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1.
Experimental studies on track etch rates in CR-39 performed with protons, deuterons and alpha particles as well as 7Li, 11B and 12C ions were extended to 14N and 16O ions. The results are compatible with the general systematics found for the dependence on the kind of ion and its initial energy. Analysing the etch rate ratios as function of the restricted energy loss (REL), the non-existence of a unique relationship has been confirmed. However, assuming a dependence of the etch rate ratio not only on REL, but also on the depth within the detector where a given REL value occurs, all experimental data could be adjusted. The experiments with 14N and 16O ions allow extension of the REL range studied up to about 14 000 MeV/cm. The whole area relevant to neutron-induced charged particles generated within the CR-39 detectors is covered thereby. Having added the data for 14N and 16O ions, the array of curves for the etch rate ratio could be expanded up to 14 000 MeV/cm without inconsistencies, demonstrating the compatibility of the new data set also quantitatively. 相似文献
2.
At the beginning of the etching process a constant track etch rate can be assumed. In deeper detector layers, however, the etch rate varies drastically along the particle trajectories. Consequently, the indirect determination of the track etch rate by measuring the etch pit diameters on the detector surface does not yield correct results. Therefore, a method for the direct measurement of the track etch rate as a function of the depth within the detector was developed. Applying this method, the relationship between the track etch rate and the energy loss in CR-39/PATRAS could be derived. 相似文献
3.
Computation of etched track profiles needs the knowledge of the variable track etch rates along the ion trajectories. Using the depth-dependent track etch rates experimentally determined for perpendicularly incident protons, deuterons and alpha particles as well as 7Li, 11B, 12C, 14N and 16O ions of different energies simulations of the track development were performed. Two models of track etching were applied for that purpose recently published in literature. Although the models are based on the same physical fundamentals the results are slightly different. The reasons of the discrepancies were found by analysing the algorithms in detail. Comparison of the calculated track profiles with those determined experimentally from longitudinal sections of the etch pits showed good agreement for non-overetched as well as overetched tracks. The consistency of the whole experimental data set was checked by analysing the correlation of the track etch rates with geometric track parameters for all kinds of ions and etching times covered by the experiments. 相似文献
4.
It is well established that the bulk etch rates for solid state nuclear track detectors are affected by the concentration and the temperature of the etchant. Recently, we found that the bulk etch rate for the LR 115 detector to be affected by stirring during etching. In the present work, the effects of stirring on the bulk etch rate of the CR-39 detector is investigated. One set of sample was etched under continuous stirring by a magnetic stirrer at 70°C in a 6.25 N NaOH solution, while the other set of samples was etched without the magnetic stirrer. After etching, the bulk etch thickness was measured using Form Talysurf PGI (Taylor Hobson, Leicester, England). It was found that magnetic stirring did not affect the bulk etch of the CR-39 detector, which was in contrast to the results for the LR 115 detector. 相似文献
5.
The calculation of the response of CR-39 detectors exposed to neutrons is of high importance for their dosimetric application. A computer code system has been developed for this purpose. Whereas the generation of secondary charged particles is carried out using non-analogue Monte-Carlo techniques with variance reduction the simulation of the track formation process is treated without any free parameter starting from the etch rate ratio V(REL) only. Results are given for the contribution of recoil protons to the response as a function of the neutron energy and angle of incidence. Furthermore, the influence of an external radiator has been studied. The comparison of the calculated values with experimental data confirm the reliability of the track etch model applied. 相似文献
6.
The depth-dependent bulk etch rate has been examined for the gamma-irradiated CR-39 at doses ranging from 20 to 100 kGy. The thickness of the damaged region in gamma-irradiated CR-39 plastics, in which the bulk etch rate was significantly enhanced, was found to be limited in the thin layer near the surface and decreases with increasing the dose-rate, while it barely depend on the total dose. This indicates that it is possible to apply CR-39 plastics as high dose gamma-dosimeter by assessing both the bulk etch rate in the damaged region and its thickness in principle. 相似文献
7.
