Track Fading Research Articles

Sensitivity reduction and track parameters fading of PADC irradiated to high energy ions after twenty-seven years

PADC track etching parameters measured in 1994 and 2021 were compared. Track fading over the longest time (27 years) was determined. The etching conditions of the samples were reproduced as closely as possible, namely 6.25M NaOH and 50 °C. The difference in track parameters of diameter, bulk, track etch rate, and detector sensitivity with detector depth for 1.89 GeV N, 0.96 GeV C, 19.2 GeV Ar, 46.48 GeV Fe, and 17.7 GeV Ni have been measured. Track diameter growth with etching time, te was observed for N, C, Ar, Fe, and Ni tracks and compared with 1994 data. Clear larger bulk and track etch rates have been observed for the current measurements compared to the previous ones for the 5 ions under investigation. A significant reduction in PADC sensitivity due to fading was observed after these twenty-seven years. The higher the ion's LET, the more the fading. The reduction rate was calculated, and a sensitivity correction formula was introduced. Detector sensitivity at any previous time can be calculated from the current sensitivity by the suggested equation. The physical and chemical explanations for the fading changes in different track parameters were suggested.

Ion charge separation with new generation of nuclear emulsion films

Abstract In hadron therapy, the accelerated ions, interacting with the body of the patient, cause the fragmentation of both projectile and target nuclei. The fragments interact with the human tissues depositing energy both in the entrance channel and in the volume surrounding the tumor. The knowledge of the fragments features is crucial to determine the energy amount deposited in the human body, and - hence - the damage to the organs and to the tissues around the tumor target. The FOOT (FragmentatiOn Of Target) experiment aims at studying the fragmentation induced by the interaction of a proton beam (150-250 MeV/n) inside the human body. The FOOT detector includes an electronic setup for the identification of Z ≥ 3 fragments integrated with an emulsion spectrometer to measure Z ≤ 3 fragments. Charge identification by nuclear emulsions is based on the development of techniques of controlled fading of the particle tracks inside the nuclear emulsion, that extend the dynamical range of the films developed for the tracking of minimum ionising particles. The controlled fading strongly depends on temperature, relative humidity and treatment duration. In this study the performances in terms of charge separation of proton, helium and carbon particles, obtained on a batch of new emulsion films produced in Japan are reported.

Modgil-Virk Formulation of Single Activation Energy Model of Radiation Damage Annealing in SSNTDs: A Critical Appraisal

Passage of heavy ions produces radiation-damage trails known as latent tracks in a variety of solid-state nuclear-track detectors (SSNTDs). These tracks are made visible in an optical microscope by a simple process known as chemical etching. It is a well-known fact that latent tracks are radiation damage trails in SSNTDs, which can be annealed by thermal heating. Modgil-Virk formulation of single-activation-energy model of radiation damage annealing was proposed as an empirical approach for explaining the thermal fading of nuclear tracks in SSNTDs. The empirical formulation of this model is based on track annealing data collected from both isothermal and isochronal experiments performed on different types of SSNTDs using a variety of heavy ion beams and fission fragments. The main objective of this empirical model was to resolve some contradictions of variable activation energy derived by using Arrhenius plots to study annealing in mineral SSNTDs. Some equivalent versions of the Modgil-Virk model have been proposed but the concept of single activation energy is vindicated in all empirical formulations. The model always yields a unique value of activation energy independent of the nature of the ion beam used and the degree of annealing. The anisotropy of the mineral SSNTDs is revealed by variation in activation energy along different crystal planes and even with different orientations of the ion beam on the same plane. Some recent experiments are a pointer to the successful exploitation of this model for future cosmic-rays studies using SSNTDs.

