Detector Signal Research Articles

Classification of FIB/SEM-tomography images for highly porous multiphase materials using random forest classifiers

FIB/SEM tomography represents an indispensable tool for the characterization of three-dimensional nanostructures in battery research and many other fields. However, contrast and 3D classification/reconstruction problems occur in many cases, which strongly limits the applicability of the technique especially on porous materials, like those used for electrode materials in batteries or fuel cells. Distinguishing the different components like active Li storage particles and carbon/binder materials is difficult and often prevents a reliable quantitative analysis of image data, or may even lead to wrong conclusions about structure-property relationships. In this contribution, we present a novel approach for data classification in three-dimensional image data obtained by FIB/SEM tomography and its applications to NMC battery electrode materials. We use two different image signals, namely the signal of the angled SE2 chamber detector and the Inlens detector signal, combine both signals and train a random forest, i.e. a particular machine learning algorithm. We demonstrate that this approach can overcome current limitations of existing techniques suitable for multi-phase measurements and that it allows for quantitative data reconstruction even where current state-of the art techniques fail, or demand for large training sets. This approach may yield as guideline for future research using FIB/SEM tomography.

Distinguishing a stochastic gravitational-wave signal from correlated noise with joint parameter estimation: Fisher analysis for ground-based detectors

Search sensitivity to a stochastic gravitational-wave background (SGWB) is enhanced by cross-correlating detector signals. However, one of the most serious concerns is the environmental noise correlated between detectors. The global electromagnetic fields on the Earth, known as Schumann resonances, produce the correlated noise through the instrumental magnetic couplings. In this paper, we study the detectability of a SGWB in the presence of the correlated magnetic noise, using the Fisher analysis based on the analytical model of the correlated magnetic noise. We find that there is no significant degeneracy between the SGWB and noise parameters. Marginalizing over the correlated noise parameters degrades the constraint on each SGWB parameter by a factor of $\ensuremath{\sim}2$ at most in the four-detector case, irrespective of the strength of the magnetic coupling. We also confirm that the forecast results are robust against the variation of correlated noise parameters and can vary up to 40% in the realistic range of the coupling parameters for the second-generation detectors. However, ignoring the correlated noise in parameter estimation generally leads to a biased constraint on the SGWB parameters. If the coupling strength is twice as large as expected, this could result in a serious bias.

Mid-infrared acetone sensor for exhaled gas using FWA-LSSVM and empirical mode decomposition algorithm

The acetone can be regarded as one of the respiratory biomarkers for lung cancer, the detection of acetone in human exhaled gas has great important for early lung cancer screening. Based on Tunable Diode Laser Absorption Spectroscopy (TDLAS), a system for detecting acetone in exhaled gas has been developed, a multi-pass gas cell (MPGC), which has a 76 m effective absorption optical path, as well as a 7.32 μm quantum cascade laser (QCL) were adopted in the detection system. In order to confirm the function of the system, a gas distribution station equipped with standard concentrations of acetone was used. Empirical mode decomposition (EMD) algorithm as a spectral pre-processing algorithm was implemented to reduce the noise from the second harmonic signal (2f signal), using an orthogonal lock-in amplifier based on LabVIEW to demodulate the detector signal. Fireworks algorithm with the least squares support vector machine (FWA-LSSVM) was designed to improve the accuracy and sensitivity of acetone gas concentration inversion. The limits of detection (LoD) of the sensor system can be found the middle value of up to ∼ 21.4 parts per billion (ppb) with a 78 s integration time by Allan-Werle deviation analysis. The exhaled breath experiment showed that the sensor provides a promising way for the detection of acetone in human exhaled breath.

Technical note: Measurement of the bunch structure of a clinical proton beam using a SiPM coupled to a plastic scintillator with an optical fiber.

Recent proposals of high dose rate plans in protontherapy as well as very short proton bunches may pose problems to current beam monitor systems. There is an increasing demand for real-time proton beam monitoring with high temporal resolution, extended dynamic range and radiation hardness. Plastic scintillators coupled to optical fiber sensors have great potential in this context to become a practical solution towards clinical implementation. In this work, we evaluate the capabilities of a very compact fast plastic scintillator with an optical fiber readout by a SiPM and electronics sensor which has been used to provide information on the time structure at the nanosecond level of a clinical proton beam. A 3×3×3mm3 plastic scintillator (EJ-232Q Eljen Technology) coupled to a 3×3mm2 SiPM (MicroFJ-SMA-30035, Onsemi) has been characterized with a 70 MeV clinical proton beam accelerated in a Proteus One synchrocyclotron. The signal was read out by a high sampling rate oscilloscope (5 GS/s). By exposing the sensor directly to the proton beam, the time beam profile of individual spots was recorded. Measurements of detector signal have been obtained with a time sampling period of 0.8 ns. Proton bunch period (16 ns), spot (10 μs) and interspot (1 ms) time structures could be observed in the time profile of the detector signal amplitude. From this, the RF frequency of the accelerator has been extracted, which is found to be 64 MHz. The proposed system was able to measure the fine time structure of a clinical proton accelerator online and with ns time resolution.

