Annealing Of Damage Research Articles

Thermal annealing of radiation damages produced by swift 14N and 16O ions in LiF crystals

Annealing of color centers was studied in lithium fluoride crystals, irradiated with 23-MeV nitrogen and 28-MeV oxygen ions. Basing on the optical absorption spectroscopy and reaction-rate modelling, a new interpretation of the annealing kinetics at the practically important temperatures below 500 K is suggested. Proposed model explains simultaneous decrease of the F and F2/F3 + peaks as a result of migration of the F centers and formation of larger aggregates, and does not include additional assumptions about impurities and cation vacancies. It specifies the migration energy of the F centers in the ground state to be about 1.3 eV, that corresponds to earlier studies.

In situ heating high-resolution TEM observation of structural recovery in metamict titanite

Besides radiation resistance, thermal recovery of radiation damage provides another critical criterion to evaluate the host phase for immobilizing high-level waste (HLW) produced by nuclear plants. Despite the increasing investigations, a comprehensive atomic-scale understanding remains elusive on thermal annealing of radiation damage in ceramics. Here, using in situ heating high-resolution transmission electron microscopy, we investigate the thermal annealing of radiation damage in natural metamict titanite (CaTiSiO5) caused by a high alpha decay dose from the incorporated U and Th during the geologic time. The recovery of the fully amorphous titanite precursor starts at 456 ℃ from the appearances of monoclinic nanoparticles 2–5 nanometers wide, and more nanoparticles form as the temperature gradually increases. At 1000 ℃, the amorphous phase recovers through epitaxial growth with titanite nanoparticles as templates. This study provides information for a unit-cell-scale understanding of the thermal stability of radiation damage in titanite-based ceramics, having significance for immobilizing HLW.

Ion velocity effect governs damage annealing process in defective KTaO3

Effects of electronic to nuclear energy losses (S e/S n) ratio on damage evolution in defective KTaO3 have been investigated by irradiating pre-damaged single crystal KTaO3 with intermediate energy O ions (6 MeV, 8 MeV and 12 MeV) at 300 K. By exploring these processes in pre-damaged KTaO3 containing a fractional disorder level of 0.35, the results demonstrate the occurrence of a precursory stage of damage production before the onset of damage annealing process in defective KTaO3 that decreases with O ion energy. The observed ionization-induced annealing process by ion channeling analysis has been further mirrored by high resolution transmission electron microscopy analysis. In addition, the reduction of disorder level is accompanied by the broadening of the disorder profiles to greater depth with increasing ion fluence, and enhanced migration is observed with decreasing O ion energy. Since S e (∼3.0 keV nm−1) is nearly constant for all 3 ion energies across the pre-damaged depth, the difference in behavior is due to the so-called ‘velocity effect’: the lower ion velocity below the Bragg peak yields a confined spread of the electron cascade and hence an increased energy deposition density. The inelastic thermal spike calculation has further confirmed the existence of a velocity effect, not previously reported in KTaO3 or very scarcely reported in other materials for which the existence of ionization-induced annealing has been reported. In other words, understanding of ionization-induced annealing has been advanced by pointing out that ion velocity effect governs the healing of pre-existing defects, which may have significant implication for the creation of new functionalities in KTaO3 through atomic-level control of microstructural modifications, but may not be limited to KTaO3.

Connecting visual metamictization to radiation damage to expand applications of zircon (U-Th)/He thermochronometry