Distinction between the Youngest Toba Tuff and Oldest Toba Tuff from northern Sumatra based on the area density of spontaneous fission tracks in their glass shards

Determination of the area density of spontaneous fission tracks (ρs) in glass shards of Toba tephra is a reliable way to distinguish between the Youngest Toba Tuff (YTT) and the Oldest Toba Tuff (OTT). The ρs values for YTT, uncorrected for partial track fading, range from 70 to 181tracks/cm2 with a weighted mean of 108±5tracks/cm2, based on 15 samples. Corrected ρs values for YTT are in the range of 77–140tracks/cm2 with a weighted mean of 113±8tracks/cm2, within the range of uncorrected ρs values. No significant difference in ρs exists between YTT samples collected from marine and continental depositional settings. The uncorrected ρs for OTT is 1567±114tracks/cm2 so that confusion with YTT is unlikely.The ρs values of the Toba tephra at Bori, Morgaon, and Gandhigram in northwestern India indicate a YTT identity, in agreement with geochemical data on their glass shards, the presence of multiple glass populations, and a glass fission-track age determination. Therefore, the view of others that OTT is present at these sites – and thereby indicates an early Pleistocene age for the associated Acheulean artifacts – is incorrect.

Track fading and its applications in archaeology, tectonics and geothermal chronology in China

Track fading is a basic phenomenon in track science and has been the source of information in geosciences. This article summarizes the knowledge of track fading and gives some examples of successful applications of track fading in archaeology, tectonics and geothermal chronology in China. The applications of track fading are classified into 5 modes: (1) mode of complete fading (annealing); (2) mode of partial fading; (3) use of the dependence of track fading on time and temperature; (4) use of the differences of track fading between coexisting minerals; and (5) use of fading-reduced track length. Track fading mechanisms hints that scientists in geothermal chronology should adopt microprobes for quantitative elemental analysis to determine the detailed chemical compositions of each mineral grain or at least of the grains from each position of geological structures in order that one becomes well aware of the relation between the track fading behavior and chemical compositions of the mineral used.

Are ageing and fading really a problem for the quality of the passive radon measurements?

Since ageing and fading of alpha tracks in CR-39 are acknowledged to modify the sensitivity of radon measurement by an alpha track device (ATD), a Radon Service operating under quality assurance has to state how these effects affect the uncertainty of the measurements, especially when long term exposures are met. A test lasting one year has been carried out, by using a total of 624 PADC detectors, to analyse the effects of three different treatments (temperature, light and as used inside the ENEA holder) together with the factor of the duration of the treatment (1, 3, 4, 6, 9 and 12 months) on the detector response. The replications ( N = 6 ) and the target exposure ( 4000 kBq h m - 3 ) were so set to achieve a minimum of 2% as significant statistical difference between treatment and control exposures. The shift of the track effective minor axis distribution has been investigated and related to the reduction of the sensitivity, which resulted in correlation with the surface removed layer of the bulk material. The use of a sensitivity value dependent on how fading, ageing and other factors modify the track diameter distribution was able to reduce the bias of the measurement.

Experimental study on hydrothermal annealing of fission tracks in zircon

Increasing temperature causes fading of fission tracks (FTs) in minerals, which has been quantified by many laboratory heating experiments in atmosphere. In order to elucidate whether or not FT annealing at hydrothermally pressured conditions is the same as that at atmospheric condition, we performed zircon heating experiments using a hydrothermal synthetic apparatus. For reliable comparison, we annealed the same zircon samples using the same temperature monitor and analyzed them using the same experimental procedure as the previous experiment at atmosphere [Yamada et al., Chem. Geol. (Isot. Geosci. Sect.) 122 (1995) 249]. The observed FT annealing characteristics are indistinguishable between atmospheric and hydrothermally heating. It is therefore implied that the annealing kinetics of FT in zircon previously established can be applied to thermal history analysis of rocks that were subjected to hydrothermal conditions in nature, such as those in fault and subduction zones.

Use of glazes on porcelain from near ground zero to measure Hiroshima neutron fluence.

Several porcelain samples from almost directly beneath the atomic explosion at Hiroshima on 6 August 1945, have been scanned for induced fission tracks, produced mostly by the thermal neutrons from the bomb due to interactions with trace uranium in their glass coatings. The ability to use porcelain opens a new and abundant material for retrospective dosimetry. Four different samples had thermal neutron fluences in 1945 of 1.0, 3.8, 4.1, and 8.9 x 10(12) cm(-2). The different values are not caused by track fading, but are likely to result from differing shielding at different nearby positions. Assuming that the three highest fluences, which have overlapping uncertainties, are at locations of minimum shielding, the statistically weighted thermal fluence in the air at ground level and ground zero was 4.8 x 10(12) cm(-2) with a statistical uncertainty of 15%. This value lies between the calculated value of 6.5 x 10(12) given in DS86 and the 3.7 x 10(12) inferred from induced radionuclides by Hoshi et al. (1998).

