Whistler Wave generation by an electron beam in a LAPTAG Plasma Physics experiment

A multi-grid pulsed electron beam (E$_{beam}=$ 1-4.8 KV, area $=$1.32 cm$^{2}$, $\tau $ \textgreater 5 $\mu $s ) is inserted into a background plasma (He, n $=$ 5X10$^{10}$ cm$^{3}$, B$_{0z} \quad =$ 80 G, L $=$ 1.5 m, dia $=$ 40 cm). The pulsed electron beam power supply, can generate up to 4800 Volts at 10 Amps and was constructed by the LAPTAG high school students. The beam can be oriented at any angle with respect to the background magnetic field. The pulsed beam generates whistler waves by Cherenkov radiation. The waves are detected with 3 axis magnetic pickup probes which can be moved in planes transverse or parallel to the background magnetic field under computer control. The whistler wave pattern is used to determine the wavenumber ${\rm {\bf \vec{{k}}}}$ and Fourier analysis of the signal determines $\omega $. The wave dispersion relation is compared to theory.