Latent Fission Tracks

Damaged regions of cylindrical shapes called ion tracks, typically in nano-meters wide and tens micro-meters long, are formed along the ion trajectories in many insulators, when high energy ions in the electronic stopping regime are injected. In most cases, the ion tracks were assumed as consequences of dense electronic energy deposition from the high energy ions, except some cases where the synergy effect with the nuclear energy deposition plays an important role. In crystalline Si (c-Si), no tracks have been observed with any monomer ions up to GeV. Tracks are formed in c-Si under 40 MeV fullerene (C60) cluster ion irradiation, which provides much higher energy deposition than monomer ions. The track diameter decreases with decreasing the ion energy until they disappear at an extrapolated value of ~ 17 MeV. However, here we report the track formation of 10 nm in diameter under C60 ion irradiation of 6 MeV, i.e., much lower than the extrapolated threshold. The diameters of 10 nm we...

Based on the Coulomb-spike model, track formation is expected to depend on the electrical resistivity of a given material. Here, we report the first systematic study on ion tracks in doped SrTiO 3 (STO) [1]. With the addition of low concentrations of Nb the resistivity of STO dramatically decreases covering the entire electronic regime from an insulating to conducting material.

As part of a Play Fairway Analysis (PFA) of the Scotian Margin, offshore eastern Canada, quantitative multidisciplinary biostratigraphic studies of Upper Triassic-Cenozoic sections in 8 wells (Bonnet P-23, Chebucto K-90, Cohasset L-97, Glenelg J-48, Glooscap C-63, Mohican H-100, South Debarres O-76, and South Griffin J-13), was conducted. These wells were chosen to provide good spatial A revised biostratigraphic and well-log sequence stratigraphic framework for the Scotian Margin, offshore eastern Canada

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The search for and identification of energetic nuclei of superheavy elements of cosmic rays in olivine crystals from meteorites, currently performed within the Olympia project [1], are based on measurements of dynamic and geometrical parameters of tracks, i.e., chemically etchable regions of the traces of slowing down of these nuclei before their stop, using the fully automated PAVIKOM measuring system [2].

We have studied the morphology and annealing kinetics of ion tracks in Durango apatite using synchrotron small angle X-ray scattering. The non-destructive, artefact-free technique enables us to determine the track radii with a resolution of fractions of a nanometre. The tracks were generated using different heavy ions with energies between 185 MeV and 2.6 GeV. The track morphology is consistent with the formation of long cylindrical amorphous tracks. The annealing kinetics, measured by SAXS in combination with ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallisation of the damaged material. The measurement methodology shown here provides a new means for in-depth studies of ion-track formation in minerals under a wide variety of geological conditions. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2 0 , which. permits unrestricted use, distributi and reproduction in any medium, provided the original work is properly cited. on,

The structure and thermal response of amorphous ion tracks formed along the [112¯0], [101¯0], and [0001]-directions in crystalline quartz have been investigated using small angle x-ray scattering. The radii of the ion tracks vary by about 5% (0.3 nm) for tracks along different crystallographic directions. Molecular dynamics simulations reproduce this anisotropy along the [101¯0] and [0001] directions and suggest that differences in thermal conductivity along these directions are partly responsible for this observation. Using in situ annealing, tracks along the [101¯0] and [0001] directions were shown to recrystallize during thermal annealing around 960–1020 °C with activations energies around 6 eV, while those along the [112¯0]-direction already disappeared at 640 °C with a significantly lower activation energy around 3–4 eV.

Ion tracks in amorphous Fe 80 B 20 , produced by irradiation with 11.1 MeV/u Au ions, were characterized using synchrotron based small angle X-ray scattering. The tracks resemble long cylindrical structures with a radius of 8.2 ± 0.1 nm. Annealing experiments reveal an activation energy for track recovery E a = 0.39 ± 0.10 eV. Wide angle X-ray scattering measurements of irradiated and unirradiated amorphous Fe 80 B 20 samples indicate enhanced recrystallization for the irradiated material.

Investigation of the ion track morphologies and track etching behaviour in polycarbonate (PC) films was carried out using synchrotron based small-angle x-ray scattering (SAXS) measurements. The tracks were induced by Au ions with kinetic energies of 1.7 and 2.2 GeV with applied fluences between 1×10 10 and 1×10 12 ions /cm 2. The average radii of the un-etched tracks were studied as a function of the irradiation fluence, indicating a general ion induced degradation of the polymer with a simultaneous increase in ion track radius from 2.6±0.02 nm to 3.4±0.3 nm. Chemical etching of the ion tracks in PC leads to the formation of cylindrical pores. The pore radius increases linearly with etching time. In 3 M NaOH at 55º C, a radial etching rate of 9.2 nm/min is observed.