Zircon (U-Th)/He (ZHe) thermochronometry quantifies the timing and tempo of low-temperature processes and is used to deconvolve tectonic and erosional histories. Accumulation and annealing of radiation damage impacts He diffusion in zircon and resulting ZHe dates. Resolving complex histories requires building relationships between ZHe date, effective U (eU), and radiation damage in grains sharing a common thermal history. Prior work demonstrated that purposefully selecting grains with a spectrum of visual metamictization yields a broad range of intrasample eU values (Ault et al., 2018), but it remained unclear if visual metamictization tracks effective radiation damage. Here we evaluate relationships between visual metamictization, effective damage calculated from Raman spectroscopy, and ZHe dates from a new suite of grains from some of the same Precambrian samples investigated in Ault et al. (2018) and Phanerozoic detrital grains from Armstrong et al. (2022). New ZHe analyses (n = 21) confirm increasing visual metamictization corresponds with increasing eU concentration and dates fall along previously reported ZHe date-eU trends for each sample, despite grain selection by different analysts in different sessions. Raman-based alpha dose calculations from multiple spot analyses from transects across the surface and interior of each grain (n = 480 total analyses) range from 3.19 × 1016 to 1.52 × 1019 α/g across the whole dataset. Alpha dose increases in samples characterized by a clear increase in visual metamictization from different types of ZHe date-eU patterns, supporting that visual metamictization reflects effective radiation damage in these samples. Complexities in visual metamictization-damage trends are due to damage zonation observed in cathodoluminescence, comparative internal and external spot analyses, and 2-D Raman maps, as well as limited spread in intrasample visual metamictization and user grain selection bias. Overall, visual metamictization provides a qualitative estimate of effective damage and should be leveraged when selecting grains for traditional ZHe analyses to build ZHe date-eU-damage patterns.

Neutrons and swift heavy ions irradiation induced damage in SiC single crystal

Radiation damage induced in SiC single crystal by neutrons and sequentially neutrons + 91.3 MeV Xe ions irradiations were characterised by optical measurements (absorption and photoluminescence) and Raman spectroscopy. The samples were first irradiated with neutrons then followed by irradiation with 91.3 MeV Xe ions. Our aim is to check electronic ionization-induced pre-existing defects annealing in SiC single crystal. The data obtained for samples irradiated by neutrons were compared to those of neutrons + ions. It is found that neutrons irradiation induced absorption band at 780 nm and two emission bands at 550 nm and 920 nm. Both bands 780 nm and 920 nm assigned to silicon vacancy (VSi). Compared to neutrons irradiation, the same absorption and emission bands are observed for neutron + ions irradiated samples, indicating similar types of defects formation by additional 91.3 MeV Xe ions. The bands growth rapid at low dose followed by a saturation effect above a dose of 2.0 × 10−4 dpa for neutrons and 10.6 × 10−3 dpa for neutrons + ions. The stress follows the same dose-dependence as the absorption band, suggesting a good correlation between the stress and the silicon vacancies (VSi). Raman results proved that additional 91.3 MeV Xe ions irradiation induced the pre-existing damage annealing in SiC crystal. However, at high pre-existing defects concentration and Xe ions dose a competition between defects creation and annealing takes place. To confirm the results experiments using Doppler Broadened Emission Spectroscopy (DBS) using Variable Energy Slow Positron Beam, are planned for our next study.

A zircon classification scheme for sedimentary provenance analysis using radiation damage

Detrital single‐grain zircon U–Pb geochronology is a powerful tool for provenance studies if information on the source rocks is available. This paper proposes a new source‐rock classification tool that uses the degree of annealing of radiation damage in detrital zircon; the annealing is expressed by the relationship between the width (full‐width at half‐maximum; FWHM) of the v3[SiO4] Raman band at ~1008 cm−1 and the calculated α‐dose. The host rocks of the zircons are classified into three types according to their emplacement process and/or thermal history: volcanic and rapidly cooled plutonic and high‐grade metamorphic rocks (type 1); rocks with hydrothermal zircons (type 2); slowly cooled igneous and metamorphic rocks (type 3). We construct a naive Bayes prediction model by training it with a collection of zircons of known types. The unknown zircons are assigned a probability of derivation from a specific host‐rock type. This classification scheme is best used as an accessory tool in provenance studies that apply detrital zircon U–Pb geochronology.

Ion-Beam Surface Modification of Carbon Fibers

Carbon fibers are used in the production of automobiles, airplanes, sporting goods, energy, and biomedicine due to their unique properties such as high specific strength, high specific tensile strength, low coefficient of thermal expansion, and low density. The research and development of both the technology of carbon fibers production and their modification for a wide range of applications have been and remain relevant. The summary of the accumulated experience in the modification of carbon fibers shows that ion-beam treatment allows to obtain a variety of geometry of the developed surface topography, in particular, whisker-shaped and corrugated oriented across or along the fiber. Such processing compares favorably with ordinary fiber whiskering both by a variety of geometry of the composite interface, and by the absence of the problem of whisker-fiber adhesion. Ion-beam treatment also makes it possible to modify the surface layer structure from amorphized to ordered with different degrees of graphitization. Irradiation with chemically active ions leads to functionalization of carbon fiber due to formation, for example, of nitrides and carbon oxides. The choice of nitrogen ions for the technology of carbon-carbon and carbon-ceramic composites seems to be more preferable due to less stringent requirements for the temperature of the irradiated fiber. For ion-beam corrugation of polyacrylonitrile-based carbon fiber surface, only its heating above the temperature of dynamic annealing of radiation damage is required. The use of helium ions in technological plasma acceleration systems leads to a significant efficiency increase in ion-beam processing.

