Charged Particles Research Articles

Measurements regarding a combined therapy concept for ophthalmic tumors consisting of brachytherapy and x-rays

Objective. We present a novel concept to treat ophthalmic tumors which combines brachytherapy and low-energy x-ray therapy. Brachytherapy with 106Ru applicators is inadequate for intraocular tumors with a height of 7 mm or more. This results from a steep dose gradient, and it is unfeasible to deliver the required dose at the tumor apex without exceeding the maximum tolerable sclera dose of usually 1000 Gy to 1500 Gy. Other modalities, such as irradiation with charged particles, may be individually contraindicated. A dose boost at the apex provided by a superficial x-ray therapy unit, performed simultaneously with the brachytherapy, results in a more homogeneous dose profile than brachytherapy alone. This avoids damage to organs at risk. The applicator may also serve as a beam stop for x-rays passing through the target volume, which reduces healthy tissue dosage. This study aims to investigate the suitability of the applicator to serve as a beam stop for the x-rays. Approach. A phantom with three detector types comprising a soft x-ray ionization chamber, radiochromic films, and a self-made scintillation detector was constructed to perform dosimetry. Measurements were performed using a conventional x-ray unit for superficial therapy to investigate the uncertainties of the phantom and the ability of the applicator to absorb x-rays. The manufacturer provided a dummy plaque to obtain x-ray dose profiles without noise from 106Ru decays. Results. The phantom is generally feasible to obtain dose profiles with three different detector types. The interaction of x-rays with the silver of the applicator leads to an increased dose rate in front of the applicator. The dose rate of the x-rays is reduced by up to 90% behind a 106Ru applicator. Therefore, a 106Ru applicator can be used as a beam stop in combined x-ray and brachytherapy treatment.

Measurement of Si pixel sensor alignment for the ALICE ITS detector

Abstract A Large Ion Collider Experiment (ALICE) experiment is one of the four experiments at the Large Hadron Collider (LHC) designed to investigate the status of matter under very high energy densities produced during heavy-ion collisions. The ALICE inner tracking system (ITS) consists of seven concentric cylindrical layers of monolithic silicon pixel sensors known as ALICE pixel detector (ALPIDE). The sensors are used to reconstruct the paths of charged particles generated in the collisions. The sensor alignment of the detector must be adjusted to a high precision standard. The adjustment objective is to obtain a detector that can undertake high-resolution measurements. This paper introduces a method for measuring the reference markers utilized in sensor alignment determination. Markers engraved at the chip corners have been detected using the Hough transform, Canny edge detection, and template matching techniques. The distances between two markers are measured to determine the accuracy of the pixel sensor alignment before and after assembly. The proposed methods exhibit an accuracy exceeding 99% and demonstrate high speed analysis. The average processing times for detecting the circle and cross markers are 105.9 ms/image and 113.8 ms/image, respectively. The sensor alignment of the detector must be adjusted to a high precision standard. However, recent studies have shown deviations of up to 5 μ m above the desired value in the measured sensor position. Such deviations do not represent a major issue, nevertheless it is important to measure them in order to speed-up and make more accurate the recursive track-based alignment procedure used to reconstruct the position of each pixel sensor in the tracking detector. The proposed method offers a promising solution to deliver precise and rapid measurements for a large number of examined objects.

Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror

Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV-induced hydrogen plasma. The Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impacting on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium mirror coating creates a positively charged wall and then prevents the ions from impacting on the mirror and therefore changes the flux and energy distribution of ions reaching the mirror. Furthermore, gas pressure has a notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and at the same time the energy corresponding to the peak flux decreases slightly. However, the EUV source intensity barely changes the sheath potential, and its influence on the ion impact is mainly limited to the approximate linear increase in ion flux.

