Knudsen Cell
Encyclopedia
In crystal growth, Knudsen Cells are often used as sources evaporators for relatively low partial pressure elementary sources (e.g. Ga, Al, Hg, As). It is easy to control the temperature of evaporating content and commonly used in molecular-beam epitaxy.

A typical Knudsen cell contains a crucible
Crucible
A crucible is a container used for metal, glass, and pigment production as well as a number of modern laboratory processes, which can withstand temperatures high enough to melt or otherwise alter its contents...

 (made of pyrolytic boron nitride
Boron nitride
Boron nitride is a chemical compound with chemical formula BN, consisting of equal numbers of boron and nitrogen atoms. BN is isoelectronic to a similarly structured carbon lattice and thus exists in various crystalline forms...

, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

, tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

 or graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

), heating filaments (often made of metal tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...

), water cooling system, heat shield
Heat shield
A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...

s and orifice
Orifice
An orifice is any opening, mouth, hole or vent, as of a pipe, plate, or a body.* Body orifice* Orifice plate* Calibrated orifice* Nozzle* Back Orifice-See also:* Choked flow* Needle valve* Venturi effect* Flow measurement...

 shutter
Shutter
Shutter may refer to:Windows:*Window shutter, a solid window covering used to block light and winds*Plantation Shutters/Jigsaw Shutters, interior wooden louvred shutters to control heat, light and privacy...

.
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