Characterization Of Ionizing Radiation In The Ultra-short Ultra-intense Laser Facility

With the rapid development of ultra-short laser technology,the ultra-short ultra-high intensity laser facility is continuously emerging in the world,which can provide laser beams with intensity larger than 10~188 W/cm~2.The emergence of these devices has led to a wide range of cutting-edge disciplines and major breakthroughs.At the same time,it has been proved that the interaction between the high-intensity laser and a solid target produces various ionizing radiation and significant dose,thus resulting in a potential radiological hazard to the environment and people around the facility.Therefore,it is necessary to study the radiation protection for this kind of new radiation source in the high-intensity laser facility.To date,only limited studies have been conducted on this laser-induced radiological protection issue.The key problem that needs to be resolved is to characterize the radiological hazard for this kind of new radiation source,namely studying the particle type,radiation level,energy spectrum and other source characteristics.Therefore,the following research work has been carried out in this study:1.The primary radiation source terms in the high-intensity laser facility were summarized and analyzed.According to the recent research results in the laser-plasma field,the characteristics of laser-driven high-energy electron and proton source terms were analyzed,and the relationship between the key source parameters(such as yield,energy spectrum and angular distribution)and the parameters of laser and plasma is given.2.The characteristics of the X-ray source generated by the high-intensity laser interaction with a solid target were studied theoretically.Based on the analysis of the source terms of hot electron,this study proposed an equation and a theoretical model to calculate X-ray dose and energy spectra,respectively.The variations in X-ray dose and energy spectra with the parameters of laser and target were studied.Moreover,due to the exponential-like spectrum of hot electron,the attenuation curves of X-ray generated by hot electron were studied in the shielding material,and the difference of attenuation curves between the laser-driven X-ray source and other X-ray source was analyzed.3.The hot electron spectra,angular distribution of photon dose and X-ray spectra generated by high-intensity laser interaction with a solid target were measured on the XG-III laser facility in China.The measured results validate the theoretical model established in this paper.In addition,the performances of different dosimeters were tested in this kind of pulsed radiation fields.The measured results can be used to assess the radiation safety in the XG-III laser facility.4.The neutron yield and energy spectra were calculated for the laser-driven photoneutron source and TNSA proton-induced neutron source,respectively.A theoretical model was established to calculate the photoneutron yield generated by the high-intensity laser interaction with a solid target.The calculation results provide a reference for assessing the radiological hazard caused by neutron in the high-intensity laser facility.