Proton Spectra Research Articles

Ion Acceleration by Foreshock Bubbles: Magnetospheric Multiscale Observations

AbstractForeshock bubbles (FBs) occur when interplanetary magnetic field discontinuities encounter the Earth's foreshock. These transient (∼1 to 5 min) features exhibit depressed densities and magnetic field strengths, enhanced temperatures, and deflected plasma flows trailed by a region of enhanced plasma density and magnetic field strength. Ions can be accelerated inside the FBs through the Fermi acceleration process. Hybrid simulations and test particle calculations predict that the maximum energies of ions accelerated by FBs reach 5.6 times the solar wind ram energy (Esw). We identify 23 FBs from September 2015 to January 2020 Magnetospheric Multiscale spacecraft observations. Most FBs (17 of 23) occurred upstream of the dusk‐side bow shock and above the ecliptic. The FBs occurred for Alfvn Mach numbers ranging from 5 to 15, with 11 FBs having an Alfvn Mach number near 10. To investigate ion energization inside the cores of the FBs we compare the proton spectra observed by the Hot Plasma Composition Analyzer and Energetic Ion Spectrometer before (upstream), during (core), and after (downstream) the FBs. The proton intensities at energies from Esw (the solar wind ram energy, ) up to about 5.6Esw are greater inside than outside 19 of 23 FBs, confirming that FBs can accelerate particles to these energies. The proton flux intensities at energies between Esw and 5.6Esw in the core of the FBs are consistent with results from global hybrid simulations for ion energization from FBs through second‐order Fermi acceleration.

Stable high repetition-rate laser-driven proton beam production for multidisciplinary applications on the advanced laser light source ion beamline.

Laser-driven proton accelerators are relevant candidates for many applications such as material science or medicine. Today, there are multi-hundred-TW table-top laser systems that can generate relativistic peak intensities >1018 W/cm2 and routinely reach proton energies in the MeV range. However, for most desired applications, there is still a need to optimize the quality and stability of the laser-generated proton beam. In this work, we developed a 0.625Hz high repetition-rate setup in which a laser with 2.5% RMS energy stability is irradiating a solid target with an intensity of 1019 to 1020 W/cm2 to explore proton energy and yield variations, both with high shot statistics (up to about 400 laser shots) and using different interaction targets. Investigating the above-mentioned parameters is important for applications that rely on specific parts of the proton spectrum or a high ion flux produced over quick multi-shot irradiation. We demonstrate that the use of a stable "multi-shot mode" allows improving applications, e.g., in the detection of trace elements using laser-driven particle-induced x-ray emission.

Direct measurements of cosmic rays with the calorimetric electron telescope on the international space station

The CALorimetric Electron Telescope, CALET, has been measuring high-energy cosmic rays on the International Space Station since October 13, 2015. The scientific objectives addressed by the mission are to search for possible nearby sources of high-energy electrons and potential signatures of dark matter, and to investigate the details of galactic cosmic-ray acceleration and propagation. The calorimetric instrument, which is 30 radiation lengths or 1.3 proton interaction lengths thick with fine imaging capability, is optimized to measure cosmic-ray electrons by achieving large proton rejection and excellent energy resolution well into the TeV region. In addition, very wide dynamic range of energy measurement and individual charge identification capability enable us to measure proton and nuclei spectra from a few tens GeV to a PeV scale. Nearly 20 million cosmic-ray shower events over 10 GeV per month are triggered and the continuous observation has been kept without any major interruption since the start of operation. Using the data obtained over 6.5 years of operation, we will present a brief summary of the CALET observation including electron spectrum, and proton and nuclei spectra as well as the performance study on orbit with MC simulations.

A measurement of the proton plus helium spectrum of cosmic rays in the TeV region with HAWC

HAWC is an air-shower detector designed to study TeV gamma and cosmic rays. The observatory is composed of a 22000 m^2m2 array of 300 water Cherenkov tanks (4.5 m deep x 7.3 m diameter) with 4 photomultipliers (PMT) each. The instrument registers the number of hit PMTs, the timing information and the total charge at the PMTs during the event. From these data, shower observables such as the arrival direction, the core position at ground, the lateral age and the primary energy are estimated. In this work, we study the distribution of the shower age vs the primary energy of a sample of shower data collected by HAWC from June 2015 to June 2019 and employ a shower-age cut based on predictions of QGSJET-II-04 to separate a subsample of events dominated by H and He primaries. Using these data and a dedicated analysis, we reconstruct the cosmic ray spectrum of H+He from 6 to 158 TeV, which shows the presence of a softening at around 24 TeV with a statistical significance of 4.1\sigmaσ.

