Incident Proton Energy Research Articles

Non-radioactive elements for prompt gamma enhancement in proton therapy

Regardless of advanced Prompt Gamma (PG) techniques developed to monitor proton range in-vivo, poor PG statistics downgrade the potential of their clinical implementation. We propose injection of the non-radioactive elements 19F, 17O, 127I in a tumor area to enhance the PG production of 4.44 MeV and 6.13 MeV prompt gamma rays emitted after proton irradiation that have been correlated with the accurate monitoring of proton range during treatment. We simulated the interaction of 75 MeV, 100 MeV and 200 MeV incident proton beams in a co-centric cylindrical geometry phantom, where the outer cylinder was filled with 100% water and the inner cylinder (hypothetical tumor area) that is leveled with respect to the outer cylinder was filled with water containing 0.1%–20% weight fractions of each of the tested elements. We demonstrate that the proposed technique affects the PG statistics with results varying with the incident proton beam energy and mixture composition. PG enhancement in the energy range that facilitates proton range monitoring in-vivo is theoretically feasible after injecting an optimal amount of the non-radioactive element for a specific incident proton energy.

Microscopic spin orbit analysis for proton+9Be scattering

microscopic folded potentials for both the real central and the spin-orbit (SO). For the imaginary central, we used surface Woods-Saxon (WS) potential. We aimed to test the microscopic SO potential based on the M3Y effective nucleon-nucleon (NN) interaction for the light system p+$^9$Be. The present calculation showed that the microscopic SO potential is satisfactory reproduce $A_y$ above 8 MeV and qualitatively reproduced $A_y$ below 8 MeV. In addition, we found that the calculated real central potentials are successfully reproduced the $d\sigma/d\Omega$ for all the considered energies. From the present analysis, we excepted that the present microscopic SO potential could reproduce successfully the $A_y$ for p+nucleus as the incident proton energy increases above 10 MeV.

Proton range monitoring using 13N peak for proton therapy applications.

The Monte Carlo method is employed in this study to simulate the proton irradiation of a water-gel phantom. Positron-emitting radionuclides such as 11C, 15O, and 13N are scored using the Particle and Heavy Ion Transport Code System Monte Carlo code package. Previously, it was reported that as a result of 16O(p,2p2n)13N nuclear reaction, whose threshold energy is relatively low (5.660 MeV), a 13N peak is formed near the actual Bragg peak. Considering the generated 13N peak, we obtain offset distance values between the 13N peak and the actual Bragg peak for various incident proton energies ranging from 45 to 250 MeV, with an energy interval of 5 MeV. The offset distances fluctuate between 1.0 and 2.0 mm. For example, the offset distances between the 13N peak and the Bragg peak are 2.0, 2.0, and 1.0 mm for incident proton energies of 80, 160, and 240 MeV, respectively. These slight fluctuations for different incident proton energies are due to the relatively stable energy-dependent cross-section data for the 16O(p,2p2n)13N nuclear reaction. Hence, we develop an open-source computer program that performs linear and non-linear interpolations of offset distance data against the incident proton energy, which further reduces the energy interval from 5 to 0.1 MeV. In addition, we perform spectral analysis to reconstruct the 13N Bragg peak, and the results are consistent with those predicted from Monte Carlo computations. Hence, the results are used to generate three-dimensional scatter plots of the 13N radionuclide distribution in the modeled phantom. The obtained results and the developed methodologies will facilitate future investigations into proton range monitoring for therapeutic applications.

Bragg's additivity rule and core and bond model studied by real-time TDDFT electronic stopping simulations: The case of water vapor

The electronic stopping power (Se) of water vapor (H2O), hydrogen (H2) and oxygen (O2) gases for protons in a broad range of energies, centered in the Bragg peak, was calculated using real-time time-dependent density functional theory (rt-TDDFT) simulations with Gaussian basis sets. This was done for a kinetic energy of incident protons (Ek) ranging from 1.56 keV/amu to 1.6 MeV/amu. Se was calculated as the average over geometrically pre-sampled short ion trajectories. The average Se(Ek) values were found to rapidly converge with 25–30 pre-sampled, 2 nm-long ion trajectories. The rt-TDDFT Se(Ek) curves were compared to experimental and SRIM data, and used to validate the Bragg's Additivity Rule (BAR). Discrepancies were analyzed in terms of basis set effects and omitted nuclear stopping at low energies. At variance with SRIM, we found that BAR is applicable to our rt-TDDFT simulations of 2H2 + O2 → 2H2O without scaling for Ek > 40 keV/amu. The hydrogen and oxygen Core and Bond (CAB) contributions to electronic stopping were calculated and found to be slightly smaller than SRIM values as a result of a red-shift in our rt-TDDFT Se(Ek) curves and a re-distribution of weights due to some bond contributions being neglected in SRIM.

