Petawatt laser system passes key milestone

27 Jan 2016

Lawrence Livermore, developing HAPLS system for ELI Beamlines, reports power breakthrough - two months early.

The High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) under construction at Lawrence Livermore National Laboratory, Livermore, CA, US, has achieved a key average power milestone more than two months ahead of schedule, and is now moving into the next phase in its development.

The HAPLS high-energy diode-pumped solid-state pump laser, firing at a repetition rate of 3.3 Hz produced 70J of infrared (1053nm) energy and 39J of green (527nm) energy. Completion of this average-power milestone marks another major step in the HAPLS commissioning plan, say its developers: the beginning of the integration of the pump laser with the HAPLS high-energy short-pulse beamline, destined for the new ELI Beamlines facility in Prague, Czech Republic.

The ELI Beamlines facility will be a high-energy, high repetition-rate laser pillar of the overall ELI project. It will provide pulses from four laser systems. To meet the requirement for high repetition rates, three of these lasers will employ the state of the art technologies of diode-pumped solid state lasers (DPSSL) for driving broadband amplifiers. The fourth, multi-kilojoule laser will use a newly-developed flash lamp technology with an actively cooled gain medium.

Constantin Haefner, program director for Advanced Photon Technologies at LLNL commented, “Ramping the pump laser to this intermediary performance level was an important step for HAPLS. For the first time we ran the pump laser at significant energy and average power levels, meeting and exceeding the required goals for this milestone. This accomplishment required a huge team effort to make it happen.

"We are taking a risk-balanced approach in ramping HAPLS to its full performance. The data we collected confirmed our performance models and gave the green light to start integration with the short-pulse beamline before ramping to even higher power levels."

Representatives from the European Union’s Extreme Light Infrastructure Beamlines facility in the Czech Republic, where HAPLS will be installed, attended the demonstration. “We are delighted to see the HAPLS pump laser work with a performance exceeding the project expectations for this phase, and achieve this important milestone on budget and ahead of schedule,” said ELI Beamlines Chief Laser Scientist Bedrich Rus. “The partnership with LLNL has been a tremendously successful story, and this demonstration shows the robustness of the underlying design and technology. The L3 (HAPLS) beamline will be an ELI Beamlines’ user facility workhorse.”

ELI Beamlines applications

HAPLS is designed to reach a peak power exceeding one petawatt at a repetition rate of 10 times per second to deliver intensities on target up to 10²³ Wcm^-2. Achieving this intensity is expected to open up entirely new areas of laser-matter investigation, new applications of laser-driven X rays and particles, and allow researchers to study laser interactions with the sea of virtual particles that comprise a vacuum.

Ramping of the laser to its full performance was organized in several phases. The first phase, completed last October, brought the pump laser to an intermediate performance level in a single shot regime. “In the second phase,” Haefner said, “we brought it up to average power, and that was an intermediate performance level. Now we’re integrating the pump laser and the short-pulse system. Together with ELI Beamlines we will integrate the short-pulse performance diagnostics, and then we will ramp the short-pulse laser system first to energy and then to average power.”

Systems Architect and Commissioning Manager Andy Bayramian explained the reason for the phased approach: “We operate the laser at the intermediate performance level, learn how to operate it, identify operational challenges and input-data errors if they exist, and once we have gained operational experience, then we ramp it to its full performance.”

Haefner added, “HAPLS will allow its users for the first time to approach the commercial applications arena for laser-generated secondary sources. There’s no other laser which could actually produce sufficient average power of the high-intensity light required for commercial applications.”

Ultimately the system’s pulses will be used to generate extremely bright and short X-ray pulses for imaging cells and proteins at unprecedented spatial and temporal resolution. Another application is generating bunches of protons or ions for medical therapy and materials science research. Scientists also will study the interaction of intense laser light with matter to improve understanding of high energy density science.

About the Author

Matthew Peach is a contributing editor to optics.org.