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Type Tokamak
Operation date 1985–2010
Size (Major radius/Minor Radius 3.4 meters (11 ft)/1.0 meter (3 ft 3 in)
Plasma volume 90 m3 (3,200 cu ft)
Magnetic field 4 T (toroidal)
Location Ibaraki Prefecture, Japan

JT-60 (short for Japan Torus-60) is the flagship of Japan's magnetic fusion program, previously run by the Japan Atomic Energy Research Institute (JAERI) and currently run by the Japan Atomic Energy Agency's (JAEA) Naka Fusion Institute [1] in Ibaraki Prefecture, Japan. In operation since 1985, it currently holds the record for the highest value of the fusion triple product achieved: 1.77×1028 K·s·m−3 = 1.53×1021 keV·s·m−3.[1][2]

JT-60 is a typical Tokamak with a D-shaped poloidal cross-section, similar to JET. Experimental results obtained by the reactor may be of importance to the ITER experiment as well as future tokamaks.

During deuterium (D–D fuel) plasma experiments in 1998, plasma conditions were achieved which would have achieved break-even—the point where the power produced by the fusion reactions equals the power supplied to operate the machine—if the D–D fuel were replaced with a 1:1 mix of deuterium and tritium (D–T fuel). JT-60 does not have the facilities to handle tritium; only the JET tokamak in the United Kingdom has such facilities currently. In fusion terminology, JT-60 achieved conditions which in D–T would have provided Q = 1.25, where Q is the ratio of fusion power to input power.[3] A self-sustaining nuclear fusion reaction would need a value of Q that is greater than 5.[1][4][5]

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.[6][7]

On May 9, 2006, the JAEA announced that the JT-60 had achieved a 28.6 second plasma duration time.[6] The JAEA used new parts in the JT-60, having improved its capability to hold the plasma in its powerful toroidal magnetic field. The main future objective of JT-60 is to realize high-beta steady-state operation in the use of reduced radio-activation ferritic steel in a collision-less regime.


It was planned for JT-60 to be disassembled and then upgraded to JT-60SA by adding niobium-titanium superconducting coils by 2010.[1][8] Construction of JT-60SA did not officially begin until 2015, and will continue until 2018 with first plasma in 2019.[9]


  1. ^ a b c "JT-60 HOME PAGE". Japan Atomic Energy Agency. Archived from the original on 8 December 2015. Retrieved 5 December 2015. 
  2. ^ JT-60 Operational History and the Progress of Plasma Performance
  3. ^ "JT-60U Reaches 1.25 of Equivalent Fusion Power Gain". 7 August 1998. Archived from the original on 6 January 2013. Retrieved 5 December 2016. 
  4. ^ "NSTX Research Program Five Year Plan for 2009-2013" (PDF). National Spherical Torus Experiment website. p. 24. Retrieved 5 December 2015. 
  5. ^ Wesson, John (November 1999). "The Science Of JET" (PDF). EUROfusion. Retrieved 5 December 2015. 
  6. ^ a b "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 -" (Press release). Japan Atomic Energy Agency. 9 May 2006. Retrieved 5 December 2016. 
  7. ^ ferromagnet diagrams
  8. ^ JAEA 2006-2007 annual report lots of detail on JT-60SA
  9. ^ "The JT-60SA project Introduction". Japan Atomic Energy Agency. Retrieved 5 December 2015. 

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