hydrogen isotopes

A Fusion Reaction Generated Twice the Energy It Used for the First Time Ever. Game On.

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We’re one step further down the path to limitless clean power.

nuclear fusion power generator concept image, 3d rendering

  • On December 5, 2022, the National Ignition Facility in the U.S. achieved ignition by creating more energy via nuclear fusion than they originally put in.
  • Now, a series of details focuses on how that achievement came to be, and also highlights three subsequent ignition reactions—one of which produced almost double the amount of energy it used.
  • Investments in renewable energy could be vital to combating the climate crisis in the present day.

Although still a far-future technology, nuclear fusion is really hot right now, both literally and figuratively. Squishing together two light nuclei requires immensely hot temperatures (like, 100 million°C hot), and the fusion industry is similarly sizzling. More than 40 fusion companies now exist around the world—25 of which are in the U.S. alone.

One of the big drivers behind the immense excitement surrounding this futuristic energy-making venture is the fact that Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) achieved “ignition” in December of 2022. This means that for the first time ever, scientists were able to create a fusion reaction that produced more energy than was used to create the reaction in the first place.

Yesterday, LLNL published a series of papers that go into detail about how exactly this major achievement took place and also talk about three other ignition moments that occurred throughout 2023—one of which produced almost twice as much energy as was initially put in.

“A fundamental obstacle to realizing a fusion energy source,” the researchers said in a press release, “has been the ability to control and heat a plasma (a mixture of ions and free electrons) to the conditions required for ignition and to confine the plasma at these conditions over long enough time scales such that more fusion energy is produced than was supplied to initiate the reaction.”

To put it very simply, nuclear fusion is like nuclear fission but in reverse. A fission reactor—the only kind of nuclear reactor used as an energy source today—splits Uranium-235 into two smaller atoms, specifically, barium and krypton. This releases energy that then creates steam and powers turbines. Fusion, on the other hand, happens on the other end of the nuclear binding energy curve. It uses two light nuclei, usually hydrogen isotopes deuterium and tritium, that then overcome the strong nuclear force and a subatomic quirk known as “quantum tunneling.” The resulting fusion creates a helium atom and most importantly energy thanks to that whole “e=mc2” thing.

Although there are many ways to achieve fusion (the Sun is pretty good at it, thanks to its immense gravity), the NIF uses a process known as inertial confinement. In using this method, 192 lasers converge on a hohlraum capsule that creates an X-ray bath. This squeezes the isotopes inside, which collapse at roughly 250 miles per hour, fuse, and release energy. Because the fusion reaction occurs before the fuel disassembles, the plasma is contained by its own inertia (hence the name).

On December 5, 2022, NIF produced 3.15 megajoules (MJ) despite only putting in 2.05 MJ (although this doesn’t account for the energy needed to run the entire facility, which is roughly 100 times greater than the energy that eventually reaches the capsule). Ignition—achieved.

In early August, the NIF announced that their second ignition successfully achieved higher yields than their historic first. While details were scant at the time, the paper reveals that 2.05 MJ of laser energy created 3.88 MJ, which is even higher than the two subsequent ignitions in 2023. However, these efficiencies are happening at a facility that wasn’t exactly designed to maximize output in the first place. Instead, achieving ignition in order to keep the U.S.’s nuclear deterrence safe and reliable is its primary goal.

“The NIF laser architecture and target configuration was chosen to give the highest probability for fusion ignition for research purposes and was not optimized to produce net energy for fusion energy applications,” the NIF said. “Inertial fusion energy applications requiring advancements to the underlying scheme require further development, such as laser energy usage, shot rate, target robustness, higher fuel compression levels, and cost.”

The fusion era is finally upon us. Laboratories regularly achieve ignition, international projects gear up for “first plasma” on groundbreaking experiments, and companies continue to invest in the energy source of the future—but not the energy source of the present.

