Low-energy Particles Research Articles

Study on Correction Method of Counting Loss below the Threshold for Low Energy Radionuclides Based on Monte Carlo Simulation.

In the absolute measurement method of nuclide radioactivity by the internal gas proportional counter, the reasonable correction of the small pulse counting loss is the key to obtaining the measurement results accurately. Considering the decay type and energy of radioactive gas nuclides, the influence of the low-energy beta particles and the wall effect counting loss on the activity measurement results is different also. To this end, two typical radioactive gas nuclides ( 37 Ar and 3 H) are used to study the cause of counting loss based on the Monte Carlo simulation. The results show that the counting loss of small pulse in the activity measurement of 37 Ar comes mainly from the wall effect generated by x rays. Within the given gas pressure of 60-300 kPa, the simulated wall effect correction factors are 1.063-1.021. The decay energy of β particles generated by 3 H is very low, and there is no obvious wall effect. The small pulse counting loss mainly comes from the low-energy beta particles' contribution with the energy below the counting threshold, which can be corrected by extrapolating the beta energy spectrum at a lower counting threshold (below 1 keV).

Application of Adaptive Channeling of Low-Energy Particles in Above-Target Graphene Film to Optimize Accelerator Nuclear Fusion in Unstructured Targets

A method for optimizing controlled nuclear fusion in an unstructured target using low-energy particles (e.g., hydrogen) is discussed. The main idea of the method is the use of quasi channeling of such particles in a thin single-crystal film of a graphene type located near the surface of an unstructured target made of an optimal isotope for fusion (e.g., natural Li). Such motion at an optimum particle energy of approximately 500 eV leads to the formation of a coherent correlated state of these particles with very large fluctuations of the transverse energy up to 50 to 100 keV in this film and in the adjacent part of the target. The interaction of these particles with target nuclei leads to the stimulation of effective nuclear fusion p(Li7,α)He4.

Kinetic vs magnetic chaos in toroidal plasmas: A systematic quantitative comparison

Magnetic field line chaos occurs under the presence of non-axisymmetric perturbations of an axisymmetric equilibrium and is manifested by the destruction of smooth flux surfaces formed by the field lines. These perturbations also render the particle motion, as described by the guiding center dynamics, non-integrable and, therefore, chaotic. However, the chaoticities of the magnetic field lines and the particle orbits significantly differ in both strength and radial location in a toroidal configuration, except for the case of very low-energy particles whose orbits closely follow the magnetic field lines. The chaoticity of more energetic particles, undergoing large drifts with respect to the magnetic field lines, crucially determines the confinement properties of a toroidal device but cannot be inferred from that of the underlying magnetic field. In this work, we implement the smaller alignment index method for detecting and quantifying chaos, allowing for a systematic comparison between magnetic and kinetic chaos. The efficient quantification of chaos enables the assignment of a value characterizing the chaoticity of each orbit in the space of the three constants of the motion, namely, energy, magnetic moment, and toroidal momentum. The respective diagrams provide a unique overview of the different effects of a specific set of perturbations on the entire range of trapped and passing particles, as well as the radial location of the chaotic regions, offering a valuable tool for the study of particle energy and momentum transport and confinement properties of a toroidal fusion device.

KinKal: A Kinematic Kalman filter Track Fitting Package for the Mu2e Experiment

Many current physics experiments require precision reconstruction of low-energy particles. One example is the Mu2e experiment, which requires reconstructing an isolated 105 MeV electron with better than 500 KeV/c momentum resolution. Mu2e uses a low-mass straw tube tracker, and a CsI crystal calorimeter, to reconstruct tracks. In this paper, we present the design and performance of a track reconstruction algorithm optimized for Mu2e’s unusual requirements. The algorithm is based on the KinKal [1] kinematic Kalman filter track fit package. KinKal supports multiple track parameterizations, including one optimized for looping tracks, such as Mu2e signal tracks, and others optimized for straight or slightly-curved tracks, such as the high-momentum (>1 GeV/c) cosmic ray muons used to calibrate and align the Mu2e detectors. All KinKal track parameterizations include the track origin time, to correctly model correlations arising from measurements that couple time and space, such as the straw drift time or the calorimeter cluster time. KinKal employs magnetic field inhomogeneity and material effect correction algorithms with 10−4 fractional precision. The Mu2e fit uses Artificial Neural Net functions to discriminate background hits from signal hits, and to resolve the straw tube hit left-right ambiguity, while iterating the extended Kalman filter. The efficiency, accuracy, and precision of the Mu2e track reconstruction, as tested on detailed simulations of Mu2e data, are presented.

