Signal Pulse Shape Research Articles

Review of Research on Nuclear Signal Pulse Shaping

Pulse shaping can greatly improve the signal-to-noise ratio and has been widely used in nuclear signal processing. This paper gives a brief overview of the current research status of nuclear signal pulse shaping at home and abroad. It describes in detail the three traditional pulse shaping methods of quasi-Gaussian shaping, triangular shaping and trapezoidal shaping, and discusses the nuclear pulse signal shaping that has appeared in recent years. And a brief introduction to the nuclear pulse signal shaping methods that have emerged in recent years is also given.

Investigation of the Influence of Infrared Illumination on the Pulse Shapes of Output Signals of CdZnTe Detectors.

The spectrometric characteristics of CdZnTe detectors are largely determined by the nonuniformity of the material and the influence of the negative polarization effects associated with the formation of space charges in the sensitive volume of the detector. They change the electric field distribution in the detector and affect the efficiency of the charge carrier collection. An analysis of the waveforms of the output pulses was used to investigate the uniformity of the charge collection and electric field distribution in the detectors when irradiated by the alpha particles. The influence of infrared (IR) illumination on these parameters was evaluated. IR illumination had no positive effect on the planar detector but greatly improved the charge collection in quasi-hemispherical detectors in the peripheral (corner) regions. The output pulse amplitude increased, and the rise time notably decreased. Polarization that occurred predominantly in the corner regions at low temperatures (from -30 °C to -20 °C) was eliminated using IR illumination.

Alpha and beta spillover in liquid scintillation counting analysis of urine samples.

Rapid detection and quantification of gross alpha/beta-emitting radionuclides by liquid scintillation counting (LSC) is vital in guiding response to a nuclear or radiological incidents. Liquid scintillation counters use signal pulse shape to discriminate alpha and beta events in samples but require precise optimization to minimize the spillover, or misclassification, of those events. In this study, samples at varying activity levels were analyzed by LSC to determine the effect of activity level, emitter type, and sample matrix on spillover. Analysis proved a matrix effect and a direct correlation of activity level on spillover percentage for both alpha and beta emitting-nuclides.

Hadron shower background in KOTO 2019 - 2021 data

One of the keys for the search of KOTO experiment is to suppress the backgrounds caused by hadron showers in CsI calorimeter. We developed three methods to discriminate the hadron showers from gamma showers. The methods use 1) pulse shape of signals, 2) shower shape on the calorimeter, and 3) depth of the showers in the calorimeter. We report on the discrimination power of these methods. The performance of the third method remained the same even if the dark current of silicon photomultipliers increased by a factor of 85 due to irradiation.

Performance evaluation of three silicon photomultiplier detector modules within the MAGIC telescopes PMT-based camera

MAGIC is a system of two imaging atmospheric Cherenkov telescopes (IACTs) located on the Canary island of La Palma. Each telescope’s imaging camera consists of 1039 photomultiplier tubes (PMTs). We developed three detector modules based on silicon photomultipliers (SiPMs) of seven pixels each that are mechanically and electronically compatible with those used in the MAGIC camera. These prototype modules are installed next to the PMTs in the imaging camera and are operated in parallel. To achieve a similar active area per pixel we used seven to nine SiPMs for producing a composite pixel. The SiPM signals within one such pixel are actively summed up for retaining the fast signal pulse shapes. Two different PCB designs are tested for thermal performance. We present our simulations of Cherenkov and light of the night sky (LoNS) responses. Based on those we calculate the signal-to-noise ratio (SNR) for this imaging application. We compare our expectations with the measurements of one of the SiPM-based detector modules.

