Doppler spectroscopy and D-alpha emission diagnostics for the C-2 FRC plasma

Two Doppler spectroscopy diagnostics with complementary capabilities are developed to measure the ion temperatures and velocities of FRC plasmas in the C-2 device. First, the multichord ion doppler diagnostic can simultaneously measure 15 chords of the plasma using an image intensified camera. Second, a single-chord fast-response ion Doppler diagnostic provides much higher faster time response by using a 16-channel photo-multiplier tube array. To study the neutral density of deuterium under different wall and plasma conditions, a highly sensitive eight-channel D-alpha diagnostic has been developed and calibrated for absolute radiance measurements. These spectroscopic diagnostics capabilities, combined with other plasma diagnostics, are helping to understand and improve the field reversed configuration plasmas in the C-2 device. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489971

Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-beta Compact Toroids

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-beta plasmoids preformed by the dynamic version of field-reversed theta-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T(i) + T(e)) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection

Formation of a long-lived hot field reversed configuration by dynamically merging two colliding high-beta compact toroids

A high temperature field reversed configuration (FRC) has been produced in the newly built, world's largest compact toroid (CT) facility, C-2, by colliding and merging two high-beta CTs produced using the advanced field-reversed theta-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional theta-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (T(e)+T(i)) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-beta plasmas. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3574380

Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-β Compact Toroids

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-beta plasmoids preformed by the dynamic version of field-reversed theta-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T(i) + T(e)) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection