I.E. Qureshi

Studies of CR-39 etch rates

Abstract A series of chemical etching experiments have been carried out on CR-39 detectors irradiated with fission fragments of 252 Cf to study the bulk and track etching characteristics. Experimental data has been analyzed to find out important track etch parameters. Both bulk and track etch rates are found to follow the Arrhenius equation which gives the variation of etch rate with temperature for a specific set of etching conditions. Activation energies for bulk and track etching have been determined by fitting Arrhenius equation to the experimental data. Other track etch parameters, e.g. critical angle of etching and track registration efficiency have also been determined using experimental data. Track etch parameters depend on properties of incident ion and etching conditions. Results describing the dependence of track etch parameters on etching conditions have been presented. These results are useful in the interpretation of track data.

Thermal annealing of fission fragment radiation damage in CR-39

Abstract The annealing behavior of fission fragment tracks in CR-39 has been studied at different temperatures for various time intervals. Experimental data, obtained in isothermal and isochronal annealing experiments carried out on CR-39 irradiated with fission fragments of 252 Cf, has been analyzed on the basis of different annealing models. It has been attempted to find out the validity of these models, developed on the basis of annealing data in minerals and other detectors, to the annealing data of fission fragment tracks in CR-39.

Kinematical analysis of 2-, 3- and 4-body channels in the reaction (12.5 MeV/u) 84Kr + natU observed with mica track detectors

Abstract The exclusive measurements of reactions induced by 1050 MeV 84 Kr ions incident on natural uranium have been made with the help of mica track detectors used in a 27 π -configuration. The cross sections for ternary and quarternary events have been determined by directly counting the numbers of events of relevant multiplicities. The angular distribution in the case of elastic events has been fitted by a generalized Fresnel model with parameters θ 1 4 ( c.m. ) = (33.5 ± 0.5)° and Δ = 8.5 ± 5. A complete kinematical picture of the reaction process has been deduced by converting the three-dimensional track parameters (lengths and angles) into parameters of reaction products (masses and energies) on an event by event basis. An empirical velocity-range relation has been used for this purpose, which has been obtained by an internal calibration procedure. It has been found that the reaction mechanism for the bulk of the data can be described as a sequential fission process. However, non-equilibrium effects appear for a small number of events (about 8%) in the three-body channel and completely dominate the four-body channel. In order to estimate the uncertainties of the computed quantities in relation to the measurement errors, Monte Carlo simulation of the selected data sets has also been performed.

Swelling in CR-39 and its effect on bulk etch-rate

Abstract The effect of swelling in CR-39, during the etching process has been studied using ‘thickness-measurement’ method. The values of the bulk etch-rate ( V B ) determined by this method have been corrected in the context of irreversible swelling produced in various CR-39 samples. The results have been compared with those obtained using the ‘mass-measurement’ as well as the ‘fission fragment track diameter’ methods. The values of experimental V B have been obtained by taking the arithmetic average as well as by fitting the Gaussians to the results of a number of CR-39 samples. It is shown that the ‘thickness-measurement’ method is as good as the other methods of determining the bulk etch-rate provided sufficiently large number of CR-39 samples are used for obtaining the mean value from the Gaussian fit of the experimental data.

Activation energy for the annealing of nuclear tracks in SSNTDs

Abstract Annealing characteristics of fission fragment tracks in CR-39 have been studied to find out the activation energy. Published annealing data sets of different ions in CR-39 and various other detectors have also been re-analyzed to study the dependence of activation energy of annealing on different factors involved in the process. This analysis shows that the activation energy of annealing depends mainly on the characteristics of the detector material but it may have weak dependence on the parameters of track forming ion and annealing conditions.