Exploring the potential use of silver-exchanged zeolites for adsorption of radon traces in low background experiments

Abstract Radon is an important source of radioactive background in experiments searching for rare decays and in the field of low-energy particle physics. Here, we report the first temperature-dependent study of radon adsorption on silver-exchanged zeolites from several commercial producers. Among the three tested zeolites, Ag-ETS-10 showed the best result. Hence, it was chosen for the further study of internal radioactivity and radon emanation, which are important characteristics of materials used in low-activity experiments. The important role of silver in radon adsorption is demonstrated by comparison of the silver-exchanged zeolites with their unexchanged counterparts. Furthermore, the temperature-dependent measurements showed that the enhancement of the radon adsorption upon the introduction of silver in zeolite occurs due to the increase of the heat of adsorption. This opens a new perspective for the search for highly efficient radon adsorbents.

Re-energization of AGN head–tail radio galaxies in the galaxy cluster ZwCl 0634.1+47474

ABSTRACT Low-frequency radio observations show an increasing number of radio galaxies located in galaxy clusters that display peculiar morphologies and spectral profiles. This is the result of the dynamical interaction of the galaxy with the surrounding medium. Studying this phenomenon is key to understanding the evolution of low-energy relativistic particles in the intracluster medium. We present a multifrequency study of the three head–tail (HT) radio galaxies and the radio halo in the galaxy cluster ZwCl 0634.1+4747. We make use of observations at four frequencies performed with LOFAR LBA (53 MHz), HBA (144 MHz), GMRT (323 MHz), and VLA (1518 MHz) data. The use of extremely low radio frequency observations, such as LOFAR at 53 and 144 MHz, allowed us to detect the extension of the tails up to a distance of ∼1 Mpc. We extracted spectral profiles along the tails in order to identify possible departures from a pure ageing model, such as the Jaffe–Perola (JP) model, which only involves synchrotron and inverse-Compton losses. We found clear evidence of departures from this simple ageing model, such as surface brightness enhancement and spectral flattening along all of the tails. This can be interpreted as the consequence of particle re-acceleration along the tails. Possible explanations for this behaviour include the interaction between a shock and the radio tails or a turbulence-driven re-acceleration mechanism. We show that the latter scenario is able to reproduce the characteristic features that we observed in our profiles.

First operation of an ALICE OROC operated in high pressure Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} and Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document}

New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} mixtures with a CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document} content between 2.8 and 5.0%, and so far up to 4 bar absolute with Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} (90-10). The charge gain of the OROC was measured with signals induced by an 55Fe\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{55}\ ext {Fe}$$\\end{document} source. The largest gain achieved at 4.2 bar was (29±1)·103\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(29\\pm 1)\\cdot 10^{3}$$\\end{document} in Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} with 4.0% CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document} with an anode voltage of 2975V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2975}\\,\\hbox {V}$$\\end{document}. In Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} with 10% CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CO}_{2}$$\\end{document} at 4 barA, a gain of (4.2±0.1)·103\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(4.2\\pm 0.1)\\cdot 10^{3}$$\\end{document} was observed with anode voltage 2975V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2975}\\,\\hbox {V}$$\\end{document}. We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in Ar-CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Ar-CO}}_2$$\\end{document} with 10% CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CO}_{2}$$\\end{document} (10,000 in Ar-CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Ar-CH}_4$$\\end{document} with ∼4%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim \\!{4}{\\%}$$\\end{document}CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CH}_{4}$$\\end{document}) may be achieved with anode voltage of 4.6kV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${4.6}\\,\\hbox {kV}$$\\end{document} (∼3.6kV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim \\!{3.6}\\,\\hbox {kV}$$\\end{document}).

