What Is the Best Material for X-ray Collimation – Tungsten Metal or Tungsten Alloy?

A collimator is a device used to transform the divergent light or other radiation from a point light source into a parallel beam, and also is an absorber device used to limit X-rays, gamma rays, or nuclear particle beams to the size and angular spread required for a specific application. Normally, special measurements in spectroscopy and geometric and physical optics require this kind of light collimation.

For reasons of patient dose and image quality, X-ray collimation for radiography and fluoroscopy projection imaging is important. Actively collimating the volume of interest will reduce the overall integrated dose to the patient, thereby minimizing the risk of radiation. Less radiation will result in less X-ray scattering incident on the detector. This leads to improved object contrast and image quality.

In a linear accelerator (linac), the main collimator may be made of depleted uranium because the density of this material is approximately 1.6 times that of lead. The secondary electric collimator can better define the beam shape and is made of lead or tungsten. The multi-leaf collimator (MLC), which is now widely used in medical linear accelerators, consists of two thin tungsten "leaf" collimator groups, each group consisting of 40 to 80 leaves composition. 

As depleted uranium and lead materials are not easy to completely eliminated by the body after entering the human body, and will damage the internal organs, tungsten metal is the most popular materials for this device now. Generally spreading, the higher density of the material, the better radiation protection. Why tungsten alloy collimator is more popular compared with pure tungsten collimator? 

The density of tungsten metal is high, however, it is also easy to fragile during machining if you use powder metallurgy to produce, especially for complex collimator. Therefore, tungsten alloy, added with the element of nickel, copper or iron, help improve the problem. The alloy has high density, better processability and good anti-radiation, and thus most collimators are made of this material. 

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3D Printing Pure Tungsten Parts in the Medical Industry

Tungsten, also known as Wolfram, is a rare metal known for its highest melting point of all elements. In addition to excellent temperature resistance, the material also has strong abrasion resistance and chemical resistance. These good properties make it an ideal material for components that operate at extreme temperatures.

Pure tungsten does not have the hardness of composite materials, but its excellent heat resistance and radiation shielding properties are very useful in the nuclear and medical industries. The medical industry generally uses pure tungsten for MRI scans, collimators, and radiation shielding. But there is a problem: it is very brittle at room temperature, which means it is difficult to process using traditional techniques.

For simple collimators, radiation shielding and other products, powder metallurgy technology can be used to process, but for high precision and complex parts, using traditional technology is suffering. Therefore, the emergence of 3D printing has solved this thorny problem.

The principle of 3D printing is to use electrons accelerated in a vacuum to melt metal powder. By moving the electron beam, 3D components can be produced from metal by means of addition. This technology was originally developed for titanium alloys and materials that require high processing temperatures.

The tungsten metal powder is preheated before it is melted. This preheating procedure reduces the deformation and internal stress of the metal, making it possible to process materials that are easily broken at room temperature but deform when heated. The printed product basically does not need to be processed again, unless there are special requirements for precision or other requirements.

Tungsten provides characteristics rarely seen in 3D printing materials. It is non-magnetic, good at absorbing and shielding radiation, so that 3D printing pure tungsten parts can be widely used in the nuclear energy industry and medical industry. 3D printed tungsten collimator is one of them. Chinatungsten Online is a professional manufacturer of tungsten and molybdenum, which can provide 3D tungsten products.

If you have any inquiry of 3D printing pure tungsten parts, please feel free to contact us:
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Why Use Thorium Tungsten Wires as Ion Source?

Many analytical and medical devices are using thorium tungsten wires as ion source. Why use thorium tungsten materials? What about tungsten or neodymium tungsten materials? 

Electrons are made available from a cathode in the source, which in most cases will use thermionic emission, i.e., heating the material so that electrons gain some energy and are able to escape the work function of the cathode material (the energy required per electron to leave the material). To lower work function, manufacturers would like to use thorium tungsten filaments. 

Doping a tungsten wire with thorium can effectively improve the thermionic emission. Doping lowers the work function of the system, resulting in a thermionic current greater than the one produced from a pure W filament. Why it happens? What are the mechanisms that lower the work function?

An idea is that thorium is an α-emitter. The 4He nuclei then produce scattering sources for the electrons, enhancing the emission probability. And according to Electronics Engineer's Reference Book, the mechanism is that thorium is added to the tungsten filament, and then the whole thing is heated significantly hotter than its normal working temperature. This causes the thorium to migrate to the surface of the filament, resulting in essentially a thorium-plated tungsten filament. Thorium has a lower work-function than tungsten so the effective work-function of the filament is that of thorium.

Some manufacturers have tried alternative materials, like neodymium tungsten rods for lamp electrodes, it works good for certain lamps but it does not for other lamps. Just like mercury for many types of lamps, thorium tungsten seems to be very mighty. Only the problem is quantities for these lamp manufacturers and device manufacturers are not large as thorium belongs to radioactive material. 

Due to regulation in Europe, transfer of thorium powder is very limited if not banned, there are a lot of papers to talk about this thorium powder ban, because it can be considered as Radioactive if it is concentrated very high, such as thorium powder. however, for thorium wires or rods, they are usually low in concentration, which is harmless to the health. 

Chinatungsten Online is a professional manufacturer of tungsten for more than two decades, if you have got the purchasing plan for thorium tungsten wires or rods, do feel free to contact us.

If you have any inquiry of thorium tungsten wires, please feel free to contact us:

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