Researchers at the Department of Energy's SLAC
National Accelerator Laboratory have used
ultra-short wavelengths of X-ray (X-ray laser)
to record in detail the microscopic motion and effects of shock waves rippling
across diamond. This is the first time that scientists have been able to
directly image the shock wave using x-rays.
Using bright and short X-ray
flashes, the team led by
Deutsches Elektronen-Synchrotron (DESY) researchers filmed the rapid and
dynamic changes taking place in the shock wave with a high spatial and a high
The findings open up a valuable new perspective
on the dynamic behaviour of diamond under high pressure. This novel technique
would allow scientists to study the properties of matter. It would open up new
possibilities for precisely exploring the complex physics involved in massive
star explosions, which are crucial for understanding fusion energy. It would
also help in improving the scientific models used to study these phenomena.
Bob Nagler, a staff scientist at the Linac Coherent
Light Source (LCLS) X-ray laser, a DOE Office of Science User Facility, said,
"What is really exciting is that we can capture images of what happens on
microscopic scales. People have used X-rays to produce images of shock waves,
but never on the tiny scale that LCLS makes possible. The ability to measure
shock wave properties so clearly at this scale, down to one-thousandth of a
meter, can be useful to understanding the fundamental physics at work on far
larger scales, too."
Dr. Andreas Schropp, a staff scientist at
Germany's DESY lab and the first author of the study, said, "With our
experiment we are venturing into new scientific terrain. We have managed for
the first time to use X-ray imaging to quantitatively determine the local
properties and the dynamic changes of matter under extreme conditions."
For the study, researchers analysed diamond
samples with the world's most powerful X-ray laser, the LCLS. With a brief
flash from a powerful infrared laser, they triggered shock waves in thin (0.3
millimetres thick) one-inch-long sliver of diamond. Then the team hit the
diamond samples with LCLS X-ray pulses at regular time intervals of hundreds of
These X-ray pulses last just 50 millionths of a
billionth of a second (50 femtoseconds), thus allowing the researchers to
capture even the fastest movements. However, the diamond sample was destroyed
with every shot, and the scientists had to repeat the experiment with identical
specimens for each picture. Every image was taken a little later to show the
shock wave at a slightly later time. Finally, these X-ray images were compiled
to create an ultra slow movie that shows how a shock wave whips through the
diamond faster than the speed of sound.
Schropp said, "LCLS's pulses, just 50
quadrillionths of a second long, 'freeze' the motion of this elastic wave as
it's propagating through the material."
The researchers then used an X-ray technique
called 'magnified phase-contrast imaging' to determine density changes in
diamond into vivid, high-resolution shock wave images. This analysis yielded
information about the compression of the diamond's structure and the pressure
changes caused by the shock wave. The experiment revealed that the intense
shock wave compressed the diamond locally by almost 10%.
The study offers new insights into the structure
of diamonds. Prof. Jerome Hastings of SLAC said, "In view of the
remarkable physical properties of diamond it continues to be important both
scientifically and technologically. We have for the first time directly imaged
shock waves in diamond using X-rays and this has opened up new perspectives on
the dynamic behaviour of diamond under high pressure."
The penetrating properties of X-rays would
enable this technique to be applied to virtually any solid material, such as
iron or aluminium.
DESY physicist Prof. Christian Schroer said,
"The method is important for a series of applications in material science
and for describing the physical processes occurring inside planets."
The study has been published in Scientific