Excitation of waves by a spiraling ion beam in a large magnetoplasma

A helium ion source (25 kV, 5 A, 0.3 Hz rep rate, 0.5-1.5 ms pulse-width) has been constructed for performing the fusion-relevant fast-ion studies on the Large Plasma Device (LAPD). The ion source comprises a hot-cathode LaB$_6$ plasma source, a multi-aperture three-grid beam extractor, power supplies, and neutral pumping system. The beam is injected from the end of the device with variable injection angles and it spirals down the LAPD plasma (n$\sim$10$^{11}$ cm$^{-3}$, T$_e\sim$0.4 eV, B = 0.5 -- 1.8 kG) radiating a multitude of waves in the drift, shear Alfven, ion cyclotron, and lower hybrid frequency ranges. The beam profiles are measured at several axial locations (up to 12 m from the deaccel grid) using a fast-ion collector. Measurements have confirmed the production of a low-divergence ion beam that forms helical orbits during oblique injection. Initial results on the beam-driven low-frequency waves ($f < f_{lh}$), with a particular emphasis on Alfven waves, will be presented.