Radiation Damage Studies Research Articles

A Multifield and Frequency Electrically Detected Magnetic Resonance Study of Atomic-Scale Defects in Gamma Irradiated Modern MOS Integrated Circuitry

The role of specific atomic-scale defects involved in total ionizing dose radiation in the metal–oxide–semiconductor field-effect transistors of the 1980s and 1990s was identified in large part with electron paramagnetic resonance (EPR) techniques. The techniques involved in those studies were classical EPR and, to a lesser extent, electrically detected magnetic resonance (EDMR). We show that somewhat more sophisticated resonance-based measurements can be fruitfully applied to explore the atomic-scale basic mechanisms of the significantly more complex, generally messier, and much smaller devices of the present day. We present multifield and frequency EDMR measurements in which the response is observed via spin-dependent leakage currents, spin-dependent charge pumping, and spin-dependent gated diode recombination currents. We also exploit isotopic substitution, replacing hydrogen with deuterium, monitoring the isotopic effects on the resonance response. The approaches utilized in this paper should be applicable to radiation damage studies in a wide variety of emerging materials and devices.

Strain and damage build-up in irradiated crystals: Coupling X-ray diffraction with numerical simulations

Radiation damage in materials is a space and time multi-scale process, ranging from the atomic scale up to the macroscopic scale, and from the femtosecond up to several years. The prediction of the long term evolution of materials subjected to radiative environments (in the nuclear or in the space industry, as well as in the field of microelectronics) therefore requires the combination of several simulation and experimental techniques able to cover the different space and time scales involved. X-ray diffraction (XRD) is highly sensitive to atomic displacements while probing macroscopic volumes of material. In this respect it is perfectly suited for the study of radiation damage. In this work it is shown how XRD can be quantitatively and qualitatively used in combination with numerical simulations, like molecular dynamics and rate-equation cluster dynamics, to analyze damage build-up in irradiated SiC and ZrC single crystals. Particular emphasis is laid on the methodological aspects of XRD data treatment in order to extract parameters such as damage-induced strain and disorder.

Investigation of radiation resistance of AlN ceramics

The study of changes in physical-chemical and mechanical properties of ceramic nitride materials as a result of the effect of heavy ions is of great interest in the field of radiation-resistant materials. In the course of investigation conducted there has been determined the mechanisms of ionizing irradiation effect on change of the main crystallographic characteristics and performance characteristics of nitride ceramics (reduction of thermal conductivity, strength, electrical resistivity and microhardness). The choice of Fe7+ ions with energy of 85 MeV is due to possibility of modeling by using it a fission fragments in reactors. In turn, the determination of mechanisms of change of structural properties and radiation resistance of materials is an important factor in the study of radiation damage in materials for nuclear industry. It has been proved that when the density of ceramics decreases due to a change in the crystallographic characteristics, the conducting properties decrease and the resistance of ceramics to the formation of microcracks decreases. The application of the ATR-FTIR method allowed to examine the change in chemical bonds in the near-surface irradiated layer as a result of irradiation. In addition, the effect of various factors in the variation of diffraction peaks has been evaluated using the Williamson-Hall method, which evidences that at small doses the contributions from size effects and deformation of the structure due to stresses are equivalent. An increase in the irradiation dose up to 1 × 1013 ion/cm2 and higher, the greatest contribution to the change in the structural properties was due to the deformations of the crystal lattice, which are caused by the formation of a large concentration of regions with a high density of defects and oxide impurities in the crystal structure.

