Radiation Resistance Of Materials Research Articles

Effect of Phase Composition Variation of Oxy–Nitride Composite Ceramics on Heat Resistance and Preservation of Strength Parameters

The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics.

Determination of gamma radiation shielding efficiency by radiation-resistant composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics

This work examines the prospects of using composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics as shielding and radiation-resistant materials as structural materials in conditions of heightened radiation background, including gamma radiation and exposure to heavy ions. The key objective of the study is to determine the impact of the variation in composite ceramic composition on resistance to radiation damage caused by exposure to heavy ions comparable to nuclear fuel fission fragments, and to establish the effect of the radiation damage accumulation on the shielding characteristics of these ceramics, the maintenance of which determines the stability of the operation of nuclear materials by eliminating the ionization factor caused by the interaction of gamma quanta. During the studies, it was found that alterations in the phase composition of composite ceramics associated with the formation of ZrTiO4, AlWO3 and Nb2W3O14 phases in the structure lead not only to strengthening of the ceramics, but also to a rise in resistance to radiation damage, and associated changes in the damaged layer degradation, having an adverse impact on the shielding characteristics.

Revealing the critical role of vanadium in radiation damage of tungsten-based alloys

Refractory tungsten-based medium- and high-entropy alloys form a promising class of strong, heat- and radiation-resistant materials for nuclear applications. Here, we systematically explore the radiation tolerance of Mo–Nb–Ta–V–W alloys using molecular dynamics simulations and a machine-learned interatomic potential. Going from pure W to W-based equiatomic binaries, ternaries, quaternary, and the quinary high-entropy alloy, we simulate the radiation damage accumulation up to 0.4–0.8 dpa through cumulative collision cascades. We find that the radiation damage and evolution are controlled by a combination of cascade-induced clustering, the balance in migration of vacancies and interstitials, and defect cluster binding energies. These mechanisms are strongly influenced by atom size, among which vanadium as the smallest atom is decisive. In pure W and alloys without V, the microstructure is characterised by large and growing interstitial dislocation loops. In stark contrast, in alloys containing V, vacancy dislocation loops are formed directly in collision cascades and the balanced migration rate of vacancies and interstitials promotes recombination and prevents growth of interstitial loops. The atom size differences also lead to clear segregation, with small atoms (V) in interstitial clusters and larger atoms (Ta, Nb) segregating around vacancy clusters. Furthermore, the small cluster sizes, formation of vacancy loops, segregation, and balanced migration in V-containing alloys lead to low swelling and an exceptionally efficient defect annealing compared to pure W and V-free alloys. Our results highlight WTaV as a promising low-activation material, where almost 90% of defects are annealed at 2000 K during 5 ns compared to <20% in pure W.

Multiscale simulation study on radiation aging of EPDM and preparation of radiation-resistant materials

With the wide application of ethylene propylene diene monomer (EPDM) in the field of nuclear engineering, exploring the radiation aging mechanism of EPDM is of great significance to improve the radiation resistance of EPDM composites. In this paper, the radiation aging mechanism of EPDM was investigated by a combination of experiments and multiscale simulations, and EPDM composites with excellent radiation resistance were prepared. The radiation aging mechanism of EPDM involves the crosslinking and degradation of molecular chains. The aging of EPDM starts from the breakage of α-H in the 5-ethylidene-2-norbornene monomer. In addition, the screening strategy of radiation-resistant additives was proposed. Antioxidants N, N′-diphenyl-p-phenylene-diamine (H), N, N′-ditolyl-p-phenylenediamine (DTPD), and N, N′-di-2-naphthyl-p-phenylenediamine (DNP) were taken as the main research objects, and quantitative analysis was carried out from the aspects of chemical protection and physical protection. The screening results showed that DNP has excellent radiation resistance and migration resistance. The prepared EPDM-DNP composites showed outstanding radiation resistance with 94% tensile strength retention after 300 kGy irradiation. This work contributes to understand the mechanisms of radiation-induced material damage and guides the design of radiation-resistant materials.

