Proton Energy Research Articles

State primary standard for units of absorbed dose and absorbed dose rate of photon, electron, proton radiation and in carbon ion beams, quantity, fuence, fux density and energy of particles in proton beams and heavy charged particles GET 38-2024

The problem of ensuring the accuracy and traceability of the measurement results of the absorbed dose in carbon ion beams, as well as the measurement results of the amount, fluence, flux density and energy of particles in proton and heavy charged particles beams is considered. Until now, in practice, these values have been measured only by indirect methods. The lack of approved measuring instruments for the quantities under consideration and the metrological traceability of measurement results of these quantities to standards did not allow achieving consistency of measurement methods used in practice and confirming the reliability of the results obtained. To solve this problem, three measuring complexes have been developed and created, which are included in the State Primary Standard of units of absorbed dose and absorbed dose rate of photon, electron, proton radiation and in carbon ion beams, quantity, fluence, flux density and energy of particles in proton and heavy charged particles beams GET 38-2024. The measuring complex for reproducing the unit of absorbed dose in carbon ion beams consists of an adiabatic calorimeter, a thermostating system, a data collection and processing system and a vacuum pumping station. To reproduce the unit of energy of protons and heavy charged particles, a complex has been implemented, which includes a total absorption calorimeter, a data collection and processing system, a vacuum pumping station and a particle count determination system based on the use of a Faraday cup. To reproduce the units of fluence and particle flux density in proton and heavy charged particles beams, a measuring complex has been created containing a Faraday cup, a set of collimators and a low current meter. The schemes, the principles and the results of studies of the metrological characteristics of the developed measuring complexes are described. The results are relevant for the field of radiation therapy and radiation resistance tests of the electronic component base used in the space industry.

Y, Yb, and Gd tri-doping on B-site of Ba(Zr, Ce)O3-δ with improved proton conduction performance

Perovskite-type proton conducting electrolytes are garnering significant attention due to its key role in protonic ceramic electrochemical cells (PCEC) and its application in hydrogen sensors (HS) used for metal melt measurements. Developing high proton conduction perovskite materials with good chemical stability is always a worldwide research focus. In this paper, Y, Yb and Gd triple-doping on B-site of BaCeO3-BaZrO3 solid solution were carried out to investigate the effect of gadolinium doping on the performance of protonic conducting electrolytes. BaZr0.1Ce0.7(Y0.5Yb0.5)0.2-xGdxO3-δ (x = 0, 0.1, 0.15 and 0.2), which were also referred as BZCYYbGdx (x = 0, 10, 15 and 20), were synthesized by solid-state reaction at 1600 °C for 10 h. It is found that BZCYYbGd15 has the highest proton conductivity and proton transfer number among the four prepared materials. The proton mobility of BZCYYbGd15 is 4.06 × 10−6 cm2/(Vꞏs) at 800 °C, which increases with an increased temperature. Its proton transfer number is higher than 0.9 at 500 °C under the atmosphere of PH2O = 0.018 atm. A moderate doping of gadolinium increases the temperature threshold for proton conduction. Proton, oxygen vacancy, electron hole and total conductivity activation energies of BZCYYbGd15 under the wet atmosphere are found to be 0.74, 1.58, 1.41 and 0.92 eV, respectively. Furthermore, the chemical stability of pellets is improved after gadolinium doping. This study provides a reference value for future research on high proton conduction electrolytes.

