Detector Surface Research Articles

Surface plasma resonance characteristics of cylindrical multilayer metal‐coated silicon nanoparticles

AbstractIn this article, the light scattering properties of cylindrical, three‐layer, silver‐coated silicon nanoparticles of the same size are investigated. Based on the T‐matrix methods, the light transmission and reflection characteristics of the multilayer structure are strictly derived. The scattering cross section (SCS) of the system and the near‐field Hz distribution are numerically calculated. The results show that surface plasmas (SPs) with different frequencies in the outer interface between the metal shell and air can be excited by the incident light and were resonant in different cavities formed by the silver‐coated silicon nanoparticles. When the incident light has higher frequencies, the SPs are excited at the inner interface between the silver shell and the silicon rod by the penetration of the light into the metal shell, and are resonant in the internal dielectric nuclei. These special SPs resonant phenomena have broad applications in the fields of surface plasma resonance sensors and detector.

Muscle Activity Detectors-Surface Electromyography in the Evaluation of Abductor Hallucis Muscle.

Despite the high availability of surface electromyography (sEMG), it is not widely used for testing the effectiveness of exercises that activate intrinsic muscles of foot in people with hallux valgus. The aim of this study was to assess the effect of the toe-spread-out (TSO) exercise on the outcomes of sEMG recorded from the abductor hallucis muscle (AbdH). An additional objective was the assessment of nerve conduction in electroneurography. The study involved 21 patients with a diagnosed hallux valgus (research group A) and 20 people without the deformation (research group B) who performed a TSO exercise and were examined twice: before and after therapy. The statistical analysis showed significant differences in the third, most important phase of TSO. After the exercises, the frequency of motor units recruitment increased in both groups. There were no significant differences in electroneurography outcomes between the two examinations in both research groups. The TSO exercise helps in the better activation of the AbdH muscle and contributes to the recruitment of a larger number of motor units of this muscle. The TSO exercises did not cause changes in nerve conduction. The sEMG and ENG are good methods for assessing this exercise but a comprehensive assessment should include other tests as well.

Using Deep Learning in Ultra-High Energy Cosmic Ray Experiments

The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible. For this reason all current and planned UHECR experiments detect cosmic rays indirectly by observing the extensive air showers (EAS) initiated by cosmic ray particles in the atmosphere. Various types of shower observables are analyzed in the modern UHECR experiments including a secondary radio signal and fluorescent light from the excited nitrogen molecules. Most of the data is collected by the network of surface stations which allows to measure the lateral EAS profile. The raw observables in this case are the time-resolved signals for the set of adjacent triggered stations. The Monte Carlo shower simulation is performed in order to recover the primary particle properties. In traditional techniques the MC simulation is used to fit some synthetic observables such as the shower rise time, the shower front curvature and the particle density normalized to a given distance from the core. In this talk we’ll consider an alternative approach based on the deep convolutional neural network trained on a large Monte-Carlo dataset, using the detector signal time series as an input. The above approach has proven its efficiency with the Monte-Carlo simulations of the Telescope Array Observatory surface detector. We’ll discuss in detail how the network architecture is optimized for this particular task.

Cosmic-Ray Anisotropies in Right Ascension Measured by the Pierre Auger Observatory

Abstract We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, , through a Fourier analysis in R.A. that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the “east–west” method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, %, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d ⊥ at the level of 1%–3%. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the R.A. of the Galactic center, at α GC = −94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin.

Probing dark matter freeze-in with long-lived particle signatures: MATHUSLA, HL-LHC and FCC-hh

Collider searches for long-lived particles yield a promising avenue to probe the freeze-in production of Dark Matter via the decay of a parent particle. We analyze the prospects of probing the parameter space of Dark Matter freeze-in from the decay of neutral parent particles at the LHC and beyond, taking as a case study a freeze-in Dark Matter scenario via the Standard Model Higgs. We obtain the projected sensitivity of the proposed MATHUSLA surface detector (for MATHUSLA100 and MATHUSLA200 configurations) for long-lived particle searches to the freeze-in Dark Matter parameter space, and study its complementarity to searches by ATLAS and CMS at HL-LHC, as well as the interplay with constraints from Cosmology: Big-Bang Nucleosynthesis and Lyman-α forest observations. We then analyze the improvement in sensitivity that would come from a forward detector within a future 100 TeV pp-collider. In addition, we discuss several technical aspects of the present Dark Matter freeze-in scenario: the role of the electroweak phase transition; the inclusion of thermal masses, which have been previously disregarded in freeze-in from decay studies; the impact of 2 → 2 scattering processes on the Dark Matter relic abundance; and the interplay between freeze-in and super-WIMP Dark Matter production mechanisms.

