Continuous scientific advancements make commercial energy production from laser-driven fusion viable. Thereby, the clean, safe and reliable technology provides a way forward in the pursuit of reducing fossil fuel dependency and CO2-neutrality.
🧭 Technology Overview
When hearing laser, people tend to think of laser pointers. The small devices are able to emit light in a targeted way. More recent laser technology is able to do much more than shoot a red dot at a company’s whiteboard. In 2018, the Nobel Prize in Physics was awarded to two researchers, Donna Strickland and Gérard Mourou, for their work on “Chirped Pulse Amplification”. The related research paved the way for peak laser output of over 10 petawatt which set a new milestone for research and industry applications. Furthermore, an overall improvement of diode technology enables quick-pulsed laser with a repetition rate of up to 10Hz. The developments prove the quick-pulsed lasers’ technical as well as commercial viability. Consequently, ultrashort pulse lasers drive progress in various high-tech fields, such as X-ray technology, material science and different medical areas.
So how is that connected to combating climate change? In the last few years, scientific developments in laser and nano technology have made laser-induced inertial confinement fusion possible. The technology is centered around a fusion process in which fuel pellets are hit with high intensity ultrashort pulsed lasers. What’s fascinating from an environmental standpoint, is that the technology provides energy which is carbon-free, safe, abundant, high-density and reliable.
👨🏻🔬 Technology Deep Dive
1) Laser Pulse Creation
The ultrashort laser pulses which are in the end shot on a fusion target cannot be produced directly. Rather, they have to be formed in a chain of events. Accordingly, a range of photons is created and formed into short pulses. These pulses have a duration of under a tenth of a trillionth of a second and are low in energy.
In order to reach higher intensity required to initiate the fusion process, the short photon pulses are prepared for amplification. Generally, the laser photons have a broad spectrum of wavelengths (from a few hundred nanometers to more than ten thousand nanometers for some types of lasers). In the amplification preparation, the laser pulses are lengthened with a pulse stretcher by a factor of 10,000.
At around 10Hz, pulses then pass through the amplifier units which increase the pulses’ energy. This is done by passing the photon pulses through crystals and glasses which are pumped with light pulses.
After getting amplified to a higher energy level, the pulses are compressed back to ultrashort pulses. Specifically, the recompressed laser beams have a duration that is nearly as short as the starting duration. By doing so, the photon pulses are now high energy and ultrashort at the same time.
5) Fuel Pellets & Fusion
Speaking of the fusion targets, the millimeter-sized pellets are produced separately and injected into the reaction. A separate injector unit replicates the frequency of the laser pulses. Typically, these pellets contain around 10 mg of fuel which consists of a mixture of two hydrogen isotopes, deuterium and tritium. In the case of Marvel Fusion, the pellets additionally contain the boron-11 isotope.
The fusion reaction itself can be schematically described in a four-step process. Firstly, the focused high intensity ultrashort laser pulses heat the surface of the fusion target and form a surrounding plasma envelope. Secondly, the fuel gets compressed through the inwards-facing blowoff of the hot surface material. Thirdly, the fuel core reaches an ultrahigh density and ignites at around 100,000,000 Celsius. The resulting thermonuclear burn yields many times the input energy. For decades, the state of “burning plasma”, a self-sustained fusion burn that is ignited from the heat of previous fusions, could not have been reached. However, this step is key as a fusion burn that is sustained by the reaction itself leads to the desired energy output which is higher than the initial input.
The released energy comes in the form of high energy ions which are expelled from the fusion. It then gets converted into electricity by a process depending on the respective fuel (e.g., Carnot cycle).
🔮 Future Applications
In general, fusion technology proposes solutions for many of nuclear fission’s pitfalls. The fuel is much safer, depending on the specific fuel pellet, it is not radioactive. Using boron instead of tritium isotopes makes the fuel available for natural and stable resources. The safety aspect is another one in favor of fusion technology. For inertial confinement fusions, there is no risk of dangerous chain reactions like for nuclear technology and the power plant can be shut down be turning off the laser pulse. Last but not least, byproducts of the energy production process can be handled without the necessity of decade-long storage due to radioactive radiation.
Consequently, the technology is seen as a potential candidate to tackle the energy demand and at the same time suffice environmental goals. Therefore, when commercially viable, the technology will most likely replace traditional fossil fuel powered energy plants. Importantly, renewable sources, such as solar, wind and hydroelectric power, can only meet a fraction of demand. With growing demand and increasingly ambitious environmental goals, new technologies have to replace the traditional ones and fill the gap that renewable sources cannot close.
✋🏻 What’s holding the technology back?
Despite recent advancements and academic attention, the technology has not made its way to commercial usability yet. In the case of the German start-up Marvel Fusion, the hope lies in the high-class academic profiles that CEO Moritz von der Linden has assembled around him. Moreover, institutes and companies in other countries aim for commercial viability until 2030 and report significant progress on the way to energy surpluses that justify the use of the technology. A recent Science article highlights the potential of the U.S. American National Ignition Facility (NIF) to increase peak laser energy and thereby reach burning plasma. As Congress has approved a $339.3 million funding for the program for FY2021, researchers might be able to reach new milestones this year. Evidently, the technology might pave the way to replace fossil fuel energy production and reach future carbon-neutrality goals in a clean, safe and reliable fashion.
📫 Closing Remarks
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