The development of more powerful technologies has made it possible to generate ultra high vacuum spaces, taking high vacuum one step further. In this post, we analyse what exactly ultra high vacuum is and the main applications of ultra high vacuum chambers.
What is ultra high vacuum?
Ultra high vacuum is considered the ultimate evolution of high vacuum: the system in which the pressure is below 10-7 mbar is called ultra high vacuum.
Vacuum space is defined as space in which less than atmospheric pressure has developed so that gases can be removed from the internal surfaces. Thus, depending on the pressure value of these gases, there are different degrees of vacuum, the highest degrees of vacuum being those with the lowest atmospheric pressure. Following this definition, ultra high vacuum occurs in spaces with the lowest atmospheric pressure.
The first vacuum produced in a laboratory environment took place in 1643, using the experimental atmospheric pressure techniques carried out by Evangelista Torricelli. Today, progress in this area of study has made it possible to create ultra high vacuum systems.
Ultra high vacuum vs high vacuum
The difference between high vacuum and ultra high vacuum systems lies in the different atmospheric pressures:
- In high vacuum, the pressure range is from 10 -3 to 10 -7 mbar. The waste gases have a high water vapour content (H2O).
- In ultra high vacuum, the atmospheric pressure ranges from 10 -7 to 10 -12 mbar. The waste gases present hydrogen as the dominant component. These low pressures also allow the internal surfaces to be kept clean of gas.
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Technical issues: produce ultra high vacuum
The main challenge of ultra high vacuum spaces is to produce pressures below 10-7 mbar. To achieve this, different technologies can be used:
- Turbomolecular pump: This type of vacuum pump is highly versatile and can produce medium to ultra high vacuum. A turbine rotor is used to achieve this which, turning at high speed, causes the gas molecules to collide, generating the vacuum.
- Ionic pump: this is a less effective pump for noble gases, although it can reach pressures below 10-11 mbar. To do this, it ionises the gas molecules using a high-intensity magnetic field and incites a cloud of electrons. The gas molecules are then captured, generating high vacuum and ultra high vacuum spaces.
- Cryogenic pump: cryogenic pumps can reach pressures less than 10-10 mbar. They use cryocondensation (condensation at low temperatures) to remove gaseous substances and generate ultra high vacuum spaces. Gases with a lower molecular weight and, therefore, with more condensation difficulties, thus receive treatment at lower temperatures.
In addition to these technologies, there are other technical issues around ultra high vacuum that must be taken into account:
- Suitable maintenance and control programmes are required, in which vacuum levels and other safety issues, such as detecting possible leaks, must be checked frequently.
- It is essential to follow the appropriate quality standards and testing protocols for each project.
- In the design phase of the ultra high vacuum system, special attention must be paid to the materials used and the construction techniques. Some good practices include minimising the internal surface of the chamber, using metal seals and vacuum compatible materials, among other actions.
- The selection of the appropriate pump must take efficiency and reliability into account, considering the specific substances used in the project.
- While the system is operational, careful attention must be paid to ensure there are no degassing levels that could interfere with creating an ultra high vacuum space.
Ultra high vacuum uses and applications
The ability of ultra high vacuum chambers to eliminate contamination on surfaces and generate ultra high vacuum spaces is required in different industries and research sectors, including:
- Some metallurgical and industrial processes require ultra high vacuum environments to prevent damage to manufactured products.
- Surface science uses ultra high vacuum to conduct research around surface analysis, including spectroscopy.
- High energy physics and nuclear physics processes also make use of ultra high vacuum chambers. These include particle accelerators or isotope separators, for example.
- Some developments around optics and electronics require ultra high vacuum systems.