Radiation Damage Processes Research Articles

Oxidation of ultralene and paraffin due to radiation damage after exposure to soft X-rays probed by FTIR microspectroscopy and X-ray fluorescence.

Radiation damage upon soft X-ray exposure is an important issue to be considered in soft X-ray microscopy. The work presented here is part of a more extended study on the topic and focuses on the effects of soft X-rays on paraffin, a common embedding medium for soft-tissues, and on ultralene and Si3N4 windows as sample supports. Our studies suggest that the sample environment indeed plays an important role in the radiation damage process and therefore should be carefully taken into account for the analysis and interpretation of new data. The radiation damage effects were followed over time using a combination of Fourier transform infrared (FTIR) microspectroscopy and X-ray fluorescence (XRF), and it was demonstrated that, for higher doses, an oxidation of both embedding medium and ultralene substrate takes place after the irradiated sample is exposed to air. This oxidation is reflected in a clear increase of C=O and O-H infrared bands and on the XRF oxygen maps, correlated with a decrease of the aliphatic infrared signal. The results also show that the oxidation process may affect quantitative evaluation of light element concentrations.

SAXS studies of X-ray induced disulfide bond damage: Engineering high-resolution insight from a low-resolution technique.

A significant problem in biological X-ray crystallography is the radiation chemistry caused by the incident X-ray beam. This produces both global and site-specific damage. Site specific damage can misdirect the biological interpretation of the structural models produced. Cryo-cooling crystals has been successful in mitigating damage but not eliminating it altogether; however, cryo-cooling can be difficult in some cases and has also been shown to limit functionally relevant protein conformations. The doses used for X-ray crystallography are typically in the kilo-gray to mega-gray range. While disulfide bonds are among the most significantly affected species in proteins in the crystalline state at both cryogenic and higher temperatures, there is limited information on their response to low X-ray doses in solution, the details of which might inform biomedical applications of X-rays. In this work we engineered a protein that dimerizes through a susceptible disulfide bond to relate the radiation damage processes seen in cryo-cooled crystals to those closer to physiologic conditions. This approach enables a low-resolution technique, small angle X-ray scattering (SAXS), to detect and monitor a residue specific process. A dose dependent fragmentation of the engineered protein was seen that can be explained by a dimer to monomer transition through disulfide bond cleavage. This supports the crystallographically derived mechanism and demonstrates that results obtained crystallographically can be usefully extrapolated to physiologic conditions. Fragmentation was influenced by pH and the conformation of the dimer, providing information on mechanism and pointing to future routes for investigation and potential mitigation. The novel engineered protein approach to generate a large-scale change through a site-specific interaction represents a promising tool for advancing radiation damage studies under solution conditions.

Radiation damage behavior of amorphous SiOC polymer-derived ceramics: the role of in situ formed free carbon

Free carbon networks (FCN) in situ formed in the amorphous SiOC polymer-derived ceramics (PDCs) have been reported to have significant effects on the material microstructures as well as the related structural and functional properties. In this paper, detailed effects of the FCN on the radiation damage process and mechanisms of the amorphous SiOC PDC are investigated by using ab initio molecular dynamics simulations. The radiation simulations were conducted by introducing a random Si atom with kinetic energy of 80 eV as the primary knock-on atom. The FCN are proven to be beneficial to absorb the ion induced kinetic energy and convert it into thermal spike, which can be dissipated as thermal energy. The FCN interfaces with Si-O-C matrix can also capture the displaced atoms easily, thus reducing the cascade damage. The SiOC PDC is promising to be radiation tolerant materials for the prevention of radiation defect accumulation by the contained amorphous phase and FCN structure.

RADDOSE-XFEL: femtosecond time-resolved dose estimates for macromolecular X-ray free-electron laser experiments

For macromolecular structure determination at synchrotron sources, radiation damage remains a major limiting factor. Estimation of the absorbed dose (J kg−1) during data collection at these sources by programs such asRADDOSE-3Dhas allowed direct comparison of radiation damage between experiments carried out with different samples and beam parameters. This has enabled prediction of roughly when radiation damage will manifest so it can potentially be avoided. X-ray free-electron lasers (XFELs), which produce intense X-ray pulses only a few femtoseconds in duration, can be used to generate diffraction patterns before most of the radiation damage processes have occurred and hence hypothetically they enable the determination of damage-free atomic resolution structures. In spite of this, several experimental and theoretical studies have suggested that structures from XFELs are not always free of radiation damage. There are currently no freely available programs designed to calculate the dose absorbed during XFEL data collection. This article presents an extension toRADDOSE-3DcalledRADDOSE-XFEL, which calculates the time-resolved dose during XFEL experiments. It is anticipated thatRADDOSE-XFELcould be used to facilitate the study of radiation damage at XFELs and ultimately be used prior to data collection so that experimenters can plan their experiments to avoid radiation damage manifesting in their structures.

