Track Fading Research Articles

Track etching in amorphous metallic Fe81B13.5Si3.5C2

A review of the presently available results for track etching in metallic glasses is given. Latent tracks in amorphous Fe81B13.5Si3.5C2 can be selectively etched to surface pores with a wide cone opening angle. Etched tracks have been observed only if the alloy is in the amorphous and not in the crystalline state. Annealing tests after ion irradiation show that track fading occurs for temperatures above 200°C. An etching threshold is observed at a critical energy loss of 3.4 keV/Å, which is far above the threshold for creating damage (1.3 keV/Å) as observed by resistivity measurements. The etching behaviour near the threshold shows a transition regime from non-homogeneous etching. This observation is related to etched tracks in insulators. The occurrence of the etching threshold is used to determine the influence of the distribution of the radial dose of ions having various velocities. The experimental results are compared with thermal spike calculations.

Annealing kinetics of fission tracks in zircon: an experimental study

A series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350–750°C for 10 −1–10 3 hr (i.e. 4.5 min-∼40 days). Variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from Nisatai Dacite. The fading contours of normalized mean track length ( r) on the Arrhenius diagram showed as sets of straight lines. We performed a series of model fittings, called the parallel and fanning models, in order to describe the decrease in r with increasing temperature or heating time. The lowest temperature limit of the zircon partial annealing zone (ZPAZ) was defined as r ≈ 0.95, and the highest as r ≈ 0.4, which approximately corresponded to the total fading of surface tracks. Extrapolation of the results of the laboratory experiments to the geological timescale gives, for a heating duration of 106 yr, estimated values of the ZPAZ of ∼210–320°C (± 60°C, 2σ) with the parallel model; ∼190–350°C (± 50°C, 2τ) with the fanning model (critical temperature, T 0 = ∞); and ∼170–390°C (±50°C, 2σ) with the fanning model ( T 0 ≠ ∞). The temperatures of the ZPAZ decrease by ∼20°C for an annealing duration that is an order of magnitude longer. Because the estimated closure temperature of zircon fission-track analysis approximately corresponds to the middle of the ZPAZ, these results support the previously estimated closure temperature of ∼240°C. By varying the etching time it was revealed that significant removal of α-radiation damage occurs at r ≈ 0.93.

Chronology of Pliocene and Quaternary bioevents and climatic events from fission-track ages on tephra beds, Wairarapa, New Zealand

High-resolution Pliocene and Pleistocene sequences exposed on land in New Zealand are some of the few detailed records of widepread marine bioevents and paleoclimatic changes in the Southern Hemisphere. Marine biostratigraphy calibrated in deep-sea cores by paleomagnetic reversals has been the primary basis for the chronology of these sequences. We have determined ages for several tephra beds which now provide an independent numerical age calibration for a well-studied marine and terrestrial section in Wairarapa. By using the isothermal plateau fission track (ITPFT) method on volcanic glass we have overcome the problems of partial track fading and detrital mineral contamination, which hindered earlier studies, to reveal a new chronology extending back to nearly 5 Ma. Our ages for the Hikawera Tuff (4.91 ± 0.25 Ma) and Spooner Tuff (3.44 ± 0.13 Ma) are consistent with the appearance and disappearance of many early Pliocene foraminiferial species, validating their age calibration in New Zealand. However, some fossil occurrences, including coccoliths, differ temporally by as much as 0.55 Ma, perhaps due to local tectonic-induced recycling. Four Pleistocene tephra beds (Potaka tephra (1.00 ± 0.03 Ma), Kaukatea tephra (0.87 ± 0.05 Ma), Rangitawa tephra (ca. 0.35 Ma) and Kawakawa tephra (ca. 0.22 Ma)) are now recognised in the Wairarapa sequence via stratigraphic and new geochemical and age data. These beds allow direct correlation to other marine and terrestrial basins, as well as volcanic regions in New Zealand, and will ultimately aid in a regional paleoenvironmental reconstruction where bioevents are absent. The tephra ages indicate that the marine sediment accumulation rates varied from 90 to 250 m/Ma between different sections of the Pliocene and reached ca. 350 m/Ma in the last 2.4 Ma, when the sequence displays pronounced glacioeustatic cyclic deposition. In the terrestrial realm, the oldest loess in New Zealand is now constrained to between 1.00 and 0.87 Ma.