Collision site effect on the radiation dynamics of cytosine induced by proton

By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions (TDDFT-MD) nonadiabatically in real time, we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 eV to 1000 eV. To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine, two collision sites are specially considered, which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine. Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified. It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations, which are 14.2% and 21.1% of the incident energy respectively. However, the scattering angles show different behaviors in these two situations when the incident kinetic energy increases. When proton collides with O, the scattering angle of proton is larger and the energy lost is more, while proton captures less electrons from O. The calculated fragment mass distribution shows the high counts of the fragment mass of 1, implying the production of H+ fragment ion from cytosine even for proton with the incident energy lower than keV. Furthermore, the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.

Genetic algorithm-based optimization of a target for the production of atmospheric-like neutrons via 100 MeV proton beam

This paper presents the optimization of a white neutron target for 100 MeV proton beam to produce a fast neutron spectrum shape similar to that of the atmospheric neutron at ground level. The neutron target consists of 0.5 mm-thick discs consecutively placed in front of a cooling water channel. A sensitivity analysis is performed with different materials to assimilate resulting neutron spectrum with the ground-level cosmic ray-induced neutron spectrum by applying the genetic algorithm (GA). Optimization of the spectrum is conducted in consideration of neutron impact to semiconductor devices. To reconstruct a target-generated neutron spectrum, parametrization on neutron generation and stopping power by target material and position is configured. The loss function in the GA is defined to evaluate similarity between the target neutron spectrum and the atmospheric neutron spectrum. The GA is modeled with a package of consecutive discs as a gene for optimization, and the length and material of target for each disc are decided throughout generations. As a result, the target is configured with six different materials, with approximately half of the weighted deviation of atmospheric neutrons being compared with any other single-solid neutron target. The GA-based optimization process shown here suggests further use for designing targets with other incident proton energies or neutron spectra for various applications.

Estimation of energy and angle of incident protons from three-dimensional track profiles on CR-39 detectors

The aim of this study was to establish a new method for estimating the energy and angle of incident protons based on the three-dimensional profile of nuclear tracks. An inverse growth approach was developed to obtain the latent track from the etched track pit. The energy and angle of the incident protons can be estimated by determining the critical point (end point of the particle trajectory). The estimated incident energies and angles were in good agreement with the pre-set values for the simulated and experimental data. Compared with the pre-set values, the deviation of the energies and angles for 1–3 MeV protons were within ±0.3 MeV and ±5.0°, respectively. This study provides a valuable reference for extracting energy and angle information from 3-D profiles of a nuclear track, and is expected to be beneficial in reconstruction of energy spectra.

Determinations of fission cross-sections and fission yields from proton induced fission reactions of 232Th, 233,235,236,238U, 237Np and 239Pu

In this work, the proton induced fission reaction cross-sections and fission yields are calculated for some actinides [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] using the fission barrier models of the TALYS 1.95 code. Cross-sections and fission yield calculations are carried out up to 100 MeV incident proton energies. The calculation results are compared with the available experimental data in the EXFOR library. In addition, a relative variance analysis of fission barrier models was done to determine the fission barrier model whose results best matched with the experimental results. Among the fission barrier models, the best agreement with the experimental data is obtained from the rotating-finite-range fission barrier model calculation for the [Formula: see text] reaction of the studied nuclei having the atomic mass number larger than 230. On the other hand, fission barrier heights for the studied reactions are determined using the same models.

Impact of Be7 breakup on the Li7(p,n) neutron spectrum

The formation of continuum neutron distribution in $^{7}\mathrm{Li}(p,n)$ has been identified as due to the coupling of the $^{7}\mathrm{Be}$ breakup levels to the final state of the reaction. The continuum neutron spectra produced by the $^{7}\mathrm{Li}(p,n)$ reaction has been estimated by measuring the double differential cross sections for continuum and resonant breakup of $^{7}\mathrm{Be}$, through the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}^{*}$ reaction at 21 MeV of proton energy. The breakup contributions from continuum and $5/{2}^{\ensuremath{-}}$, $7/{2}^{\ensuremath{-}}$ states of $^{7}\mathrm{Be}$ have been identified. The measured double differential cross sections have been reproduced through continuum-discretized coupled channel-coupled reaction channel calculations. The cross sections were projected to neutron spectrum using the Monte Carlo approach and validated using experimentally measured $^{3}\mathrm{He}$ gated neutron spectra. $^{7}\mathrm{Li}(p,n)$ neutron spectrum at 20 MeV incident proton energy measured by McNaughton et al. [Nucl. Instrum. Methods 130, 555 (1975)] has been reproduced by adapting estimated model parameters for the reaction.