DNA structure change induced by guanosine radicals – A theoretical and spectroscopic study of proton radiation damage

Proton radiation therapy is one of the newest and most promising methods used in modern oncology. Nonetheless, the dissemination of that method may result challenging. This is partially due to the fact that the mechanism of DNA damage induced by protons, which is one of the ways proton radiation interacts with tissues, has not been fully understood yet. It is well known that ionizing radiation especially ions such as protons may directly damage DNA but it also causes the formation of radicals, which may lead to even more serious damage of the DNA sugar-backbone than direct interaction with charged ion. In this article we focus on the influence of guanine radicals on the DNA structure, namely the conformation and stability of the DNA strand. We present the theoretical results of the optimization calculations of DNA structures with guanine radical-adenine pairs as well as calculated Raman spectra. By combining theoretical calculations with the experimental spectra we were able to explain molecular modifications of the DNA sugar-backbone affected by guanine radicals formed upon radiation exposure, which lead to spectral changes between spectra of control and irradiated DNA. Thus we established a pathway of the formation of DNA damage caused by protons.

Experimental study of pulse neutron irradiation damage in SiGe HBT

ABSTRACT The response to transient irradiation of npn SiGe HBT (BG35 SiGe BiCMOS), i.e. device under test (DUT) was studied with online measurement of 1 MeV equivalent pulse neutron fluence of 0.8 × 1013n/cm2. The differently biased DUT1 and DUT2 in test circuit were irradiated in the first day with neutron fluence (0.8 × 1013n/cm2) termed as Fluence1 and with an additional neutron fluence (0.8 × 1013n/cm2) in the second day to make Fluence2 equals to 1.6 × 1013n/cm2. The experimental results show that pulsed neutron irradiation causes voltage surges in the DUTs exhibited by a negative and positive peak known to be radiation damage (RD). The RD in DUTs induced by pulse neutron Fluence1 initially created unstable displacement defects and the defects later reordered (cluster defects) to form more stable configurations via neutron Fluence2. The irradiated DUTs experienced online instantaneous annealing after 2.03 × 10−9 s and offline measurement (i.e. without irradiation) of DUTs showed recovery to normal mode of operation after 24 h annealing. The level of pulse peaks in the base voltage terminals of DUT1 and DUT2 were compared as Vb2 Fluence1 > Vb1 Fluence1 and Vb2 Fluence2 > Vb1 Fluence2. A comprehensive analysis of RD region in DUTs with reference to Area (A1, A2), Peak (P1, P2), Height (H), and Full width at half maximum (FWHM) were investigated.

The study of irradiation damage induced by proton in metallic glass Ni62Ta38 and metal W

The protons with an energy of 250 keV were used to irradiate metallic glass Ni62Ta38 and metal W, the changes in structure and surface morphology of both the materials were compared, and their performances against the irradiation were evaluated, in order to provide the reference for the possibility of application of metallic glass Ni62Ta38 in irradiation environment. The results showed that after the proton irradiation, metallic glass Ni62Ta38 still maintained its good amorphousness without obvious irradiation damage on its surface. Meanwhile, stress was generated in metal W, and its crystalline size, micro-strain and dislocation line density varied undulately with the increase of fluence. When the irradiation fluence was 1.0 × 1018 ions/cm2, large area of blisters were formed on the surface of metal W. The surface roughness of metal W increased with the fluence. Compared with metal W, the proton irradiation resistance of metallic glass Ni62Ta38 was better.

A systematic study of radiation damage in transition metal chloride complexes with 1,5-cyclooctadiene ligands using diffraction and spectroscopy

A systematic study of radiation damage in transition metal chloride complexes with 1,5-cyclooctadiene ligands using diffraction and spectroscopy

Radiation Damage Effects and Operation of the LHCb Vertex Locator

Vertex locator (VELO) is a silicon microstrip detector situated around the interaction point in the large Hadron Collider beauty (LHCb) spectrometer at the Large Hadron Collider. The LHCb experiment is dedicated to studying charge conjugation and parity symmetry violation in the heavy flavor sector and rare decays of B mesons. The precise reconstruction of both the primary and secondary vertices, obtained by the VELO, is crucial in the selection of signal events containing b and c quarks and lifetime measurements. VELO consists of two retractable parts that operate at 8 mm from the interaction region. Its proximity to proton beams makes the LHCb VELO a place for studying radiation damage effects in silicon detectors in proton–proton and heavy-ion collisions. The latest results from radiation damage studies and their impact on the operation of the LHCb VELO after the first data-taking period (Run I) and the ongoing Run II are presented in this paper. The main macroscopic parameters, influenced by particle fluence, are described along with selected methods of their monitoring. All the results show that VELO sustains the impact of high fluence of radiation, and its performance will not change significantly until the end of Run II.

