View source for Physics:JT-60

{{Short description|Japanese tokamak}}
{{Infobox fusion devices
|name                 = JT-60
|fullname             = Japan Torus-60
|image                =
|imagetitle           =
|type                 = [[Physics:Tokamak|Tokamak]]
|city                 = Naka
|state                = Ibaraki Prefecture
|country              = {{wipe|Japan}}
|coordinates          = <!-- {{coord|latitude|longitude|type:city|display=inline,title}} -->
|affiliation          = [[Organization:Japan Atomic Energy Agency|Japan Atomic Energy Agency]]
|major_radius         = {{cvt|3.4|m}}
|minor_radius         = {{cvt|1.0|m}}
|volume               = {{val|90|ul=m3}}
|field                = {{cvt|4|T}} (toroidal)
|heating              =
|temperature          =
|power                =
|time                 = {{val|65|ul=s}}
|current              =
|construction_date    =
|operation_start_year = 1985
|operation_end_year   = 2010
|ongoing              =
|prev                 = JFT-2M
|next                 = JT-60SA
|related              = [[Physics:Tokamak Fusion Test Reactor|TFTR]]
|website              = <!-- {{url|insert here}} -->
|other_links          =
}}
'''JT-60''' (short for '''Japan Torus-60''') is a large research [[Physics:Tokamak|tokamak]], the flagship of {{wipe|Japan}}'s magnetic fusion program, previously run by the Japan Atomic Energy Research Institute (JAERI) and later by the [[Organization:Japan Atomic Energy Agency|Japan Atomic Energy Agency]]'s (JAEA) Naka Fusion Institute in Naka, Ibaraki Prefecture.<ref>{{cite web |url=http://www.naka.jaea.go.jp/english/NAKA-HPe.html |title=Archived copy |website=www.naka.jaea.go.jp |access-date=14 January 2022 |archive-url=https://web.archive.org/web/20070701014102/http://www.naka.jaea.go.jp/english/NAKA-HPe.html |archive-date=1 July 2007 |url-status=dead}}</ref> As of 2023 the device is known as '''JT-60SA''' and it is the largest operational superconducting tokamak in the world to date,<ref name="first">{{cite web |title=First plasma 23 October |url=https://www.jt60sa.org/wp/first-plasma-23-october/ |website=JT-60SA |date=24 October 2023 |access-date=15 November 2023}}</ref> and was built and is operated jointly by the [[Social:European Union|European Union]] and Japan.<ref name="JT-60SA">{{cite web |title=What is JT-60SA? |url=https://www.jt60sa.org/wp/ |website=JT-60SA |access-date=15 November 2023}}</ref> SA stands for super advanced tokamak, including a D-shaped [[Physics:Plasma|plasma]] [[Cross section (geometry)|cross-section]], superconducting coils, and active feedback control.

==Original design==
JT-60 was first designed in the 1970's as the "'''Breakeven Plasma Test Facility'''" ('''BPTF'''),<ref>{{Cite news |last=Arnoux |first=Robert |date=31 May 2011 |title=Taking the Big Leap |url=https://www.iter.org/newsline/179/731 |url-status=live |access-date=24 January 2024 |work=ITER Newsline}}</ref> a scaled-up version of the JFT-2M<ref>{{Cite web |title=JFT-2M Project {{!}} Introduction of JFT-2M - National Institutes for Quantum Science and Technology |url=https://www.qst.go.jp/site/jt60-english/6685.html |access-date=2024-01-24 |website=www.qst.go.jp}}</ref> aimed at achieving [[Physics:Fusion energy gain factor|breakeven fusion power]]. It began operations in 1985, and much like the {{wipe|United States}}'s [[Physics:Tokamak Fusion Test Reactor|TFTR]] and the {{wipe|United Kingdom}}'s [[Physics:Joint European Torus|JET]] that began operations only shortly before it with similar goals, JT-60 demonstrated performance far below predictions.

