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

Publikation: Qualifikations-/Studienabschlussarbeit › Dissertation

Autoren

  • Tobias Burgermeister

Organisationseinheiten

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Details

OriginalspracheEnglisch
QualifikationDoctor rerum naturalium
Gradverleihende Hochschule
Betreut von
  • Tanja Mehlstäubler, Betreuer*in
Datum der Verleihung des Grades12 Juli 2019
ErscheinungsortHannover
PublikationsstatusVeröffentlicht - 2019

Abstract

In mehreren Experimenten haben Frequenzstandards auf der Basis von einzelnen Ionen hervorragende Ergebnisse erzielt und nähern sich einer relativen Frequenzunsicherheit von 10^-18 an. Eine weitere Reduzierung der Frequenzunsicherheit wäre durch eine verbesserte Ionenfalle möglich, da dominante Beiträge der Frequenzunsicherheit auf die Eigenschaften der Ionenfalle zurückzuführen sind. Aufgrund der Abfrage eines einzelnen Ions sind diese Frequenznormale zur Zeit durch das intrinsisch niedrige Signal-Rausch-Verhältnis limitiert und benötigen lange Mittelungszeiten in der Größenordnung von mehreren Tagen. Diese Limitierung ist für verschiedene Anwendungen, die eine hohe Frequenzauflösung nach kurzen Mittelungszeiten erfordern, ein kritischer Punkt. Die Frequenzstabilität kann durch eine höhere Anzahl von Uhrenionen verbessert werden. Allerdings werden durch diesen Ansatz auch die Anforderungen an die Ionenfalle weiter erhöht. Aus diesem Grund ist für die Realisierung einer Multi-Ionen Uhr, die gleichzeitig die Frequenzstabilität und -unsicherheit weiter verringern soll, die Kontrolle über die Eigenschaften der Ionenfalle von entscheidender Bedeutung. Diese Dissertation setzt frühere Arbeiten zur Realisierung einer optischen Multi-Ionen-Uhr auf der Basis von Coulomb-Kristallen aus 115In+-Ionen, die durch 172Yb+-Ionen sympathisch gekühlt werden, fort. Das existierende Design einer segmentierten linearen Ionenfalle wurde optimiert und es wurde ein zuverlässiger Herstellungsprozess basierend auf goldbeschichteten Aluminiumnitrid-Wafern entwickelt. Durch Fertigungstoleranzen von weniger als 10 μm konnte die axiale Mikrobewegungsamplitude deutlich reduziert werden. Es wird gezeigt, dass in einem Bereich von über 300 μm der Beitrag der dreidimensionalen Mikrobewegung zur Frequenzunsicherheit unterhalb von 10^-19 ist. Zusätzlich wurde die radiale Heizrate der Falle mit 1,1 Phononen/s bei einer Fallenfrequenz von 490 kHz bestimmt. Die Frequenzverschiebung durch Zeitdilatation durch die Heizrate der radialen Fallenachse beträgt damit (2,1 ± 0,3) x 10^-20 1/s. Das Fallendesign wurde ebenso auf einen geringen Anstieg der Fallentemperatur durch die angelegte HF-Spannung optimiert. Die Messungen der Fallentemperatur mit den auf der Falle installierten Pt100 Sensoren zeigten einen maximalen Temperaturanstieg von 1,21 K bei einer HF-Spannungsamplitude von 1 kV. Durch den Vergleich der Messergebnisse mit FEM-Simulationen wurde der Beitrag der Fallentemperatur zur Frequenzverschiebung durch die Schwarzkörperstrahlung mit 2,4 x 10^-20 bestimmt. Da die Ionenfalle eine sehr gute Kontrolle über Coulomb-Kristalle bietet, eignet sie sich auch hervorragend für Experimente mit atomaren Vielteilchensystemen. Hierzu werden in dieser Arbeit Untersuchungen topologischer Defekte in zweidimensionalen Coulomb-Kristallen vorgestellt. Der Schwerpunkt lag dabei auf der Analyse des Einflusses von Massendefekten und externen elektrischen Feldern auf die Stabilität der topologischen Defekte. Es wird gezeigt wie dieser Einfluss genutzt werden kann, um die Defekte gezielt zu manipulieren und sie deterministisch zu produzieren.

Zitieren

Development and characterization of a linear ion trap for an improved optical clock performance. / Burgermeister, Tobias.
Hannover, 2019. 144 S.

Publikation: Qualifikations-/Studienabschlussarbeit › Dissertation

Burgermeister, T 2019, 'Development and characterization of a linear ion trap for an improved optical clock performance', Doctor rerum naturalium, Gottfried Wilhelm Leibniz Universität Hannover, Hannover. https://doi.org/10.15488/5160
Burgermeister, T. (2019). Development and characterization of a linear ion trap for an improved optical clock performance. [Dissertation, Gottfried Wilhelm Leibniz Universität Hannover]. https://doi.org/10.15488/5160
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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.",
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note = "Doctoral thesis",
year = "2019",
doi = "10.15488/5160",
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Download

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AU - Burgermeister, Tobias

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PY - 2019

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N2 - 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.

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