Assessment of fluence- and dose-averaged linear energy transfer with passive luminescence detectors in clinical proton beams

Objective. This work investigates the use of passive luminescence detectors to determine different types of averaged linear energy transfer ( LET― ) for the energies relevant to proton therapy. The experimental results are compared to reference values obtained from Monte Carlo simulations. Approach. Optically stimulated luminescence detectors (OSLDs), fluorescent nuclear track detectors (FNTDs), and two different groups of thermoluminescence detectors (TLDs) were irradiated at four different radiation qualities. For each irradiation, the fluence- ( LET―f ) and dose-averaged LET ( LET―d ) were determined. For both quantities, two sub-types of averages were calculated, either considering the contributions from primary and secondary protons or from all protons and heavier, charged particles. Both simulated and experimental data were used in combination with a phenomenological model to estimate the relative biological effectiveness (RBE). Main results. All types of LET― could be assessed with the luminescence detectors. The experimental determination of LET―f is in agreement with reference data obtained from simulations across all measurement techniques and types of averaging. On the other hand, LET―d can present challenges as a radiation quality metric to describe the detector response in mixed particle fields. However, excluding secondaries heavier than protons from the LET―d calculation, as their contribution to the luminescence is suppressed by ionization quenching, leads to equal accuracy between LET―f and LET―d . Assessment of RBE through the experimentally determined LET―d values agrees with independently acquired reference values, indicating that the investigated detectors can determine LET― with sufficient accuracy for proton therapy. Significance. OSLDs, TLDs, and FNTDs can be used to determine LET― and RBE in proton therapy. With the capability to determine dose through ionization quenching corrections derived from LET― , OSLDs and TLDs can simultaneously ascertain dose, LET― , and RBE. This makes passive detectors appealing for measurements in phantoms to facilitate validation of clinical treatment plans or experiments related to proton therapy.

Evaluation of cross sections for fast ion reactions with beryllium in helium and hydrogen fusion plasmas

To computationally support hydrogen and helium plasma discharges in the early stages of tokamak operation and to support the commissioning of the neutron detectors during these operational phases, creation of a realistic neutron and gamma ray particle source for Monte Carlo simulations will be needed. One of the most important parts of creating the particle source is calculating the reaction rates of the particle-emitting reactions to determine the emission profile in the plasma and the energy spectra of the emitted particles. In this paper the analysis and evaluation of cross sections for important neutron-emitting reactions, namely, 9Be(p,nγ)9B, 9Be(3He,nγ)11C, and charged-particle emission reactions 9Be(p,d)2α and 9Be(p,α)6Li that cause neutron emission in the next step of interactions are presented. The reaction cross sections were evaluated based on experimental measurements and empirical models describing the interaction of two charged particles. Evaluation of the associated uncertainties was also performed. The main goal of the work is to propose the newly evaluated cross sections for inclusion in the FENDL nuclear data library, thus making the cross section available to other researchers studying the above listed reactions.

Analyzing the correlation between thermal and kinematic parameters in various multiplicity classes within 7 and 13 TeV pp collisions

We investigate the transverse momentum spectra of identified particles at 7 and 13 TeV in pp collisions in the framework of the blast wave model with Tsallis statistics (TBW). Based on experimental data by ALICE Collaboration, we observe that the model describes the p T spectra well with the common Tsallis temperature (T) and flow velocity (β T ) but separate non-extensive parameters (q) for baryons and mesons. The parameter dependence on multiplicity as well as on collision energy is investigated, and a strong dependence on the former while a weak dependence on the latter is reported. The extracted parameters in this work consist of the initial temperature (T i ), the average transverse momentum (〈p T 〉), the Tsallis temperature (T), the flow velocity (β T ), and the non-extensive parameter (q). These parameters are found to increase a little with increasing energy, however, they (except the parameter q) decrease significantly with decreasing multiplicity. We observe that β T drops to zero at high multiplicity , while, T and q do not change their behavior. Furthermore, our analysis explore the correlations among different parameters, including associations with the charged particle multiplicity per unit pseudorapidity ( 〈dNch/dη〉 ). The correlations between T and β T , T and 〈dNch/dη〉 , β T and 〈dNch/dη〉 , T i and 〈p T 〉 and T i and 〈dNch/dη〉 demonstrates a positive relationship, while, the correlation between T and q − 1, and q − 1 and 〈dNch/dη〉 is negative. Finally, we implement an extra flow correction on the T parameter. Our findings reveal that the Doppler-corrected temperature parameter aligns closely with the T in scenarios with lower multiplicities. However, as the multiplicity increases, a noticeable divergence emerges between these parameters, indicating a widening separation between them.

