▶ Date: 2022. 11. 17(THU)

▶ Time: 4:30 ~ 5:30 PM

▶ Venue :  Online(ZOOM)

     Link: https://us02web.zoom.us/j/2076815786?pwd=UUNMbldJSjBlcXpEVUtHNzJPNmNZdz09

▶ Speaker: Prof., Rui Qiu(Tsinghua Univ., Beijing)

▶ Title: Bremsstrahlung Photon Dose Generated from Ultra-Intense and Ultra-Short Laser Target Interactions

▶ Abstract:

Radiation protection in ultra-intense and ultra-short laser facilities is becoming more and more important as both the number and the intensity of the laser facility increase rapidly with the development of laser technology. Experiments show that bremsstrahlung photon dose is usually dominant in this new type of ionizing radiation source. Therefore bremsstrahlung photon dose estimation is essential for radiation protection in ultra-intense and ultra-short laser facilities. This paper reviews the literatures on the bremsstrahlung photon dose level in the experiments and the photon dose estimation models. The effects of laser-target interaction experiment configuration on the photon dose are also analyzed. Experimental measurements are collected from a total of 18 ultra-intense and ultra-short laser facilities over the laser intensities from 10¹⁷ ~ 10²¹ W cm^-2 μm^-2. Measured normalized photon dose values spread over a span of 6 orders from 10^-5 ~ 1 mSv J^-1 shot^-1. The wide spread range of normalized photon dose suggests that there might be some factors not considered in the photon dose estimation models. In this review, four important electron physical quantities that are related to the photon dose are introduced, which are hot electron energy distribution, characteristic temperature of electron, laser-to-electron conversion efficiency, and electron divergence angle. Then four photon dose estimation models from different groups are introduced and discussed. The measurement results in the literatures are compared with the prediction values with these models. The diagram of normalized photon dose could be roughly divided into four regions by the dose estimation models. Specifically, each region corresponds to a unique target scheme, namely foil target, solid target, coated target and hybrid target. This review shows that the target scheme might be one of the most relavant factors that affect the bremsstrahlung photon dose level. For the radiation shielding of such ultra-intense and ultra-short laser facility, consideration of different target scheme may help ensure radiation safty and reduce the shielding cost.