How X-Ray Microscopy Works & How We Save You Time & Money

X-ray microscope components can vary significantly based on design; however, each model typically has three main parts:

• X-ray Optics
• X-ray Source
• Detection device

X-ray optics are specifically designed to manipulate X-rays rather than visible light because X-rays behave pretty differently than visible light. Visible light is easily redirected using lenses and mirrors. That said, X-rays change direction much less, as they are prone to penetrating and being absorbed by an object.

Instead, various techniques are used to redirect X-rays where they need to go. This includes diffraction and interference, typically in the form of various compound refractive lenses and zone plates and certain types of crystals and crystal planes.

Initially, a tungsten filament inside a vacuum tube was used as the X-ray source in these microscopes. However, the development of synchrotron radiation as an X-ray source opened up new possibilities in X-ray microscopy. The synchrotron light source was brighter and more brilliant and tunable and coherent as well.

Furthermore, synchrotron radiation-producing imaging systems can be coupled with spectroscopy to map chemical composition with sub-micron resolution. This includes X-ray fluorescence and X-ray spectroscopy.

There are different types of X-ray detectors for other applications. However, one of the most common detection devices in X-ray microscopes tends to be the charge-coupled device (CCDs) detector, a highly sensitive photon detector essential to digital imaging today. These detectors are excellent for measuring spatial intensity distributions.

Other detectors include X-ray photographic film, image plates, scanning point detectors, converter screens, and more.

X-ray microscopy is generally categorized as either full-field or scanning. However, full-field X-ray microscopy can be divided into two distinct versions. The first involves lensless imaging with parallel and conical beams. The second version is most commonly seen in transmission X-ray microscopes, which use the same optical configuration as conventional light microscopes and transmission electron microscopes.

Full-field microscopes use optical elements like Fresnel zone plates or refractive optics as objective lenses for high-resolution imaging and typically image the whole field of view to a detector plane simultaneously.

In a scanning X-ray microscope, a small but intensive X-ray beam is used to scan the sample, creating a finely focused spot or microprobe through which the sample is rasterized, or converted as an image into pixels. The extremely small X-ray beam is typically generated using focusing optics. In this case, an X-ray optic.

Each sample position produces an X-ray signal during the scan, which is then recorded. These signals include X-ray fluorescence, absorption spectroscopy, or diffraction. In this way, the sample’s elemental, chemical, and structural information can be determined.

Using high-energy X-rays or gamma rays, XRF microscopes can analyze the secondary, or fluorescent, X-rays that are excited by the sample. These secondary emissions can then be analyzed to produce an image.

When the gamma rays strike molecules, they fluoresce at specific energies, allowing for elemental image analysis. This technique also gives the user depth control and horizontal and vertical aiming control. Advanced models can analyze and image multiple elements at once.

Besides electron microscopes, most conventional microscopy could not provide fully 3D, high-resolution images without destructive sectioning. That said, three-dimensional (3D) X-ray microscopy is an exception; it’s a non-destructive 3D imaging method able to image submicron to the nanometer scale.

X-rays’ inherent penetrative qualities and their ability to not harm organic material allow this to happen.

By employing a zone plate to focus the X-ray beam onto a specific and small area, STXM allows for analyzing wet samples. Specifically, STXM uses near-edge X-ray absorption spectroscopy as the contrast mechanism to produce an image.

Samples in water pose issues when being imaged due to how various forms of light interact with water. X-rays can penetrate water and only interact with the sample.

Another significant advantage of STXM, as opposed to other similar transmission microscopy techniques, is that it inflicts relatively minimal damage to the actual material.

Three-dimensional X-ray diffraction microscopy, which has led to the implementation of high-energy X-ray diffraction microscopy (HEDM), is a somewhat young technique. However, it is pretty powerful (and, of course, nondestructive).

X-ray diffraction microscopy uses the far-field scattering of coherent X-rays to form the 2D or 3D image of a scattering object in a way that resembles crystallography.

HEDM generates a map of the internal crystalline structure of a sample and allows researchers to obtain specific information regarding the object’s internal measurements on a tiny scale.

Thanks to its non-destructive qualities in hard materials like ceramics and metals, it is an invaluable technique in materials science.

X-rays were discovered by professor Wilhelm Röntgen in 1895. While a professor of physics at the University of Würzurg, he was looking into how vacuum tubes would react to various forms of external stimuli.

During his studies, while working with a tube where an aluminum window was added to allow for a cathode ray to escape, the tube was covered with a cardboard box. This was meant to prevent any light from escaping; however, during his experiments, he noticed that the cathode rays caused a fluorescent effect on the part of the cardboard that was painted with barium platinocyanide.

Determined to satisfy his curiosity, Röntgen reconstructed his initial setup, only this time using a black cardboard box and a thicker walled tube. Passing an electric charge through the tube with a coil, he turned off the lights of his lab to test that the cardboard box was indeed lightproof.

When he did this, he noticed that the barium platinocyanide screen he intended to use was shimmering. Immediately he speculated that it must be due to some new type of ray that he temporarily labeled the “X-ray.” The X was denoting that it was still unknown. For the next few days, Röntgen would spend every waking hour in his lab testing what was causing this glow.

He produced the first X-ray image of his wife’s hand during his initial experiments, showing the bones inside. When he showed it to her, she exclaimed that “I have seen my death!”

Röntgen would publish all his findings in a paper called “On A New Kind of Rays” on December 28th, 1895. The radiation would be called Röntgen radiation, after Wilhelm Röntgen, but would continue to be known as X-ray.