Coincidence Measurements Research Articles

Machine learning assisted quantum state estimation

We build a general quantum state tomography framework that makes use of machine learning techniques to reconstruct quantum states from a given set of coincidence measurements. For a wide range of pure and mixed input states we demonstrate via simulations that our method produces functionally equivalent reconstructed states to that of traditional methods with the added benefit that expensive computations are front-loaded with our system. Further, by training our system with measurement results that include simulated noise sources we are able to demonstrate a significantly enhanced average fidelity when compared to typical reconstruction methods. These enhancements in average fidelity are also shown to persist when we consider state reconstruction from partial tomography data where several measurements are missing. We anticipate that the present results combining the fields of machine intelligence and quantum state estimation will greatly improve and speed up tomography-based quantum experiments.

Discriminating Uranium Isotopes Based on Fission Signatures Induced by Delayed Neutrons

The use of active interrogation (AI) to induce delayed neutron emission is a well-established technique for the characterization of special nuclear materials (SNM). Delayed neutrons have isotope-characteristic spectral and temporal signatures, which provide the basis for isotope identification. However, in bulk materials that contain an appreciable fissile (e.g., $^{235}$U or $^{233}$U) fraction, such as highly-enriched uranium (HEU), delayed neutrons have a high probability of inducing additional fissions. As a result, the overall delayed neutron signature consists of two distinct components: the "primary" delayed neutrons (emitted directly by fission fragments), and the "secondary prompt" fission neutrons produced in fission induced by primary delayed neutrons. These prompt products differ from "primary" delayed neutrons both in their energy spectra and in the presence of coincident radiation released by the parent fission event. The presence and relative quantity of prompt products from delayed fission depend on the cross-section of the material in the energy range of delayed neutrons, which may differ significantly between isotopes, thus providing an exploitable means for isotope differentiation. In this work, we demonstrate two experimental approaches for discriminating between $^{235}$U and $^{238}$U isotopes based on the measurement of delayed neutron-induced fission products. First, HEU and depleted uranium objects are differentiated through the detection of high-energy prompt neutrons from delayed fission using both recoil-based organic liquid scintillators and thermalization spectra from a custom-built capture-gated composite detector. Secondly, coincident radiation measurements are used as the basis for discrimination by comparing the overall rates and time evolution of fission events when delayed neutrons are present.

Distortion-free frequency response measurements

We propose and experimentally demonstrate a distortion-free network analyzer (DFNA) using a noise source and an average power sensor for measuring the frequency property of an electronic device. DFNA makes use of the global algorithm and therefore typically save 60% measurements than conventional network analyzer which measures frequency response locally, under the same conditions. Furthermore, conventional network analyzer could be significantly affected by distortion due to its direct point-by-point scanning manner in frequency domain. In contrast, by utilizing the coincidence measurement principle, DFNA shows strong robustness against distortion. The results demonstrate that the proposed technique provides an efficient and robust way for anti-distortion frequency response analysis and has potential applications in communications, radio frequency circuits, radar and even electronic warfare.

Site-Adaptation of Modeled Solar Radiation Data: The SiteAdapt Procedure

The adaptation of modeled solar radiation data with coincident ground measurements has become a standard practice of the industry, typically requested by financial institutions in the detailed solar resource assessments of solar projects. This practice mitigates the risk of solar projects, enhancing the adequate solar plant design and reducing the uncertainty of its yield estimates. This work presents a procedure for improving the accuracy of modeled solar irradiance series through site-adaptation with coincident ground-based measurements relying on the use of a regression preprocessing followed by an empirical quantile mapping (eQM) correction. It was tested at nine sites in a wide range of latitudes and climates, resulting in significant improvements of statistical indicators of dispersion, distribution similarity and overall performance: relative bias is reduced on average from −1.8% and −2.3% to 0.1% and 0.3% for GHI and DNI, respectively; relative root mean square deviation is reduced on average from 17.9% and 34.9% to 14.6% and 29.8% for GHI and DNI, respectively; the distribution similarity is also improved after the site-adaptation (KSI is 3.5 and 3.9 times lower for GHI and DNI at hourly scale, respectively). The methodology is freely available as supplementary material and downloadable as R-package from SiteAdapt.