SYNTHESIS OF MULTICOMPONENT HEAT-SHIELDING RADIATION-RESISTANT CERAMICS WITH VARIATION OF STOICHIOMETRY OF CERAMIC COMPONENTS

The paper presents the results of obtaining multicomponent heat-protective radiation-resistant ceramic materials based on the WO3–Bi2O3–ZnO–TeO2–CeO2–ZrO2 compounds obtained by mechanochemical solid-phase synthesis with further annealing at a temperature of 1000 °C. The introduction of doping substances into the structure in the form of metal oxides makes it possible to prevent undesirable structural changes in ceramics and improve the durability and stability of the system. The choice of the synthesis of ceramics based on zirconium oxide is associated with the presence of several valuable physical and mechanical properties of the substance, and, as a consequence, the possibility of application in the field of functional materials for use in a variety of technical fields. The processes of phase formation in multicomponent ceramics based on oxide refractory compounds (WO3, Bi2O3, ZnO, TeO2, CeO2, ZrO2) were studied by scanning electron microscopy, energy dispersive and x-ray phase analysis methods. Using a combination of the presented methods, the following results were obtained, which make it possible to comprehensively characterize the samples under study, as well as establish the dependence of the influence of variations in the oxides used on the phase composition and morphological features of the ceramics. Analysis of morphological parameters showed that with increasing dopant concentration, a denser structure of agglomerates is formed, which is associated with sintering of particles at higher dopant concentrations. According to the obtained results of energy dispersive analysis, it was found that the addition of ZrO2 results a slight redistribution of elements in the structure, so the atomic content of Ce, W, Bi, and Te decreased by 2.58; 3.38; 2.12; 1.91 times, respectively, and the atomic content of Zn increased by 1.32 times. Analysis of diffraction patterns showed that the studied samples WO3-Bi2O3-ZnO-TeO2-CeO2-ZrO2 are characterized by the content of Zn3(TeO6), ZnTeO3, CeO2, Bi2O3, Bi2WO6, ZnWO4, Ce5Zr3O16, ZnO, (Zr0.98Ce0.02)O2 phases.

Role of aging temperature on thermal stability of Co-free Cr0.8FeMn1.3Ni1.3 high-entropy alloy: Decomposition and embrittlement at intermediate temperatures

This study prepared a reduced activation single-phase Co-free Cr0.8FeMn1.3Ni1.3 high-entropy alloy (HEA) through arc melting, which exhibits great potential as a radiation-resistant material. The microstructural evolution and mechanical property changes of the alloy after prolonged aging at temperatures of 300, 500, and 700 °C were systematically studied using scanning and transmission electron microscopy (SEM/TEM/STEM) and electron probe microanalysis (EPMA) techniques. The results reveal that the alloy forms a single-phase FCC solid solution following cold deformation and subsequent recrystallization annealing. After prolonged aging at 300 °C for 1500 h, the microstructure of the alloy remains stable, maintaining a single-phase structure with minimal changes in mechanical properties. After aging at 500 °C for 1500 h, the alloy undergoes complex phase decomposition, giving rise to tetragonal σ-FeCr and L10-NiMn phases, along with minor amounts of Cr-rich BCC and Fe-rich FCC phases. During this stage, the interfaces between σ-FeCr and L10-NiMn phases undergo amorphization, leading to room-temperature embrittlement of the alloy. Following aging at 700 °C for 1500 h, the alloy precipitates the Cr-rich BCC phase, forming a dual-phase microstructure, resulting in increased tensile strength and reduced ductility. This study discloses the thermal stability of Cr0.8FeMn1.3Ni1.3 HEA through extended aging at 300 °C and 500–700 °C for up to 300 h, simultaneously providing reference values for evaluating the stability of other HEA systems. The occurrence of complex phase decomposition significantly impacts the mechanical properties of HEAs, necessitating cautious evaluation of their application potential.

Defects Act in an “Introverted” Manner in FeNiCrCoCu High-Entropy Alloy under Primary Damage

