Low-energy Protons Research Articles

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.

Enhancing Proton Radiosensitivity of Chondrosarcoma Using Nanoparticle-Based Drug Delivery Approaches: A Comparative Study of High- and Low-Energy Protons

To overcome chondrosarcoma’s (CHS) high chemo- and radioresistance, we used polyethylene glycol-encapsulated iron oxide nanoparticles (IONPs) for the controlled delivery of the chemotherapeutic doxorubicin (IONPDOX) to amplify the cytotoxicity of proton radiation therapy. Human 2D CHS SW1353 cells were treated with protons (linear energy transfer (LET): 1.6 and 12.6 keV/µm) with and without IONPDOX. Cell survival was assayed using a clonogenic test, and genotoxicity was tested through the formation of micronuclei (MN) and γH2AX foci, respectively. Morphology together with spectral fingerprints of nuclei were measured using enhanced dark-field microscopy (EDFM) assembled with a hyperspectral imaging (HI) module and an axial scanning fluorescence module, as well as scanning electron microscopy (SEM) coupled with energy-dispersive X-Ray spectroscopy (EDX). Cell survival was also determined in 3D SW3153 spheroids following treatment with low-LET protons with/without the IONPDOX compound. IONPDOX increased radiosensitivity following proton irradiation at both LETs in correlation with DNA damage expressed as MN or γH2AX. The IONPDOX–low-LET proton combination caused a more lethal effect compared to IONPDOX–high-LET protons. CHS cell biological alterations were reflected by the modifications in the hyperspectral images and spectral profiles, emphasizing new possible spectroscopic markers of cancer therapy effects. Our findings show that the proposed treatment combination has the potential to improve the management of CHS.

Unveiling the origin of XMM-Newton soft proton flare. II. Systematics in the proton spectral analysis

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. 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). 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. 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<!PCT!> with regard to the PN ones. After 20 years, PN does not present any variation in its response, while MOS1 suffers a reduction of sim 30<!PCT!>, in addition to the 30<!PCT!> loss due to the damage of two CCDs, and MOS2 is affected by an even worse degradation (70<!PCT!>). 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 ($<$5keV) energies. This component contributes for 21<!PCT!> for the MOS and 5<!PCT!> for the PN to the total flux in the 2–5 keV energy range. 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<!PCT!> between the two MOS detectors and of 24<!PCT!> 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.

In Situ Unraveling Surface Reconstruction of Ni‐CoP Nanowire for Excellent Alkaline Water Electrolysis

The surface reconstruction behavior of transition metal phosphides precursors is considered as an important method to prepare efficient oxygen evolution catalysts, but there are still significant challenges in guiding catalyst design at the atomic scale. Here, the CoP nanowire with excellent water splitting performance and stability is used as a catalytic model to study the reconstruction process. Obvious double redox signals and valence evolution behavior of the Co site are observed, corresponding to Co2+/Co3+ and Co3+/Co4+ caused by auto‐oxidation process. Importantly, the in situ Raman spectrum exhibits the vibration signal of Co–OH in the non‐Faradaic potential interval for oxygen evolution reaction, which is considered the initial step in reconstruction process. Density functional theory and ab initio molecular dynamics are used to elucidate this process at the atomic scale: First, OH− exhibits a lower adsorption energy barrier and proton desorption energy barrier at the configuration surface, which proposes the formation of a single oxygen (–O) group. Under a higher –O group coverage, the Co–P bond is destroyed along with the POx groups. Subsequently, lower P vacancy formation energy confirm that the Ni‐CoP configuration can fast transform into a highly active phase. Based on the optimized reconstruction behavior and rate‐limiting barrier, the Ni‐CoP nanowire exhibit an excellent overpotential of 1.59 V at 10 mA cm−2 for overall water splitting, which demonstrates low degradation (2.62%) during the 100 mA cm−2 for 100 h. This work provide systematic insights into the atomic‐level reconstruction mechanism of transition metal phosphides, which benefit further design of water splitting catalysts.

