Pinch-effekt (elektrodynamik)

En pinch-effekt, elektromagnetisk indsnøringseffekt, elektromagnetisk sammensnøringseffekt eller elektromagnetisk knibningsfænomen er kompressionen af en elektrisk ledende tråd af magnetiske kræfter. Lederen er typisk et plasma, men kunne også være et faststof eller flydende metal. I en z-pinch, er den elektriske strøm aksial (i z-retningen i et cylindrisk koordinatsystem) og magnetfeltet azimutalt; i en theta-pinch strømmen azimutal (i theta-retningen i cylindriske koordinater) og magnetfeltet er aksialt. Fænomenet benævnes også som et "Bennett-pinch"^[1] (efter Willard Harrison Bennett), "elektromagnetisk-pinch",^[2] "magnetisk-pinch",^[3] "pinch-effekt"^[4] eller "plasma-pinch".^[5]

Z-pinch illustrerer det elektromagnetiske knibningsfænomen af plasmatråde i en elektrisk udladning fra en tesla-transformator. (Klik på billedet for at forstørre)

Pinch-effekten forekommer naturligt i elektriske udladninger som f.eks. lyn,^[6] polarlyset,^[7] strømlag,^[8] and solfakler.^[9] Pinch-effekter produceres også i laboratorier, primært ved forskning i fusionskraft, men også af hobby-folk (f.eks. indsnøre aluminumsdåser).^[10]

Magneforming

Uddybende artikel: Magneforming

Indsnøringsvirkningen (pinch-effekten) kan være så stærk, at den svarer til f.eks. 100 atmosfære. Der er mange eksempler på at hobby-folk har "forminsket"/3D-mast mønter – og lagt to mønter oven på hinanden med resultatet, at de former to halvkugler eller en hel møntkugle grundet 3D-masning. Bemærk at bevidst deformering af mønter kan være ulovlig i nogle lande.^[11]^[12]

Kilder/referencer

^ Se for eksempel, Buneman, O., "The Bennett Pinch" (1961) Plasma Physics, Edited by James E. Drummond. LOC 60-12766. Publ. McGraw-Hill, Inc., New York, 1961, p.202
^ Lee, S., "Energy balance and the radius of electromagnetically pinched plasma columns" (1983) Plasma Physics, Volume 25, Issue 5, pp. 571–576 (1983).
^ Schmidt, Helmut, "Formation of a Magnetic Pinch in InSb and the Possibility of Population Inversion in the Pinch" (1966) Physical Review, vol. 149, Issue 2, pp. 564–573
^ Severnyi, A. B., "On the Appearance of Cosmics Rays in the Pinch Effect in Solar Flares" (1959) Soviet Astronomy, Vol. 3, p.887
^ Zueva, N. M.; Solov'ev, L. S.; Morozov, A. I. "Nonlinear instability of plasma pinches" (1976) Journal of Experimental and Theoretical Physics Letters, Vol. 23, p.256
^ Rai, J.; Singh, A. K.; Saha, S. K, "Magnetic field within the return stroke channel of lightning" (1973) Indian Journal of Radio and Space Physics, vol. 2, Dec. 1973, p. 240-242.
^ Galperin, Iu. I.; Zelenyi, L. M.; Kuznetsova, M. M. "Pinching of field-aligned currents as a possible mechanism for the formation of raylike auroral forms" (1986) Kosmicheskie Issledovaniia (ISSN 0023-4206), vol. 24, Nov.-Dec. 1986, p. 865-874. på russisk.
^ Syrovatskii, S. I. "Pinch sheets and reconnection in astrophysics" (1981) In Annual review of astronomy and astrophysics. Volume 19. (A82-11551 02-90) Palo Alto, CA, Annual Reviews, Inc., 1981, p. 163-229
^ Airapetyan, V. S.; Vikhrev, V. V.; Ivanov, V. V.; Rozanova, G. A. "Pinch Mechanism of Energy Release of Stellar Flares" (1990) Astrophsyics (Tr. Astrofizika) v.32 No.3 Nov. p.230 1990
^ For eksempel, se (webarchive-backup) "Electromagnetic Crusher"
^ Stoneridge Engineering – Theory of Operation of the Quarter Shrinker Citat: "...In an opinion letter, the US Mint "frowns on the despicable practice" of altering coins, but they agree that it is quite legal to shrink coins. Note that this may not be the case within other countries! For example, in the UK and Australia, defacing the Queen's image on a coin may be considered a punishable offense..."
^ Stoneridge Engineering: The Reconstructed History of Quarter Shrinking

Se også

Madison Symmetric Torus (Reverseret felt-pinch, hvordan en torus-pinch-effekt laves)
Explosively pumped flux compression generator

Eksterne henvisninger

Web-archive backup: Can crushing info using electromagnetism among other things.
The MAGPIE project at Imperial College London Arkiveret 6. april 2010 hos Wayback Machine is used to study wire array Z-pinch implosions.

[1] Se for eksempel, Buneman, O., "The Bennett Pinch" (1961) Plasma Physics, Edited by James E. Drummond. LOC 60-12766. Publ. McGraw-Hill, Inc., New York, 1961, p.202

[2] Lee, S., "Energy balance and the radius of electromagnetically pinched plasma columns" (1983) Plasma Physics, Volume 25, Issue 5, pp. 571–576 (1983).

[3] Schmidt, Helmut, "Formation of a Magnetic Pinch in InSb and the Possibility of Population Inversion in the Pinch" (1966) Physical Review, vol. 149, Issue 2, pp. 564–573

[4] Severnyi, A. B., "On the Appearance of Cosmics Rays in the Pinch Effect in Solar Flares" (1959) Soviet Astronomy, Vol. 3, p.887

[5] Zueva, N. M.; Solov'ev, L. S.; Morozov, A. I. "Nonlinear instability of plasma pinches" (1976) Journal of Experimental and Theoretical Physics Letters, Vol. 23, p.256

[6] Rai, J.; Singh, A. K.; Saha, S. K, "Magnetic field within the return stroke channel of lightning" (1973) Indian Journal of Radio and Space Physics, vol. 2, Dec. 1973, p. 240-242.

[7] Galperin, Iu. I.; Zelenyi, L. M.; Kuznetsova, M. M. "Pinching of field-aligned currents as a possible mechanism for the formation of raylike auroral forms" (1986) Kosmicheskie Issledovaniia (ISSN 0023-4206), vol. 24, Nov.-Dec. 1986, p. 865-874. på russisk.

[8] Syrovatskii, S. I. "Pinch sheets and reconnection in astrophysics" (1981) In Annual review of astronomy and astrophysics. Volume 19. (A82-11551 02-90) Palo Alto, CA, Annual Reviews, Inc., 1981, p. 163-229

[9] Airapetyan, V. S.; Vikhrev, V. V.; Ivanov, V. V.; Rozanova, G. A. "Pinch Mechanism of Energy Release of Stellar Flares" (1990) Astrophsyics (Tr. Astrofizika) v.32 No.3 Nov. p.230 1990

[10] For eksempel, se (webarchive-backup) "Electromagnetic Crusher"

[11] Stoneridge Engineering – Theory of Operation of the Quarter Shrinker Citat: "...In an opinion letter, the US Mint "frowns on the despicable practice" of altering coins, but they agree that it is quite legal to shrink coins. Note that this may not be the case within other countries! For example, in the UK and Australia, defacing the Queen's image on a coin may be considered a punishable offense..."

[12] Stoneridge Engineering: The Reconstructed History of Quarter Shrinking

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