High-entropy alloys (HEAs) attract much attention as possible radiation-resistant materials due to their several unique properties. In this work, the generation and evolution of the radiation damage response of an FeNiCrCoCu HEA and bulk Ni in the early stages were explored using molecular dynamics (MD). The design, concerned with investigating the irradiation tolerance of the FeNiCrCoCu HEA, encompassed the following: (1) The FeNiCrCoCu HEA structure was obtained through a hybrid method that combined Monte Carlo (MC) and MD vs. the random distribution of atoms. (2) Displacement cascades caused by different primary knock-on atom (PKA) energy levels (500 to 5000 eV) of the FeNiCrCoCu HEA vs. bulk Ni were simulated. There was almost no element segregation in bulk FeNiCrCoCu obtained with the MD/MC method by analyzing the Warren–Cowley short-range order (SRO) parameters. In this case, the atom distribution was similar to the random structure that was selected as a substrate to conduct the damage cascade process. A mass of defects (interstitials and vacancies) was generated primarily by PKA departure. The number of adatoms grew, which slightly roughened the surface, and the defects were distributed deeper as the PKA energy increased for both pure Ni and the FeNiCrCoCu HEA. At the time of thermal spike, one fascinating phenomenon occurred where the number of Frenkel pairs for HEA was more than that for pure Ni. However, we obtained the opposite result, that fewer Frenkel pairs survived in the HEA than in pure Ni in the final state of the damage cascade. The number and size of defect clusters grew with increasing PKA energy levels for both materials. Defects were suppressed in the HEA; that is to say, defects were “cowards”, behaving in an introverted manner according to the anthropomorphic rhetorical method.

Impacts of local chemical ordering on the primary radiation damage in Cr–Fe–Ni multi-principal element alloys

Face-centered cubic (FCC) single-phase multi-principal element alloys (MPEAs) have demonstrated promising irradiation resistance. The generation and evolution of irradiation defects are integral aspects to comprehend, as they offer valuable insights into the radiation resistance of materials. In this work, we use molecular dynamics simulations to investigate the primary radiation damage of CrFeNi FCC MPEAs, while focusing on the impact of local chemical ordering (LCO) on the generation and evolution of defects. Our simulation results reveal that the LCO reduces the probability of defect production, consequently mitigating the maximum number of defects. Furthermore, the LCO increases defect migration barriers, thereby impeding the migration of interstitial atoms and leading to an increased number of residual defects subsequent to primary damage. However, the dispersed distribution of defects throughout space facilitates the uniform nucleation of dislocations in subsequent irradiation cascades. Additionally, the increased migration energy acts as a barrier to the movement of defect clusters, impeding their growth and thereby enhancing the radiation resistance of MPEAs. Our findings underscore the potential for enhancing the radiation resistance of MPEAs through the deliberate tailoring of LCOs.

Proton Irradiation on Halide Perovskites: Numerical Calculations.

The results of numerical SRIM and SCAPS calculations for the ionization, displacement and heating of hybrid perovskites under the influence of protons (E = 0.15, 3.0 and 18 MeV) are presented and show that the lowest transfer energy is demonstrated by the MAPbI3, FAPbBr3 and FAPbI3 compounds, which represent the greatest potential for use as solar cells in space devices. On the other hand, it is found that perovskite compositions containing FA and Cs and with mixed cations are the most stable from the point of view of the formation of vacancies and phonons and are also promising as radiation-resistant materials with respect to powerful proton fluxes. Taking into account the lateral distribution of proton tracks showed that, at an energy level of several MeV, the release of their energy can be considered uniform over the depth and area of the entire solar cell, suggesting that the simple protection by plastic films from the low-energy protons is sufficient.

Radiation resistant optical components for high energy physics detectors

New detectors for future high-energy physics experiments will operate under unprecedented radiation dose rates. This condition requires improved radiation resistance on detector equipment. The consequent development of new materials, particularly optical materials, becomes crucial. In this work, optical components mean reflectors, light absorbers, or light transmitters. These materials, reflectors or light transmitters, are needed in detectors primarily to collect and transmit light from the scintillator to the PMT. When it comes to light absorbers, they are required to protect the detector from light from the environment. This work aims at studying selected optical materials with improved properties (functional and optical) and radiation resistance that can be used in new detectors at the Large Hadron Collider (LHC) experiments. Light transmittance, optical reflection, thermal characteristics, and radiation resistance were investigated to evaluate the proposed materials.We have developed optical systems based on siloxanes to continue our previous developments of radiation-resistant materials for radiation detectors. We also report a study of several reflective materials and light absorber introduced into the siloxane. Investigations have shown that these systems are radiation resistant to doses of at least 1 MGy.Tested samples were irradiated at linear electron accelerator LUE-40 in the National Science Center Kharkiv Institute of Physics and Technology (KIPT). The accelerated electrons were sent to the heavy complex targets to deliver the irradiation with gamma or neutron fluxes. The consequent gamma and neutron fluxes and doses were estimated with the GEANT4 simulation.

