Study On The Technology Of Anti-deliquescence For CsI(Tl) Film And The Design For The Structure Of Light Conversion Components

The X-ray detector based on scintillators has many important applications in medical detection and security.CsI: Tl has become a very prevailing scintillator because of its outstanding optical properties,low cost and accessibility to grow.However,it is apt to deliquescence and its light conversion ability will deteriorate when exposed to the humid air.Therefore,it is crucial to do some research about the resistance of deliquescence for Cs I: Tl thin film.Moreover,in order to gather the diffusing visible light converted by Cs I: Tl and avoid the direct radiation damage to CCD,the light conversion component for X-ray detector should be designed.Thus,in this work,the research on the resistance of deliquescence for Cs I: Tl thin film has been done theoretically and experimentally,meanwhile the light conversion component for X-ray detector was designed and optimized.Firstly,the FTIR spectrum for CsI: Tl thin film was measured and the result testified the phenomenon of deliquescence when exposed to the humid air.Then the mechanism of deliquescence for Cs I: Tl thin film was analyzed theoretically.Furthermore,the effect of the air with different humidity and different exposure time to humid air on the crystal structure and fluorescent spectrum of CsI: Tl thin film was discussed.And it turned out that the ability of light conversion for CsI: Tl thin film decreased severely when it was exposed to the air with higher humidity and more time.Secondly,various schemes of anti-deliquescence film for CsI: Tl thin film was designed.Ultimately,aluminum,silicon dioxide and silicon nitride films were chosen to be the anti-deliquescence films for CsI: Tl thin film.The transmitted spectra of these three protection films were simulated to ensure the high transmittance in the target wavelength and the exact thickness of them was calculated.Eventually,these three protection films were grown by magnetron sputtering method and PEVCD respectively and the effect of the resistance of moisture for CsI: Tl thin film was measured.The results revealed that the Al was the best protection film with anti-deliquescence performance among these three films.Additionally,the parameters of initial light conversion component were calculated by imaging formulas based on the requirement of X-ray detector.According to the parameters,the 3D optical path diagram for light conversion component was built and the imaging quality of the initial light conversion component was evaluated through the software ZEMAX.Finally,due to the drawbacks in the initial light conversion components,the optimizing function was built to optimize its imaging quality.Although the overall aberration,the optical path difference of wavefront and the astigmatism of the initial light conversion components was improved drastically after the optimization,the drawbacks of confusing disc and diffraction capability was still existing.Subsequently,the light conversion component with three lenses was designed inspired by the three-lens camera.The evaluation results of this design were promising and its imaging quality met the requirement of X-ray detector.Hence,this ultimate design would offer important reference to accomplish the design of the complete X-ray detector.