Analysis of nuclear radiation damage effect on typical materials

In order to evaluate the effects of nuclear radiation on several typical materials, the mathematical models of radiation damage characteristics of three materials are established based on the analysis of radiation environment and damage forms. In order to simplify the calculation, the principles and indexes of damage estimation are determined according to the radiation damage process of three typical materials: polymer materials, high-energy explosives, and metal materials. The results show that the pure nuclear radiation environment has no obvious effect on the properties of three typical materials. It lays a theoretical foundation for radiation hardening of devices.

Site-Selective Dissociation upon Sulfur L-Edge X-ray Absorption in a Gas-Phase Protonated Peptide.

Site-selective dissociation induced by core photoexcitation of biomolecules is of key importance for the understanding of radiation damage processes and dynamics and for its promising use as "chemical scissors" in various applications. However, identifying products of site-selective dissociation in large molecules is challenging at the carbon, nitrogen, and oxygen edges because of the high recurrence of these atoms and related chemical groups. In this paper, we present the observation of site-selective dissociation at the sulfur L-edge in the gas-phase peptide methionine enkephalin, which contains only a single sulfur atom. Near-edge X-ray absorption mass spectrometry has revealed that the resonant S 2p → σ*C-S excitation of the sulfur contained in the methionine side chain leads to site-selective dissociation, which is not the case after core ionization above the sulfur L-edge. The prospects of such results for the study of charge dynamics in biomolecular systems are discussed.

Optical reflectivity of ion-irradiated cerium dioxide sinters

Reflection spectra of cerium dioxide sintered samples were measured in the UV-visible range after irradiation with various heavy ions (2.4-MeV Cu, 5-MeV W, 10-MeV W, 36-MeV W, 100-MeV Kr, and 200-MeV Xe). Differential reflectance spectra of irradiated samples after subtraction of the reference sample spectrum are fit with six broad Gaussian bands centered at about 1.2, 2.2, 2.8, 4.0, 4.8, and 6.2 eV. The growth curves of most bands show a saturation behavior vs ion fluence. Reflection spectra are consistent with the UV-visible absorption spectra of electron-irradiated ceria single crystals for photon energies lower than 3.2 eV, corresponding to the optical gap. The spectra are tentatively analyzed on the basis of charge transfer bands and the 4f-5d transitions related to the Ce3+ ions in the distorted environment formed by irradiation. More insight into defect formation is given by the reflection spectra rather than the absorption ones due to the limitation in the absorption of the optical gap. These data are also discussed with reference to the radiation damage processes by electronic excitations and nuclear collisions in ceria.

Resolution and dose dependence of radiation damage in biomolecular systems.

The local Fourier-space relation between diffracted intensity I, diffraction wavevector q and dose D, , is key to probing and understanding radiation damage by X-rays and energetic particles in both diffraction and imaging experiments. The models used in protein crystallography for the last 50 years provide good fits to experimental I(q) versus nominal dose data, but have unclear physical significance. More recently, a fit to diffraction and imaging experiments suggested that the maximum tolerable dose varies as q -1 or linearly with resolution. Here, it is shown that crystallographic data have been strongly perturbed by the effects of spatially nonuniform crystal irradiation and diffraction during data collection. Reanalysis shows that these data are consistent with a purely exponential local dose dependence, = I 0(q)exp[-D/D e(q)], where D e(q) ∝ q α with α ≃ 1.7. A physics-based model for radiation damage, in which damage events occurring at random locations within a sample each cause energy deposition and blurring of the electron density within a small volume, predicts this exponential variation with dose for all q values and a decay exponent α ≃ 2 in two and three dimensions, roughly consistent with both diffraction and imaging experiments over more than two orders of magnitude in resolution. The B-factor model used to account for radiation damage in crystallographic scaling programs is consistent with α = 2, but may not accurately capture the dose dependencies of structure factors under typical nonuniform illumination conditions. The strong q dependence of radiation-induced diffraction decays implies that the previously proposed 20-30 MGy dose limit for protein crystallography should be replaced by a resolution-dependent dose limit that, for atomic resolution data sets, will be much smaller. The results suggest that the physics underlying basic experimental trends in radiation damage at T ≃ 100 K is straightforward and universal. Deviations of the local I(q, D) from strictly exponential behavior may provide mechanistic insights, especially into the radiation-damage processes responsible for the greatly increased radiation sensitivity observed at T ≃ 300 K.