Experimental and simulation study of neutron dosimetry at various neutron energies

Abstract A Monte Carlo Neutron Photon (MCNP) transport code has been employed to simulate CR-39 plastic track detector as neutron dosimeter at various neutron energies. In each simulation a monoenergetic neutron source of a particular energy was embedded in the center of a sphere made of CR-39. Surrounding the source there were concentric shells of 2 μm CR-39 track detectors. The code, MCNP, was run on personal computer for 7.5×106 histories. The number of proton recoils in each shell of 2 μm of CR-39 were determined. The simulation results show that apart from proton recoils (for En > 1.0 MeV), about 50% recoils are due to heavy charged particles i.e. Oxygen and Carbon in CR-39. This indicates that etched tracks are not only due to recoil of protons but also due to recoil of heavy charged particles. The upper limits of the track registration efficiencies have been determined as a function of neutron energies. These simulation results have been experimentally verified using CR-39 track detectors at various known energies of neutrons. The proton and heavy charged particle recoil tracks in CR-39 were made visible by etching in NaOH solution, at 70±1°C for 1.75 hours.

Fission Track Estimation Of Uranium Concentrations In Drinking Water From Azad Kashmir, Pakistan

Abstract— The analysis of uranium in water samples can be very helpful for providing guidelines to the general public regarding necessary remedial measures. A fission-track technique has been applied for the estimation of the uranium concentration in drinking water collected from natural springs of Muzaffarabad and hilly areas of Reshian, Azad Kashmir. The technique involved simultaneous irradiation with thermal neutrons of a sample and a standard in contact with a track detector, and the counting of the fission tracks in the detector from the (n, f) nuclear reaction. Uranium concentrations of the samples were determined by comparing fission-track density with that of a standard of known uranium concentration. Uranium concentration in water samples from the Muzaffarabad and Reshian area varied from 0.03 ± 0.01 &mgr;gL−1 to 6.67 ± 0.14 &mgr;gL−1 with an average of 1.36 ± 0.05 &mgr;gL−1. The observed concentrations of uranium in drinking water were found to be less than the Maximum Acceptable Concentration levels of 9–30 &mgr;gL−1. Thus, the observed values are within safe limits as far as uranium related health hazards are concerned.

On the use of SSNTD in relativistic heavy ion physics and the study of open questions

Abstract Taking an historic perspective on the development of relativistic physics in general and relativistic heavy ion physics in particular, it can be shown that many observations were first made with nuclear emulsions and other SSNTD detectors, later confirmed with conventional counter techniques and/or radiochemical techniques. It is quite possible that SSNTD can make similar contributions when studying the open and controversal problems of today. In this article we consider the anomalon phenomenon as to be one such problem.

A quick method for maintaining the molarity of NaOH solution during continuous etching of CR-39

Abstract A series of experiments have been performed to investigate the physio-chemical changes that occurred in the 6 M NaOH solution after etching CR-39 (Pershore and Homalite) detectors, each for 3, 6, 9, 12 and 15 h . Various physical parameters like concentration, electrical conductivity (EC) and density of the solutions have been measured after each etching interval. Results have been discussed in the light of stoichiometrical equation for the interaction of CR-39 with NaOH. It is found that the concentration, EC and the density of the solution, in which CR-39 has been etched, increase linearly with respect to the etching time. The inter-relationship of EC–concentration and density–concentration suggest that the concentration of the etchant can be maintained at certain desired value by adjusting the corresponding value of EC or density, measured through non-destructive and quick methods.

Pion-induced fission in tin and bismuth observed with makrofol detectors

Pion is the field particle of nuclear force. Its interaction with the nucleons may lead to complete absorption resulting in the full deposition of the rest mass and kinetic energy within the nucleus. Consequently the nucleus can be excited to very high energies. This situation gives rise to binary decay even in those nuclei which are not normally prone to fission due to their high fission barriers. We have studied the occurrence of binary fission induced by pions of energies 500, 672, 1068 and 1665 MeV in the targets of Sn and Bi. The exposures have been made at the Brookhaven National Laboratory (USA). The experimental set-up was based on 2π-geometry with targets in the form of thin foils placed in front of Makrofol detectors. The fission events were counted manually with an optical microscope. The incident beam was monitored with the help of a scintillator and local fluences were determined in-situ. The fission cross-sections were calculated by using the known values of target thickness and local frequencies of fission counts.