Lawrence Livermore National Laboratory

LLNL physicists, chemists, and engineers leverage powerful tools in the accelerator complex to address evolving national security challenges.

Nuclear physics research at LLNL encompasses a broad range of experimental capabilities, where researchers study subatomic particles that play a key role in our national security mission. LLNL’s investigators design, test, and refine new tools that enable them to detect isotopes; explore the structure of unstable nuclei; confine and measure radioactive ions; analyze fission reactions; and understand neutron scattering.

Our teams continue expanding and enhancing our suite of world-class instruments, offering new research opportunities at the frontier of nuclear and particle physics.

Neutron imaging system

Working with the neutron imaging system

Our neutron imaging system is based on a deuterium-deuterium fusion reaction, where fast neutrons are produced through deuteron bombardment. The radiographic technique is used to penetrate thick, dense objects and produce images of interior features—offering a robust, non-destructive evaluation tool.

In addition, the system’s neutron source capability plays a key role in research involving nuclear cross-section measurements, material assay via gamma-ray spectroscopy, and studies of radiation effects on material performance.

The state-of-the-art, fast neutron source includes two deuteron ion accelerators, a fully instrumented beamline, an advanced optics system, and high-power neutron production targets. It fits in a 5,000-square-foot space and offers powerful, sub-millimeter radiographic imaging.

PRISM accelerator

The PRISM accelerator

LLNL’s Photonuclear Reactions for Isotopic Signature Measurements (PRISM) accelerator provides unique experimental capabilities in experimental nuclear physics, accelerator physics, detector development, and nuclear reaction modeling. Coupled with a bremsstrahlung converter, PRISM operates as a high-energy, high-intensity photon source for a range of applications. In support of stockpile stewardship and national security missions, LLNL scientists can use the PRISM system to measure photo-nuclear cross sections and infer quantities of interest for a variety of nuclear materials. The system’s flexibility for measurements at lower energies supports important physics research that addresses both programmatic and fundamental science needs.

PRISM generates high-energy x-rays, which then interact with nuclei. Detectors measure particles generated by the neutron-induced reactions. For example, PRISM’s photofission-based neutron source can be used to:

  • Identify isotopes by measuring the delayed neutron-decay signatures of actinides.
  • Determine photonuclear cross sections by scanning particles across various energies.
  • Conduct experiments aimed at understanding neutron scattering.

PRISM can accelerate electrons up to 25 MeV. However, by tuning the accelerator to low-electron energy, it can also be used to study radiation effects, support radiochemistry research, or analyze medical isotope production.

Mono-Energetic Gamma-Ray (MEGa-ray) Test Station

The MEGa-ray test station

MEGa-ray is a state-of-the-art electron accelerator developed as a Laser-Compton light source using a high-gradient X-band, photoinjector-based accelerator. Originally used for Laser-Compton experiments and related research, LLNL scientists adapted the technology to support a broader range of physics research and applications.

The system begins with short, picosecond laser pulses that produce short electron bunches on the photocathode, with the X-band accelerator boosting the energy of the electrons. These highly energetic electron bunches collide with separate laser photons, which gain energy from their Compton-scattering interaction. This scattered x-ray radiation is Doppler upshifted in energy and directed forward in a narrow-bandwidth photon beam.

The light source can be tuned to different wavelengths so that it predominantly interacts with only one kind of material—in a process known as isotope-specific nuclear photonics. The beam can penetrate through lead and other thick containers, enabling researchers to non-destructively detect, image, and assay specific objects of interest, such as nuclear waste canisters, nuclear fuel rods, and other objects that might house uranium or plutonium.