Influence of low-energy supersymmetric vector-like quirk particles on W mass increment and muon g–2 anomaly* *Supported by the National Natural Science Foundation of China (12075213)

In the low energy realization of the quirk assisted Standard Model, the couplings between the exotic particles "quirks" and gauge bosons may contribute to the W mass and muon anomaly reported by FermiLab. We calculate the contributions from supersymmetric quirk particles as an example. By imposing the theoretical constraints, we determined that the CDF II W-boson mass increment strictly constrains the mixing and coupling parameters and the quirk mass , while the muon anomaly cannot be solely attributed to the involvement of exotic particles, considering their significantly large masses.

Non-resonant ultra-fast multipactor regime in dielectric-assist accelerating structures

The objective of this work is the evaluation of the risk of suffering a multipactor discharge in an S-band dielectric-assist accelerating (DAA) structure for a compact low-energy linear particle accelerator dedicated to hadrontherapy treatments. A DAA structure consists of ultra-low loss dielectric cylinders and disks with irises which are periodically arranged in a metallic enclosure, with the advantage of having an extremely high quality factor and very high shunt impedance at room temperature, and it is therefore proposed as a potential alternative to conventional disk-loaded copper structures. However, it has been observed that these structures suffer from multipactor discharges. In fact, multipactor is one of the main problems of these devices, as it limits the maximum accelerating gradient. Because of this, the analysis of multipactor risk in the early design steps of DAA cavities is crucial to ensure the correct performance of the device after fabrication. In this paper, we present a comprehensive and detailed study of multipactor in our DAA design through numerical simulations performed with an in-house developed code based on the Monte–Carlo method. The phenomenology of the multipactor (resonant electron trajectories, electron flight time between impacts, etc.) is described in detail for different values of the accelerating gradient. It has been found that in these structures an ultra-fast non-resonant multipactor appears, which is different from the types of multipactor theoretically studied in the scientific literature. In addition, the effect of several low electron emission coatings on the multipactor threshold is investigated. Furthermore, a novel design based on the modification of the DAA cell geometry for multipactor mitigation is introduced, which shows a significant increase in the accelerating gradient handling capabilities of our prototype.

Effect of large-angle incidence on particle identification performance for light-charged ([formula omitted]) particles by pulse shape analysis with a pad-type nTD silicon detector

In recent years, particle discrimination methods based on digital waveform analysis techniques for neutron-transmutation-doped silicon (nTD-Si) detectors have become widely used for the identification of low-energy charged particles. Although the particle discrimination capability of this method has been well demonstrated for small incident angles, the particle discrimination performance may be affected by changes in the detector response when the detector is moved closer to the charged particle source and the incident position distribution and incident angle distribution to the detector become wide. In this study, we performed a beam test for particle discrimination in light-charged (Z≤2) particles using the digital waveform analysis method with a pad-type nTD-Si detector and investigated the dependence of the performance of the particle discrimination on the incident position and incident angle. As the incident angle increased, a decrease in the maximum current was observed, which was sufficient to affect the performance of the particle discrimination. This decrease can be expressed as a function of the penetration depth of the charged particles into the detector, which varies for each nuclide.

Pre-Earthquake Ionospheric Anomalies of the Wenchuan Earthquake Studied with DEMETER Satellite

The pre-earthquake ionospheric anomalies in Wenchuan, China (21°-41°N, 93°-113°E) are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER (Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions) satellite detectors ICE (Internet Communications Engine), IAP (In Application Programming), and ISL (Interior Switching Link). In this paper, we take the 12 May 2008 Wenchuan earthquake as an example, use the spatial gridding method to construct the background field over the epicenter, analyze the background characteristics of very low frequency (VLF) electric field components, low-energy particle parameters, and plasma parameters, and define the perturbation intensity index of each parameter before the earthquake to extract each parameter anomaly in both space and time dimensions. The results show that the background values of some ionospheric parameters in the Wenchuan area are related to spatial distribution. Moreover, anomalous enhancement of low-frequency electric field power spectral density, H+ concentration, He+ concentration and ion concentration with different intensities and anomalous weakening of ion temperature were extracted in the fifteen days before the Wenchuan earthquake. After filtering the data to exclude external interference, such as solar activity, this paper concludes that there is some connection between these anomalies and the Wenchuan earthquake.

