Electron Structures

Mechanical structures of conductors with their surrounding dielectrics have a profound influence on electromagnetic signal and power propagation. This post explores some of these mechanical conductor structures and the influence on electron flow.

Microstrip capacitors occur when, relative to the wavelength of the propagating wave, the microstrip widens considerably. Often microwaves are manipulated using microstrip capacitors. Electrons will be trapped momentarily causing the capacitive effect. Electrons will slow down their drift velocity in the wider capacitive microstrip though the group velocity of the electromagnetic wave may not slow down at all.

Microstrip inductor is created to, relative to the wavelength of the propagating wave, the microstrip narrows considerably. Microwaves can be manipulated with microstrip inductors. Electrons will accelerate and move faster through the narrow space. Some of the electrons will jump off the conductor and eddy out. This phenomenon is known as inductance and is used as a linear circuit element in microwave circuits.

Brushes are an old electron structure. They have been used to build high voltages. Excited electrons will find themselves traveling down a conducting brush towards the end. Electrons have been observed to fire very well off the end of conductive brushes no doubt creating some amount of inductance along the way (Ampere-Maxwell's law). Plasma discharge is observed from the ends of brushes as large amounts of electrons fire off the ends of the bristles.

Spike or electron wick is used for electrostatic purposes. When a surface builds up too many excess electrons such as on the wing of an airplane or on the international space station it has to find a way to shed the excess charge. If the charge is not neutralized to the surroundings communication noise or arcing could be a dangerous result. Spikes or wicks can be a tuned electron structure that allows for some inductance or eddy electrons that keep the flow of electrons from the aircraft or the spacecraft. The spikes will act as an electron trap as the conductivity and inductance will propel electrons from the craft but it is far less likely that an electron will spontaneously jump back onto the spike.

Xe charge balance mechanism allows the fuselage of the international space station to reach charge balance with the surrounding orbital plasma if the station finds itself short on electron or positively charged. The station might accelerate Xe nuclei into the surrounding plasma. The electrons that were orbiting the Xe nuclei before they were accelerated will diffuse through the chassis of the station causing a relative match in charge balance with the surrounding plasma.

Resonant cavities are a topic I should attack some other time. These structures are used on microwave frequency radiation to provide bandpass linear effects. Someone has even proposed harvesting thrust from an electromagnetic resonant cavity. More on this some other time.