Effects of He-ion irradiation on microstructures of low activation Ti-Ta-V alloy from atomic simulations and irradiation experiments

Most conventional titanium alloys contain nuclides with long half-lives, which is not conductive to material recovery after decommissioning. To recover components from post-service reactors safely and effectively, it is necessary to use materials with low activation and rapid induction of radioactive decay. In this work, a low-activation α-titanium alloy Ti-5Ta-1.6 V was prepared and irradiated with 80 keV helium ions to 6.8 dpa at room temperature. The mechanical properties and irradiation swelling properties of Ti-5Ta-1.6 V alloy were mainly investigated. The results showed that compared with the commercially pure titanium alloy (CP-Ti), the mechanical properties of Ti-5Ta-1.6 V were substantially improved. After ion irradiation, the irradiation swelling rate of Ti-5Ta-1.6 V (in mass ratio) was found to be significantly lower than that of CP-Ti by atomic force microscopy (AFM) technology. Molecular dynamic (MD) simulations were used to study the irradiation behavior and cascade collisions process, and the Ti-5Ta-1.6 V produced a small number of stable defects with cluster size and number density, which is consistent with the results of irradiation experiments. The results indicate that Ti-5Ta-1.6 V is expected to be a promising new titanium alloy for nuclear applications, which provides a new idea for the selection and optimization of low-activation and radiation-resistant nuclear materials.

Radiation-Resistant Electrical Insulation Materials for Superconducting Magnet Applications

To develop radiation-resistant electrical insulation materials suitable for cryogenic temperatures and applications that require radiation resistance such as future nuclear fusion energy systems, a United States Department of Energy Fusion Energy Sciences funded study was undertaken collaboratively by InnoSense LLC (ISL) and the Center for Advanced Power Systems. The goals for the new electrical insulation materials were low gas generation under irradiation, long pot life, high mechanical strength, good flexibility, and high dielectric strength. The development of proprietary metal oxide nanoparticle incorporated organic polymer composites (MOPOC) and their properties are reported. MOPOC consists of organic polyurethane (PU)-polyimide (PI) copolymers, ISL's proprietary and patented phenylated bipyridinium ionic polymers, and metal oxide nanoparticles. The results show the promise of the materials with the desired characteristics of mechanical, thermal, and pot life. Dielectric strength of 44 kV/mm and the suitability for cryogenic temperature application was demonstrated by room temperature and 77 K measurements. Preliminary gamma radiation exposure tests are promising. Further systematic investigations with larger doses on multiple compositions are planned in the next phase of the development with the extension of funding from the Department of Energy Fusion Energy Sciences and the established extended collaboration with the University of California Davis for neutron and proton beam exposure of the insulation samples.

Preparation and Study of a Radiation-Resistant Composite Material Based on V–Ti–Cr and Kh17N2 (Ferrite Steel 17Cr–12Ni–Fe)

Preparation and Study of a Radiation-Resistant Composite Material Based on V–Ti–Cr and Kh17N2 (Ferrite Steel 17Cr–12Ni–Fe)

Gamma radiation shielding simulation for thermoplastic elastomer and silicon rubber/alloy dopant with functional nanoparticle

With the global energy crisis worsening, the research and application of new energy have become a strategic objective for the major countries’ long-term development in the twenty-first century. Nuclear energy technology development and application have become central to new energy development. Numerous types of high-energy radiation (such as X-rays, gamma rays, and neutron rays) produced by nuclear materials not only impose stricter requirements on the radiation-resistant materials used in the reactor but also risk causing significant environmental pollution (nuclear pollution) and serious harm to human life and health if a leak does not form. As a result, the prudent control and protection of nuclear radiation have become critical issues in the development of nuclear energy. With the rapid development of nuclear power today, it is necessary to seek new nuclear radiation protection materials, particularly those with high energy, penetrating ability, and other neutron-protective material characteristics. This is a new type of nuclear power design and construction of critical materials. In this study, WinXCom software is used to simulate the shielding properties of the used functional shielding element, compounds of metal oxide, and the mixture of RTV and TPE with the functional nanoparticle and observe the K-edge absorption of the material used. Based on the simulation, the shielding performance of the selected element of Sm was observed to have the smallest weak gap absorption zone of 40-47 MeV in common medical radiation of 30-150 KeV. Different sets of combinations of shielding material were simulated and found that the combination of WO3 with Sm2O3 gave the most pronounced radiation shielding performance with two strong absorption peaks at 46.8 KeV and 69.5 KeV. RTV composite (Sm2O3+RTV+ WO3) with WO3 as matrix gave the best shielding performance and was used as a reference for the manufacture of the new type of shielding materials.