Ageing effects on a new polymeric track detector SR-90 and a model of the nuclear track formation

The relationship between the detection sensitivity for charged particles and the molecular structure of polymers like CR-39 was studied while changing the average chain length of the carbonate linkages cross-linking the polyallyl chains. It has been found that the polymer shows the highest sensitivity when the length of the carbonate linkages is about 1.6 times longer than that of CR-39. Just after polymerization this polymeric track detector named SR-90 has about 3 times higher sensitivity than CR-39 but ageing effects on its sensitivity are very strong. In this connection a model of the latent track formation and the mechanism of the track fading are discussed on the basis of the recombination of free radicals produced by charged particles.

Isothermal plateau correction for partial fading of fission tracks in hydrated glass shards

The age of hydrated glass shards from the Pleistocene Ester Ash Bed at Fairbanks, Alaska, is determined using the population-subtraction fission-track method. The age so determined is then corrected for partial annealing by use of the isothermal plateau fission-track (ITP-FT) technique. In this paper, we describe the mathermatical basis of a procedure for obtaining the correct fission-track age using the ITP-FT technique.

A search for particle tracks in the metallic glass Pd80Si20

Abstract Thin samples of the metallic glass Pd 80 Si 20 have been irradiated at 150 K with 2.8- MeV / u - 129 Xe ions . A stack of these samples has been investigated at room temperature for the occurrence of particle tracks by small angle neutron scattering in the q-range of 3×10 −3 A −1 to 6.7×10 −2 A −1 . Neither traces of radiation damage nor indications arising from particle tracks have been found. In comparison with other results it is concluded that the most probable explanation for the absence of any radiation-induced scattering signal is due to a total track fading far below room temperature.

First running experience with the laser calibration system of the UA1 central detector

We report on a UA1 technical run made with four nitrogen lasers mounted on the UA1 Central Detector during the 1987 proton-antiproton collider run. With only moderate laser power (< 7 μJ/mm 2) and the help of gas seeding (1 ppb of tetra-methyl-phenylene-diamine [TMPD]) straight 2 m calibration tracks can be produced. The unexpected effect of track fading under high luminosity conditions was observed. A model is presented explaining this phenomenon, which is based on the removal of neutral TMPD molecules from the drift volume via positive ion charge exchange.

Study of thermal annealing characteristics of 5022Ti ion tracks in a soda glass track detector

Samples of soda glass detectors were exposed vertically to a 50 22 Ti ion beam, of energy 4.9 MeV n -1 , at the Joint Institute of Nuclear Research (JINR), Dubna, U.S.S.R. These exposed samples were annealed at different temperatures for various intervals of time. The chemical etching of these samples was performed in the etching solution (HF, 48 vol.%, + H 2 SO 4 , 96 vol.%, + H 2 O, mixed in the ratio 6:1:18 with a small amount of Zn) at 40°C for different etching times. The variation of track diameter with annealing temperature and annealing time was studied, and finally, the activation energies for various percentages of track fading were determined.

Isothermal plateau fission‐track age of the Late Pleistocene Old Crow Tephra, Alaska

Hydrated glass shards of the widespread Old Crow tephra in Alaska have been dated by the isothermal plateau fission‐track method, which corrects for partial track fading, if present. The weighted mean age of 149±13 ka is older than previous estimates, which range from 86 to 109 ka. These new data support the view that Old Crow tephra was deposited during the cold interval that immediately preceded the last interglacial, which is dated in the marine record at 125 ka B.P. It is likely, therefore, that the buried forest beds and numerous ice‐wedge pseudomorphs, preserved in sediments just above Old Crow tephra in interior Alaska, relate to the last interglacial and not a younger warm event of early Wisconsin age.

On shukolyukov equation for the fading of fission tracks in minerals

Abstract In this paper it is shown that the differential equation to describe the fading of fission tracks in minerals proposed by Shukolyukov et al. (trans. from Geokhimiya Ǎo3, pp. 291–301, 1965) should be correct in first approximation since its solution for a particular condition where the activation energy E is taken as constant gives the linear relation between log t and T-1, for constant values of ρ/ρ0, known as Arrhenius plots. It is also shown that another experimental result, the linear variation of ρ/ρ0 with log t for constant T is not independent from Arrhenius plots for a given ρ/ρ0 if E is given by E = β ρ/ρ0 + γ, where β and γ are constants, as proposed by Dakowski et al. (Bull.Acad.Polon.Sci.Ser.Terre 22, pp. 11–17, 1974) for minerals. Then there is some consistency so that Shukolyukov equation with E given by E = β ρ/ρ0 + γ can be proposed as a interesting tool for further studies on fading of fission tracks in minerals.

