Mechanism Research On Radiation Damage Of GG17 Glass And Rubidiuim Loss For Rubidium Spectral Lamp

Factors of affecting the rubidium spectral lamp performance were analysed systematically, and the corresponding experiments were performed under the background of engineering application. Radiation effects caused by protons and electrons with various energies were investigated for the GG17 borosilicate glass as envelope materials of rubidium spectral lamps. The mechanisms of radiation-induced defects were investigated. The glass envelope of rubidium spectral lamps under the conditions of RF discharge and various temperatures was analysed, and the chemical reaction between rubidium and glass envelope was characterized. The spectral performance of rubidium spectral lamps was investigated and the parameter range of ring mode was identified.Experimental results show that the electron irradiation, proton irradiation and simultaneous irradiation of electrons and protons affect the optical property of GG17 glasses to some different extent. The optical degradation of GG17 glass irradiated by electrons and higher energy protons is evident, especially 1MeV electrons with the fluence of 1016/cm2 could induce a spectral transmittance decrease over 18% at the rubidium D lines (780nm and 794.6nm). In comparison, lower energy protons have a weak effect on the rubidium D line. The optical change results from a number of radiation-induced color centers. The results show that the main type of radiation defects is the oxygen hole center, determined by Electron Paramagnetic Resonance and Fourier Transform Infrared Spectroscopy. Electrons and higher energy protons mainly induce ionizing effect and the major defects are boron-oxygen hole centers. Lower energy protons mainly induce displacement effect and the primary defects are silicon-oxygen hole centers and boron-oxygen hole centers. The formation model of oxygen hole centers was presented for various irradiation conditions. The boron-oxygen hole centers induced by electrons and higher energy protons are due to holes trapped on bridging oxygens, while for lower energy protons as a result of holes trapped on non-bridging oxygens.Rubidium lamp serves as an optically pumped sources under a certain temperature and RF voltage. Heating and RF discharge for a long time could cause an interaction of the rubidium and glass envelope, including the rubidium diffusion into the glass envelope and the chemical reaction of rubidium and glass envelope, leading to rubidium loss. Both the diffusion and chemical reaction strongly depend on temperature and RF voltage. Rates of chemical reaction and rubidium diffusion are enhanced with increasing temperature and RF voltage. The rubidium diffusion process is examined by secondary ion mass spectra, X-ray photoelectron spectra and back-scattered diffraction analysis, giving rubidium profile distribution along glass wall for various work conditions. The main products of chemical reactions are rubidium-oxides (Rb₂O, Rb₂O₂ and RbO₂), rubidium-silicates (Rb₂Si₄O₉ and Rb₂SiO₃) and rubidium-borates (RbBO₂).Another important factor affecting rubidium lamp performance is luminescent mode, which is mainly cotrolled by temperatue and RF voltage. Change of the luminescent mode from a ring mode to a red mode arises as the temperature or RF voltage becomes too large, leading to a decrease in the signal-to-noise ratio of optical intensity and failure of the rubidium spectral lamp. The maximal RF voltage corresponding to the mode change decreases with increasing temperature, and the parameter range of temperature and RF voltage corresponding to the ring mode is identified.The rubidium lamp should work at the temperatures and RF voltages as low as possible under the ring mode in order to weaken the interaction of rubidium and glass and to guarantee the discharge stability. It could reduce the rate of performance degradation for rubidium lamps. It is important and significant for engineering application and theoretical research to reveal damage effects and mechanisms for the glass envelope material exposed by radaition environment, as well as the mechanism of the interaction between rubidium and glass envelope.