Reliability of petrogenetic information obtained from the distribution of trace elements in zircon in light of the complex infusion by foreign-element-bearing low temperature solutions

The increasing application of minor elements such as REE, Ti, Fe in zircon as petrogenetic indicators depends on zircon remaining a closed chemical system over a history that can include metamorphic events, erosion, transport, and sedimentation. Whereas examples have been described of UPb loss and element exchange during metamorphic reactions, for over 50 years there have been reports of the accumulation of a range of non-formula elements such as Ca, Al, Fe, in zircons with no metamorphic history that have been tentatively related to hydrothermal action or some other process such as weathering. This open system behaviour of zircons needs further explanation and in this contribution we present data from three zircons from a late Archaean granite from Western Australia that confirm previous observations on the distribution of non-formula elements in radiation damaged zircon and support our earlier conclusion that elements are added from percolating low temperature weathering solutions and provide new insights into the mechanisms and processes controlling access of weathering fluids into the zircon. These include radiation damage accumulation over time from the decay of U and Th to produce domains of porous amorphous material that vary in porosity and the presence of weaknesses along the boundaries of oscillatory zones which allow the penetration of low temperature groundwater fluids carrying solute elements. Also important is the size of particles of the solute elements such as Al and Ca, which depends on Eh - pH of the groundwater and porous domains within the zircon structure. This low temperature fluid interaction is distinguished from hydrothermal activity by a lack of any reaction fronts or annealing of the radiation damage and a lack of any modification of existing zircon structures. Capillary action is proposed as the mechanism driving the penetration of weathering solutions into radiation damage expansion fractures and the radiation damaged zonal structure. The susceptibility of radiation damaged zircon to infusion by low temperature fluids and deposition of accompanying solute elements has implications for the application of zircon trace element chemistry as a petrogenetic and temperature indicator as well as a geochronometer and host for nuclear waste.

Temperature dependence of radiation damage annealing of Silicon Photomultipliers

The last decade has increasingly seen the use of silicon photomultipliers (SiPMs) instead of photomultiplier tubes (PMTs). This is due to various advantages of the former on the latter like its smaller size, lower operating voltage, higher detection efficiency, insensitivity to magnetic fields and mechanical robustness to launch vibrations. All these features make SiPMs ideal for use on space based experiments where the detectors require to be compact, lightweight and capable of surviving launch conditions. A downside with the use of this novel type of detector in space conditions is its susceptibility to radiation damage. In order to understand the lifetime of SiPMs in space, both the damage sustained due to radiation as well as the subsequent recovery, or annealing, from this damage have to be studied. Here we present these studies for three different types of SiPMs from the Hamamatsu S13360 series. Both their behaviour after sustaining radiation equivalent to 2 years in low earth orbit in a typical mission is presented, as well as the recovery of these detectors while stored in different conditions. The storage conditions varied in temperature as well as in operating voltage. The study found that the annealing depends significantly on the temperature of the detectors with those stored at high temperatures recovering significantly faster and at recovering closer to the original performance. Additionally, no significant effect from a reasonable bias voltage on the annealing was observed. Finally the annealing rate as a function of temperature is presented along with various operating strategies for the future SiPM based astrophysical detector POLAR-2 as well as for future SiPM based space borne missions.