Search for PeV Gamma-Ray Emission from the Southern Hemisphere with 5 Yr of Data from the IceCube Observatory

Abstract The measurement of diffuse PeV gamma-ray emission from the Galactic plane would provide information about the energy spectrum and propagation of Galactic cosmic rays, and the detection of a pointlike source of PeV gamma-rays would be strong evidence for a Galactic source capable of accelerating cosmic rays up to at least a few PeV. This paper presents several unbinned maximum-likelihood searches for PeV gamma-rays in the Southern Hemisphere using 5 yr of data from the IceTop air shower surface detector and the in-ice array of the IceCube Observatory. The combination of both detectors takes advantage of the low muon content and deep shower maximum of gamma-ray air showers and provides excellent sensitivity to gamma-rays between ∼0.6 and 100 PeV. Our measurements of pointlike and diffuse Galactic emission of PeV gamma-rays are consistent with the background, so we constrain the angle-integrated diffuse gamma-ray flux from the Galactic plane at 2 PeV to 2.61 × 10−19 cm−2 s−1 TeV−1 at 90% confidence, assuming an E −3 spectrum, and we estimate 90% upper limits on pointlike emission at 2 PeV between 10−21 and 10−20 cm−2 s−1 TeV−1 for an E −2 spectrum, depending on decl. Furthermore, we exclude unbroken power-law emission up to 2 PeV for several TeV gamma-ray sources observed by the High Energy Spectroscopic System and calculate upper limits on the energy cutoffs of these sources at 90% confidence. We also find no PeV gamma-rays correlated with neutrinos from IceCube’s high-energy starting event sample. These are currently the strongest constraints on PeV gamma-ray emission.

Search for point sources of ultra-high-energy photons with the Telescope Array surface detector

ABSTRACTThe surface detector (SD) of the Telescope Array (TA) experiment allows us to detect indirectly photons with energies of the order of 1018 eV and higher, and to separate photons from the cosmic ray background. In this paper, we present the results of a blind search for point sources of ultra-high-energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers are separated from the hadron-induced extensive air shower background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment’s angular resolution for photons. The average 95 per cent confidence level upper-limits for the point-source flux of photons with energies greater than 1018, 1018.5, 1019, 1019.5 and 1020 eV are 0.094, 0.029, 0.010, 0.0073 and 0.0058 km−2yr−1, respectively. For energies higher than 1018.5 eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.

MC study for TALE Hybrid detector

The Telescope Array Low-energy Extension (TALE) Experiment is a hybrid air shower detector for observation of air showers induced by very high energy cosmic rays above 1016 eV. The TALE detector consists of a Fluorescence Detector (FD) station with ten FD telescopes and a surface detector (SD) array made up of 80 scintillation detectors. The TALE-FD and the TALE-SD array have been operational since 2013 and 2017 respectively. A triggering system of the TALE-SD using external triggering signals from the TALE-FD that is of a lower energy threshold, so called the hybrid trigger system, has been working since 2018. We evaluated the performance of hybrid mode of the TALE detector by using Monte Carlo simulation. Here we show analysis method for air shower events observed by the TALE hybrid detector and report the accuracies of air shower parameters.

