R.A. Akber

Studies of structural changes produced by high doses of gamma rays in some plastic track detectors

Abstract High gamma doses produce various structural changes in plastic track detectors. This paper describes (a) X-ray diffraction studies, (b) optical transmission measurements, and (c) molecular weight determinations, of CA80-15 and Lexan plastic track detectors which were previously exposed to high doses 60Co gamma rays. There is evidence of decrease of the cellulose nitrate phase as a consequence of dissociation under the influence of gamma radiation. This results in a decrease of both the amorphous phase and the molecular weight. Apparently, there is no effect of gamma rays on the interchain separation of cellulose nitrate. Also, the reaction products such as NO2, HNO3, aldehydes, and ketones seem to be produced in the interaction.

Field experience about the use of alpha sensitive plastic films for uranium exploration

Abstract The paper describes the results of some experiments and field applications of solid state nuclear track detectors for uranium exploration. The experiments were carried out to understand the mechanism of radon diffusion into the tubes containing alpha sensitive plastic films (ASPFs). The effect of position of the film in the tube has also been studied. The effect of background radon levels in the exploration region has been considered and the results of some experiments carried out to simulate the field conditions are reported. A comparison of the results of the gamma surveymetric technique has been made with those obtained by using alpha sensitive plastic films. Finally, the results of an actual field application are reported.

Some important considerations in the use of solid state nuclear track detectors for radon gas concentration measurements

Abstract Experiments have been carried out concerning the usefulness of an alpha sensitive plastic SSNTD for radon gas concentration measurements. In this respect, the effects of factors like (a) radon source concentration, (b) exposure time, (c) size of the tube, and (d) post-exposure handling etc, have been studied. In addition to the alpha sensitive plastic detectors, a surface barrier detector has also been employed to confirm the results. It has been observed that the track density is an increasing but non-linear function of the exposure time and of the size of the tubes containing the detectors. Also, the time required for radon concentration to attain equilibrium in the tubes appears to be dependent upon the strength of the radon source. Theoretical models have been developed to explain this behaviour of the etched track density. These results clearly indicate that the use of these systems for the absolute measurements of radon concentration is not quite straightforward.

14.8 MeV neutron induced fission studies of 239Pu, 242Pu, 244Pu and 241Am

Abstract A Muscovite mica track detector has been employed for the measurement of (a) fission cross-section, and (b) the angular anisotropy of the fission fragments emitted in fission of 239 Pu, 242 Pu, 244 Pu, and 241 Am induced by 14.8 MeV neutrons. A new approach has been tried to extract the above mentioned angular distribution information from experiments carried out in 2π-geometry instead of the conventional vacuum chamber measurements. This has drastically cut down the neutron generator time needed to carry out such experiments. The cross-section and the anisotropy results are found to be in close agreement with those theoretically predicted or reported earlier.

The effect of post-exposure annealing on the track registeration characteristics of CR-39 nuclear track detectors

Abstract The effect of post exposure annealing on the track registeration characteristics of CR-39 (Pershore) Solid State Nuclear Track Detectors has been studied. The changes introduced in the bulk etch rates, track diameter, and the track density have been observed. The results indicate that the bulk etch rate of the detectors and the size of the tracks are considerably changed due to annealing. Variations in the track density are, however, not serious in the presently studied temperature range.

On the use of solid state nuclear track detectors for the measurement of ranges of charged particles

Abstract Attempts have been made to use glass and plastic solid state nuclear track detectors for the measurement of the ranges of fission fragments and alpha particles in air. Both ‘collimated’ and ‘uncollimated’ sources were employed in these determinations. The results of these measurements indicate that the values of the ranges so obtained are in fair agreement but slightly smaller than those obtained by the conventional methods. This can be explained by the finding that the ‘etchable range’ of a charged particle is normally smaller than its ‘true range’ in a track detecting medium.

Radon and thoron dosimetry by plastic solid state nuclear track detectors

Abstract Studies have been made concerning (a) the development and annealing properties of the latent damage trails produced by radon/thoron alpha particles in plastic solid state nuclear track detectors (SSNTDs), and (b) the diffusion properties of radon and thoron in various media by using SSNTDs. The information thus obtained has been employed for (a) the optimization of the conditions for the construction of radon/thoron dosimeters for uranium/thorium mines, and (b) the use of SSNTDs for the prospection and estimation of uranium and thorium. The results indicate that cellulose nitrate detectors, LR-115 and CA80-15, can be profitably employed in dosimetry, prospection, and for the discrimination between uranium and thorium ore bodies.

Double sequential fission events produced in the interaction of 1539 MeV 208Pb ions with natural lead

Abstract The 2π-geometry arrangement of mica track detectors has been employed for the study of multiprong fission events produced in the interaction of 1539 MeV 208 Pb ions with natural lead. Particular attention was given to the analysis of four-pronged events. There is an indication of double sequential fission in the interaction.

A new approach to measure reaction parameters in the 14.8 meV neutron induced fission of 240Pu and 241Pu

Abstract A new approach has been made to use solid state nuclear track detectors in 2π-geometry for studying (a) the fission cross-section, and (b) the angular anisotropy of the fission fragments emitted in the 14.8 MeV neutron induced fission of 240 Pu and 241 Pu. The results of 2π-geometry arrangements have been compared with those obtained by using the conventional vacuum chamber measurements. The results indicate that with proper adjustments, the 2π-geometry method can cut down the accelerator time by at least a few orders of magnitude as compared to that required by the conventional vacuum chamber arrangements. This facilitates the studies of reactions with two yields. The paper also describes the measurements carried out to determine the spontaneous fission decay constants of the above mentioned isotopes of plutonium. Some preliminary values of other fission parameters have also been quoted.

The measurement of radon and thoron by solid state nuclear track detectors

Abstract Experiments have been conducted to study (a) the development and annealing properties of the latent damage trails produced by radon/thoron alpha particles in plastic Solid State Nuclear Track Detectors (SSNTDs), and (b) the diffusion properties of radon and thoron in various media by using SSNTDs. The information thus obtained has been employed for (a) the optimization of the conditions for the construction of radon/thoron dosimeters for uranium/thorium mines, and (b) the use of SSNTDs for prospection and estimation of uranium and thorium. The results indicate that these gases can diffuse even through rocks, and cellulose nitrate detectors, LR-115 and CA80–15, can be profitably employed in dosimetry, prospection, and for the discrimination between uranium and thorium deposits.