Novel Penning trap design delivers optical access for precise spectroscopy

Penning traps are tools for confining ions within an electric and magnetic field for characterization by precision spectroscopy. Maintaining an electrically closed system, however, often restricts optical access. New trap geometries seek to optimize light accessibility, and the benefits of a new “half-open” cylindrical Penning trap are described in Review of Scientific Instruments.

Inspired by its use in other industries, scientists replaced one electrode of their Penning trap with glass coated with a 100-nanometer layer of indium tin oxide (ITO), a doped n-type semiconductor. They showed that this design can maintain stable confinement for extended periods of time without any charge buildup on the window. The coating was also found to withstand cooling to 4 Kelvin and the bombardment of high energy ions. The high surface quality of the glass was key in achieving harmonic confinement of ions in close proximity to the electrode.

The window permits light accessibility with large solid angles and enables optical excitation of ions and efficient light collection from the trapping region. The ITO layer is largely transparent and an anti-reflection coating on the outer surface of the glass minimizes stray light.

To further extend the application, co-author Manuel Vogel said, “We are planning to increase the degree of optical access, and see if we can replace more parts of the Penning trap with glass elements.” They are also looking to structure the ITO layer and emphasized the applicability of this design to other areas, like quantum computing, where individual ions are manipulated with a laser.

Source: “Optically transparent solid electrodes for precision Penning traps,” by M. Wiesel, G. Birkl, M. S. Ebrahimi, A. Martin, W. Quint, N. Stallkamp, and M. Vogel, Review of Scientific Instruments (2017). The article can be accessed at https://doi.org/10.1063/1.5002180 .