Unveiling the origin of XMM-Newton soft proton flares

Context. Low-energy (< 300 keV) protons entering the field of view of the XMM-Newton telescope scatter with the X-ray mirror surface and might reach the X-ray detectors on the focal plane. They manifest in the form of a sudden increase in the rates, usually referred to as soft proton flares. By knowing the conversion factor between the soft proton energy and the deposited charge on the detector, it is possible to derive the incoming flux and to study the environment of the Earth magnetosphere at different distances, given the wide and elliptical XMM-Newton orbit. Thanks to detailed Geant4 simulations, we were able to build specific soft proton response matrices for MOS and PN. Aims. In this second paper, we present the results of testing these matrices with real data for the first time, while also exploring the seasonal and solar activity effect on the proton environment. The selected spectra are relative to 55 simultaneous MOS and PN observations with flares raised in four different temporal windows: December-January and July-August of 2001-2002 (solar maximum) and 2019-2020 (solar minimum). Methods. We selected and extracted the flare mean spectra and count rates in the 2–11.5 keV energy range for the four epochs. After investigating the rate variations among the MOS1, MOS2, and PN instruments, we fit the X-ray spectra using XSPEC and the proton response matrices. The best-fitting parameters derived for the three instruments were compared in order to obtain the systematic errors. Results. There is no seasonal or solar activity effect on the soft proton mean count rates, but we find large discrepancies in the instrument cross-correlations across the 20 years of satellite operations. In 2001-2002, after a few years of operation, the MOS1 and MOS2 rates are similar, and about 20% with regard to the PN ones. After 20 years, PN does not present any variation in its response, while MOS1 suffers a reduction of ∼30%, in addition to the 30% loss due to the damage of two CCDs, and MOS2 is affected by an even worse degradation (70%). The main result of the spectral analysis is that the physical model representative of the proton spectra at the input of the telescope is a power law. However, a second and phenomenological component is necessary to take into account imprecision in the generation of the matrices at softer (< 5 keV) energies. This component contributes for 21% for the MOS and 5% for the PN to the total flux in the 2–5 keV energy range. Conclusions. This study, which is the first application of the soft proton response matrices to real data, shows coherent results between detectors and allows us to estimate systematic uncertainties in the measured spectra of 3% between the two MOS detectors and of 24% between MOS and PN, together with a systematic in the input flux of about a factor of two. They are all likely due to uncertainties in the proton transmission models, with the presence of additional passive material in front of the front-illuminated MOS, and element deposition on its electrode structure across the mission life. Dedicated studies and laboratory measurements are required for improving the accuracy of the proton response files.

Theoretical investigation of dosimeter accuracy for linear energy transfer measurements in proton therapy: A comparative study of stopping power ratios

BackgroundAccurate measurement of linear energy transfer (LET) is crucial in medical physics, particularly for proton therapy dosimetry. High atomic-number (Zeff) materials such as BaFBr and low-Zeff materials such as Al2O3 and water are commonly used in dosimeters. PurposeTo evaluate the feasibility and accuracy of the use of various dosimetry materials (water, air, Al2O3, aluminum (Al), BaFBr, and oxygen) for measuring LET by comparing their stopping power (ratios) via the Bethe-Bloch theory and semiempirical models. MethodsStopping power ratios were calculated via the PSTAR database for proton energies ranging from 0.01 MeV to 10,000 MeV. The Bethe-Bloch theory with density and shell corrections was used for high-energy protons, whereas a semiempirical model was applied for low-energy protons. Calculations validation involved comparing the computed stopping powers SRIM-2008 and PSTAR for materials such as water, aluminum, air, Al2O3, BaFBr, and oxygen. ResultsThe stopping power water-to-air ratio remains stable, while the Al2O3-to-water and air-to-water ratios highlight their differing attenuation properties. The BaFBr-to-water ratio shows significant material-dependent differences, and the water-to-Al2O3 ratio is particularly relevant for proton therapy dosimetry calculations in medical physics. These results demonstrate consistency across materials but do not inherently confirm the accuracy of LET measurements. However, a comparison of theoretical models with computed stopping powers SRIM-2008 and PSTAR showed strong agreement, particularly for high-energy protons where the Bethe-Bloch theory was applied, suggesting that the models reliably predict stopping power at these energy levels. ConclusionsThis study confirms the feasibility of using high-Zeff materials such as BaFBr and low-Zeff materials such as Al2O3 and water for the use of LET measurements in proton therapy. The results validate the use of the Bethe-Bloch theory, computed stopping powers and semiempirical models in dosimetric applications, enhancing the precision of LET measurements and contributing to improved radiation therapy outcomes.

Interpreting the biological effects of protons as a function of physical quantity: linear energy transfer or microdosimetric lineal energy spectrum?

