MeV Proton Beam Research Articles

Contributions of MYRRHA to the European Fusion Energy Roadmap

One of the main objectives of the EUROfusion Roadmap to Fusion Energy during Horizon Europe is to finalize the conceptual design (thus preparing the engineering design phase) and initiate the construction of a fusion spectrum neutron source (IFMIF-DONES). The Belgian Nuclear Research Center is currently developing the MYRRHA research facilities, which include a subcritical accelerator-driven system ignited by a 600 MeV superconducting linear proton accelerator coupled to a 100 MeV proton injector. The implementation of the multipurpose fast spectrum reactor MYRRHA will proceed in phases, with phase I, covering 2019–2027, including the deployment of the 100 MeV proton accelerator and associated fusion material research facilities. The research on fusion materials on the basis of the 100 MeV proton beam and with hot cell facilities will focus on innovative materials and composites and will be fully complementary to IFMIF-DONES as well to the planned research program on using currently available nuclearized facilities such as BR2 (Belgian Research Reactor 2) and Hot Cells for mechanical, microstructural and chemical analysis. A bespoke fusion irradiation module is also foreseen on the MYRRHA reactor, the construction of which is planned in the third phase of the implementation of the project (i.e. after 2035). Provisions have been made in the core of the MYRRHA reactor to include so-called In-Pile Sections around the central core or at the central core position below the spallation target when operating in subcritical mode. In this contribution, we review the role and technical capabilities that MYRRHA facilities may provide in the framework of the European Fusion Electricity Roadmap and specifically for DEMO Engineering Design, Material's Development and enhancement of Technology Readiness Level. Aspects of education and training, being an integral part of the European nuclear fusion program, are also touched upon. Finally, the synchronization of the timelines for the implementation of MYRRHA and the EU fusion facilities are discussed.

Proton-induced radiation damage in Cs2LiYCl6:Ce scintillator

Cs2LiYCl6:Ce crystal scintillator (CLYC:Ce) has garnered significant attention for its applications in both neutron detection and gamma-ray spectroscopy. This is due to its excellent pulse shape discrimination (PSD) capabilities, which allow for distinguishing between neutrons and gamma rays. Recently, there has been interest in utilizing CLYC:Ce in high-dose environments, making it crucial to understand the effects of radiation damage on its performance. In this work, we aim to examine the impact of radiation damage on the scintillation performance of CLYC:Ce under 100 MeV proton beam. To minimize systematic uncertainty, the change in light output of CLYC:Ce was measured at different accumulated doses using the same experimental setup. The pulse shape discrimination for thermal neutrons was assessed before and after irradiation. Additionally, the decay time of gamma-ray and thermal neutron-induced pulses was analyzed at various accumulated doses. The results of these analyses provide support for little degradation of pulse shape discrimination even with the high proton dose. Furthermore, the study considered and discussed the scintillation recovery of CLYC:Ce over a month. Despite the substantial damage induced by high-energy protons, the results demonstrate that CLYC:Ce remains a promising scintillator for thermal neutron detection.

Neutron radiation induced effects in 4H-SiC PiN diodes

Silicon carbide (SiC) is a wide band gap semiconductor and an attractive candidate for applications in harsh environments such as space, fusion, or future high luminosity colliders. Due to the large band gap, the leakage currents in SiC devices are extremely small, even after irradiation to very high fluences, enabling operation without cooling and at high temperatures. This study investigates the effect of neutron irradiation on 50 μm p-n 4H-SiC diodes using current-voltage, capacitance-voltage, and charge collection efficiency (CCE) measurements up to neutron fluences of 1 × 1016 n eq/cm2. The leakage currents of the investigated devices remained extremely small, below 10 pA at 1.1 kV reverse bias. In the forward bias, a remarkable drop of the current was observed, which was attributed to an increased epi resistivity due to compensation of the epi layer doping by deep-level defects. The CCE was evaluated for alpha particles from a radioactive source, a 62.4 MeV proton beam at the MedAustron ion therapy center and using UV-TCT. The charge collection efficiency in reverse bias was shown to scale directly with the 1 MeV equivalent fluence Φeq as CCE∝Φeq -0.63±0.01. A CCE better than 50% was able to be obtained for fluences up to 1 × 1015 n eq/cm2. Because of the low currents in the forward direction, particle detection was also possible in forward bias, where the CCE was found to be increased relative to reverse bias. Furthermore, a significant dependency on the amount of injected charge was observed, with the CCE surpassing 100% in alpha and UV-TCT measurements, requiring further systematic investigation.