Natural apatite samples were irradiated with 185 MeV Au and 2.3 GeV Bi ions to simulate fission tracks. The resulting track morphology was investigated using synchrotron small angle x-ray scattering (SAXS) measurements before and after chemical etching. We present preliminary results from the SAXS measurement showing the etching process is highly anisotropic yielding faceted etch pits with a 6-fold symmetry. The measurements are a first step in gaining new insights into the correlation between etched and unetched fission tracks and the use of SAXS as a tool for studying etched tracks.

revealed by chemical etching, because, until now, unetched, latent FTs could not be examined analytically at the atomic-scale. The major challenge to such an analysis has been the random orientation of FTs and their extremely small diameters. Here we use high-energy ions (2.2 GeV Au or 80 MeV transmission electron microscopy (TEM) of single tracks and small-angle X-ray scattering (SAXS) for millions of tracks, a precise picture of track morphology as a function of orientation is obtained. High-resolution analysis reveals that orientation affects the shape of tracks in apatite and zircon through the preferential creation of damage along directions with highest atomic density. However, track radius does not depend on orientation, contradicting previous reports. Independent of track orientation, track radii, as measured at each point along the entire length of 80 MeV Xe ion tracks in apatite, can be understood using the thermal spike model of Szenes. Thus, the well-known track annealing anisotropy of apatite is not due to track radius anisotropy. The combination of ion-irradiations with TEM and SAXS analysis provides a unique opportunity to understand and model track formation and annealing under various geologic conditions.

Based on the Coulomb-spike model, track formation is expected to depend on the electrical resistivity of a given material. Here, we report the first systematic study on ion tracks in doped SrTiO 3 (STO) [1]. With the addition of low concentrations of Nb the resistivity of STO dramatically decreases covering the entire electronic regime from an insulating to conducting material.

A major issue in thermochronology and U-Th-Pb dating is the effect of radiation damage, created by α-recoils from α-decay events, on the diffusion of radiogenic elements (e.g., He and Pb) in host mineral. Up until now, thermal events have been considered as the only source of energy for the recovery of radiation-damage. However, irradiation, such as from the α-particle of the α-decay event, can itself induce damage recovery. Quantification of radiation-induced recovery caused by α-particles during α-decay events has not been possible, as the recovery process at the atomic-scale has been difficult to observe. Here we present details of the dynamics of the amorphous-to-crystalline transition process during α-particle irradiations using in situ transmission electron microscopy (TEM) and consecutive ion-irradiations: 1 MeV Kr(2+) (simulating α-recoil damage), followed by 400 keV He(+) (simulating α-particle annealing). Upon the He(+) irradiation, partial recrystallization of the origina...

Tracks created by fission events in ceramics are randomly-oriented, linear radiation-damage regions about 10 to 25 μm in length but only several nm in diameter. In the absence of a method to observe the entire length of a latent, unetched track, the details of the structure and the process of the thermal-annealing of tracks have remained elusive, despite their importance to fission track thermochronology and radiation damage studies in nuclear materials. Here, we have used a novel sample preparation technique, together with advanced transmission electron microscopy (TEM), to successfully image the entire length and in situ thermal annealing of latent tracks created by 80 MeV Xe ions implanted in apatite. Track annealing significantly increases as the track diameter decreases along the ion trajectory from an initial diameter of 8.9 nm tõ 1.5 nm at the end of the track (total track length~8.1 μm). For the first time, the initial, rapid reduction in etched length during isothermal annealing can be essentially explained by the rapid annealing of the sections of the track with smaller diameters, as observed directly by TEM.

Ion tracks are narrow cylindrical defects of displaced atoms, a few nanometres in diameter and up to tens of micrometres in length. They result from the interaction of high-energy heavy ions with the electrons of a target material. We have performed a systematic investigation of the effects of the temperature during track formation in natural quartz samples, using synchrotron-based small angle x-ray scattering (SAXS). SAXS is a powerful and non-destructive technique well suited to measure ion track radii with high precision [1]. Natural quartz samples were irradiated at the UNILAC accelerator with 2.2-GeV Au ions and a fluence of 5 10 ions/cm. This leads to the formation of ion tracks of ~95 μm length, as estimated by SRIM2008 [2]. The irradiation was carried out at room-temperature (RT) as well as at elevated temperatures. The quartz was cut parallel to the c-axis, thus leading to a track alignment perpendicular to the crystal’s c-axis. Reference samples, irradiated at RT, underwen...

