Direct experimental investigation of the electron distribution function in a magnetized plasma

Time resolved measurements of the electron distribution function in a magnetized plasma, F(vparallel,vperpendicular), are presented. These measurements were obtained with a novel diagnostic of the author's own design. The diagnostic works by imposing two orthogonal criteria for electron collection: an adjustable magnetostatic barrier which selects electrons according to their pitch angle, Wperpendicular/Wparallel, and an electrostatic barrier which selects electrons on the basis of their parallel energy, Wparallel. The theory of operation of the analyzer is discussed and details of its construction are presented. The analyzer features a magnetic configuration with no net dipole moment to localize the magnetostatic component of the analyzer, a zero crossing coil to provide a magnetic field null at the location of the electrostatic collector, and a large inner diameter to minimize the effect of the analyzer wall on the plasma. The measurements were performed on a plasma produced by a lower-power rf source. The source consisted of a reentrant microwave cavity driven at the electron cyclotron frequency and it produced a plasma density of roughly 109 cm-3 per watt of rf power. The cavity's construction and performance is also described