Coincidence Method Research Articles

IMPLEMENTATION OF THE COINCIDENCE FREQUENCY METER ON FPGA

Means of measuring various parameters and technical characteristics of radio equipment have always occupied leading positions in science and technology. Without an accurate definition of the relevant values, it is impossible to build modern high-quality radio communication systems, radar, navigation ground and satellite systems. In ultrasound diagnostics, which are used in medicine, the speed of blood flow in vessels is studied by determining the frequency of the reflected signal. At the same time, it is necessary to use high-speed frequency measurement tools in systems with active sensors used in telecommunication networks based on Internet of Things technology. For example, in active radar, using the frequency of the reflected signal, it is possible to calculate not only the coordinates, but also the circular speed of the moving target. Modern research is aimed at improving the metrological and technical indicators of existing measuring devices, in particular at developing new methods for correcting the characteristics of the transformation of the measuring channel, which is their main component. At the same time, most digital frequency meters are built on the method of counting the number of pulses N with an unknown period Tx that arrive at the input of the device during a calibrated time interval. All this leads to an increase in measurement time and requires additional hardware costs for fast processing of measurement results. The coincidence method belongs to vernier methods and is promising for use when measuring the frequency of periodic signals. This paper points out the shortcomings of known methods of measuring the frequency of a periodic signal. On the basis of the well-known method of coincidence, a functional scheme of a 16-bit device for measuring frequency, which is implemented on the basis of a FPGA from Intel (Altera), has been developed. The developed coincidence frequency meter has a dynamic range of 96dB. Representation of time diagrams obtained in the Quartus Prime 18.0 automated design environment and confirming the operability of the developed functional scheme of the 16-bit device for frequency measurement by the coincidence method. An analytical dependence for determining the frequency of a periodic signal during frequency measurement by the coincidence method is presented.

In-Cites research fronts and its relationship with citations per document and highly cited papers: Spanish universities as a case study

Research fronts (RFs) represent the most dynamic areas of science and technology and the topics that receive higher attention in a specific field. Their identification has become the focus of global scientific and technological competition. In this study, we performed an analysis of the In-Cites RFs from Web of Science (WoS) in seven Spanish universities as a case study in the period 2015–2019. Our purpose is threefold: (1) to develop a methodology for approximating the ‘alignment’ of scientific articles with the RFs, (2) to test if Highly Cited Papers (HCP) from these universities are more aligned with RFs than the rest of the output, and (3) to test if papers aligned with RFs receive more citations per document than those not aligned. The study uses a novel retrieval method, and the analysis is conducted using a coincidence method (comparison with a standard), in which Mann–Kendall’s test and Pearson’s correlation are used. The results show that there is alignment between output and the HCP and those better aligned, present greater mean ranks of citations per article. This study shows the usefulness of RFs for orienting the research priorities at the institutional level for the university.

A double photon coincidence detection method for medical gamma-ray imaging

Abstract Cascade nuclides emit two or more gamma rays successively through an intermediate state. The coincidence detection of cascade gamma rays provides several advantages in gamma-ray imaging. In this review article, three applications of the double photon coincidence method are reviewed. Double-photon emission imaging with mechanical collimators and Compton double-photon emission imaging can identify radioactive source positions with their angular-resolving detectors, and reduce the crosstalk between nuclides. In addition, a novel method of coincidence Compton imaging is proposed by taking coincidence detection between a Compton event and a photopeak events. Although this type of coincidence Compton imaging cannot specify the location, it can be useful in multi-nuclide Compton imaging.

Efficiency calibration and self-attenuation correction in radioxenon measurement using β-γ coincidence method

Measurement of the four radioxenon isotopes, namely 131mXe, 133mXe, 133Xe, and 135Xe, play a key role in underground nuclear test monitoring for ensuring compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). To improve detection sensitivity, a β-γ coincidence technique is commonly used. Due to the presence of the gas matrix, such as stable xenon, nitrogen, helium, the self-attenuation effects should be taken into account when measuring different types of sample. In order to improve the accuracy of the measurement, the detection efficiencies of X-rays and γ-rays were derived by using a simulation gas calibration source with low density of sponge matrix. The detection efficiencies of β-particles and conversion electrons (CEs) were calibrated by measuring radioxenon sample. The self-attenuation correction factors of X-rays and γ-rays were determined by Geant4 simulation method. The self-attenuation correction factors of β-particles and CEs were provided by measuring the radioxenon samples with different volumes of xenon, nitrogen and helium.

