Compression and Light Transmission Characteristics of Vacuum Tube under Magnetic Flux Compression Generator Driven Quasi-Isentropic Loading

Cylindrical quasi-isentropic compression driven by explosive magnetic flux compression generator (MFCG) enables ultra-high pressure loading of low-density materials. To obtain the optical properties of the compressed sample, a new vacuum light-guide probe structure using metal vacuum tube as the optical transmission channel is proposed to avoid the influence of loading pressure on the optical measurement path. In order to evaluate whether the optical diagnostic channel of the vacuum light-guide probe is closed in the MFCG quasi-isentropic loading experiment, the compression characteristics and light transmission characteristics of the cavity of the high-density metal vacuum tube under cylindrical implosion quasi-isentropic loading were analyzed and experimentally tested. In the experiment of compressing water conducted on the single-stage MFCG device CJS-100, through the comparative analysis of the measurement results of the inner shell velocity of the Ta tube and the theoretical calculation results, the inner diameter of the Ta tube with an outer diameter of 3 mm and an inner diameter of 2 mm is compressed to 1.28 mm when the water is quasi-isentropic loaded to about 485 GPa. During this time, the optical signal transmission channels of the Ta tube cavity and the optical fiber and fiber probe inside the Ta tube remain open. The optical signal remains present for about 50 ns after the inner diameter of the Ta tube is compressed to 1.28 mm. The results show that the measurement of optical characteristics of cylindrical implosion loading samples is feasible by using vacuum light-guide tube made of high-density metal materials such as Ta, which provides a new technical way for the measurement of optical properties of high-pressure samples in MFCG driven quasi-isentropic loading experiments.