Droplet-on-demand metal additive manufacturing using a magnetostrictive actuator

The molten metal droplet-on-demand (MMDoD) mechanism is one of the many advanced ways to achieve metal additive manufacturing (AM). A novel MMDoD mechanism is designed and developed using a magnetostrictive actuator to achieve a desktop-based metal AM system using a low input voltage circuit. The MMDoD mechanism further includes the use of a thermally insulating piston to protect the actuator from the heat of the molten metal pool. The oscillation of the piston in the MMDoD mechanism is used to generate the molten metal droplets. To generate reproducible molten metal droplets with the least geometrical variations, the effect of the input signal pulse shape, the input signal voltage amplitude, and stand-off distance between piston and nozzle entrance on the MMDoD mechanism performance is studied using high-speed videography. The input signal pulse shape is selected to be either the unfiltered signal (UFS) and low pass filtered signal (LPFS). Using UFS and LPFS, a parametric study of molten metal droplets size and its variation is conducted by varying the stand-off distance between the piston and nozzle and input signal voltage amplitude across the magnetostrictive actuator. To demonstrate the metal additive manufacturing using this system, a study is conducted to find the optimal gap between each droplet. Using the MMDoD system, molten metal droplets of uniform shape (571 μm) are ejected at fixed generation rate and deposited with an optimal gap to print conductive traces on a polymer substrate. As these conductive lines were printed using metal on polymer substrate, they could provide a new way to connect the electronic components to achieve AM of the electronic circuits.

Simultaneous monitoring of residual chromatic dispersion and OSNR of NRZ-OOK signal based on asynchronous delay-tap sampling and image processing

We demonstrated a simultaneous residual chromatic dispersion (CD) and optical signal-to-noise ratio (OSNR) monitoring method for non-return-to-zero on-off keying signals by employing the delay-tap sampling and image processing techniques. Delay-tap sampling scatter plots reflect the signal pulse shape change and image processing can extract the contour of the scatter plots. Numerical simulation shows that the OSNR monitoring range is from 12 to 32 dB with <0.5 dB error and the CD monitoring range is from 0 to 1360 ps/nm. In the experiment, the OSNR monitoring range is from 14 to 30 dB and the CD monitoring range can go up to 1275 ps/nm.

Characterization and operational stability of EJ276 plastic scintillator-based detector for neutron spectroscopy

A state-of-the-art EJ276 plastic scintillator-based detector for neutron spectroscopy has undergone detailed characterization both in a controlled laboratory and on-site at the SPIDER negative ion source facility in Padua. The device will be used for the spectroscopy of 2.5 MeV neutrons produced from Deuterium-Deuterium fusion reactions occurring inside the SPIDER beam dump. A plastic based scintillator with neutron/gamma discrimination has some key advantages over the commonly used organic liquid scintillators with regards economic cost and handling safety. The purpose of this characterization is to determine the operational functionality and reliability of this new breed of detector material. Several tests were performed to verify expected operation with regards to signal reproducibility, long-term stability, and pulse shape discrimination (PSD) capabilities. It was found that the detector system (EJ276 scintillator + photomultiplier tube) performed well in terms of reproducibility and PSD, however the long-term stability of the scintillator light output was seen to diminish considerably over time (>50% decrease) and must be consistently monitored in order to have an accurate conversion scale needed for energy spectroscopy.

Low background measurement in CANDLES-III for studying the neutrinoless double beta decay of Ca48

We developed a CANDLES-III system to study the neutrino-less double beta (0$\nu\beta\beta$) decay of $^{48}$Ca. The proposed system employs 96 CaF$_{2}$ scintillation crystals (305 kg) with natural Ca ($^{\rm nat.}$Ca) isotope which corresponds 350\,g of $^{48}$Ca. External backgrounds were rejected using a 4$\pi$ active shield of a liquid scintillator surrounding the CaF$_2$ crystals. The internal backgrounds caused by the radioactive impurities within the CaF$_2$ crystals can be reduced effectively through analysis of the signal pulse shape. We analyzed the data obtained in the Kamioka underground for a live-time of 130.4\,days to evaluate the feasibility of the low background measurement with the CANDLES-III detector. Using Monte Carlo simulations, we estimated the background rate from the radioactive impurities in the CaF$_{2}$ crystals and the rate of high energy $\gamma$-rays caused by the (n, $\gamma$) reactions induced by environmental neutrons. The expected background rate was in a good agreement with the measured rate, i.e., approximately 10$^{-3}$ events/keV/yr/(kg of $^{\rm nat.}$Ca), in the 0$\nu\beta\beta$ window. In conclusion, the background candidates were estimated properly by comparing the measured energy spectrum with the background simulations. With this measurement method, we performed the first search for 0$\nu\beta\beta$ decay in a low background condition using a detector with a Ca isotope, in which the Ca present was not enriched, in a scale of hundreds of kg. The $^{48}$Ca isotope has a high potential for use in 0$\nu\beta\beta$ decay search, and is expected to be useful for the development of a next-generation detector for highly sensitive measurements.