Monitoring the long term stability of civil buildings through the MRPC telescopes of the EEE Project

Cosmic ray muons are a penetrating component of extensive air showers created in the Earth atmosphere by the interaction of highly energetic primary particles, mostly protons, which continuously bombard our Planet. The secondary cosmic radiation is the result of the complex interplay between the production cross section and the interaction mechanisms with the atmosphere (including the energy loss, multiple scattering and particle decay). Cosmic muons have been considered since several decades as a powerful probe to exploit our environment, from muography of volcanoes to absorption radiography of possible hidden rooms inside large structures, such as Pyramids, to the detection of high-Z illicit nuclear materials inside containers and many other applications of social interest.This paper discusses the possibility to employ the Multigap Resistive Plate Chambers (MRPC) of the Extreme Energy Events (EEE) Project as muon tracking detectors to monitor the long term stability of civil buildings and structures when used in conjunction with additional detectors. For this application the average direction of the cosmic muon tracks passing through the MRPC telescope and an additional detector located some distance apart in the same building may be reconstructed with good precision and any small variation over long time acquisition periods may be monitored. The performance of such setup is discussed and experimental results from first coincidence measurements obtained with a 40 × 60 cm2 scintillator detector operated in the same building with one of the EEE telescopes, at about 15 m vertical distance from it, are presented. Simple Monte Carlo and GEANT simulations were also carried out to evaluate typical acceptance values for the operating conditions employed so far, to extrapolate to other geometrical configurations, and to evaluate multiple scattering effects.

Hybrid frequency-time spectrograph for the spectral measurement of the two-photon state.

In this Letter, a hybrid frequency-time spectrograph combining a tunable optical filter and a dispersive element is presented for measurement of the spectral properties of the two-photon state. In comparison with the previous single-photon spectrograph utilizing the dispersive Fourier transformation (DFT) technique, this method is advanced since it avoids the need for additional wavelength calibration and the electronic laser trigger for coincidence measurement; therefore, its application is extended to continuous wave (CW) pumped two-photon sources. The achievable precision of the spectrum measurement has also been discussed in theory and demonstrated experimentally with a CW pumped periodically poled lithium niobate (PPLN) waveguide-based spontaneous parametric down-conversion photon source. Such a device is expected to be a versatile tool for the characterization of the frequency entangled two-photon state.

Positive-Parity Linear-Chain Molecular Band in ^{16}C.

An inelastic excitation and cluster-decay experiment ^{2}H(^{16}C,^{4}He+^{12}Be or ^{6}He+^{10}Be)^{2}H was carried out to investigate the linear-chain clustering structure in neutron-rich ^{16}C. For the first time, decay paths from the ^{16}C resonances to various states of the final nuclei were determined, thanks to the well-resolved Q-value spectra obtained from the threefold coincident measurement. The close-threshold resonance at 16.5MeV is assigned as the J^{π}=0^{+} band head of the predicted positive-parity linear-chain molecular band with (3/2_{π}^{-})^{2}(1/2_{σ}^{-})^{2} configuration, according to the associated angular correlation and decay analysis. Other members of this band were found at 17.3, 19.4, and 21.6MeV based on their selective decay properties, being consistent with the theoretical predictions. Another intriguing high-lying state was observed at 27.2MeV which decays almost exclusively to ^{6}He+^{10}Be(∼6 MeV) final channel, corresponding well to another predicted linear-chain structure with the pure σ-bond configuration.

Energy calibration of HPGe detector using the high-energy characteristic $$\gamma$$ rays in 13C formed in 6Li + 12C reaction

An $${^6{\hbox {Li}}} + {^{89}{\hbox {Y}}}$$ experiment was conducted at the Laboratori Nazinali di Legnaro, INFN, Italy. The 550 $$\upmu$$g/cm$$^2$$ thick $$^{89}$$Y target was backed on a 340 $$\upmu$$g/cm$$^2$$ thick $${^{12}\hbox {C}}$$ foil. The several $$\gamma$$ rays in the experiment with energies higher than 3000 keV can most likely be ascribed to the transitions in the $${^{13}\hbox {C}}$$ nuclei, which can be formed through various interactions between the $${^{6}\hbox {Li}}$$ beam and the $${^{12}\hbox {C}}$$ foil. The high-energy properties of $$\gamma$$ rays in $${^{13}\hbox {C}}$$ are employed for energy calibrating HPGe detectors, especially for the $$>3000$$ keV region, which is impossible to reach by common standard sources ($$^{152}$$Eu, $$^{133}$$Ba, etc.). Furthermore, $$\gamma$$–$$\gamma$$ and particle–$$\gamma$$ coincidence measurements were performed to investigate the formation of $${^{13}\hbox {C}}$$.