Chemical Characterization of Coal: Quality Control and Applications of Nuclear Analytical Methods Utilizing Neutrons (Thermal and Fast) and Low Energy Protons from Accelerators

Chemical Characterization of Coal: Quality Control and Applications of Nuclear Analytical Methods Utilizing Neutrons (Thermal and Fast) and Low Energy Protons from Accelerators

Unveiling the origin of XMM-Newton soft proton flares. I. Design and validation of a response matrix for proton spectral analysis

Low-energy ($<$ 300 keV) protons entering the field of view of XMM-Newton can scatter with the X-ray mirror surface and reach the focal plane. They are observed in the form of a sudden increase in the background level, the so-called soft proton flares, affecting up to 40<!PCT!> of the mission observing time. Soft protons can hardly be disentangled from true X-ray events and cannot be rejected on board. All future high throughput grazing incidence X-ray telescopes operating outside the radiation belts are potentially affected by soft proton-induced contamination that must be foreseen and limited since the design phase. In-flight XMM-Newton 's observations of soft protons represent a unique laboratory to validate and improve our understanding of their interaction with the mirror, optical filters, and X-ray instruments. At the same time, such models would link the observed background flares to the primary proton population encountered by the telescope, converting XMM-Newton into a monitor for soft protons. We built a Geant4 simulation of XMM-Newton including a verified mass model of the X-ray mirror, the focal plane assembly, and the EPIC MOS and pn-CCDs. Analytical computations and, when available, laboratory measurements collected from literature were used to verify the correct modelling of the proton scattering and transmission to the detection plane. Similarly to the instrument X-ray response, we encoded the energy redistribution and proton transmission efficiency into a redistribution matrix file (RMF), mapping the probability that a proton from 2 to 300 keV is detected in a certain detector channel, and an auxiliary response file (ARF), storing the grasp towards protons. Both files were formatted according to the standard NASA calibration database and any compliant X-ray data analysis tool can be used to simulate or analyse soft proton-induced background spectra. An overall systematic uncertainty of 30<!PCT!> was assumed on the basis of the estimated accuracy of the mirror geometry and transmission models. For the validation, three averaged soft proton spectra, one for each filter configuration, were extracted from a collection of 13 years of MOS observations of the focused non X-ray background and analysed with Xspec . A similar power-law distribution is found for the three filter configurations, plus black-body-like emission below tens of keV used as a correction factor, based on the dedicated spectral analysis of 55 in-flight proton flares presented in Paper II. The best-fit model is in agreement with the power-law distribution predicted from independent measurements for the XMM-Newton orbit, spent mostly in the magnetosheath and nearby regions. For the first time we are able to link detected soft proton flares with the proton radiation environment in the Earth's magnetosphere, while proving the validity of the simulation chain in predicting the background of future missions. Benefiting from this work and contributions from the Athena instrument consortia, we also present the response files for the Athena mission and updated estimates for its focused charged background.

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.

Development of a compact magnetic spectrometer for use at the OMEGA Laser Facility and the National Ignition Facility.

Measurement of proton spectra is an important diagnostic for a variety of high energy density physics experiments. Current diagnostics are either not designed to capture the spectrum of low-energy protons or are unsuitable for high debris experiments. To bridge the gap, a new CR-39 based compact magnetic spectrometer (MagSpec) has been developed to measure proton spectra in the 1-20MeV energy range, with a particular focus on the low-energy (1-6MeV) spectrum, for use in experiments at the OMEGA Laser Facility and the National Ignition Facility (NIF). In the MagSpec diagnostic, protons of different energies are dispersed as they pass through a magnetic field before impinging on a differentially filtered CR-39 surface, resulting in a spatial distribution of CR-39 tracks that corresponds to the energy spectrum. In this paper, we discuss details of the design and implementation of MagSpec on the NIF and OMEGA.

МГД-волны в области предфронта межпланетных ударных волн 6 и 7 сентября 2017 г.

We analyze strong space weather disturbances during first ten days of September 2017, using the geomagnetic Dst index, parameters of normals to interplanetary shock fronts, direct measurements of interplanetary magnetic field, solar wind, and cosmic ray parameters. By applying spectral analysis methods to interplanetary medium data, we analyze MHD waves at the pre-front of two interplanetary shocks responsible for geomagnetic disturbances on September 6 and 7, 2017. The main results are as follows: the contribution of three branches of MHD waves (Alfvén, fast and slow magnetosonic) to the observed spectrum of the interplanetary magnetic field modulus has been established. We have confirmed the conclusion that the generation of Alfvén waves and fast magnetosonic waves is due to the presence of low-energy proton fluxes (Ep~1 MeV) at the pre-front of interplanetary shocks. We have also discovered a predominant contribution of slow magnetosonic waves to the observed spectrum of the interplanetary magnetic field modulus, but its reason is yet unknown. It is noted that different orientations of the normals to the interplanetary shock fronts and to the direction of the interplanetary magnetic field average vector on spacecraft located fairly close to each other may indicate waviness of the shock front structure.

