Development and characterization of a linear ion trap for an improved optical clock performance

authored by: Tobias Burgermeister
supervised by: Tanja Mehlstäubler
Abstract: Single ion frequency standards have demonstrated in several experiments excellent results and are approaching fractional frequency uncertainties of 10^-18. As dominant contributions to the uncertainty are linked to the ion trap properties a further reduction would be possible by an improved ion trap. Due to the interrogation of a single ion these frequency standards are currently limited by the intrinsically low signal-to-noise ratio and require long averaging times on the order of several days. This limitation is critical for various applications that require a high frequency resolution on short timescales. One possibility to improve the clock stability is to increase the number of clock ions. However, this approach further increases the requirements for the ion trap. Therefore, for the realization of a multi-ion clock that aims at simultaneously reducing the frequency stability and uncertainty the control over the characteristics of the ion trap is crucial. This thesis continues previous work towards the realization of a multi-ion optical clock based on ion Coulomb crystals of 115In+ ions which are sympathetically cooled by 172Yb+ ions. The existing design for a segmented linear ion trap has been refined and a reliable trap manufacturing process for a trap based on gold coated aluminium nitride wafers has been developed. Manufacturing tolerances below 10 μm allowed to reduce the axial micromotion amplitudes substantially. For a region of more than 300 μm the uncertainty contribution of the three-dimensional micromotion amplitude is shown to be below 10^-19. Additionally the radial ion heating rate of the trap has been measured to be 1.1 phonons/s for a trap frequency of 490 kHz. The time dilation shift due to the heating rate on the radial trap axis is found to be (2.1 ± 0.3) x 10^-20 1/s. The trap design has also been optimized for a low trap temperature rise due to the applied rf voltage. Trap temperature measurements with Pt100 sensors installed on the trap showed a maximum temperature increase of 1.21 K at an rf voltage amplitude of 1 kV. By comparing the measurement results to FEM simulations the uncertainty contribution of the trap temperature to the black-body radiation shift has been deduced to be 2.4 x 10^-20. As the ion trap provides a high level of control on Coulomb crystals it also provides an ideal test bed for studying atomic many-body systems. This work presents results of the investigations on topological defects in two-dimensional Coulomb crystals. The emphasis was placed on the effects of mass defects and external electric fields on the stability of the topological defects. It is shown that these effects can be used to manipulate and create topological defects deterministically.
Organisation(s): QUEST-Leibniz Research School
Type: Doctoral thesis
No. of pages: 144
Publication date: 2019
Publication status: Published
Electronic version(s): https://doi.org/10.15488/5160 (Access: Open)
: Details in the research portal "Research@Leibniz University"

BibTeX

@phdthesis{869a3093b4554a5297fc1d067470f8b3,
title = "Development and characterization of a linear ion trap for an improved optical clock performance",
abstract = "Single ion frequency standards have demonstrated in several experiments excellent results and are approaching fractional frequency uncertainties of 10^-18. As dominant contributions to the uncertainty are linked to the ion trap properties a further reduction would be possible by an improved ion trap. Due to the interrogation of a single ion these frequency standards are currently limited by the intrinsically low signal-to-noise ratio and require long averaging times on the order of several days. This limitation is critical for various applications that require a high frequency resolution on short timescales. One possibility to improve the clock stability is to increase the number of clock ions. However, this approach further increases the requirements for the ion trap. Therefore, for the realization of a multi-ion clock that aims at simultaneously reducing the frequency stability and uncertainty the control over the characteristics of the ion trap is crucial. This thesis continues previous work towards the realization of a multi-ion optical clock based on ion Coulomb crystals of 115In+ ions which are sympathetically cooled by 172Yb+ ions. The existing design for a segmented linear ion trap has been refined and a reliable trap manufacturing process for a trap based on gold coated aluminium nitride wafers has been developed. Manufacturing tolerances below 10 μm allowed to reduce the axial micromotion amplitudes substantially. For a region of more than 300 μm the uncertainty contribution of the three-dimensional micromotion amplitude is shown to be below 10^-19. Additionally the radial ion heating rate of the trap has been measured to be 1.1 phonons/s for a trap frequency of 490 kHz. The time dilation shift due to the heating rate on the radial trap axis is found to be (2.1 ± 0.3) x 10^-20 1/s. The trap design has also been optimized for a low trap temperature rise due to the applied rf voltage. Trap temperature measurements with Pt100 sensors installed on the trap showed a maximum temperature increase of 1.21 K at an rf voltage amplitude of 1 kV. By comparing the measurement results to FEM simulations the uncertainty contribution of the trap temperature to the black-body radiation shift has been deduced to be 2.4 x 10^-20. As the ion trap provides a high level of control on Coulomb crystals it also provides an ideal test bed for studying atomic many-body systems. This work presents results of the investigations on topological defects in two-dimensional Coulomb crystals. The emphasis was placed on the effects of mass defects and external electric fields on the stability of the topological defects. It is shown that these effects can be used to manipulate and create topological defects deterministically.",
author = "Tobias Burgermeister",
note = "Doctoral thesis",
year = "2019",
doi = "10.15488/5160",
language = "English",
publisher = "Leibniz Universit{\"a}t Hannover",
school = "Leibniz University Hannover",
}