PROGRESS SUMMARY OF LHD ENGINEERING DESIGN AND CONSTRUCTION

摘要

In March 1998, the large helical device (LHD) project finally completed its 8 years constructionrnschedule. LHD is a superconducting (SC) heliotron type device with R=3.9 m, a_p=0.6 m, and B=3 T,rnwhich has simplex and continuous large helical coils. The major mission of LHD is to demonstrate thernhigh potential of currentless helical-toroidal plasmas, which are free from current disruption and havernan intrinsic potential for steady state operation. After the intensive physics design studies in the 1980’s,rnthe necessary programs of SC engineering R&D were made and carried out, and as a result, LHDrnfabrication technologies were successfully developed. In this process, a significant database on fusionrnengineering has been established.rnThese achievements have been made in various areas, such as the technologies of SC conductorrndevelopment, SC coil fabrication, liquid helium (Lhe) and supercritical helium (She) cryogenics,rndevelopment of low temperature structural materials and welding, operation and control, and powerrnsupply systems and related SC coil protection schemes. They are integrated, and nowadays comprise arnmajor part of the LHD relevant fusion technology area. These issues correspond to a necessaryrntechnological data base for the next step of future reactor designs. In addition, we could increase thisrnwith successful commissioning tests just after the completion of LHD machine assembly phase, whichrnconsisted of vacuum leak test, Lhe cooldown test, and coil current excitation test. We recapitulate andrnhighlight these LHD relevant engineering developments in this paper.rnTo summarize our construction of LHD as an SC device, the critical design with NbTi SC materialrnhas been successfully accomplished by our R&D activities, which enables us to move into a newrnregime of fusion experiments.