Digital signal processing for neutron-gamma discrimination using a liquid scintillator detector

Digital signal processing has shown promise as a reliable approach for nuclear radiation spectroscopy. In this paper, the charge-to-digital conversion technique was applied to neutron-gamma discrimination. The method is based on the direct comparison of the charge at the fast and slow components of the anode signal of the scintillator detector. The performance of the technique was tested using experimental investigation by 252Cf source and D-D neutron generator. The minimum detectable energy for reasonable separation was found to be around 0.2 MeVee. The FOM of the discrimination parameter was maximized by the optimum selection of the charge integration parameters. Excellent discrimination between neutron and gamma signals was confirmed by the presented setup. The results confirmed that the presented technique can replace analog nuclear electronics conventionally uses for pulse shape discrimination.

Performance of Multipulse Pulse-Position Modulation in NLOS Ultraviolet Communications

The performance of multipulse pulse-position modulation (MPPM) in non-line-of-sight (NLOS) ultraviolet communications (UVC) with output signals of detectors following Poisson distribution and Poisson-triggered Gaussian (PTG) distribution has been investigated. Specifically, the probabilities of a given number of incorrectly identified pulsed or empty slots in an MPPM symbol have been derived with output signals Poisson and PTG distributed. Based on those probabilities, the expressions of symbol-error rate and achievable data rate of MPPM in the NLOS UVC systems have been further obtained. Finally, Monte-Carlo simulations are presented to verify the theoretical results.

Construction of a computational MDCT model for simulations of the detector signals

ObjectiveTo develop a computational model of a multi-detector CT scanner (MDCT), which could be used to simulate the signal of each detector element in the MDCT by using the Monte Carlo method. MethodsThe CT scanner was modelled, including the X-ray source, the bowtie filter, the collimator, the couch and the detector panel. Under a general scanning condition, the signal in each detector element was simulated based on the model by using the MCNPX code. Both the energy spectra at different tube voltages and energy deposition in the detector panel at different collimations were simulated to test the robustness of the MDCT model built in this study. Furthermore, the simulated signals in each detector element were compared with their recorded signals. The accuracies were evaluated by the relative root mean square error (RRMSE) and the structural similarity (SSIM) for each detector element and the whole detector panel, respectively. ResultsThe simulated energy spectra before and after passing through the phantom and simulated energy deposition in the detector panel were rational. In the scan range from the apex of lung to pubic symphysis, the RRMSE of the 18 axial projections ranged from 0.02 to 0.17, with an average of 0.08. And the SSIMs were calculated to be 0.979 and 0.976 for projections with the largest peak signal and the smallest peak signal, respectively. ConclusionsThe computational model of the MDCT developed in this study is accurate and successful, it is helpful for further accurate simulations of the radiation dose and image quality of the MDCT.

Sorted compressive sensing for reconstruction of failed in-core detector signals

Self-Powered Neutron Detectors(SPNDs) are used to calculate core power distributions, an essential factor in the safe operation of nuclear power plants. Some detectors may fail during normal operation, and signals from failed detectors are isolated from intact signals. The calculated detailed power distribution accuracy depends on the number of available detector signals. Failed detectors decrease the operating margin by enlarging the power distribution measurement error. Therefore, a thorough reconstruction of the failed detector signals is critical. This note suggests a compressive sensing based methodology that rationally reconstructs the readings of failed detectors. The methodology significantly improves reconstruction accuracy by sorting signals and removing high-frequency components from conventional compressive sensing methodology.

Medium and high energy electron detectors onboard BeiDou navigation satellite in MEO

Abstract This work introduces the instruments’ design of multi-directional medium-energy electron detector (energy range: 30–770 keV) and high-energy electron detector (energy range: 400 keV to 5.8 MeV) deployed on one of the BeiDou navigation satellites in medium earth orbit. Through the electromagnetic compatibility design, the problem of the detector signal being susceptible to electromagnetic interference is solved and the lower detection limit reaches a very low level of 20 keV. The proton contamination in the electron measurement can be effectively removed by designing the light-blocking layer and the logical working mode of the sensors. The detector circuits and sensor structure are optimized and the miniaturization of the instrument is realized. This study also introduces the calibration method of the detectors, and gives the ground test results, which can provide a basis for the on-orbit calibration and data processing of the instrument.