A single-ion monitor based on coincident measurement of secondary electrons for single event effect research.

Single-ion monitoring is a key requirement for many energetic heavy-ion experiments, e.g., the laboratory simulation of the single event effect of semiconductor devices under heavy ion bombardments. We have developed a two-dimensional position-sensitive and timing monitor of individual ions. It is composed of a thin aluminum foil, a pair of microchannel plate detectors, and electrostatic and magnetic fields. When energetic heavy ions pass through the aluminum foil, secondary electrons generated on each side of the foil are guided by the fields to the corresponding detector. Both the hitting position and the arrival time of the secondary electrons on corresponding detectors are measured in coincidence. A test with an 241Am α source shows that the present monitor is capable of discriminating true events from heavy background radiations. A position resolution of 1.0 mm and a recording time resolution of 50 ns have been realized in the test.

Performance Assessment of Amplification and Discrimination Electronic Devices for Passive Neutron Measurements

The assessment of fissile material mass is a key requirement to enhance radioactive waste management and to ensure a high level of safety in the nuclear industry. The assessment of plutonium fissile mass by passive coincidence measurements is usually obtained by detecting the neutrons generated by the spontaneous fissions of Pu isotopes. The detection and the quantification of a fissile mass in the radioactive waste can also be carried out using active neutron interrogation with a pulsed D-T neutron generator. The 14-MeV neutrons are moderated to induce fissions in the uranium and plutonium-contaminated waste. The emitted neutron signal can be analyzed by considering their detection time after the generator pulse. Data are measured according to the principles of the neutron measurement techniques. As proportional counters filled with 3He gas display high neutron detection efficiency and good gamma-ray immunity, they are the reference detector for passive neutron coincidence counting. A charge preamplifier or a current amplifier, depending on applications, collects the electric pulse produced by neutron interaction in the 3He gas, and a threshold discriminator produces a logic pulse used for neutron counting. This article describes the performance assessment of different commercially-available electronics from Mirion Technologies, Precision Data Technology (PDT), Mesytec, as well as MONACO electronics originally developed by CEA LIST for fission chamber measurements in experimental reactors. Comparative passive neutron measurements are carried out with these electronics at CEA/DEN Nuclear Measurement Laboratory in Cadarache. Overall, PDT and Mesytec electronics show similar detection efficiency as the ACH-NA98 charge amplifier, which is commonly used in our laboratory for such applications. However, MONACO electronics have a lower detection efficiency, similar to the Mirion 7820 current amplifier used in specific high-count rate applications. An optimization of MONACO settings would probably be necessary to adapt to 3He counters instead of fission chambers.

Multiple Auger decays of core-excited states in N2.

Multi-electron coincidence measurements have been performed at the photon energies for the core-to-valence (1s → π*) and core-to-Rydberg (1s → 3sσ and 3pπ) resonant excitations in N2 in order to investigate the dynamics of multiple Auger-electron emissions from these core-excited states in detail. Peaks due to slow electrons from superexcited atomic fragments are observed in the decay processes by emission of two or three Auger electrons, indicating stepwise (cascade) multiple Auger decays that involve faster dissociations than electronic relaxations. Energy partitions between the emitted electrons enable us to reveal the detailed decay mechanisms for these processes. Branching ratios among the decays by emission of one, two, or three Auger electrons and those between the simultaneous (direct) and stepwise (cascade) processes have been determined for each of the core-excited states. Branching ratios of decay channels resulting in molecular or fragment ions have also been substantiated.