The thermal response of nanoscale cylindrical inclusions of amorphous SiO 2 embedded in crystalline quartz (c-SiO 2) is investigated by means of small-angle x-ray scattering. The inclusions are generated by swift heavy-ion irradiation that leads to the formation of amorphous ion tracks along the ion trajectories. During in situ annealing between room temperature and 620°C, we observe an irreversible expansion of the track cylinders followed by a reversible contraction. The reversible "elastic" response of the tracks can be modeled using the temperature-dependent elastic properties of bulk amorphous and crystalline SiO 2 for the inclusions and the matrix, respectively. A high initial interface pressure of the nanocylinders is apparent from the calculations.

revealed by chemical etching, because, until now, unetched, latent FTs could not be examined analytically at the atomic-scale. The major challenge to such an analysis has been the random orientation of FTs and their extremely small diameters. Here we use high-energy ions (2.2 GeV Au or 80 MeV transmission electron microscopy (TEM) of single tracks and small-angle X-ray scattering (SAXS) for millions of tracks, a precise picture of track morphology as a function of orientation is obtained. High-resolution analysis reveals that orientation affects the shape of tracks in apatite and zircon through the preferential creation of damage along directions with highest atomic density. However, track radius does not depend on orientation, contradicting previous reports. Independent of track orientation, track radii, as measured at each point along the entire length of 80 MeV Xe ion tracks in apatite, can be understood using the thermal spike model of Szenes. Thus, the well-known track annealing anisotropy of apatite is not due to track radius anisotropy. The combination of ion-irradiations with TEM and SAXS analysis provides a unique opportunity to understand and model track formation and annealing under various geologic conditions.

Ion tracks are narrow cylindrical defects of displaced atoms, a few nanometres in diameter and up to tens of micrometres in length. They result from the interaction of high-energy heavy ions with the electrons of a target material. We have performed a systematic investigation of the effects of the temperature during track formation in natural quartz samples, using synchrotron-based small angle x-ray scattering (SAXS). SAXS is a powerful and non-destructive technique well suited to measure ion track radii with high precision [1]. Natural quartz samples were irradiated at the UNILAC accelerator with 2.2-GeV Au ions and a fluence of 5 10 ions/cm. This leads to the formation of ion tracks of ~95 μm length, as estimated by SRIM2008 [2]. The irradiation was carried out at room-temperature (RT) as well as at elevated temperatures. The quartz was cut parallel to the c-axis, thus leading to a track alignment perpendicular to the crystal’s c-axis. Reference samples, irradiated at RT, underwen...

We have studied the morphology and annealing kinetics of ion tracks in Durango apatite using synchrotron small angle X-ray scattering. The non-destructive, artefact-free technique enables us to determine the track radii with a resolution of fractions of a nanometre. The tracks were generated using different heavy ions with energies between 185 MeV and 2.6 GeV. The track morphology is consistent with the formation of long cylindrical amorphous tracks. The annealing kinetics, measured by SAXS in combination with ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallisation of the damaged material. The measurement methodology shown here provides a new means for in-depth studies of ion-track formation in minerals under a wide variety of geological conditions. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2 0 , which. permits unrestricted use, distributi and reproduction in any medium, provided the original work is properly cited. on,

The thermal response of nanoscale cylindrical inclusions of amorphous SiO 2 embedded in crystalline quartz (c-SiO 2) is investigated by means of small-angle x-ray scattering. The inclusions are generated by swift heavy-ion irradiation that leads to the formation of amorphous ion tracks along the ion trajectories. During in situ annealing between room temperature and 620°C, we observe an irreversible expansion of the track cylinders followed by a reversible contraction. The reversible "elastic" response of the tracks can be modeled using the temperature-dependent elastic properties of bulk amorphous and crystalline SiO 2 for the inclusions and the matrix, respectively. A high initial interface pressure of the nanocylinders is apparent from the calculations.

