How to Catch a Particle: Physicists Found a Way to Make Ion Traps More Efficient

Scientists from ITMO University have developed and applied a new method for analyzing the electromagnetic field inside ion traps. For the first time, they explained the field deviations inside nonlinear radio-frequency traps. This allows for the reconsideration of nonlinear traps applications, including ion cooling and research into quantum phenomena. The results are published in the Journal of Physics B.

An optical trap

Ion traps can localize and confine individual charged particles in a closed space in order to perform subsequent manipulations, for example, move them or cool them down. Cooling down an ion trap basically means reducing the particle’s kinetic energy, which makes it almost completely still. Scientists believe that in the future, this technique will be used to observe quantum phenomena with the naked eye.

There are different types of radio-frequency traps, which vary in terms of the frequency and configuration of the field inside them. More convenient optical traps are used for cooling uncharged particles. As for charged particles, radio-frequency traps are used, as they allow to cool these particles to lower temperatures.

Physicists from ITMO University are actively studying radio-frequency traps and looking for new ways to make them more effective. In their new research, they have proposed a new approach for a more accurate analysis of the electromagnetic field inside a nonlinear radio-frequency trap. Unlike in some simpler linear traps where a charged particle is contained in one spot, particles in nonlinear traps can be “caught” in several spots. Previously developed models were only suitable for simple traps since they could not explain field asymmetry occurring in nonlinear traps. The proposed model is more universal as it explains the symmetry breaking and is suitable for describing both simple and complex traps.

“Our research, which resulted in the development of a new technique, began with a cup of coffee. As a big coffee drinker, I often use a coffee machine at work. Annoyingly, my cup was always sliding off the tray during the coffee preparation, every time in a different direction, which means that it was not caused by the overall tilt of the machine. After studying the literature on vibromechanics, I came to the conclusion that it’s the so-called nonlinear friction that is to blame. Then I realized that this phenomenon can be found in radio-frequency traps that we study. We applied the method of complete separation of motion, used in vibromechanics, and suddenly found out that this allows to describe previously unexplained symmetry breaking in the traps!” shares Semyon Rudyi from Nonlinear Optics Laboratory at ITMO University.

Semyon Rudyi
Semyon Rudyi

Scientists have tested their method on the experimental data obtained in previous studies. Old models of radio-frequency traps were unable to explain strange deviations that occurred in nonlinear traps, which limited the prospects of nonlinear traps application. Within the framework of the proposed model, these deviations were fully justified. The new approach helps to predict and control the localization of charged particles for different electrode positions and voltages. This is necessary for the development of more efficient radio-frequency traps for various applications.

“Even though this work is theoretical, it is closely related to practice. Our laboratory develops new designs of radio-frequency traps and constructs them to consequently localize various charged particles. We also do research into nanocrystals in these traps, since these particles can model quantum effects. Our studies often bring unexpected interesting results and bring us closer to interaction with quantum phenomena,” notes Tatiana Vovk from the Laboratory of Modeling and Design of Nanostructures at ITMO University.

Tatiana Vovk
Tatiana Vovk

Reference: Features of the effective potential formed by multipole ion trap. Semyon Rudyi, Tatiana Vovk and Yuriy Rozhdestvensky. Journal of Physics B. 16 April 2019.

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