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The Penning source is a low gas pressure, cold cathode ion source which utilizes crossed electric and magnetic fields. The ion source anode is at a positive potential, either dc or pulsed, with respect to the source cathode. The ion source voltage is normally between 2 and 7 kilovolts.
A set of cold cathode discharge tubes. A cold cathode [1] is a cathode that is not electrically heated by a filament. [note 1] A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone. It is used in gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube.
A duoplasmatron is a type of glow discharge ion source that consists of a hot cathode or cold cathode that produces a plasma that is used to ionize a gas. [1] [22] THey can produce positive or negative ions. [23] They are used for secondary ion mass spectrometry, ion beam etching, and high-energy physics. [24] [25] [26]
Penning ionization is a form of chemi-ionization, an ionization process involving reactions between neutral atoms or molecules. [1] [2] The Penning effect is put to practical use in applications such as gas-discharge neon lamps and fluorescent lamps, where the lamp is filled with a Penning mixture to improve the electrical characteristics of the lamps.
The physical principles of ion traps were first explored by F. M. Penning (1894–1953), who observed that electrons released by the cathode of an ionization vacuum gauge follow a long cycloidal path to the anode in the presence of a sufficiently strong magnetic field. [6]
A cylindrical version of a Penning trap, with open endcaps to permit axial access. B indicates the magnetic field, and E indicates the electric field used for storage of the particles in the trap centre. A Penning trap is a device for the storage of charged particles using a homogeneous magnetic field and a quadrupole electric field.
The basic element of the common ion pump is a Penning trap. [6] A swirling cloud of electrons produced by an electric discharge is temporarily stored in the anode region of a Penning trap. These electrons ionize incoming gas atoms and molecules. The resultant swirling ions are accelerated to strike a chemically active cathode (usually titanium ...
I 0 is the photoelectric current generated at the cathode surface, e is Euler's number, α n is the first Townsend ionisation coefficient, expressing the number of ion pairs generated per unit length (e.g. meter) by a negative ion moving from cathode to anode, and; d is the distance between the plates of the device.