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The '''Karlqvist gap''' or '''Karlqvist Field''' is an [[electromagnetism|electromagnetic]] phenomenon discovered in 1953 by the Swedish engineer Olle Karlqvist (1922-1976),<ref name=olle/> which is important in [[magnetic storage]] for computers.<ref name=field>{{Citation|author=Jan Karlqvist |access-date=2010-12-23 |date=1999 |title=The Karlqvist field |url=http://www.treinno.se/pers/okq/field.htm |language=sv }} (HTML 1 kB)</ref>

Karlqvist discovered the phenomenon while designing a [[Ferromagnetism|ferromagnetic]] surface layer to the magnetic [[drum memory]] for the [[BESK]] computer.<ref name=olle>{{Citation|author=Jan Karlqvist |access-date=2010-12-23 |date=1999 |title=Olle Karlqvist, datorpionär och upptäckare av "Karlqvist field"(gap) |trans-title=Olle Karlqvist, computer pioneer and discoverer of the "Karlqvist field"(gap) |url=http://www.treinno.se/pers/okq/index.htm |language=sv }} (HTML 3 kB)</ref> When designing a magnetic memory store, the ferromagnetic layer must be studied to determine the variation of the [[magnetic field]] with [[permeability (electromagnetism)|permeability]], air gap, layer thickness and other influencing factors. The problem is [[Nonlinear system|non-linear]] and extremely difficult to solve. Karlqvist's gap discovery shows that the non-linear problem could be approximated by a linear [[Boundary value problem|boundary value]] for the two-dimensional [[Magnetostatics|static field]] and the one-dimensional [[Transient magnetic field|transient field]]. This linear calculation gives a first approximation. 

Karlqvist published his discovery in the 1954 paper "Calculation of the magnetic field in ferromagnetic layer of a magnetic drum" at [[KTH Royal Institute of Technology]] in [[Stockholm]].<ref name=calcferro>{{Citation|author=Olle Karlqvist |date=1954 |publication-date=2013-07-15 |title=Calculation of the magnetic field in ferromagnetic layer of a magnetic drum |url=http://www.treinno.se/pers/okq/Calculation%20of%20the%20magnetic%20field.pdf |publisher=AB Henrik Lindstahls Bokhandel i distribution |language=sv }} (PDF 741 kB)</ref>

== See also ==
* [[Carousel memory]], 2560-[[kilobyte]] storage unit first sold in 1958

== References ==
<references/>

[[Category:Electromagnetism]]
[[Category:Computer memory]]


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