MHD waves at the pre-front of interplanetary shocks on September 6 and 7, 2017

We analyze strong space weather disturbances during first ten days of September 2017, using the geomagnetic Dst index, parameters of normals to interplanetary shock fronts, direct measurements of interplanetary magnetic field, solar wind, and cosmic ray parameters. By applying spectral analysis methods to interplanetary medium data, we analyze MHD waves at the pre-front of two interplanetary shocks responsible for geomagnetic disturbances on September 6 and 7, 2017. The main results are as follows: the contribution of three branches of MHD waves (Alfvén, fast and slow magnetosonic) to the observed spectrum of the interplanetary magnetic field modulus has been established. We have confirmed the conclusion that the generation of Alfvén waves and fast magnetosonic waves is due to the presence of low-energy proton fluxes (Ep~1 MeV) at the pre-front of interplanetary shocks. We have also discovered a predominant contribution of slow magnetosonic waves to the observed spectrum of the interplanetary magnetic field modulus, but its reason is yet unknown. It is noted that different orientations of the normals to the interplanetary shock fronts and to the direction of the interplanetary magnetic field average vector on spacecraft located fairly close to each other may indicate waviness of the shock front structure.

Millicharged particles from proton bremsstrahlung in the atmosphere

Light millicharged particles can be copiously produced from meson decays in cosmic ray collisions with the atmosphere, leading to detectable signals in large underground neutrino detectors. In this paper we study a new channel for generating atmospheric millicharged particles, the proton bremsstrahlung process. We find that the proton bremsstrahlung process leads to a significantly higher flux of millicharged particles compared to meson decays and, for certain masses, results in a one-order-of-magnitude improvement in the flux. Consequently, Super-K constraints on ε2 for sub-GeV MCPs are improved by half order of magnitude. We further note that the study on the proton bremsstrahlung process can be extended to a variety of new physics particle searches in atmospheric collisions and in low energy proton accelerators.

Characteristics of radiation belt energetic protons and the movement of their core location in response to geomagnetic disturbances

The energetic protons trapped within the Earth's radiation belt play a crucial role in substantially impacting the behavior of the ring current, which in turn affects the dynamics of energetic particles. Here, we statistically analyze and discuss the global distributions and temporal evolutions of them at energies from 55 keV to 489 keV by using 7-year (2012–2019) observations by radiation belt storm probes ion composition experiment onboard Van Allen Probes. The observations show that low-energy protons (55–148 keV) are distributed at higher L shells (L > 4), which can deeply penetrate during intense storms. The high-energy protons (221–489 keV) are mainly located at L < 4.5 and are comparably stable. Moreover, the core location (i.e., Lc, the L shell with the peak flux) of them is typically energy-dependent and can be displaced due to geomagnetic storms. Detailed analysis reveals that the Lc for low-energy protons is primarily outside the plasmapause location (Lpp), which can rapidly radially move. However, the Lc for high-energy protons is essentially inside Lpp and is harder to move. The Lc for intermediate-energy protons exhibits fluctuations around Lpp, indicating a clear competition between source and loss processes. In addition, alternative mechanisms, such as wave–particle interactions, are primarily responsible for the gradual variation of them after storms. Our study provides the total configuration of the radiation belt energetic protons measured in the Van Allen Probe era, which would be useful for better understanding the variation of trapped particles in the inner magnetosphere.

Absolute energy-dependent scintillating screen calibration for real-time detection of laser-accelerated proton bunches.

Laser-plasma accelerators (LPAs) can deliver pico- to nanosecond long proton bunches with ≳100 nC of charge dispersed over a broad energy spectrum. Increasing the repetition rates of today's LPAs is a necessity for their practical application. This, however, creates a need for real-time proton bunch diagnostics. Scintillating screens are one detector solution commonly applied in the field of electron LPAs for spatially resolved particle and radiation detection. Yet their establishment for LPA proton detection is only slowly taking off, also due to the lack of available calibrations. In this paper, we present an absolute proton number calibration for the scintillating screen type DRZ High (Mitsubishi Chemical Corporation, Düsseldorf, Germany), one of the most sensitive screens according to calibrations for relativistic electrons and x rays. The presented absolute light yield calibration shows an uncertainty of the proton number of 10% and can seamlessly be applied at other LPA facilities. For proton irradiation of the DRZ High screen, we find an increase in light yield of >60% compared to reference calibration data for relativistic electrons. Moreover, we investigate the scintillating screen light yield dependence on proton energy since many types of scintillators (e.g., plastic, liquid, and inorganic) show a reduced light yield for increased local energy deposition densities, an effect termed ionization quenching. The ionization quenching can reduce the light yield for low-energy protons by up to ∼20%. This work provides all necessary data for absolute spectral measurements of LPA protons with DRZ High scintillating screens, e.g., when used in the commonly applied Thomson parabola spectrometers.