Analysis of etched nuclear tracks in CR-39 solid state nuclear track detectors has recently been made possible by the confocal microscope. This recent innovation has opened up some particularly interesting perspectives. The main originality of this microscopy technique is that it makes it possible to work on numerical, three-dimensional images of chemically etched nuclear tracks in the CR-39. We have studied the performances of this new approach for light ions (H, He, Li and C) with kinetic energies typically of the order of the MeV per nucleus. First, we determined the response functions of the CR-39 for these ions. We were then able to show that aside from decreasing the analysis time of traditional methods, the confocal microscope greatly increases the sensibility of the detection. The aim of this study was to find a correlation between the response functions and the primary physical parameters of the interaction between the ion and the material, such as the linear energy transfer (LET), the restricted energy transfer (REL ω0), the integrated radial dose or the rate of ionization. Although these parameters presented a strong resemblance to the experimental response functions (they are all “Bragg” curves), none of them were correlated to the response function in an unambiguous way. 相似文献
8.
Etching rates along tracks of protons and lithium ions with energies in the Bragg peak region were explored. The energy losses in this region, especially for protons of low energies, are of particular interest from the physical as well as biological points of view. The microscopic track etch rate, VT, is studied using the many-hit model in its first approximation assuming that VT is a function of the restricted energy loss (REL ω). The ions multiple scattering and straggling effects on the average experimental VT values are corrected by shifting the calculated REL ω values along the track, until its maximum coincides with that of the VT. The fitting of least square differences between calculated and experimental VT values is used in order to determine the many-hit model registration parameters for the detector under investigation. 相似文献
10.
Computation of the neutron response of CR-39 detectors needs to simulate the track formation by neutron induced charged particles taking into account the bulk etch rate and the track etch rate varying along the particle trajectories. The latter one was determined experimentally by track length measurement. The results allowed to derive the relationship between the track etch rate and the restricted energy loss of the charged particles. On this basis, the geometrical track parameters and track etch rates as well as the critical angle of particle incidence could be determined for protons and alpha particles in the energy range from 0.2 to 8.8 MeV. The energy dependence of the critical angle enabled to determine the detection efficiency for a charged particle of given energy and direction. 相似文献
11.
The effect of infrared radiation on the etching characteristics of CR-39 plastic track recorder has been studied. CR-39, which is commonly employed in cosmic rays studies is found to be affected by IR radiations. The changes in the bulk etch rate, in the track etch rate and in etching efficiency due to infrared radiation exposure of CR-39 are discussed on the basis of scission and cross linking during infrared exposure. 相似文献
12.
In previous investigations the formation of radicals induced by γ-irradiation in CR-39 samples has been studied by electron spin resonance (ESR) spectroscopy. On the other hand, all attempts fail to detect radicals in samples irradiated by particles (p, and neutrons). The present work succeeded in detection of radicals produced by charged particle radiation in CR-39 (TASTRAK). The detectors were irradiated with protons of 7 MeV and -particles of 3 MeV with fluences in the order of 10 11–10 12 particles/cm 2. The observed ESR signal is composed of at least four different resonance lines for each of which we determined the amplitudes, g-factors, lifetimes and the G-value. The amplitude of the total ESR signal decreases rapidly with a short and a longer lifetime. About 5 days after irradiation the ESR intensity decreased to an undetectable value. The lowest detectable dose (LDD) is of the order of 1 kGy. 相似文献
13.
Yields of CO 2 gas formation and the scissions at ether bonds have been determined along ion tracks in CR-39 plastics. Thin CR-39 films with thickness were irradiated by 130 MeV C-13 ions at 45 incidence up to , and then IR spectra were obtained without removing the samples from the vacuum chamber. The absorption band for CO 2 was observed clearly around , whose absorbance increased proportional to the fluence up to 3×10 12 ions/cm 2 and then saturated. Using a mole absorption coefficient for gaseous CO 2, the yield along the track was determined to be molecules/μm. This means that the G-value of CO 2 formation in CR-39 was about 3.6 molecules/100 eV. The scission yield of ether bonds was found to be 11,000 scissions/μm. This corresponds to a G-value of about 5.5 scissions/100 eV. These values suggest that the parts between the two carbonate ester bonds in each repeat unit of CR-39 can be segmented into two CO 2 and other small molecules along the nuclear tracks. 相似文献
14.
The effect of gamma-rays and pulsed electrons has been investigated on the bulk etch rate of CR-39 detector at doses up to 100 kGy under various dose-rate between 0.0044 and 35.0 Gy/s. The bulk etch rate increased exponentially with the dose at every examined dose-rates. It was reveled to be strongly depend on the dose-rate: the bulk etch rate was decreased with increasing dose-rate at the same total dose. A primitive model was proposed to explain the dose-rate effect in which oxygen dissolved was assumed to dominate the damage formation process. 相似文献
15.
