الفهرس 
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Abstract
CR-39 track detectors have wide interest in many fields of science and technology due to their low cost, relatively easy handling and being more similarly to human tissue than other passive detectors.
This solid state detector of nuclear radiation is used to learn more about frequently cosmic rays, long-standing radioactive elements, radon concentration in houses, and the age of geological samples. Moreover, it has a high efficiency on detection of alpha particles (0.5-20 MeV).
In this thesis, we study the effect of alpha radiation on polymeric material (CR-39), by investigation the physical properties (optical properties, electrical properties and the structural properties) of CR-39 before and after irradiation process. Furthermore, the effect of irradiation positions on the microstructure of CR-39 polymer was investigated. At first, the irradiations of CR-39 samples were performed by using 241Am at constant alpha particle energy 4.86±0.22 MeV in normal position for different periods of times (6 - 96) hours, the other samples of CR-39 were irradiated by using 241Am at constant alpha particle energy 4.28±0.22 MeV at normal and inclined incident for the same fluence.
The data in the normal incidence radiation showed a formation of chain scission at low fluence. This scission was increased with increasing fluence. Positron annihilation Doppler-broadening technique was used to study the effect of irradiation α-particles emitted from 241Am (4.86±0.22 MeV) source on the line shape S- and W-parameters for CR-39 samples.
The results showed the formation of defects in CR-39 samples after irradiations, and good correlation between S- and W-parameters with correlation coefficient r = 0.99 for the sample at irradiation times (6, 24 and 72 hrs). Additionally a correlation was existed with correlation coefficient r = 0.72 between the optical band gap energy (Eg) and S-parameter. Extended system of conjugated bonds due to irradiation was noticed.
The obtained results were discussed and compared with other literature data and they showed an agreement with these results to some extent.
The effects of α-particles with different positions (normal and inclined) on the structural properties of CR-39 polymer were investigated. X- ray diffractions were performed on irradiated and non-irradiated CR-39 samples in order to study the structure of samples. A noticeable change in the crystallinity was appeared at the normal incidence position. Accordingly, the normal incidence increases ordering of the original lamellar structure of CR-39 polymer.
Positron annihilation Doppler-broadening technique was used to study the effects of irradiation α-particles on the line shape S- parameters for CR-39 samples. We found that the S-parameter for the normal irradiation is greater than that in the inclined. Therefore, normal incident irradiation plays a vital role in making defects in CR-39 samples.
Furthermore, a strong correlation was existed between the crystallinity and S-parameter with correlation coefficient r = 0.87. Moreover, with correlation coefficient r = 0.99, we found a good correlation between S-parameter and W-parameter as.