Noise assessment of CMOS active pixel sensors for the CYGNO Experiment

Active Pixel sensors play a crucial role in enabling successful low-light scientific experiments due to their inherent advantages and capabilities. Such devices not only offer high spatial resolution but also feature individual pixels with integrated amplifiers, allowing for direct signal amplification at the pixel level. This results in reduced readout noise and improved signal-to-noise ratio (SNR), which are particularly vital when dealing with limited photon counts in low-light environments. This holds particularly true for scientific CMOS (sCMOS) sensors, acknowledged as an advanced evolution of Active Pixel sensors. However, despite their advantages, such sensors can still exhibit limitations such as higher cost and presence of noise artifacts that should be closely investigated. In particular, CYGNO project fits in a global effort aimed at direct detection of Dark Matter particles. CYGNO collaboration intends to build a detector based on a Time Projection Chamber making use of Gas Electron Multipliers for the amplification of ionization electrons. The GEM multiplication process produces photons that can be readout by a high-resolution sCMOS sensor. Such detection system is being designed to have enough sensitivity to detect low-energy particles and to measure released energy with enough granularity so to reconstruct direction and energy profile along their trajectories. The image sensor has an important role in the detector performance, having a direct impact on the SNR of the experiment. This work proposes a study on the performance of three different sCMOS sensors with respect to their sensitivity to low-energy particles and their intrinsic noise, which are of the utmost importance for various scientific experiments.

Low-Velocity-Favored Transition Radiation.

When a charged particle penetrates through an optical interface, photon emissions emerge-a phenomenon known as transition radiation. Being paramount to fundamental physics, transition radiation has enabled many applications from high-energy particle identification to novel light sources. A rule of thumb in transition radiation is that the radiation intensity generally decreases with the decrease of particle velocity v; as a result, low-energy particles are not favored in practice. Here, we find that there exist situations where transition radiation from particles with extremely low velocities (e.g., v/c<10^{-3}) exhibits comparable intensity as that from high-energy particles (e.g., v/c=0.999), where c is the light speed in free space. The comparable radiation intensity implies an extremely high photon extraction efficiency from low-energy particles, up to 8 orders of magnitude larger than that from high-energy particles. This exotic phenomenon of low-velocity-favored transition radiation originates from the interference of the excited Ferrell-Berreman modes in an ultrathin epsilon-near-zero slab. Our findings may provide a promising route toward the design of integrated light sources based on low-energy electrons and specialized detectors for beyond-standard-model particles.

Cosmic ray transport in large-amplitude turbulence with small-scale field reversals

ABSTRACT The nature of cosmic ray (CR) transport in the Milky Way remains elusive. The predictions of current microphysical CR transport models in magnetohydrodynamic (MHD) turbulence are drastically different from what is observed. These models usually focus on MHD turbulence with a strong guide field and ignore the impact of turbulent intermittency on particle propagation. This motivates our studying the alternative regime of large-amplitude turbulence with δB/B0 ≫ 1, in which intermittent small-scale magnetic field reversals are ubiquitous. We study particle transport in such turbulence by integrating trajectories in stationary snapshots. To quantify spatial diffusion, we use a set-up with continuous particle injection and escape, which we term the turbulent leaky box. We find that particle transport is very different from the strong guide-field case. Low-energy particles are better confined than high-energy particles, despite less efficient pitch-angle isotropization at small energies. In the limit of weak guide field, energy-dependent confinement is driven by the energy-dependent (in)ability to follow reversing magnetic field lines exactly and by the scattering in regions of ‘resonant curvature’, where the field line bends on a scale that is of the order of the local particle gyro-radius. We derive a heuristic model of particle transport in magnetic folds that approximately reproduces the energy dependence of transport found numerically. We speculate that CR propagation in the Galaxy is regulated by the intermittent field reversals highlighted here and discuss the implications of our findings for CR transport in the Milky Way.

