Ten stories in 2017 you may have missed, plus a bonus
Throughout 2017 researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have produced new insights into the science of fusion energy that powers the sun and stars and the physics of plasma, the hot, charged state of matter that consists of electrons and atomic nuclei, or ions, and makes up 99 percent of the visible universe. The research advances the development of fusion as a safe, clean and plentiful source of power, produced in doughnut-shaped facilities called tokamaks, and explores the diverse aspects and applications of plasma. The findings range from a breakthrough for stabilizing fusion plasmas to good news for the international ITER project going up in France to new thoughts about the chances of life on planets circling nearby stars. Here, in no particular order, are 10 not-to-be-missed PPPL stories — plus a bonus story — that appeared in 2017.
1. Improving fusion power plants. Future facilities that produce fusion energy must operate in a steady state, or constant, manner 24 hours a day. At PPPL, physicist Masayuki Ono, in collaboration with research centers in the United States and Japan, has proposed an innovative solution to the steady state problem. His design calls for loops of liquid lithium to clean and recycle tritium, a key fusion fuel ingredient, while protecting tokamak components that exhaust waste heat, and cleaning dust and other impurities from the tokamak — all at the same time.
2. Bringing solar eruptions down to Earth. Using lasers, researchers led by PPPL physicist Will Fox have created conditions on Earth that mimic astrophysical behavior. The lasers generate plasmas that shed light on cosmic bursts of subatomic particles that give rise to solar eruptions and solar flares and accelerate cosmic rays to near the speed of light. Subsequent computer simulations have agreed well with the breakthrough laboratory experiments.
3. Good news for ITER. New findings led by C.S. Chang of PPPL show that ITER, the international fusion experiment under construction in France, should be able to withstand the enormous heat load that will strike the divertor plates that exhaust waste heat from the facility. Results of the two-year collaboration with seven U.S. and European institutions found that the load, which will be comparable to the heat that spacecraft experience when re-entering the Earth’s atmosphere, will be wide enough for the divertor to tolerate. Previous estimates drawn from existing tokamaks had suggested that the heat could be so narrow and concentrated as to the damage the divertor.
4. The blob that ate the tokamak. Like bubbles that rise in boiling water, blobs that percolate in the plasma inside fusion devices known as tokamaks can cause heat to escape from the devices. PPPL scientists led by Michael Churchill performed computer simulations that have produced a fuller and more fundamental picture of the behavior of blobs, providing new insight into how to control them.
5. Shock waves of the new. Supersonic shock waves propel astrophysical processes such as supernova particles to velocities that approach the speed of light. Scientists led by Derek Schaeffer of PPPL and Princeton have for the first time reproduced such shocks in a laboratory setting, enabling study of the puzzling processes with greater flexibility and control than can be done in space.
6. Growing microscopic particles that are stronger than steel. Research at the PPPL Laboratory for Plasma Nanosynthesis develops new insight into the use of plasma to synthesize nanomaterials — particles such as carbon nanotubes that are measured in billionths of a meter, are found in everything from swimwear to electrodes and have a tensile strength, or resistance to breaking when stretched, that is stronger than steel. PPPL collaborations with physicists at Princeton University and the State University of New York at Stony Brook have now uncovered a method for speeding the growth of nanoparticles — a step toward understanding, predicting and controlling the synthesis of plasma to produce the prized material.
7. Stabilizing next-generation fusion plasmas. In a potentially major advance, physicists at PPPL and the DIII-D National Fusion Facility that General Atomics operates for the DOE have discovered a way to reduce the loss of heat and particles from fusion plasmas. A combination of PPPL modeling led by physicist Gerrit Kramer and DIII-D experiments has found that broadening the electric current in the center of plasma could reduce the loss of crucial elements called alpha particles that heat the plasma and sustain fusion reactions.
8. A quick and easy way to shut down plasma instabilities. A wave-like disturbance that commonly occurs in fusion plasmas can halt fusion reactions and damage the walls of tokamaks that house the fusion process. PPPL physicist Eric Fredrickson recently found that such disturbances can be suppressed on the National Spherical Torus Experiment-Upgrade at the Laboratory with particles from a second neutral beam injector installed in the upgrade — a remarkably simple solution. The results validated predictions of a computer code developed by PPPL physicist Elena Belova and marked good news for the future of fusion.
9. The impact of recycling on plasma turbulence. Researchers have long wondered how atoms recycled from the walls of tokamaks that house fusion reactions affect turbulence, the random fluctuation of plasma that can cause heat and particle loss. In the first basic-physics attempt to study the impact, PPPL physicist Daren Stotler, working under PPPL’s C.S. Chang, used an extreme-scale computer code to model how the recycled neutral atoms tend to increase turbulence in detail that had never before been possible. Further research could improve understanding of the likely performance of plasma in the huge ITER tokamak, where recycling may differ from what is observed in current tokamaks.
10. Self-extinguishing troublesome bursts in fusion plasmas. Instabilities called Edge Localized Modes (ELMs) frequently arise in highly confined fusion plasma and could damage tokamak components and halt fusion reactions. PPPL physicist Fatima Ebrahimi has for the first time used advanced models to simulate the cyclic behavior of these instabilities, creating insight into how to curtail or prevent them in future tokamaks. The simulations agree with observations of the cyclic behavior of ELMs in tokamaks around the world.
And now, a bonus story you should not miss from 2017:
11. Life on exoplanets. Astrophysicst Chuanfei Dong of PPPL and Princeton University has led collaborative research that casts doubt about the chances of life on planets that orbit stars beyond the solar system. The space physicists noted that the stellar wind that blows from stars could deplete the atmosphere of such planets over hundreds of millions of years, eliminating liquid water that is vital for life as we know it.
PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.
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