The choice of appropriate physical quantities to characterize the biological effects of ionizing radiation has evolved over time coupled with advances in scientific understanding. The basic hypothesis in radiation dosimetry is that the energy deposited by ionizing radiation initiates all the consequences of exposure in a biological sample (e.g., DNA damage, reproductive cell death). Physical quantities defined to characterize energy deposition have included dose, a measure of the mean energy imparted per unit mass of the target, and linear energy transfer (LET), a measure of the mean energy deposition per unit distance that charged particles traverse in a medium. The primary advantage of using the “dose and LET” physical system is its relative simplicity, especially for presenting and recording results. Inclusion of additional information such as the energy spectrum of charged particles renders this approach adequate to describe the biological effects of large dose levels from homogeneous sources. The primary disadvantage of this system is that it does not provide a unique description of the stochastic nature of radiation interactions. We and others have used dose-averaged LET (LETd) as a correlative physical quantity to the relative biological effectiveness (RBE) of proton beams. This approach is based on established experimental findings that proton RBE increases with LETd. However, this approach might not be applicable to intensity-modulated proton therapy or other applications in which the proton energy spectrum is highly heterogeneous. In the current study, we irradiated cancer cells with scanning proton beams with identical LETd (3.4 keV/µm) but arising from two different proton energy/LET spectra (a narrow spectrum in group 1 and a widespread heterogeneous spectrum in group 2). Clonogenic survival after irradiation revealed significant differences in RBE at any cell surviving fraction: e.g., at a surviving fraction of 0.1, the RBE was 0.97 ± 0.03 in group 1 and 1.16 ± 0.04 in group 2 (p≤0.01), validating our hypothesis that LETd alone may not adequately indicate proton RBE. Further analysis showed that microdosimetric spectrum (the probability density function of the stochastic physical quantity lineal energy y) was helpful for interpreting observed differences in biological effects. However, more accurate use of microdosimetric spectrum to quantify RBE requires a cell line–specific mechanistic model.

Significance of the proton energy loss mechanism to gold nanoparticles in proton therapy: a Geant4 simulation

The biological effectiveness in proton therapy is only slightly greater than of the treatment by X-ray and hence, many researches have suggested the use of gold nanoparticles for increasing the ionization interactions to produce more secondary electrons and elevate the yield of DNA damage. But the ionization interactions also lead to protons energy loss inside the nanoparticles. The present study shows that, the protons slowed-down by High-Z nanoparticles are responsible for dose enhancement rather than the produced secondary electrons. To this purpose, using Geant4 Monte Carlo tool, one million nanoparticles distributed in a proton irradiated volume and variation of the proton’s spectra and the dose related to this variation has been demonstrated. It was found that, the elevation in proton’s LET values when passing through the gold nanoparticles will lead to a more significant dose enhancement than the increased dose due to the extra secondary electrons. Also, it was found that, the mechanism of protons slowing-down by gold nanoparticles has another useful aspect in proton therapy in which, the dose leakage to surrounding healthy tissues will be reduced which must be considered in future investigations more precisely.

Detection of extended gamma-ray emission in the vicinity of Cl Danks 1 and 2

Abstract We report the detection of high-energy gamma-ray emission towards the G305 star-forming region. Using almost 15 years of observation data from Fermi Large Area Telescope, we detected an extended gamma-ray source in this region with a significance of ∼13σ. The gamma-ray radiation reveals a clear pion-bump feature and can be fitted with the power law parent proton spectrum with an index of −2.5. The total cosmic ray (CR) proton energy in the gamma-ray production region is estimated to be the order of $10^{49}\ \rm erg$. We further derived the CR radial distribution from both the gamma-ray emission and gas distribution and found it roughly obeys the 1/r type profile, though a constant profile is not ruled out. This is consistent with other similar systems and expected from the continuous injection of CRs by the central powerful young massive star cluster Danks 1 or Danks 2 in this region. Together with former detections of similar gamma-ray structures, such as Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and W40, the detection supports the hypothesis that young massive star clusters are CR accelerators.