Over the next two decades, JET and JT-60 led the effort to regain the performance originally expected of these machines. JT-60 underwent two major modifications during this time, producing '''JT-60A'''{{When|date=January 2024}}, and then '''JT-60U''' (for "upgrade") in 1991.<ref>{{cite book|title=FUSION - Future Energy of the Earth|author=Naka Fusion Institute|publisher=Japan Atomic Energy Agency|page=12|date=June 2008|access-date=25 January 2024|url=https://www.qst.go.jp/uploaded/attachment/5304.pdf}}</ref> These changes resulted in significant improvements in plasma performance. {{Asof|2018}}, JT-60 currently holds the record for the highest value of the fusion triple product achieved: {{val|1.77|e=28|u=[[Kelvin|K]]·[[Second|s]]·m<sup>−3</sup>}} = {{val|1.53|e=21|u=[[Physics:Electronvolt|keV]]·s·m<sup>−3</sup>}}.<ref name=jt60site>{{cite web|url=https://www-jt60.naka.qst.go.jp/english/jt60/project/html/history.html |title=JT-60 HOME PAGE |publisher=[[Organization:Japan Atomic Energy Agency|Japan Atomic Energy Agency]] |access-date=25 April 2021 }}</ref><ref name=JT-60-history>[http://www-jt60.naka.jaea.go.jp/english/jt60/project/html/history.html JT-60 Operational History and the Progress of Plasma Performance] {{webarchive|url=https://web.archive.org/web/20160223140234/http://www-jt60.naka.jaea.go.jp/english/jt60/project/html/history.html |date=2016-02-23 }}</ref>  To date, JT-60 has the world record for the hottest ion temperature ever achieved (522 million °C); this record defeated the TFTR machine at Princeton in 1996.<ref>{{Cite web|url=https://jopss.jaea.go.jp/search/servlet/search?5017810&language=1|title = Plasma physics found in JT-60 tokamak over the last 20 years}}</ref> 

In 2020, JT60 was upgraded to '''JT-60SA'''. In 2021 and 2022, a poloidal field coil short circuit was investigated, and repairs were done.

==JT-60U (Upgrade)==
On October 31, 1996, JT-60U successfully achieved extrapolated breakeven with a factor of ''Q''{{sub|DT}}{{sup|eq}} = 1.05 at {{val|2.8|u=MA}}. Put simply, if the [[Chemistry:Homogeneity and heterogeneity|homogenous]] [[Physics:Deuterium|deuterium]] fuel was theoretically replaced with a 1:1 mix of deuterium and [[Physics:Tritium|tritium]], the fusion reaction would have created an energy output 1.05 times the energy used to start the reaction. JT-60U was not equipped to utilize tritium, as it would add extensive costs and safety risks.

In February 1997, a modification to the [[Physics:Divertor|divertor]] from an open-type shape to a semi-closed W-shape for greater particle and impurity control was started and later completed in May.<ref>{{cite report|title=Annual Report from April 1, 1996 to March 31, 1997|author1=Naka-machi|author2=Naka-gun|author3=Ibaraki-ken|publisher=Naka Fusion Research Establishment|url=https://www.qst.go.jp/uploaded/attachment/7664.pdf|page=1|year=1997|access-date=26 January 2024|quote=The construction for the divertor modification from the original open type to the W-shaped semi-closed type for improving the particle control was started on February 1997.}}</ref><ref>{{cite report|title=Annual Report of Naka Fusion Research Establishment from April 1, 1997 to March 31, 1998|author1=Naka-machi|author2=Naka-gun|author3=Ibaraki-ken|publisher=Naka Fusion Research Establishment|url=https://www.qst.go.jp/uploaded/attachment/7665.pdf|page=1|date=1 October 1998|access-date=26 January 2024|quote=The construction for the divertor modification from the original open type to the W-shaped semi-closed type for improving the particle control was finished in May 1997.}}</ref><ref>{{Cite book |title=Fusion energy 1996. 3 |date=1997 |isbn=978-92-0-103997-2 |series=Publication / Division of Scientific and Technical Information, International Atomic Energy Agency |location=Vienna}}</ref> Experiments simulating the [[Chemistry:Helium|helium]] exhaust in ITER were promptly performed with the modified divertor, with great success. In 1998, the modification allowed JT-60U to reach an extrapolated fusion energy gain factor of ''Q''{{sub|DT}}{{sup|eq}} = 1.25 at {{val|2.6|u=MA}}.<ref>{{cite web |date=7 August 1998 |title=JT-60U Reaches 1.25 of Equivalent Fusion Power Gain |url=http://www-jt60.naka.jaea.go.jp/english/html/exp_rep/rep46.html |archive-url=https://web.archive.org/web/20130106002827/http://www-jt60.naka.jaea.go.jp/english/html/exp_rep/rep46.html |archive-date=6 January 2013 |access-date=5 December 2016}}</ref><ref>{{Cite book |last=Clery |first=Daniel |url=https://books.google.com/books?id=EGcjCQAAQBAJ&pg=PT103&lpg=PT103&dq=JT-60U+q=1.2 |title=A Piece of the Sun: The Quest for Fusion Energy |date=2014-07-29 |publisher=Overlook Press |isbn=978-1-4683-1041-2 |language=en}}</ref><ref>[http://www-pub.iaea.org/mtcd/publications/pdf/csp_001c/pdf/ex1_2.pdf HIGH PERFORMANCE EXPERIMENTS IN JT-60U REVERSED SHEAR DISCHARGES]</ref>