Ion tracks were generated in crystalline San Carlos olivine (Mg,Fe) 2 SiO 4 and Durango apatite Ca 10 (PO 4) 6 F 2 using different heavy ions (58 Ni, 101 Ru, 129 Xe, 197 Au, and 238 U) with energies ranging between 185 MeV and 2.6 GeV. The tracks and their annealing behavior were studied by means of synchrotron based small angle X-ray scattering in combination with in situ annealing. Track radii vary as a function of electronic energy loss but are very similar in both minerals. Furthermore, the annealing behavior of the track radii has been investigated and preliminary results reveal a lower recovery rate of the damaged area in olivine compared with apatite.

revealed by chemical etching, because, until now, unetched, latent FTs could not be examined analytically at the atomic-scale. The major challenge to such an analysis has been the random orientation of FTs and their extremely small diameters. Here we use high-energy ions (2.2 GeV Au or 80 MeV transmission electron microscopy (TEM) of single tracks and small-angle X-ray scattering (SAXS) for millions of tracks, a precise picture of track morphology as a function of orientation is obtained. High-resolution analysis reveals that orientation affects the shape of tracks in apatite and zircon through the preferential creation of damage along directions with highest atomic density. However, track radius does not depend on orientation, contradicting previous reports. Independent of track orientation, track radii, as measured at each point along the entire length of 80 MeV Xe ion tracks in apatite, can be understood using the thermal spike model of Szenes. Thus, the well-known track annealing anisotropy of apatite is not due to track radius anisotropy. The combination of ion-irradiations with TEM and SAXS analysis provides a unique opportunity to understand and model track formation and annealing under various geologic conditions.

Ion tracks were created in olivine from San Carlos, Arizona (95% Mg 2 SiO 4), apatite (Ca 5 (PO4) 3 (F,Cl,O)) from Durango, Mexico, and synthetic silicates with the apatite structure: Nd 8 Sr 2 (SiO 4) 6 O 2 and Nd 8 Ca 2-(SiO 4) 6 O 2 using 1.6 and 2.2 GeV Au ions. The morphology and annealing behaviour of the tracks were investigated by means of synchrotron based small angle X-ray scattering in combination with ex situ annealing. Tracks in olivine annealed above $400°C undergo a significant change in track radius due to recrystallisation of the damage tracks. At temperatures higher than 620°C, the scattering images indicate fragmentation of the track cylinders into smaller subsections. Ion tracks were annealed at elevated temperatures up to 400°C in the Durango and Ca-britholite, and up to 560°C in Sr-britholite. While there was a significant change in the track radii in the Durango apatite, tracks in the two synthetic samples remained almost unchanged.

We have studied the morphology and annealing kinetics of ion tracks in Durango apatite using synchrotron small angle X-ray scattering. The non-destructive, artefact-free technique enables us to determine the track radii with a resolution of fractions of a nanometre. The tracks were generated using different heavy ions with energies between 185 MeV and 2.6 GeV. The track morphology is consistent with the formation of long cylindrical amorphous tracks. The annealing kinetics, measured by SAXS in combination with ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallisation of the damaged material. The measurement methodology shown here provides a new means for in-depth studies of ion-track formation in minerals under a wide variety of geological conditions. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2 0 , which. permits unrestricted use, distributi and reproduction in any medium, provided the original work is properly cited. on,

Small angle X-ray scattering measurements were performed on natural apatite of different thickness irradiated with 2.2 GeV Au swift heavy ions. The evolution of the track radius along the full ion track length was estimated by considering the electronic energy loss and the velocity of the ions. The shape of the track is nearly cylindrical, slightly widening with a maximum diameter approximately 30 lm before the ions come to rest, followed by a rapid narrowing towards the end within a cigar-like contour. Measurements of average ion track radii in samples of different thicknesses, i.e. containing different sections of the tracks are in good agreement with the shape estimate.

Based on the Coulomb-spike model, track formation is expected to depend on the electrical resistivity of a given material. Here, we report the first systematic study on ion tracks in doped SrTiO 3 (STO) [1]. With the addition of low concentrations of Nb the resistivity of STO dramatically decreases covering the entire electronic regime from an insulating to conducting material.

Ion tracks were generated in crystalline San Carlos olivine (Mg,Fe) 2 SiO 4 and Durango apatite Ca 10 (PO 4) 6 F 2 using different heavy ions (58 Ni, 101 Ru, 129 Xe, 197 Au, and 238 U) with energies ranging between 185 MeV and 2.6 GeV. The tracks and their annealing behavior were studied by means of synchrotron based small angle X-ray scattering in combination with in situ annealing. Track radii vary as a function of electronic energy loss but are very similar in both minerals. Furthermore, the annealing behavior of the track radii has been investigated and preliminary results reveal a lower recovery rate of the damaged area in olivine compared with apatite.

Ion tracks in amorphous Fe 80 B 20 , produced by irradiation with 11.1 MeV/u Au ions, were characterized using synchrotron based small angle X-ray scattering. The tracks resemble long cylindrical structures with a radius of 8.2 ± 0.1 nm. Annealing experiments reveal an activation energy for track recovery E a = 0.39 ± 0.10 eV. Wide angle X-ray scattering measurements of irradiated and unirradiated amorphous Fe 80 B 20 samples indicate enhanced recrystallization for the irradiated material.