Effect of Hydrogen on Albedo Neutrons in the Lunar Surface

The remote sensing observations of the lunar soil by using neutron spectroscopy as well as infrared spectroscopy in various studies suggest the presence of hydrogen in the lunar surface, particularly around the lunar polar regions. Additionally, the cosmic ray protons incident on the lunar surface induce the generation of secondary neutrons depending on the composition of the surface soil and the associated density, a certain number of which, called albedo neutrons, leak from the lunar regolith. Motivated by the interaction of the cosmic ray protons with the lunar surface in the absence and presence of hydrogen, a series of GEANT4 simulations are employed in the current study to unveil the influence of hydrogen on the energy spectrum of the albedo neutrons that escape from the lunar surface. Initially, a discrete 69-bin proton energy spectrum between 0.4 and 115 GeV based on the PAMELA spectrometer is implemented into GEANT4. Subsequently, a single-volume lunar surface of 2-m thickness is constructed where it is assumed that a single layer of either 1.6 or 1.93 g/cm^3 constitutes the lunar regolith. The material composition in the present study includes 43.7 wt.% oxygen, 0.3 wt.% sodium, 5.6 wt.% magnesium, 9 wt.% aluminium, 21.1 wt.% silicon, 8.5 wt.% calcium, 1.5 wt.% titanium, 0.1 wt.% manganese, and 10.2 wt.% iron in accordance with another study. Then, 0.1 wt.% hydrogen is introduced by replacing oxygen in order to assess the impact of hydrogen on the secondary neutrons. In the wake of irradiating a lunar surface of 3*2*3 m^3 with a planar vertical PAMELA proton beam of 20*20 cm^2, the depth profile of the generated neutrons as well as the corresponding initial energy spectrum is primarily obtained in the absence and presence of 0.1 wt.% hydrogen by voxelizing the entire geometry with 100 cells of 2-cm thickness. Next, a surface detector is placed at the top of the lunar surface in order to collect the albedo neutrons in both cases, and the energy spectra of the albedo neutrons are acquired in terms of thermal, epithermal, and fast neutrons. From the GEANT4 simulations in this study, it is shown that the presence of 0.1 wt.% hydrogen is observable in each energy regime of the albedo neutrons at the lunar surface, thereby providing an indication about the elemental variation of the lunar soil.

Dosimetry in MRgPT: Impact of magnetic fields on TLD dose response during proton irradiation.

Proton beam therapy, when integrated with MRI guidance, presents complex dosimetric challenges due to interactions with magnetic fields. Prior research has emphasized the nuanced impact of magnetic fields on dosimetry. For thermoluminescent dosimeters (TLDs) the electron-return effect, alongside small air cavities surrounding the pellets, can lead to nonuniform dose distributions. Future MR-guided proton therapy will require reliable methods for end-to-end tests and dosimetric audits, which so far are often performed using TLDs equipped with phantoms. This implicates the necessity of accounting for theseinteractions. This study investigates the influence of magnetic fields on TLDs at two proton energies, using magnetic field strengths of 0, 0.25, and , aiming to clarify their impact on dose measurementaccuracy. The study was conducted at a synchrotron-based ion beam therapy beam line, enhanced by a resistive dipole magnet for creating magnetic fields up to to simulate MR-guided proton therapy. Individual correction factors were applied for TLD measurements. The impact of air gaps on the TLD signal was evaluated using three dedicated TLD holders with air gaps of 0.1, 0.25, and 0.5 mm surrounding the TLD pellets using the highest available proton energy of . Additionally, the influence of the magnetic field strength on the TLD response was evaluated for two proton energies of and . The study found no statistically significant variation in TLD dose response attributable to changes in the air gap or the presence of magnetic fields. A power analysis indicated an upper limit on a potential change in dose-response as small as 1.5%. The findings suggested that the impact of air gap variations and magnetic field strengths on the TLD response was below the detection threshold of TLD sensitivity. This emphasizes the suitability of TLDs for dose measurement in MR-guided proton therapy, indicating that additional correction factors may not be necessary despite the influence of magneticfields.

Direct and Indirect Effects for Radiosensitization of Gold Nanoparticles in Proton Therapy.

The radiosensitization characteristics of gold nanoparticles (GNPs) have been investigated in a single cell irradiated with monoenergetic beams of protons of various energies using TOPAS-nBio, an advanced toolkit of TOPAS. Both direct and indirect effects against single-strand breaks (SSBs) are investigated and their double-strand breaks (DSBs) have been calculated. A single spherical cell interaction with a detailed DNA structure has been modeled and simulated under different conditions such as particle sizes and concentrations of GNPs, their biodistributions and associated proton energies. The physical interaction among protons, suspension water and GNPs has been simulated using a dual physics approach, while the interaction between water radiolysis and OH radicals was considered in the chemical process to save computational time. The present simulations involve irradiating the cell geometry with a dose of 1 Gy. The range of DSBs (Gy-1 Gbp-1) obtained was 2.1 ± 0.09 to 21.74 ± 0.4 for all GNPs of sizes 6-50 nm the proton energies in the range of 5-50 MeV. Regardless of proton energy and GNP size, the calculations showed that the contribution of indirect and hybrid DSBs remains higher in all simulation types than that of direct DSBs. New simulation outcomes of the indirect DSBs illustrate a percentage increase, while we cannot get an increase in the direct and hybrid DSBs in most cases when compared with no GNPs cases. The indirect DSBs provide the highest enhancement factor of 1.89 at 30 nm GNPs in size for 30 MeV protons energy, and the direct and hybrid DSBs indicate a slight increase in enhancement. The work indicates that the use of GNPs increased indirect DNA DSBs, while hybrid DSBs show only a slight increase in enhancement, and no enhancement is shown in direct DNA DSBs. It is significant to consider other mechanisms such as DNA damage repair when investigating DNA damage.