Effects of Carrier Transport Layers on Performance Degradation in Perovskite Solar Cells under Proton Irradiation

Perovskite solar cells (PSCs) are potentially ideal for use in space satellites and spacecraft. While perovskites were found to be robust to space particle irradiations, it is important to investigate the influences of the carrier transport layers in PSCs on the irradiation-induced performance degradation. This study reports on the responses of different CsMAFAPbI3-based PSCs to 250 keV proton irradiation. Spiro-OMeTAD is used as a hole transport material in the cells, whereas SnO2, TiO2, and In2O3 are used as electron transport materials. After irradiation, the three different cells are not degraded up to 1 × 1013 p/cm2 and follow a similar degradation trend with further increasing the proton fluence until they are completely destroyed at 6 × 1014 p/cm2. By means of recycling, it is shown that SnO2, TiO2, and In2O3 have little influence on cell degradation, although the square resistances of SnO2, TiO2, and In2O3 on FTO/glass substrates are increased by 15–19% after irradiation of 6 × 1014 p/cm2; instead, the degradation of the spiro-OMeTAD material accounts for the reduced performance of the PSCs. The proton irradiation leads to a de-doping effect of spiro-OMeTAD, causing an efficiency decrease of the PSCs. A more radiation-resistant hole transport material to replace spiro-OMeTAD is therefore warranted to extend the lifetime of the PSCs in space environments.

Structure, stability and defect energetics of interfaces formed between conventional and transformed phases in Cu–Nb layered nanocomposite

Layered nanocomposite material having fcc-bcc interface with Kurdjumov-Sachs interface orientation relation has shown great potential as radiation resistant structural material for future fusion energy reactors. The superior radiation resistant properties of this material are attributed to it’s special fcc-bcc interface structure. In this study we have reported a stable interface between conventional bcc phase of Nb and transformed bcc phase of Cu. This bcc-bcc interface is found to be stable from both strain-energy and dynamical stability analysis. We have also shown that the bcc-bcc interface has different defect energetics behaviour compared to previously reported fcc-bcc interface which has a negative impact on the self annihilation property of the material against radiation induced defects. These aspects should be carefully considered in the future design of robust layered material for extreme radiation environment.

Consequences of Neutron Energy Spectrum on Radiation Damage, Gas Production, and Transmutations in Fusion Materials

The inclusion of test modules in the U.S. Fusion Prototypic Neutron Source (FPNS) offers the opportunity to test a wide variety of materials in a representative radiation environment of the fusion Pilot Plant, DEMO, and power plant. The testing may include various generations of structural materials for conventional and advanced blanket and divertor concepts. Since all structural materials derived from the fission industry are inadequate for fusion applications (due to the more damaging effects of the 14-MeV fusion neutrons), radiation-resistant reduced-activation structural materials (reduced-activation ferritic-martensitic steel, vanadium alloy, W alloy, and SiC/SiC composites) were specifically developed for fusion and could be tested in the FPNS to qualify for the highly irradiated fusion components surrounding the plasma. The large atomic displacement and the helium and hydrogen generations by fusion neutrons are unique to fusion materials. The most important attribute for the FPNS would be the typical fusion-relevant He/displacements per atom (dpa) ratio of ~10 for steel in particular. By comparison, irradiation in the fission spectrum of the High Flux Irradiation Facility (HFIR) would underestimate the dpa and provide a very low He/dpa ratio of ~0.3 for steel, which is irrelevant to fusion. This paper reviews the neutron irradiation impacts and presents a few examples of dpa and transmutation products for steel, W, and SiC based on modeling in several fusion design studies. The operating conditions of advanced U.S. fusion power plants were considered along with the credible lifetime goal of 200 dpa and 20 MW·yr/m2 fluence that could be achieved with directed research and development programs coupled with the construction of the FPNS 14-MeV neutron facility.

Simultaneously efficient adsorption and highly selective separation of U(VI) and Th(IV) by surface-functionalized lignin nanoparticles: A novel pH-dependent process.