Alpha-Decay Damage and Annealing Effects in Natural Pyrochlores: Analogues for Long-Term Radiation Damage Effects in Actinide, Pyrochlore, Structure Types

ABSTRACTCubic pyrochlore structure types, A2-mB2O6(O, OH, F) i-n*pH2O, and their derivatives (e.g., monoclinic zirconolite) are important actinide-bearing phases in polyphase, ceramic waste forms (e.g., SYNROC). These waste form phases may typically accumulate alpha-decay doses of 1025 alpha-events/m3 in 1, 000 years or 1026alpha-events/m3 in one million years (i.e., for SYNROC with 20 wt. % HLW). Natural pyrochlores have calculated doses ranging from 1024 to 1027 alpha-events/m3 (= 0.02 to 50 dpa) which have accumulated over ten to a thousand million years. Actinide doping experiments typically reach doses of 1025 alpha-events/m3over periods of several years. Detailed x-ray diffraction analysis of natural samples reveals that the alpha-decay dose at which there is an initial loss of crystallinity (i.e., transition from crystalline to the aperiodic, metamict state as a result of alpha-decay damage) increases as a function of the geologic age of the sample. The increase in the calculated alpha-decay dose which is associated with a specific degree of damage (e.g., loss of x-ray diffraction intensity) is attributed to annealing of isolated alpha-recoil tracks back to the original, crystalline structure. Based on a model of gradual track fading, the alpha-recoil tracks in natural pyrochlores have mean lives on the order of 108 years. In contrast, minerals which remain crystalline (e.g., uraninite, UO2) despite doses of over 1027 alpha-events/m3 have mean alpha-recoil track lives of approximately 104 years. This demonstrates that the microstructure of alpha-decay damaged materials depends not only on the total alpha-event dose, but also on the annealing kinetics of alpha-recoil track fading. Therefore, the prediction of the long-term performance and final state of crystalline phases in ceramic nuclear waste forms requires the determination of alpha-recoil damage annealing as a function of time and temperature.

Uplift and Subsidence of the Suez Rift: Constraints from Fission-Track Analysis and Sediment Backstripping: ABSTRACT

The Gulf of Suez is a Neogene rift that has evolved as one arm of the Sinai triple junction. The basement uplifts flanking the rift are larger than can be explained by uniform lithospheric extension. The timing of the regional heating required by the uplift has important implications for hydrocarbon maturation for the Gulf of Suez and rifts in general. The local geology indicates that the uplift did not predate rifting. Therefore, a regional subsidence and two-dimensional backstripping of the rift sediments were undertaken in conjunction with fission track analyses of the basement uplift. The initial rift deposits (Nukhul Formation) indicate slow extension during the earliest Miocene. The extension rate increased at the beginning of the deposition of the Rudeis Formation at approximately 19 Ma as the Gulf of Suez entered its main phase of rifting. By the end of the deposition of the Kareem Formation (approximately 14-15 Ma), most of the Africa-Arabia separation had transferred to the Gulf of Aqaba-Dead Sea transform. In order to determine the onset of the rift flank uplift relative to the rift history, 55 apatite fission track analyses were performed on samples from the basement of the eastern desert, on the western side ofmore » the rift. Apatite fission tracks record the thermal history of the samples for temperatures up to 125{degree}c. Apparent ages range from 382 to 11 Ma representing samples that have undergone various degrees of track annealing. Track length distributions clearly show the fading of tracks acquired prior to uplift in more deeply buried samples and the accumulation of long unannealed tracks subsequent to unroofing. The pattern of the track length vs. age distribution indicates that major uplift began simultaneously with the main phase of rifting at 19-20 Ma.« less

Fission track annealing behaviour of minerals of the East Alligator River uranium field, N.T., Australia.

The possibility of annealing of radiation damage in minerals and hence of track fading, always exists. This effect can be in response to a short time, higher temperature event, or be caused by prolonged annealing, at only a slightly elevated temperature during the geothermal history of earths crust. Track retention in minerals apatite, chlorite, biotite, phlogopite, muscovite, garnet, epidote and zircon have track retention over a wide range of temperatures (90–250°C), when we consider closing temperatures for fission track system. Further experiments have been made to determine the calibration curves relating track length shrinkage with track density reduction.