Investigation of the dose rate and linear-energy-transfer of the signal quenching of radiochromic silicone-based dosimeters for different curing times and compositions

The response of radiochromic dosimeters based on silicone is influenced by the dose-rate quenching and also the linear energy transfer (LET). However, the impact of curing time and composition on quenching has not been fully characterized. We investigated two dosimeter compositions, with 5% and 9% curing agent, which cured for 1, 3 or 5 days and that subsequently were irradiated with an 80 MeV proton beam with three different beam currents. Monte Carlo simulations were utilised for the estimation of dose, dose rate and LET profiles. We found a significant decrease in LET-dependent quenching with curing time, but no significant decrease in dose-rate-dependent quenching.

Proton dosimetry in a magnetic field: Measurement and calculation of magnetic field correction factors for a plane-parallel ionization chamber.

The combination of magnetic resonance imaging and proton therapy offers the potential to improve cancer treatment. The magnetic field (MF)-dependent change in the dosage of ionization chambers in magnetic resonance imaging-integrated proton therapy (MRiPT) is considered by the correction factor , which needs to be determined experimentally or computed via Monte Carlo (MC)simulations. In this study, was both measured and simulated with high accuracy for a plane-parallel ionization chamber at different clinical relevant proton energies and MFstrengths. The dose-response of the Advanced Markus chamber (TM34045, PTW, Freiburg, Germany) irradiated with homogeneous 10 10 cm quasi mono-energetic fields, using 103.3, 128.4, 153.1, 223.1, and 252.7 MeV proton beams was measured in a water phantom placed in the MF of an electromagnet with MF strengths of 0.32, 0.5, and 1 T. The detector was positioned at a depth of 2 g/cm in water, with chamber electrodes parallel to the MF lines and perpendicular to the proton beam incidence direction. The measurements were compared with TOPAS MC simulations utilizing COMSOL-calculated 0.32, 0.5, and 1 T MF maps of the electromagnet. was calculated for the measurements for all energies and MF strengths based on the equation: , where and were the temperature and air-pressure corrected detector readings with and without the MF, respectively. MC-based correction factors were determined as , where and were the doses deposited in the air cavity of the ionization chamber model with and without the MF, respectively. Furthermore, MF effects on the chamber dosimetry are studied using MC simulations, examining the impact on the absorbed dose-to-water ( ) and the shift in depth of the Braggpeak. The detector showed a reduced dose-response for all measured energies and MF strengths, resulting in experimentally determined values larger than unity. For all energies and MF strengths examined, ranged between 1.0065 and 1.0205. The dependence on the energy and the MF strength was found to be non-linear with a maximum at 1 T and 252.7 MeV. The MC simulated values agreed with the experimentally determined correction factors within their standard deviations with a maximum difference of 0.6%. The MC calculated impact on was smaller 0.2 %. For the first time, measurements and simulations were compared for proton dosimetry within MFs using an Advanced Markus chamber. Good agreement of was found between experimentally determined and MC calculated values. The performed benchmarking of the MC code allows for calculating for various ionization chamber models, MF strengths and proton energies to generate the data needed for a proton dosimetry protocol within MFs and is, therefore, a step towardsMRiPT.

Nanocomposite physics and structure considerations in MCNP proton shielding models