Determination of the cluster-decay branching ratio from a near-threshold molecular state in Be10

A puzzle has long existed for the $\alpha$-cluster content in the near-threshold 7.54 MeV state of $^{10}$Be. A new measurement was conducted to measure the cluster-decay partial width of this state, using the reaction $\rm{^9Be}(\rm{^9Be}, \rm{^{10}Be}^{*} \rightarrow \alpha + \rm{^6He})\rm{^8Be}$ at 45 MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-decay strength was also obtained based on the three-fold coincident measurement. A cluster-decay branching ratio of $(4.04 \pm 1.26)\times 10^{-4}$ is obtained, resulting in a reasonably large $\alpha$-cluster spectroscopic factor. The present work confirms the formation of the $\sigma$-bond molecular rotational band headed by the 6.18 MeV state in $^{10}$Be.

Novel coincidence setup using indigenously developed portable USB gamma spectrometer and associated analysis software

We present the development of a compact gamma spectrometer that is also capable of coincidence measurements, by connecting two units by a cable. The spectrometer consists of a CsI scintillator mated to a PIN photo-diode as the detector, a charge sensitive pre-amplifier, a shaping amplifier, and a 1024 bin Multi-Channel analyser. The assembly fits on a single PCB of dimensions 55mm x 105mm enclosed in a compact aluminum box. The USB powered plug and play design of the spectrometer makes it a highly portable surveying tool. While the pre-amplifier and shaping amplifier circuits are derived from schematics available in the open source domain, the MCA has been custom built. The data acquisition, analysis cum visualization software has been written in Python and is open sourced. A dual parameter list mode MCA capable of recording time stamped energy data from each of the individual gamma spectrometers including identification of coincident events was also developed for energy-gated coincidence measurements, and algorithms to visualize heat maps and surface plots of the obtained list mode data have been incorporated into the software.An FWHM of 81.2 keV was measured for the 1332 keV peak of 60Co. Two point calibration using the 1173 keV and 1332 keV peaks was carried out. The calculated calibration factors are applied to the 661.7 keV peak of 137Cs. The measured peak is at 661.3 keV, corresponding to 0.1% accuracy. However, a full-range linearity testing with a commercial pulser showed a non-linearity with a maximum value of 0.6%. The dead time of the electronics was measured using a pulse generator, and was found to be less than 20 microseconds. Photopeak efficiency of the detector measured with the 661.7 keV peak of 137Cs was found to be around 29%.In a novel approach, the MCA firmware has been modified to demonstrate non-energy gated gamma-gamma coincidence with no additional circuitry. The coincidence filtering has been verified with a 1μC 22Na source using a timing window of 400 ns.

Method for the diagnosis of aged plastic radiation portal monitors

The light collection efficiency of plastic scintillator panels used in radiation portal monitors (RPM) declines over time. We present an efficiency calibration procedure to measure the capability of an aged panel to detect 186 keV gamma rays of highly enriched uranium (HEU). The method is based on a coincidence measurement of backscattered Cs-137 gamma rays having an energy of 184 keV. Energy calibration of the plastic panel can be obtained from the same measurement.

Measurements with cosmic muons to monitor the stability of a civil building on a long time-scale

Due to their penetration capability, cosmic muons may provide a way to monitor the alignment and possible long term deformations of large structures, such as historical or other civil buildings. The basic idea behind this possibility is to look for any misalignment between position-sensitive detectors, fixed to different parts of the structure, relative to the original alignment condition. In this paper we discuss the possibility of employing Multigap Resistive Plate Chambers (MRPC) as tracking devices, operating them in coincidence with additional detectors without tracking capability. One of the MRPC telescopes (size 158× 82 cm2) of the Extreme Energy Events (EEE) project, installed in the underground floor at the Department of Physics and Astronomy in Catania, was used together with a 40× 60 cm2 scintillator-based detector, located at about 16 m vertical distance, on the third floor of the same building. Coincidence measurements were carried out over a period of about two months by shifting the position of the smaller detector, to mimic the movement of the structure. Plans for future studies with different detectors and under different geometrical configurations are also discussed.

