Tracks In Mica Research Articles

Dynamic evolutions of swift heavy ion induced latent tracks under electron bombardment from TEM

Abstract Dynamic evolutions of morphology and size of swift heavy ion (SHI) induced latent tracks in muscovite mica were explored using in situ transmission electron microscopy (TEM) in this paper. Prior to the measurements, muscovite mica sheets were irradiated with Kr and Bi ions with electronic energy loss (dE/dx)e of 5.9 keV/nm and 31.5 keV/nm, respectively. It is observed in TEM micrographs that the latent tracks in mica are continuously along the cross section view of the ion tracks. The track profile is not found dramatically uniform but rather it is found slightly fluctuating for similar (dE/dx)e values. In situ TEM observation clarify that atoms in the track halo are unstable compared with the lattice atoms in the vicinity of the track. Point defects induced by the electron bombardment are generated preferentially around the track core, which results in the increased diameter of the track.

Structural and electric surface characteristics of heavy ion tracks in poly(ethylene terephthalate) and mica

The entry of high-energy Kr, Xe, and Bi ions into the surface of poly(ethylene terephthalate) (PET) and mica has been imaged. It has been shown that the track images have the shape of protuberances in both cases. The formation of protuberances is associated with the degradation of the material in the track region, in the formation of an amorphous structure, and the release of low-molecular radiolysis products as gaseous compounds. Holding the irradiated PET samples in water and dilute alkaline solution for several hours changes the surface topography due to hydrolysis of the material and escape of the radiolysis products to the solution. The kinetics of track etching in the dilute alkaline solution and pore formation have been studied. The electrical resistance and the permeability of the tracks in KCl, LiCl, MgCl2, and BaCl2 electrolytes have been measured.

A comparison between neutron-fluence measurements using metal-activation monitors and standard glasses calibrated via thin uranium-fission monitors and via ηq method

The two fundamental approaches to fission-track dating involve either an explicit determination of the thermal neutron fluence (φ-method) or a calibration against age standards (ζ-method). The neutron fluence measurements are carried out with metal-activation monitors or with uranium-fission monitors, co-irradiated with the samples. Uranium-fission monitors consist of either a thin “mono-atomic”) film, or a thick fission source (standard uranium glass) irradiated against a muscovite external track detector. In this work, different techniques for performing neutron-fluence measurements were compared: based on thin-film calibration, based on thick-source calibration, and based on gamma spectrometry of co-irradiated metal monitors (Au, Co). The results suggest that more experiments are needed to make all calibrations consistent, including new measurements of the length of etched induced tracks in mica. Also the standard glass calibration carried out with thin films should be confirmed with a greater number of calibrating irradiations.

Atomic force microscopy of fission tracks in fluorapatite and mica: A tool for nanoscale investigations

Atomic force microscopy of fission tracks in fluorapatite and mica: A tool for nanoscale investigations

The geometry of etched heavy ion tracks in phlogopite mica; a clear dependence on energy deposited

It is shown that the etched track contour geometry in phlogopite mica depends on the extent of the radiation damage present in the track core. At low stopping power values (i.e. low radiation damage), the tracks have triangular (T) geometries while at high damage densities, track contours become polygons which are hexagonal (H) for normally incident fission fragments. For these tracks, the track contour geometry along the track can change from H to T or vice versa due to variations in the extent of radiation damage. Such geometry changes are abrupt and sudden. For fragments with dip angles less than 90°, the track contour geometry can be hexagonal, irregular polygon and triangular. The observed etch figures can be explained on the basis of energy deposited by the heavy ions and thermodynamic quantities of the track-crystal system.

HREM investigation of latent tracks in GeS and mica induced by high energy ions

Observations of heavy ion latent tracks in layered materials were carried out with a 400 kV high resolution electron microscope as well as with conventional 100 and 200 kV microscopes. The materials were irradiated normal to the cleavage plane at the UNILAC-accelerator at GSI Darmstadt with ions up to several MeV/u. High-resolution images of latent tracks in muscovite mica and in GeS single crystals are presented in this paper. The micrographs show that the track core represents a disordered zone. Depending on the diffraction conditions in the surroundings of the tracks, strain contrast centres are visible. The boundary between the amorphous track core and the intact crystal lattice is well defined. The cross sections of the tracks in mica have a nearly circular shape. In contrast to that they are elliptical in GeS and are well oriented with respect to the crystal lattice. The sharp amorphous–crystalline transition allows the exact measurement of the track dimensions. The values resulting for the track diameters show a large variation in size depending on the ion sort. The tracks produced by heavy ions have more than twice the diameter of those produced by light ions. Relations between the track size and the energy loss for different ions are given.