A four-channel coincidence digital positron annihilation lifetime spectrometer

Positron annihilation lifetime (PAL) spectrometer is an effective tool to investigate material microstructures. Commonly used PAL spectrometers are conventional PAL spectrometer based on nuclear instrument modules (NIMs) and digital PAL spectrometer based on ultra-high-speed digitizer. Limited by the detection efficiency of the detectors, the coincidence count rate of the PAL spectrometer is always low, causing long time consumption of measurement. To solve this problem, a multi-channel coincidence method based on the ultra-high-speed digitizer was proposed. However, the ultra-high-speed digitizer is usually excessively expensive for research institutes. In this paper, we introduce a four-channel coincidence digital PAL spectrometer. Through the improvement of the timing and trigger circuit, all channels can act as start and stop channels during one measurement. Hence the coincidence count rate can be increased by an order of magnitude. The time measurement shows good linearity and high resolution with a full width half maximum (FWHM) at a level of several tens picoseconds. The effective number of bits (ENOB) of the analog-to-digital converter (ADC) reaches 10.72 bits. The energy resolution of the 511 keV photopeak reaches 4.16% when using LaBr 3: 5% Ce3+ scintillator, better than 4.62% of the conventional spectrometer. The time resolution of our PAL spectra when one channel receives start signals and one channel receives stop signals reaches 193.7 ps, better than that of the conventional spectrometer (212.8 ps). The FWHMs of the lifetime spectra of the two and four channel coincidence measurements are 205.8 ps and 212.4 ps respectively. Moreover, the coincidence count rate of our system increases significantly by using the four-channel coincidence method, which can be 10 times higher than the conventional spectrometer.

Exploring the intrinsic energy resolution of liquid scintillator to approximately 1 MeV electrons

We propose a novel method for exploring the intrinsic energy resolution of a liquid scintillator (LAB + 2.5 g/L PPO + 3 mg/L bis-MSB) to approximately 1 MeV electrons. With the help of coincidence detection technology, single-energy electrons of 207Bi were effectively selected. With a careful measurement and analysis of the energy resolution of a small liquid scintillator detector, the intrinsic energy resolution of the liquid scintillator to 976 keV electrons was extracted to be 1.83% ± 0.06%. We used the wide-angle Compton coincidence (WACC) method to measure the luminescent nonlinearity of a liquid scintillator and found that it contributes only weakly to the intrinsic energy resolution of electrons. Such an unexpected large intrinsic energy resolution may come from fluctuations in energy transfer processes.

Charge-encoded multi-photoion coincidence for three-body fragmentation of CO2 in the strong laser fields.

The photoion-photoion coincidence (PIPICO) is a simple and effective approach for the selection of correlated fragments in a specific dissociating channel in molecules. We propose here a charge-encoded multi-photoion coincidence (cMUPICO) method, in analogy to traditional PIPICO, however in which the charge of individual fragments is taken into account. The cMUPICO method allows for clearly displaying coincident channels for dissociation channels containing three more fragments with unequal charge states, invisible in the traditional PIPICO. As a demonstration, three-body fragmentation dynamics of CO2 in strong IR laser fields is analyzed, and 11 dissociation channels are effectively identified, five of which are first found with cMUPICO. The present results show that cMUPICO is a powerful and practical tool for distinguishing various dissociation channels with multiply charged multi-photoions.

Significance of Product Purchase unaffected by Place of Business

Purpose: This study aimed to determine factors influencing consumers’ decision to buy products and prove whether the place of business is an important factor for consumers to decide to buy products. The variables used in this study were 1) price, location and social media, 2) product quality, price, location and social media.
 Design/methodology/approach: This is a quantitative study with an unknown population. Samples were consumers who incidentally make a purchase at Kober Mie Setan in Surabaya. Sampling technique was coincidence method with a sample of 90 respondents. The data collection technique is a questionnaire with tested validity and reliability. The data analysis technique used to answer the hypothesis is multiple regression.
 Findings: The results of this study indicate that (1) simultaneous test indicated that the variables of product quality, price, location and social media had a significant effect on consumer purchasing decisions at Kober Mie Setan in Surabaya. This is evidenced by a significance value of 0.000 0.05 and (2) partial test results show that location variable had no positive and significant effect while the product quality, price, and social media variables had a significant effect on consumer purchasing decisions at Kober Mie Setan in Surabaya. This is evidenced by the significance value of 0.383 > 0.05. Product quality variable had a significant effect with a significance value of 0.000 0.05. Price variable had a significant effect with a significance value of 0.002 0.05 and social media has a significant effect with a significance value of 0.014 0.05.
 Originality/value: This paper is original.
 Paper type: Research paper