Progress Towards an Operational Personal Neutron Dosemeter Based on Electrochemical Etching of CR-39

Abstract A trial operational personal neutron dosemeter based on the electrochemical etching of CR-39 is described. Experimental studies to determine the effects of time and environment on the neutron sensitivity of the plastic detector, the fading of latent tracks, and on the background observed after processing, are summarised. It is shown that environmental effects are generally not serious and can be minimised by simple precautions. The most significant remaining problem for an operational dosemeter is that of the poor angular response of a single planar detector. In addition, further reduction in the background uncertainty is very desirable, and will be essential if the recent ICRU recommendation to increase the Quality Factor to 25 is endorsed.

Thermal annealing of nuclear tracks in polycarbonate plastic

Thermal annealing, or fading, of latent tracks in a polycarbonate plastic nuclear track detector is investigated. An empirical expression for fading of tracks of relativistic uranium ions is determined, and its form is physically interpreted.

Fading of latent tracks in CR-39 due to environmental conditions

Evidence presented in the literature indicates that the sensitivity and stability of latent tracks in CR-39 is affected by the environmental conditions which the detector experiences both before and after the irradiation. Studies have been made to determine the magnitude of these effects in CR-39 with ion beams of 1 H, 16 O, 20 Ne, 40 Ar and 56 Fe. Post-irradiation annealing studies were performed in air and vacuum. As a result, the beneficial effect of anti-oxidant doping of CR-39 on the stability of the material and of latent tracks was confirmed.

Annealing of 54 132 Xe-ion tracks in Lexan and Makrofol plastic track detectors

Samples of Lexan and Makrofol-E polycarbonate plastic track detectors were exposed to 1·1 MeV/N54132Xe-ions to investigate the thermal track fading properties of these plastics. The experimental results show that there is no effect of annealing on the bulk etch rate while the track etch rate decreases with annealing. The track diameter decreases with increase in annealing time and temperature. It is also observed that the track density is reduced as a result of annealing. The experiments reveal that the track lengths are, in general, decreased by the application of heat and that the oblique tracks are less stable than the vertical tracks. The decrease in diameter of54132Xe-ion tracks in Makrofol-E due to heat treatment is faster than that of54132Xe-ion tracks in Lexan.

High temperature fission track annealing in natural fluorapatite

Annealing of etchable fission tracks in apatite has been studied previously at temperatures between 473 K and 623 K and annealing times up to 2 years. Results have been used to extrapolate to geological times in order to obtain corrected fission track ages. On the other hand, extrapolation to higher temperatures and shorter times is needed in the interpretation of track fading in meteorites. In order to investigate the validity of this extrapolation, single isothermal annealing experiments have been made at 668 K and 695 K. It has been found, that for these high temperatures serious experimental problems arise due to sample handling and a delayed temperature increase in the sample. To avoid these difficulties a new annealing procedure has been created and results obtained prove the exponential annealing law for high temperatures.

Fission-track analysis of apatite and zircon defines a burial depth of 4 to 7 km for lowermost Upper Devonian, Catskill Mountains, New York

Apatite and zircon grains separated from a sandstone layer of earliest Late Devonian age, Catskill Mountains, have been subjected to fission-track analysis. A 125-m.y. age, obtained on the apatite grains, requires a temperature for the sediment of less than 120 °C during the past 125 m.y. At some time prior to 125 m.y. ago, temperatures were above 120 °C long enough to cause complete fading of tracks. Analysis of zircon grains resulted in a fission-track age of 320 m.y. Zircon data indicate that the temperature of the sediment layer enclosing the grains did not exceed 175 to 200 °C over a 235-rn.y. period (time between sedimentation and 125 m.y. ago). If one assumes a typical geothermal gradient of 25 °C/km, a burial depth of between 4 and 7 km is indicated for the lowermost Upper Devonian, atskill Mountains.

Annealing of etchable fission induced defects at high temperatures in natural fluorapatite

Abstract Annealing of etchable fission tracks in apatite has been studied previously at temperatures between ∼200°C and 350°C and annealing times up to 2 years. Results have been used to extrapolate to geological times in order to obtain corrected fission track ages. On the other hand, extrapolation to higher temperatures (and short times) is needed in the interpretation of track fading in meteorites. In order to investigate the validity of this extrapolation, single isothermal annealing experiments have been made at annealing temperatures up to ∼500°C. It has been found that at these high annealing temperatures and short annealing times a serious experimental problem arises when using usual annealing procedures due to a delayed temperature increase in the sample. Results obtained (which prove the validity of the annealing law up to ∼500°C) and implications for further studies will be discussed.