Page 6 - EX_P3-37_a2

6 EX/P3-37
FIG. 6. Time evolutions of plasma radius and line-integrated electron density for (a) shot #44446 with injection at 2.0 ms (single CT) and for (b) shot #48492 with three CTs injected at 0.5 (single) and 3.0 ms (double).
The effect of injected CTs especially onto the FRC confinement has been confirmed by the time evolution of the Dα emission in the vicinity of injection plane. In the case without CT injection, there is no significant amount of emission from the FRC after collisional merging FRC formation as shown in FIG. 7. On the other hand, CT injection increases Dα emission. It is potentially caused by the particle loss from FRC core and/or neutral trailing gas flowing from the CT injector.
To reduce the adverse effect of CT injection into the target C-2U FRC, PI technique has been employed. Intensity of Dα emission is significantly lower compared to the case without PI as shown by the green trace in FIG. 7. This suggests that the trailing neutral gas is successfully reduced by the PI on the MCPG.
2.0
1.5 1.0 0.5
FRC (#48500), FRC+CT (#48468), FRC+CT+PI(#49755)
NC plane FRC FRC+CT
FRC+CT+PI
FRC+CT
FRC+CT+PI
Intensity (a.u.)
0 0 1.0
FIG. 7. Time evolution of the Dα emission on the plane by the CT injector. Black line is FRC without
CT injection, red is the case with CT injection and green one shows the case with PI.
4. Summary
In this project, a CT injector, which fuels 0.5 – 1.0 × 1019 of particles with 1kHz of repetition frequency have been developed. The injection velocity evaluated on the test stand keeps the range of 100km/s in a transverse magnetic field even after passing through the 1m long drift tube. This is high enough to penetrate external magnetic field of C-2U FRC. CTs injected perpendicularly to the geometrical axis of the C-2U demonstrated successful fueling with significant density build-up of 20 - 30% of total particle inventory per single CT injection
2.0 3.0 4.0 5.0
time (ms)