Neodymium-doped yttrium aluminium garnet (Nd:Y 3 Al 5 O 12 or Nd:YAG) crystals were irradiated with 2.2 GeV 197 Au ions. Ion track formation was investigated using synchrotron based small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Cylindrical ion tracks consisted of an amorphous core with sharp boundaries within the crystalline matrix. The SAXS results, modelled as long cylindrical tracks, provided a constant track density that is 0.6 ± 0.3% different to that of the surrounding matrix. The average track radii determined by both techniques were in excellent agreement, 4.4 ± 0.1 nm from SAXS and 4.4 ± 0.5 nm from TEM. A comparison with previous results of ion tracks in YAG indicates that the track radius is not affected by the presence of 1 mol% Nd dopant.

Radial electron densities within 27-111 mm-long ion damage trails, 'latent ion tracks', created in {100} LiF by irradiation with GeV Pb and U projectiles, have been derived by means of small-angle X-ray scattering. The tracks exhibit continuous electron density decreases of 49-74% along the centers of their 2.3-3.4 nm-diameter cores. Structural alteration under the intense ion-deposited electronic excitation has been attributed to two successive processes: (a) local breakdown of the LiF lattice into fluorine molecules and Li atoms, and (b) release of the fluorine gas and of at least a portion of the voluminous Li atoms through the low-density tracks.

Radial electron densities within 27-111 mm-long ion damage trails, 'latent ion tracks', created in {100} LiF by irradiation with GeV Pb and U projectiles, have been derived by means of small-angle X-ray scattering. The tracks exhibit continuous electron density decreases of 49-74% along the centers of their 2.3-3.4 nm-diameter cores. Structural alteration under the intense ion-deposited electronic excitation has been attributed to two successive processes: (a) local breakdown of the LiF lattice into fluorine molecules and Li atoms, and (b) release of the fluorine gas and of at least a portion of the voluminous Li atoms through the low-density tracks. conference papers J. Appl. Cryst. (2007). 40, s121-s125 Abu Saleh and Eyal Core structure of latent heavy-ion tracks s125

A major issue in thermochronology and U-Th-Pb dating is the effect of radiation damage, created by α-recoils from α-decay events, on the diffusion of radiogenic elements (e.g., He and Pb) in host mineral. Up until now, thermal events have been considered as the only source of energy for the recovery of radiation-damage. However, irradiation, such as from the α-particle of the α-decay event, can itself induce damage recovery. Quantification of radiation-induced recovery caused by α-particles during α-decay events has not been possible, as the recovery process at the atomic-scale has been difficult to observe. Here we present details of the dynamics of the amorphous-to-crystalline transition process during α-particle irradiations using in situ transmission electron microscopy (TEM) and consecutive ion-irradiations: 1 MeV Kr(2+) (simulating α-recoil damage), followed by 400 keV He(+) (simulating α-particle annealing). Upon the He(+) irradiation, partial recrystallization of the origina...