In December 1998, a modification to the vacuum pumping system that began in 1994 was completed. In particular, twelve turbomolecular pumps with oil [[Physics:Bearing (mechanical)|bearings]] and four oil sealed rotary vacuum pumps were replaced with [[Physics:Magnetic levitation|magnetically suspended]] turbomolecular pumps and dry vacuum pumps. The modification reduced the 15-year-old system's consumption of [[Chemistry:Liquid nitrogen|liquid nitrogen]] by two thirds.<ref>{{cite report|url=https://www.qst.go.jp/uploaded/attachment/7666.pdf|title=Annual Report of Naka Fusion Research Establishment from April 1, 1998 to March 31, 1999}}</ref>

In [[Physics:Fiscal year|fiscal year]] 2003, the plasma discharge duration of JT-60U was successfully extended from {{val|15|u=s}} to {{val|65|u=s}}.<ref>{{cite report|url=https://www.qst.go.jp/uploaded/attachment/7659.pdf|title=Annual Report of Naka Fusion Research Establishment from April 1, 2003 to March 31, 2004}}</ref>

In 2005, ferritic steel (ferromagnet) tiles were installed in the vacuum vessel to correct the magnetic field structure and hence reduce the loss of fast ions.<ref name=long2006>{{cite press release |url=http://www.jaea.go.jp/english/news/p06052303/index.shtml |title=Achievement of long sustainment of a high-confinement, high-pressure plasma in JT-60 - A big step towards extended burn in ITER with the use of ferritic steel - |agency=[[Organization:Japan Atomic Energy Agency|Japan Atomic Energy Agency]] |date=9 May 2006 |access-date=5 December 2016}}</ref><ref>[http://www.jaea.go.jp/english/news/p06052303/all.jpg ferromagnet diagrams]</ref> 
The JAEA used new parts in the JT-60, having improved its capability to hold the plasma in its powerful toroidal magnetic field.

Sometime in 2007-2008, in order to control plasma pressure at the pedestal region and to evaluate the effect of fuel on the self-organization structure of plasma, a [[Supersonic speed|supersonic]] [[Physics:Molecular beam|molecular beam]] injection (SMBI) system was installed in JT-60U. The system's design was a collaboration between [[Physics:Cadarache|Cadarache]], [[Organization:French Alternative Energies and Atomic Energy Commission|CEA,]] and JAEA.<ref>{{cite report |url=https://www.qst.go.jp/uploaded/attachment/7663.pdf |title=Annual Report of Fusion Research and Development Directorate of JAEA from April 1, 2007 to March 31, 2008 |date=20 October 1998 |page=18 |access-date=30 January 2024}}</ref>

==JT-60SA==
It was planned for JT-60 to be disassembled and then upgraded to JT-60SA by adding niobium-titanium [[Physics:Superconducting|superconducting]] coils by 2010.<ref name=jt60site/><ref name=JAR2007>{{cite web |url=http://www-jt60.naka.jaea.go.jp/english/annual/07/html/I.JT-60.html |title=JAEA 2006-2007 annual report |quote="3.1.3 Machine Parameters : A bird's eye view of JT-60SA is shown in Fig. I.3.1-1. Typical parameters of JT-60SA are shown in Table I.3.1-1. The maximum plasma current is 5.5 MA with a relatively low aspect ratio plasma (Rp=3.06 m, A=2.65, κ95=1.76, δ95=0.45) and 3.5 MA for an ITER-shaped plasma (Rp=3.15 m, A=3.1, κ95=1.69, δ95=0.36). Inductive operation with 100s flat top duration will be possible within the total available flux swing of 40 Wb. The heating and current drive system will provide 34 MW of neutral beam injection and 7 MW of ECRF. The divertor target is designed to be water-cooled in order to handle heat fluxes up to15 MW/m2 for long time durations. An annual neutron budget of 4x1021 neutrons is foreseen" |access-date=2016-02-16 |archive-url=https://web.archive.org/web/20130106154327/http://www-jt60.naka.jaea.go.jp/english/annual/07/html/I.JT-60.html#I_3.3 |archive-date=2013-01-06 |url-status=dead }} lots of detail on JT-60SA in section 3</ref> 
It was intended for the JT60SA to be able to run with the same shape plasma as [[Organization:ITER|ITER]].<ref name=JAR2007/>{{rp|3.1.3}} The central solenoid was designed to use niobium-tin (because of the higher (9 T) field).<ref name=JAR2007/>{{rp|3.3.1}}