Research on leak monitoring of the primary circuit of a pressurized water reactor based on the 13N coincidence method

To assess the characteristics of 13N decay, a monitoring method of the primary loop leakage rate based on the ?-? coincidence method was proposed. In this work, sampling and measurement devices were designed, in which NaI (Tl) crystals were used as coincidence detectors. The Geant4 simulation method was used to study the relationship between the efficiency e and capacity V change of different devices, and the eV value under the corresponding capacity was obtained. According to the value of eV, the optimal sampling and measurement device was determined, and then the detection efficiency of the device was calibrated experimentally. Taking the 600 000 kW reactor of Qinshan Phase II as the research object, the lower limit of detection was discussed. When the sampling point was located in the fume hood of the control rod drive mechanism, the theoretical lower limit of the coincidence method was 0.756 Lh-1.

Electron-induced dissociation dynamics studied using covariance-map imaging.

Recently, covariance analysis has found significant use in the field of chemical reaction dynamics. When coupled with data from product time-of-flight mass spectrometry and/or multi-mass velocity-map imaging, it allows us to uncover correlations between two or more ions formed from the same parent molecule. While the approach has parallels with coincidence measurements, covariance analysis allows experiments to be performed at much higher count rates than traditional coincidence methods. We report results from electron-molecule crossed-beam experiments, in which covariance analysis is used to elucidate the dissociation dynamics of multiply-charged ions formed by electron ionisation over the energy range from 50 to 300 eV. The approach is able to isolate signal contributions from multiply charged ions even against a very large 'background' of signal arising from dissociation of singly-charged parent ions. Covariance between the product time-of-flight spectra identifies pairs of fragments arising from the same parent ions, while covariances between the velocity-map images ('recoil-frame covariances') reveal the relative velocity distributions of the ion pairs. We show that recoil-frame covariance analysis can be used to distinguish between multiple plausible dissociation mechanisms, including multi-step processes, and that the approach becomes particularly powerful when investigating the fragmentation dynamics of larger molecules with a higher number of possible fragmentation pathways.

Development of a triple coincidence method of reaction, gamma-ray, and weak decay in the hypernuclear gamma-ray spectroscopy at J-PARC

To understand the mechanism of the charge symmetry breaking between 4ΛH and 4ΛHe, we plan to measure the gamma-transition energy of 4ΛH (1+ → 0+) with a Ge detector array. For identification of the hypernucleus, we will perform triple coincidence with the reaction, γ-ray, and weak decay for the first time. We measure the pion from weak decay with a range counter. This method will enable γ-ray spectroscopy of various hyperfragments which cannot be directly produced by (K−, π−) or (π+, K+) reactions.

Method of multiscale coincidence of pulses for measuring temporary loads from moving vehicles in bridges and overpasses

Modern development of road transport is characterized by constant updating of the nomenclature of cars (including heavy-duty vehicles), by increasing of intensity and speed of their movement, especially in large metropolises and on roads of national and local significance. This complicates the operating conditions of spans of highway bridges to some extent, leads to their damage and early wear. The deterioration of the technical condition of the structures of the spans is largely due to the increased dynamic impact of the cars on the bridges. The purpose of this article is to measure the amplitude of oscillations of a bridge structure from temporary loads of rolling stock with non-periodic long-term loading by optical methods. In accordance with this goal, it is necessary to develop a technique and device for measuring the amplitude of oscillations of the bridge structure by converting the amplitude of oscillations in time intervals and their subsequent measurement by multi-scale pulse coincidence. In a number of works, digital deployment systems that use number systems with different bases, represented by a family of deployment functions, are considered in detail.
 Such digital systems in general, are described by the corresponding operating scheme. According to this operating scheme, a method of multiscale matching for measuring time intervals was developed, which formed the basis for measuring the vibration amplitude of the bridge structure. The given mathematical model of calculation of the number of measurement channels was used in the synthesis of velocity transducers and linear displacements based on optical (laser) deployment systems, information conversion devices of radar velocity sensors based on the Doppler effect. Similarly, a frequency comparison device, a digital frequency meter, a digital phase meter, and a number of other frequency-time group devices were synthesized.