The effect of simultaneous temperature, pressure and stress on the experimental annealing of spontaneous fission tracks in apatite: a brief overview

Tracks made in minerals by the electronic stopping of uranium fission fragments provide a modern geological dating tool, and are believed also to yield specific information on the low-temperature thermal history of rocks. Experimental work showing that the damaged crystal lattice along a fission track recovers primarily as a function of temperature ignored the fact that the basic theory of atomic diffusion requires an exponential decrease in the intrinsic diffusion coefficient with increasing pressure. Here, fission track recovery was experimentally investigated in basic apatite under the simultaneous influences of temperature, pressure and stress. We show that track fading is a complex recovery mechanism responding to several environmental physical parameters simultaneously. In particular a strong decrease in the track recovery rate was observed as a function of increasing pressure. And a nearly temperature-independent recovery was observed in samples under stress.

Experimental evidence for the pressure dependence of fission track annealing in apatite

Fission track analysis has seen a major expansion in application to general geological problems reflecting its advances in understanding the temperature dependence of track annealing and track length distributions. However, considerable uncertainties still persist, in particular concerning the stability of fission tracks subjected to the interaction of environmental physical parameters (e.g. pressure, temperature, stress) and in extrapolation of laboratory data to geological time scales. In this work, we studied the fading behavior of spontaneous fission tracks in basic apatite [hexagonal Ca 5(PO 4) 3(OH, F, Cl)] when exposed simultaneously to laboratory pressures, temperatures and stress over varying time spans. The experiments showed that track fading is a complex recovery mechanism, which is extremely sensitive to the coupling of these three parameters. In particular, a strong decrease in the fission track fading rate was observed as a function of increasing pressure. And a nearly temperature-independent dramatic increase in fission track recovery was observed as a function of stress. Consequently, (1) the stability field of fission tracks in apatite increases towards temperatures higher than 110°C depending on the absolute pressure; (2) closure ages in apatite are underestimated (>100% for an ideal geothermobarometric gradient); (3) related exhumation and erosion rates are overestimated above the closure temperature and underestimated below the closure temperature; and (4) since the widely applied statistical description of thermally induced fading kinetics does not account for the influences of either pressure or stress and is based on fission track annealing data produced at ambient pressure, the accuracy in extrapolating fission track data to geological time scales and in their application to dynamical systems must be cast into doubt.

Hiroshima neutron fluence on a glass button from near ground zero.

A decorative glass button that was uncovered at a location that is 190 +/- 15 m from directly beneath the atomic explosion at Hiroshima on 6 August 1945 has been scanned for induced fission tracks produced mostly by the thermal neutrons from the bomb due to interactions with the trace uranium that is normally present in silicate glasses. In surveying 4.14 cm2 at 500x magnification, 28 tracks were seen. From a calibration irradiation in a nuclear reactor we infer that the neutron fluence in 1945 was 5.7(+/-1.1) x 10(11) cm(-2); and, allowing for shielding by the structure in which the button was probably located, the free-air (i.e., outside) value is estimated as 1.5(+/-0.5) x 10(12) cm(-2). A limit has been placed on possible fading of the radiation-damage tracks that could increase the fluence by at most a factor of 1.27. The values bracket the calculated value of 9 x 10(11) given in DS86 but are higher than the 3.6 x 10(11) inferred from induced radionuclides for the distance given. The difference is, however, within the observed variability of the two types of results.