Experimental study of aerosol behavior in ambient electric and magnetic fields at low indoor relative humidity

The tendency of aerosols to carry viral particles featured significantly in public discourse during the SARS Covid-19 pandemic. In this research, the potential significance of the aerosol electric charge, especially as it relates to indoor relative humidity (RH) is considered. While electrostatic interactions may occur at any level of humidity, the level of humidity has a strong influence on these interactions. Above 55 % RH, there is sufficient moisture in the air to facilitate neutralization of the electric charges of particles and surfaces, whereas, at lower humidity levels, less moisture and higher surface resistivities enable increasingly stronger electrostatic interactions. Experiments were designed and conducted to study the behavior of electrically charged aerosols in fields emanating from capacitive touchscreens and permanent magnets. These preliminary experimental results suggest that operating indoor environments closer to the 55–60 % RH range could reduce interactions between these charged aerosols and capacitive touchscreens. This relative humidity range is within the acceptable ranges of humidity recommended by ASHRAE standard 55 which defines thermal environmental conditions for human occupancy.

Dust Particle Surface Potential in an Argon-Helium Plasmas using (r,q)-Distribution Function

Abstract In this paper, the dust particle surface potential for argon-helium plasma is evaluated analytically and numerically in the contest of negatively charged dust particles by employing a power-law (r,q)-distribution function. Recent studies have reported the argon-helium plasma and conducted a brief theoretical and experimental survey. To deepen our understanding further, this study aims to analyze the argon-helium plasma comprehensively using the same pattern but with the (r,q)-distribution function. For this subject, the current balance equations are derived for electron, helium, and argon ions, when these charge species attain the quasineutrality condition. We numerically examined the currents of plasma species for a broad range of effective distribution function parameters r and q. It is revealed that the surface potential of dust particles is significantly affected by the parameters r and q, helium ion-to-electron temperature ratio, argon ion-to-electron temperature ratio, and helium ion to argon ion number density ratio. By incorporating the multi-ion (argon-helium) species, the significance of low-temperature non-Maxwellian dusty (complex) plasma is briefly examined.

Rotation Matrix of a Charged Symmetrical Body: One-Parameter Family of Solutions in Elementary Functions

Euler–Poisson equations of a charged symmetrical body in external constant and homogeneous electric and magnetic fields are deduced starting from the variational problem, where the body is considered as a system of charged point particles subject to holonomic constraints. The final equations are written for the center-of-mass coordinate, rotation matrix and angular velocity. A general solution to the equations of motion is obtained for the case of a charged ball. For the case of a symmetrical charged body (solenoid), the task of obtaining the general solution is reduced to the problem of a one-dimensional cubic pseudo-oscillator. In addition, we present a one-parametric family of solutions to the problem in elementary functions.

Optimizing shear-thickening fluid microencapsulation with high-temperature pickering emulsion for enhanced impact-resistant materials

Combining shear-thickening fluid (STF) with matrix material enables the creation of high-performance materials with enhanced impact resistance. However, effectively preventing STF leakage and avoiding potential reactions between the fluid and the matrix material remain notable challenges. Encapsulating STF through emulsion templating offers a viable solution to these issues. Traditional emulsion templating methods require adding extra solvents to STF to counteract the hindrance of shear-thickening on emulsification, accompanied with increased costs and environmental pollution, and difficulties in maintaining the integrity of core components. In this study, we developed STF microcapsules using a novel high-temperature Pickering double emulsion technique. Our investigation into the rheological properties of molecular sieve/diols suspensions demonstrates that the shear thickening effect could be controlled by particle concentration, surface charge of particles and solvent viscosity. Octadecyltrimethoxysilane-modified fumed silica and fumed silica were utilized as stabilizers for STF-in-paraffin primary emulsions and STF-in-paraffin-in-propylene glycol secondary emulsions, respectively. As temperature increased, droplet sizes of the primary emulsion were significantly reduced. The Pickering emulsion approach effectively preserves the STF composition by forming robust barriers at the emulsion interface with silica particles. Typical STF microcapsules were incorporated into a silicone rubber matrix, the composites exhibited a significant decrease in resilience and an enhanced impact resistance with a 20.9% reduction in maximum impact force. This study is the first to suggest the application of the high-temperature Pickering double emulsion technique for the microencapsulation of STF, offering a practical and scalable method without diluting the STF, thereby ensuring the controllability of the core components.

