A recent research emphasizes the necessity for the United States to intensify its laser R&D endeavors to be able to better compete with the significant overseas efforts in constructing large, high-power laser systems. The research marks the advancement and milestones achieved by the Department of Energy’s Berkeley Lab Laser Accelerator (BELLA) Center and other sites.
As noted by the December report from the National Academies of Sciences, Engineering, and Medicine, which extends the independent analysis to policymakers and government agencies, investments in this supposed “second laser revolution” promise to pave the way for a range of applications, such as particle acceleration, medicine, and machining.
Improved collaboration and coordination by government agencies and labs, industry, and universities are recommended in the 280-page report, “Opportunities in Intense Ultrafast Lasers: Reaching for the Brightest Light,” for enhancing U.S. laser facilities and capabilities.
Furthermore, it advocates the DOE to guide the conception of a national approach for a laser tech-transfer program connecting national labs, academia, and industry; midscale projects that could be prospectively hosted at universities, and the development and operation of large-scale national laboratory-based laser projects.
The committee that came up with the report surveyed Berkeley Lab and other Northern California national labs, including SLAC National Accelerator Laboratory and Lawrence Livermore National Laboratory. In addition, the committees also surveyed the Extreme Light Infrastructure Beamlines laser facility site that is under progress in the Czech Republic and the Laboratory for Laser Energetics of the University of Rochester in New York.
At the Lawrence Berkeley National Laboratory (Berkeley Lab) of DOE, BELLA scientists have undertaken efforts to devise laser-based acceleration methods that could result in more compact particle accelerators for high-energy physics and drivers for high-energy light sources. Moreover, according to the report, “laser expertise and utilization” that had been the focus of other laboratories “is now broadening with plans for utilization of lasers at (Berkeley Lab)” and other places.
BELLA has been able to show advancement in demonstrating the high-speed acceleration of electrons with the help of separate stages of laser-based acceleration by forming and heating plasmas in which a powerful wave is generated on which electrons “surf.”
According to Wim Leemans, Director of the BELLA Center and the Lab’s Accelerator Technology and Applied Physics Division, “There’s a lot of work that’s been done already, and Berkeley Lab has been a key developer for the vision of where things need to go.”
In 2004, a ground-breaking experiment was conducted in Berkeley Lab, demonstrating the ability of laser plasma acceleration to generate relatively narrow energy spread beams—featured in the issue named “Dream Beam” in the journal Nature. In 2006, a similar laser-driven acceleration technique was used for the acceleration of electrons to a record (at that time) energy of one billion electron volts, or GeV. Following that accomplishment, in 2014, a 4.2 GeV beam was achieved with the help of the robust new laser that is at the center of the BELLA Center and will be important to its campaign in progress for achieving 10 GeV. In 1996, Berkeley Lab also recorded the earliest demonstration of X-ray pulses lasting merely quadrillionths of a second using an approach called “inverse Compton scattering,” the report reads.
K-BELLA: Combining Speed and Power
“What industry is seeing is the push toward higher-average-power lasers and ultrafast lasers, and it’s starting to impact machining and industrial applications,” Leemans added. “That’s really good news for us.” In laser terminology, average power concerns the total power generated by the laser puts over time, counting the pulses and the “off time” between pulses, while the peak power corresponds to an individual pulse.
A rapid-fire rate of high-power pulses provides a laser higher average power and may find potential applications in an extensive range of areas. The National Academies report advocates that it is essential for U.S. scientific stakeholders to work to characterize the technical specifications in laser performance objectives, including the wavelength of laser light, pulse length, repetition rate, and the targets for peak power.
In 2012, the laser at BELLA Center delivered a petawatt (quadrillion watts) of power squeezed into pulses measuring 40 quadrillionths of a second in length and came at a rate of one per second—thereby setting a record.
A new objective is to increase this pulse rate to one kilohertz, or 1000 per second, for a next-generation upgrade named k-BELLA. If it is possible to generate pulse rates of up to 10,000 or 100,000 per second, this machine could be applicable for an innovative type of laser-based particle accelerator.
“There are lots of applications for a k-BELLA-style laser,” stated Leemans. The idea is for k-BELLA to be a collaborative research facility that would involve researchers from outside the Lab, he stated, which is also consistent with the proposal in the report to promote a more accommodating environment for laser science and scientists. The report also notes that forging and maintaining a partnership with other top-notch laser centers is crucial for the U.S. laser program.
According to Leemans, the inclusion of a second beamline at BELLA is another upgrade that may prove to be valuable to the U.S. laser program. The second beamline could enable exotic collisions between two beams of light, or between an electron beam and a beam of light.
Moreover, laser-produced low-energy electron beams and laser-produced beams of light elements could be pursued at BELLA to develop the biomedical principle for innovative types of medical treatments with the ability to better target cancers, for instance.
We look forward to enhancing our own laser capabilities at Berkeley Lab while working with our partners to strengthen the nation’s laser R&D efforts. Higher average power lasers will be essential for all practical applications of laser plasma accelerators.
James Symons, Associate Laboratory Director for Physical Sciences
The U.S. Department of Energy’s Office of Science, the National Nuclear Security Administration, the Office of Naval Research, and the Air Force Office of Scientific Research sponsored the National Academies report.