Two research institutes are joining forces around laser design and simulation. They are doing this to successfully take laser ignited inertial fusion from the experimental phase to industrial application and make it suitable for a power plant, for example. In the project ICONIC-FL (International Cooperation on Next-gen Inertial Confinement Fusion Lasers), the US Lawrence Livermore National Laboratory (LLNL) and the Fraunhofer-Institut für Lasertechnik ILT in Germany, are working closely together to combine their advanced laser simulation models.
The aim of the collaboration is to develop high-energy lasers that can ignite a fusion reaction and be operated 24/7 with maximum efficiency in a power plant. This requires precise and highly accurate predictions of laser performance. Therefore, powerful computer simulations play a central role in the development of laser architectures.
From experiment to power plant
At the National Ignition Facility (NIF), engineers focused on solving plasma physics issues. Consider issues about the conditions needed to heat the fusion fuel deuterium-tritium to more than 100 million degrees, extremely compress it and trigger a self-sustaining fusion reaction. When this happens, more energy is released than is introduced externally by lasers into the fuel capsule - the target.
Efficient diode-pumped solid-state lasers
Since the breakthrough in late 2022, LLNL has demonstrated several times that the physical principle works, with ever-increasing energy yields. However, a single firing is not enough for a future power plant. The power plant will need about 15 shots per second (!). This will require efficient diode-pumped solid-state lasers (DPSSL) that can fire dozens of times per second.
Laser heavyweights
Two laser heavyweights, LLNL and Fraunhofer ILT, are now combining their complementary expertise to develop these lasers: while LLNL brings decades of experience in high-energy laser technology, the Aachen-based institute is a global leader in the development and industrial scale-up of DPSSLs.
Virtual stress test for tomorrow's hardware
The laser design needs to be validated in simulations before expensive prototypes can be built. In the ICONIC-FL (International Cooperation on Next-gen Inertial Confinement Fusion Lasers) project, the partners are pursuing the common goal of simulating the amplification phases of high-energy lasers in as much detail as possible to lay the groundwork for a later design. They focus on the heart of the system: the laser amplifiers.
Laser amplifiers
Laser amplifiers amplify an initially small laser pulse to the laser energies required for fusion. In these laser pulses, the photons transmit an energy of many millions of joules. The laser media used for this purpose consist of stacks of laser glass or crystal plates with an area of up to 40 cm x 40 cm and a thickness of several millimetres; they are cooled with transparent cooling media during operation. The amplifier plates are exposed to enormous thermal and optical loads.
Small effects, big impact
"24/7 operation leads to heating, refraction effects and aberrations that can distort the laser beam. Even the smallest, unpredictable effects here are significant and lead to efficiency loss or direct damage to the optics. We want to understand exactly what happens in each individual plate so that we can then accurately simulate complex plate stacks," explains Johannes Weitenberg, project manager at Fraunhofer ILT.
In this transatlantic collaboration, we will efficiently consolidate the technological basis for the fusion power plantTammy Ma, head of fusion research at LLNL
Independent cross-validation: safety through two models
In the research project, the partners will carefully merge their respective simulation solutions, which they have developed over many years, to obtain increasingly detailed and realistic simulations. They will systematically compare and cross-validate the simulations without exchanging the actual code. "The point is not to merge the simulation models, but to learn from each other and double-check our results," Weitenberg clarifies.
Robust and reliable
This methodical approach is extremely valuable from a scientific, technical and economic point of view: the partners can guarantee that their simulated predictions are extremely robust and reliable by applying their respective codes - developed to maturity in different application areas - independently to the same design. This approach can significantly speed up the development of lasers for a real power plant and avoid costly missteps in a multi-billion-dollar process.
Lowering financial risks
The collaboration combines the advanced expertise of both institutes, which they have systematically built up and deepened since the 1990s, to significantly reduce development time. By validating the designs in simulation, the partners avoid not only technical, but also huge financial risks: with up to 400 beam paths in future power plant designs, even the smallest overlooked detail can incur significant costs when transitioning to series production.
Strategic partnership for clean energy
"The transition from basic research to power plant development requires the rapid development of new, robust laser systems. Fraunhofer ILT's expertise in industrial scale-up of diode-pumped lasers is crucial for accelerating our IFE programme. In this transatlantic collaboration, we will efficiently consolidate the technological base for the fusion power plant," explained Tammy Ma, head of fusion research at LLNL.
Basis for power plant of the future
Prof Constantin Häfner, executive vice president for research and transfer at the Fraunhofer-Gesellschaft, stresses, "We are in the decisive decade for fusion energy. To exploit the full potential of inertial fusion, we need to develop new laser architectures with uncompromising perfection. Combining LLNL's expertise with the industrial scalability expertise of Fraunhofer and its institute ILT is a powerful answer to this challenge. Here we lay the foundations the energy cenetral of the future."
Climate-neutral electricity
Fusion power plants could generate competitive, climate-neutral electricity 24/7, making them an important addition to volatile renewable energy sources. With ICONIC-FL, Germany and the US are jointly laying the mathematical foundation for this future technology.
Opening photo: During the construction of the National Ignition Facility (NIF), a production line was set up on site specifically for the production of laser glass plates. (Photo: Lawrence Livermore National Laboratory)
Source: Fraunhofer ILT
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