Mirnov oscillations

{{Short description|Magnetic field fluctuations in an ionised gas}}

Mirnov oscillations (a.k.a. magnetic oscillations) are amplitude perturbations of the magnetic field in a plasma. It is named after Sergei V. Mirnov who designed a probe to measure these oscillations in 1965.{{Cite journal|last=Mirnov|first=S. V.|date=1965|title=A probe method for measuring the displacement of the current channel in cylindrical and toroidal discharge vessels|journal=Journal of Nuclear Energy C|language=en|volume=7|issue=3|pages=325–328|doi=10.1088/0368-3281/7/3/112|issn=0368-3281}} The probe name is Mirnov coil.

Mirnov oscillations have been extensively studied in tokamaks{{Cite journal|last1=McGuire|first1=K.|last2=Hammett|first2=G.|date=1982|title=Analysis of Mirnov oscillations on PDX|url=http://inis.iaea.org/Search/search.aspx?orig_q=RN:13701258|language=en}}{{Cite journal|last1=Tan|first1=I. H.|last2=Caldas|first2=I. L.|last3=Nascimento|first3=I. C.|last4=Silva|first4=R. P. Da|last5=Sanada|first5=E. K.|last6=Bruha|first6=R.|date=1986|title=Mirnov Oscillations in a Small Tokamak|journal=IEEE Transactions on Plasma Science|volume=14|issue=3|pages=279–281|doi=10.1109/TPS.1986.4316542|issn=0093-3813|bibcode=1986ITPS...14..279T|s2cid=12920335|url=http://publica-sbi.if.usp.br/PDFs/pd537.pdf }}{{Cite journal|last=Kikuchi|first=M.|date=1986|title=A note on the Mirnov signal analysis in tokamaks|journal=Nuclear Fusion|language=en|volume=26|issue=1|pages=101–107|doi=10.1088/0029-5515/26/1/009|s2cid=122502537 |issn=0029-5515|url=https://digital.library.unt.edu/ark:/67531/metadc1085941/}}{{Cite journal|last1=Raju|first1=D.|last2=Jha|first2=R.|last3=Kaw|first3=P. K.|last4=Mattoo|first4=S. K.|last5=Saxena|first5=Y. C.|last6=Team|first6=Aditya|date=2000-11-01|title=Mirnov coil data analysis for tokamak ADITYA|journal=Pramana|language=en|volume=55|issue=5|pages=727–732|doi=10.1007/s12043-000-0039-8|issn=0973-7111|bibcode=2000Prama..55..727R|s2cid=120615200}} as they provide information about the plasma instabilities that occur within the system.{{Cite journal|author1-link=Alan Herbert Glasser|last1=Glasser|first1=A. H.|last2=Greene|first2=J. M.|last3=Johnson|first3=J. L.|date=1975|title=Resistive instabilities in a tokamak|doi=10.2172/4183368|language=en|osti=4183368|url=https://digital.library.unt.edu/ark:/67531/metadc865177/}}{{Cite journal|last1=Mirnov|first1=S. V.|last2=Semenov|first2=I. B.|date=1971|title=Investigation of the instabilities of the plasma string in the Tokamak-3 system by means of a correlation method|journal=Soviet Atomic Energy|language=en|volume=30|issue=1|pages=22–29|doi=10.1007/BF01788387|s2cid=124432349|issn=1573-8205}}{{Cite journal|last1=Schittenhelm|first1=M.|last2=Zohm|first2=H.|date=1997|title=Analysis of coupled MHD modes with Mirnov probes in ASDEX Upgrade|journal=Nuclear Fusion|language=en|volume=37|issue=9|pages=1255–1270|doi=10.1088/0029-5515/37/9/I06|issn=0029-5515|bibcode=1997NucFu..37.1255S|s2cid=250784804 }} The instabilities create local fluctuations in the current which induce a varying magnetic flux density, and are picked up by the coils due to Faraday's law of induction.