Proton Energy Research Articles

The Effect of the Laser Light Polarization on the Generation of Proton Ignitor Beam

In this study, the effect of laser light polarization (linear polarization (LP) and circular polarization (CP)) on the shape of the proton energy spectrum and its energy cut-off is explored. The obtained results from 1D3V PIC simulation showed that two different acceleration mechanisms including target normal sheath acceleration (TNSA) and radiation pressure acceleration (RPA) are dominant. It is found that for the amplitude of a = 27 and pulse duration 333 fs when the laser polarization is changed from LP to CP, the electron heating is reduced which caused the generation of the multi-peak quasi-monoenergetic proton beam. Then by applying the 1D3T hydrodynamic code, the potential of the aforementioned proton beam with a high peak energy 510 MeV to irradiation on pre-compressed DT capsule was examined. Finally, the proton ignition energy threshold at a distance of 0.78 cm between the proton source and pre-compressed DT fuel capsule was investigated. (The threshold proton ignition energy is 15.52 kJ)

Fabrication of custom oral positioning devices in head and neck proton radiotherapy.

With complex head and neck diseases that closely approximate crucial organs or have advanced spread and cannot be surgically resected, intensity modulated proton beam radiotherapy (IMPT) is favored due to its superior dose targeting through magnetic manipulation of the proton energy. A radiation mask and an oral positioning device (OPD) immobilize craniofacial, cervical, and oral structures for accurate and reliable radiation delivery. Widely available pe-fabricated thermoplastic OPDs are manufactured in standardized forms and materials that unpredictably affect the proton beams' pathways and range. This technique article showcases a workflow that combines of analog and digital dental techniques to produce a customized 3-D printed OPD within 2 appointments. This article is protected by copyright. All rights reserved.

Non-destructive measurement of the beryllium thickness of the iBNCT neutron-generation target using negative muons

Accelerator-based boron neutron capture therapy (BNCT) has recently been studied by several researchers. In BNCT, a neutron-generation target is an important component because an intense neutron flux of more than 109n/cm2/s is required to complete medical treatments within an acceptable treatment time. In the Ibaraki BNCT (iBNCT) project, a proton linear accelerator (linac) consisting of a 3-MeV radio-frequency quadrupole and an 8-MeV drift-tube linac based on J-PARC linac techniques was used. As for the neutron-generation target, beryllium was adopted with an incident proton energy of 8 MeV. The target has a three-layer structure fabricated using hot-isostatic pressing (HIP). The first layer consists of 0.5 mm-thick beryllium, which is slightly shorter than the 8-MeV proton range in beryllium for neutron generation. The second is a 0.5 mm-thick palladium, which was selected owing to its durability against blistering, and the third is a 10 mm-thick copper for heat removal purposes with cooling water circulation. The thickness of the beryllium is very important because a shortage of thickness reduces the yield of neutrons, while an excess of thickness results in damage by stopped protons owing to a blistering effect. Despite its importance, this thickness has not yet been confirmed because it is not realistic to measure it destructively in terms of the construction cost of the iBNCT target; thus, a non-destructive measurement is desirable. This paper describes a method for measuring the thickness of the beryllium layer of a mockup of an iBNCT neutron target, which was constructed in the same way as the actual iBNCT, in a non-destructive manner using negative muon X-rays. The experiment was performed in the J-PARC MLF muon facility, and the obtained thickness was 0.48 ± 0.02 mm, which corresponds to the designed value of 0.50 ± 0.05 mm.

Differential cross section measurements of the 7Li (p,p΄γ1-0) 7Li reaction suitable for PIGE applications

Differential cross sections of the reaction 7Li(p,p΄γ1-0)7Li were experimentally determined in the proton energy range between 1000 and 4000 keV. The experiment was conducted at the Tandem Accelerator Laboratory of N.C.S.R. “Demokritos”. The detection of the emitted gamma rays, having an energy Eγ = 477.6 keV, was accomplished using four HPGe detectors of relative efficiency varying between 18 and 80%, at the detection angles of 0°, 55°, 90° and 165°. The statistical errors of the measurements did not exceed 4%, while the overall systematic uncertainty budget was also kept as low as possible (∼8%). For the validation of the obtained cross sections a benchmarking experiment was performed using a thick target of known stoichiometry. The comparison with existing experimental datasets in literature is also presented and discussed.