Macroscopic and microscopic investigation of maximum effectiveness of proton-boron capture therapy using Monte Carlo simulation

Proton-boron capture therapy (PBCT) has been proposed as a new method to enhance effectiveness of proton therapy. There is, however, no consensus on its potential effectiveness. Most theoretical studies have been done at a macroscopic level. At cellular dimensions, however, the dose ratio with PBCT can be strongly favourable due to proton-boron reactions. The goal of this study was to investigate the theoretical maximum dose enhancement with PBCT, and its radiation physics mechanisms, through both macroscopic and microscopic simulations. The Monte Carlo simulations involved two stages due to model limitations. In the macroscopic calculations, variations in Bragg-peak height and depth caused by a 10 mm thick boron region were examined for different proton energies (62, 80 and 100 MeV) using MCNPX. Percentage depth doses and energy spectra of protons, alpha particles, neutrons and photons were also computed. The second stage used Geant4 for dose calculation in cellular dimensions. Macroscopically, the energy deposition peak shifted towards the surface by about 3.1 mm and the Bragg peak dose increased by up to 53.1%, 53.4%, 53.9% for proton energies 62, 80 and 100 MeV, respectively, compared to the proton-only (no boron) case. Microscopically, the calculated total equivalent doses for these energies showed 5%, 23% and 50% enhancements, respectively. The results suggest increased effectiveness with PBCT due to production of short-range alpha-particles, especially at higher incident proton energies. Also, by adding boron, the mean proton energy is reduced thereby increasing the probability of local dose deposition. The theoretical maximum possible improvement in dose equivalent in the target region at the cellular scale was shown to slightly increase with beam energy, reaching about 54% at the highest studied energy. This combined approach has provided further insight into the potential of PBCT. Further studies, particularly at higher proton energies, are indicated.

Rapid Measurement of Heteronuclear Coupling Constants in Complex NMR Spectra.

The NMR analysis of fluorine-containing molecules, increasingly widespread due to their importance in pharmaceuticals and biochemistry, poses significant challenges. Severe peak overlap in the proton spectrum often hinders the extraction of critical structural information in the form of heteronuclear scalar coupling constants, which are crucial for determining pharmaceutical properties and biological activity. Here, a new method, IPAP-FESTA, is reported that drastically simplifies measurements of the signs and magnitudes of proton-fluorine couplings. Its usefulness is demonstrated for the structural study of the steroidal drug fluticasone propionate extracted from a commercial formulation and for assessing solvent effects on the conformational equilibrium in a physically inseparable fluorohydrin mixture.

GPU-accelerated calculation of proton microdosimetric spectra as a function of target size, proton energy, and bounding volume size

Objective. Shortcomings of dose-averaged linear energy transfer (LETD), the quantity which is most commonly used to quantify proton relative biological effectiveness, have long been recognized. Microdosimetric spectra may overcome the limitations of LETD but are extremely computationally demanding to calculate. A systematic library of lineal energy spectra for monoenergetic protons could enable rapid determination of microdosimetric spectra in a clinical environment. The objective of this work was to calculate and validate such a library of lineal energy spectra. Approach. SuperTrack, a GPU-accelerated CUDA/C++ based application, was developed to superimpose tracks calculated using Geant4 onto targets of interest and to compute microdosimetric spectra. Lineal energy spectra of protons with energies from 0.1 to 100 MeV were determined in spherical targets of diameters from 1 nm to 10 μm and in bounding voxels with side lengths of 5 μm and 3 mm. Main results. Compared to an analogous Geant4-based application, SuperTrack is up to 3500 times more computationally efficient if each track is resampled 1000 times. Dose spectra of lineal energy and dose-mean lineal energy calculated with SuperTrack were consistent with values published in the literature and with comparison to a Geant4 simulation. Using SuperTrack, we developed the largest known library of proton microdosimetric spectra as a function of primary proton energy, target size, and bounding volume size. Significance. SuperTrack greatly increases the computational efficiency of the calculation of microdosimetric spectra. The elevated lineal energy observed in a 3 mm side length bounding volume suggests that lineal energy spectra determined experimentally or computed in small bounding volumes may not be representative of the lineal energy spectra in voxels of a dose calculation grid. The library of lineal energy spectra calculated in this work could be integrated with a treatment planning system for rapid determination of lineal energy spectra in patient geometries.