ABSTRACT Forty apatite samples of sandstone from ten exploration wells in the Scotian Basin, offshore Nova Scotia, Canada, were used for fission track analysis and thermal history reconstruction. The sample depths range from 1000 to 5500 m. Fission tracks in all apatite samples are at least partially annealed. Apatite fission track ages for the shallowest samples, from the Logan Canyon Formation, are older than their stratigraphic ages and therefore retain some record of cooling in the detrital source area. Samples from deeper formations (Missisauga, Mic Mac and Verrill Canyon) have apatite fission track ages younger than their stratigraphic ages (some give zero ages), indicating partial to total annealing of fission tracks in apatite. The degree of annealing in most samples modelled is significantly higher than would be expected given their present-day temperatures. This indicates that these samples experienced a thermal overprint; they have been hotter in the past than at present. Inverse modelling by a Constrained Random Search (CRS) technique was carried out on the six best data sets. The results indicate that strata at depths of 1650-2600 m in the modelled wells were heated to paleotemperatures of about 80-110°C at some time during the interval 100-40 Ma. The magnitude of the thermal overprint predicted (estimated) by the modelling ranges from 1° to 55Cdeg; among the five wells modelled. Zircon fission track data from fifteen samples in four wells do not constrain burial temperatures. These data indicate a mixed provenance for the sediments. RESUME Quarante echantillons d'apatite de gres provenant de dix puits d'exploration du bassin Scotian, au large de la Nouvelle-Ecosse, au Canada, ont servi pour l'analyse des traces de fission et la reconstruction de l'evolution thermique. La profondeur des echantillons varie de 1 000 a 5 500 metres. Les traces de fission dans tous les echantillons d'apatite sont au moins partiellement recuites. Les ages des traces de fission d'apatite pour les echantillons les moins profonds, de la Formation Logan Canyon, sont anterieurs a leurs ages stratigraphiques et par consequent, conservent quelques temoignages du refroidissement dans les regions detritiques formatrices. Les echantillons provenant de formations plus profondes (Missisauga, Mic Mac et Verrill Canyon) donnent des traces de fission d'apatite plus jeunes que leurs ages stratigraphiques (quelques-uns donnent zero pour age), indiquant une recuisson partielle a complete des traces de fission d'apatite. Le degre de recuisson dans la plupart des echantillons modeles est significativement plus eleve qu'il ne serait attentu etant donne leurs temperatures contemporaines. Ceci indique que ces echantillons ont subi une superposition thermique d'empreintes; ils ont auparavant ete plus chauds. La modelage inverse par la technique Constrained Random Search (CRS) (recherche au hasard contrainte) a ete effectue sur les six meilleurs jeux de donnees. Les resultats indiquent que des couches a des profondeurs de 1650-2600 metres dans les puits modeles ont ete chauffes a des paleotemperatures de 80-110°C a une epoque durant l'intervalle de 100-40 Ma. L'ampleur de la superposition thermique d'empreintes prevue (estimee) par les ecarts de modelage de 1° a 55°C pour les cinq puits modeles. Les donnees de traces de fission de quinze echantillons de zircon de quatre puits ne contraignent pas les temperatures d'enfouissement. Ces donnees indiquent une provenance mixte des sediments. Traduit par Marie Louise Tomas

As the latent track damage cross section and defect morphology are well known in magnetic insulators, irradiations of such inorganic materials (Y3FesO12, BaFe12O19 and SrFe12019 in two different crystalline orientations) have been undertaken at different substrate temperatures. Xenon irradiations were performed at the following substrate temperatures 20, 100, 330 and 600 K and krypton irradiations only at 100 and 300 K. In the range of electronic stopping power dE/dx for which the damage morphology is known to be cylindrical and continuous, the latent track damage cross section is the same within the experimental errors whatever is the irradiation temperature between 20 and 300 K while according to the material annealing can occur at 600 K. In the range of dE/dx for which the damage morphology is discontinuous (spherical isolated defects or discontinuous cylindrical ones) the damage cross section is bigger at 300 K than at 100 K.

Ion tracks were created in olivine from San Carlos, Arizona (95% Mg 2 SiO 4), apatite (Ca 5 (PO4) 3 (F,Cl,O)) from Durango, Mexico, and synthetic silicates with the apatite structure: Nd 8 Sr 2 (SiO 4) 6 O 2 and Nd 8 Ca 2-(SiO 4) 6 O 2 using 1.6 and 2.2 GeV Au ions. The morphology and annealing behaviour of the tracks were investigated by means of synchrotron based small angle X-ray scattering in combination with ex situ annealing. Tracks in olivine annealed above $400°C undergo a significant change in track radius due to recrystallisation of the damage tracks. At temperatures higher than 620°C, the scattering images indicate fragmentation of the track cylinders into smaller subsections. Ion tracks were annealed at elevated temperatures up to 400°C in the Durango and Ca-britholite, and up to 560°C in Sr-britholite. While there was a significant change in the track radii in the Durango apatite, tracks in the two synthetic samples remained almost unchanged.

Natural apatite samples were irradiated with 185 MeV Au and 2.3 GeV Bi ions to simulate fission tracks. The resulting track morphology was investigated using synchrotron small angle x-ray scattering (SAXS) measurements before and after chemical etching. We present preliminary results from the SAXS measurement showing the etching process is highly anisotropic yielding faceted etch pits with a 6-fold symmetry. The measurements are a first step in gaining new insights into the correlation between etched and unetched fission tracks and the use of SAXS as a tool for studying etched tracks.

We report on the observation of a fine structure in ion tracks in amorphous SiO 2 using small angle x-ray scattering measurements. Tracks were generated by high energy ion irradiation with Au and Xe between 27 MeV and 1.43 GeV. In agreement with molecular dynamics simulations, the tracks consist of a core characterized by a significant density deficit compared to unirradiated material, surrounded by a high density shell. The structure is consistent with a frozen-in pressure wave originating from the center of the ion track as a result of a thermal spike.

