Using powerful machinery originally developed in the hope of discovering a way to generate energy from hydrogen fusion, scientists in Cornell’s Laboratory of Plasma Studies are creating high-resolution images of minute objects, like fly hairs or the fine filaments that keep dandelion seeds afloat in the air.
The machine that produces the images runs a powerful electrical current through a vacuum chamber containing a pair of crossed wires, each many times finer than a human hair.
The current is reportedly so strong that it causes the wires to explode, forming plasma, a dense gas that has become so hot that the atoms in it break down. This plasma is known as the X-pinch, and it is particularly hot and dense at the cross point of the wires.
What makes the X-ray images it produces so special is their extremely fine resolution. Consequently, the very fineness of this detail is being used to determine the size of the X-pinch plasma.
The Cornell lab has been working for the past few years with Sandia National Laboratories to develop an inertial confinement fusion system that uses X-rays.
The so-called Z-machine that has been built at Sandia is designed to generate an extremely high-power X-ray pulse to create temperatures in the millions of degrees that would result in fusion of hydrogen fuel. This same research also has yielded the unexpected discovery of X-pinch imaging.
The plasma created by the exploding crossed wires lasts for less than one microsecond, but in that time it implodes and forms one or two plasma points with temperatures as high as 10 million degrees Celsius that last for less than a billionth of a second.
The high-density plasma, which has almost the same density of a solid, generates bursts of X-rays that can produce extremely high-resolution radiographs of very small objects.
Because the detail shown in the radiograph is determined by the size of the X-ray source, microscopic details can be shown at very high resolution. The plasma points that emit the X-rays are reportedly so small that their size is still unknown.
‘What we’re doing now is making little nanofabricated structures, and then we will image those structures and see what the resolution is,’ said David Hammer, the JC Ward Professor of Nuclear Energy Engineering at Cornell.
The first images the researchers obtained were poorly defined but as the technique has been refined, the images have become sharper. Recently developed radiographs of a dead housefly, collected from the floor of the laboratory, show fine structures, such as hairs, only a few microns across. As with traditional X-rays, it is also possible to take X-pinch radiographs of living organisms.