Investigating changes in the diffuse reflectance spectra of BaSO4 powders modified with SiO2 nanoparticles exposed to proton irradiation

The authors modified BaSO4 powders with SiO2 nanoparticles and studied the effect of this modification on powders’ structure and optical properties, as well as on the changes of the latter after 5 keV proton irradiation. No significant post-modification changes in structure have been observed. In the IR-spectrum, the authors have recorded the band intensity changes for SiO2, Si – O – Si, and Si–Si vibrations, as well as emerging OH group vibration band. Additionally, the authors have noted the appearance of an absorption band in the UV/vis spectra caused by intrinsic point defects in BaSO4 anionic sublattice. The energy losses induced by displacement and ionization were calculated, as were the proton free paths in the modified powder. It is shown that an increase of radiation stability is provided by solely 1.2% of the proton energy flux absorbed in the nSiO2 nanolayer contributing to the total energy loss in the entire modified powder. Two mechanisms are proposed for the processes occurring in the nSiO2/mBaSO4 system that determine the increase of its radiation stability compared with the non-modified powder.

Development of a log file analysis tool for proton patient QA, system performance tracking, and delivered dose reconstruction.

To describe a log file-based patient-specific quality assurance (QA) method and develop an in-house tool for system performance tracking and dose reconstruction in pencil-beam scanning proton therapy that can be used for pre-treatment plan review. The software extracts beam-specific information from the treatment delivery log file and automatically compares the monitor units (MU), lateral position, and size of each spot against the intended values in the treatment plan to identify any discrepancies in the beam delivery. The software has been used to analyze 992 patients, 2004 plans, 4865 fields, and more than 32 million proton spots from 2016 to 2021. The composite doses of 10 craniospinal irradiation (CSI) plans were reconstructed based on the delivered spots and compared with the original plans as an offline plan review method. Over the course of 6 years, the proton delivery system has proved stable in delivering patient QA fields with proton energies of 69.4-221.3 MeV and an MU range of 0.003-1.473 MU per spot. The planned mean and standard deviation (SD) of the energy and spot MU were 114.4 ± 26.4 MeV and 0.010 ± 0.009 MU, respectively. The mean and SD of the differences in MU and position between the delivered and planned spots were 9.56 × 10-8 ± 2.0 × 10-4 MU and 0.029/-0.007 ± 0.049/0.044 mm on the X/Y-axis for random differences and 0.005/0.125 ± 0.189/0.175 mm on the X/Y-axis for systematic differences. The mean and SD of the difference between the commissioning and delivered spot sizes were 0.086/0.089 ± 0.131/0.166 mm on the X/Y-axis. A tool has been developed to extract crucial information about the performance of the proton delivery and monitor system and provide a dose reconstruction based on delivered spots for quality improvement. Each patient's plan was verified before treatment to ensure accurate and safe delivery within the delivery tolerance of the machine.

Cross sections for natZr(n,xn)88Zr and natZr(n,xn)89Zr reactions at neutron energies from 29.4 to 42 MeV

Cross sections of natZr(n,xn)88Zr and natZr(n,xn)89Zr were measured at six neutron energies in the energy range of 29.4–42 MeV by irradiating natural zirconium (natZr) samples. The neutrons were produced via 9Be(p,n)9B reaction induced by bombarding a 0.25 mm thick beryllium target with 35, 40, and 45 MeV protons. The neutron spectrum produced at each proton energy was simulated by using the PHITS code. Two neutron peaks were observed in the simulated spectra for each proton energy. By using the estimated activity ratio factor for each neutron peak and experimentally measured γ-ray activities of 89Zr and 88Zr, the cross sections of natZr(n,xn)89Zr and natZr(n,xn)88Zr reactions were obtained, respectively. These experimentally measured cross sections were compared with the cross sections estimated by the TALYS-1.95 calculations and those from the EAF library. For natural zirconium, these cross sections are reported here for the first time in the neutron energy range of 29.4–42 MeV.

Systematic study of (p, n) and (p, 2n) reactions on 110Cd

Standard activation analysis technique with γ ray spectroscopy via off-line mode was utilized for reaction cross section estimation. The proton beam was transported from the BARC-TIFR accelerator and targeted on the natCd target. The 16 MeV proton beam irradiated the sample, and Copper foil was utilized as an energy degrader. The activation cross sections were estimated for 110Cd(p, n) reaction for the ground state (Jπ = 7+) population of 110In nucleus and 110Cd(p, 2n)109In reaction at 14.14 MeV of proton energy. Along with experimental measurements, the theoretical study has been carried out for ground and metastable states population by utilizing the nuclear model code TALYS-1.95, EMPIRE-3.2.3, and ALICE-2014 for both reaction channels. The estimated cross sections are valuable for the improvement of theoretical nuclear model codes for a comprehensive knowledge of nuclear reaction mechanisms. The produced isotopes 109,110In have significant importance in Positron Emission Tomography (PET) studies. The present study is a dive into the phenomenological and microscopic level density models of different nuclear model codes in predicting excitation functions.

