Recent Progress of TS-3/4 Reconnection Heating Experiments

Y. Ono and E. Kawamori

The clear evidence of reconnection outflow heating has been measured
in the TS-3/4 laboratory experiments,
using the 2-D Doppler broadening measurement.
This fact leads us to the first application of reconnection
to pulsed high-power startup/ heating of fusion plasmas.
Two spherical tokamaks (STs) produced by PF coil induction were
merged together for its quick beta-ramp-up from 0.05 to 0.4-0.6.
The reconnection outflow speed was equal to the Alfven speed
under no guiding field condition, causing ion heating power
as high as 5-30MW in TS-3 with B=0.5kG.
The outflow energy is converted mostly into ion thermal energy
through ion viscosity and/or fast shock,
indicating that the ion temperature increment
(and the thermal energy increment) scales
with squares of reconnecting magnetic field (Alfven speed).
This unique method has the highest heating power MW-GW
among all CS(Center Solenoid)-less startup methods of STs
and the heating time much shorter than the energy confinement time.
These facts suggest that two merging STs with B=1-3T will be
transformed into an ITER-like burning ST with T?20keV
possibly through partly relativistic reconnection process.