Radiative electron capture to the continuum in U89++N2 collisions: Experiment and theory

For U89+ projectiles colliding at a beam energy of 75.91 MeV/u with a N2 target, we present a coincidence measurement between the cusp electrons emitted under an angle of 0∘ with respect to the projectile beam and the photons emitted under a polar angle of 90∘. This radiative-electron-capture-to-continuum cusp directly probes the theory of electron-nucleus bremsstrahlung up to the high-energy endpoint in inverse kinematics. In the present study, significant improvement with respect to the experimental accuracy has been achieved, resulting in a finer agreement between experimental and theoretical results.Received 10 December 2019Accepted 29 January 2020DOI:https://doi.org/10.1103/PhysRevA.101.022708Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasScattering of atoms, molecules, clusters & ionsScattering theoryAtomic, Molecular & Optical

Evaluation of the Crosta method for the retrieval of water quality parameters from remote sensing data in the Pearl River estuary

Abstract In recent decades, many algorithms have been developed for the retrieval of water quality parameters using remotely sensed data. However, these algorithms are specific to a certain geographical area and cannot be applied to other areas. In this study, feature-orientated principal component (PC) selection, based on the Crosta method and using Landsat Thematic Mapper (TM) for the retrieval of water quality parameters (i.e., total suspended sediment concentration (TSM) and chlorophyll a (Chla)), was carried out. The results show that feature-orientated PC TSM, based on the Crosta method, obtained a good agreement with the MERIS-based TSM product for eight Landsat TM images. However, the Chla information, selected using the feature-orientated PC, has a poor agreement with the MERIS-based Chla product. The accuracy of the atmospheric correction method and MERIS product may be the main factors influencing the accuracy of the TSM and Chla information identified by the Landsat TM images using the Crosta method. The findings of this study would be helpful in the retrieval of spatial distribution information on TSM from the long-term historical Landsat image archive, without using coincident ground measurements. This article has been made Open Access thanks to the kind support of CAWQ/ACQE (https://www.cawq.ca).

HIGH SPIN STRUCTURE OF 173Os

High-spin states in 173Os have been studied by γ-γ coincidence measurements following the 146Nd(32S,5n)173Os reaction. Four main sequences have been identified as the two signature branches of the bands built an the [642]5/2+ and [523]5/2- Nilsson states. Multi-polarity assignements have been derived utilizing the directional correlation (DCO) ratios aa well as the anisotropies of the γ-rays. B(M1)/B(E2) ratios have also been extracted to deduce farther information an the detailed structure of the bands

An improved air mass factor calculation for nitrogen dioxide measurements from the Global Ozone Monitoring Experiment-2 (GOME-2)

Abstract. An improved tropospheric nitrogen dioxide (NO2) retrieval algorithm from the Global Ozone Monitoring Experiment-2 (GOME-2) instrument based on air mass factor (AMF) calculations performed with more realistic model parameters is presented. The viewing angle dependency of surface albedo is taken into account by improving the GOME-2 Lambertian-equivalent reflectivity (LER) climatology with a directionally dependent LER (DLER) dataset over land and an ocean surface albedo parameterisation over water. A priori NO2 profiles with higher spatial and temporal resolutions are obtained from the IFS (CB05BASCOE) chemistry transport model based on recent emission inventories. A more realistic cloud treatment is provided by a clouds-as-layers (CAL) approach, which treats the clouds as uniform layers of water droplets, instead of the current clouds-as-reflecting-boundaries (CRB) model, which assumes that the clouds are Lambertian reflectors. On average, improvements in the AMF calculation affect the tropospheric NO2 columns by ±15 % in winter and ±5 % in summer over largely polluted regions. In addition, the impact of aerosols on our tropospheric NO2 retrieval is investigated by comparing the concurrent retrievals based on ground-based aerosol measurements (explicit aerosol correction) and the aerosol-induced cloud parameters (implicit aerosol correction). Compared with the implicit aerosol correction utilising the CRB cloud parameters, the use of the CAL approach reduces the AMF errors by more than 10 %. Finally, to evaluate the improved GOME-2 tropospheric NO2 columns, a validation is performed using ground-based multi-axis differential optical absorption spectroscopy (MAXDOAS) measurements at different BIRA-IASB stations. At the suburban Xianghe station, the improved tropospheric NO2 dataset shows better agreement with coincident ground-based measurements with a correlation coefficient of 0.94.

Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere

Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur. Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate.