Fixed-field alternating gradient accelerator: Difference between revisions

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</noinclude></noinclude>{{Expand Russian|FFAG|date=May 2012}}

A '''Fixed-Field Alternating Gradient accelerator''' ('''FFAGFFA''') is a circular [[particle accelerator]] concept on which development was started in the early 50s, and that can be characterized by its time-independent magnetic fields (''fixed-field'', like in a [[cyclotron]]) and the use of [[strong focusing]] (''alternating gradient'', like in a [[synchrotron]]).<ref name=briefhistory>{{Cite journal

| last1 = Ruggiero

| first1 = A.G.

| title = Brief History of FFAGFFA Accelerators

| journal = Bnl-75635-2006-Cp

| date = Mar 2006

| url = http://www.bnl.gov/isd/documents/31130.pdf

}}</ref><ref>{{cite journal | author=Daniel Clery | date=4 January 2010 | title=The Next Big Beam? | journal=[[Science (journal)|Science]] | volume=327 |pages=142–143 | doi=10.1126/science.327.5962.142 | pmid=20056871 | bibcode = 2010Sci...327..142C | issue=5962 | url = | format = | accessdate = }}</ref> Thus, FFAGFFA accelerators combine the cyclotron's advantage of continuous, unpulsed operation, with the synchrotron's relatively inexpensive small magnet ring, of narrow bore.

Although the development of FFAGsFFAs had not been pursued for over a decade starting from 1967, it has regained interest since the mid-1980s for usage in [[neutron]] [[spallation]] sources, as a driver for [[muon]] colliders <ref name=briefhistory /> and to accelerate muons in a [[Neutrino Factory|neutrino factory]] since the mid-1990s.

The revival in FFAGFFA research has been particularly strong in Japan with the construction of several rings. This resurgence has been prompted in part by advances in [[Radio frequency|RF]] cavities and in magnet design.<ref name=mori2004>{{Cite journal

| first1 = Y. | last1 = Mori

| title = Developments of FFAGFFA Accelerator

| journal = Proceedings of FFAG04 /

| year = 2004

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===First development phase===

[[File:MichiganFFAGmark1.jpg|thumb|The Michigan Mark I FFAGFFA accelerator. This 400KeV electron accelerator was the first operational FFAGFFA accelerator. The large rectangular part on the right is the [[betatron]] transformer core.]]

The idea of fixed-field alternating-gradient synchrotrons was developed independently in Japan by [[Tihiro Ohkawa]], in the United States by [[Keith Symon]], and in Russia by [[Andrei Kolomensky]]. The first prototype, built by [[Lawrence W. Jones]] and [[Kent M. Terwilliger]] at the [[University of Michigan]] used [[betatron]] acceleration and was operational in early 1956.<ref>Lawrence W. Jones, Kent M. Terwilliger, [http://inspirehep.net/record/38999/files/MURA-104.pdf A Small Model Fixed Field Alternating Gradient Radial Sector Accelerator], Technical Report MURA-LWJ/KMT-5 (MURA-104), April 3, 1956; contains photos, scale drawings and design calculations.</ref> That fall, the prototype was moved to the [[Midwestern Universities Research Association]] (MURA) lab at [[University of Wisconsin]], where it was converted to a 500&nbsp;keV electron [[synchrotron]].<ref name=JonesTerwilliger>{{Cite book | last1 = Jones | first1 = L. W. | chapter = Kent M. Terwilliger; graduate school at Berkeley and early years at Michigan, 1949–1959| title = Kent M. Terwilliger memorial symposium, 13−14 Oct 1989| series = [[AIP Conference Proceedings]] | doi = 10.1063/1.41146 | publisher = | volume = 237 | pages = 1–21| year = 1991 | pmid = | pmc = }}</ref> Symon's patent, filed in early 1956, uses the terms "FFAG accelerator" and "FFAG synchrotron".<ref>{{US patent reference

| number = 2932797