies theoretical computations of AC devices, including demodulation and the interactions between signals at different frequencies. This theory is applied to measurements of bolometers, each consisting of a kinetic inductance device suspended on a silicon nitride membrane. These measurements and analysis facilitate the optimization of the design and performance of these novel AC bolometers.

A high-impedance attenuator for measurement of high-voltage nanosecond-range pulses

A novel kind of high-impedance cable attenuator for measurement of high-voltage ns-range pulses is investigated in this paper. The input and output ports of the proposed attenuator were both high-impedance ports, and good pulse response characteristics of the proposed attenuator were obtained with pulse response time less than 1 ns. According to the requirement of measurement, two attenuators with lengths at 14 m and 0.7 m were developed with response time of 1 ns and 20 ns, and the attenuation coefficient of 96 and 33.5, respectively. The attenuator with the length of 14 m was used as a secondary-stage attenuator of a capacitive divider to measure the high-voltage pulses at several hundred ns range. The waveform was improved by the proposed attenuator in contrast to the result only measured by the same capacitive divider and a long cable line directly. The 0.7 m attenuator was also used as a secondary-stage attenuator of a standard resistant divider for an accurate measurement of high-voltage pulses at 100 ns range. The proposed cable attenuator can be used to substitute the traditional secondary-stage attenuators for the measurement of high-voltage pulses.

Microwave Properties of Superconducting Atomic-Layer Deposited TiN Films

We have grown superconducting TiN films by atomic layer deposition with thicknesses ranging from 6 to 89 nm. This deposition method allows us to tune the resistivity and critical temperature by controlling the film thickness. The microwave properties are measured, using a coplanar-waveguide resonator, and we find internal quality factors above a million, high sheet inductances (5.2-620 pH), and pulse response times up to 100 \mu s. The high normal state resistivity of the films (> 100 \mu\Omega cm) affects the superconducting state and thereby the electrodynamic response. The microwave response is modeled using a quasiparticle density of states modified with an effective pair-breaker,consistently describing the measured temperature dependence of the quality factor and the resonant frequency.

Characterization of fast microchannel plate photomultipliers for the ITER core LIDAR Thomson scattering system

In the new ITER core LIDAR Thomson scattering system under development, detectors with pulse response as low as 330 ps and 10 mm diameter active area, covering with good sensitivity the spectral range 380–1100 nm will be necessary. For the visible region 400–750 nm, fast microchannel plate photomultipliers with a GaAsP photocathode that fulfill the characteristics of speed, sensitivity and active area are already commercially available and have been recently characterized for operation in the JET edge LIDAR Thomson scattering system. In this paper we present a further characterization of these devices to evaluate their usefulness in the more demanding operating conditions of the ITER core LIDAR Thomson scattering system. The characteristics of these detectors with regard to linearity, gain recovery time, pulse repetition rate, quantum efficiency and response time for large F-number illumination, have been measured. Linearity and recovery time data have been interpreted according to a new, time dependent, microchannel plate operational model. The results show that these detectors are suitable also for use in ITER.

A Fast-Speed Pulse Detector Based on N-Type Si-Schottky Diode via Tuning Circuit

A fast-speed pulse detector based on n-type Si-Schottky diode mounted in the waveguide is investigated. The relation of the fast-speed pulse detector between response time and 3 dB bandwidth is analyzed. By adopting the tunable circuit, the matched bandwidth is achieved as wide as possible. Experi- mental results show that the pulse response time of the detector is less than 150 ps within random carrier signal 500 MHz bandwidth range between 35 GHz to 39 GHz via tuning circuit. The detector is very easy to operate because it does not need bias current or synch-pulse source.

Bi$_{3}$Fe$_{4}$Ga$_{1}$O$_{12}$ Garnet Properties and Its Application to Ultrafast Switching in the Visible Spectrum

We have synthesized Bi3Fe4Ga1O12 (BIGG) films on Gd3Ga5O12 and Gd3(ScGa)5O12 substrates by a pulsed laser deposition technique. X-ray diffraction and rocking curve analyses confirm the epitaxial quality of the films with a lattice constant close to 12.61 plusmn 0.01 Aring. Compared with that of a bismuth iron garnet Bi3Fe5O12 (BIG) film, the bandwidth of the BIGG transmittance (T) spectrum is extended and its left edge shifted down in wavelength by approximately 50 nm. This enables its Faraday rotation and switching speed to be tested at a wavelength of 532 nm. While BIGG film has a Faraday rotation angle slightly less than that of BIG film, its magnetooptical figure of merit, 2|thetasFd|/-ln(T%), is greatly improved to a typical value ~1.8 times larger than that of the BIG film. Further, the high-speed pulse response time of the BIGG film reaches 2.4 ns with a 1 mm aperture size at the wavelength of 532 nm.