Neutron yield calculation of p-Li thick target by using PHITS with JENDL-4.0/HE and ENDF/B-VII for BNCT application

ABSTRACT The lithium thick target bombed with low-energy protons is one of the promising neutron sources for the Boron Neutron Capture Therapy (BNCT). The benchmark calculations of the neutron Thick Target Yield (TTY) of the lithium target are conducted by the Particle and Heavy Ion Transport Code System PHITS with ACE formatted files of JENDL-4.0/HE and ENDF/B-VII and the DROSG-2000 code for the incident proton energy of around 3 MeV. Also, neutron TTY of the lithium thick target with a titanium window is evaluated for the Nagoya University Accelerator-driven Neutron Source (NUANS). Finally, the TTY evaluated with PHITS is applied for the neuron transport calculation for the Beam Shaping Assembly (BSA) of NUANS. As a conclusion, it is considered that ENDF/B-VII is more feasible than JENDL-4.0/HE for the 7Li(p,n)7Be reaction around 3 MeV of the proton energy.

Development of a storage phosphor imaging system for proton pencil beam spot profile determination.

Accurate two-dimensional (2D) profile measurements at submillimeter precision are necessary for proton beam commissioning and periodic quality assurance (QA) purposes and are currently performed at our institution with a commercial scintillation detector (Lynx PT) with limited means for independent checks. The purpose of this work was to create an independent dosimetry system consisting of an in-house optical scanner and a BaFBrI:Eu2+ storage phosphor dosimeter by: (a) determining the optimal settings for the optical scanner, (b) measuring 2D proton spot profiles with the storage phosphors, and (c) comparing them to similar measurements using a commercial scintillation detector. An in-house 2D laboratory optical scanner was constructed and spatially calibrated for accurate 2D photostimulated luminescence (PSL) dosimetry. Square 5×5cm2 BaFBrI:Eu2+ dosimeter samples were uniformly irradiated with line scans performed to determine the physical and electronic scanner settings resulting in the highest signal-to-noise ratios (SNR) at a sub-millimeter spatial resolution. The resultant spatial resolution of the scanner was then quantitatively assessed by measuring (a) line pairs on a standard X-ray lead bar phantom and (b) modulation transfer functions. Following this, 2D proton spot profiles from a Mevion S250i Hyperscan proton unit were obtained at 1, 10, 20, 30, 40, and 50 monitor unit (MU) settings at maximum energy (E0 =227.1MeV) and compared to baseline profiles from a commercial scintillation detector, where 1MU is calibrated to deliver 1Gy absolute proton dose-to-water under reference conditions, that is, 41×41 proton spots uniformly spaced by 0.25cm within a 10×10cm2 square field size at maximum energy (227.1MeV) in water at depth of 5cm at isocenter. The dosimetric system's sensitivities to (a) ±1mm positional shifts and (b) ±0.3mm beam lateral spread changes were quantitatively evaluated through a Gaussian fitting of the crossline and inline plots of the respective artificially shifted beam profiles. The physical scanner settings of (a) Δτ=27ms time interval between data samples, (b) vx =1.235cm/s scanning speed, (c) 1% laser transmission (0.02mW power) and (d) (Δx, Δy)=(0.33, 0.50mm) pixel sizes with electronic settings of (a) 300 microseconds time constant, (b) normal dynamic reserve, (c) 24dB/oct low pass filter slope, and (d) 160Hz chopping frequency resulted in the highest SNR while maintaining sub-millimeter spatial resolution. The BaFBr0.85 I0.15 :Eu2+ storage phosphor dosimeters were linear from 1 to 50MU and their profiles did not saturate up to 150MU. The scanner was able to detect lateral displacements of ±1mm in both the crossline and inline directions and ±0.3mm beam spread changes that were artificially introduced by varying the incident proton energy. Specific to our proton unit, proton energy changes of ±1MeV can also be detected indirectly via beam spread measurements. Our combined dosimetric system including an in-house laboratory optical scanner and reusable BaFBr0.85 I0.15 :Eu2+ storage phosphors demonstrated a sufficient spatial resolution and dosimetric accuracy to support its use as an independent proton spot measurement dosimeter system. Its wide dynamic range allows for other versatile applications such as proton halo measurements.