Concurrent surface enhanced infrared and Raman spectroscopy with single molecule sensitivity.

Surface enhanced infrared absorption (SEIRA) and surface enhanced Raman Spectroscopy (SERS) were simultaneously measured from the same location on plasmonically active substrates. The spectra were acquired using an optical photothermal infrared spectrometer coupled with a Raman spectrometer. The sensitivity of this approach enables exceptionally small quantities of molecules to be interrogated while providing complementary information from both infrared and Raman spectroscopy. This arrangement provides additional improvement of SEIRA through the enhancement of both the optical photothermal detector signal and the infrared absorption. The plasmonic substrates tested were silver nanospheres and a gold coated atomic force microscope tip. The concurrent acquisition of SEIRA and SERS is further demonstrated by nano-sampling material onto an atomic force microscope tip. The analytes, Buckminsterfullerene and 1,2-bis(4-pyridyl) ethylene, were analyzed individually and as mixtures. The concurrent acquisition of SERIA and SERS is a unique approach. It has general applications in trace surface analysis and for the analysis of returned planetary samples.

High-Performance and High-Fidelity GPU-Based Monte Carlo Solutions to the BEAVRS Benchmark

The BEAVRS benchmark is solved by PRAGMA, the graphics processing unit (GPU)–based continuous-energy Monte Carlo code. The solutions consist of the detailed simulation results for the two cycles that involve the reactivity and pin power distribution information for the zero-power physics tests and depletion. Primary results at hot zero power, such as the critical boron concentration at various rodded conditions, control rod bank worth, isothermal temperature coefficients, and assemblywise detector signal, are compared with the measured data. Core-follow calculations are performed with varied power, and the resulting boron letdown curves are compared with the measured one. Hot full-power depletion is also performed and the resulting pinwise power distributions of cycle 1 are compared with the nTRACER results. The comparison with the measured data and also with the nTRACER results demonstrates the high solution fidelity of PRAGMA. In all the calculations, PRAGMA uses a tremendously large number of histories, ranging from up to hundreds of millions per cycle, that are used to fully exploit the massive parallel computing capacity of GPUs. The execution time of the entire core-follow calculation with about 30 burnup steps takes less than 16 h on a single rack of computing nodes mounted with 24 gaming GPUs, which represents considerably high Monte Carlo core calculation performance.

Sparse denoising and adaptive estimation enhances the resolution and contrast of fluorescence emission difference microscopy based on an array detector.

An array detector allows a resolution gain for confocal microscopy by combining images sensed by a set of photomultipliers tubes (or sub-detectors). Several methods have been proposed to reconstruct a high-resolution image by linearly combining sub-detector images, especially the fluorescence emission difference (FED) technique. To improve the resolution and contrast of FED microscopy based on an array detector, we propose to associate sparse denoising with spatial adaptive estimation. We show on both calibration slides and real data that our approach applied to the full stack of spatially reassigned detector signals, enables us to achieve a higher reconstruction performance in terms of resolution, image contrast, and noise reduction.

Testing Model Predictions of Depth of Air-Shower Maximum and Signals in Surface Detectors using Hybrid Data of the Pierre Auger Observatory

We present a method for testing the predictions of hadronic interaction models and improving their consistency with observed two-dimensional distributions of the depth of shower maximum, X max, and signal at the ground level as a function of zenith angle. The method relies on the assumption that the mass composition is the same at all zenith angles, while the atmospheric shower development and attenuation depend on composition in a correlated way. In the present work, for each of the three leading LHC-tuned hadronic interaction models, we allow a global shift ∆ X max of the predicted shower maximum, which is the same for every mass and energy, and a rescaling R Had of the hadronic component at the ground level which is constant with the zenith angle. We apply the analysis to 2297 events reconstructed with both the fluorescence and surface detectors of the Pierre Auger Observatory with energies 1018.5−19.0 eV and zenith angles below 60°. Given the modeling assumptions made in this analysis, the best fit reaches its optimum value when shifting the X max predictions of hadronic interaction models to deeper values and increasing the hadronic signal. This change in the predicted X max scale alleviates the previously identified model deficit in the hadronic signal (commonly called the muon puzzle) but does not fully remove it. Because of the size of the adjustments ∆ X max and R Had and the large number of events in the sample, the statistical significance of need for these adjustments is large, greater than 5σstat, even for the combination of the systematic experimental shifts within 1σsys that are the most favorable for the models.

