346 / 2019-02-27 10:08:06

Precise determination of on-target M-band X-ray via preheating and shock propagation simulation

inertial confinent fusion,on target M-band X-rays,preheating effect

全体主题 > Laser and Particle Beam Fusion

In indirect drive inertial confinement fusion (ICF), high energy laser beams are converted into uniform X-ray radiation field via a high-Z enclosure (hohlraum). Ideally, intense soft X-rays can launch shock waves and drive the capsule to implosion. However, due to the emission of high energy X-rays originated from the hot, low density plasma, such as gold M-band, radiation field usually deviates from ideal blackbody radiation.
These hard X-ray preheating inside hohlraum would degrade capsule performance and induce deleterious effects on inertial confinement fusion, e.g. by generating additional entropy and decreasing capsule compressibility or by changing shock propagation and tuning campaign. Precise determination and study of M-band generation and effect is of critical importance for target design as well as capsule implosion.
Experimentally, previous research studied M-band generation by measuring hard X-ray emission from laser entrance hole (LEH). Due to different visual angles and the complexity of hohlraum energetic simulation, it is not straight forward to correlate M-band measurement from LEH to those 'on target'.
This talk will present a more direct evaluation on M-band X-rays deposited on target. Instead of measurement from LEH, the preheating effect brought by M-band X-rays before and during shock breakout has been studied. Since preheat level is highly sensitive to radiation flux spectra, it could provide useful information for assessing hard X-rays inside hohlraum.
Sensitivity test and correlation factor between simulation and experimental measurement shows shock transition time and shock temperature profile are good benchmarks to characterize target preheat level with high precision. This study is proposed as a preliminary step to develop prediction capability in ICF and high energy density physics.