For the last few years, the Besançon and Dresden teams have been working in a parallel way on light ion (protons and alphas) registration characteristics for the CR-39 SSNTD. Even if the two groups use different approaches, the main part of both investigations concerns the study of the track etch rate (V T) and the consequences of the obtained results, which have provided us with greater understanding of detection limits. After recalling the methods used to determine the VT from both teams, will show how fundamental datal related to the registration properties of the CR-39 detector can be extracted. Indeed, the knowledge of an analytical relation for the VT enables the relationship between this velocity and the primary deposited energy to the examined with respect to the same spatial variable (the instantaneous depth of penetration (x) of the incoming particle). According to experimental uncertainties, the Bragg peak of the primary ionization coincides within a very close range with the maximum of the VT. Moreover, if increasing the etching parameters (C, T) increases the maximum VT value, these changes do not affect its position with respect to the instantaneous depth of penetration. Taking into account the reduced etch rate, the Dresden team found that both protons and alphas exhibit the same behavior when this rate is plotted versus the primary energy deposition rate. As a consequence, the corresponding reduced etch rate is always identical no matter what type of particle deposits a given amount of energy (e.g. proton or alpha). The Besançon team has corroborated the results obtained by the Dresden group for alphas and have extended the study to various etching conditions. From these results, the sensitivity of the CR-39 SSNTD is obtained in terms of critical LET and leads to a very low energy threshold for alpha particles. We will see throughout this paper that the lower threshold does not seem to depend on the etching parameters. 相似文献
16.
Solid-state nuclear track detectors have found wide use in various domains of science and technology, e.g. in environmental
experiments. The measurement of alpha activity on sources in an environment, such as air is not easy because of short penetration
range of alpha particles. Furthermore, measurement of alpha activity by most gas ionization detectors suffers from high background
induced by the accompanying gamma radiation. Solid state nuclear track detectors (SSNTDs) have been used successfully as detecting
devices and as a passive system to detect alpha contamination on different surfaces. This work presents the response of CR-39
(for two types) to alpha particles from two sources, 238Pu with energy 5 MeV and 241Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency
and reproducibility. The sensitivity to low activity and energy resolution are studied.
相似文献
17.
A review was given for our recent studies on the latent tracks in CR-39 nuclear track detector. The radial size of track core has been determined through UV spectral measurements combined to the model of track overlapping and by AFM observations of slightly etched detectors. The track core radius was found to be about a few nano-meters and almost proportional to the cubic root of stopping power. As a control study, the etching properties of CR-39, irradiated by low-LET radiation, has been examined. The observed depth dependence and dose-rate dependence of the bulk etch rate of the irradiated CR-39 were explained that the damage formation process was governed by the reaction between the radiation induced radicals and the oxygen supplied from the air. This indicated that latent tracks in CR-39 are produced through local radiation induced oxidation process along the ion paths. Studies on vibration spectra, near-IR, FT-IR and Raman spectra, of CR-39 have also been carried out to estimate the chemical structure of the latent tracks. The creation of OH group in irradiated CR-39 has been confirmed. 相似文献
18.
In this paper, the previous modeling of protons and alpha particles tracks depth in CR-39 nuclear track detectors was extensively extended to describe tracks of heavier ions. These ions include deuteron, lithium, boron, carbon, nitrogen and oxygen. Based on a compilation of published experimental results related to these ions, a set of empirical fitted model parameters is obtained for each type of ion. The A dependence of these model parameters is obtained. 相似文献
19.
This paper presents the results of the influence of soft X-ray radiation on craters induced in SSNTDs by energetic α particles and protons of energy in the MeV range. We checked two detectors of the PM-355 and CR-39 types in order to verify and compare their resistance to the harsh conditions of high-temperature plasma experiments. To determine this effect some detector samples were first irradiated with α particles emitted from natural α particle sources and protons delivered by a particle accelerator. After that these samples were exposed to soft X ray radiation emitted from an X ray tube and also from the PF-1000 Plasma Focus facility. Doses during X ray irradiations varied from 0 up to tens of kGy. The irradiated samples were then etched in steps and track diameters were determined versus the absorbed dose and etching time and compared with those measured in samples not exposed to X ray radiation. 相似文献
20.
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. 相似文献
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