plasma and gaseous electronics
TRANSCRIPT
Plasma and Gaseous Electronics
Group 11Graubner, Erik; Walker, Andrew; Walters, Robert; Williams, Wesley
What is Plasma?
• Plasma is a fundamental state of matter• Plasmas account for over 99% of the visible universe.
What is Plasma?
• Plasma is composed of Ionized Atoms and free electrons.– After enough heat or other energies is applied to affect the electrical properties of the gas, it becomes a plasma.
What is Plasma?
• The interactions between the charged and neutral particles determine the properties and usefulness of the plasma
• The type of atoms and the ratio of charged and neutral particles result in a broad spectrum of plasma types, characteristics, and behaviors
What is Plasma?
• Plasma was first identified in 1879• Called Radiant Matter by Sir William Crookes• The term "plasma" was coined by Irving Langmuir in 1928.
• Based on Greek origin meaning “to mold” because it molds to the shape of its container
Physics of Plasma
Generation of Artificial Plasma
• Cathode ray tubes • Must have an energy
source to generate and sustain
• Current is applied across a dielectric gas
• The potential difference and electric field pull electrons to the Anode and positive charges to the Cathode
Breakdown
• As the voltage increases the current stresses the material beyond its dielectric limit and causes electrical breakdown
• Breakdown is seen in region 3
• Dielectric Breakdown of air = 3 X 10^6 V/m
Townsend Avalanche
• This breakdown process is know as the Townsend Avalanche
• Collisions between electrons and atoms create more ions and electrons
Break Down/Avalanche
Ion creation
• Collisions between electrons and atoms create more ions and electrons
• The number of ions increase into the millions after about 20 sets of collisions
• The collisions also cause Photons to be released
Arcing
• With high current density and ionization an electric arc occurs
• Similar to lightning
Plasma
• Resistance along the arc creates heat, this heat ionizes more atoms
• The gas gradually turns into a thermal plasma
• The plasma is said to be in thermal equilibrium at which the temperature is homogenous throughout
Applications of Plasma
Plasma Torch
• Plasma Spraying• Plasma Gasification• Plasma Cutting
Precision Cleaning
• Monatomic oxygen (inside oxygen plasma) at pressures above 0.1 torr is the most reactive element in the plasma and will readily combine with any organic hydrocarbon.
• The resultant combination is water vapor, which is carried away in the vacuum stream.
Plasma Television
Fluorescent Lights
• Argon is typically used• Mercury Vapor is added• Two metal plates on either side: cathode and anode (both act as cathodes, though).
• Townsend Avalanche + fluorescent coating = light!
Hall Thruster
• Used in Soviet Spacecraft• Uses Hall current, electron plasma, and ions.
Plasma Research
Research and Prototypes
• Research into plasma is extensive and promises to have considerable technological ramifications.
• These applications of plasma are still in their infancy and as such are either purely theoretical or exist in the form of early prototypes.
Variable Specific Impulse Magnetoplasma Rocket
• Uses radio waves to ionize and heat the rocket propellant to generate plasma. This plasma is accelerated by a strong magnetic field to generate thrust.
• This engine allows for switching between high thrust/low specific impulse and low thrust/high specific impulse configurations. This kind of freedom is not available on a normal rocket unless it has multiple engines.
Variable Specific Impulse Magnetoplasma Rocket
Plasma Antenna
Plasma Antenna
• The antenna consists of a hollow dielectric tube filled with a noble gas. As voltage is applied across the tube, the gas inside is ionized which generates plasma.
• The strength of the plasma antenna is its dynamism.
• Metal antennae are by nature static which limits them to certain frequencies in addition to an inability to easily vary operating parameters.
Plasma Antenna
• Plasma antennae can be dynamically configured and tuned to adjust various operating parameters such as frequency, direction, gain, bandwidth, and beamwidth. This versatility allows a single plasma antenna to replace multiple metal antennae.
• A plasma antenna can be turned off making it invisible to radar. Metal antennae cannot be as stealthy because they scatter incoming radar waves.
Plasma Antenna• Plasma antennae can simultaneously transmit and receive high‐frequency and low‐frequency signals without any interference.
• Plasma antennae are also incredibly resistant to various forms of electronic warfare.– They can be configured to be either invisible to, or immune to, high‐frequency, high‐power pulses.
– They are also resistant to signal jamming because of their dynamism.
Plasma Window
• A plasma window is a volume of space filled with plasma that is held in place via magnetic field.
• The viscosity of a plasma window allows it to separate gas at standard temperature and pressure from a total vacuum. Data suggests that a plasma window can separate gas at a pressure of nine atmospheres from a total vacuum.
Plasma Window
• A plasma window does not inhibit radiation in the form of electron beams or lasers from passing through.– Plasma windows allow radiation that can only be generated in a vacuum to be applied to objects in an atmosphere.
– Plasma windows make electron beam welding useful as the electron beams used dissipate when not in a vacuum.
The End….. Or is It?
• Questions?