Testing for the continuous spectrum of x rays predicted to accompany the photoejection of an atomic inner-shell electron

Echoing classical physics, quantum electrodynamics predicts the release of a spectral continuum of electromagnetic radiation upon the sudden acceleration of charged particles in quantum matter. Despite apparent theoretical success in describing sister nuclear processes, known as internal bremsstrahlung, following nuclear beta decay and K capture, the situation of the photoejection of an electron from an inner shell of an atom, intraatomic bremsstrahlung (IAB), is far from settled. In this paper we present fresh measurements which rely on contemporary signal processing as well as the high flux available from a synchrotron radiation source to revisit the problem by photoejecting electrons from the innermost shell of copper. For the first time we have sufficient sample statistics to measure the expected spectra at the level expected by contemporary theory. Furthermore, we employ sufficiently thin targets to overcome secondary scattering artifacts. Our approach applies the fluorescence coincidence method to guard against extraneous scattering and multiple incident photon processes. Our observations set a severe upper limit on the rate for IAB: We conclude that current theory overpredicts, by at least 5 sigma, the measured rate for K shell IAB in copper in the range of detected energies below the K fluorescence energy.

On the determination of neutron multiplication by the Rossi-alpha method

Introduction. This work contains the results of determining the prompt neutron multiplication factor in the subcritical state of a one-core BFS facility, obtained by the neutron coincidence method, for which the influence of the error in the βeff in determining the multiplication factor turned out to be insignificant. The core of the facility consisted of rods filled with pellets of metallic depleted uranium, 37% enriched uranium dioxide and 95% enriched plutonium, sodium, stainless steel and Al2O3. Stainless steel served as a reflector. Methods. In contrast to the inverse kinetics equation solving (IKES) method, which is convenient for determining reactor subcritical states, the neutron coincidence method practically does not depend on the error in the value of the effective fraction of delayed neutrons βeff. If in the IKES method the reactivity value is obtained in fractions of βeff, i.e., from the measurement of delayed neutrons, the neutron coincidence method is based on the direct measurement of the value (1 – kσp)2, where is the effective multiplication factor by prompt neutrons. The total multiplication factor is defined as keff = kσp + βeff. If, for example, keff ≈ 0.9 (which is typical for determining the fuel burnup campaign), then it is the error in determining kσp that is the main one in comparison with the error in βeff. Thus, a 10% error in βeff of 0.003–0.004 (typical for plutonium breeders) will make a contribution to the error 1 – keff equal to 1 – kσp + βeff ≈ 0.00035, i.e., approximately 0.35%, but not 10%, as in the IKES method. Rossi-alpha measurements were carried out using two 3He counters and a time analyzer. The measurement channel width Δt was 1.0 μs. From these measurements, the value of the prompt neutron multiplication factor was obtained. In this case, the space-isotope correlation factor for the medium with a source was calculated using the following values: Φ(x) – solutions of the inhomogeneous equation for the neutron flux and Φ+(x) – solutions of the ajoint inhomogeneous equation. Results. The authors also present a comparison of the results of the Rossi-alpha experiment and measurements of the BFS-73 subcritical facility by the standard IKES method in determining the multiplication factor value. The data of the IKES method differ insignificantly from the results of the Rossi-alpha method over the entire range of changes in the subcriticality with an increase in the subcriticality of the BFS-73 one-core facility. Conclusion. It was impossible to apply the neutron coincidence method to fast reactors; however, the method turned out to be quite workable on their models created at the BFS facility, which was successfully demonstrated in this study.

Auger cascade initiated by the Coster–Kronig transition from the Kr 3p core-hole states

The full Auger cascade initiated by the M2,3M4,5N Coster–Kronig (CK) transitions from the Kr 3p core-hole states is revealed by using a multi-electron coincidence method. The individual CK transitions are located on the basis of the energy correlations between the Auger electrons emitted in the CK and secondary Auger transitions. The decay processes of the CK-final Kr2+ states are investigated, whereby two-electron emissions leading to the formation of Kr4+ levels are identified.

Performance evaluation of a beta-spectrometer comprising a plastic scintillator and multi-wire chamber using a coincidence method

This paper describes an experimental setup developed to measure the beta-ray energy spectrum as well as a Geant4 simulation study conducted to characterize the properties of a beta-spectrometer. The beta-spectrometer comprises a multi-wire chamber to generate signals to indicate the incidence of beta rays and a plastic scintillation detector to measure its energy. The coincidence method of the detector signals was used to remove high gamma-ray interference. To evaluate the performance of the developed spectrometer, the energy spectra were measured with the radionuclide sources (137Cs and 207Bi) emitting internal conversion electrons and gamma rays. The gamma-ray interference removal rate of the spectrometer using the coincidence method was 99.12 ± 0.09%. To reconstruct the beta spectrum from the measured spectrum, Monte Carlo simulations using the Geant4 toolkit were performed to calculate the coefficient related to the effect of gamma rays. The obtained spectrum confirmed that the energy resolution and intrinsic internal conversion peak detection efficiency of the beta-spectrometer were 10.2% at 1 MeV and 91.6%, respectively.