Preparation of two uranium glass reference materials for fission-track dating of geological samples

The European Commission produced and certified uranium glass for fission-track dating in 1996 (Reference Material IRMM-540). This material is now out of stock and a project for the preparation of two new reference glasses is underway. The new glasses, containing nominally 15 and 55 mg kg −1 uranium, were prepared from blended oxide powder, and cast using an improved method, which minimised micro-scale defects and optimised the yield. Glass rods were produced which were then cut into discs of 2 mm thickness and 15 mm diameter and subsequently polished. Uranium homogeneity and fission-track stability are critical properties of the glass. An extensive study was carried out to verify the homogeneity by fission-track counting, investigating both within-disc and between disc effects, and to investigate potential track fading due to thermal annealing. No evidence of uranium heterogeneity was detected. The stability study, using an “isochronous” method, in which all measurements are made at the end of exposure to artificial ageing, is still underway. The reference material will be certified for isotopic composition (natural), uranium mass fraction and neutron fluence (one disc out of each set of three will be irradiated, together with a mica foil, to induce fission tracks in a certified fluence). The reference materials will be released as IRMM-540R ( 15 mg kg −1 U) and IRMM-541 ( 55 mg kg −1 U).

A global model for annealing in solid state track detectors

A systematic study of annealing phenomenon in solid state track detectors (SSTD) is presented using a quasi-equilibrium approach for the defects migration process. The nonlinear nature of the mechanism is also taken into account, which leads to an interesting formula for rate of annealing. Some of the experimentally tested empirical/semi-empirical formulae can also be deduced from it under certain approximations. The importance of the concept of relaxation time/hopping time is stressed. The temperature dependence of rate of annealing follows automatically from this formulation. Suggestion is made for experimental measurement of half life of fractional thermal fading of tracks so that the nonlinearity parameter can be computed and annealing process can be better understood.

Track fading and track regrowth in cellulose nitrate SSNTD

Isothermal post-irradiation annealing at room temperature, i.e. practical fading of alpha particle tracks in cellulose nitrate (CN) detectors has been studied. It is found that the fading process, by itself, lasts about a month. Thereafter the registration efficiency is stabilized and holds constant for about ten days. Then a new process begins which was not observed earlier for CN-detectors. This new process-growing has time boundaries too and lasts 1–2 months. On its completion the registration efficiency becomes equal to the initial value. Experimental data obtained in 1990–1993 on fading and growing of alpha particle tracks are presented in this paper for a long-term storage of irradiated detectors. Mathematical description of the dependence obtained is given for two processes—fading and growing, and some facts elucidating the nature of this effect are considered.

固体飛跡検出器ＣＲ‐３９におけるＡｇｉｎｇとＦａｄｉｎｇの影響

The effect of storage on the track registration property of CR-39 has been studied. Pieces of CR-39 plate were irradiated with normally incident α particles and fission fragments by using a 252Cf source before and after their storage in air for one to six months at different temperatures of -80°C, -23°C, 4°C, 23°C and 35°C. The bulk etch rate and α-track sensitivity were obtained from the etch pit diameters of α and fission tracks. It was shown that the bulk etch rate and the α-track sensitivity both tend to decrease during storage time and from the effect of storage temperatures. The most significant effect was observed on α-track sensitivity at 35°C, which was reduced 55% for six months. It was also shown that the storage effect is attributed not to a fading of latent tracks, but to changes in the detector itself.

Thermal annealing of heavy ion latent tracks in soda and BP-1 phosphate glasses

Annealing behaviour of latent tracks in soda glass has been studied in the temperature range 100–300°C for different time intervals. These latent tracks are created by irradiating these samples with heavy ions viz., 238U (11.4 MeV/u) and 132Xe (11.4 and 5.9 MeV/u) from GSI Darmstadt and 56Fe (4.0 MeV/u) and 48Ti (4.0 MeV/u) from JINR, Dubna. A similar study has been made on Barium Phosphate glass (BP-1) irradiated with 238U (11.4 MeV/u) and fission fragments of 252Cf. The ‘Single Activation Energy’ model proposed by Modgil and Virk (1985) is used as an empirical approach for explaining the thermal fading of these latent tracks. This model always yields a unique value of activation energy of annealing and which is independent of the nature of the ion beam and the degree of annealing. In comparison to this model, Mark et al. (1973) and Green et al. (1985) approach on annealing phenomena has also been used to determine the activation energy. The value of activation energy for annealing of these heavy ion latent tracks is found to be 0.16 and 0.41 eV in soda and BP-1 phosphate glass, respectively. The results of ‘Single Activation Energy’ model are compared with those obtained by using models proposed by Mark et al. (1973) and Green et al. (1985).