Transition Metals Ion Behavior of Cathode Materials for Li Ion Battery By Electron Beam Irradiation in Scanning Transmission Electron Microscopy

Investigating the structural properties of Li-ion batteries (LIBs) and, if possible, determining the overall structure is important in understanding the physical and chemical properties. Understanding the structural properties and the electrochemical properties of the arranged atoms of cathode materials is therefore essential for new battery material design and system optimization. Particularly, cathode materials such as LiNixMnyCo1-x-yO2 (NMC), lithium-rich Li(LiyNix-yMnxCo1-2x)O2, lithium-rich / manganese-rich xLi2MnO3 (1-x)LiMO2 are analyzed by the scanning transmission electron microscopy (STEM) techniques to identify structural characteristics, leading to the conversion of the layer structure to the spinel and/or salt structure, leading to increased impedance, voltage reduction and capacity of the LIBs. The atomic behavior of Li ion in the cathode materials that determines LiBs performance is hardly characterized by transmission electron microscopy (TEM) owing to its weak electron-scattering power. In this sense, annular bright-field (ABF) STEM, in which the contrast has a low scaling rate with the atomic number, has been proven to be a robust technique for simultaneous imaging of light and heavy elements. However, it is very important to understand the damage mechanism of cathode materials by electron-beam irradiation in STEM and to develop this technique. In this study, we investigated the effect of electron-beam irradiation damage on the surface reaction layer and LiNi0.6Co0.2Mn0.2O2 material during STEM data acquisition. This electron-beam irradiation damage process is similar to the lattice reconstruction and chemical evolution caused by the charge-discharge cycle. Furthermore, based on the phase transition phenomenon by the electron-beam irradiation, it is examined whether the electron beam irradiation damage in the lattice structure substituted by Al and Ti affects the phase transition phenomenon.

Resolution and dose dependence of radiation damage in biomolecular systems

The local Fourier-space relation between diffracted intensity I, diffraction wavevector q and dose D, \tilde I(q,D), is key to probing and understanding radiation damage by X-rays and energetic particles in both diffraction and imaging experiments. The models used in protein crystallography for the last 50 years provide good fits to experimental I(q) versus nominal dose data, but have unclear physical significance. More recently, a fit to diffraction and imaging experiments suggested that the maximum tolerable dose varies as q−1 or linearly with resolution. Here, it is shown that crystallographic data have been strongly perturbed by the effects of spatially nonuniform crystal irradiation and diffraction during data collection. Reanalysis shows that these data are consistent with a purely exponential local dose dependence, \tilde I(q,D) = I0(q)exp[−D/De(q)], where De(q) ∝ qα with α ≃ 1.7. A physics-based model for radiation damage, in which damage events occurring at random locations within a sample each cause energy deposition and blurring of the electron density within a small volume, predicts this exponential variation with dose for all q values and a decay exponent α ≃ 2 in two and three dimensions, roughly consistent with both diffraction and imaging experiments over more than two orders of magnitude in resolution. The B-factor model used to account for radiation damage in crystallographic scaling programs is consistent with α = 2, but may not accurately capture the dose dependencies of structure factors under typical nonuniform illumination conditions. The strong q dependence of radiation-induced diffraction decays implies that the previously proposed 20–30 MGy dose limit for protein crystallography should be replaced by a resolution-dependent dose limit that, for atomic resolution data sets, will be much smaller. The results suggest that the physics underlying basic experimental trends in radiation damage at T ≃ 100 K is straightforward and universal. Deviations of the local I(q, D) from strictly exponential behavior may provide mechanistic insights, especially into the radiation-damage processes responsible for the greatly increased radiation sensitivity observed at T ≃ 300 K.

Deep learning inter-atomic potential model for accurate irradiation damage simulations

We propose a hybrid scheme that smoothly interpolates the Ziegler-Biersack-Littmark (ZBL) screened nuclear repulsion potential with a deep learning potential energy model. The resulting deep potential-ZBL model can not only provide overall good performance on the predictions of near-equilibrium material properties but also capture the right physics when atoms are extremely close to each other, an event that frequently happens in computational simulations of irradiation damage events. We applied this scheme to the simulation of the irradiation damage processes in the face-centered-cubic aluminum system and found better descriptions in terms of the defect formation energy, evolution of collision cascades, displacement threshold energy, and residual point defects than the widely adopted ZBL modified embedded atom method potentials and their variants. Our work provides a reliable and feasible scheme to accurately simulate the irradiation damage processes and opens up extra opportunities to solve the predicament of lacking accurate potentials for enormous recently discovered materials in the irradiation effect field.