Role of Subauroral Polarization Streams in Deep Injections of Energetic Electrons Into the Inner Magnetosphere

AbstractThe electric fields of subauroral polarization streams (SAPS) have been suggested to affect energetic charged particles' dynamics in the inner magnetosphere, though their role on radiation belt electrons has never been properly quantified. A moderate geomagnetic storm on 2015‐09‐07 caused the deep injection of 10–100s of keV electrons in Earth's inner magnetosphere to low L* (L* < 4). Using a 2‐D test particle tracer, we present the effects of electric fields given by the Volland‐Stern model, a SAPS (Goldstein et al., 2005, https://doi.org/10.1029/2005ja011135) model, and a modified SAPS model on the energetic electron deep injections. The modified SAPS model reflects the SAPS electric field observations by the Van Allen Probes and is supported by Defense Meteorological Satellite Program observations. Simulations suggest that the SAPS electric field pushes 10–20 MeV/G electrons Earthward to L* ∼ 2.7 in 2.5 hr, much deeper compared to the Volland‐Stern electric field.

On the Role of the Tail Term in Electromagnetic Radiation Reaction

In a recent study devoted to the influence of electromagnetic radiation reaction on the motion of radiating charged particles in magnetized black hole spacetimes the authors claim that the tail term cannot be neglected in the complete DeWitt–Brehme equation, putting into doubt the previous papers where such an approximation was used. Here, we demonstrate by using simple dimensional arguments that such a statement is misleading in many astrophysically relevant situations. In the case of relativistic electrons moving around a stellar-mass black hole, the tail term is ignorable if a magnetic field of at least a few Gauss is present.On the other hand, in different situations, the tail term can be relevant, as demonstrated in the case of orbital widening, where it can even amplify the effect.

Anti-Inflammatory Activity of No-Ozone Cold Plasma in Porphyromonas gingivalis Lipopolysaccharide-Induced Periodontitis Rats.

Periodontitis is an inflammatory disease caused by Porphyromonas gingivalis (P. gingivalis) in the oral cavity. This periodontal disease causes damage to the periodontal ligament and alveolar bone and can cause tooth loss, but there is no definite treatment yet. In this study, we investigated the possibility of using no-ozone cold plasma to safely treat periodontitis in the oral cavity. First, human gingival fibroblasts (HGFs) were treated with P. gingivalis-derived lipopolysaccharide (PG-LPS) to induce an inflammatory response, and then the anti-inflammatory effect of NCP was examined, and a study was conducted to identify the mechanism of action. Additionally, the anti-inflammatory effect of NCP was verified in rats that developed an inflammatory response similar to periodontitis. When NCP was applied to PG-LPS-treated HGFs, the activities of inflammatory proteins and cytokines were effectively inhibited. It was confirmed that the process of denaturing the medium by charged particles of NCP is essential for the anti-inflammatory effect of NCP. Also, it was confirmed that repeated treatment of periodontitis rats with NCP effectively reduced the inflammatory cells and osteoclast activity. As a result, this study suggests that NCP can be directly helpful in the treatment of periodontitis in the future.