Influence of Initial Proton Energy on the Nonlinear Interactions Between Ring Current Protons and He+ Band EMIC Waves

AbstractThe energy of ring current protons is believed to influence the pitch angle scattering due to electromagnetic ion cyclotron (EMIC) waves and is typically analyzed using quasi‐linear theory. However, nonlinear behavior becomes significant as the wave amplitude intensifies. In this study, we aim to explore how the nonlinear behavior depends on the initial proton energy under various background plasma density conditions. The frequency of EMIC waves is 0.96ΩHe (where ΩHe is the gyrofrequency of He+ at the equator). It is found that the higher energy protons with nonlinear phase trapping experience more resonances, causing these trapped protons to move away from the loss cone more quickly compared to lower energy protons. However, the proportion of phase‐trapped protons significantly decreases as the initial proton energy increases. This declining trend is more pronounced for a background plasma condition in the plasmapause than within the plasmasphere. The number of phase‐trapped protons goes to zero as initial proton energy increases to above approximately 60 keV. Additionally, nonlinear phase bunching is more pronounced for lower energy protons (e.g., below 60 keV) compared to higher energy protons. As a result, both nonlinear phase trapping and phase bunching contribute to larger standard deviations in the net changes of equatorial pitch angle (Δαeq), suggesting a larger pitch agnel diffusion coefficient compared to the prediction of quasi‐linear theory.

Measurement of electromagnetic pulse in laser acceleration enhanced by near-critical density targets

High-power laser interactions with solid targets create an abundance of high-energy charged particles, resulting in the generation of intense electromagnetic pulses (EMPs), which are strongly pertinent to the target parameters. In this study, the characteristics of EMPs generated by relativistic femtosecond laser irradiation of double-layer targets composed of near-critical density carbon nanotube foams (CNFs) and an aluminum (Al) foil are investigated. The results demonstrate that the CNF double-layer targets accelerate proton energy by over 1.6 times compared to a single-layer Al plane target, thereby indirectly amplifying the EMP amplitude by over 3.6 times. The findings are beneficial to gaining insight into EMPs induced by femtosecond laser coupling with near-critical density targets and open a new avenue to achieve tunable EMPs by managing the material and structure of the target to optimize the coupling efficiency between the laser and solid targets.

Development of an algorithm for proton dose calculation in magnetic fields.

The advantages of proton therapy can be further enhanced with online magnetic resonance imaging (MRI) guidance. One of the challenges in the realization of MRI-guided proton therapy (MRPT) is accurately calculating the radiation dose in the presence of magnetic fields. This study aims to develop an efficient and accurate proton dose calculation algorithm adapted to the presence of magnetic fields. An analytical-numerical radiation dose calculation algorithm, Proton and Ion Dose Engine (PRIDE), was developed. The algorithm combines the pencil beam algorithm (PBA) with a novel iterative voxel-based ray-tracing algorithm. The new ray-tracing method uses fewer assumptions and ensures broader applicability for proton beam trajectory prediction in magnetic fields, and has been compared to Wolf's method and Schellhammer's method. The accuracy of PRIDE algorithm was validated on three phantoms and two practical plans (one single-field water plan and one prostate tumor plan) in different magnetic field strengths up to 3.0 T. The validation was performed by comparing the results against the Monte Carlo (MC) simulations, using the global gamma index criteria of 2%/2mm and 3%/3mm with a 10% threshold. PRIDE showed good agreement with MC in homogeneous and slab heterogeneous phantom, achieving gamma passing rates (%GPs) above 99% for 2%/2mm criteria when magnetic field strength is not greater than 1.5 T. Although the agreement decreased for scenarios involving high proton energy (240 MeV) and strong magnetic field (3.0 T), the 2%/2mm %GPs still remained above 98%. In lateral heterogeneous phantom, the accuracy of PRIDE decreased due to the PBA's limitation. For the two practical plans in different magnetic fields, %GPs exceeded 98% and 99% for 2%/2mm and 3%/3mm criteria, respectively. PRIDE can perform efficient and accurate proton dose calculation in magnetic fields up to 3.0 T, and is expected to work as a useful tool for proton dose calculation in MRPT.

