129 / 2023-04-14 15:43:02

The study of transmission energy on Hundreds-of-joules Broadband Kunwu Laser Facility

Laser plasma interaction, Broadband laser

惯性约束聚变物理学 > 驱动器、制靶和诊断-II

Laser plasma interaction (LPI) is one of the key issues in laser-driven inertial confinement fusion ignition (ICF), as it may affect target compression and fusion energy gain ^[1]. Broadband laser technology is one novel option that may inhibit the related processes of LPI. It can be thought of a decrease of the effective light intensity felt in the plasma, which in turn may play a role in inhibiting the occurrence and development of related LPI processes in the plasma.

One broadband double-frequency laser with an output energy of hundreds of joules by using the superluminescent diode (SLD) technology has now been built by the researchers from Shanghai Institute of Laser Plasma ^[2]. In this research, the results from preliminary experiments using both broadband laser pulses and narrowband laser pulses have been carried on this facility. The experiment was carried out by using a single beam laser to drive a C₈H₈ plane target with different thickness from 2 μm to 300 μm. Then we tested the laser transmission energy with target of different thickness driven by broadband laser or narrowband laser. The results show that the laser transmission energy decreases with the increase of target thickness. Above all, we've found that it has significantly higher transmission energy for the same target driven by broadband laser than narrowband laser. The plasma generated and coupled by laser incident on target can be such important. As it directly determines the efficiency and quality of the energy conversion. The beam energy would be absorbed. In the direct-drive approach, electrons in the target’s outer would transport that energy to the denser shell material to drive the ablation and the resulting implosion. In the indirect-drive approach, the laser energy is converted to X-rays. Higher transmission energy may indicate less energy loss during the laser interact with the plasma corona of the imploding capsule. Thus, this interesting and valuable experimental phenomenon may have influence on the fundamental understanding of the related processes of laser plasma interaction of novel broadband low- coherence laser facility.