CERN: How does matter really hold together?

99.9 per cent of the interior of atoms consists only of a vacuum – of nothing. One of Lund’s research teams is using equipment at CERN to study this.They are investigating the limits of when the nuclei of atoms collapse.
Lund colleagues Joakim Cederkäll and Claes Fahlander show us around wires and cylinders covered in foil. We are in the ISOLDE experiment station at CERN. This is where their research team spends part of its working day.
Their overall aim is to understand the functioning of the forces within the nucleus of the atom; they are particularly interested in studying extremely short-lived atomic nuclei. In certain physical processes out in space, such as supernova explosions, it is this type of nucleus that both creates and participates in the gigantic explosions.

“We want to compare the different energy levels and life lengths of unstable nuclei”, says Joakim Cederkäll, professor of nuclear physics at the Department of Physics.

He explains that this is pure basic research, but also points out that the detectors that the researchers have developed for this type of experiment have also been put to use in other areas, such as the so-called PET camera in medical technology.

After a tour of a few minutes, Joakim Cederkäll stops and points to a shiny cylindrical component which is part of the equipment for which the Lund researchers are responsible at the ISOLDE experiment station. It is with this piece of equipment that the researchers are to accelerate the unstable nuclei.

”These nuclei can exist for a few milliseconds at most, so you have to be quick to make the most of them”, says Joakim Cederkäll.

He explains that he has always been fascinated by how matter is able to hold together. What is it, for example, that makes it possible to stand on the floor and not fall through it? Joakim Cederkäll gives an account of a couple of the four known forces that govern the universe, on the one hand the weak force that is created between the nucleus of an atom and the spinning electrons, on the other the strong force which exists within the nucleus itself. It is this strong force that the researchers want to find out more about in this context.

They get the raw material for the experiment itself from CERN’s proton accelerators. The protons are introduced into the ISOLDE facility where they are made to collide with a heavy element which causes the nuclei to split. The resulting unusual, short-lived nuclei are in turn accelerated against a new collision substance, a so-called secondary radiation target, so that their properties can be studied.

In total, ISOLDE has between 300 and 400 users. The existing accelerator at the experiment station will be replaced in the future by six new modules, forming a new accelerator which will be 16 metres long all together. One of the modules will be built within the framework of the CATE project (see article on this).

Text: Lena Björk Blixt

Footnote. In addition to the weak and the strong force there are two more types of force according to the science of today: gravitation and electromagnetic force.

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