Engeering Design And Pressure Distribute Analysis For The Cryopumping System Of Neutral Beam Injection System

Neutral Beam Injection (NBI) heating technology is considered as one of the most effective method for fusion plasma heating by the international fusion community, for which can significantly upgrade the plasma parameters inside fusion device. Some large-scale fusion device, such as PLT,TFTR,JET,NSTX, have successfully applied NBI heating technology. The international fusion engineering test reactor (ITER) also has been planed to use this technique. Both the cryopumping performance of NBI cryopumping system and the characteristic of pressure distribution inside NBI system are two key factors that affect the steady experiment operation of NBI system. The aim of this thesis is to analyze the characteristic of pressure distribution inside the NBI system of HT-7 and to design its cryopumping system after taking into account of the technical requirement of steady experiment operation of the NBI for its vacuum pumping system.Based on the operating principle and structural trait of NBI system, gas source characteristic of its each parts were analyzed , one set of vacuum system was designed, the vacuum system was made up of a main differential cryopumping system consists of two cryocondensation pumps,and an auxiliary pumping system consists of turbomolecular pumps and mechanical pumps. Three-dimensional model of main vacuum chamber was established, and mechanical analysis was made using ANSYS software,and the results proved that the main vacuum chamber could meet the practical requirements of the intensity condition. The performance parameters of the cryopumping system such as pumping speed (for H₂), ultra vacuum, gas throughput, cryopanel temperature, cool-down time and residual gas species were measured to get their technical date through the test run experiment of the NBI system. The pressure distributions inside ion source, main vacuum chamber and drift tube were analyzed through utilizing origin and matlab software. The results reveal that the designed cryopumping system is of excellent performance, such as cool-down and warm-up process is uniform and steady, short cool-down time, high ultra vacuum and stable dynamic vacuum. The results may indicate that the designed system can meet the requirements of steady experiment operation of HT-7 NBI for vacuum quality.