Anomalous Ion Heating Effect of Magnetic Reconnection in TS-3/4 Merging Experiment
Abstract
Significant ion heating was observed during merging of two tokamaks, spheromaks, and RFPs in TS-3 device. This phenomena was found useful for an initial high-power heating of compact torus plasmas. Merging of two torus plasmas with q<1.5 increases center ion temperature rapidly from 10eV to over 100eV during magnetic reconnection, increasing poloidal beta βp by 10 ~20%. The heating power increases with decreasing magnetic field component BX parallel to the ``X-point'' line and with increasing the external force F that pushes the two initial plasma. This dependence of ion heating on BX and F is quite similar to that of magnetic reconnection speed or anomalous resistivity, indicating the ion heating is caused by magnetic reconnection. This BX and F dependence can be explained by the anomalous resistivity of current sheet that appears when its sheet width is compressed shorter than ion gyroradius. Mach probe measurement indicates that the ion outflow velocity from X-point is almost as high as ion thermal velocity after the reconnection heating, which reaches about 70% of the Alfven speed of the upstream region( ~ 100 km/sec). The outflow ion velocity from X-point was also found to decrease with increasing B_X, in agreement with the dependence of the ion heating on B_X. The ion heating is probably caused by the themalization of accelerated ions though some velocity dumping mechanisms such as shocks or large ion viscosity.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1998
- Bibcode:
- 1998APS..DPP.K6S50I