Angular distribution of the sputtered atoms from UO 2 under high electronic stopping power irradiation

This study deals with the sputtering of uranium atoms from UO 2 surfaces, induced by high 238U 15+ and 116Sn 36+ irradiation. The sputtered uranium atoms were collected on mica energy foils which were subsequently irradiated with thermal neutrons in order to fission the 235U. The fission fragments created latent tracks in mica which were revealed by chemical etching. Finally, we determined the track densities as a function of the emission angle in the mica detectors using three microscopy techniques: optical microscopy, SEM and AFM. The total yield of uranium emission and the angular distribution are given for both projectiles.

Submicroscopic analysis of tracks in mica

Tracks of 49 MeV 35Cl ions in muscovite mica were analyzed by transmission electron microscopy up to 10 Å resolution applying the track replica method. The enlargement of the track diameter is measured as a function of etching time. The track shape evolution shows circular tracks for very short etching times. By increasing the etching time the tracks gradually become ovals. For longer etching times, tracks show the characteristic rhombic shape of the bulk region. A non monotonous decrease of the track velocity vs. radius is reported. Formation of a low velocity shell in the intermediate region between the central amorphous zone and the non-perturbed crystalline lattice is suggested.

Ion tracks in mica studied with scanning force microscopy using force modulation

Aiming at an improved understanding of heavy-ion track formation we have imaged latent tracks in mica by means of scanning force microscopy. Studies based on lateral force microscopy characterized the track cross sections as amorphized zones with increased friction. In the present contribution we report on further measurements performed by operating the microscope in the mode of force modulation. The tracks, imaged by lock-in filtered signal detection, appear as areas which are softer than the undamaged surroundings. Within the experimental errors the track diameters obtained from the two experiments are in good agreement.

Latent (sub-surface) tracks in mica studied by tapping mode scanning force microscopy

This short communication presents information on the structure of latent (i.e subsurface) tracks in muscovite mica due to single 78.2 MeV 127I ions incident at an angle of 67° with respect to the surface normal. The latent tracks have been studied for the first time using tapping mode scanning force microscopy. Images of an underlying mica surface, exposed by cleaving after ion bombardment, displayed hillocks accompanied by raised tails. These features were significantly lower in height compared to similar features observed on the originally outermost mica surface. The inner back surface of the mica sheet cleaved away also displayed shallow hillocks with raised tails, but on that surface, the tails stretched in the opposite direction to those observed on the originally outermost mica surface. On both surfaces exposed by cleaving, the tail is located in close proximity to the latent ion track, showing a symmetry of expansion along the track. The present results provide more evidence for a permanent expansion occurring around each ion track, as described qualitatively by theoretical models.

The etching of natural alpha-recoil tracks in mica with an argon RF-plasma discharge and their imaging via atomic force microscopy

The conventional technique used to reveal the natural alpha-recoil tracks, as well as other nuclear tracks, in muscovite mica is to etch the mica sheets in a concentrated hydrofluoric (HF) acid solution. However, because of the fast etching along the basal plane of the mica when using HF acid, the recoil-disturbed regions are commonly enlarged laterally so that it is difficult to determine the real size of these regions. In the present study, etching with an argon radio-frequency (RF) plasma discharge is used for the first time to locate and size the alpha-recoil tracks in the mica. The investigation of the etched tracks which followed was carried out using atomic force microscopy (AFM). From a consideration of the topography observed and of the characteristics of the interactions between the argon RF-plasma and the mica substrate, it is suggested that the etch pit dimensions as revealed by the low power argon RF-plasma discharge used and imaged by AFM correspond to the actual scales of the etchable damaged regions induced by the alpha-recoils in the mica, in contrast to those revealed by etching in HF acid. The mechanism of the preferential sputter etching observed at low power levels in an argon RF-plasma discharge at the etchable regions is discussed.

Formation of amorphous latent tracks in mica

There are controversial experimental data on latent track sizes in mica bombarded by energetic ions in the electronic stopping regime. Recent measurements by wide angle X-ray diffraction [1] and atomic force microscopy (AMF) with lateral scanning [2] provided intermediate values between previous AMF [3] and small angle neutron scattering results [4]. In the present paper the variation of the amorphous track size with the electronic stopping power Se is analyzed based on a thermal spike model. Good agreement is found between the results obtained by wide-angle X-ray diffraction and AMF with lateral scanning and the predictions of the model. The relation predicted between the thermal properties and the radiation sensitivity is also confirmed. A comparison with latent track formation in magnetic insulators is given and very close values of the thermal spike parameters are obtained from the analysis.

Ion track diameters in mica studied with scanning force microscopy

Aiming at a detailed study of morphology and size of heavy-ion tracks in mica, thin samples were irradiated with several heavy-ion species at the universal linear accelerator UNILAC of GSI. The latent ion tracks were investigated in air with a scanning force microscope (SFM) operated in the lateral-force mode. The track cross sections appear as areas of increased friction. The diameters of individual latent tracks were extracted by registering lateral-force line profiles of the amorphous track cross sections embedded in the undisturbed crystalline mica lattice. Averaged track-diameter values were determined by fitting the diameter distributions with Gaussian curves. We observed an increase of the track diameters with increasing electronic energy loss. The results are compared with earlier data from small-angle scattering and from topographic SFM measurements.

