A promising approach to inertial fusion energy, called heavy-ion fusion (HIF), has long been advocated by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).
In inertial fusion, the fuel is a solid target made of frozen isotopes of hydrogen (deuterium, or deuterium and tritium), which is instantly heated to fusion temperature when hit by driver beams of laser light or energetic particles. The heavy-ion fusion approached pursued at Berkeley Lab uses driver beams of ions (atoms lacking one or more electrons) whose atomic mass is generally greater than 100 – cesium or xenon, for example.
A target in an inertial fusion reaction chamber is bathed in x-rays that ablate its surface, causing a rocket effect that squeezes and heats the target until it ignites and burns. For continuous power production, new targets would be injected into the chamber five to 10 times each second.
The unifying motivations and major challenges for further research into HIF have been noted by various high level reviews:
• Heavy ions of mass ~100 amu and ion kinetic energy ≥ 1 GeV have a stopping range suitable to drive IFE targets with yield over 100 MJ and gain of over 50 times.
• A heavy-ion driver must deliver 1–10 MJ of energy, properly shaped, at a peak power over 100 Terawatts at about 10 Hz (10 times per second).
• Near the source and near the target multiple beams are desired for physics reasons. For the induction linac approach, multiple beams are desired for economic reasons. Because of the high charge per bunch, the adopted approach is to accelerate a longer bunch and then compress it to the short length required at the target.
• The beams’ quality and alignment must be such that they can be focused onto the target to a radius of a few millimeters from a distance of several meters.
• Limitations due to space charge, emittance growth, beam-gas, and beam-plasma interactions must be sufficiently controlled throughout the driver.
• Nuclear and high energy physics accelerators, with total beam energy of over 1 MJ have separately exhibited intrinsic efficiencies, pulse repetition rates (over 100 Hz), power levels (TW), and durability required for HIF.
9:05 am Inertial Fusion Energy: Activities and Plans in the UK and EU, John Collier, UK Science and Technology Facilities Council
10:50 am Inertial Fusion Energy: Activities and Plans in Japan Hiroshi Azechi, Institute of Laser Engineering, Osaka University
1:00 pm Integrated design of a laser fusion target chamber system,
John Sethian, Naval Research Laboratory
8:30 am Nuclear Power Plant Financing Philip M. Huyck, Encite, LLC (formerly of Credit Suisse First Boston and Trust Company of the West)
9:45 am Inertial Fusion Energy: Activities and Plans in China Zhang Jie, President, Shanghai Jiao Tong University