Background Deep space crewed missions require unique radiation shielding considerations. Due to mission duration and the heavy, high-energy nature of deep space radiation, the aluminum alloys that have historically been used for spacecrafts do not provide sufficient protection for crew members. Polymer-based nanocomposites have been proposed as potential radiation shielding materials for deep space applications; however, the high tunability of nanocomposites and the limited number of facilities able to produce representative radiation energies presents barriers to nanocomposite testing. Computational approaches may allow for preliminary investigation and discrimination of nanocomposite parameters like polymer and filler composition, loading percentage, and filler size and structure. Methods This work aims to investigate several modeling methods to perform radiation transport simulations for a nanocomposite, particularly with regards to modeling the filler nanostructure and the involved physics. Published experiments of a polydimethylsiloxane-carbon nanotube nanocomposite in 63 MeV and 105 MeV proton beams were digitally recreated in MCNP6.2 with three different nanocomposite structures. Additionally, several simulations were performed under various physics assumptions. The computationally determined water equivalent thicknesses are compared between modeling methods, as well as between the computational and the published experimental work. Results Nanostructure model complexity had no impact on the computed water equivalent thickness, with <1% difference between the three modeling methods. The inclusion of delta ray production and tracking physics produced a slight decrease in the computed water equivalent thickness and significantly increased the computational time for a single simulation by a factor of 35.7. Computationally determined water equivalent thicknesses are within 5% of published experimentally determined values. Conclusions Shielding capabilities of a polymer/carbon nanotube nanocomposite estimated using Monte Carlo radiation transport models agree well with published experimental results, even with a simplistic representation of the nanocomposite material. Radiation transport settings influenced the resulting water equivalent thickness as well as computational resource needs.

First microdosimetric measurements with a tissue-equivalent proportional counter at the MedAustron ion-beam therapy facility.

The aim of this work is to present the first microdosimetric spectra measured with a miniaturised tissue-equivalent proportional counter in the clinical environment of the MedAustron ion-beam therapy facility. These spectra were gathered with a 62.4-MeV proton beam and have been compared with microdosimetric spectra measured in the 62-MeV clinical proton beam of the CATANA beam line. Monte Carlo simulations were performed using the Geant4 toolkit GATE and a fully commissioned clinical beam line model. Finally, similarities and discrepancies of the measured data to simulations based on a simple and complex detector geometry are discussed.

Microdosimetry of a 62-MeV clinical proton beam with five detectors.

In proton therapy, most treatment planning systems (TPS) use a fixed relative biological effectiveness (RBE) of 1.1 all along the depth-dose profile. Innovative TPS are now investigated considering the variability of RBE with radiation quality. New TPS need an experimental verification in the quality assurance (QA) routine in clinics, but RBE data are usually obtained with radiobiological measurements that are time consuming and not suitable for daily QA. Microdosimetry is a useful tool based on physical measurements which can monitor the radiation quality. Several microdosimeters are available in different research institutions, which could potentially be used for the QA in TPS. In this study, the response functions of five detectors in the same 62-MeV proton Spread Out Bragg Peak is compared in terms of spectral distributions and their average values and microdosimetric RBE. Their different response function has been commented and must be considered in the clinical practice.

Super antiwear properties of polytetrafluoroethylene (PTFE) induced by MeV proton irradiation

In this paper, the surface of polytetrafluoroethylene (PTFE) was modified by 1 MeV proton beam at high temperature. The changes of wear resistance and hardness of PTFE before and after irradiation were evaluated by ball/pin disk friction loss tester and nanoindentation tester, respectively. The results showed that the wear resistance of PTFE irradiated by proton at high temperature has been significantly enhanced. The mass wear rate decreases from 2.75 × 10−6 g/Nm to 0.39 × 10−6 g/Nm, and the wear depth decreases from 29.9 μm to 8.2 μm, respectively. Proton irradiation could be a simple and effective method for PTFE surface modification and can significantly improve the wear resistance. The potential chemical reaction mechanism for the improvement of wear resistance of irradiated PTFE in terms of microstructure was discussed. Crosslinking induced by proton irradiation enhanced the interaction force among PTFE molecules, thus the mechanical properties were improved.

47Sc production with proton beams on isotopically enriched 48Ti and 49Ti targets

The theranostic emerging radionuclide 47Sc is under the spotlight of the scientific community due to its medically favorable decay characteristics (t1/2 =3.3492 d, Eγ=159.381 keV, E β−, mean =162.0 keV) for both the diagnostic and treatment procedures. In the framework of the LaRAMED (LAboratory of RAdionuclides for MEDicine) program at INFN-LNL (National Institute of Nuclear Physics-Legnaro National Laboratories), the investigation of the possible 47Sc production routes using a 70 MeV proton beam is one of the goals of the REMIX (Research on Emerging Medical radIonuclides from the X-sections) project, funded by INFN for the years 2021-2023. Since the LARAMED bunkers are currently under completion, experiments are performed in collaboration with the GIP ARRONAX facility (Nantes, France), where a 70 MeV multi-particle cyclotron is operational. In this work, the cross-section measurements using enriched 48,49Ti targets are reported and the results presented in comparison to the previous literature data, when available. The 47Sc excitation functions are analyzed in relation to the contaminants’ ones since the co-produced radionuclides can affect the dose delivered to a patient. 46Sc cross-section curves are mainly taken into account since 46Sc cannot be chemically separated from 47Sc and its half-life (t1/2=83.79 d) is longer than the 47Sc one (t1/2=3.3492 d).