Design and performance of the first IceAct demonstrator at the South Pole

In this paper we describe the first results of IceAct, a compact imaging air-Cherenkov telescope operating in coincidence with the IceCube Neutrino Observatory (IceCube) at the geographic South Pole. An array of IceAct telescopes (referred to as the IceAct project) is under consideration as part of the IceCube-Gen2 extension to IceCube. Surface detectors in general will be a powerful tool in IceCube-Gen2 for distinguishing astrophysical neutrinos from the dominant backgrounds of cosmic-ray induced atmospheric muons and neutrinos: the IceTop array is already in place as part of IceCube, but has a high energy threshold. Although the duty cycle will be lower for the IceAct telescopes than the present IceTop tanks, the IceAct telescopes may prove to be more effective at lowering the detection threshold for air showers. Additionally, small imaging air-Cherenkov telescopes in combination with IceTop, the deep IceCube detector or other future detector systems might improve measurements of the composition of the cosmic ray energy spectrum. In this paper we present measurements of a first 7-pixel imaging air Cherenkov telescope demonstrator, proving the capability of this technology to measure air showers at the South Pole in coincidence with IceTop and the deep IceCube detector.

Telescope Array search for EeV photons

We present the results of a search for point sources of photons with energies higher than 1 EeV based on the Telescope Array surface detector data for 9 years. No significant excess of photon signal over UHECR background was found. The photon-flux upper limits were set for each direction in the Telescope Array field of view as well as for stacked directions of dwarf spheroidal galaxies.

Rapid sub-micromolar amperometric enzyme biosensing with free substrate access but without nanomaterial signalling support: oxidase-based glucose detection as a proof-of-principle example.

High-sensitivity electrochemical glucose biosensing has so far been possible only through incorporation of nanomaterials into the glucose oxidase-(GOx) containing polymer layer on the detector surface. Here, as a conceptionally novel simplified option, pure gelatin thin films with covalently attached GOx were used to convert platinum (Pt) disk electrodes into rapidly responding amperometric glucose probes with a sub-micromolar limit of detection. The advanced enzymatic tools are easy to make and, as is crucial for a focus on waste minimization, green and sustainable, through restriction of sensor modification to readily available economical materials.

The Performance of Belle II High Level Trigger in the First Physics Run

The Belle II experiment is a new generation B-factory experiment at KEK in Japan aiming at the search for New Physics in a huge sample of B-meson decays. The commissioning of the accelerator and the detector for the first physics run has started from March this year. The Belle II High Level Trigger (HLT) is fully working in the beam run. The HLT is now operated with 1600 cores clusterized in 5 units, which is 1/4 of the full configuration. The software trigger is performed using the same offline reconstruction code, and events are classified into a set of physics categories. Only the events in the categories of interest are finally sent out to the storage. Live data quality monitoring is also performed on HLT. For the selected events, the reconstructed tracks are extrapolated to the surface of the pixel detector (PXD) and quickly fed back to the readout electronics for the real time data reduction by sending only the associated hits. The maximum trigger rate in the first physics run was 3.5kHz, and the Belle II data acquisition system was stably operated. There were several problems in the HLT operation, but they have successfully been fixed during the data taking period. The HLT reduction factor is measured to be 8 which is still higher than the design because of the high background environment.

Diamond Detector With Laser-Formed Buried Graphitic Electrodes: Micron-Scale Mapping of Stress and Charge Collection Efficiency

The paper reports the micron-scale investigation of an all-carbon detector based on synthetic single crystal CVD-diamond having an array of cylindrical graphitic buried-contacts, about $20~\mu \text{m}$ in diameter each, connected at the front side by superficial graphitic strips. To induce diamond-to-graphite transformation on both detector surface and bulk volume, direct-laser-writing technique was used. Laser-treatment parameters and cell shape have been chosen to minimize the overlapping of laser-induced stressed volumes. Optical microscopy with crossed polarizers highlighted the presence of an optical anisotropy of the treated material surrounding the embedded graphitized columns, and non-uniform stress in the buried zones being confirmed with a confocal Raman spectroscopy mapping. Dark current-voltage characterization highlights the presence of a field-assisted detrapping transport mainly related to highly-stresses regions surrounding buried columns, as well as superficial graphitized strips edges, where electric field strength is more intense, too. Notwithstanding the strain and electronic-active defects, the detector demonstrated a good charge collection produced by 3.0 and 4.5 MeV protons impinging the diamond, as well as those generated by MeV $\beta $ -particles emitted by 90Sr source. Indeed, the mapping of charge collection efficiency with Ion Beam Induced Charge technique displayed that only a few micrometers thick radial region surrounding graphitic electrodes has a reduced efficiency, while most of the device volume preserves good detection properties with a charge collection efficiency around 90% at 60 V of biasing. Moreover, a charge collection efficiency of 96% was estimated under MeV electrons irradiation, indicating the good detection activity along the buried columns depth.

