Inertial Confinement Fusion

Forty-eight final optic assemblies are symmetrically distributed around the upper and lower hemispheres of the target chamber (National  Ignition Facility, Lawrence Livermore National Laboratory)

Forty-eight final optic assemblies are symmetrically distributed around the upper and lower hemispheres of the target chamber (National  Ignition Facility, Lawrence Livermore National Laboratory)

The Office of ICF provides experimental capabilities and scientific understanding in high energy density physics (HEDP) necessary to ensure a safe, secure, and effective nuclear weapons stockpile without underground testing.  The demonstration of laboratory ignition and its use to support the Stockpile Stewardship Program (SSP) is the highest priority goal for this office as well as a high priority goal for NNSA and DOE.  As a core part of the NNSA’s advanced science and technology portfolio, the Office of ICF is working to produce thermonuclear burn conditions in the laboratory, to develop laboratory capabilities that will create and measure extreme conditions of temperature, pressure, and radiation of relevance to nuclear weapons, and to conduct weapons-related research in these environments.

Achieving HEDP conditions is critical to developing and validating advanced theoretical models and codes that are used to characterize weapons performance.  ICF supports other non-ignition SSP campaigns in the design and execution of experiments (at physical conditions approaching those in a nuclear weapon) that are used to validate the advanced physical models and computational capabilities required to support the nuclear weapon stockpile.  ICF’s experimental capabilities are an essential component of the overall NNSA plan to manage the assessment of nuclear performance issues.

This office maintains the world’s preeminent HEDP infrastructure and is committed to the preservation of intellectual and technical competencies in nuclear weapons under a comprehensive test ban.  To this end, ICF uses its experimental facilities, diagnostic techniques, and computational tools to demonstrate ignition in the laboratory, providing the capability to scale data to weapons-relevant parameters, and assessing innovative concepts that could provide long-term support of the SSP.  ICF sustains beneficial international collaborations, including with the United Kingdom and France.

Inertial Confinement Fusion
In the ICF process, a tiny sphere (known as the capsule or pellet), ranging in size from a pinhead to a small pea, is filled with a mixture of two isotopes of hydrogen (deuterium (D) and tritium (T)) and is subjected to a sudden application of intense pressure and high temperature (Figure 1a).  The pressure is provided either directly by the light of a laser, by the conversion of laser light into x-rays, or by an x-ray generating device such as a Z-pinch machine.  This pressure forces rapid heating and a subsequent ablation (blow-off) of some of the material of the outer layer of the capsule/pellet (Figure 1b).  This ablation produces an opposing force (rocket effect) that results in a fast inward compression of the remaining material that heats the interior of the fuel (D and T) forcing the two isotopes to fuse (ignition) (Figure 1c).  The ignition of the core spreads to the remaining fuel and generates additional energy that blows the capsule apart (Figure 1d).

Under proper conditions, the energy released through compression and burning of the fuel will significantly exceed the energy used to implode the capsule.  Thermonuclear fusion by inertial confinement offers the prospect of a long-term energy source based on a secure and essentially limitless fuel.

In many respects, this process is similar to the process by which the Sun produces its energy, though the Sun system uses gravitational confinement.

inertial confinement fusion concept            This ICF concept specifies laser energy; however, the process is the same when used with other drivers.