Расчет чувствительности детекторов для космического эксперимента Солнце-Терагерц"

The paper briefly describes the goals and objectives of the planned space experiment "Sun - Terahertz" aboard the Russian Segment of the ISS. The experiment is aimed at studying solar radiation in the unexplored terahertz range at frequencies of 1012…1013 Hz, obtaining new data on terahertz radiation from the sun, solar active regions and solar flares. The main components of the optical path of scientific equipment are considered. With the help of the Blackbody Simulator and the Single-Channel Model, the detectors of scientific equipment were calibrated, the influence of the quality of the optical surface of the telescope mirrors on the detector signal amplitude in the terahertz range was studied, and a preliminary assessment of the detector sensitivity was carried out.

Time-resolved dose rate measurements in pencil beam scanning proton FLASH therapy with a fiber-coupled scintillator detector system.

The spatial and temporal dose rate distribution of pencil beam scanning (PBS) proton therapy is important in ultra-high dose rate (UHDR) or FLASH irradiations. Validation of the temporal structure of the dose rate is crucial for quality assurance and may be performed using detectors with high temporal resolution and large dynamic range. To provide time-resolved in vivo dose rate measurements using a scintillator-based detector during proton PBS pre-clinical mouse experiments with dose rates ranging from conventional to UHDR. All irradiations were performed at the entrance plateau of a 250MeV PBS proton beam. A detector system with four fiber-coupled ZnSe:O inorganic scintillators and 20μs temporal resolution was used for dose rate measurements. The system was first characterized in terms of precision and stem signal. The detector precision was determined through repeated irradiations with the same field. The stem signal contribution was quantified by irradiating two of the detector probes alongside a bare fiber (fiber without a coupled scintillator). Next, the detector system was calibrated against an ionization chamber (IC) with all four detector probes and the IC placed in a water bath at 2cmdepth. A scan pattern covering 9.6×9.6cmwas used. Multiple irradiations with different requested nozzle currents provided instantaneous dose rates at the detector positions in the range of 7-1270Gy/s.The correspondence of the detector signal (in Volts) to the instantaneous dose rate (in Gy/s) was found. The instantaneous dose rate was calculated from the beam current and the spot-to-detector distance assuming a Gaussian beam profile at distances up to 8mmfrom the spot. Afterwards, the calibrated system was used in vivo, in mouse experiments, where mouse legs were irradiated with a constant dose and varying field dose rates of 0.7-87.5Gy/s.Theinstantaneous dose rate was measured for each delivered spot and the delivered dose was determined as the integrated instantaneous dose rate. The spot dose profile and PBS dose rate map were calculated. The dose contamination to neighbouring mice were measured together with the upper limit of the dose to the mouse body. The detectors showed high precision with ≤0.4% fluctuations in the measured dose. The stem signal exceeded 10% for spots <5mmfromthe optical fiber and >18mmfromthe scintillator. It contributed up to 0.2% to the total dose, which was considered negligible. All four detectors showed a non-linear relation between signal and instantaneous dose rate, which was modelled with a polynomial response function. In the mouse experiments, the measured scintillator dose showed 1.8% fluctuations, independent of the field dose rate. The in vivo measured spot dose profile had tails that deviated from a Gaussian profile with measurable dose contributions from spots up to 85mm from the detector. Neighbour mouse irradiation contributed ∼1% of the total mouse dose. The upper limit of the mouse body dose was 6% of the mouse leg dose. A fiber-coupled inorganic scintillator-based detector system can provide high precision in vivo measurements of the instantaneous dose rate if correction for the non-linear dose rate dependency is applied.

Phase-shifted demodulation scheme for fiber-optic interferometric sensors with combined waveform phase modulation

We propose and demonstrate a demodulation scheme for interferometric optical fiber sensing using combined waveform phase modulation. The method is based on a designed combined waveform and time-division separation technology, which moves the target signal to the sidebands of the carrier signal and eliminates the influence of residual direct current (DC) term and low-frequency intensity noise by filtering the detector signal directly. The effect of the modulation-to-target ratio (MTR) defined as the ratio of the modulation frequency to the target frequency on the demodulation results is also discussed. Both simulations and experiments verify the ability to obtain a pair of quadrature signals. The experimental results indicate that the phase resolution of the system is 1.1 × 10−6 rad/√Hz@2 kHz when the MTR is 625, and 5 × 10−6 rad/√Hz@2 kHz when the MTR is 25, while demonstrating excellent demodulation consistency. This work not only has the advantages of carrier modulation methods, but also does not need to generate analog signals for mixing, which provides guidance for high-sensitivity phase demodulation technology.

