HAPLS Completes Phase 1 Energy-Ramping Campaign

LLNL’s High Repetition Rate Advanced Petawatt Laser System (HAPLS) project reached a key energy milestone on Oct. 21, when the HAPLS pump laser system produced 71 joules of infrared laser energy and 41 joules of second-harmonic (green) energy.

The pump laser is a main component of the HAPLS system, and energizes the final power amplifier of the short-pulse beamline. When fully commissioned, HAPLS will be the world’s highest average power petawatt laser system. HAPLS is being designed, developed, assembled and tested at LLNL for delivery to the European Union’s Extreme Light Infrastructure Beamlines (ELI-Beamlines) facility in the Czech Republic.

Ramping of the HAPLS laser, and in this case the pump laser, is organized in several phases which are set forth in the agreement with ELI-Beamlines and is based on a conservative and stepwise approach to commissioning HAPLS to its full design performance. Achieving 71 joules of infrared energy and 41 joules at the second harmonic marks the completion of the first energy-ramping campaign, which exceeded the required energies by 11 joules in the infrared and six joules in the second harmonic.

The energy ramping was conducted with shots every five seconds in a “single shot” regime, as opposed to an average power regime in which the amplifiers are thermally loaded and thermal effects need to be mitigated. HAPLS uses helium-gas cooling to extract the heat from the amplifier gain material.

The HAPLS team’s next ramping milestone is to repeat the same amount of energy extraction at a repetition rate of 3Hz (three shots per second) in keeping with the project’s phase 1 ramping guidelines. Gas cooling and heat extraction already has been demonstrated on the HAPLS pump laser amplifiers. Completion of those milestones will prepare the facility to integrate the pump laser with the short-pulse beamline.

In the second ramping phase, the short-pulse beamline will be ramped following a similar approach as for the pump laser. Once that is complete, the laser will be transported to the ELI Beamlines facility and integrated with the ELI pulse compressor before ramping to full design performance is begun.

“This is great progress and marks an important part in the commissioning of HAPLS,” said Constantin Haefner, program director for Advanced Photon Technologies. “HAPLS is being realized through the extensive subject matter expertise in the NIF & Photon Science and Engineering directorates and close collaboration with ELI Beamlines.”

The ELI Beamlines facility was officially inaugurated in ceremonies on Oct. 19, marking the conclusion of the project’s initial implementation phase. LLNL Deputy Director for Science and Technology Patricia Falcone, who attended the ceremonies along with Haefner, said, “We are excited to be working with our colleagues on realizing new capabilities for lasers, and looking forward to great scientific results from this wonderful facility.”

The facility’s laser hall is being prepared for installation of new laser and experimental technologies beginning next year. The entire complex will be available for user research starting in 2018.

“ELI as a whole will be the world’s first international laser facility,” said Wolfgang Sandner, Director General of the ELI-DC International Association, “hosting today’s most sophisticated and most powerful lasers. It will attract the best scientists from all over the world to perform experiments at the frontier of science. Our vision is to make it the ‘CERN of laser research.’”

Bedřich Rus, chief scientist of ELI laser technology, noted that several world records already have been broken during the development of the project’s laser systems, including the world’s highest peak power laser diode arrays developed for HAPLS.

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