Assessing the long-term low-temperature thermal evolution of the central Indian Bundelkhand craton with a complex apatite and zircon (U-Th)/He dataset

Modern approaches in low-temperature thermochronometry are capable of extracting long-term thermal histories from cratonic settings that may elucidate potential drivers of deep-time phases of intracontinental burial and erosion. Here, we assess the utilization of the Radiation Damage Accumulation and Annealing Model for apatite (RDAAM) and zircon (ZRDAAM) to track the long-term low-temperature thermal evolution of the Archean Bundelkhand craton and the surrounding undeformed strata of the ∼1.7–0.9 Ga Vindhyan successions in central India. We correspondingly interpret a complex basement and detrital zircon and apatite (U-Th)/He (ZHe and AHe, respectively) dataset in light of observed model limitations and known geologic context. ZHe and AHe dates from across the craton reveal a significant (>300 Myr) date inversion between the two systems within grains with moderate to high effective uranium (eU) concentrations. Inverse thermal models utilizing current ZRDAAM and RDAAM parameters are not capable of reproducing observed coupled basement ZHe and AHe data for the same thermal history. However, meaningful thermal information can be extracted from AHe inverse models coupled with a forward modeling approach applied to detrital ZHe data from Vindhyan deposits, which have notably lower eU concentrations and yield significantly older ZHe dates (between ∼1,475 and 575 Ma) than basement zircon. Resulting thermal models indicate that the Bundelkhand craton experienced peak burial temperatures of ∼150°C between 850 and 475 Ma, followed by a major crustal cooling event at ∼350–310 Ma, possibly driven by late Paleozoic glaciations and/or epeirorogenic uplift. Inverse models including AHe data require a Deccan Traps related thermal perturbation between ∼66 and 65 Ma, and we suspect that this event overprinted basement zircon with moderate to high eU concentrations. Although the effects of zonation, grain morphology, and/or uncertainties in damage-annealing parameters contribute to disparities between predicted and observed AHe and ZHe dates, these factors alone cannot account for the major ZHe and AHe date inversion observed from the Bundelkhand craton. Instead, it is likely the case that current damage-dependent models for ⁴He diffusion are not adequately calibrated at the resolution necessary to predict short-lived thermal perturbations that occurred in a late phase relative to a prolonged period of extensive damage accumulation.

Investigating apatite (U-Th)/He thermochronologic ages to understand exhumation history of the Ethiopian Plateau

Although the Ethiopian Plateau is a prominent feature in East Africa, its exhumation history is not well constrained. For the last few decades, this history has been a topic of scientific interest due to the plateau's complicated geologic setting and thermal response to surface topographic changes. Studies of the plateau's thermal history have the potential to cast light on the numerous tectonic and geodynamic events that have affected the region since the beginning of the Mesozoic, such as Gondwana rifting, Afar mantle plume upwelling, continental flood basalt emplacement, Cenozoic continental rifting, and shield and cinder cone volcanism that has continued until the present day. We present new single-grain apatite (U-Th)/He (AHe) thermochronologic cooling ages from the Blue Nile Canyon to address the Ethiopian Plateau's exhumation history. AHe dates of 55 grains from nine Neoproterozoic basement and Mesozoic sedimentary rock samples, collected from a vertical transect of the Blue Nile Canyon, range from 58.9 ± 2.7 to 460.2 ± 34.7 Ma. Interpretation of these cooling ages is complex due to intra-sample age dispersion. We address this dispersion by systematically evaluating the ages based on standard deviation percentage, effective Uranium concentration [eU], and equivalent spherical grain radius r, which also helps select samples to generate a geologically meaningful thermal history model. Our inverse thermal history model using the Radiation Damage Accumulation and Annealing Model (RDAAM) reveals a protracted Paleozoic cooling, a gradual reheating during Permo-Mesozoic time (between ∼300 and ∼100 Ma), and a rapid cooling in the Cretaceous (∼100 Ma). This Paleozoic and Mesozoic thermal history reflects post-Pan-African orogenic denudation followed by Gondwana rift-related burial and then exhumation. A period of tectonic quiescence is reflected between ∼100 and ∼30 Ma, during which there was little to no cooling. Although our thermal model shows burial-related reheating after the flood basalt emplacement around 30 Ma and eventual cooling to present-day surface temperature, our thermochronologic data likely lack sufficient resolution to determine the details of the Neogene cooling related to incision of the Blue Nile Canyon. Our study suggests that the thermal history of the Ethiopian Plateau is dynamic and warrants further high-resolution, low-temperature thermochronologic investigation to constrain post-30 Ma river incision of the plateau.