Post-irradiation sensitization of CR-39 track detector in carbon dioxide atmosphere

The effect of post-irradiation treatment of CR-39 track detector in carbon dioxide atmosphere on the alpha particle registration sensitivity was investigated. Significant increase in etch rate ratio for 6.1 MeV 252Cf alpha particle was observed. The sensitization increasedboth as a function of trating time and as a function of carbon dioxide pressure in the treating vessel. Energy dependence of the sensitization was found to be small in the 2–9 MeV alpha particle energy interval. Fading of latent tracks after the sensitization process was slow in a one day period. Pre-irradiation treatment in carbon dioxide showed also some sensitization, though to a lesser extent than post-irradiation treatment. However, exposing CR-39 alpha particles in pure carbon dioxide atmosphere resulted in dramatic decrease in sensitivity. The role of dissolved oxygen and carbon dioxide in the primary latent track formation and in post-irradiation latent track transformation is discussed. Potential influence of the application of sensitization of CR-39 in radon, neutron and cosmic ray charged particle dosimetry is also discussed.

新弥彦‐ｌ号井において観察されたアパタイトのフィッション・トラックの消失とその意味

Fission track fading in apatite has been measured in samples from the Shin-Yahiko-1 well, which is situated in a very young sedimentary basin in Japan. Fission track densities were too low to detect confined fission tracks, and consequently semi-track lengths were measured directly instead.Mean lengths and frequency distribution of semi-tracks decrease clearly and progressively with increasing temperature and depth below 4, 400m, and the fading zone of semi-tracks spans an interval of less than 1, 500m, and 40°C in temperature.The smooth trend of fission track fading in the Shin Yahiko-1 well suggests a relatively simple subsidence burial history, which is concordant with the burial history roughly estimated from ages of planktonic foraminifers.From the Shin Yahiko-1 well data, fission track fading over a a very short effective heating time (0.05Ma) delineates a zone on the vitrinite reflectance nomograph.GC/MS analysis suggests that the oil produced from the Shin Yahiko-1 originated from the highly matured Teradomari Formation, which occurs at a depth greater than 4, 500m and roughly corresponds to the top of apatite fission track fading zone.Semi-track length measurement is useful as a supplementary thermal indicator even for very young basins, especially in igneous basement rocks where vitrinites are absent.

Fission track dating of ancient man site in Baise, China, and its significances in space research, paleomagnetism and stratigraphy

A large number of artifacts (stone tools) have been discovered in Baise (Bose), Guangxi, China in recent years. They show that ancient man were living in the south of China during very ancient times. During excavation, tektites were discovered in the same layer of deposits as the stone tools. The structure of the layers of deposits in this site was never disturbed, which is the evidence that the stone tools were left behind by the ancient man at the time when the tektites fell on the earth, which were slowly covered over by layers of deposits. Fission track dating has been carried out on tektites. The age of the tektites is 0.732 ± 0.039 Ma, which is also the age of the ancient man in Baise, Guangxi, China. The annealing degree of spontaneous fission tracks in the tektite was investigated by measuring track diameters. A correction of age for track fading has been made by track diameter technique. According to current understanding, tektites were formed by the impact of falling asteroids or comets on the earth's surface. The dating shows that a big impact occurred on the earth 0.732 Ma ago. The coincidence of the age of the tektites with the age of geomagnetic polarity reversal (∼ 0.73 Ma) from the Matuyama Epoch to the Brunhes Epoch proposes a plausible explanation that the possible cause of the geomagnetic polarity reversal is due to the big impact of space objects falling onto the earth. The result of the dating also set up a standard for inferring the ages of the deposits in South China as well as in South-East Asia where laterite (red soil) deposits exist in the entire region.

Ageing and Fading of Alpha Particle Tracks in CR-39 Exposed to Air

Tests have been carried out on the effects of ageing and fading of alpha particle tracks in CR-39 of the type used in the NRPB area radon detector. The tests showed that there were no significant effects over three months, the normal exposure period for the radon detectors. However, ageing and fading of the CR-39 in air over longer periods resulted in reduced sensitivity.