Session GP1 - Poster Session IV.
POSTER session, Tuesday afternoon, October 30
Exhibit Hall B,
In the Cornell ion ring experiment FIREX, a proton ring is formed in one ion cyclotron period by cusp injection into a solenoid. The rapid magnetic field change generated by the ring current launches large-amplitude Alfvén waves with amplitudes as large as 25% of the 6~kG field. The lowest frequency and largest amplitude components of the wave spectrum are identified as the lowest-order (nearly radial) magnetoacoustic mode of the magnetized plasma column in the solenoid. In high-density plasmas this is the only significant mode, but injection into lower density plasmas in which the Alfven speed approaches the ring ion velocity also produces non-axisymmetric, higher frequency components, near the ion cyclotron frequency. Due to the wave generation, axial momentum is transferred from the ring to the plasma, bringing the ring to stop inside the solenoid. Diamagnetic loop arrays and magnetically-insulated proton detectors diagnose the wave and ring dynamics, and spectroscopic diagnostics measure energy deposition in the background plasma. We present our developing understanding of the ring-plasma dynamics, including ring stability and particle loss, and details of the magnetic dynamics.