Information transfer via temporal convolution in nonlinear optics

Nonlinear parametric processes involving ultrashort pulses are typically carried out in time domain, which mathematically corresponds to a convolution of their frequency spectra. In contrast, this spectral convolution changes into a multiplication operation when performing the nonlinear interaction in frequency domain. Here, we extend the scope of frequency-domain nonlinear optics by demonstrating its ability to perform a temporal convolution. Through this approach, nonlinear optical operations that are inaccessible in time domain can be realised: specific optical information can be coherently advanced by picoseconds within a pulse sequence—a newly generated second harmonic pulse carries the amplitude and phase information of two input pulses. This central pulse is isolated when using an input field consisting of two cross-polarized input pulses in combination with type-II second harmonic generation. The effects of nonlinear temporal convolution can be viewed from the aspect of signal processing and pulse shaping, where the nonlinear interaction in the parametric crystal plays the role of a dynamic linear optical filter—in contrast to conventional static filters—with a shaping mask instantaneously adapting to the laser field.

Dual-threshold Time-over-Threshold nonlinearity correction for PET detectors

The Time-over-Threshold (ToT) analog-to-digital signal processing approach provides a power-efficient and cost-effective technique to extract all relevant information from detectors in high-energy physics and Positron Emission Tomography (PET) imaging. In this work, three calibration methods were investigated to correct the inherent nonlinear response of the ToT data using 1) γ-ray sources of various energies, 2) internal electronic gain variation in the LabPET II ASIC in combination with a single energy γ-ray source, and 3) internal gain variation along with an embedded pulse charge generator in replacement of a γ-ray source. The electronic gain calibration technique was shown to achieve equivalent correction accuracy as the γ-ray sources calibration. Furthermore, this method has the advantage of allowing a faster calibration requiring only one single γ-ray source (e.g., 511 keV) and a quick automated routine to sweep the internal gain. The last technique would be the most convenient method, provided that the signal pulse shape would be similar to the detector signal responding to a typical γ-ray event. Whereas the concept was demonstrated with a step pulse, extensive processing would be required to recover the nonlinearity correction factors for the detector pulse shape. After calibration, the 511-keV energy resolution of typical LabPET II detectors was only slightly degraded, by less than 12% and 8% for methods 1) and 2), respectively, relative to a conventional ADC-based data acquisition system. The feasibility of fast and accurate calibration for the nonlinearity correction of ToT data in PET imaging was demonstrated, making a daily quality control within reach.

Fission fragment atomic number measurements using Bragg detectors

A Bragg detector with a Frisch grid and 1 metre-long time-of-flight section with microchannel plate assemblies was characterized at the Lohengrin fission fragment separator at the Institut Laue-Langevin (ILL) by measuring 235U fission fragments of selected masses and energies at the Lohengrin focal plane. The aim of the measurements was to investigate the response of Bragg detectors to differing nuclear charge states. Energy-loss and a signal-risetime dependent parameters were defined and extracted from the accumulated signal pulse shapes, and their behaviour as a function of fragment velocity was investigated. The experimental results are compared to a SRIM-2013 simulation. Measurements of fission fragment ranges in isobutane are presented. Average proton numbers for measured fragment masses were identified and could be resolved by the parameters, which exhibited monotonic variation with charge. The results differed from SRIM both in trends and in values, with SRIM simulations exhibiting non-monotonic behaviour with proton number.