Secondary electron count imaging in SEM

Scanning electron microscopy (SEM) is a versatile technique used to image samples at the nanoscale. Conventional imaging by this technique relies on finding the average intensity of the signal generated on a detector by secondary electrons (SEs) emitted from the sample and is subject to noise due to variations in the voltage signal from the detector. This noise can result in degradation of the SEM image quality for a given imaging dose. SE count imaging, which uses the direct count of SEs detected from the sample instead of the average signal intensity, would overcome this limitation and lead to improvement in SEM image quality. In this paper, we implement an SE count imaging scheme by synchronously outcoupling the detector and beam scan signals from the microscope and using custom code to count detected SEs. We demonstrate a ∼30% increase in the image signal-to-noise-ratio due to SE counting compared to conventional imaging. The only external hardware requirement for this imaging scheme is an oscilloscope fast enough to accurately sample the detector signal for SE counting, making the scheme easily implementable on any SEM.

Performance of a convolutional autoencoder designed to remove electronic noise from p-type point contact germanium detector signals

We present a convolutional autoencoder to denoise pulses from a p-type point contact high-purity germanium detector similar to those used in several rare event searches. While we focus on training procedures that rely on detailed detector physics simulations, we also present implementations requiring only noisy detector pulses to train the model. We validate our autoencoder on both simulated data and calibration data from an ^{241}Am source, the latter of which is used to show that the denoised pulses are statistically compatible with data pulses. We demonstrate that our denoising method is able to preserve the underlying shapes of the pulses well, offering improvement over traditional denoising methods. We also show that the shaping time used to calculate energy with a trapezoidal filter can be significantly reduced while maintaining a comparable energy resolution. Under certain circumstances, our denoising method can improve the overall energy resolution. The methods we developed to remove electronic noise are straightforward to extend to other detector technologies. Furthermore, the latent representation from the encoder is also of use in quantifying shape-based characteristics of the signals. Our work has great potential to be used in particle physics experiments and beyond.

A non-dispersive infrared sensor for real-time detection of cyanogen chloride

Cyanogen chloride, as a systemic toxic agent, can cause death rapidly. In this paper, a non-dispersive infrared sensor was designed for the infrared absorption detection of cyanogen chloride at 800 cm-1. The roughness of the internal coating material was analyzed by experiments, and the gold-plated gas chamber was selected. The light path propagation of different cross-section gas chambers was simulated, and the circular section gas chamber was selected to increase the infrared detector signal. The effect of flow rate on voltage was studied. The standard curve between voltage and concentration was obtained under the optimal condition of 0.4 L min-1. The maximum response time was 19 s, and RSD was less than 2%. The interference experiment results showed that common gases entering the gas chamber do not cause interference. The non-dispersive infrared sensor for cyanogen chloride has good stability and detects cyanogen chloride in real-time.

A new brain dedicated PET scanner with 4D detector information

Abstract In this article, we present the geometrical design and preliminary results of a high sensitivity organ-specific Positron Emission Tomography (PET) system dedicated to the study of the human brain. The system, called 4D-PET, will allow accurate imaging of brain studies due to its expected high sensitivity, high 3D spatial resolution and, by including precise photon time of flight (TOF) information, a boosted signal-to-noise ratio (SNR). The 4D-PET system incorporates an innovative detector design based on crystal slabs (semi-monolithic) that enables accurate 3D photon impact positioning (including photon Depth of Interaction (DOI) measurement), while providing a precise determination of the photon arrival time to the detector. The detector includes a novel readout system that reduces the number of detector signals in a ratio of 4:1 thus, alleviating complexity and cost. The analog output signals are fed to the TOFPET2 ASIC (PETsys) for scalability purposes. The present manuscript reports the evaluation of the 4D-PET detector, achieving best values 3D resolution values of &lt;1.6 mm (pixelated axis), 2.7±0.5 mm (monolithic axis) and 3.4±1.1 (DOI axis) mm; 359 ± 7 ps coincidence time resolution (CTR); 10.2±1.5 % energy resolution; and sensitivity of 16.2% at the center of the scanner (simulated). Moreover, a comprehensive description of the 4D-PET architecture (that includes 320 detectors), some pictures of its mechanical assembly, and simulations on the expected image quality are provided.