29th Symposium on Fusion Technology (SOFT 2016)

P1.020 Fabrication of DLC cone for fast ignition experiment

5 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 20

Poster A. Experimental Fusion Devices and Supporting Facilities P1 Poster session

Speaker

Mayuko Koga (Graduate School of Engineering)

Description

Fast ignition is one of the proposed ways to achieve high fusion energy gain in inertial fusion research. This scheme has an advantage that requirements of laser power and implosion process for ignition are not strict compared to that in central ignition. For a successful ignition, it is necessary to transport the energy of hot electrons to the imploded core effectively. Recently, it is found that hot electrons were diverged more than expected. In addition, it is concerned that hot electrons are scattered by high-Z plasma generated from gold cone target. This may cause the drop of the energy coupling of the heating laser to hot electrons. Therefore, low-Z materials, such as diamond like carbon (DLC) and aluminum, are drawing attention as cone materials. However, it is very difficult to deposit thick DLC layer for making a stand-alone DLC cone because of its strong residual stress. In this study, we tried various preparation conditions for thick DLC layers and studied its characteristics. DLC layer was prepared on metal conical bars by using plasma–based ion implantation and deposition system. Acetylene gas or toluene vapor was used as a source. It was found that the toluene vapor had an advantage in thick layer deposition because of its high deposition rate. It was found that rf pulse power, negative bias pulse and gas pressure affected deposition rates. These DLC layers showed SP³3 rich property in Near edge X-ray absorption fine structures (NEXAFS) spectra. Moreover, we improved the DLC cone fabrication process (cutting and etching). Based on these results, we succeeded in making stand alone DLC cones more easily.