The simultaneous removal and selective separation of U(VI) and Th(IV) via adsorption remain challenging due to their strong mobility, reactivity, and similar chemical properties. Thus, a surface-functioned lignin nanoparticle (AL-PEI) was synthesized to adsorb U(VI)/Th(IV) in a unitary system via a pH-dependent process. In alkaline solution, AL-PEI exhibited excellent adsorption performance, and the maximum adsorption capacities for U(VI) and Th(IV) reached 392 and 396mg/g, respectively. Discrepantly in acidic solution, the adsorption performance of AL-PEI for U(VI) could still reach a high capacity (332mg/g), whereas highly limited adsorption capacity (less than 40mg/g) for Th(IV) was obtained, and the separation factor of U(VI) from U(VI)-Th(IV) matrix significantly reached 6662 in 3M of the HNO3 medium. The simultaneously efficient adsorption in alkaline solution and highly selective separation performance in acidic solution of AL-PEI also showed excellent anti-ions interference capacities, high reusability, and strong stability. This study is the first to apply lignin fabricating radiation-resistant adsorbent material, and the adsorbent displays good performance for U(VI)/Th(IV) removal and selective separation via a novel pH-dependent process, which is important to the green and sustainable development of nuclear energy and environmental protection.

Topological Defects Created by Gamma Rays in a Carbon Nanotube Bilayer.

Graphene sheets are a highly radiation-resistant material for prospective nuclear applications and nanoscale defect engineering. However, the precise mechanism of graphene radiation hardness has remained elusive. In this paper, we study the origin and nature of defects induced by gamma radiation in a graphene rolled-up plane. In order to reduce the environmental influence on graphene and reveal the small effects of gamma rays, we have synthesized a novel graphene-based nanocomposite material containing a bilayer of highly aligned carbon nanotube assemblies that have been decorated by organometallic compounds and suspended on nanoporous Al2O3 membranes. The bilayer samples were irradiated by gamma rays from a 137Cs source with a fluence rate of the order of 105 m-2s-1. The interaction between the samples and gamma quanta results in the appearance of three characteristic photon escape peaks in the radiation spectra. We explain the mechanism of interaction between the graphene sheets and gamma radiation using a pseudo-Majorana fermion graphene model, which is a quasi-relativistic N=3-flavor graphene model with a Majorana-like mass term. This model admits the existence of giant charge carrier currents that are sufficient to neutralize the impact of ionizing radiation. Experimental evidence is provided for the prediction that the 661.7-keV gamma quanta transfer enough energy to the electron subsystem of graphene to bring about the deconfinement of the bound pseudo-Majorana modes and involve C atoms in a vortical motion of the electron density flows in the graphene plane. We explain the radiation hardness of graphene by the topological non-triviality of the pseudo-Majorana fermion configurations comprising the graphene charge carriers.

Radiation effects in optical coatings for ITER diagnostics

The aim is to provide an assessment of radiation damage in coated films on refractive substrates that could be used as relevant information to protect the field lenses in optical diagnostics for ITER. Radiation-resistant optical materials with transparent properties should transfer light from plasma to detectors through the interspace until the port cell area where they are located (more than 10 m from the vacuum window). These optical coatings and substrates should have resilience enough to withstand neutron and gamma irradiation without significant degradation of their transmittance.Coated sapphire (Al2O3 windows), YAG with Broad Band Anti-Reflective (BBAR) and substrates of BaF2/CaF2 protected with anti-humidity coating (Parylene-C) were extensively tested. After testing, transmission measurements and analysis of optical surfaces yield significant discoveries. All substrates showed good refractive performance under gamma radiation. On the contrary, Parylene-C did not resist temperatures above 100 degrees Celsius as expected, according to manufacturing specifications. In addition, it was observed that with an energy dose of 332 kGy of gamma rays and a significantly lower temperature of 50 degrees Celsius, the Parylene-C protection is also damaged. Coated sapphire had the best overall performance with respect to the neutron irradiation tests. Nevertheless, the decrease in transmission observed in the YAG and BaF2 coated samples is not significant for the expected cumulative neutron dose that these samples will receive at their location within the diagnostic.This information was considered for the selection of the best candidates as refractive lenses and optical coatings for the Preliminary Design Review (PDR) of ex-vessel components that will integrate the Wide-Angle Viewing System (WAVS) for ITER Equatorial Port 12.