ON SOME REGULARITIES IN THE CHANGES IN THE PROPERTIES OF GLASSES UNDER THE ACTION OF IONIZING RADIATION

V. G. VAKHROMEEV, V. A. STARODUBTSEV, E. K. ZAVADOVSKAYA

A study has been carried out of the influence of proton irradiation on glasses. After irradiation with a dose of \(7.5 \cdot 10^{15}\) protons/cm\(^2\), the amount of stored energy was \(3.6\) cal/g. An increase in microhardness after irradiation was found, and two maxima are observed in the optical absorption spectrum.

It was researched an influence of the proton irradiation on glasses. The quality of storage energy was \(3.6\ \frac{\text{kal}}{\text{g}}\) after irradiation of the dose \(7.5 : 10^{15}\ \frac{\text{proton}}{\text{cm}^{-2}}\). Microhardness was increased after irradiation and two maximums was watched in the Spectrum of the optics absorption.

In the present work we present the results of investigations carried out by us of changes in the microhardness, optical absorption, electrical resistance, and stored energy in sodium–calcium silicate glasses after proton irradiation. Investigation of the changes in the complex of properties of glass after irradiation makes it possible to judge its radiation resistance.

Irradiation was carried out in air, at room temperature, with protons of energy on the order of \(4.5\) MeV. The most complete characteristic reflecting the changes that have occurred in the body after irradiation is the stored energy. By the annealing method in a calorimeter [1], we measured the stored energy in glasses after irradiation with \(7.5 \cdot 10^{15}\) protons/cm\(^2\). At this irradiation dose, the amount of energy released was \(3.6\) cal/g. After irradiation, the microhardness of the glasses increases. The change in microhardness with the dose of proton irradiation (Fig. 1) follows a curve with saturation. The increase in microhardness at a dose of \(7.2 \cdot 10^{15}\) protons/cm\(^2\) is about 3%; moreover, at small irradiation doses the change in microhardness is insignificant, while beginning with a dose of \(3.6 \cdot 10^{15}\) protons/cm\(^2\) a sharp increase in microhardness is observed. After irradiation the glasses have a light-brown coloration. The optical absorption spectrum reveals two maxima, at 550 and 440 nm (Fig. 2).

At the given irradiation doses no substantial change in electrical conductivity is observed; a slight increase in dielectric losses is found in the relaxation region.

Holding the samples at a temperature of \(100^\circ\text{C}\) for one hour leads to annealing of the defects that cause the increase in microhardness. The optical absorption spectrum of the glasses after annealing shows the disappea—

the absorption band with a maximum at 550 nm and a decrease in the maximum of the absorption band at 440 nm. From a comparison of the facts given above, it may be assumed that the change in microhardness after proton irradiation is associated with color centers.

Fig. 1. Dependence of the change in microhardness in glass on the dose of proton irradiation

It is assumed [2] that the band with a maximum at 550 nm is due to \(A\)-centers. Since annealing for one hour leads to the destruction of this band and removes the strengthening effect, it may be said that

Fig. 2. Optical absorption spectrum of irradiated glass.
1 — after irradiation with a dose of \(7.2 \times 10^{15}\) protons/cm\(^2\). 2 — after irradiation and subsequent annealing at \(100^\circ\)C for 60 min

the change in microhardness after irradiation is associated precisely with this type of defect.

Conclusions

1. After proton irradiation, an effect of energy storage by glasses is observed owing to the formation of defects in them.

2. The stored energy per gram of irradiated glass is 3.5 calories.

1. Proton irradiation causes an increase in microhardness.
2. The change in microhardness with the dose of proton irradiation has a saturation character at high doses.

References

1. E. K. Zavadovskaya et al. PTE, No. 5, 215, 1966.
2. T. O. Karapetyan et al. FTT, 6, 5, 1964.