Laser beam combined with metal foam to produce the brightest X-ray

According to the Physicists' Network, scientists from Lawrence Livermore National Laboratory (LLNL) in the United States ingeniously combined the high-power laser emitted by the National Ignition Facility (NIF) with the ultra light metal foam to create the brightest X-ray ever. These ultra bright high-energy X-rays play an important role in many research fields, including imaging of extremely dense matter (including plasma generated during inertial confinement fusion). The relevant research paper was published in the latest issue of Physical Review E.

The laser generated by NIF overlaps the millimeter level cylindrical silver foam target to create high-energy X-ray. Image source: Lawrence Livermore National Laboratory

The team explained the process of creating this type of X-ray: a high-power laser beam collides with silver atoms, exciting plasma and generating X-rays. The higher the atomic number of a metal atom, the higher the X-ray energy it produces.

To produce X-rays with energies higher than 20000 electron volts, the team chose metallic silver in the experiment. Since the foam structure of metal is crucial for creating high-energy X-ray, they used molds and silver nanowires to create a cylindrical target with a diameter of 4mm and a height of 4mm.

The team first freezes the nanowires suspended in the mold solution, then uses supercritical drying technology to remove the solution, and finally leaves low-density porous silver metal foam. The density of this silver foam structure is only one thousandth of that of solid silver.
This foam structure has many advantages: the laser emitted by NIF can heat a larger volume of foam material, and the heat transmission speed is far faster than that in solids. The entire silver foam cylinder was heated by a laser beam in about 1.5 billionths of a second, thus producing the brightest X-ray so far.

In addition to creating the X-ray source, the team also made in-depth exploration on a variety of different foam materials to determine which foam can provide the maximum energy output. Meanwhile, they also employed a novel data analysis technique to understand the physical properties of the generated plasma.

Source: Yangtze River Delta Laser Alliance