Progress of the synthetic HCOOH laser diagnostic system on HL-2A tokamak

A synthetic formic-acid laser (HCOOH, λ=432.5 μm) diagnostic system, which includes a Michelson Interferometer, a Faraday-effect Polarimeter and a Far-forward collective scattering diagnostic, has been successfully developed on HL-2A tokamak for plasma operation and physics research. This paper describes the progress made to improve the diagnostic system: (1) For the Interferometer, the data processing/acquisition system was greatly improved, and the high-speed refractive memory card was firstly utilized in the real-time density feedback control. (2) For the Polarimeter, the main interference source of Faraday rotation angle measurement was identified to be the stay light, and preliminary result indicated that the stray light coming from the detector surface can be largely suppressed by using the optic-isolator which was made up of a polarizer and a quarter wave plate. (3) The newly developed Far-forward collective scattering diagnostic based on two circularly polarized waves was widely used to investigate broadband density fluctuations in recent experimental campaign.

New mathematical approach to calculate the geometrical efficiency using different radioactive sources with gamma-ray cylindrical shape detectors

The geometrical efficiency of a source-to-detector configuration is considered to be necessary in the calculation of the full energy peak efficiency, especially for NaI(Tl) and HPGe gamma-ray spectroscopy detectors. The geometrical efficiency depends on the solid angle subtended by the radioactive sources and the detector surfaces. The present work is basically concerned to establish a new mathematical approach for calculating the solid angle and geometrical efficiency, based on conversion of the geometrical solid angle of a non-axial radioactive point source with respect to a circular surface of the detector to a new equivalent geometry. The equivalent geometry consists of an axial radioactive point source with respect to an arbitrary elliptical surface that lies between the radioactive point source and the circular surface of the detector. This expression was extended to include coaxial radioactive circular disk source. The results were compared with a number of published data to explain how significant this work is in the efficiency calibration procedure for the γ-ray detection systems, especially in case of using isotropic radiating γ-ray sources in the form of point and disk shapes.

ANGULAR DEPENDENCE OF TRACK-ETCH DETECTOR HARZLAS TD-1.

Track-etched detectors are commonly used also for radiation monitoring onboard International Space Station. To be registered in track-etched detectors, the particle needs to meet several criteria-it must have linear energy transfer above the detection threshold and strike the detector's surface under an angle higher than the so-called critical angle. Linear energy transfer is then estimated from calibration curve from the etch rate ratio V that is calculated from parameters of individual tracks appearing on the detector's surface after chemical etching. It has been observed that V can depend on the incident angle and this dependence can vary for different detector materials, etching and evaluating conditions. To investigate angular dependence, detectors (Harzlas TD-1) were irradiated at HIMAC by several ions under angles from 0° to 90°. The correction accounting not only for critical angle but also for dependence of V on the incident angle is introduced and applied to spectra measured onboard International Space Station.

Appraisal of the ‘penumbra effect’ using lingual pulse oximetry in anaesthetized dogs and cats