Turbulent Origins of Particle Intensity Dropout in Gradual Solar Energetic Particle Events During Solar Cycle 23

Dropout is a low-energy particle phenomenon in which the particle intensity drops sharply and then rises rapidly during an impulsive or gradual solar energetic particle (SEP) event. We investigated dropouts in gradual SEP events during solar cycle 23, in which we identified 77 dropout periods with an average duration of approximately 1 hr. During most of the dropout periods, we observe large angles between the mean magnetic field and the solar wind velocity, implying that the slab turbulent component dominates. We therefore explore the origin of particle intensity dropout in slab turbulent environments. At a wave frequency of 1 Hz in the spacecraft frame, we observed a significant positive correlation between the turbulent power spectral density (PSD) and its spectral index, both in the ion dissipation range. As the input PSD decreases, the correlation can amplify the reduction factor for pitch-angle scatterings, quickly suppressing particle scattering through the 90° pitch angle. Hence, particle dropout may occur due to lack of spatial diffusion of particles.

Improving the resolution and light yield in CsI(Tl) scintillators

In the search for Dark Matter, very low-energy sensitive detectors are needed that would be able to distinguish minute differences in closely residing energy peaks. To increase the ability of CsI(Tl) scintillator detectors to do so, a different wrapping material will be used on the innermost layer of the detector. This wrapping material is a 3MTM Enhanced Specular Reflector (ESR) material which is hypothesized to produce a higher light yield with better resolution than the PTFE wrapping of plumber’s tape due to its high reflectivity. Two different types of measurements were carried out to test this hypothesis. Each test was run on a different half of a CsI(Tl) rectangular crystal of volume 48 in3. First, a source of 60Co was used to test the difference between the wrappings. The test was run an hour for the PTFE and the ESR wrapping. We observe a 35% increase in the ADC count for each 60Co energy peak and 15% decrease in the value of the standard deviation around those peaks. Secondly, a source of 241Am was used to test the low-energy capabilities of the ESR material. Here also we see a significant increase in the ADC count for the two energy peaks of the 241Am source. Due to the high photon reflectivity capability of the ESR film, our detector is more capable of collecting photons created by low-energy interactions. As we know Dark Matter produces very low-energy recoils, while interacting with the detector target material, so the ability to contain a maximum number of photons within the detector volume will help us move one step closer to detecting the rare interaction. Because of this significant increase in light yield and general decrease in standard deviation, it is clear that the ESR material has a greater ability to gather higher resolution data than its predecessor. This could lead to a greater understanding of low-energy particles, which in turn could help us understand what Dark Matter really is.

The energetic storm particle events of 3 November 2021

Observations of energetic particles at interplanetary shocks are important to study acceleration mechanisms and their connection with magnetohydrodynamic turbulence. Energetic storm particle (ESP) events are increases in proton fluxes that occur locally at the passage time of interplanetary shocks. These events are more dangerous when they are superimposed on the solar energetic particles (SEPs) produced by the eruption of flares and/or CME-driven shocks propagating from the corona to the interplanetary space. We considered ESP events occurring in association with SEPs on 3 November 2021. We used proton fluxes provided by Solar Orbiter (located at 0.85 AU) in the energy range of 30 keV–82 MeV, by Wind at energies from 70 keV to 72 MeV, and ACE in the range from 40 keV to 5 MeV (both located at the Lagrangian point L1, close to 1 AU along the Sun-Earth direction). In order to broaden the range of analyzed energies (40 keV - 72 MeV), we combine these data with the proton fluxes from the SOHO spacecraft, also located at L1. We analyzed the ESP event and fitted the proton energy spectra at both locations with several distributions to shed light on the mechanisms leading to the acceleration of energetic particles. We also investigated the turbulent magnetic field fluctuations around the shock. The obtained ESP spectra, best reproduced by the so-called double power law function, the spectral differences at the two locations, and the shock features (quasi-parallel geometry, enhanced downstream turbulence) suggest that diffusive shock acceleration is responsible for acceleration of low energy particles, whereas stochastic acceleration contributes to the (re) acceleration of high energies ones.