Fusion-fission hybrid reactor facility: power profiling

The current state of research in the field of nuclear and thermonuclear power aimed at creating power generation plants makes it possible to predict the further development of modern power industry in the direction hybrid reactor power plants. Such hybrid systems include a tokamak with reactor technologies, worked out in detail in Russia, and systems with an additional source of neutrons. Power generation plants using tokamaks and accelerators with the required level of proton energy will be of exceptionally large size and power, which will postpone their construction on an industrial scale to the distant future. The ongoing research is aimed at the development of small generation and has the prospect of entering the field of energy use in a shorter period. The hybrid reactor facility under study consists of an axisymmetric assembly of fuel blocks of a high-temperature gas-cooled reactor and a linear plasma source of additional neutrons. The paper demonstrates the results of optimization plasma-physical, thermophysical and gas-dynamic studies, the purpose of which is to level the distortions of the power density field, which are formed in the volume of the multiplicating part of the facility due to the pulsed operation of the plasma source of D-T-neutrons. The studies on increasing the “brightness” of the source and modeling its operating modes were carried out using the DOL and PRIZMA programs. The thermophysical optimization and gas-dynamic calculations were performed using the verified SERPENT and FloEFD software codes. The calculations were made on a high-performance cluster of the Tomsk Polytechnic University.

Mechanistic insight into electron orientation by tailoring Ni–Cu atom-pairs for high-performance CO2 electroreduction

The electrochemical CO2 reduction reaction (CO2RR) is a promising solution for addressing global issues related to carbon neutrality and energy shortage. However, it is hindered by the high thermal stability of CO2 and competitive hydrogen evolution reaction, which lead to low efficiency and selectivity. Herein, a Ni–Cu atom-pair catalyst with well-defined electron orientation has been tailored for electrocatalytic CO2RR. In particular, the tailored Ni/Cu0.38–covalent triazine framework catalyst exhibited extremely high catalytic activity with high faradaic efficiency (99.82% at −1.1 V vs. reversible hydrogen electrode, RHE) and turnover frequency (5116 h−1 at −1.1 V vs. RHE). To the best of our knowledge, this is a diatomic catalyst with the lowest reported metal concentration and excellent efficiency and selectivity. Density functional theory calculations and experimental results further revealed that the adsorption of CO2 was enhanced, while the electron orientation from the Cu site to Ni site reduced the antibonding orbital coupling between Ni and C atoms in CO2, thereby breaking the protonation energy barrier and providing high catalytic efficiency. Moreover, the enrichment of electrons from the electrolyte as well as the accumulation of *H at Cu sites was essential for improving CO selectivity.

Influence of Particle Beam and Accelerator Type on ADS Efficiency

Conditions that maximize the performance of an accelerator-driven system related to particle beam and energy and accelerator type are analyzed. The toolkit Geant4 simulated the interaction of protons and ions with masses up to 20Ne and energies from 0.2 to 2 GeV/n. The beam intensity considered is 1.5 × 1016 p/s. The core of the reactor is modeled as an assembly of fuel rods surrounding a cylindrical beryllium converter, with a criticality coefficient of 0.985 and lead-bismuth eutectic coolant. Lower enrichment generates better utilization of fuel (20% to 25% from the initial actinide mass can fission in a cycle keeping neutron damage in clad below 200 displacements per atom). Data on particle fluence and energy released obtained from the simulation are used to calculate total electric power produced and isotope evolution. Power spent to accelerate the beam depends on accelerator type and is calculated by scaling from data on accelerator efficiency for a reference particle. Optimal proton energy is ~1.5 GeV when the beam is accelerated in a linac with energy gain G ~ 14 and is 0.75 to 1 GeV in the case of a cyclotron (G ~ 12). Ion beams starting with 4He realize higher G values than protons: 20 to 50 in a linac and 15 to 35 in a cyclotron.