Ion-source development at the off-line LERIB test-facility at iThemba LABS

The Low Energy Radioactive Ion Beam (LERIB) facility [1] will be used to produce low-energy radioactive-ion beams (RIBs) with energies up to 60 keV. Radioactive reaction products will be created by a 66 MeV proton-beam impinging on a target made of carbide disks, such as SiC [2]. These reaction products will then be ionized in a target-ion-source (TIS) and extracted as beam. The TIS design allows three ion-sources: a surface ion-source [3], a forced electron-beam induced arc-discharge (FEBIAD) ion-source [4], and a resonance-ionization laser ion-source, or RILIS. The surface-ionization source was commissioned with stable beams in October 2021. The production of ions from Group-1 elements was accomplished with beams of 39K+, 41K+ and 23Na+ where currents were measured in the μA range. This source may be advantageous for producing stable pilot-beams for future radioactive-beam experiments. The FEBIAD is still in development at present.

Drift Velocity Measurement of the Prototype Beam Drift Chamber (pBDC) by using 100 MeV Proton Beam Produced by the HIMAC Facility

Drift Velocity Measurement of the Prototype Beam Drift Chamber (pBDC) by using 100 MeV Proton Beam Produced by the HIMAC Facility

Wild bilberries – Superfood or health risk

Wild bilberries (Vaccinium myrtillus L.) were collected from 23 sites in Finland, dried, ground, homogenized and pressed into pellets. The pellets were irradiated in air with a 3 MeV proton beam from the Åbo Akademi MGC-20 cyclotron. The induced X-rays were measured, and elemental concentrations were calculated from the peak areas in the spectra. Elemental concentrations for K, Ca, Mn, Fe, Cu, Zn, Rb, and Sr were found to be above the detection limit of the method. A special focus was set on the high concentration of Mn (27 ± 16 µg/g). Already by consuming 100 g of fresh wild-grown bilberries the Recommended Dietary Allowance value for an adult male was exceeded. A child of 4–8 years old will reach the Tolerable Upper Intake Level of Mn (3 mg/day) by eating somewhat more than 100 g of bilberries in a day. In addition, the regional differences in elemental concentrations were found to be higher than earlier reported. The activity concentrations of Cs-137 in some of the bilberry samples were also measured and the equivalent dose to a person that annually consumes 2 kg of bilberries was found negligible (about 1 µSv).

Luminescence imaging of water irradiated by protons under FLASH radiation therapy conditions

Objective. FLASH radiation therapy with ultrahigh dose rates (UHDR) has the potential to reduce damage to normal tissue while maintaining anti-tumor efficacy. However, rapid and precise dose distribution measurements remain difficult for FLASH radiation therapy with proton beams. To solve this problem, we performed luminescence imaging of water following irradiation by a UHDR proton beam captured using a charge-coupled device camera. Approach. We used 60 MeV proton beams with dose rates of 0.03–837 Gy s−1 from a cyclotron. Therapeutic 139.3 MeV proton beams with dose rates of 0.45–4320 Gy s−1 delivered by a synchrotron-based proton therapy system were also tested. The luminescent light intensity induced by the UHDR beams was compared with that produced by conventional beams to compare the dose rate dependency of the light intensity and its profile. Main results. Luminescence images of water were clearly visualized under UHDR conditions, with significantly shorter exposure times than those with conventional beams. The light intensity was linearly proportional to the delivered dose, which is similar to that of conventional beams. No significant dose-rate dependency was observed for 0.03–837 Gy s−1. The light-intensity profiles of the UHDR beams agreed with those of conventional beams. The results did not differ between accelerators (synchrotron or cyclotron) and beam energies. Significance. Luminescence imaging of water is achievable with UHDR proton beams as well as with conventional beams. The proposed method should be suitable for rapid and easy quality assurance investigations for proton FLASH therapy, because it facilitates real-time, filmless measurements of dose distributions, and is useful for rapid feedback.

