New measurement method promises spectacular insights into the interior
of planets

Date:
October 5, 2021
Source:
Helmholtz-Zentrum Dresden-Rossendorf
Summary:
At the heart of planets, extreme states are to be found:
temperatures of thousands of degrees, pressures a million times
greater than atmospheric pressure. They can therefore only be
explored directly to a limited extent -- which is why the expert
community is trying to use sophisticated experiments to recreate
equivalent extreme conditions.

Researchers have adapted an established measurement method to these
extreme conditions and tested it successfully: Using the light
flashes of the world's strongest X-ray laser the team managed to
take a closer look at the important element, carbon, along with
its chemical properties.



FULL STORY ==========================================================================
At the heart of planets, extreme states are to be found: temperatures of thousands of degrees, pressures a million times greater than atmospheric pressure. They can therefore only be explored directly to a limited extent
- - which is why the expert community is trying to use sophisticated experiments to recreate equivalent extreme conditions. An international research team including the Helmholtz-Zentrum Dresden-Rossendorf
(HZDR) has adapted an established measurement method to these extreme conditions and tested it successfully: Using the light flashes of the
world's strongest X-ray laser the team managed to take a closer look at
the important element, carbon, along with its chemical properties. As
reported in the journal Physics of Plasmas the method now has the
potential to deliver new insights into the interior of planets both
within and outside of our solar system.


==========================================================================
The heat is unimaginable, the pressure huge: The conditions in the
interior of Jupiter or Saturn ensure that the matter found there exhibits
an unusual state: It is as dense as a metal but, at the same time,
electrically charged like a plasma. "We refer to this state as warm dense matter," explains Dominik Kraus, physicist at HZDR and professor at the University of Rostock. "It is a transitional state between solid state and plasma that is found in the interior of planets, although it can occur
briefly on Earth, too, for example during meteor impacts." Examining
this state of matter in any detail in the lab is a complicated process involving, for example, firing strong laser flashes at a sample, and,
for the blink of an eye, heating and condensing it.

But what are the chemical properties of this warm dense matter really
like? Up to now, existing methods have only produced unsatisfactory
answers to this question. So, a team from six countries came up with
something new, based on the strongest X-ray laser in the world, the
European XFEL in Hamburg. In an accelerator a kilometer long, extremely
short, intensive X-ray pulses are generated. "We directed the pulses at
thin carbon foils," says lead author Katja Voigt from HZDR's Institute
of Radiation Physics. "They were made of graphite or diamonds." In the
foils, a small proportion of the X-ray flashes is scattered on electrons
and their immediate environment. The crucial thing is that the scattered flashes can reveal what kind of chemical bond the carbon atoms have
formed with their environment.

After the doubts came the surprise Known as X-ray Raman scattering,
researchers in fields like materials science have been using this
method for quite a while. But for the first time, the team around
Voigt and Kraus have managed to equip it for experiments to probe warm
dense matter. "Some experts were doubtful whether it could work," Kraus explains. The detectors, in particular, which have to capture the X-ray
signals emitted by the carbon foils, have to be both highly efficient
and high- resolution -- a major technical challenge. But the analysis of
the measurement data clearly showed which bonding states the carbon had entered. "We were a bit surprised that it worked so well," says Voigt, obviously pleased. If they were to apply the method to warm dense matter, however, something was still missing -- strong laser flashes that would
drive the carbon foils to high pressures and temperatures of up to
several 100,000 degrees. For this purpose, the Helmholtz International
Beamline for Extreme Fields (HIBEF) which was recently inaugurated under
the auspices of HZDR at the European XFEL comes into play. It is one of
the most modern research facilities in the world with high- performance
lasers that could perform the first X-ray Raman experiments in a few
months' time. "I'm really optimistic that it'll work," says Dominik Kraus.

Comet crash in the lab The method could well facilitate many different scientific insights: for one thing, it is unclear how many light elements
like carbon or silicon are present in the Earth's core. Laboratory
experiments could produce important indicators.

"The new method is not restricted to carbon, but could be applied to other light elements," Katja Voigt explains. Another question to be explored addresses the interior of so-called gas giants like Jupiter and ice
giants like Neptune. Here, complex chemical reactions will be occurring
-- as they will in distant exoplanets of similar stature. It should be
feasible to re-enact these processes in the lab using the X-ray Raman
method. "Perhaps it might be possible to solve the puzzle about which
reactions are responsible for planets like Neptune and Saturn emitting
more energy than they really should," Kraus hopes.

In addition, this new method should enable scientists to simulate comet
crashes on a miniature scale: If comets really did transport organic
matter to Earth once up a time -- could the crash have triggered chemical reactions that favored the development of life? And the method even holds potential for technical applications: On principle, it seems possible
that, under extreme conditions, novel materials could form which could
exhibit fascinating properties. One example would be a superconductor
that functions at room temperature and does not need complicated cooling
like existing materials. A room-temperature superconductor of this kind
would be of great technological interest as it could conduct electricity completely loss-free without having to cool it with liquid nitrogen or
liquid helium.

========================================================================== Story Source: Materials provided by
Helmholtz-Zentrum_Dresden-Rossendorf. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. K. Voigt, M. Zhang, K. Ramakrishna, A. Amouretti, K. Appel,
E. Brambrink,
V. Cerantola, D. Chekrygina, T. Do"ppner, R. W. Falcone, K. Falk,
L. B.

Fletcher, D. O. Gericke, S. Go"de, M. Harmand, N. J. Hartley,
S. P. Hau- Riege, L. G. Huang, O. S. Humphries, M. Lokamani,
M. Makita, A. Pelka, C.

Prescher, A. K. Schuster, M. Smi'd, T. Toncian, J. Vorberger,
U. Zastrau, T. R. Preston, D. Kraus. Demonstration of an x-ray
Raman spectroscopy setup to study warm dense carbon at the high
energy density instrument of European XFEL. Physics of Plasmas,
2021; 28 (8): 082701 DOI: 10.1063/ 5.0048150 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211005124833.htm

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