A multi-source based Monte Carlo simulation model for spot scanning proton radiotherapy using GEANT4

Proton therapy is widely used for treating various tumor types due to its favorable dosimetric characteristics compared with conventional radiotherapy. However, a small error in dose calculation may lead to a substantial misadministration of planned radiation dose. This work aims to create a simplified and easy-to-use Monte Carlo (MC) simulation model, based on the multi-source model principle, for spot scanning proton radiotherapy. Our multi-source model contains a set of physical parameters acquired from a Varian ProBeam compact system at the South Florida Proton Therapy Institute (SFPTI). The source model input parameters are mean energy (σΕ) and beam spot (σs) standard deviations, which directly affect the integrated depth-dose (IDD) dosimetric characteristics such as beam width, proton range, and distal fall-off. Despite the simplicity of the presented model, all simulated results matched the corresponding experimental values within 2.5% and were found to be within the acceptable clinical limits, for a wide nominal proton energy range (i.e., 90–220 MeV). Additionally, the comparison of the simulated IDDs with the experimental IDDs was found to be highly conformal with 100% of the points passing the 2%/2 mm gamma index test. The model presented in this work can be efficiently used to model high energy (>80 MeV) in a central axis clinical scanning proton beam in a real clinical setting. The small number of input parameters selected allows for a more efficient and user-friendly MC modeling than previously developed models, while off-axis beam characteristics can be studied with the addition of a new sub-source parameter file.

Mono-Energetic Proton Induced Damages in SiC Power MOSFETs

The mechanisms of single event burnout (SEB) are investigated for SiC MOSFETs by proton irradiation with varying energies. The material melting due to thermal runaway is observed at the damage region for the device with SEB. The proton energy is proved to be a key factor to affect SEB. The proton induced SEB cross-section is higher for higher energy proton irradiation. The information of the secondary ions is obtained through Monte Carlo simulations to explain this phenomenon. The occurrence of SEB depends on the LET value and range of the secondary ions. The relations between SEB and quasi-stationary avalanche characteristics for SiC MOSFET are verified by TCAD simulations. SEB phenomenon actually origins from the secondary breakdown caused by charged ion injection. So the drain bias voltage during irradiation is very important to determine whether SEB occurs.

High Energy Solar Particle Events and Their Relationship to Associated Flare, CME and GLE Parameters

AbstractLarge solar eruptive events, including solar flares and coronal mass ejections (CMEs), can lead to solar energetic particle (SEP) events. During these events, protons are accelerated up to several GeV and pose numerous space weather risks. These risks include, but are not limited to, radiation hazards to astronauts and disruption to satellites and electronics. The highest energy SEPs are capable of reaching Earth on timescales of minutes and can be detected in ground level enhancements (GLEs). Understanding and analyzing these events is critical to future forecasting models. However, the availability of high energy SEP data sets is limited, especially that which covers multiple solar cycles. The majority of analysis of SEP events considers data at energies <100 MeV. In this work, we use a newly calibrated data set using data from Geostationary Operational Environmental Satellite‐high energy proton and alpha detector between 1984 and 2017. Analysis of the SEP events in this time period over three high energy channels is performed, and SEP properties are compared to flare and CME parameters. In addition, neutron monitor (NM) observations are examined for the relevant GLE events. We find that correlations between SEP peak intensity and the CME speed are much weaker than for lower SEP energies. Correlations with flare intensity are broadly similar or weaker. Strong correlations are seen between >300 MeV data and GLE properties from NM data. The results of our work can be utilized in future forecasting models for both high energy SEP and GLE events.

A high-intensity superconducting H+ 3 cyclotron for isotope production

We're concerned with future accelerators of high intensity protons for isotope production. To this end, we initiate a proposal to design an innovative superconducting H+ 3 cyclotron TR150, aiming at proton energy of 70–150 MeV and proton current of ∼ 1.0 mA. Cyclotrons in this energy range are not developed world-wide; moreover numerous highly interesting and increasingly demanded radio­nuclides are in this energy range. Our machine shall be designed to accelerate H+ 3 ion, the simplest and stable triatomic molecular ion, by injection from an external ion source and extraction by stripping. This has potential to extract proton beam of variable energies with very high extraction efficiency, and thus enables to simultaneously provide multiple proton beams for multiple external production targets. A baseline design of our machine and the beam dynamics studies are presented in this paper.

Optically Stimulated Luminescent Response of the LiMgPO4 Silicone Foils to Protons and Its Dependence on Proton Energy.

Modern radiotherapy (RT) techniques, such as proton therapy, require more and more sophisticated dosimetry methods and materials. One of the newly developed technologies is based on flexible sheets made of a polymer, with the embedded optically stimulated luminescence (OSL) material in the form of powder (LiMgPO4, LMP) and a self-developed optical imaging setup. The detector properties were evaluated to study its potential application in the proton treatment plan verification for eyeball cancer. The data showed a well-known effect of lower luminescent efficiency of the LMP material response to proton energy. The efficiency parameter depends on a given material and radiation quality parameters. Therefore, the detailed knowledge of material efficiency is crucial in establishing a calibration method for detectors exposed to mixed radiation fields. Thus, in the present study, the prototype of the LMP-based silicone foil material was tested with monoenergetic uniform proton beams of various initial kinetic energies constituting the so-called spread-out Bragg peak (SOBP). The irradiation geometry was also modelled using the Monte Carlo particle transport codes. Several beam quality parameters, including dose and the kinetic energy spectrum, were scored. Finally, the obtained results were used to correct the relative luminescence efficiency response of the LMP foils for monoenergetic and spread-out proton beams.