Improved energy spread in the radiation pressure acceleration of protons with a linearly polarized laser.

Degradation in the energy spread of accelerated protons due to the transverse instability induced transparency is one of the critical issues in the laser-driven radiation pressure acceleration (RPA) scheme. This issue is more severe for linearly polarized lasers due to enhanced heating of electrons. Therefore, in spite of being experimentally challenging, most of the numerical studies are performed with circularly polarized lasers. In this work, through particle-in-cell simulations, we demonstrate a significant improvement in the energy spread of the accelerated protons when a multilayered target is irradiated by a linearly polarized laser. This multilayered target consists of a near-critical-density (NCD) layer, sandwiched between a thick metallic foil and a thin RPA target. The role of the NCD target is to suppress the laser transparency to increase the coupling of laser momentum to the RPA protons. On the other hand, the metallic foil utilizes the kinetic energy of the escaping fast electrons to form an electrostatic sheath to filter the low-energy RPA protons. This results in significant improvement in the accelerated proton spectrum, even with a linearly polarized laser.

Quantification of short echo time MRS signals with improved version of QUantitation based on quantum ESTimation algorithm.

Magnetic resonance spectroscopy offers information about metabolite changes in the organism, which can be used in diagnosis. While short echo time proton spectra exhibit more distinguishable metabolites compared with proton spectra acquired with long echo times, their quantification (and providing estimates of metabolite concentrations) is more challenging. They are hampered by a background signal, which originates mainly from macromolecules (MM) and mobile lipids. An improved version of the quantification algorithm QUantitation based on quantum ESTimation (QUEST), with MM prior knowledge (QUEST-MM), dedicated to proton signals and invoking appropriate prior knowledge on MM, is proposed and tested. From a single acquisition, it enables better metabolite quantification, automatic estimation of the background, and additional automatic quantification of MM components, thus improving its applicability in the clinic. The proposed algorithm may facilitate studies that involve patients with pathological MM in the brain. QUEST-MM and three QUEST-based strategies for quantifying short echo time signals are compared in terms of bias-variance trade-off and Cramér-Rao lower bound estimates. The performances of the methods are evaluated through extensive Monte Carlo studies. In particular, the histograms of the metabolite and MM amplitude distributions demonstrate the performances of the estimators. They showed that QUEST-MM works better than QUEST (Subtract approach) and is a good alternative to QUEST when measured MM signal is unavailable or unsuitable. Quantification with QUEST-MM is shown for 1 H in vivo rat brain signals obtained with the SPECIAL pulse sequence at 9.4 T, and human brain signals obtained, respectively, with STEAM at 4 T and PRESS at 3 T. QUEST-MM is implemented in jMRUI and will be available for public use from version 7.1.

The First Ground Level Enhancement Seen on Three Planetary Surfaces: Earth, Moon, and Mars

AbstractOn 28 October 2021, solar eruptions caused intense and long‐lasting solar energetic particle (SEP) flux enhancements observed by spacecraft located over a wide longitudinal range in the heliosphere. SEPs arriving at Earth caused the 73rd ground level enhancement (GLE) event recorded by ground‐based neutron monitors. In particular, this is also the first GLE event seen on the surface of three planetary bodies, Earth, Moon, and Mars, by particle and radiation detectors as shown in this study. We derive the event‐integrated proton spectrum from measurements by near‐Earth spacecraft and predict the lunar and martian surface radiation levels using particle transport models. Event doses at the lunar and martian surfaces of previous GLE events are also modeled and compared with the current event. This statistical and comparative study advances our understanding of potential radiation risks induced by extreme SEP events for future human explorations of the Moon and Mars.

Total Kinetic Energy of Fission Fragments based on Fission Product Data

Total kinetic energy (TKE) is the physical quantity that must be acquired during a nuclear fission reaction. This energy is used for various purposes, primarily to determine the spectrum of the second proton. This spectrum is advantageous in the design of nuclear reactors. Various techniques for calculating TKE, from microscopic to macroscopic, have been carried out, from statistical to quantum reviews. This whole technique is solely for obtaining TKE accurately. This paper will review the TKE calculation based on the fission products' experimental results. This fission product data can be in the form of raw experimental data or evaluated data. The calculations are carried out within a macroscopic and statistical review framework. The macroscopic view is a liquid drop model, while the statistics use the random number technique. Because the liquid drop model and the random number technique are very standard, this paper does not review them.