Influence factors of resolution in laser accelerated proton radiography and image deblurring

Contact imaging based on MeV energy laser accelerated protons is studied in this paper. First, we show that both external structures and the internal organs of ants can be distinguished with micrometer spatial resolution by proton radiography. Then, we systematically study several specific influence factors and their coupled effects on the spatial resolution of proton radiography, i.e., the accumulated shot number, the proton irradiation dose, the different types of detectors, and the incident proton energy, using two specially designed resolution calibration targets. Under our experimental conditions with MeV protons, the best resolution obtained with the radiochromic film is 20 μm, and that with the solid-state nuclear-track detector (CR39) is 10 μm. In the end, we propose an image deblurring algorithm that uses deconvolution to eliminate the blurring caused by the nonzero spatial extent of the source and multiple Coulomb scattering. This work studies the comprehensive factors of laser accelerated proton radiography with resolution calibration targets and presents incremental additions to previous work on proton radiography.

The p +9Be elastic scattering below 30MeV: Optical model analysis and data normalization

Differential cross-section data of elastic scattering for [Formula: see text]Be below a proton incident energy of 30[Formula: see text]MeV are evaluated by using two techniques. First, optical model analysis is performed and applied to the analyzing powers and reaction cross-sections to extract the optical potential parameters. Then, angular distributions of the differential cross-section are calculated with this potential and compared with the experimental data and normalization coefficients are extracted. Second, a consistent comparison between data sets with similar energies is considered in a minimization process to obtain another set of data normalization coefficients. The two techniques lead to similar normalized values for the existing data and consistently validate a body of low-energy data that can be safely used for further theoretical studies. Furthermore, the systematic behavior and energy dependence of the volume integral are determined as well as the energy dependence of the reaction cross-sections is predicted.

Production Cross Sections and Induced Activity in Ge Isotopes by 30 MeV Proton Beam

The excitation functions of 70 Ge(p,n) 70 As, 72 Ge(p,n) 72 As, 74 Ge(p,n) 74 As and 76 Ge(p,n) 76 As reactions were studied from reaction threshold to 30 MeV by using EMPIRE-3.2 and TALYS-1.9 nuclear reaction model codes. This study is important because some isotopes produced are important for positron emission tomography (PET). Direct, pre-compound and compound nuclear reactions are considered as main nuclear reaction mechanisms in the codes. The calculated excitation functions have been compared with available experimental data and found to be in fair agreement. Furthermore, the contributions of various reaction mechanisms have been studied in total reaction cross-section that varies with the incident proton energy. The estimation of induced radio activity in thick Ge target due to the primary interaction is carried out for1μA, 30 MeV proton beam.

Calculated cyclotron-based scandium-47 production yields via 48Ca(p, 2n)47Sc nuclear reaction

Scandium-47 is a promising particle emitter that has been suggested as a candidate for radiotheranostics. Thus, better understanding of optimum irradiation parameters, radioactivity yields and possible impurities during its production is of paramount importance. The theoretical calculation of the end-of-bombardment (EOB) results is performed using Microsoft Excel following the calculation of the excitation function obtained from the TALYS software and the stopping power obtained from the SRIM software can be accessed for free. According to the TALYS code calculations, the threshold energy for 47Sc production was 8.39 MeV, whereas the maximum cross-section (879 mbarn) occurred at proton incident energy of 17 MeV. The calculated EOB yield for 48Ca(p,2n)47Sc nuclear reaction at 60 MeV proton energy was found to be 449 MBq/μAh, which was suitable quality for typical radionuclide production. Besides, three radionuclides, i.e. 48Sc, 46Sc and 47Ca were predicted to be the main impurities in the 47Sc production. However, in order to minimize the production of 48Sc, 46Sc and 47Ca impurities radionuclide the safest and optimum proton energy should be between 23 and 30 MeV, which can be achieved using the available 26 MeV cyclotron. This study can be used as a reference for future 47Sc production when proton beams of up to 60 MeV are employed.