Chalcogenides encapsulated Pt-doped carbon quantum dot (Pt@CQD) as a carrier for the controlled release of lapachone: Outlook from theoretical calculations

While cancer remains a significant health concern for humans, and is a serious and life-threatening disease, this research introduces an innovative drug delivery strategy employing platinum-doped carbon quantum dots (Pt@CQD) decorated with chalcogenide (O, S, Te) atoms for targeted delivery of the anti-inflammatory drug lapachone (LPC), which was analysed through density functional theory (DFT) at the ωB97XD/def2svp level of theory. Adsorption studies indicated exothermic behaviour, with negative energies for LPC_Pt@CQD, LPC_OdecPt@CQD, LPC_SdecPt@CQD, and LPC_TedecPt@CQD with corresponding values of −25.549 kcal/mol, −24.583 kcal/mol, −24.629 kcal/mol and − 24.419 kcal/mol respectively, indicating their chemisorption strengths. The quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses highlight weak and partial interactions among the complexes. Significantly, the engineered systems exhibit notable drug-release properties, especially LPC_OdecPt@CQD, where we observed a considerably slight physisorption and an adsorption energy of 10.277 kcal/mol and a protonation energy gap (ΔE) of 2.648 eV which balances effective adsorption and the ability to release the drug when needed. Furthermore, molecular dynamics and reactivity analysis revealed high stability and biological activity respectively among the designed systems, making them promising candidates for therapeutic delivery and holding potential for further in vivo and clinical investigations.

High power target for the High Brilliance Neutron Source

The High Brilliance Neutron Source (HBS) is a High-Current Accelerator-driven Neutron Source (HiCANS) under development at Jülich Centre for Neutron Science - Forschungszentrum Jülich. The unique specifications of the HBS require a neutron target with a high neutron emission able to operate in vacuum with a 70MeV proton beam with 90mA peak current and 1.6% duty cycle leading to an average thermal load of 100kW. A tantalum target of 100cm2 irradiated area with an internal cooling structure which removes the heat quite homogeneously, provides a good compromise between low pressure and high heat transfer and ensures an homogeneous protons energy loss was designed and optimized by means of MCNP, CFD and FEM simulations. Such a target was successfully manufactured and its operational capability was demonstrated by operating it under a heat load of 1kWcm−2 from an electron gun.

Nuclear Transmutation of 99Tc Utilizing Proton Spallation and Compact Subcritical Assembly

An innovative design is introduced for neutron transmutation employing a proton accelerator in conjunction with a compact subcritical system. The transmutation converter comprises a spherical target enveloped by a subcritical assembly. The subcritical assembly consists of a moderator and low-enriched uranium in shell plates. The subcritical assembly has an inner radius of 10 cm and a thickness of 40 or 55 cm. The material used for the target is lead, and beryllium or beryllium oxide is used as a moderator. Low-enriched uranium in the subcritical assembly contains 5% 235U. The transmutation half-life is inversely proportional to the integral of epithermal 99Tc capture rates. The MCNP6 simulation demonstrates that the transmutation half-life is less than 1 year when exposed to 1-GeV protons at 5 mA. Additionally, it is notable that this half-life can be further reduced with increased proton energies and currents. Previous studies have reported that the 99Tc transmutation half-life using fast reactors and an accelerator-driven system ranges from tens to hundred years; this design concept represents a substantial advancement to previous research efforts.

Observations of Kappa Distributions in Solar Energetic Protons and Derived Thermodynamic Properties

In this paper, we model the high-energy tail of observed solar energetic proton energy distributions with a kappa distribution function. We employ a technique for deriving the thermodynamic parameters of solar energetic proton populations measured by the Parker Solar Probe Integrated Science Investigation of the Sun EPI-Hi high-energy telescope, over energies from 10 to 60 MeV. With this technique, we explore, for the first time, the characteristic thermodynamic properties of the solar energetic protons associated with an interplanetary coronal mass ejection (ICME) and its driven shock. We find that: (1) the spectral index or, equivalently, the thermodynamic parameter kappa of solar energetic protons (κ EP) gradually increases, starting from the pre-ICME region (upstream of the CME-driven shock), reaching a maximum in the CME ejecta (κ EP ≈ 3.5), followed by a gradual decrease throughout the trailing portion of the CME; (2) the solar energetic proton temperature and density (T EP and n EP) appear anticorrelated, a behavior consistent with subisothermal polytropic processes; and (3) values of T EP and κ EP appear to be positively correlated, indicating an increasing entropy with time. Therefore, these proton populations are characterized by a complex and evolving thermodynamic behavior, consisting of multiple subisothermal polytropic processes, and a large-scale trend of increasing temperature, kappa, and entropy. This study and its companion study by Livadiotis et al. open up a new set of procedures for investigating the thermodynamic behavior of energetic particles and their shared thermal properties.

