Nav: Home

As hot as the sun's interior

June 05, 2019

The three classic physical states - solid, liquid and gaseous - can be observed in any normal kitchen, for example when you bring an ice cube to the boil. But if you heat material even further, so that the atoms of a substance collide and the electrons separate from them, then another state is reached: plasma. More than 99 per cent of material in space is present in this form, inside stars for instance. It is therefore no wonder that physicists are keen to study such material. Unfortunately, creating and studying plasmas on Earth using the high temperature and pressure that exist inside stars is extremely challenging for various reasons. Physicists at Friedrich Schiller University in Jena have now managed to solve some of these problems, and they have reported on their results in the renowned research journal Physical Review X.

Nanowires let light through

"To heat material in such a way that plasma is formed, we need correspondingly high energy. We generally use light in the form of a large laser to do this," explains Christian Spielmann of the University of Jena. "However, this light has to be very short-pulsed, so that the material does not immediately expand when it has reached the appropriate temperature, but holds together as dense plasma for a brief period." There is a problem with this experimental setup, though: "When the laser beam hits the sample, plasma is created. However, it almost immediately starts to act like a mirror and reflects a large part of the incoming energy, which therefore fails to penetrate the matter fully. The longer the wavelength of the laser pulse, the more critical the problem," says Zhanna Samsonova, who played a leading role in the project.

To avoid this mirror effect, the researchers in Jena used samples made of silicon wires. The diameter of such wires - a few hundred nanometres - is smaller than the wavelength of around four micrometres of the incoming light. "We were the first to use a laser with such a long wavelength for the creation of plasma," says Spielmann. "The light penetrates between the wires in the sample and heats them from all sides, so that for a few picoseconds, a significantly larger volume of plasma is created than if the laser is reflected. Around 70 per cent of the energy manages to penetrate the sample." Furthermore, thanks to the short laser pulses, the heated material exists slightly longer before it expands. Finally, using X-ray spectroscopy, researchers can retrieve valuable information about the state of the material.

Maximum values for temperature and density

"With our method, it is possible to achieve new maximum values for temperature and density in a laboratory," says Spielmann. With a temperature of around 10 million Kelvin, the plasma is far hotter than material on the surface of the Sun, for example. Spielmann also mentions the cooperation partners in the project. For the laser experiments, the Jena scientists used a facility at the Vienna University of Technology; the samples come from the National Metrology Institute of Germany in Braunschweig; and computer simulations for confirming the findings come from colleagues in Darmstadt and Düsseldorf.

The Jena team's results are a ground-breaking success, offering a completely new approach to plasma research. Theories on the state of plasma can be verified through experiments and subsequent computer simulations. This will enable researchers to understand cosmological processes better. In addition, the scientists are carrying out valuable preparatory work for the installation of large-scale apparatus. For example, the international particle accelerator, 'Facility for Antiproton and Ion Research' (FAIR), is currently being set up in Darmstadt and should become operational around 2025. Thanks to the new information, it will be possible to select specific areas that merit closer examination look.
Original publication: Zhanna Samsonova, et al.: Relativistic Interaction of Long-Wavelength Ultrashort Laser Pulses with Nanowires, Physical Review X, 2019, DOI: 10.1103/PhysRevX.9.021029

Dr Zhanna Samsonova / Prof. Christian Spielmann
Institute of Optics and Quantum Electronics of Friedrich Schiller University, Jena
Max-Wien-Platz 1, 07743 Jena, Germany
Tel.: +49 (0)3641/947214, +49 (0)3641/947231

Friedrich-Schiller-Universitaet Jena

Related Plasma Articles:

Table top plasma gets wind of solar turbulence
Scientists from India and Portugal recreate solar turbulence on a table top using a high intensity ultrashort laser pulse to excite a hot, dense plasma and followed the evolution of the giant magnetic field generated by the plasma dynamics.
Getting the biggest bang out of plasma jets
Capillary discharge plasma jets are created by a large current that passes through a low-density gas in what is called a capillary chamber.
Neptune: Neutralizer-free plasma propulsion
Plasma propulsion concepts are gridded-ion thrusters that accelerate and emit more positively charged particles than negatively charged ones.
UCLA researchers discover a new cause of high plasma triglycerides
People with hypertriglyceridemia often are told to change their diet and lose weight.
Where does laser energy go after being fired into plasma?
An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde.
More Plasma News and Plasma Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Teaching For Better Humans
More than test scores or good grades — what do kids need to prepare them for the future? This hour, guest host Manoush Zomorodi and TED speakers explore how to help children grow into better humans, in and out of the classroom. Guests include educators Olympia Della Flora and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...