From Wikipedia, the free encyclopedia
Jump to: navigation, search
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)

JT-60 (JT stands for Japan Torus) 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, if the D–D fuel were replaced with a 1:1 mix of deuterium and tritium (D–T fuel), have exceeded break-even—the point where the power produced by the fusion reactions equals the power supplied to operate the machine. JT-60 does not have the facilities to handle tritium; currently only the JET tokamak in the United Kingdom has such facilities. 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.[4][1][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.


In 2010 JT-60 is being disassembled to be upgraded to JT-60SA by using niobium-titanium superconducting coils.[1][8] Construction of JT-60SA was underway in 2015 and will continue until 2018 with first plasma in 2019.[9]


External links[edit]