High-Voltage Insulator (from left: solution mesh after adaptive process, scalar potential with equipotential lines and vectors of displacement, electric field)
Trajectories of electrons in depressed collector
http://youtu.be/qjqj4JKQ0HE
Sparkgap example from video tutorial.
http://youtu.be/LGLQGzNXEpE
Oscilloscope example from video tutorial.