Monolithic Perovskite/Silicon Tandem Solar Cells Fabricated Using Industrial p‐Type Polycrystalline Silicon on Oxide/Passivated Emitter and Rear Cell Silicon Bottom Cell Technology

Combining a perovskite top cell with a conventional passivated emitter and rear cell (PERC) silicon bottom cell in a monolithically integrated tandem device is an economically attractive solution to boost the power conversion efficiency (PCE) of silicon single‐junction technology. Proof‐of‐concept perovskite/silicon tandem solar cells using high‐temperature stable bottom cells featuring a polycrystalline silicon on oxide (POLO) front junction and a PERC‐type passivated rear side with local aluminum‐p+contacts are reported. For this PERC/POLO cell, a process flow that is compatible with industrial, mainstream PERC technology is implemented. Top and bottom cells are connected via a tin‐doped indium oxide recombination layer. The recombination layer formation on the POLO front junction of the bottom cell is optimized by postdeposition annealing and mitigation of sputter damage. The perovskite top cell is monolithically integrated in a p−i−n junction device architecture. Proof‐of‐concept tandem cells demonstrate a PCE of up to 21.3%. Based on the experimental findings and supporting optical simulations, major performance enhancements by process and layer optimization are identified and a PCE potential of 29.5% for these perovskite/silicon tandem solar cells with PERC‐like bottom cell technology is estimated.

Multi‐Band Raman Analysis of Radiation Damage in Zircon for Thermochronology: Partial Annealing and Mixed Signals

AbstractFour zircon Raman bands were previously calibrated to give consistent estimates of the accumulated self‐irradiation α‐dose in unannealed volcanic samples. Partial annealing of radiation damage produces inconsistent values because of differences in the relative annealing sensitivities. The damage estimates based on the external rotation band (DER) at ∼356 cm−1 and that based on the ν2(SiO4) band (D2) at ∼438 cm−1 are the most and least sensitive to damage annealing. The D2/DER‐ratio thus provides a numerical estimate of the extent of geologic annealing that a zircon sample has experienced. This ratio characterizes the thermal history of a zircon sample but also its state of radiation damage during the course of its geologic history, and thus the manner in which this state influences other thermochronologic methods. Meaningful interpretation of the zircon Raman age requires that the spectra are free of measurement artifacts. The major artifacts result from micrometer‐scale gradients of the damage densities within a zircon grain due to uranium and thorium zoning. The micrometer‐sized sampled volume may span different densities, producing overlapping spectra, causing apparent peak broadening, overestimated damage densities, and zircon Raman ages. The D3/D2‐ratio of the damage densities calculated from the ν3(SiO4) and ν2(SiO4) bands, most and least affected by overlap, is an efficient indicator of a meaningless signal. It reveals overlap in annealed and unannealed samples, because the used bands have similar responses to annealing. Multi‐band Raman maps can be converted to damage‐ratio maps for screening zircon mounts, and selecting spots for thermochronologic investigations.

Prismatic edge dislocations in graphite

Dislocations are a central concept in materials science, which dictate the plastic deformation and damage evolution in materials. Layered materials such as graphite admit two general types of interlayer dislocations: basal and prismatic dislocations, of which prismatic dislocations have been relatively less studied. Using density functional theory (DFT) calculations, we have examined different prismatic core structures in graphite and evaluated their structure, energetics and mobility. We find close energetic interplay between bonded and “free-standing” core structures in both zigzag and armchair directions, with a reconstructed stable zigzag core identified. We explore grain boundaries and prismatic dislocation pile-up, identifying metastable structures which may be important in energy storage. The role of interlayer stacking in core structure, dislocation glide and climb is also considered in-depth. Our calculations suggest that the prismatic dislocation core is stable up to high temperatures of approximately 1500 K in bulk graphite. Above this temperature, the breaking of bonds in the dislocation core can facilitate climb, grain-boundary motion, and the annealing of damage through prismatic dislocation glide.

