What is the difference between a field emission and thermionic source tems?
The field emission source produces a greater current density than that produced by the thermionic sources and produces ~10 to 100 times higher electron brightness than that of the thermionic single crystal LaB6 emission filament as listed in a table on the comparison of various electron sources in page1409.
What is the difference between thermionic emission and photoelectric emission?
What is the difference between thermionic emission and photoelectric emission? During thermionic emission electrons are emitted from metal surface by providing heat energy, whereas, during photoelectric emission light energy is emitted when, electrons are emitted from the surface of metal.
What is the difference between a field emission Schottky field emission and thermionic source electron emitters?
Emitters are either of cold-cathode type, usually made of single crystal tungsten sharpened to a tip radius of about 100 nm, or of the Schottky type, in which thermionic emission is enhanced by barrier lowering in the presence of a high electric field.
What is thermal field emission?
The thermal (thermally assisted) field-emission electron gun (TFEG) emits electrons from a tungsten (W) tip emitter by tunneling the potential barrier (～4.5 eV) where the emitter is heated at ～1600 K in a strong electric field. The energy spread of the emitted electrons from the TFEG is ～0.7 eV.
What is the thermionic electron source?
Thermionic emission of electron Thermionic sources rely on heat to generate electrons, similar to how light is produced by incandescent lightbulbs. Just like a tungsten filament, these crystals are heated by an applied current until there is enough energy to emit electrons.
What is difference between photoelectric emission and photoelectric effect?
The phenomenon of emission of electrons is known as the photoelectric emission. The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner can be called photo electrons.
What is the difference between photoionization and photoelectric emission?
Photovoltaic effect is the generation of an electric current in a substance when exposed to light. The main difference between Photoelectric Effect and Photovoltaic Effect is that in Photoelectric Effect the electrons are emitted to open space whereas in Photovoltaic Effect the electrons enter a different material.
What is thermionic emission and field emission?
The former, called thermionic emission when electrons are excited by heat , typically requires cathode temperatures ~103 K. The latter, called field emission, occurs when a high voltage thins the potential barrier , and typically requires the cathode electric field to be greater than ~108 V/m.
What is field emission in physics?
field emission, also called Cold Emission, discharge of electrons from the surface of a material subjected to a strong electric field. The resulting current of electrons through the surface of a material under the influence of a strong electric field is called field emission.
What is thermionic field emission?
thermionic emission, discharge of electrons from heated materials, widely used as a source of electrons in conventional electron tubes (e.g., television picture tubes) in the fields of electronics and communications.
What is thermionic emission of electron?
Thermionic emission is the emission of electrons from a heated metal (cathode). As the temperature increases, the surface electrons gain energy. The energy acquired by the surface electrons allows them to move a short distance off the surface thus resulting in emission.