A. Ahmed Morsy

Electrical, optical and structural behaviour of fast neutron-irradiation-induced CR-39 SSNTD

Abstract The effect of fast neutron irradiation on the electrical, optical and structural properties of CR-39 diglycol carbonate, solid state nuclear track detector, was investigated. DC conductivity measurements were studied in the temperature range 293–413°K using solid state samples of the CR-39 polymer. These samples were exposed to neutrons of initial energy levels between 0.8 and 19.2 MeV . Furthermore, the activation energy was measured, at various temperatures, as a function of the neutron energy. It was found that many changes in electrical resistance of CR-39 polymer could be produced by neutron irradiation via the degradation mechanism. Also, at the energy range 6– 19.2 MeV the neutron irradiation causes branching that reduces crystallinity and induces further lattice defects that may act as scattering centers and energy barriers for the flow of electric current. Moreover, optical and structural property studies using refractive index measurement and X-ray diffraction were performed on irradiated and non-irradiated CR-39 samples. The results indicate that the neutron irradiation in the energy range 6– 12.26 MeV enhances the isotropic nature of the CR-39 polymer samples.

An optical method for fast neutron dosimetry using CR-39

Measurements of the neutron doses in and around its sources are important for the purpose of personal and environmental neutron dosimetry. In the present work, we investigate a method for the measurement of neutron dose using the ultraviolet–visible (UV–VIS) spectra of an irradiated CR-39 plastic track detector. Therefore, a set of CR-39 plastic detectors was exposed to a source of fast neutrons, which has a yield of 0.68×108 s−1, and the neutron equivalent dose rate 1 m apart from the source is equal to 0.038 mSv/h. The samples were etched for 10 h in 6.25 N NaOH at 70±0.1 °C. Using the UV method, changes in the UV–VIS spectra of CR-39 with different neutron doses were obtained and the absorbance of the etched samples was measured using a UV–VIS spectrophotometer as a function of neutron dose. Further, it is observed that there is a linear relationship between the optical absorption of these detectors and neutron doses. Hence, the linear graph can be used as a calibration to measure the unknown dose of neutrons by knowing the optical absorption of the sample. These results are compared with previous work, and in principle, there is a good agreement with their investigations.

Radiation-induced changes in some SSNTDs

A comparative study of the effect of fast neutrons and alpha particles on the color changes of some solid state nuclear track detectors was performed. Samples from CR-39 diglycol carbonate and Makrofol polycarbonate were classified into two main groups. The first group was exposed to neutrons of energies in the range between 4.4 and 19.2 MeV, while the second group was irradiated with alpha particles of initial energies in the range between 5.1 and 34 MeV. The transmission of these samples in the wavelength range 200–2000 nm, as well as any color changes, was studied. A characteristic transmission band with different intensities in the wavelength range 200–2000 nm was observed when the samples were exposed to alpha particles, while the interaction of fast neutrons on these detectors, CR-39, may lead to the appearance of new transmission bands at some particular wavelengths. Using the transmission data, both the tristimulus and chromaticity coordinate values were calculated. In addition, the color differences between the non-irradiated sample and those irradiated with different neutron or alpha doses were calculated. The results indicate that both CR-39 and Makrofol detectors acquire color changes under fast neutrons or alpha particles irradiation, but the Makrofol detector has more response to color change than CR-39.

Measurements of environmental radon-222 concentration in indoor and outdoors in Egypt

Abstract The major contribution to population exposure from natural radiation arises from the inhalation of the decay properties of radon. Substantial surveys 4 are being conducted by several investigators to estimate the indoor and outdoor exposure nationally and to discover regional variations. In this work radon concentration in the indoor and the outdoor air was determined using the can technique and employing CR-39 SSNTD for exposures. The range of 222Rn activity in this survey was 2–11 Bq.m −3 in Cairo, 0.81–6.3Bq.m −3 in Alexandria and Aswan and Sinai ranged between 3.6–15.2 Bq.m –3 . Values of indoor and outdoor radon concentrations were found to vary with time of day, geographic location, season and height above the ground.

Variation of the track etch rates of alpha-particle trajectory in PADC

The formation of etched tracks in solid-state nuclear track detectors is usually described by assuming an unequivocal correlation of the etch-rate ratio with the energy loss of charged particles. For alpha particles, this assumption could be verified within the scatter of the experimental data. In this article, the dependence of the depth (x) on the track etch rate (V T) was determined experimentally by track length measurement. It is found that the track etch rate as a function of the depth within the detector follows the Bragg curve. The track etch rate has been found to be described by a generalization of the restricted energy loss, in good approximation along the trajectories of alpha particles.

Radon measurements in the interior of the great pyramid

Abstract Radon concentration measurements were made in the interior of the great pyramid of “Cheops” at Giza. Measurements were carried out using CR-39 as solid state nuclear track detector. The CR-39 sheets were placed inside the Queens and Kings chambers and along the ascending corridor leading to it. Evaluation of radon concentration is presented and discussed.

Variation of the track length along the particle trajectory through CR-39 stack sheets

An alpha track was selected through a number of successive CR-39 sheets in a high energy nuclear reaction experiment. The experiment was aimed at identifying particles emitted at an angle of 25° to the beam direction when bombarding a copper disk with relativistic fluorine ions. Most of these particles were identified as protons and alpha particles. The experiment showed that the inlet energy of an alpha particle to be detectable in CR-39 plastic is 53.4 MeV per nucleon. The CR-39 range of such particles is ∼2 cm long. The corresponding range for a proton is ∼1 mm long. The track diameter at positions on the track length can display the damage as a function of the depth in the CR-39 material. In addition, the track length is measured along the particle trajectories in CR-39 sheets for a single track as a function of residual range in the CR-39 material. The restricted energy loss (REL) for alpha tracks in CR-39 is calculated using the Henke–Benton computer program. Comparison between the REL and the damage was available along this track, especially owing to the ability of CR-39 to prevail etched tracks.

Central cord syndrome

Spinal cord injuries (SCIs) are classified as complete or incomplete injuries. Central cord syndrome (CCS) is the most common type of incomplete SCI. The syndrome mostly occurs in older individuals with underlying cervical spondylosis caused by a hyperextension injury. The neurological impairment is characterized by a disproportionate weakness of the upper extremities more than the lower extremities and may also include bladder dysfunction and varying degrees of sensory loss. The natural history of the syndrome varies, with some patients experiencing complete spontaneous recovery and others having persistent neurological deficits. The role of surgical intervention remains controversial. We present a case of an elderly patient with cervical spondylosis who underwent thoracolumbar spine fixation and was complicated by CCS mostly due to hyperextension injury during surgery.