| Abstract: | Heliotron E(H-E) experiment was started in 1980. Until 1987 high power heating experiments for improving plasma parameters have almost finished. H-E firstly demonstrated that ECR heated plasmas are usable for target plasmas of NBI or ICRF heating to obtain high density and high temperature currentless plasmas. The highest electron temperature is 1.5keV and ion temperature is 1.6keV and both are realized in the low density regime of <n> (average density) ≤1013cm?3. H-E also showed that the currentless plasmas have no major disruption and quasi-steady plasmas are confined with controlling impurity ions by titanium gettering and carbon coating. H-E also obtained <β> (average β) –2%, which is the highest value realized in helical systems, with <n–8×l013cm?3 and Te(0)–Ti(0)–350 eV at B0 (magnetic field at the magnetic axis) =0.94 T. In the high β experiments pressure-driven instabilities were observed for peaked pressure profiles and sometimes relaxation oscillations similar to the tokamak internal disruptions were observed. In the ECRH plasmas neoclassical transport is dominant in the region inside the half radius. However, global confinement time τE follows the scaling law τE ∝<n>0.66Pheat ?0.53 which is different from the neoclassical scaling law. Here Pheat denotes the net heating power. Based on the H-E results, a new large helical system design study has started in 1986. The plasma parameters entering the regime of <n>τE<T> (2–3)× 1019m?3?S?keV is investigated, which is about one tenth of fusion plasma condition. From the transport code studies and empirical scaling law based on the H-E results, R=(4×5)m, ā=(50–60)cm and Bo=4T are required to satisfy the above condition with Pheat=20MW. The design study to fix the magnetic field configuration is progressing. Expected one is l=2 and m=10 with additional poloidal coils, where m is a toroidal period number. The magnetic field is produced by superconducting coil and long pulse operation will be tested, if continuous heating is available. |