An Estimation of the Neutron Displacement Damage Cross Section for Ga2O3

Gallium oxide (Ga2O3) has recently gained attention as an alternative power electronics semiconductor for aerospace applications. Irradiation damage studies are needed to characterize the radiation tolerance of this material. This paper presents coupled neutronics and primary knock-on atom transport simulations that have been performed to estimate the neutron displacement damage cross section for Ga2O3 as a function of neutron energy. This functional dependence will allow for improved comparisons between irradiation experiments of Ga2O3 using a variety of neutron fields. The methodology presented uses MCNP and transport of ions in matter to determine the displacement damage cross section, which has been calculated in a multigroup neutron energy structure. The calculational method was also validated against the ASTM standard damage cross section for silicon.

Study of self-ion irradiated nanostructured ferritic alloy (NFA) and silicon carbide-nanostructured ferritic alloy (SiC-NFA) cladding materials

Abstract Silicon carbide-nanostructured ferritic alloy (SiC-NFA) materials are expected to have the beneficial properties of each component for advanced nuclear claddings. Fabrication of pure NFA (0 vol% SiC-100 vol% NFA) and SiC-NFAs (2.5 vol% SiC-97.5 vol% NFA, 5 vol% SiC-95 vol% NFA) has been reported in our previous work. This paper is focused on the study of radiation damage in these materials under 5 MeV Fe++ ion irradiation with a dose up to ∼264 dpa. It is found that the material surfaces are damaged to high roughness with irregularly shaped ripples, which can be explained by the Bradley-Harper (B-H) model. The NFA matrix shows ion irradiation induced defect clusters and small dislocation loops, while the crystalline structure is maintained. Reaction products of Fe3Si and Cr23C6 are identified in the SiC-NFA materials, with the former having a partially crystalline structure but the latter having a fully amorphous structure upon irradiation. The different radiation damage behaviors of NFA, Fe3Si, and Cr23C6 are explained using the defect reaction rate theory.

Static and dynamic multipolar field expansions of dislocations and cracks in solids

This article provides a comprehensive analysis of the way multipolar field expansions, of common use in the study of point defects in solids, may be extended to study the long range fields of dislocations and cracks. The long range fields of such defects are of relevance in fields as disparate as dislocation dynamics, microcrack and fragmentation, or radiation damage studies. The article provides a general framework for the development of multipolar field expansions in the continuum; one that may be used for any generalised force distribution. The general framework is combined with the Burridge–Knopoff force representation of dislocations and cracks, both in the planar and in the three dimensional cases, to achieve their respective multipolar field expansions for generalised dislocation loop and crack geometries. It is shown that, despite its simplicity, the multipolar field expansions provide a very accurate measure of the far field of both planar and three dimensional dislocations and cracks, and that the accuracy increases as higher order terms (i.e., quadrupolar, octopolar, etc) are introduced into the expansion. The formulation is then extended to the elastodynamic case. Both a spatial-temporal multipolar field expansion and a spatial multipolar field expansion, are developed. The spatial-temporal multipolar field expansion is seen to capture only the leading terms of the elastodynamic fields, whilst the spatial multipolar expansions are seen to be very accurate at capturing the long range field behaviour so long as the characteristic speed of the dislocation or crack are a fraction of the longitudinal speed of sound.

