Ion wind

from Wikipedia, the free encyclopedia
The articles ion wind and electric wind overlap thematically. Help me to better differentiate or merge the articles (→  instructions ) . To do this, take part in the relevant redundancy discussion . Please remove this module only after the redundancy has been completely processed and do not forget to include the relevant entry on the redundancy discussion page{{ Done | 1 = ~~~~}}to mark. burts ∞ 7:44 p.m. , Nov. 10, 2016 (CET)

Under ion wind is meant a directional flow of ions , a kind of the ion beam . It is generated by a gas discharge , from a positive to high voltage lying electrode (usually pointed shape, resulting in a very strong inhomogeneity of the electrical field brings with it) emanates. The ionization takes place by withdrawing electrons. The positively charged ions generated in this way are then accelerated away from this electrode (anode) along the field gradient . The ions in turn pick up electrons at an opposing, negatively charged electrode ( cathode ) of any shape.

Since the ions are positively charged, the direction of movement of the ions is the conventional current direction "from plus to minus". The direction of the electron flow z. B. in a lead wire would be reversed.

Glow discharge at atmospheric pressure. Positive electrode on the right.

Historical

Gas discharges at low pressure were observed experimentally in 1897 by Joseph John Thomson in a so-called cathode ray tube . The radiation that was later recognized as positive ions and caused a glimmering phenomenon was referred to as " channel rays ".

In addition, a cathode glow discharge was observed, a luminous phenomenon caused by the secondary electrons released from the cathode by gas ions of high kinetic energy. The electrons are accelerated towards the anode and called cathode rays .

Technical applications

Ion wind at atmospheric pressure in ordinary air, i.e. oxygen and nitrogen, creates a blue-violet glow discharge with ultraviolet (UV) components. The ionization and also the UV radiation generate oxygen radicals that attach to molecular oxygen, creating the aggressive gas ozone . This effect is used in devices, often called ozonizers, that use ozone to purify the air (primarily to neutralize odors) or to disinfect water.

The ion wind can also generate normal wind in the sense of an air flow. Fans can be constructed that do not have any moving parts and can therefore work almost noiselessly. Flow velocities are achieved which, at 2.5 m / s, are higher than the velocity achieved with mechanical fans.

In space technology, ion thrusters with noble gases are used as control thrusters.

literature

  • Wolfgang Demtröder: Experimental Physics. Volume 2: Electricity and Optics. 4th, revised. and exp. Edition. Springer Spectrum, Berlin / Heidelberg 2006, ISBN 3-540-33794-6 .
  • Michael Binnewies, Manfred Jäckel, Helge Willner , Geoff Rayner-Canham: General and Inorganic Chemistry. 1st edition. Spectrum, Akad. Verlag, Heidelberg / Berlin 2004, ISBN 3-8274-0208-5 .

Web links