FPGA implementation of a deep learning algorithm for real-time signal reconstruction in particle detectors under high pile-up conditions

The analog signals generated in the read-out electronics of particle detectors are shaped prior to the digitization in order to improve the signal to noise ratio (SNR). The real amplitude of the analog signal is then obtained using digital filters, which provides information about the energy deposited in the detector. The classical digital filters have a good performance in ideal situations with Gaussian electronic noise and no pulse shape distortion. However, high-energy particle colliders, such as the Large Hadron Collider (LHC) at CERN, can produce multiple simultaneous events, which produce signal pileup. The performance of classical digital filters deteriorates in these conditions since the signal pulse shape gets distorted. In addition, this type of experiments produces a high rate of collisions, which requires high throughput data acquisitions systems. In order to cope with these harsh requirements, new read-out electronics systems are based on high-performance FPGAs, which permit the utilization of more advanced real-time signal reconstruction algorithms. In this paper, a deep learning method is proposed for real-time signal reconstruction in high pileup particle detectors. The performance of the new method has been studied using simulated data and the results are compared with a classical FIR filter method. In particular, the signals and FIR filter used in the ATLAS Tile Calorimeter are used as benchmark. The implementation, resources usage and performance of the proposed Neural Network algorithm in FPGA are also presented.

The CMS ECAL Phase-2 upgrade for high precision energy and timing measurements

The CMS electromagnetic calorimeter (ECAL) is a homogeneous calorimeter made of about 75,000 lead tungstate scintillating crystals. In view of the high-luminosity phase of the LHC, the ECAL electronics must be upgraded to cope with the more stringent requirements in terms of trigger latency and rate. The new electronics will transmit the data in streaming mode from the front-end electronics to the off-detector electronics, where the trigger primitives will be formed in powerful FPGAs. The front-end electronics will feature two new radiation-hard chips: a dual gain trans-impedance amplifier (TIA) and a sampling ADC with loss-less data compression. The TIA choice preserves the fast pulse shape of signals in the lead tungstate coupled to avalanche photodiodes (APD), and it is more resilient to the noise increase due to the radiation-induced APD leakage current. An important characteristic of the new design will be the capability to provide precision timing measurements, of the order of 30ps, for photons and electrons above 50GeV. The excellent time resolution will improve the overall CMS physics performance by mitigating the high pile-up effects. First characterization results of the TIA chip will be shown, and studies of energy and timing resolution performed in beam tests with the prototype electronics will be presented.

Limits on interactions between weakly interacting massive particles and nucleons obtained with NaI(Tl) crystal detectors

Limits on the cross section for weakly interacting massive particles (WIMPs) elastic scattering on nuclei in NaI(Tl) detectors at the Yangyang Underground Laboratory are obtained from a 2967.4 kg·day data exposure. The nuclei recoiling from the scattering process are identified by the pulse shape of the scintillation light signals that they produce. The data are consistent with a no nuclear-recoil hypothesis, and WIMP-mass-dependent 90% confidence-level upper-limits are set on WIMP-nuclei elastic scattering cross sections. These limits partially exclude the DAMA/LIBRA allowed region for WIMP-sodium interactions with the same NaI(Tl) target material. The 90% confidence level upper limit on the WIMP-nucleon spin-independent cross section is 3.26×10−4 pb for a WIMP mass of 10 GeV/c2.

Evaluation of a Compton camera concept using the 3D CdZnTe drift strip detectors

At DTU Space, a high-resolution 3D CZT drift strip detector has been developed and a number of prototype detectors were fabricated, allowing for sub-mm position resolution at high energies (>100 keV), as well as high energy resolution. For spectral and spatial performance, the 3D CZT prototype detectors were characterized with a fine collimated high-energy (Cs137) monochromatic beam (0.2 mm × 40 mm) using a digitizer with which the pulse shapes of the bi-polar signals from all electrodes could be analysed. Data analysis consist of position determination for single as well as double interaction events handled within the detector. The double interaction events (e.g. Compton interaction) are utilized to characterize the imaging performance of the 3D CZT drift strip detector prototype when operating as a Compton camera.