Proton formation at absorption of π<sup>–</sup>-meson in a “live” silicon target

The spectra of protons were measured at the absorption of stopped π–-mesons in “live” target—analog of the 28Si target. Based on the data obtained, it was possible to isolate the process without secondary interactions and obtain the spectrum of primary protons from the act of pion absorption on an intranuclear pp pair.

Simulation of large angle backscattering spectra of channeled protons in Geant4

In this work a new open source simulation model based on GEANT4 toolkit is presented that allows the simulation of large angle elastic backscattering spectra of protons in single virgin crystals. The simulation model evaluates the backscattering yield based on the differential cross-section, modified by the close encounter probability with lattice atoms at a specific projectile position. Simulations were performed for 1–2.5 MeV energy protons channeled along the silicon, diamond, silicon dioxide and silicon carbide crystals. The comparison between experimental and simulated curves has shown that the developed model is capable of accurately simulating the channeling backscattering spectra of protons when angular beam spread is considered in the simulations. Although perfect match of the simulated spectra to the experimental ones was not achieved in all cases, the agreement between results is highly promising. The presented model is a proof of concept and further development of the model for the simulation of lattices with defects is underway.

Absolute calibration up to 20 MeV of an online readout CMOS system suitable to detect high-power lasers accelerated protons

We present the design and absolute calibration of a charged particle online readout CMOS system tailored for high-power laser experiments. This system equips a Thomson parabola spectrometer, which is used at the Apollon petawatt scale laser facility to measure the spectra of protons produced by high-intensity laser–target interactions. The RadEye1 CMOS matrices array detectors are paired with a custom triggering system for image grabbing. This allows us to register the proton and ion signals remotely. The repetition rate is presently 1 shot/min, but the frame grabbing enables the system to be compatible with modern high-power lasers running, e.g., at 1 Hz. We detail here the implementation, in the harsh electromagnetic environment of such interactions, of the system, and its absolute calibration, which was performed for proton energies from 4 to 20 MeV.

Reacceleration of Galactic Cosmic Rays beyond the Knee at the Termination Shock of a Cosmic-Ray-driven Galactic Wind

The origin of cosmic rays (CRs) above the knee in the spectrum is an unsolved problem. We present a wind model in which interstellar gas flows along a nonrotating, expanding flux tube with a changing speed and cross-sectional area. CRs from Galactic sources, such as supernova remnants, which are coupled to the plasma via Alfvén waves, provide the main pressure source for driving this outflow. These CRs are then subject to diffusive shock reacceleration at the Galactic wind termination shock, which is located at a distance ∼200 kpc. Some of the highest-energy reaccelerated particles propagate upstream against the wind and can contribute to the petaelectronvolt to exaelectronvolt range of the spectrum. We analyze the conditions under which efficient reacceleration can occur and find that rigidities ∼10–40 PV can be obtained and that the termination shock may account for between 10% and 50% of the proton spectrum measured in IceCube/IceTop experiment. In our model, the termination shock is unable to fully explain the CR spectrum in the petaelectronvolt to exaelectronvolt range. The highest-energy particles that escape downstream from our termination shock, and similar shocks surrounding most galaxies, can be further accelerated by intergalactic shock fronts.

Implications of a Possible Spectral Structure of Cosmic-Ray Protons Unveiled by the DAMPE

The recent observations revealed that the cosmic-ray (CR) proton spectrum showed a complex structure: the hardening at ∼200 GeV and softening at ∼10 TeV. However, so far, the physical origins of this spectral feature remain strongly debated. In this work, we simulate the acceleration of CR protons in a nearby supernova remnant (SNR) by solving numerically the hydrodynamic equations and the equation for the quasi-isotropic CR momentum distribution in the spherically symmetrical case to derive the spectrum of protons injected into the interstellar medium, and then simulate the propagation process of those accelerated CR particles to calculate the proton fluxes reaching the Earth. Besides, we use the DRAGON numerical code to calculate the large-scale CR proton spectrum. Our simulated results are in good agreement with the observed data (including the observed data of proton fluxes and dipole anisotropy). We conclude that the spectral feature of CR protons in this energy band may originate from the superposition of the distribution from the nearby SNR and background diffusive CR component. We find that the release of particles from this nearby SNR has a time delay. Besides, it can be found that the nonlinear response of energetic particles, the release time of CR protons, and age of the local SNR can leave strong signatures in the spectrum of the resulting CR proton fluxes.

