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The National Nuclear Security Administration’s National Ignition Facility (NIF) has set world records for neutron yield and laser energy delivered from laser-driven capsules to an inertial confinement fusion (ICF) target.
NIF researchers will report on these and other recent experimental results this week at the annual meeting of the American Physical Society Division of Plasma Physics in Chicago.
The neutron yield record was set on Oct. 31, when the NIF team fired 121 kilojoules of ultraviolet laser light into a glass target filled with deuterium and tritium (DT) gas.
The shot produced approximately 3 x 1014 (300 trillion) neutrons, the highest neutron yield to date by an inertial confinement fusion facility. Neutrons are produced when the nuclei of deuterium and tritium (isotopes of hydrogen) fuse, creating a helium nucleus and releasing a high-energy neutron.
On Tuesday, Nov. 2, the team fired 1.3 megajoules of ultraviolet light into a cryogenically cooled cylinder called a hohlraum containing a surrogate fusion target known as a symmetry capsule, or symcap. This was the highest-energy laser shot and was the first test of hohlraum temperature and capsule symmetry under conditions designed to produce fusion ignition and energy gain.
Preliminary analysis indicated that the hohlraum absorbed nearly 90 percent of the laser power and reached a peak radiation temperature of 300 electron volts (about 6 million degrees Fahrenheit) — making this the highest X-ray drive energy ever achieved in an indirect drive ignition target.
The experiments followed closely on the heels of NIF’s first integrated ignition experiment on Sept. 29, which demonstrated the integration of the complex systems required for an ignition campaign including a target physics design, the laser, target fabrication, cryogenic fuel layering and target positioning, target diagnostics, control and data systems and tritium handling and personnel and environmental protection systems.
In that shot, one megajoule of ultraviolet laser energy was fired into a cryogenically layered capsule filled with a mixture of tritium, hydrogen and deuterium (THD), tailored to enable the most comprehensive physics results.
NIF will also help advance fusion energy technology, which could be an element of making the United States energy independent.
For more information, visit www.llnl.gov.