On determination of Th concentration in specimens by means of gamma rays and alpha particles

Experiments on improving the track technique for the determination of Th content in natural samples have been performed. For Th concentration measurements, γ-rays with energies of 18 and 20 MeV were used. For γ-rays in the energy range 6–23.5 MeV, the ratio of fission fragment track densities N U/ N Th of these elements for thick targets has been obtained. The ratio ranges from 1.7 to 3.2 with the maximum at a γ-ray energy of 15 MeV. The determined Th concentrations in the calibrated Th standards and iron manganese nodules agree, within experimental error, with the known values. For 9.1 MeV/n α-particles, the track density ratio N Th/ N U has been found to be equal to (1.06 ± 0.07), but the Th content was lowered, possibly due to the vertical inhomogeneity of the α-particle beam and also due to partial thermal fading of the tracks in mica. The investigation was performed at the Laboratory of Nuclear Reactions, JINR.

Observations by X-ray diffraction of structural changes in mica irradiated by swift heavy ions

The descriptions of high-energy ion irradiation damage in mica by small-angle X-ray/neutron scattering and electron microscopy are used to support some models of track formation in dielectric solids. More recently heavy ion tracks in mica could be observed by atomic force microscopy and the dependence of the track radius on the particle energy loss is in contradiction with previous results. This discrepancy as well as the structural modifications (i.e. amorphization, dilatation, distortions) of ion-irradiated mica are discussed using the technique of wide-angle X-ray diffraction.

Advances in solid state nuclear track detectors

Several types of commercially available phosphate glasses with a wide range of sensitivities have recently been developed. Chief among these is BP-1, which has a high sensitivity and an unprecedented charge resolution. CR- 39 has been found to respond differently at velocities below ∼10−2 c, where nuclear stopping begins to dominate, than at high velocities, where electronic stopping dominates. Atomic force microscopy has been shown to be a powerful new tool for the study of the etching process, using recoil tracks in mica. CR-39 has been used to set limits on cold fusion rates in strong conflict with rates claimed by some electrochemists. CR-39 and BP-1 have been used to study a number of topics in atomic and nuclear physics including charge pickup in relativistic nucleus-nucleus reactions, nuclear and electromagnetic spallation of relativistic heavy nuclei, the determination of electron attachment and stripping cross sections for relativistic heavy nuclei, and cluster radioactivity. CR-39 is being used to search for strangelets in nature and in ultrarelativistic nucleus-nucleus interactions. Several studies of cosmic ray composition, including TREK, ANTIPODE, HIIS, and UHCRE, are obtaining new results using CR-39, polycarbonate, and BP-1 glass. An experiment to search for weakly interacting massive elementary particles called WIMPs will use mica to detect very short tracks of nuclei that recoil when struck elastically by the WIMPs.

Submicroscopic observation of fission product tracks in mica

The method of folding the replica of tracks has been shown to be a useful tool to analyze nuclear tracks at submicroscopic level. To date, this methodology was applied only to organic SSNTD. In the present study its applications are extended to an inorganic material. Muscovite mica was irradiated with fission products and replicas of track profiles were evaluated by TEM up to 10 Å resolution. The tracks showed a central, amorphous damaged region and an external bulk zone where the crystalline nature of the mica was presented.

On the determination of the track age of some natural crystals

The detailed investigations of annealing behavior of fission fragment tracks in muscovite mica, apatite and whitlocite crystals have been performed. For muscovite mica the annealing procedure has been applied to single fission fragment tracks, for apatite and whitlocite crystals — for binary events. As it has been observed, the controlled annealing produced the shortening down of fission fragment track length. Such procedure provides more direct comparison of the track length spectra due to spontaneous fission of 238U and due to thermal neutron induced fission of 235U in the same crystal; it allows one to obtain more correct value of the track age.

Electrochemical etching of fission fragment tracks in muscovite mica and soda glass

Electrochemical etching study has been carried out for muscovite mica and soda glass, irradiated with fission fragments of 252Cf, under various electrical and etchant parameters. In case of muscovite mica, it is observed that preferential chemical etching is correlated with applied field strength and frequency. Soda glass does not exhibit any such behaviour. The investigations reveal that treeing phenomenon does not occur in muscovite mica and soda glass under the prevailing experimental conditions.

Identification and selection criteria for charged lepton tracks in mica

Decorated tracks of minimum ionizing particles, including muons, relativistic shower particles and positrons from beta-decay have been identified in natural crystals of mica. Criteria for the selection and identification of these particle tracks against a background of crystal-related decorated features have been derived. A procedure for determining the sensitivity and duration of the recording period also has been found.