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy-ion irradiation. An underlying core-shell structure consistent with remnants of a high-density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions differ for as-implanted and relaxed Si as attributed to different microstructures and melting temperatures. The identification and characterization of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy-ion irradiation in amorphous semiconductors.

Ion tracks were created in natural quartz and fluorapatite from Durango, Mexico, by irradiation with 2.2 GeV Au ions at elevated temperatures of up to 913 K. The track radii were analysed using small-angle X-ray scattering, revealing an increase in the ion track radius of approximately 0.1 nm per 100 K increase in irradiation temperature. Molecular dynamics simulations and thermal spike calculations are in good agreement with these values and indicate that the increase in track radii at elevated irradiation temperatures is due to a lower energy required to reach melting of the material. The post-irradiation annealing behaviour studied for apatite remained unchanged.

Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase. V

A major issue in thermochronology and U-Th-Pb dating is the effect of radiation damage, created by α-recoils from α-decay events, on the diffusion of radiogenic elements (e.g., He and Pb) in host mineral. Up until now, thermal events have been considered as the only source of energy for the recovery of radiation-damage. However, irradiation, such as from the α-particle of the α-decay event, can itself induce damage recovery. Quantification of radiation-induced recovery caused by α-particles during α-decay events has not been possible, as the recovery process at the atomic-scale has been difficult to observe. Here we present details of the dynamics of the amorphous-to-crystalline transition process during α-particle irradiations using in situ transmission electron microscopy (TEM) and consecutive ion-irradiations: 1 MeV Kr 2+ (simulating α-recoil damage), followed by 400 keV He + (simulating α-particle annealing). Upon the He + irradiation, partial recrystallization of the original, fully-amorphous Durango apatite was clearly evident and quantified based on the gradual appearance of new crystalline domains in TEM images and new diffraction maxima in selected area electron diffraction patterns. Thus, α-particle induced annealing occurs and must be considered in models of α-decay event damage and its effect on the diffusion of radiogenic elements in geochronology and thermochronology. Diffusion kinetics for noble gas thermochronometry is commonly assumed to be solely a function of temperature , and this is the basis for extrapolating the physical mechanisms observed in laboratory experiments to the temperature and time regimes of natural systems 1. However, recent new models have demonstrated that alpha-recoil damage, i.e., isolated defects induced by α-recoils from α-decay events, significantly reduces the diffusion of noble gases (e.g., He) in apatite 1–4. This effect can be reversed by thermal annealing of the radiation damage 2,3. Similar approaches have been used in the determination of the age of the oldest zircon ~4.4 Ga via a new U-Th-Pb method 5–7 : The thermally enhanced Pb diffusion during a reheating event leads to the redistribution of the radiogenic 207 Pb and 206 Pb within the nano-clusters produced by alpha-decay. In addition, the recovery of fission tracks, another type of radiation damage caused by spontaneous fission of 238 U, is generally considered as diffusion-controlled process 8–10 , an ultimate thermal effect. However, under certain radiation conditions , thermally induced diffusion is less significant than radiation-enhanced diffusion 11,12 as more vacancies and interstitials are produced by interactions of energetic ions than those that are thermally activated 13,14. In apa-tite, alpha-decay from U or Th produces a pair of an alpha-particle (energy: ~4.5 MeV He ion; ion range: ~14 µm), and an alpha-recoil (energy: 60–90 keV; ion range: 20–30 nm) that are ejected in opposite directions (Fig. 1a,b). This study addresses the recovery of alpha-recoil damage in apatite by the irradiation of alpha-particles, another source of energy that can drive the recovery process. Despite the importance of radiation effects in reconstructing the thermal histories and age of rocks 1,5,10,15 , mechanisms of radiation damage and damage recovery in minerals are still poorly understood at the atomic-scale. Radiation damage in minerals is dominated by the accumulation of Frenkel defect pairs based on nuclear stopping power, (dE/dx) n , between heavy α-recoils (usually heavier than Pb) and surrounding atoms (Fig. 1a). This is in contrast to the irradiation of alpha-particles, where electronic stopping power, (dE/dx) e , between the

With the aim of characterizing damage along nuclear tracks in apatite, Durango fluoroapatite monocrystals were irradiated under a high fluence 86Kr ion beam at the G.A.N.I.L. (Grand Acc616rateur National d'Ions Lourds, Caen, France). The resulting irradiation damage was studied by associating CRBS spectrometry and chemical etching. By applying Poisson's law to the backscattering results, the nuclear track average effective radius R e was calculated for different steps along the ion path. On the other hand, the chemical etching experiments allowed us to deduce three different damaging morphologies in correspondence to the Re values. For the first time in apatite, it has been shown that a defect fragmentation produced along the ion paths may be detected by chemical etching. These results were also applied to fission tracks in order to quantify the damage rate and to describe the damage morphology evolution along fission fragment paths.