A simulation study of irradiation effect on InAs/GaAsSb type II quantum dot structures

Particles in space cause irradiation damage to the solar cells (SCs), resulting in the degradation of their performance. Quantum dot solar cells (QDSCs) have higher theoretical efficiency and better irradiation resistance than the conventional GaAs SCs, which makes them highly promising for application in space. In this paper, we study the proton irradiation effect on InAs/GaAs0.8Sb0.2 QDSCs by SRIM program. The simulation result shows that the InAs/GaAs0.8Sb0.2 QDSCs have fewer vacancies than GaAs SCs when irradiated with low-energy proton, which indicates that the InAs/GaAs0.8Sb0.2 QDSCs have better anti-irradiation characteristics. The study about displacements per atom and proton concentration in two SCs shows that protons with low energy and high irradiation fluences will cause more serious damage in InAs/GaAs0.8Sb0.2 QDSCs. In addition, the proton incident angle affects the vacancy distribution, while the number of QD layers has little effect on it.

Closer scrutiny of cosmic ray proton energy losses

The percent-level precision attained by modern cosmic ray (CR) observations motivates reaching a comparable or better control of theoretical uncertainties. Here we focus on energy-loss processes affecting low-energy CR protons (∼0.1–5 GeV), where the experimental errors are small and collisional effects play a comparatively larger role with respect to collisionless transport ones. We study three aspects of the problem: (i) We quantitatively assess the role of the nuclear elastic cross section, for the first time, providing analytical formulas for the stopping power and inelasticity; (ii) We discuss the error arising from treating both elastic and pion production inelastic interactions as continuous energy loss processes, as opposed to catastrophic ones. The former is the approximation used in virtually all modern numerical calculations; (iii) We consider subleading effects such as relativistic corrections, radiative and medium processes in ionization energy losses. Our analysis reveals that neglecting (i) leads to errors close to 1%, notably around and below 1 GeV, neglecting (ii) leads to errors reaching about 3% within the considered energy range, (iii) contributes to a minor effect, gauged at the level of 0.1%. Consequently, while (iii) can currently be neglected, (ii) warrants consideration, and we also recommend incorporating (i) into computations. We conclude with some perspectives on further steps to be taken towards a high-precision goal of theoretical CR predictions regarding the treatment of energy losses. Published by the American Physical Society 2024

Nuclear elastic scattering of protons below 250 MeV in FLUKA v4-4.0 and its role in single-event-upset production in electronics

FLUKA is among the general-purpose codes for the Monte Carlo simulation of radiation transport that are routinely employed to estimate the production of single-event-upsets (SEUs) in commercial static random access memories (SRAMs) exposed to radiation. Earlier studies concerning the production of SEUs in commercial SRAMs under proton irradiation revealed very good agreement between experimental measurements and FLUKA estimates of the SEU production cross section for proton energies above 20-30 MeV. However, at lower proton energies, where the cross section for SEU production in such low-critical-charge components increases drastically, a FLUKA underestimation of up to two orders of magnitude was observed. Preliminary analyses indicated that this underestimation was in great measure due to the lack of nuclear elastic scattering of protons below 10 MeV in FLUKA up to version 4-3.4. To overcome this limitation, a new model for the nuclear elastic scattering of protons has been developed, combining partial-wave analyses and experimental angular distributions. This newly developed model has been included in FLUKA v4-4.0, and leads to an order-of-magnitude improvement in the agreement between FLUKA and experimental cross sections for the production of SEUs in SRAMs under proton irradiation in the 1–10 MeV energy domain.