Electron transfer in proton‐hydrogen collisions in dense semi‐classical hydrogen plasma

AbstractQuantum mechanical calculations have been accomplished to study the dynamics of the reaction: p + H(1s) → H(nlm) + p in dense semi‐classical hydrogen plasma. Interactions among the charged particles in plasma are represented by a pseudopotential which takes care of the collective effects at large distances and quantum effect of diffraction at small distances. Various capture cross sections are computed for the incident proton energy lying within 10 to 500 keV by applying a distorted wave method which uses a variationally determined closed‐form wave function of hydrogen atom. Moreover, an inclusive study is made to explore the effects of screening of plasma and quantum diffraction on various capture cross sections for a wide range of thermal Debye length and de Broglie wave length. It has been found that various cross sections suffer considerable changes due to varying Debye length and de Broglie wave length.

New measurements of cross sections and S-factors for $$d(p,\gamma )^{3}\text{He}$$ reaction at BBN energies

This communication is a summary of our measurements of cross sections and astrophysical S-factors for radiative proton capture on deuteron. The measurements are a part of a new program to study light-ion induced nuclear capture and inelastic scattering reactions relevant to nucleosynthesis and astrophysics. We are primarily interested in the capture reactions relevant to primordial or Big Bang Nucleosynthesis (BBN). Section 1 provides a brief and general overview of nuclear astrophysics and the primary experimental challenges in the measurements of cross sections and S-factors for reactions relevant to nuclear astrophysics. The next section discusses the significance of the $$d(p,\gamma )^{3}\text{He}$$ reaction in context of BBN and the need for generating a more precise data in the relevant energy window. The subsequent section is devoted to the experiment and results of measurements of cross sections and astrophysical S-factors for the $$d(p,\gamma )^{3}\text{He}$$ reaction at three new BBN energies. One salient features of the measurements is the use of large volume LaBr $$_{3}$$ :Ce scintillation detector for measurement of the capture $$\gamma $$ -rays. To the best of our knowledge, capture $$\gamma $$ -rays for this reaction had so far been measured with NaI(Tl) or HPGe detectors only. The detection efficiency of the detector has been measured experimentally for different monochromatic $$\gamma $$ -ray energies. In addition, realistic GEANT4 Monte Carlo simulations have been carried out to generate the response of the detector for $$\gamma $$ -ray energies of interest. The measured cross section and astrophysical S(E)-factor for the three incident proton energies are found to be in agreement with the overall trend of the global data set for the BBN region, reported in the literature. The measured S-factors are also found to be in agreement with recent microscopic calculations of Marcucci et al. (2016).

Double differential cross sections of neutron production by 135 and 180 MeV protons on A-150 tissue-equivalent plastic

The double differential cross sections (DDXs) of neutron production by 135 and 180 MeV protons were measured to obtain benchmark data for calculating neutron doses in proton therapy. The incident proton energies correspond to those of protons decelerating in a patient. An A-150 tissue-equivalent plastic was used as the target. The measured DDXs were compared with those calculated using PHITS, FLUKA, and Geant4. The calculated DDXs were found to be underestimated compared with the measured ones, especially at forward angles. In proton therapy, exposure evaluations using one of these simulation codes would underestimate the neutron dose.

Off-Axis Characterisation of the CERN T10 Beam for low Momentum Proton Measurements with a High Pressure Gas Time Projection Chamber

We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.

Evaluation of the activation of brass apertures in proton therapy using gamma-ray spectrometry and Monte Carlo simulations

Collimating apertures are used in proton therapy to laterally conform treatment fields to the target volume. While this is a standard technique in passive spreading treatment heads, patient-specific apertures can supplement pencil-beam scanning (PBS) techniques to sharpen the lateral dose fall-off. A radiation protection issue is that proton-induced nuclear reactions can lead to the formation of radionuclides in the apertures. In the experiments of the current study, cylindrical, thick brass targets were irradiated with quasi-monoenergetic proton fields of 100.0 MeV and of 226.7 MeV in PBS mode. The radioactivation of these two brass samples was characterised with a low-level gamma-ray spectrometer. The activation products were scored in a Monte Carlo simulation, too, and compared with the experimental activities. For the high-energy field, 63Zn, 60Cu, and 61Cu were the most important short-lived isotopes regarding the measured specific activity. After irradiation with the 100.0 MeV field, 62Cu, 63Zn, and 60Cu had the highest activity. Regarding long-lived isotopes, which determine the storage time of the used apertures, the isotopes 57Co, 65Zn, 54Mn, 56Co had the largest contribution to the activity. The relative difference of activities between simulation and experiment was typically between 10%–20% for short-lived nuclides and were up to a factor of five larger for long-lived nuclides. Summarising experiments and simulations for both incident proton energies, 62Cu was the most important detected residual nucleus regardless if specific activity or equivalent dose is considered.