Ion tracks were created in olivine from San Carlos, Arizona (95% Mg 2 SiO 4 ), apatite (Ca 5 (PO4) 3 (F,Cl,O)) from Durango, Mexico, and synthetic silicates with the apatite structure: Nd 8 Sr 2 (SiO 4 ) 6 O 2 and Nd 8 Ca 2 -(SiO 4 ) 6 O 2 using 1.6 and 2.2 GeV Au ions. The morphology and annealing behaviour of the tracks were investigated by means of synchrotron based small angle X-ray scattering in combination with ex situ annealing. Tracks in olivine annealed above $400°C undergo a significant change in track radius due to recrystallisation of the damage tracks. At temperatures higher than 620°C, the scattering images indicate fragmentation of the track cylinders into smaller subsections. Ion tracks were annealed at elevated temperatures up to 400°C in the Durango and Ca-britholite, and up to 560°C in Sr-britholite. While there was a significant change in the track radii in the Durango apatite, tracks in the two synthetic samples remained almost unchanged.

Ion tracks were created in olivine from San Carlos, Arizona (95% Mg 2 SiO 4 ), apatite (Ca 5 (PO4) 3 (F,Cl,O)) from Durango, Mexico, and synthetic silicates with the apatite structure: Nd 8 Sr 2 (SiO 4 ) 6 O 2 and Nd 8 Ca 2 -(SiO 4 ) 6 O 2 using 1.6 and 2.2 GeV Au ions. The morphology and annealing behaviour of the tracks were investigated by means of synchrotron based small angle X-ray scattering in combination with ex situ annealing. Tracks in olivine annealed above $400°C undergo a significant change in track radius due to recrystallisation of the damage tracks. At temperatures higher than 620°C, the scattering images indicate fragmentation of the track cylinders into smaller subsections. Ion tracks were annealed at elevated temperatures up to 400°C in the Durango and Ca-britholite, and up to 560°C in Sr-britholite. While there was a significant change in the track radii in the Durango apatite, tracks in the two synthetic samples remained almost unchanged.

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy-ion irradiation. An underlying core-shell structure consistent with remnants of a high-density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions differ for as-implanted and relaxed Si as attributed to different microstructures and melting temperatures. The identification and characterization of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy-ion irradiation in amorphous semiconductors.

In amorphous SiO 2 (a-SiO 2), a technologically most important material, average structural properties of ion tracks have been inferred from macroscopic measure-ments, yet details of the track structure and inner mor-phology are difficult to retrieve due to the lack of suffi-cient contrast inherent with most techniques. Here we report on measurements of a fine structure in ion tracks in a-SiO 2 using small angle x-ray scattering (SAXS) [1]. The ion tracks were produced in 2-µm thick a-SiO 2 , thermally grown on Si(100) substrates, by irradiation with 1.4 and 0.6 GeV Xe ions at the UNILAC accelerator. The fluence was limited to 3×10 11 ions/cm 2 to avoid signifi-cant track overlap. Thin SiO 2 layers were utilized to achieve a uniform energy loss over the extent of the layer and hence uniformity of the tracks along the ion paths. The track structure was studied using synchrotron SAXS in transmission geometry performed at beamline 15ID-D of the Advanced Photon Source, Argonne Na-tional...

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy-ion irradiation. An underlying core-shell structure consistent with remnants of a high-density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions differ for as-implanted and relaxed Si as attributed to different microstructures and melting temperatures. The identification and characterization of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy-ion irradiation in amorphous semiconductors.

In many solids, swift heavy ions (MeV-GeV) produce long cylindrical damage trails with diameters of a few nm. The projectiles induce excitation and ionization processes, releasing electrons which spread their kinetic energy via collisions with secondary electrons radially to the ion trajectory. The energy density in this cylindrical zone is determined by the ion energy deposited per unit path length (dE/dx) and by the range of the electron cascades. Since this range is directly connected to the maximum energy transfer to the electrons, the kinetic energy of the projectiles comes into play. For a fixed dE/dx value, the resulting energy density is lower for higher ion velocities. This so-called velocity effect was evidenced for latent tracks [1] as well as for etched tracks [2], revealing that track radii increase with decreasing ion velocity.