Divergence of the energy-losing rate of charged particles in plasmas

In modeling the charged alpha particle transport in hot-spot plasmas of inertial confinement fusion, the energy-losing rate is a major concern in the Monte Carlo simulations of alpha particle transport of a radiative-hydrodynamic code. However, the traditionally used energy stopping-power only describes the averaged energy-losing rate of the incident charged particles, whereas the variance of the energy exchange with the background particles is generally ignored. In this paper, the variance of charged particle collisions is studied by both analytical derivation and Monte Carlo simulations. An expression of the divergence of the charged particle energy-losing rate is given for the first time, which can be directly used for practical estimations. It indicates that when the areal density of the target particles along the incident particle path length is low, the divergence of the lost energy would be much larger than the average value, and the traditionally used energy stopping-power would be no longer sufficient to describe the charged particle Coulomb collisions. It helps to obtain a more comprehensive understanding about the charged particle transport in plasmas.

Scaling Energy Transfer in Ball Mills: A Scale-Agnostic Approach through a Universal Scaling Constant

Ball mills are widely used for size reduction in mineral processing, but effective scaling from laboratory to industrial scale remains challenging. This study introduces a novel scaling constant approach to replicate energy transfer to ore during milling across different scales by adjusting rotational speed and grinding medium size distribution. The scaling constant encapsulates parameters like the number of balls per working area, rotational speed, and an average ball’s maximum potential and kinetic energies. Experiments were conducted using a laboratory ball mill with interchangeable drum sizes (300, 400, and 500 mm) and a Design of Experiments methodology. Statistical analysis revealed that the scaling constant was more effective at maintaining consistent specific energy and energy per rotation across scales than size reduction, especially in dry milling. Wet milling results showed no significant differences in all metrics across scales. The dominant charge motion shifted from centrifuging to cascading as the mill diameter increased, highlighting the complex scaling dynamics. While the scaling constant shows promise for maintaining energy utilization, additional factors like charge motion and particle breakage mechanisms should be considered. The findings provide insights for improving ball mill design and optimization in mineral processing.

Development of a non-intercepting weak beam current measurement electronics for Heavy Ion Accelerator Facility in Lanzhou.

Non-destructive measurements of low-intensity charged particle beams are particularly challenging for beam diagnostics. At the Heavy Ion Accelerator Facility in Lanzhou (HIRFL), beams with weak currents below 1 µA are often provided for experiments. The detection of such low beam current is below the threshold of typical standard beam current transformers. Therefore, a low-intensity monitoring system is developed by using a sensitive capacitive pick-up (PU) and low-noise electronics. This device measures beam currents by digitally analyzing the amplitude of the PU signals using a homodyne detection scheme. During lab tests, the amplitude nonlinearity is <0.5% in the operational range of 1 nA-45 µA and the amplitude resolution is 0.94 nA. At present, four measurement systems for low beam currents are installed at HIRFL for the monitoring of standard operating conditions with low beam currents below 1 µA. After an absolute calibration with a Faraday cup, it can be used for accurate beam intensity measurement with a current resolution of about 1 nA.

Dynamic acceleration of energetic protons by an interplanetary collisionless shock

Context. Interplanetary collisionless shocks are known to be capable of accelerating charged particles up to hundreds of MeV. However, the underlying acceleration mechanisms are still under debate. Aims. We present the dynamic behaviors of energetic protons that are accelerated by an interplanetary shock that was observed with unprecedented high-resolution measurements by the Electron-Proton Telescope sensor of the Energetic Particle Detector suite on board the Solar Orbiter spacecraft on 2021 November 3. We constrain the potential acceleration mechanisms and processes. Methods. We first reconstructed the proton pitch-angle distributions (PADs) in the solar wind frame. Then, we examined the temporal flux profile, PAD, and the velocity distribution function of energetic protons close to the shock, and we qualitatively compared the observations with theoretical predictions. Moreover, we applied a velocity dispersion analysis (VDA) to an observed velocity dispersion event and derived the proton path length and release time at the shock. Then, we tested this derivation by comparing it with the shock motion and the magnetic field configuration. Results. We find that ∼1000–4000 keV protons exhibit a rapid-rise, rapid-decay temporal flux profile with a clear velocity dispersion ∼2 min before the shock, similar to impulsive solar energetic particle events. The proton path length based on the VDA of this event is consistent with the length derived from the shock motion and magnetic field configuration. The peak spectrum in this event appears to be steeper than the spectrum at the shock. Furthermore, we find that ∼50–200 keV proton fluxes peak between ∼10 and ∼20 s before the shock, with an inverse velocity dispersion. The velocity dispersion event and the inverse velocity dispersion event are both accompanied by magnetic kinks or switchbacks. In addition, two distinct proton populations appear near the shock. The first population at energies below ∼300 keV is characterized by a power-law spectrum with an index of ∼6–7 and a flux profile that increases before and decreases after the shock. The other population at energies above ∼300 keV shows a long-lasting, anti-sunward-beamed PAD across the shock and a flux profile that remains relatively constant before and increases slightly after the shock. Conclusions. These results suggest that the shock acceleration of energetic protons is highly dynamic due to temporal and/or spatial variations at the shock front. The observation of the velocity dispersion event further suggests that shock acceleration can be impulsive and efficient, which may be due to the interaction between the shock and magnetic kinks or switchbacks. Moreover, these results may support shock-drift acceleration and diffusive shock acceleration as candidate acceleration mechanisms at interplanetary shocks.