Radiation Damage in Macromolecular Crystallography—An Experimentalist’s View

Radiation damage still remains a major limitation and challenge in macromolecular X-ray crystallography. Some of the high-intensity radiation used for diffraction data collection experiments is absorbed by the crystals, generating free radicals. These give rise to radiation damage even at cryotemperatures (~100 K), which can lead to incorrect biological conclusions being drawn from the resulting structure, or even prevent structure solution entirely. Investigation of mitigation strategies and the effects caused by radiation damage has been extensive over the past fifteen years. Here, recent understanding of the physical and chemical phenomena of radiation damage is described, along with the global effects inflicted on the collected data and the specific effects observed in the solved structure. Furthermore, this review aims to summarise the progress made in radiation damage studies in macromolecular crystallography from the experimentalist’s point of view and to give an introduction to the current literature.

A study to compute integrated dpa for neutron and ion irradiation environments using SRIM-2013

Displacements per atom (dpa), estimated based on the standard Norgett–Robinson–Torrens (NRT) model, is used for assessing radiation damage effects in fast reactor materials. A computer code CRaD has been indigenously developed towards establishing the infrastructure to perform improved radiation damage studies in Indian fast reactors. We propose a method for computing multigroup neutron NRT dpa cross sections based on SRIM-2013 simulations. In this method, for each neutron group, the recoil or primary knock-on atom (PKA) spectrum and its average energy are first estimated with CRaD code from ENDF/B-VII.1. This average PKA energy forms the input for SRIM simulation, wherein the recoil atom is taken as the incoming ion on the target. The NRT-dpa cross section of iron computed with “Quick” Kinchin-Pease (K-P) option of SRIM-2013 is found to agree within 10% with the standard NRT-dpa values, if damage energy from SRIM simulation is used. SRIM-2013 NRT-dpa cross sections applied to estimate the integrated dpa for Fe, Cr and Ni are in good agreement with established computer codes and data. A similar study carried out for polyatomic material, SiC, shows encouraging results. In this case, it is observed that the NRT approach with average lattice displacement energy of 25 eV coupled with the damage energies from the K-P option of SRIM-2013 gives reliable displacement cross sections and integrated dpa for various reactor spectra. The source term of neutron damage can be equivalently determined in the units of dpa by simulating self-ion bombardment. This shows that the information of primary recoils obtained from CRaD can be reliably applied to estimate the integrated dpa and damage assessment studies in accelerator–based self-ion irradiation experiments of structural materials. This study would help to advance the investigation of possible correlations between the damages induced by ions and reactor neutrons.

Molecular dynamics studies and irradiation effects in ODSS alloys

Radiation Damage (RD) studies on structural materials provide a way to understand a material's behaviour in a NPP. Oxide Dispersed Strengthened Steel (ODSS) alloys have been considered as one of the promising candidate materials in fast nuclear fission and fusion reactors. There are multiple mechanisms responsible for the microstructural changes instigating substantial alterations in the macroscopic properties of the material as well. Currently, various experimental and simulation studies on RD in ODSS alloys are being carried out owing to their radiation resistant property under different irradiation conditions. Owing to varying experimental approaches, the interpretations are usually incoherent. Simulating irradiation effect through Molecular Dynamics (MD) simulations offers necessary insight into the production of primary damage defects and microstructural evolution. MD simulations can reveal atomistic details of some hidden phenomena and their mechanistic understanding associated with ODSS alloys, such as: damage cascades, defects interface interactions and radiation stability at elevated temperature. Thus, it is highly desirable to understand the aforementioned phenomena through atomistic simulation techniques, although one simulation technique is not enough to cover ranges of RD. Hence, this paper reviews recent studies performed through MD simulations and irradiation effects in ODSS alloys.