Zircon (U-Th)/He thermochronology of Grand Canyon resolves 1250 Ma unroofing at the Great Unconformity and <20 Ma canyon carving

Abstract Our study used zircon (U-Th)/He (ZHe) thermochronology to resolve cooling events of Precambrian basement below the Great Unconformity surface in the eastern Grand Canyon, United States. We combined new ZHe data with previous thermochronometric results to model the <250 °C thermal history of Precambrian basement over the past >1 Ga. Inverse models of ZHe date-effective uranium (eU) concentration, a relative measure of radiation damage that influences closure temperature, utilize He diffusion and damage annealing and suggest that the main phase of Precambrian cooling to <200 °C was between 1300 and 1250 Ma. This result agrees with mica and potassium feldspar 40Ar/39Ar thermochronology showing rapid post–1400 Ma cooling, and both are consistent with the 1255 Ma depositional age for the Unkar Group. At the young end of the timescale, our data and models are also highly sensitive to late-stage reheating due to burial beneath ∼3–4 km of Phanerozoic strata prior to ca. 60 Ma; models that best match observed date-eU trends show maximum temperatures of 140–160 °C, in agreement with apatite (U-Th)/He and fission-track data. Inverse models also support multi-stage Cenozoic cooling, with post–20 Ma cooling from ∼80 to 20 °C reflecting partial carving of the eastern Grand Canyon, and late rapid cooling indicated by 3–7 Ma ZHe dates over a wide range of high eU. Our ZHe data resolve major basement exhumation below the Great Unconformity during the Mesoproterozoic (1300–1250 Ma), and “young” (20–0 Ma) carving of Grand Canyon, but show little sensitivity to Neoproterozoic and Cambrian basement unroofing components of the composite Great Unconformity.

Recovery of ion-damaged 4H-SiC under thermal and ion beam-induced ultrafast thermal spike-assisted annealing

The recovery effect of isochronal thermal annealing and inelastic energy deposited during 100 MeV Ag swift heavy ion (SHI) irradiation is demonstrated in the case of 4H-SiC pre-damaged by elastic energy deposition of 300 keV Ar ion. The Ar-induced fractional disorder follows a nonlinear two-step damage build-up. The fractional disorder level of 0.3 displacements per atom (dpa) is established as the threshold above which the lattice rapidly enters the amorphous phase, characterized by the presence of highly photo-absorbing defects. The SHI-induced recovery suggests that the damage annealing, in the pre-damaged region (∼350 nm) where the Se for 100 MeV Ag is almost constant (∼16.21 keV/nm), is more pronounced than the damage creation by SHI. This allows the disorder values to saturate at a lower value than the present initial disorder. Furthermore, the thermal effect due to SHI irradiation of an amorphous nano-zone embedded in a crystalline host matrix has been evaluated using the 3D implementation of the thermal spike. The recovery process by SHI is ascribed to the thermal spike-induced atomic movements resulting from the melting and the resolidification of the crystalline–amorphous interface.

Late Oligocene–Early Miocene Detachment Faulting in Crystalline Basement, Mecca Hills, CA, Documented With Zircon (U–Th)/He Date‐eU‐Visual Radiation Damage Patterns

AbstractZircon (U–Th)/He (zircon He) thermochronometry and visual radiation damage relationships reveal the timing and patterns of Orocopia Schist and North American basement exhumation in the Mecca Hills, CA. Zircon crystals from these units were selected to maximize the spectrum in visual metamictization and effective U (eU) concentrations, and thus He retentivity, in each sample. Zircon He dates (n = 31 analyses) from six of seven samples are ∼24 Ma regardless of eU, despite a large spread in eU (>2,800 ppm) across all grains. One sample (n = 7 analyses) yields a mean ∼65 Ma date. Uniform zircon He dates over a range of eU concentrations and their preserved visual metamictization indicate these grains experienced a thermal history that induced complete He loss, but did not anneal the damage. This is consistent with recent work that indicates zircon radiation damage anneals at higher temperatures than parameterized in current damage annealing models. The zircon He data patterns, together with new zircon U‐Pb results and thermal history modeling, reveal the two basement units in the Mecca Hills exhumed simultaneously at ∼24 Ma, likely by the Orocopia Mountains detachment fault. This requires both basement units lie in the footwall of the detachment, and implies the breakaway zone of the Orocopia Mountains detachment fault was west of the present‐day Mecca Hills basement exposures and has been translated by the San Andreas fault. Combined with prior work, our data suggest large‐magnitude late Oligocene–early Miocene extension in the southwestern Cordillera was more widespread than previously recognized.

