What are the conditions and applications of ultra-high vacuum pumps?
October 21, 2022
4 MIN READ
High-performance vacuum equipment is an essential element of a wide range of industries and scientific fields of research. Many industries and academic research fields require different levels of vacuum to succeed. This blog will focus on the many types of industries and scientific fields that rely on both high vacuum (HV) and ultra-high vacuum (UHV) equipment.
Because these systems require extremely low pressure to function effectively, only the most advanced types of vacuum equipment can produce the necessary vacuum conditions for these systems to function.
What are high and ultra-high vacuums?
High vacuum and ultra-high vacuum are defined by the pressure that is present in the vacuum chamber. While the classification of HV and UHV can vary according to the source, a high vacuum is generally considered to be a pressure range between 10-3 and 10-7 mbar, and an ultra-high vacuum is considered to be a pressure range below 10-7 mbar.
Though these may seem like insignificant distinctions in day-to-day life, the reality is that extremely low pressure is crucially important for numerous industrial processes, engineering techniques, and scientific experiments. As such, both HV and UHV equipment have a multitude of significant applications across multiple industries and scientific disciplines.
What are the advantages of high and ultra-high environments?
There are two main advantages to HV and UHV conditions, the biggest of which is the minimization of contamination, both on surfaces and in the vacuum of the chamber. While no surface can be rendered entirely free of contamination, the extremely low pressures produced by ultra-high vacuum minimize contamination to a sufficient level that surfaces can maintain pristine conditions for long enough to carry out the required experiments.
The other main advantage of HV and UHV conditions is to limit interactions between the residual gas and particle beams that are present in a multitude of vacuum applications. Limiting these interactions can also be referred to as increasing the mean free path of particles in the vacuum, usually electrons or other ions.
While it might not seem like it, the air is quite thick, especially from the point of view of an electron. In normal atmospheric pressure, an electron can only travel about 50 nanometers, which means it stops almost as soon as it gets started. To increase the mean free path to a more useful distance of even a few meters, the pressure in the system needs to be in the range of 10-4 to 10-6 mbar.
High and ultra-high vacuum applications
Some of the most common examples of the application of UHV equipment are techniques that require the reduction of surface area contamination to perform essential surface analysis. Different types of spectrometry, spectroscopy, and microscopies, such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, and scanning tunneling microscopy, all require uncontaminated surface areas to accurately identify the chemical composition and structure of a given material. The necessary level of decontamination can only be achieved with extremely low pressures.
The reduction of beam-gas interactions is also important for many of these techniques. For example, in X-ray photoelectron spectroscopy, a beam of X-rays is focused on the material. These high-energy photons knock electrons out of the material. The electrons need to travel a distance of at least a meter, sometimes more, to reach a detector. Vacuum is essential for providing these electrons the necessary mean free path to reach the detector.
Some industrial processes also require HV and UHV, once again for beam-gas-interaction reduction benefits. One example of this is electron beam welding. In this HV application, a beam of high-energy electrons is applied to two materials that need to be joined. The materials melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact.
Both high and ultra-high vacuums have additional applications in the field of physics. For example, particle accelerators (such as the Large Hadron Collider at CERN) require ultra-high vacuum conditions for reducing beam-gas interactions and minimizing interference from the exterior environment. This is also true for other tools in experimental physics, such as gravitational wave detectors.
HV and UHV conditions are also in high demand in the fields of aerospace engineering, biomedical technologies, analytical instrument manufacturing, mass spectroscopy, electron microscopy, space simulation, coating, and medical diagnostic equipment.
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