Fusion glossary
B
The flight tube connecting the neutral beam box to the plasma torus. Sometimes, colloquially, the complete beam system including the beam box.
A thick wall of concrete surrounding the cryostat and designed to absorb the bulk of the remaining neutron radiation from the plasma. The wall shields the region outside the cryostat so that it can be accessed, at maximum a couple of weeks after shutdown, for major hands-on repairs.
The blanket, composed of the shield block module and the first wall, covers the interior surfaces of the vacuum vessel, providing shielding to the vessel and the superconducting magnets from the heat and neutron fluxes of the fusion reaction. The neutrons are slowed down in the blanket, where their kinetic energy is transformed into heat energy and collected by the coolants. In a fusion power plant, this energy will be used for electrical power production. In °ÄÃÅÁùºÏ²Ê¸ßÊÖ, some of the 440 individual blanket modules will be used to test materials for tritium breeding concepts.
The point where the amount of energy produced by fusion equals the energy required to fuel the reaction (Q = 1).
If blanket modules contain lithium, a reaction occurs: the incoming neutron is absorbed by the lithium atom, which recombines into an atom of tritium and an atom of helium. The tritium can be removed from the blanket and recycled into the plasma as fuel. Blankets containing lithium are thus considered to be "breeding blankets" for tritium. Within the fusion reaction, tritium can be 'bred' indefinitely. This will be an important technology for future fusion power reactors.
A number of different combinations of tritium breeding material, neutron multiplier, structural material, and coolant will be tried out on °ÄÃÅÁùºÏ²Ê¸ßÊÖ to determine the best combination for tritium and power production. Each one of these solutions is referred to as a "breeding technology". A future fusion plant producing large amounts of power will be required to breed all of its own tritium; °ÄÃÅÁùºÏ²Ê¸ßÊÖ will test this essential concept of tritium self-sustainment.
An agreement for complementary research and development between the European Atomic Energy Community (Euratom) and the Japanese government. Signed in 2007 and renewed in 2020, the Broader Approach establishes a framework for advanced research and development in support of °ÄÃÅÁùºÏ²Ê¸ßÊÖ and the next-stage device, DEMO.
The period of roughly constant and maximum fusion power during the plasma pulse.
A plasma in which the energy of the helium nuclei (alpha particles) produced by the fusion reaction is enough to maintain the temperature of the plasma; the external heating methods can then be strongly reduced or switched off altogether. A burning plasma in which at least 50 percent of the energy to drive the fusion reaction is generated internally is an essential step to reaching the goal of fusion power generation. At Q = 10 (°ÄÃÅÁùºÏ²Ê¸ßÊÖ), approximately 66% of the plasma heating is contributed by the alpha particles.