The void, in reality, is not empty. In our universe it never has been. Nor will it be. One way of defining it that is easy to get comfortable with is to describe it as a region of space in which there is an absolute absence of matter and energy.

This is the classic conception of emptiness, and it invites us to accept that they can exist, and do exist, different degrees of vacuum that it is possible to identify by comparing the pressure in the region of space that we want to measure with the atmospheric pressure.

However, this view has been superseded by modern science. The development of relativistic mechanics and quantum mechanics has allowed scientists to elaborate a description of the vacuum much more adjusted to reality in which it is conceived as a physical state of a system that is linked at minimum energy that this can have.

From the perspective of quantum mechanics the vacuum is not empty; contains waves that originate randomly. Also, these waves behave like particles, so one way to define this quantum vacuum is to describe it as a soup of particles that arise and are destroyed very quickly.

This is what is known as vacuum fluctuations, and the best tool we have to understand them is Heisenberg’s uncertainty principle. This is the idea behind the existence of our universe, but what interests us in this article is something a little more mundane.

Measuring how empty the vacuum is is very important for making chips

The quality of the vacuum, understood as the minimization of the amount of matter and energy contained in a certain region of space, often makes the difference. And we are not talking about a theoretical lucubration; there are many scenarios where in practice it is very important have a quality gap.

The extreme ultraviolet photolithography (UVE) machines manufactured by ASML and installed in the chip factories of companies such as TSMC, Intel or Samsung, among others, house inside a large vacuum chamber designed to minimize the chance that an airborne dust particle could physically damage a part of a silicon wafer.

Another example that clearly illustrates the need to obtain a quality vacuum is the tubes of the particle accelerators through which the particles that are being accelerated circulate driven by very powerful magnetic fields. Or the vacuum chamber of experimental nuclear fusion reactors inside which the fusion of deuterium and tritium nuclei takes place.

These are just three of the scenarios in which it is important in practice to measure the quality of the vacuum, and all of them can benefit from the finding made by a group of researchers from the National Institute of Standards and Technology (NIST) in the United States. And it is that this team has elaborated a very sophisticated procedure that, according to the first tests that it has carried out, evaluates the vacuum more accurately than any other system.

Currently, the procedure used in most industrial and research facilities in which a vacuum chamber is used uses sensors designed to identify an electrical current, no matter how minimal, when the molecules of the gas housed inside the enclosure are ionized. . The problem is that this system degrades over time, so it needs to be recalibrated to prevent its reliability from sinking.

In this photograph we can see how one of the NIST researchers adjusts the vacuum measurement device that he and his colleagues have designed. The metallic cylinder on the right is the vacuum chamber that is being used to take the measurement.

The NIST researchers’ proposal is different. What they have done to measure the vacuum of the chamber is to ponder the number of gas molecules present inside the enclosure measuring their interaction with a set of lithium atoms confined and cooled to a temperature very close to absolute zero (-273.15 degrees Celsius) and on which a laser shines.

The interesting thing is that this procedure, according to the researchers who have designed it, is very precise, and, furthermore, the measurement equipment does not require to be calibrated. At the moment this strategy has only passed the first test of the set of tests that it must pass to be officially established as a measurement standard. But it looks very good. Everything is to have something as exotic as the void better tied. And, by the way, to understand it a little better.

Images: NIST