ObjectiveFactors described as contributors to the ‘penumbra effect’ in relation to pulse oximetry include optical shunting, circulatory anastomoses and probe parallelity. This study aimed to clarify the main underlying mechanism involved. Study designProspective clinical trial. AnimalsA total of 30 dogs and 15 cats (client-owned). MethodsIn anaesthetized dogs and cats, a pulse oximeter probe was placed on the tongue to measure haemoglobin oxygen saturation (SpO2) and perfusion index. In 15 dogs, the probe was positioned at the root (baseline) of the tongue, then at 0.5 and 1 cm rostral to it, to investigate the effect of circulatory anastomoses on SpO2 values. In cats (which do not have lingual arteriovenous anastomoses), the probe was positioned at the root and apex of the tongue. To assess the effect of probe parallelity on SpO2 values in dogs, two lines were drawn parallel to the planes of the light-emitting diode and the detector surfaces and the intersection angle calculated using ImageMeter Pro, Google Play. In a further 15 dogs, the probe was placed at the tongue edge (0% optical shunt), with 50% optical shunt, then with the 50% optical shunt shielded. Data were analysed using Friedman’s test, Student t test and Pearson’s correlation coefficient (p < 0.05). ResultsIn dogs, SpO2 values were significantly higher at 1.0 cm than at baseline (p < 0.0001). In cats, there were no significant differences in SpO2 values at each location. There was no significant difference in SpO2 between 0% and 50% optical shunt in dogs. SpO2 had a moderate negative correlation with tongue thickness and negligible correlation with intersection angle. Conclusions and Clinical relevanceCirculatory anastomoses are probably responsible for observed changes in SpO2 as the probe is placed towards an extremity, rather than optical shunting or probe parallelity.

4π semiconductor beta-spectrometer for measurement of 144Ce – 144Pr spectra

Precision measurements of beta-spectra have always been and are still playing an important role in several fundamental physical problems, predominantly in neutrino physics. Magnetic and electrostatic spectrometers possess the superior energy resolution, but at the same time such devices appear to be very complex and large-scale setups. Since the electron free path at 3 MeV (which is, basically, the maximum beta-transition energy for long-living isotopes) does not exceed 2 g/cm3, solid state scintillation and ionization detectors were effectively employed for detection of electron. In case of semiconductor detectors there is a significant probability of back-scattering from the detector surface that depends on the detector material. This issue could be overcome by constructing a beta-spectrometer with 4π geometry, fully covering the source and capable of detecting backscattered electrons. Here we present a technology allowing production of a beta-spectrometer based on silicon detectors and having 4π geometry. The spectrometer developed had been fitted with a 144Ce-144Pr radioactive source and has demonstrated capability of performing precision beta-spectrometry for this nuclides.

Study of Muons in Ultra-High-Energy Cosmic-Ray Air Showers with the Telescope Array Experiment

One of the uncertainties in the interpretation of ultra-high-energy cosmic-ray (UHECR) data comes from the high-energy hadronic interaction models used for air shower Monte-Carlo (MC) simulations. A long-standing problem of the so-called “muon excess”, the discrepancy of number of muons predicted by simulations and observed in the data, is believed to be caused by the incompleteness of modern hadronic interaction models, all of which are known to use the extrapolated values of the parameters of hadronic interactions, such as cross sections and multiplicities. The present work is dedicated to the study of muon densities in UHE extensive air showers from the Telescope Array experiment surface detector data. In the 7-year-data from the Telescope Array experiment, we find that the number of particles observed for signals with an expected muon purity of ∼65% at a lateral distance of 2000 m from the shower core is 1.72 ± 0.10(stat.) ± 0.37(syst.) times larger than the MC prediction value using the QGSJETII-03 model for the proton-induced showers. A similar effect is also seen in comparison with other hadronic models such as QGSJETII-04, which shows a 1.67 ± 0.10 ± 0.36 excess. We also studied the dependence of these excesses on lateral distances and found a slower decrease of the lateral distribution of muons in the data as compared to the MC, causing larger discrepancy at the larger lateral distances.

Limits on point-like sources of ultra-high-energy neutrinos with the Pierre Auger Observatory

With the Surface Detector array (SD) of the Pierre Auger Observatory we can detect neutrinos with energy between 1017 eV and 1020 eV from point-like sources across the sky, from close to the Southern Celestial Pole up to 60̂ in declination, with peak sensitivities at declinations around ∼ −53̂ and ∼+55̂, and an unmatched sensitivity for arrival directions in the Northern hemisphere. A search has been performed for highly-inclined air showers induced by neutrinos of all flavours with no candidate events found in data taken between 1 Jan 2004 and 31 Aug 2018. Upper limits on the neutrino flux from point-like steady sources have been derived as a function of source declination. An unrivaled sensitivity is achieved in searches for transient sources with emission lasting over an hour or less, if they occur within the field of view corresponding to the zenith angle range between 60̂ and 95̂ where the SD of the Pierre Auger Observatory is most sensitive to neutrinos.