At particle accelerators, scientists not only conduct collisions that simulate the conditions of the Universe’s first seconds, but also create rare, exotic particles that are almost never found in nature. In addition to producing these particles, one of the main challenges is to trap and hold them long enough to perform measurements.

Highly charged ions are atoms that have lost several electrons, sometimes becoming fully ionized nuclei without any electron shell. Creating such ions in laboratory conditions requires high energies and strong fields. Typically, these ions are generated in accelerators, where they move at extremely high speeds. For physical experiments, it is necessary to slow down, capture, and cool these ions—a complex task. At the GSI Helmholtz Centre for Heavy Ion Research in Germany, the HITRAP (High Charge Ion Trap) facility was developed specifically for this purpose.

With HITRAP, researchers were able for the first time to slow down and fully capture completely ionized argon ions (36Ar18+) that were traveling at about 30% of the speed of light. This significant deceleration allowed the particles to be held in a Penning trap. For the first time, electronic cooling of highly charged ions was also achieved in such a trap. The results of this experiment were published in the journal Physical Review X.

Light atomic nuclei were shielded from the extreme temperatures typical of accelerators. Previously, it was unclear why light nuclei do not break apart at such high temperatures, but it was discovered that they are not formed in the very center of the collision.

For the first time, a scientific team managed to complete the entire process—from generating highly charged ions to storing them in a special trap for at least 11 seconds.

In a Penning trap, magnetic and electric fields are used to confine particles: the magnetic field restricts movement along one axis, while the electric field confines them along another. In the plane of the third axis, the particle moves along a trajectory determined by the cyclotron frequency. By observing this frequency, researchers can calculate the properties of the trapped particle. To capture the ions, their kinetic energy had to be reduced by about 10,000 times.

Even after this, the ions’ energy remained too high for precise studies, so electronic cooling was applied. A beam of electrons with energy matched to the argon ions was introduced into the trap. During collisions, the electrons absorbed some of the ions’ energy, gradually cooling them and increasing their lifetime in the trap.

This is the first documented case of using electronic cooling in a Penning trap for highly charged ions. Unlike traditional gas cooling, this approach allows ions to be prepared for high-precision measurements and paves the way for further research into heavy, highly charged ions.