Оценка эквивалентной дозы излучения в режиме реального времени по данным спутника GOES

A system has been developed that makes it possible to evaluate the equivalent radiation dose at the altitudes of airliners in real time. A brief description of the calculation methodology is presented, a link is given to an information resource that provides data in the public domain. The result is shown for a typical spectrum of cosmic ray protons obtained from a satellite.

Synthesis and Characterization Studies of new Heterocyclic Azo Compound 2-[2‾-(4,5-Dimethyl thaizolyl azo]-5-Amino Anilin with some Complexes Metal Ions

This work included the preparation of a new ligand of heterogeneous azo ligands derived from thiazole 2- [2‾-(4,5-Dimethyl thaizolyl azo]-5-Amino Anilin (DMeTAAA) and some of its metallic complexes were diagnosed by means of the infrared spectrum, mass spectrum, nuclear magnetic resonance proton spectra, ultraviolet-visible spectrum, thermogravimetric analysis, and in addition to the careful analysis of the elements. Eight metal complexes were prepared by reaction the prepared ligand with Chromium (III), Iron (II), Cobalt (III), Nickel (II), Copper (II), Zinc (II), mercury (II) and silver (I). The effect of the solvent on ligand has been studied and the results have indicated that all the obtained complexes possess high stability. The percentage of metallic ions in the prepared complexes was obtained by the flame atomic absorption spectrometer. A careful analysis of the elements showed a great compatibility between the theoretically calculated and practically obtained ratios. The results of magnetic sensitivity showed that Cr(III),Ni(II) and Cu(II)-complexes possessed magnetic para qualities while the other complexes possessed magnetic dia qualities, as well as the molar conductivity of the prepared complexes was studied and the results showed that all complexes possess the ionic Based on the results obtained, the synthetic formulas of chelated complexes were proposed revealing that the investigated thiazolele azo ligand behaves as a triple ligand.

Search for the Galactic accelerators of cosmic rays up to the knee with the Pevatron test statistic

ABSTRACT The Pevatron test statistic (PTS) is applied to data from γ-ray observatories to test for the origin of cosmic rays (CRs) at energies around the knee of the CR spectrum. Several sources are analysed within hadronic emission models. Previously derived results for RX J1713.7−3946, Vela Jr, and HESS J1745−290 are confirmed to demonstrate the concept, reliability, and advantages of the PTS. It is excluded with a significance more than 5σ that the sources RX J1713.7−3946 and Vela Jr are Pevatrons, while strong indications exceeding 4σ are found for excluding HESS J1745−290 as a Pevatron. The importance to resolve source confusion with high angular resolution observations for Pevatrons searches is demonstrated using PTS for the region containing the SNR G106.3+2.7 and the Boomerang nebula. No statistically significant conclusion with respect to Pevatron associations could be drawn from this region, for the diffuse γ-ray emission around the Galactic Centre, and the unidentified γ-ray sources LHAASO J2108+5157, HESS J1702−420A, and MGRO J1908+06. Assuming the entire γ-ray emission from MGRO J1908+06 and the tail region of SNR G106.3+2.7 are hadronic, a statistical indication exceeding 3σ is found for the underlying proton spectrum to extend beyond 350–400 TeV as a power law. This result can indicate that these sources are proton and helium Pevatrons, in which the accelerated particles contribute to the knee of proton and helium spectra observed at Earth.

Improvements in Resolution of ¹H NMR of solids.

Magic angle spinning (MAS) in 1H NMR has allowed progress from featureless spectra in static samples to linewidths of a few hundreds of Hertz for powdered solids at the fastest spinning rates available today (100-150 kHz). While this is a remarkable improvement, this level of resolution is still limiting to the widespread use of 1H NMR for complex systems. This review will discuss two recent alternative strategies that have significantly improved 1H resolution, when combined with fast MAS. The first is based on anti-z-COSY, a 2D experiment originally used for J decoupling in liquids, which removes residual broadening due to splittings caused by imperfect coherent averaging of MAS. The second strategy is to obtain pure isotropic proton (PIP) spectra in solids, by parametrically mapping any residual broadening due to imperfect averaging into a second dimension of a multidimensional correlation spectrum.