Influence of electrical field on the susceptibility of gallium nitride transistors to proton irradiation

Radiation susceptibility of electronic devices is commonly studied as a function of radiation energetics and device physics. Often overlooked is the presence or magnitude of the electrical field, which we hypothesize to play an influential role in low energy radiation. Accordingly, we present a comprehensive study of low-energy proton irradiation on gallium nitride high electron mobility transistors (HEMTs), turning the transistor ON or OFF during irradiation. Commercially available GaN HEMTs were exposed to 300 keV proton irradiation at fluences varying from 3.76 × 1012 to 3.76 × 1014 cm2, and the electrical performance was evaluated in terms of forward saturation current, transconductance, and threshold voltage. The results demonstrate that the presence of an electrical field makes it more susceptible to proton irradiation. The decrease of 12.4% in forward saturation and 19% in transconductance at the lowest fluence in ON mode suggests that both carrier density and mobility are reduced after irradiation. Additionally, a positive shift in threshold voltage (0.32 V and 0.09 V in ON and OFF mode, respectively) indicates the generation of acceptor-like traps due to proton bombardment. high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy analysis reveal significant defects introduction and atom intermixing near AlGaN/GaN interfaces and within the GaN layer after the highest irradiation dose employed in this study. According to in-situ Raman spectroscopy, defects caused by irradiation can lead to a rise in self-heating and a considerable increase in (∼750 times) thermoelastic stress in the GaN layer during device operation. The findings indicate device engineering or electrical biasing protocol must be employed to compensate for radiation-induced defects formed during proton irradiation to improve device durability and reliability.

Detection of fluorescent low-energy proton tracks in lithium fluoride crystals

The exploitation of visible radiophotoluminescence in lithium fluoride (LiF) crystals, due to local aggregate point defects produced by ionizing radiation in the crystal lattice, is demonstrated for fluorescent imaging of single tracks of protons at low energies. LiF crystals were irradiated perpendicularly with respect to nearly monochromatic, collimated proton beams at the energies of about 1 MeV in a fluence range from ∼5.8 × 105 p/cm2 up to ∼3.4 × 107 p/cm2 and of about 2.6 MeV in a fluence range from ∼9.6 × 105 p/cm2 up to ∼4.7 × 106 p/cm2. The fluence values were estimated by detecting and automatically counting the tracks on the images acquired with a fluorescence microscope at high magnification; they were found to be in agreement with those obtained using CR39 plastic detectors irradiated under the same experimental conditions. Despite the very short range in matter of these charged particles, by focusing the excitation blue light at discrete depths in the irradiated LiF crystals, an estimate of the proton energies was also obtained. These first results are encouraging for the utilization of LiF crystals as fluorescent nuclear track detectors under typical conditions employed in ion radiobiology.

Proton spectroscopy for 11B(p,α)2α fusion reaction with RCF films: calibration and unfolding procedure

The reaction occurring between protons and 11B isotope (p+11B → 3α+8.7 MeV) has recently attracted attention as a possible candidate to overcome the generation of high-energy neutrons via the more studied Deuterium-Tritium fusion reaction. Since the early 2000s, several experiments have been carried out to investigate the viability of triggering this aneutronic reaction in laser-target interaction schemes. During these experiments, the total number of escaping α particles is measured to infer fusion reaction efficiency. However, the accurate detection of α particles in such experiments poses a real challenge.In this scenario, RadioChromic Films(RCFs) arranged in a stack configuration can be used for the fluence and energy spectra reconstruction of generated protons, being this mandatory information in both “pitcher-catcher” and “in plasma” p-11B irradiation schemes. Nevertheless, RCF response exhibits a dependence on Linear Energy Transfer (LET), which leads to an underestimation of the response in high-LET conditions. This can result in dosimetric errors if not properly taken into account.In this work, an analytical procedure able to reconstruct the incident energy spectra in an RCF stack was developed and validated thanks to a calibration procedure that was established for high and low proton energy (4–60 MeV) beams to properly reconstruct the incident spectra in the “pitcher-catcher” irradiation scheme.

CR-39 track detector calibration with H and He beams for applications in the p-11B fusion reaction

The 11B(p,α)2α reaction, generating three alpha particles, emerges as a promising alternative or complementary route for clean and efficient energy generation. A comprehensive understanding of reaction dynamics, energy distribution of emitted particles, and optimization of fusion efficiency requires precise diagnostic methods. CR39 detectors, being highly sensitive to ions and neutrons while remaining transparent to low fluxes of electrons and gammas, are extensively utilized as primary Solid State Nuclear Track Detector devices in laser-plasma environments. This study presents the CR-39 track detector calibration to low-energy protons and alpha particles. CR-39 irradiation took place at INFN-LNL (Istituto Nazionale di Fisica Nucleare — Laboratori Nazionali di Legnaro, Legnaro, Italy) across a range of energies (≥ 80 keV) up to a few MeV, employing various etching times with a NaOH solution. The observed discrepancy in particle diameters, related to a specific etching time, presents a promising avenue for distinguishing alpha particles from proton contributions. This finding holds potential for future practical applications in the study of 11B(p,α)2α fusion reactions.