Construction of the tokamak officially began in January 2013,<ref>{{Cite book |url=https://www.qst.go.jp/uploaded/attachment/20800.pdf |title=JT-60SA - Toward the Realization of Fusion Energy |date=January 2021 |page=3 |access-date=26 January 2024}}</ref> and it was to continue until 2020 with first plasma planned in September 2020.<ref>{{cite web |url=http://www.jt60sa.org/b/index_nav_1.htm?n1/introduction.htm |title=The JT-60SA project Introduction |publisher=[[Organization:Japan Atomic Energy Agency|Japan Atomic Energy Agency]] |access-date=6 March 2018 |archive-date=5 March 2016 |archive-url=https://web.archive.org/web/20160305025820/http://www.jt60sa.org/b/index_nav_1.htm?n1%2Fintroduction.htm |url-status=dead }}</ref> Assembly was completed in the spring of 2020,<ref>{{cite web|url=http://www.jt60sa.org/b/index_news113.htm?news113/news113.php|title=JT-60SA: World's largest superconducting tokamak completed!|publisher=National Institutes for Quantum and Radiological Science and Technology|date=April 2020|series=Newsletter 113}}</ref> and in March 2021 it reached its full design toroidal field successfully, with a current of 25.7kA.<ref>{{Cite web|title=02.03.2021 – JT-60SA successfully reaches its full design toroidal field – JT-60SA|url=https://www.jt60sa.org/wp/02-03-2021-jt-60sa-successfully-reaches-its-full-design-toroidal-field/|access-date=2021-03-19|language=en-GB|archive-date=2021-03-02|archive-url=https://web.archive.org/web/20210302144918/https://www.jt60sa.org/wp/02-03-2021-jt-60sa-successfully-reaches-its-full-design-toroidal-field/|url-status=dead}}</ref> A test of the poloidal field coils in March 2021 suffered a short circuit leading to a lengthy investigation and repair.<ref name=pfc-sc-2022>[https://fusionforenergy.europa.eu/news/team-spirit-resilience-and-adaptability-key-to-jt-60sa-repairs/ ''Team spirit, resilience, and adaptability key to JT-60SA repairs'' 28 Nov 2022]</ref>

Repairs were completed in May 2023 and preparations for operation began.<ref>{{cite web |title=Operations restart with vacuum pumping on 30.05.2023 |url=https://www.jt60sa.org/wp/operations-restart-with-vacuum-pumping-on-30-05-2023/ |website=JT-60SA |date=5 June 2023 |access-date=15 November 2023}}</ref> First plasma was achieved on 23 October 2023 making JT-60SA the largest operational superconducting tokamak in the world to date.<ref name="first"/>
The reactor was declared active on 1 December 2023.  <ref>EU Press release https://energy.ec.europa.eu/news/eu-and-japan-celebrate-start-operations-jt-60sa-fusion-reactor-and-reaffirm-close-cooperation-fusion-2023-12-01_en</ref>

==References==
{{Reflist}}

==External links==
* of the JT-60
* of the JT-60SA
* [https://web.archive.org/web/20100817185757/http://www-jt60.naka.jaea.go.jp/english/jt60/project/html/parameter.html JT-60 diagram and parameters]
* [https://web.archive.org/web/20070908014439/http://www.jaea.go.jp/jaeri/english/index.html JAERI (English)]
* [http://www.yomiuri.co.jp/dy/features/science/20060511TDY04004.htm JT-60's Newly Achieved Plasma Record (Japanese) ] {{Webarchive|url=https://web.archive.org/web/20060603155534/http://www.yomiuri.co.jp/dy/features/science/20060511TDY04004.htm |date=2006-06-03 }}
* [https://web.archive.org/web/20130106002319/http://www-jt60.naka.jaea.go.jp/english/html/exp_rep/rep36.html World Highest Fusion Triple Product Marked in High-βp H-mode Plasmas - Aug 1996] 1.5*10<sup>21</sup> m<sup>−3</sup> s keV

{{fusion experiments}}

[[Category:Tokamaks]]

{{Sourceattribution|JT-60}}