Molecular dynamics studies and irradiation effects in ODSS alloys

Radiation Damage (RD) studies on structural materials provide a way to understand a material's behaviour in a NPP. Oxide Dispersed Strengthened Steel (ODSS) alloys have been considered as one of the promising candidate materials in fast nuclear fission and fusion reactors. There are multiple mechanisms responsible for the microstructural changes instigating substantial alterations in the macroscopic properties of the material as well. Currently, various experimental and simulation studies on RD in ODSS alloys are being carried out owing to their radiation resistant property under different irradiation conditions. Owing to varying experimental approaches, the interpretations are usually incoherent. Simulating irradiation effect through Molecular Dynamics (MD) simulations offers necessary insight into the production of primary damage defects and microstructural evolution. MD simulations can reveal atomistic details of some hidden phenomena and their mechanistic understanding associated with ODSS alloys, such as: damage cascades, defects interface interactions and radiation stability at elevated temperature. Thus, it is highly desirable to understand the aforementioned phenomena through atomistic simulation techniques, although one simulation technique is not enough to cover ranges of RD. Hence, this paper reviews recent studies performed through MD simulations and irradiation effects in ODSS alloys.

Radiation damage studies in fusion reactor steels by means of small-angle neutron scattering (SANS)

In this contribution, small-angle neutron scattering (SANS) studies of the micro-structural radiation damage in technical steels, developed for application in future fusion reactors, are presented. The effect of neutron irradiation at 250 °C–450 °C, up to dose levels of 16 dpa (displacement per atom), has been investigated in the European reference ferritic/martensitic steel Eurofer97 (0.12 C, 9 Cr, 0.2 V, 1.08 W wt%), both in its standard composition and mechanically alloyed with B (up to 1000 appm) to enhance the helium production, via transmutations, and reproduce fusion relevant helium/dpa ratios. The obtained SANS results suggest that in the irradiated standard Eurofer97 micro-voids distributions are present, with very small average radii (a few Å) and volume fractions (around 0.01); such low values, close to the SANS resolution limit, are consistent with the good resistance of this steel to radiation damage, for low helium concentrations. In the irradiated B-alloyed Eurofer97, more complex changes are observed: the helium bubble distributions appear strongly dependent on the irradiation temperature and on the helium concentration; furthermore, micro-structural effects possibly related to modifications in the steel matrix are detected.

Study and mitigation of radiation damage on the P12 BioSAXS beamline

Study and mitigation of radiation damage on the P12 BioSAXS beamline

Estimate your dose: RADDOSE-3D.

We present the current status of RADDOSE-3D, a software tool allowing the estimation of the dose absorbed in a macromolecular crystallography diffraction experiment. The code allows a temporal and spatial dose contour map to be calculated for a crystal of any geometry and size as it is rotated in an X-ray beam, and gives several summary dose values: among them diffraction weighted dose. This allows experimenters to plan data collections which will minimize radiation damage effects by spreading the absorbed dose more homogeneously, and thus to optimize the use of their crystals. It also allows quantitative comparisons between different radiation damage studies, giving a universal "x-axis" against which to plot various metrics.

Structural defects caused by swift ions in fluorite single crystals

A comparative study of radiation damage caused by the irradiation of oxygen-free calcium fluoride single crystals with ∼GeV 132Xe or 209Bi heavy ions, 100-keV light hydrogen ions (protons) or X-rays at room temperature has been performed. Optical absorption in a wide spectral region from NIR to VUV (1.5–10.5 eV), its dependence on stepwise preheating of the irradiated CaF2 crystals to a certain temperature as well as thermally stimulated luminescence accompanying the main annealing stages have been analyzed. It is shown that in addition to different F-type aggregates, Ca colloids and trifluorine quasi-molecules, complex and temperature stable structural defects responsible for VUV absorption (in particular, the 9.8 eV band) are induced in CaF2 only after irradiation with swift heavy ions. The origin and tentative creation mechanisms of such defects as well as the features of the used irradiation types are considered.

CERN IRRADIATION FACILITIES.

CERN provides unique irradiation facilities for applications in dosimetry, metrology, intercomparison of radiation protection devices, benchmark of Monte Carlo codes and radiation damage studies to electronics.