Apatite (U-Th)/He thermochronometric constraints on the northern extent of the Deccan large igneous province

The volcanic emplacement and subsequent weathering of the Deccan Traps of India is believed to have had a significant influence in driving global climatic shifts from the Late Cretaceous and through the Cenozoic. The magnitude of the Deccan Traps' impact on Earth's surface environment is largely dependent on the speculated original footprint of the large igneous province. To test established estimates for the pre-erosive northern extent of the Deccan Traps, we applied low-temperature apatite (U-Th)/He thermochronology (AHe) on rocks from the Bundelkhand craton and overlying Proterozoic Vindhyan successions of central India ∼150–200 km northeast of the northernmost preservation of Deccan basalts. New AHe data reveal young ∼5–85 Ma AHe dates with low effective uranium concentrations (eU) between 5–22 ppm, with a steep positive date-eU correlation that plateaus at ∼350 Ma in grains with eU values >50 ppm. Inverse thermal history modeling—utilizing AHe diffusion parameters of the Radiation Damage Accumulation and Annealing Model (RDAAM)—indicate that observed AHe date-eU correlations are most consistent with thermal histories that require the craton and Vindhyan strata to be at or near surface temperatures by ∼66 Ma, followed by a discrete reheating event associated with Deccan volcanism. These results establish new minimal areal constraints for the northern extent of Deccan volcanism which thermally perturbed much of the Vindhyan succession. Thermal alteration of organic rich Vindhyan sediment may have provided an additional source of volatile emissions that facilitated late Maastrichtian warming at the onset of Deccan volcanism. New minimal northern constraints on Deccan volcanism additionally confirm that large volumes of Deccan basalts have been stripped away since the time of their emplacement, which poses considerable implications for unraveling their role in Cenozoic cooling.

Diffusion of strontium implanted in glassy carbon

Glassy carbon has properties making it attractive as a containment material for radioactive waste. In this study, the diffusivity of the radiological important fission product, strontium, is measured. Two hundred kiloelectronvolt strontium ions were implanted at room temperature. The implanted samples were either annealed isochronally for 1 h up to 900°C or by increasing the temperature linearly up to 648°C. The Sr profiles were determined by Rutherford backscattering spectrometry (RBS). The isochronally annealed samples showed Fickian diffusion at 300°C ( D = 6.7 × 10 −19 m 2 s −1 ) with segregation occurring at the higher temperatures. Raman spectroscopy indicated a link between damage annealing and the onset of segregation. During increasing temperature, the system is dynamic with diffusion taking place. An equation to determine diffusion coefficients for ramped heating was derived. Fickian diffusion occurred with an activation energy of 1.97 eV for 414–454°C, and from 458 to 558°C, it was 0.184 eV. At higher temperatures, a segregation of the strontium towards the surface was observed. A calculation of the heat of segregation of Sr in carbon supports this segregation. The results show that the in situ RBS measurements with a linear increase in temperature give additional information compared with the conventional isochronal annealing.

He beam annealing and self-healing of Kr implanted BaWO4 at low temperature

Damage formation in 370 keV Kr ion-implanted BaWO4 is investigated with Rutherford backscattering spectrometry in channeling mode (RBS/C), performed in a quasi-in situ modus at a cryogenic temperature of 16 K. The obtained results are compared to those for similar experiments done previously at room temperature. The significant differences observed for ion implantation into BaWO4 at these two temperatures can be explained by the mobility of WO3 impurities. Other authors found WO3 to become mobile at temperatures above 240 K. This defect mobility can further account for the strong damage annealing occurring during warming implanted samples from 16 K to room temperature. In this temperature range, only completely amorphized layers remain stable. However, these layers transform into much less damaged layers exhibiting a strong crystalline long-range order during storage at room temperature with time, revealing a kind of self-healing. Another very important finding is the strong damage annealing due to the analyzing He ions during the RBS/C analysis both at 16 K and at room temperature. The analyzing He ions deposit their energy mainly in the electronic system of the target atoms. By applying an analytical thermal spike model, it is shown that the local temperature increase along the trajectory of the analyzing He ions could be responsible for observed damage annealing. The high susceptibility to energy deposition in electronic processes may have implications for any analysis based on energetic electrons. BaWO4 reveals a high radiation resistance at room temperature, which may be relevant for practical application.