The Construction Of Dual-HCN Laser And The Design Of CO₂ Dispersion Interferometer

Laser interferometers have become one of the most essential diagnostics for electron density which is critical for magnetic confinement plasma.Time resolution and phase resolution are two of the most important parameters of interferometer.In order to improving the time resolution and phase resolution,an useful method is to increase the heterodyne modulation frequency and vibration compensation of the system on each device.The main work of this paper also focuses on these two aspects:the design and construction of the dual-HCN laser on J-TEXT and the design of the CO₂ dispersion interferometer on HFRC（HUST Field-Reversed Configuration）.In the first part of the thesis,the research purpose and principle of the dual-HCN laser are introduced at first.The time resolution of HCN interferometer J-TEXT is 100us,which limits the ability to observe fast physical processes such as microscopic turbulence.By the construction of dual-HCN laser,the IF（Intermediate Frequency）signal frequency will be increased to 2MHz.Next,the main components of the dual-HCN laser are introduced.Then,the specific work including the calculation of the parameters of the discharge tube,the design of the cavity adjustment structure,and the design of the two-color HCN laser gas path system is described in detail.In the last of this part,a HCN laser is constructed and the experiment is carried out after the optical path is built.The output power of the laser is15mW and the optical characteristics are good too.The second part of the thesis focuses on the design of the CO₂ dispersion interferometer on HFRC.This part first introduces the background of HFRC devices and the design requirements for interferometer.Next,the conceptual design of CO₂ dispersion interferometer is completed.On the one hand,an acousto-optic modulator with a modulation frequency of 40 MHz is used for higher time resolution.On the other hand,the vibration noise is compensate by the second harmonic in the CO₂ dispersion interferometer.According to Gaussian optics theory,the optical lens parameter is designed.The optical waist of the system and the thickness of ZnSe window are calculated.Vacuum sealing arrangement of the window is also designed.Finally,the selection of the equipment is determined.