The Laboratory in the News

Petawatt Laser System Fully Integrated

The High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) was recently declared to be fully operational at the European Union’s Extreme Light Infrastructure (ELI) Beamlines. Forming the facility’s third world-leading laser capability, HAPLS (see below) was developed and built by Lawrence Livermore to be the world’s most powerful diode-pumped petawatt laser system. HAPLS has met the required performance parameters of being able to reach its 1-petawatt, 10-hertz design specification and is ready for integration with experimental systems.

In 2013, conceptual work on HAPLS commenced at the Laboratory, where it was designed, developed, and constructed by the Advanced Photon Technologies Program. In 2016, a Livermore–European team completed construction and final testing at the Laboratory. In 2017, the laser system was disassembled and shipped to ELI in Dolní Břežany, Czech Republic, where it arrived in June of that year.

The system consists of a main petawatt beamline capable of delivering 45 joules of energy per pulse, and is energized by diode-pumped lasers capable of delivering up to 200 joules of energy per pulse. The laser has been commissioned for early experiments at its phase 1 operation point of 16 joules and a 26-femtosecond pulse duration at a 3.3-hertz repetition rate, equivalent to a peak power of approximately 0.5 petawatts after the pulse compressor.

HAPLS represents a major advancement over any other petawatt-class laser system in the world and opens up a new arena of quantitative science, with the potential to develop societally impactful applications for industry and medicine.
Contact: Constantin Haefner (925) 422-1167 (haefner2 [at] llnl.gov (haefner2[at]llnl[dot]gov)).

Understanding the Universe through Neutrinos

Livermore scientists are part of a team that proposed the next-generation Enriched Xenon Observatory (nEXO) experiment for providing a two-orders-of-magnitude increase over current limits in sensitivity to neutrinoless double-beta decay (NDBD) half-life. Determining features of the neutrino by observing NDBD—an extremely rare nuclear process—could provide an explanation for the puzzling overabundance of matter over antimatter in the universe. Studying NDBD could also reveal physics that would confirm the existence of a new elementary particle, the Majorana fermion. This discovery could reshape the Standard Model of particle physics and lead to a better understanding of neutrinos and their role in the universe’s evolution. The design of the nEXO detector—a 5-ton liquid-xenon time-projection chamber using 90 percent enriched xenon-136—takes advantage of advanced technology for the next phase of NDBD research. The Laboratory research behind the experiment appears in the June 2018 issue of Physical Review C.

“A competitive two-orders-of-magnitude increase in NDBD half-life sensitivity over current experiments is possible using the nEXO detector,” states Livermore scientist Samuele Sangiorgio, lead author of the team’s paper. “We now have great confidence in nEXO’s design and approach, and we could have a real chance at measuring this rare event.” Scientists expect to base discovery on observing only a dozen or so decays in a decade-long experiment. This very low signal rate means false signals from background radiation and cosmic rays must be suppressed as much as is feasible—a goal that the new experiment design will help achieve.
Contact: Samuele Sangiorgio (925) 422-6439 (sangiorgio1 [at] llnl.gov (sangiorgio1[at]llnl[dot]gov)).

Hydrodynamic Instabilities Elucidated

Researchers at Lawrence Livermore and the University of Michigan reported on recent experiments and techniques designed to improve the understanding and control of hydrodynamic instabilities in high-energy-density (HED) settings, such as those that occur in inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF). In the June 2018 issue of Proceedings of the National Academy of Sciences, the team describes four areas of HED research that focus on Rayleigh–Taylor (RT) instabilities. This phenomenon arises when two fluids or plasmas of different densities are accelerated together, with the lower density fluid pushing and accelerating the higher density one. RT instabilities can degrade NIF implosion performance by amplifying target defects and causing perturbations through engineering features, such as the tents used to suspend the target capsule in the hohlraum and the fill tube that injects fusion fuel into the capsule.

The paper summarizes a wide range of studies about HED RT instabilities relevant not only to ICF but also astrophysics, planetary science, and hypervelocity impact dynamics. The researchers state that the studies, although aimed primarily at improving understanding of stabilization mechanisms in RT growth within NIF implosions, also offer unique opportunities to study other phenomena that typically can be found only in high-energy astrophysics, astronomy, and planetary science, such as the interiors of planets and stars, the dynamics of planetary formation, supernovae, cosmic gamma-ray bursts and galactic mergers.
Contact: Bruce Remington (925) 423-2712 (remington2 [at] llnl.gov (remington2[at]llnl[dot]gov)).