Simultaneous multi-nuclide imaging via double-photon coincidence method with parallel hole collimators

Multi-tracer imaging can provide useful information in the definitive diagnosis and research of medical, biological, and pharmaceutical sciences. Single-photon emission computed tomography (SPECT) is one of the nuclear medicine imaging modalities widely used for diagnosis or medical research and has a multi-tracer imaging capability. One of the drawbacks of multi-tracer imaging is crosstalk from other gamma rays, which affects the reconstructed image. Scattering correction methods, such as the dual- and triple-energy window methods, are used for conventional SPECT imaging to reduce the background caused by the crosstalk. This study proposes another crosstalk reduction method. Some nuclides emit two or more gamma rays through intermediate levels. Thus, detecting these gamma rays with the coincidence method allows us to distinguish a true gamma ray signal and a background signal. The nuclide position can be estimated at the intersection of two gamma rays using collimators. We demonstrate herein simultaneous 111In and 177Lu imaging via the double-photon coincidence method using GAGG detectors and parallel hole collimators. The double-photon coincidence method greatly reduces the background caused by other gamma rays and offers higher-quality images than does conventional imaging.

Identification of Auger mechanisms responsible for low energy electron emission from graphene on copper using Auger-gamma coincidence spectroscopy

We have applied positron annihilation induced Auger-gamma coincidence spectroscopy to identify important mechanisms responsible for the emission of low energy electrons following the sudden creation of holes in bilayer graphene on copper substrate. The novel surface spectroscopic method measures the energy of the Doppler shifted annihilation gamma photon in coincidence with the Auger electron emitted following the relaxation of the hole created by the annihilation of a surface electron with a surface trapped positron. By extracting and theoretically modelling the annihilation gamma spectra coincident with low energy electrons, we associate majority of the intensity in the low energy (7 eV–25 eV) region of the Auger spectrum to electron emission following Auger decays of 2s holes in adsorbed oxygen and deep valence holes in graphene. We provide additional support to this conclusion by showing that most of the Auger electrons with energy less than ∼ 25 eV are coincident with gamma photons with small Doppler shift (511 keV–512 keV) indicating that the primary electron whose annihilation resulted in low energy Auger electron emission had small momentum parallel to the gamma emission direction. On the other hand, majority of the Auger electrons measured in coincidence with the photons having maximum Doppler shift (515 keV–521 keV) were emitted following the decay of core holes (C 1s and O 1s). By selecting annihilation gamma photons coincident only with the O KVV (from surface adsorbed oxygen), C KVV (graphene), and Cu MVV (copper substrate) Auger electrons, we have also experimentally derived the energy spectrum of Doppler shifted gamma photons resulting from the annihilation of positrons with 1s electrons of O, 1s electrons of C and 3p electrons of Cu respectively. Model Doppler broadened gamma spectra produced using ab-initio calculations agree well with the experimentally derived line shapes. This demonstrates the ability of Auger-gamma coincidence method to experimentally resolve the Doppler broadened annihilation gamma spectrum from surfaces into its veiled electronic level constituents which has, heretofore, relied solely on theoretical analysis. Our results also demonstrate that the line shape of the Doppler broadened annihilation gamma peak reflect the chemical composition of the topmost atomic layer and can thus be used to characterize both external and inaccessible surfaces of porous materials.

Effect of gamma window setting on activity measurement of 134Cs by 4πβ(LS)-γ coincidence method

Effect of gamma window setting on activity measurement of 134Cs by 4πβ(LS)-γ coincidence method

Development of the readout system for SiPM-scintillator-based muography devices

Muography is a promising imaging method to detect the heavily-shielded materials, large buildings and geological structures. The expansion of the sensitive area and the improvement of the detection accuracy propose strict requirements on the readout system, including large channel number, high integration and low noise. In particular, for the SiPM-scintillator-based technology which strongly relies on temperature, the readout system also needs to compensate for the temperature variation. This paper describes the design and implementation of a scalable readout system for the general muography devices based on SiPM-scintillator technology. A flexible cross-layer coincidence method is embedded in the system to screen out the muon events and further improve the detection efficiency. Self-performance measurements are carried out and the results show that the readout system is capable of outstanding spatial resolution and imaging results.