Systematic study of theoretical estimation of nuclear reaction cross section of proton-induced reactions on Neodymium target upto 65 MeV using TALYS-1.96 code

Abstract Systematic study of theoretical estimation of nuclear cross section of charged particle induced reactions on rare earth nuclei has been carried out. The production cross section of the $^{150,149,148,146,144,143,141}$Pm and $^{149,147}$Nd nuclei were calculated theoretically via proton induced reaction on neodymium using TALYS (version 1.96) code in the default mode, with different combination of nuclear models as well as using adjusted nuclear model parameters from reaction threshold to the proton energy upto 65 MeV. The theoretically computed results were compared with the experimental results taken from EXFOR database and literature, reported by various research groups. Moreover, the effect of the various Level Density Models (LDMs), Preequilibrium Models (PEs), Optical Model Potentials (OMPs), gamma Strength Functions ($\gamma$SFs) in the cross section calculation were taken into consideration. The present theoretical analysis will help to understand the theory of nuclear reaction models and improve the evaluated nuclear data libraries.

Bonner sphere measurements of high-energy neutron spectra from a 1 GeV/u 56Fe ion beam on an aluminum target and comparison to spectra obtained by Monte Carlo simulations

The goal of this work is to characterize the secondary neutron spectra produced by 1 GeV/u56Fe beam colliding with a thick cylindric aluminum target and to perform a quantitative comparison with simulated results obtained with Monte Carlo codes. The measurements were performed using extended-range Bonner sphere spectrometers at two positions (15° and 40°) with respect to the beam direction. The secondary radiation field was simulated using four Monte Carlo codes (FLUKA, MCNP6, Geant4 and PHITS) and several physical models of nuclei transport and interaction. Neutron and proton energy distributions were simulated for the experimental measurement positions. The simulated neutron spectra, together with data measured with Bonner sphere spectrometers, after carrying out the correction of the contributions induced by the secondary protons, were used as input for the MAXED spectrum unfolding code to obtain the measured neutron spectra. Unfolded neutron spectra were compared with simulated ones to carry out a quantitative analysis of the performance of the chosen Monte Carlo codes and their corresponding physical models. This comparison showed that, because of experimental uncertainties and physical models, there are no unique solutions for each measurement location, but a range of solutions where the true experimental neutron spectra probably lie. The results showed deviations between 4.23% and 8.42% for some simulated spectra. Regarding the total integral values of neutron fluence and ambient equivalent dose, the unfolded neutron spectra showed deviations lower than 2%.

Proton acceleration in plasma turbulence driven by high-energy lepton jets

Abstract The interaction of high energy lepton jets composed of electrons and positrons with background electron-proton plasma is investigated numerically based upon particle-in-cell simulation, focusing on the acceleration processes of background protons due to the development of electromagnetic turbulence. Such interaction may be found in the universe when energetic lepton jets propagate in the interstellar media. When such a jet is injected into the background plasma, the Weibel instability is excited quickly, which leads to the development of plasma turbulence into the nonlinear stage. The turbulent electric and magnetic fields accelerate plasma particles via the Fermi II type acceleration, where the maximum energy both for electrons and protons can be accelerated to much higher than that of the incident jet particles. Because of background plasma acceleration, a collisionless electrostatic shock wave is formed, where some pre-accelerated protons are further accelerated when passing through the shock wave front. Dependence of proton acceleration on the beamplasma density ratio and beam energy is investigated. For a given background plasma density, the maximum proton energy generally increases both with the density and kinetic energy of the injected jet. Moreover, for a homogeneous background plasma, the proton acceleration both via turbulent fields and collisionless shocks is found to be significant. In the case of an inhomogeneous plasma, the proton acceleration in the plasma turbulence is dominant. Our studies illustrate a scenario where protons from background plasma can be accelerated successively by the turbulent fields and collisionless shocks.