Highlights of LHD Experiments
High Plasma Stored Energy, High Beta Discharge
A milestone of 1MJ stored energy was achieved by injecting higher heating power and optimizing plasma confinement.
We succeeded to produce plasma by NBI heating alone with optimized gas puffing. Based on this fact, high beta experiments using only NBI were conducted at low magnetic fields. The highest value of plasma beta, 3%, was obtained at Bt=0.5T.
Attainment of 10keV Central Electron Temperature
The 5th campaign of LHD experiments to explore the high electron temperature regime with low electron density has been started using an upgraded electron cyclotron heating (ECH) system. As a result, high central electron temperatures well above 10keV were recorded.
|Electron temperature profiles measured by high power YAG-Thomson scattering at several times|
Steady-State Experiment, 150 seconds Discharge by ICRF
We are now attempting to sustain high performance plasmas for longer times.
Significant progress is two-minute discharges by Ion Cyclotron Range of Frequency heating (ICRF), in which electron density is 0.8x1019m-3 and electron, ion temperatures are both 1.2keV. High density plasmas are sustained by 2MW NBI power for 10seconds and plasma shots over forty seconds can be repeated every nine minutes. These results clearly demonstrate the inherent merit of helical devices and their prospects for future thermonuclear fusion reactors.
|CCD camera image of 150 seconds ICRF discharge|
Achievememt of Ti(0)=7keV
A central ion temperature of 7.1keV was achieved during the 6th experimental campaign in LHD. A newly operated Ne glow discharge cleaning was very effective for hydrogen removal from the vacuum wall. The increase in the NBI absorption power by Ar gas puff and the increase in the NBI heating power up to 10MW also contrbuted to the high ion temperature.