CMOS and post-CMOS on-chip microwave pulse power detectors

Schottky diode microwave pulse power detectors were fabricated by both a CMOS process and a post-CMOS process. Focused ion beam (FIB) milling and ion-induced deposition were used for the post-CMOS fabrication. Fabricated detectors were tested under RF direct injection and RF radiation. CMOS fabricated Schotty diode power detectors had 820 ns pulse response time, 36 dBm dynamic range, and began to detect −21 dBm injected input power level. FIB fabricated Schottky diode power detectors with large contact area had 6 μs pulse response time, 25 dBm dynamic range, and began to detect −15 dBm injected input power level, and Schottky diode with small contact area had 100 ns pulse response time, 16 dBm dynamic range, and began to detect −1 dBm injected input power level. The main factor determining pulse response time and dynamic range was the area of the Schottky contact of diodes.

On-Chip RF Pulse Power Detector Using FIB as a Post-CMOS Fabrication Process

RF pulse power detectors on a CMOS chip may be useful in studying and mitigating the effects of unwanted RF radiation on chip performance. Focused ion beam (FIB) milling and ion-induced deposition were used as post-fabrication steps to build Schottky diodes on the CMOS chips fabricated using MOSIS. The standard CMOS layout of chips had Schottky diodes and was fabricated in the AMIS 0.5μ process. The directly fabricated diodes were in fact mostly ohmic and needed to be cut to fabricate FIB diodes, which showed normal diode characteristics. The FIB Schottky diodes detected pulses (i.e., bursts of 10 msec length) up to 15 GHz in the direct injection experiments, and the pulse response time was 192 ns.

GaAs photomultiplier for LIDAR Thomson scattering

Edge light detection and ranging (LIDAR) Thomson scattering at Joint European Torus (JET) is used for measuring temperature and density gradients of the edge plasma. The accuracy of the present measurements is limited not only by the spatial resolution of the system but also by photon statistics. The accuracy of the measurements can be increased by at least a factor of 2 by improving the sensitivity of the detection system. The present detectors are fast, 18 mm diameter microchannel plate photomultipliers (MCP PMTs) with multialkali photocathodes. The quantum efficiency is 5% at 650 nm decreasing toward the red. We present the characteristics of a newly developed MCP PMT with a GaAs photocathode. Four 18 mm diameter photomultipliers with a V-stack MCP and a preliminary prototype unit have been produced and tested to fully equip the edge LIDAR diagnostic. The GaAs photocathode of the new detectors has a quantum efficiency in excess of 20% in the spectral range of 520–850 nm. The effective quantum efficiency has been measured and is at least four times that of the present detectors. Investigations of the other characteristics required for use in a LIDAR system show good results. The pulse response time is slightly faster than that of the current tubes, potentially offering the possibility of improving the spatial resolution to better than the present value of 12 cm. The effect of varying the gate voltage between 100–300 V has been investigated. Lower gate voltages cause less ringing on the output signal and only increase the effective noise slightly.

Dashing with scooters to in-hospital emergencies: a randomised cross-over experiment

Objective: Physical exhaustion is a frequent condition in emergency medical teams after in-house emergency runs, which might affect the quality of advanced care. Newly available light-weight scooters may reduce exertion as measured by the cardiovascular response in these circumstances and, therefore, may reduce physical exhaustion on arrival. Methods: We undertook a randomised cross-over trial in a simulated in-house emergency alarm run to examine the influence of scooting compared with conventional running on pulse rate (primary outcome), manual skilfulness and response time. Results: We tested 24 emergency department professionals in eight emergency medical teams. After scooting the pulse rate was significantly lower compared with conventional running [157 (IQR 145–169) vs. 170 (IQR 154–175) min −1, P=0.004]. After the simulated emergency alarm run no difference was found in manual skilfulness and response time between scooting and running. Conclusion: Using scooters for simulated in-house emergency alarm runs markedly reduces the cardiovascular response of emergency medical teams.

70 GHz InGaAs metal-semiconductor-metal photodetectorsfor polarisation-insensitive operation

InGaAs metal-semiconductor-metal photodetectors with 0.2 µm feature size finger electrodes have been fabricated. A pulse response time of 3.8 ps for 1.55 µm light was measured by means of electro-optical sampling. A 3 dB bandwidth of 70 GHz was extracted from the time domain data. Polarisation-insensitive operation under front illumination was obtained by employing semicircular-type finger electrodes for the photodetectors with a 14 µm diameter active area.