Boron Nanoparticle-Enhanced Proton Therapy for Cancer Treatment.

Proton therapy is one of the promising radiotherapy modalities for the treatment of deep-seated and unresectable tumors, and its efficiency can further be enhanced by using boron-containing substances. Here, we explore the use of elemental boron (B) nanoparticles (NPs) as sensitizers for proton therapy enhancement. Prepared by methods of pulsed laser ablation in water, the used B NPs had a mean size of 50 nm, while a subsequent functionalization of the NPs by polyethylene glycol improved their colloidal stability in buffers. Laser-synthesized B NPs were efficiently absorbed by MNNG/Hos human osteosarcoma cells and did not demonstrate any remarkable toxicity effects up to concentrations of 100 ppm, as followed from the results of the MTT and clonogenic assay tests. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell death under irradiation by a 160.5 MeV proton beam. The irradiation of MNNG/Hos cells at a dose of 3 Gy in the presence of 80 and 100 ppm of B NPs led to a 2- and 2.7-fold decrease in the number of formed cell colonies compared to control samples irradiated in the absence of NPs. The obtained data unambiguously evidenced the effect of a strong proton therapy enhancement mediated by B NPs. We also found that the proton beam irradiation of B NPs leads to the generation of reactive oxygen species (ROS), which evidences a possible involvement of the non-nuclear mechanism of cancer cell death related to oxidative stress. Offering a series of advantages, including a passive targeting option and the possibility of additional theranostic functionalities based on the intrinsic properties of B NPs (e.g., photothermal therapy or neutron boron capture therapy), the proposed concept promises a major advancement in proton beam-based cancer treatment.

Synthesis and characterization of Ce3+-doped barium-gadolinium-fluoroborate glasses for proton beam diagnostic

By using a melt-quenching technique in an air atmosphere, barium-gadolinium-fluoroborate scintillating glasses with different concentrations of BaO and CeF3 were fabricated. The purpose of developing glasses is to be applied as proton or x-ray energy detectors for medical purposes. Physical and scintillating properties of the fabricated glasses were tested and analyzed, including glass density and spectroscopic properties such as transmittance, photoluminescence, x-ray absorption near edge structure, and x-ray-induced luminescence. Moreover, the glasses were impinged by a 70 MeV proton beam at the Proton Center of King Chulalongkorn Memorial Hospital to observe their proton-induced light emission. The absorption edge of the transmittance revealed that the glasses showed a redshift at high concentrations of BaO and CeF3. The glasses had a broad emission band centering around 400 nm due to the 5d–4f transition of Ce3+ induced by x-ray. The higher light yield was observed at a higher cerium compound glass. Our glass can clearly measure the depth-dose profile of the impinging proton beam by varying different water thicknesses. Moreover, the depth-dose profile results are in good agreement with that of the energy deposition of proton beams in glass calculated via GATE simulation.

Monte Carlo simulation of a high-efficacy composite material: feasibility for neutron and gamma ray shielding of Small Modular Reactor (SMR) facilities

Secondary neutrons with energy distribution similar to that of a Small Modular Reactor (SMR) was generated by bombarding a water target with 10 MeV proton beam from a Cyclotron and analyzed using Monte Carlo (MC) technique. Transmission of neutrons (SMR-Analogue) through a batch of spheres (r = 20 cm) made of a composite of Lead (PB), Boron Carbide (BC) and Polyethylene (PL) granules of varying volume concentrations was investigated. An optimized blend of 50%(vol) PB, 2%(vol) BC and 48%(vol) PL: (50PB2BC48PL) giving the lowest neutron transmission factor was evaluated. The tenth value layer thickness (TVLT) relevant to SMR neutrons in the optimized composite and in ordinary concrete was calculated to be 5.6 cm and 25.4 cm respectively. The high (50% vol) Lead content guaranteed a high attenuation of gamma rays co-produced by neutron activation of reactor cooling water. Feasibility of the high-efficacy optimized compact composite in radiological shielding of SMR is envisaged.