Characterizing Low-Energy Charged Particles in the Magnetosphere with the LEM CubeSat Spectrometer Project: Detector Concept and Hardware Characterisation

An accurate flux measurement of low-energy charged particles trapped in the magnetosphere is necessary for space weather characterization and to study the coupling between the lithosphere and magnetosphere, which allows for the investigation of the correlations between seismic events and particle precipitation from Van Allen belts. In this work, the project of a CubeSat space spectrometer, the low-energy module (LEM), is shown. The detector will be able to perform an event-based measurement of the energy, arrival direction, and composition of low-energy charged particles down to 0.1 MeV. Moreover, thanks to a CdZnTe mini-calorimeter, the LEM spectrometer also allows for photon detection in the sub-MeV range, joining the quest for the investigation of the nature of gamma-ray bursts (GRBs) and terrestrial gamma-ray flashes (TGFs). The particle identification of the LEM relies on the ΔE−E technique performed by thin silicon detectors. This multipurpose spectrometer will fit within a 10 × 10 × 10 cm3 CubeSat frame, and it will be constructed as a joint project between the University of Trento, FBK, and INFN-TIFPA. To fulfil the size and mass requirements, an innovative approach, based on active particle collimation, was designed for the LEM; this avoids the heavy/bulky passive collimators of previous space detectors. In this paper, we will present the LEM geometry, its detection concept, the results from the developed GEANT4 simulation, and some characterisations of a candidate silicon detector for the instrument payload.

An improved model for predicting the erosion within the DEM framework

For investigating the erosion caused by particle impact, an erosion model based on the particle impact energy has been proposed in our previous study, which can be called IEEM (Impact Energy Erosion Model). By incorporating IEEM with DEM (Discrete Element Method), the erosion caused by particle impact can be numerically predicted. However, IEEM assumes that all particle impacts lead to erosion, which contradicts the reality where gentle particle impacts with low collision energy do not cause erosion. Therefore, an improved erosion model called FIEEM (Filtering Impact Energy Erosion Model) is devised by introducing the concept of filtration into IEEM. In FIEEM, the low-energy particle collisions are filtered by comparing the contact stress with the flow stress of the target material so that these collisions cannot cause erosion, and the Hertz contact theory is employed to determine the accurate contact stress. Subsequently, the DEM simulations of the charge behaviors and liner wear in an industrial-scale SAG (Semi-Automatic Grinding) mill are conducted and then compared with the experimental data for validating the accuracy and effectiveness of FIEEM. Additionally, the discussion regarding the difference of the predicted erosion between IEEM and FIEEM is also presented from the point of effective collision energy.

Hierarchical learning particle swarm optimization using fuzzy logic

Particle swarm optimization (PSO) has been used extensively in numerical and engineering optimization problems in the last decades. However, due to drawbacks such as a single learning sample, PSO has the problems of loss of population diversity and easily falls into local optimum. To enhance optimization capability, a PSO based on fuzzy logic and hierarchical learning mechanism (FHPSO) is proposed. In FHPSO, the parameters are dynamically adjusted through fuzzy logic. The purpose of the fuzzy system is to generate appropriate parameters based on the performance metrics at each iteration, which better balances exploration and exploitation capability. Then particles are classified into different layers in terms of their fitness, and the particles in different layers perform different learning mechanisms. Each layer divides the particles into high-energy particles and low-energy particles. The high-energy particles in each layer are qualified to learn from the particles in the upper layer and the low-energy particles learn from the high-energy particles in their layer. This learning mechanism avoids all individuals to learn the global optimal individual at each iteration which will effectively reduce the speed and possibility of premature convergence and maintain population diversity. The FHPSO was compared with 8 well-known algorithms and 6 state-of-the-art PSO variants in the CEC 2022 and CEC 2021 test suites, respectively. The experimental results show significant performance of FHPSO. Simulation results for 5 complex engineering optimization problems and 3D path planning problem also show that the FHPSO can provides more competitive optimization results.