Radiation damage in protein crystallography at X-ray free-electron lasers.

Radiation damage is still the most limiting factor in obtaining high-resolution structures of macromolecules in crystallographic experiments at synchrotrons. With the advent of X-ray free-electron lasers (XFELs) that produce ultrashort and highly intense X-ray pulses, it became possible to outrun most of the radiation-damage processes occurring in the sample during exposure to XFEL radiation. Although this is generally the case, several experimental and theoretical studies have indicated that structures from XFELs may not always be radiation-damage free. This is especially true when higher intensity pulses are used and protein molecules that contain heavy elements in their structures are studied. Here, the radiation-damage mechanisms that occur in samples exposed to XFEL pulses are summarized, results that show indications of radiation damage are reviewed and methods that can partially overcome it are discussed.

Ion beam induced phase transformation and krypton bubble formation in monoclinic zirconium oxide

Low energy krypton ion beam induced phase transformation and bubble formation in monoclinic zirconia (ZrO2) has been studied using electron microscopy, Raman scattering, grazing incidence X-ray diffraction and photoluminescence spectroscopy. The zirconia samples were synthesized by the thermal decomposition method and 60 keV Kr+ ion irradiation was carried out at 300 K and 143 K. The as-sintered ZrO2 particles were found to be monoclinic in structure, however, upon 60 keV Kr+ ion irradiation, a fraction of the sample (∼4.9% (300 K) and ∼8.3% (143 K) for the ion fluence of 1 × 1017 ions/cm2) was transformed from monoclinic to tetragonal phase along with the formation of krypton bubbles. The size of the bubbles is found to increase with the ion fluence, irrespective of the sample temperature during ion irradiation. The phase transformation from monoclinic to tetragonal structure was mainly due to radiation damage process where the driving force is strain field associated with the O-vacancies. The monoclinic to tetragonal transformation rate is faster when the ion irradiation was carried out at 143 K and this is attributed to the immobility of defects and production of large number of oxygen vacancies. The krypton bubble formation might be hindering the monoclinic to tetragonal phase transformation rate.

Structural integrity and characteristics at lattice and nanometre levels of ZrN polycrystalline irradiated by 4 MeV Au ions

We report an as-hot-pressed zirconium nitride polycrystalline with its primary crystal structure maintained no change but lattice defects and features were introduced at nanometre-scale after being irradiated by 4 MeV Au2+ with a total fluence of 5 × 1016/cm2. The variation of grey-level seen in backscattered electron images and electron backscattered diffraction maps directly evidenced the structure integrity of the polycrystalline ZrN is well maintained with no crystal structure change of ZrN. The irradiation depth had no relevance to crystal orientation, and Au deposition peaked at a depth of ∼0.58 μm with a near-Gaussian distribution. Within a depth <0.58 μm, long dislocation lines were developed with a Burgers vector of [01¯]b/2 and density 3.2 × 1014 1/m2; beyond this depth, dislocation loops were formed with much higher density. In the ionization zone, cubic ZrO2 crystallites precipitated in a size of ∼5 nm. The irradiation damage processes are discussed based on the observed features.

Mesoscale simulations of radiation damage effects in Materials: A SEAKMC perspective

Radiation damage presents a unique challenge for material simulations, with processes ranging from picoseconds to decades in time and nanometers to meters in length. Particularly, the understanding of many processes and fundamental mechanisms at the mesoscale are still lacking. In this paper, the self-evolving kinetic Monte Carlo (SEAKMC) method and its application to study mesoscale defect interaction is presented. SEAKMC is an off-lattice atomistic kinetic Monte Carlo approach which conducts ‘on-the-fly’ saddle point searches (SPS) using selective active volumes. The main components of SEAKMC are examined with focus on the comparative benefits of this method. Future areas of improvement are outlined, including suggestions for general improvements to SPS methods by reducing redundant searching and making predictive initial guesses for point defect migration events. Previous applications of SEAKMC to radiation effects in materials are briefly reviewed. Some potential applications of SEAKMC are given, including discussion of dislocation bias, and the further study of interaction between dislocation loops and point defects, which provide useful insights to understand void swelling, radiation induced segregation, and other important radiation damage processes.