Particle‐induced degradation of III–V multi‐junction solar cells under different configurations of displacement damage dose

AbstractThe solar arrays of spacecrafts are subjected to a severe radiative environment. Associated degradation rates are dependent on operational orbit configuration. The current approach used in models and tools to determine power degradation shall thus be validated to ensure good prediction accuracy. This paper reports on extensive irradiation test campaigns realized on triple‐junction solar cells to compare degradation induced by different configurations of irradiation reproducing nominally the same displacement damage dose (DDD) in the active layer. These test campaigns data are used to support the validation of a new tool developed to optimize prediction accuracy of solar cell degradation. The DDD equivalence between front/rear irradiation on solar cell assemblies and on bare solar cells, between different electron and proton energies, as well as the verification of the superposition principle are addressed. Results are conclusive regarding the equivalence of degradation obtained with electrons, protons and/or combined electrons and protons, accounting for local shielding.

Mechanisms of the Device Property Alteration Generated by the Proton Irradiation in GaN-Based MIS-HEMTs Using Extremely Thin Gate Insulator

Recently, we reported that device performance degradation mechanisms, which are generated by the γ-ray irradiation in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs), use extremely thin gate insulators. When the γ-ray was radiated, the total ionizing dose (TID) effects were generated and the device performance deteriorated. In this work, we investigated the device property alteration and its mechanisms, which were caused by the proton irradiation in GaN-based MIS-HEMTs for the 5 nm-thick Si3N4 and HfO2 gate insulator. The device property, such as threshold voltage, drain current, and transconductance varied by the proton irradiation. When the 5 nm-thick HfO2 layer was employed for the gate insulator, the threshold voltage shift was larger than that of the 5 nm-thick Si3N4 gate insulator, despite the HfO2 gate insulator exhibiting better radiation resistance compared to the Si3N4 gate insulator. On the other hand, the drain current and transconductance degradation were less for the 5 nm-thick HfO2 gate insulator. Unlike the γ-ray irradiation, our systematic research included pulse-mode stress measurements and carrier mobility extraction and revealed that the TID and displacement damage (DD) effects were simultaneously generated by the proton irradiation in GaN-based MIS-HEMTs. The degree of the device property alteration was determined by the competition or superposition of the TID and DD effects for the threshold voltage shift and drain current and transconductance deterioration, respectively. The device property alteration was diminished due to the reduction of the linear energy transfer with increasing irradiated proton energy. We also studied the frequency performance degradation that corresponded to the irradiated proton energy in GaN-based MIS-HEMTs using an extremely thin gate insulator.

Preparation of [68Ga]Ga-Chloride from 68Zn solid target for the synthesis of pharmaceutical grade [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTA-TATE

68Ga is produced from enriched zinc-68 target electrodeposited on copper base material which was irradiated with 15 MeV proton energy in 30 MeV cyclotron. A modified semi-automated separation and purification module was used to obtain pharmaceutical grade [68Ga]GaCl3 in 35 ± 5 min. The quality of [68Ga]GaCl3 produced was in accordance with Pharmeuropa 30.4. The [68Ga]GaCl3 was utilized for the formulation of multiple doses of [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTATATE. The quality of [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTATATE were also in accordance with Pharmacopeia.

Experimental setup for Weak Interaction Studies with Radioactive ion-beams WISArD

The article describes the commissioning and technical development of the Weak Interaction Studies with 32Ar Decay (WISArD) experiment, installed at the radioactive ion-beam facility ISOLDE/CERN. The experiment aims to extend the present limits on scalar and tensor currents in the weak interaction and hence search for physics beyond the Standard Model. The evaluation of these limits relies on measuring the proton energy in beta-delayed proton emission, sensitive to both the beta-neutrino angular correlation coefficient aβν and the Fierz interference term b. The method tries to improve previous studies by considering the positron-proton coincidences when determining the kinematic shift in the energy of the emitted protons. Using this coincidence technique, the aβν and b coefficients will be measured at the per mil level. Simulations were employed to optimize the ion beam transport efficiency and validate proof-of-principle results obtained in November 2018 (Nov2018). Upgrades are ongoing, and we are looking into improvements to the overall performance of the setup.