3 MeV protons to simulate the effects caused by neutrons in optical materials with low metal impurities

In this paper we tested an optical material which more recently has been introduced in the commercial area (KU-1). The outstanding optical qualities in the 190+2500 nm and their enhanced resistance to ionizing radiations are making them appropriate as shield for attenuation of degradation over time of optical systems such as commercial color cameras when they must operate in hostile radiation environments. This type of optical glass (KU-1) is a promising candidate to replace the most common type of optical glass BK-7 (330+2100 nm) associated optics equipment affected by cosmic radiation or nuclear areas. In this direction we exposed different samples of this type of optical glass at a 3MeV energy protons flow. The spectrophotometer measurements have revealed the effect of protons irradiation as the degree in change in optical transmission in the visible region of the electromagnetic spectrum (350+850 nm). Measurement results, post-irradiation, have revealed a reduction in the optical transmission of the samples especially in the blue region of the visible spectrum. Our interest focused on the behavior of the KU-1 glass samples in central wavelengths for spectral areas corresponding to the three primary colors (blue 473 nm, green 533 nm, red 685 nm) which are responsible for the accuracy of transmitting images using color cameras. Since the proportions of those color signals builds the entire color range of the resulted images, damaging any of them in the irradiation process will lead to overall deterioration of the image. In our case, the radiations have affected the blue component (11.7%), followed by the green (11.3%) and the red (10.0%). Although our main goal was to test the optical glass type KU-1 at proton energy of 3MeV in the visible part of the spectrum, we obtained additional information from the irradiation with protons of 13MeV energy and gamma ray having about 1.25MeV in other area of the electromagnetic spectrum such as ultraviolet and infrared. Checking of the IR behavior is important because the digital cameras are also sensitive even in this spectral region. This ability is useful in fusion experiments to monitor hot spots of the enclosure in which plasma is formed. The paper also shows the best fitting curves and their associated relationships that describe analytically the causal relationship between absorbed dose and change in optical transmission. These analytical relationships allow us to estimate the optical transmission that we can expect for different absorbed doze values in the range of 0+10MGy.