While fusion energy is certainly exciting, it’s arriving too late to solve the current climate crisis. Research into this emerging field continues to grow, and as it does, so too must investments in the renewable energy technologies of today if we ever want to see a world powered by the physics of our own Sun.

Nuclear spins control electrical currents.

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Photograph of University of Utah physicist Christoph Boehme

Spin doctor: Christoph Boehme inserts an OLED into a spectrometer

An international team of physicists has shown that information stored in the nuclear spins of hydrogen isotopes in an organic LED (OLED) can be read out by measuring the electrical current through the device. Unlike previous schemes that only work at ultracold temperatures, this is the first to operate at room temperature, and therefore could be used to create extremely dense and highly energy-efficient memory devices.

With the growing demand for ever smaller, more powerful electronic devices, physicists are trying to develop more efficient semiconductors and higher-density data-storage devices. Motivated by the fact that traditional silicon semiconductors are susceptible to significant energy losses via waste heat, scientists are investigating the use of organic semiconductors. These are organic thin films placed between two conductors and they promise to be more energy efficient than silicon semiconductors. Furthermore, the availability of many different types of organic thin film could help physicists to optimize the efficiency of these devices.

Chip and spin

Conventional memory chips store data in the form of electrical charge. Moving this charge around the chip generates a lot of waste heat that must be dissipated, which makes it difficult to miniaturize components and also reduces battery life. An alternative approach is to store information in the spins of electrons or atomic nuclei – with spin-up corresponding to “1” and spin-down to “0”, for example. This could result in memories that are much denser and more energy efficient than the devices used today.

Atomic nuclei are particularly attractive for storing data because their spins tend to be well shielded from the surrounding environment. This means that they could achieve storage times of several minutes, which is billions of times longer than is possible with electrons. The challenge, however, is how to read and write data to these tiny elements.

Now, Christoph Boehme and colleagues at the University of Utah, along with John Lupton of the University of Regensburg and researchers at the University of Queensland, have shown that the flow of electrical current in an OLED can be modulated by controlling the spins of hydrogen isotopes in the device. “Electrical current in an organic semiconductor device is strongly influenced by the nuclear spins of hydrogen, which is abundant in organic materials,” explains Lupton. The team has shown that the current flowing through a plastic polymer OLED can be tuned precisely, suggesting that inexpensive OLEDs can be used as efficient semiconductors.

Just like MRI

Boehme and his team applied a small magnetic field to their test OLED, which creates an energy difference between the orientations of the nuclear spins of protons and deuterium (both hydrogen isotopes). The researchers then used radio-frequency signals to alter the directions of the spins of the protons and deuterium nuclei – a process that is also done during a nuclear magnetic resonance (NMR) experiment.

The changes to the nuclear spins affect the spins of nearby electrons, and this results in changes to the electrical current. The magnetic forces between the nuclear and electron spins are millions of times smaller than the electrical forces needed to cause a similar change in current. This suggests that the effect could be used to create energy-efficient semiconductor memories.

This recent work follows on from research done in 2010, when Boehme and colleagues showed that the technique could be used to control current in a device made from phosphorus-doped silicon. However, this was only possible in the presence of strong magnetic fields and at temperatures within a few degrees of absolute zero. Such conditions are impractical for commercial devices, but the OLED-based device needs neither ultracold temperatures nor high magnetic fields.

Time to relax

“In organic semiconductors, the spin-relaxation time does not change significantly with temperature,” explains Lupton. “In contrast, the spin-relaxation time in phosphorus-doped silicon increases significantly when the temperature is lowered; so in phosphorus-doped silicon, the experiments had to be carried out at low temperatures and high magnetic fields.”

The team believes that its technique should also work with other nuclei with non-zero spin, with some limitations. “Since protons and deuterium are both hydrogen isotopes, they can be interchanged in the synthesis without changing the chemical structure of the polymer, which may not be possible with other types of nuclei,” Lupton explains. “Tritium, the third hydrogen isotope, is radioactive, so would not be much good in experiments.”