Recent progress of ISOL facility at RAON

The RAON (Rare Isotope Accelerator complex for ON-line experiments) is currently in the stage of commissioning under the Rare Isotope Science Project (RISP) launched in 2011. RAON will utilize an advanced rare isotope beams produced with a high power target by the Isotope Separation On-Line (ISOL) facility, aiming to deliver high purity and intense, neutron-rich rare isotope beams to the post-accelerator and experimental facilities. The RAON ISOL facility consists of a target/ion source module surrounded by movable shielding blocks in a bunker, remote handling facilities for the target operation, a pre-mass separator, a RFQ cooler buncher, an EBIS charge breeder, and an A/q separator. The installation and alignment of the ISOL facility were completed in June 2021. The target/ion source module allows us to bombard a thick target with a 70 MeV proton beam of RAON, producing a variety of rare isotope beams. Rare isotope beams extracted from the target/ion source can be transported to a pre-mass separator at energies of up to 60 keV, and will be cooled in a RFQ-CB. Cooled ion beams can be sent to two different experimental facilities, such as a Mass Measurement System and a Collinear Laser Spectroscopy in ISOL experimental hall. Alternatively, for post-acceleration of ion beams, the singly charged ion beam of interest can be bunched to 108 ions in RFQ-CB and then delivered to the EBIS charge breeder through the EBIS branch system. The preparation of multi charged ion beams for the post-acceleration using the superconducting LINAC of SCL3 will be carried out through the EBIS charge breeder and A/q separator to match the energy of 10 keV/u with A/q < 6 with the requirement of RAON Injector.The first commissioning experiment of the ISOL system started in March 2021 using the 133Cs and 120Sn stable beams produced from the target container combined with the surface ion source and laser Ion source. The stable beam experiments have demonstrated the overall functioning of the RAON ISOL system, and we are planning to carry out the first RI beam test using the SiC target with 70 MeV proton of cyclotron in the coming months.

Analysis of rain-deposited dust on polysulfone membranes using proton-induced X-ray emission spectroscopy

Proton-induced X-ray emission spectroscopy (PIXE) is a long-established method of nondestructive elemental analysis for environmental samples. While a standard method of recovery of solids from rainwater involves filtration onto polysulfone media, PIXE analysis has not typically been used on such substrates. We describe methodologies of the University of North Texas Ion Beam Laboratory for PIXE analysis of dust in Texas rainwater on polysulfone membranes from the National Atmospheric Deposition Program (NADP). PIXE analyses utilized a 2 MeV proton beam of 1 × 1 mm2 spot size with beam currents of 1–5nA. A 100 µm Al absorber attenuated X-rays produced by S native to the polysulfone and minimized pileup, allowing use of higher beam currents at the expense of detecting elements of Z < 22. Uniformity of dust deposition on the membranes was evaluated by utilizing Fe concentration as a dust tracer. Areas of uniform particulate deposition with comparable results to averages across the entire membrane were located, allowing reduced acquisition time. GeoPIXE software was used for quantitative analysis, and 18 elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Hg and Pb) were investigated for a collaborative project. Average minimum detection limits (MDL) were ≤ 10 ng/cm2 for 21 > Z greater than 36 and 10–30 ng/cm2 for 36 < Z < 83. Polysulfone is shown to be an appropriate substrate for PIXE analysis of environmental samples, especially when quantification of low-Z elements is not a priority.

Overview of nuclear data production system at RAON

Nuclear Data Production System (NDPS), a fast neutron facility for nuclear science and applications, was constructed at the Rare Isotope Accelerator complex for ON-line experiments (RAON) in Korea. NDPS is designed to provide both white and quasi-monoenergetic neutrons using 98 MeV deuteron and 20 – 83 MeV proton beams with thick graphite and thin lithium targets, respectively. Neutron energy is determined by employing the Time-Of-Flight (TOF) technique, along with a pulsed deuteron (or proton) beam with a repetition rate of less than 200 kHz. Fast neutrons are produced in the target room and are guided to the TOF room through a 4 m long neutron collimator consisting of iron and 5% borated polyethylene. The neutron beam is monitored using a parallel plate avalanche counter (PPAC) and a micro-mesh gaseous (MICROMEGAS) detector installed in the TOF room, so as to measure the energy and the position of neutrons.