Complexity analysis of flexible transmitter digital signal processing for terabit (40 × 50G) four‐level pulse amplitude modulation transmission

The authors propose a transmitter digital filter for joint optimisation of signal pulse shaping and chromatic dispersion pre-compensation, providing a detailed analysis of the architecture complexity. Experimental transmission of 40 × 50G channels (28 Gbaud four-level pulse amplitude modulation) over up to 110 km uncompensated standard single mode fibre with low-bandwidth hardware is demonstrated.

In brief

PAGE 1061 Researchers in Egypt have created a novel pseudo-omnidirectional antenna placed on an artificial magnetic conductor surface with a heart-shaped radiation pattern. The implemented antenna is appropriate for wide beam applications such as handheld devices, and with a reduced back radiation has potential for wearable applications. PAGE 1084 A transmitter digital filter for joint optimisation of signal pulse shaping and dispersion pre-compensation has been presented by researchers in Brazil. The filter provides complexity analysis, and a 2Tb/s transmission was demonstrated over up to 110 km uncompensated standard single mode fibre (SSMF) using low bandwidth optoelectronics. Detailed layer diagram of the folded dipole. PAGE 1070 Winding switching for improved performance of permanent magnet vernier machines (PMVMs) has been proposed by researchers in South Korea. PMVMs usually suffer from inherent low power factors, limiting their performance, but the introduction of winding switching is shown to be an effective method in reducing the required inverter capacity for high-speed operation. Transmission results for 110 km. PAGE 1091 A phase improvement algorithm for designing nonlinear frequency modulated (NLFM) signals has been put forward by researchers in Iran. Simulation results demonstrate a significant improvement over the stationary phase method with the minimum error in each iteration being reduced. Topology of dual 3-phase machine. PAGE 1082 Free-space optical transmission of high-speed 120 Gb/s wavelength division multiplexing signals has been performed by researchers in China. The signals were transmitted in a 1 km outdoor atmospheric channel with high free optical-space quality demonstrating that they are suitable for use in long-distance high-speed optical transmissions. Minimum error against number of iterations. Experimental setup of the transmission through a 1 km atmospheric channel.

Shape-preserving and unidirectional frequency conversion by four-wave mixing

In this work, we investigate the properties of four-wave mixing Bragg scattering driven by orthogonally polarized pumps in a birefringent waveguide. This configuration enables a large signal conversion bandwidth, and allows strongly unidirectional frequency conversion as undesired Bragg-scattering processes are suppressed by waveguide birefringence. Moreover, we show that this form of Bragg scattering preserves the (arbitrary) signal pulse shape, even when driven by pulsed pumps.

Testing of a sCVD diamond detection system in the CROCUS reactor

The paper describes the testing of the NEUTON detection system into CROCUS, the zero-power reactor of the Ecole Polytechnique Federale de Lausanne (EPFL). NEUTON is composed of a $4 {\rm mm} \times 4$ mm sCVD diamond detector with a 6Li converter and the associated acquisition electronics. It is developed by CIVIDEC Instrumentation GmbH. The use of a diamond detector with converter in the mixed radiation field of a nuclear reactor is challenging because these detectors are sensitive to gamma-rays, fast neutrons and thermal neutrons through conversion in 6Li . In NEUTON, the rejection of gamma-rays is achieved in real time, via the analysis of the signal pulse shape from the detector. To do so, a few signal characteristics (amplitude, area and FWHM) are recorded in the integrated Field Programmable Gate Arrays (FPGA) of the system. This treatment does not induce any dead time. Measurements in CROCUS demonstrated for the first time the capability of a system like NEUTON to detect and separate fast neutrons, thermal neutrons, and gamma-rays. The system response was shown to be linear with respect to the reactor power (up to 35W) and its thermal sensitivity was found to be $(3.5\pm 0.2)\times 10^{-5}$ cps/nv.