Performance of the CERN Proton Synchrotron internal dump: numerical simulation studies and comparison with beam measurements

In the framework of the LHC Injector Upgrade project, a new internal dump for the CERN Proton Synchrotron (PS) ring has been designed, installed, and successfully commissioned. This device is designed to move rapidly into the beam and stop charged particles over several thousand turns to provide protection to PS hardware against beam-induced damage. Due to its design, the internal dump absorbs only a fraction of the secondary particles shower produced by the beam particles that impinge on it. The performance of the dump should ensure efficient use throughout the PS energy range, i.e. from injection at 2 GeV (kinetic energy) to flat top at 26 GeV (total energy). This paper presents comprehensive numerical simulations that combine advanced beam dynamics and beam-matter interaction codes to analyse the behaviour of stopped or scattered particles. Based on the impacts computed by multi-turn beam dynamics simulations, detailed shower simulations with FLUKA were performed to assess the impact of the radiation field on downstream equipment, with a particular emphasis on the dose measured by Beam Loss Monitors. The results of these numerical simulations are compared with the data collected during the routine operation of the PS and its internal dump.

Deep-learning-based decomposition of overlapping-sparse images: application at the vertex of simulated neutrino interactions

Image decomposition plays a crucial role in various computer vision tasks, enabling the analysis and manipulation of visual content at a fundamental level. Overlapping and sparse images pose unique challenges for decomposition algorithms due to the scarcity of meaningful information to extract components. Here, we present a solution based on deep learning to accurately extract individual objects within multi-dimensional overlapping-sparse images, with a direct application to the decomposition of overlaid elementary particles obtained from imaging detectors. Our approach allows us to identify and measure independent particles at the vertex of neutrino interactions, where one expects to observe images with indiscernible overlapping charged particles. By decomposing the image of the detector activity at the vertex through deep learning, we infer the kinematic parameters of the low-momentum particles and enhance the reconstructed energy resolution of the neutrino event. Finally, we combine our approach with a fully-differentiable generative model to improve the image decomposition further and the resolution of the measured parameters. This improvement is crucial to search for asymmetries between matter and antimatter.

Assembly and testing of 2S module prototypes for the CMS Phase-2 outer tracker upgrade

The HL-LHC necessitates a Phase-2 upgrade for the CMS detector, which includes the complete replacement of the existing tracker. The new Outer Tracker incorporates two types of silicon module, 2S and PS, based on an innovative transverse momentum (pT) discrimination idea. By using these modules, the information from the tracker will be sent to the Level-1 (L1) trigger for the first time. They will identify charged particles with pT > 2 GeV, helping to reduce the data sent to the L1 trigger. This paper offers a comprehensive overview of the 2S module prototyping process, which include the precise assembly and testing procedures to ensure their performance and quality before integration into the Outer Tracker. Additionally, to assess the performance of a 2S module in beam, the data from a DESY test beam is reconstructed and analyzed using the Corryvreckan offline reconstruction framework. The results demonstrate agreement to within 1% with those obtained using the EUTelescope framework.