Radiation damage in protein crystallography at X-ray free-electron lasers

Radiation damage is still the most limiting factor in obtaining high-resolution structures of macromolecules in crystallographic experiments at synchrotrons. With the advent of X-ray free-electron lasers (XFELs) that produce ultrashort and highly intense X-ray pulses, it became possible to outrun most of the radiation-damage processes occurring in the sample during exposure to XFEL radiation. Although this is generally the case, several experimental and theoretical studies have indicated that structures from XFELs may not always be radiation-damage free. This is especially true when higher intensity pulses are used and protein molecules that contain heavy elements in their structures are studied. Here, the radiation-damage mechanisms that occur in samples exposed to XFEL pulses are summarized, results that show indications of radiation damage are reviewed and methods that can partially overcome it are discussed.

Comparison of Interfacial Strengthening in Creep Deformation and Radiation Damage Processes of Advanced Structural Materials for Nuclear Applications

The mechanisms for microstructural strengthening in creep deformation and radiation damage processes of advanced structural materials for nuclear applications are compared. During creep and irradiation, various defects are generated and move in the microstructure. Any microstructural features that can retard such defect movement may improve both creep and radiation damage resistance. Interfaces in the microstructure are important barriers for preventing defect motion. To achieve ultrahigh strength and enhanced radiation damage resistance, an extremely high density of interfaces has been designed in recently developed nanostructured materials. However, interface-mediated processes may govern the deformation of these materials, decreasing their creep properties. Methods for improving the creep resistance of nanostructured materials are reviewed and discussed.

Structural changes of Ti3SiC2 induced by helium irradiation with different doses

In this study, the microstructure changes of Ti3SiC2 MAX phase material induced by helium irradiation and evolution with a sequence of different helium irradiation doses of 5 × 1015, 1 × 1016, 5 × 1016 and 1 × 1017cm−2 at room temperature (RT) were characterized with grazing incidence X-ray diffraction (GIXRD) and Raman spectra analysis. The irradiation damage process of Ti3SiC2 can be roughly divided into three stages according to the level of helium irradiation dose: (1) for a low damage dose, only crystal and damaged Ti3SiC2 exit; (2) at a higher irradiation dose, there is some damaged TiC phase additionally; (3) with a much higher irradiation dose, crystal TiC phase could be found inside the samples as well. Moreover, the 450 °C 5 × 1016 cm−2 helium irradiation on Ti3SiC2 has confirmed that Ti3SiC2 has much higher irradiation tolerance at higher temperature, which implies that Ti3SiC2 could be a potential future structural and fuel coating material working at high temperature environments.

Dose-rate dependence of damage buildup in 3C-SiC

The influence of the defect generation rate on radiation damage processes in SiC remains poorly understood. Here, we use a combination of ion channeling and transmission electron microscopy to systematically study the dose-rate dependence of damage buildup in 3C-SiC bombarded in the temperature range of 25–200 °C with 500 keV Ar ions. The results reveal a pronounced dose-rate effect, whose magnitude increases close-to-linearly with temperature. When ion dose and temperature are held constant, the dose-rate dependence of the damage level is nonlinear, with saturation at high dose rates. Electron microscopy reveals that the average size of stable defect clusters increases with increasing dose rate. These findings have important implications for understanding and predicting radiation damage in SiC.

Methodology trends on gamma and electron radiation damage simulation studies in solids under high fluency irradiation environments

The present work deals with the numerical simulation of gamma and electron radiation damage processes under high brightness and radiation particle fluency on regard to two new radiation induced atom displacement processes, which concern with both, the Monte Carlo Method based numerical simulation of the occurrence of atom displacement process as a result of gamma and electron interactions and transport in a solid matrix and the atom displacement threshold energies calculated by Molecular Dynamic methodologies. The two new radiation damage processes here considered in the framework of high brightness and particle fluency irradiation conditions are: 1) The radiation induced atom displacement processes due to a single primary knockout atom excitation in a defective target crystal matrix increasing its defect concentrations (vacancies, interstitials and Frenkel pairs) as a result of a severe and progressive material radiation damage and 2) The occurrence of atom displacements related to multiple primary knockout atom excitations for the same or different atomic species in an perfect target crystal matrix due to subsequent electron elastic atomic scattering in the same atomic neighborhood during a crystal lattice relaxation time. In the present work a review numeral simulation attempts of these two new radiation damage processes are presented, starting from the former developed algorithms and codes for Monte Carlo simulation of atom displacements induced by electron and gamma in