Coulomb crystallization of highly charged ions Lisa Schmöger (Max-Planck-Institut für Kernphysik / Physikalisch-Technische Bundesanstalt) COOL’15 Workshop

Bildreferenzen: (links), Piet O. Schmidt (rechts oben), (rechts unten) Test predicitions of the Standard Model High-Energy Physics (e.g. LHC) high energy Atomic physics (e.g. atomic clocks) high precision Are fundamental constants constant? Are fundamental constants constant? says yes

dimensionless frequency measurement for highest accuracy Why ? atomic calculations  most stringently tested theory q: sensitivity coefficient (relativistic contribution) numerical value of fine structure constant: CODATA 2010 Search for alpha variation astrophysical investigations:  Webb et al., Phys. Rev. Lett. 107, (2011)  Berengut et al., Europhys. Lett. 97, (2012) What happens if  changes ?

? Laboratory experiment: compare 2 accurate frequency references with different sensitivities to over long period of time Laboratory experiment: compare 2 accurate frequency references with different sensitivities to over long period of time numerical value of fine structure constant: CODATA 2010 Search for alpha variation

Hg + /Al + Atomic clock comparison T. Rosenband et al., Science 319 (2008) strong α dependence weak α dependence  Need tighter limits on alpha variation  Need factor 100 improvement to test Australian dipole

Where to find two orders of magnitude?

Highly charged ions for novel optical clocks and the search for alpha variation remove several e - low polarizabilities: low susceptibility to external fields for low systematic error strong relativistic effects: enhanced sensitivity to α-dot forbidden transitions in optical regime (e.g. level crossings): high f/∆f for atomic clock with level accuracy transitions with different large (!) q values of opposite sign: two frequency references with one ion q: sensitivity coefficient (relativistic contribution)

10 HCI Theory proposals: HCIs for novel optical clocks and the search for alpha variation Highly charged ions for atomic clocks, quantum information, and search for α variation, M.S. Safronova et al., Phys. Rev. Lett. 113, A. Derevianko et al., Phys. Rev. Lett. 109, (2012) J.C. Berengut at al., Phys. Rev. Lett. 109, (2012) Electron-Hole Transitions in Multiply Charged Ions for Precision Laser Spectroscopy and Searching for Variations in α, J.C. Berengut et al., Phys. Rev. Lett. 106, (2011) J.C. Berengut et al., Phys. Rev. Lett. 105, (2010) V. I. Yudin et al., Phys. Rev. Lett. 113, (2014) V.A. Dzuba et al., Phys. Rev. A. 86, (2012) Ir 17+ V.A. Dzuba et al., Phys. Rev. A. 91, (2015) 2015

Highly charged ions for novel optical clocks and the search for alpha variation Objective: ultra-precise laser spectroscopy with HCI Prerequisite: HCI need to be cold and strongly localized

e - -beam Ar Ar 13+ (Electron Beam Ion Trap) EBIT – production of HCI But: MK! trap electrodes e - collector e - gun

Laser spectroscopy of HCIs Fluorescence laser spectroscopy in an EBIT on 2 P 3/2 – 2 P 1/2 M1 transitions in Ar 13+ and Fe 13+ in combination with evaporative cooling K. Schnorr et al., Astrophys. J. 776, 121 (2013) V. Mäckel et al., PRL 107, (2011) T HCI ~ 10 5 K  Δf Doppler ~ 20 GHz (natural linewidth: ~ 10 Hz) Fe 13+ Limited by Doppler linewidth  different cooling method (and ion trap)

e - -beam Ar Ar 13+ EBIT – source for HCI pulsed ion 2 Hz E HCI ~ 1keV/Q ΔE HCI ~ 20eV/Q Ar 13+

From ion source To Paul trap ( ) mm PDT1PDT2 Deceleration and Precooling of ion pulses V PDT2 > V PDT1

Retrapping HCI in a cryogenic linear Paul trap Electrostatic mirrors for HCI ping-pong 1 st 2 nd

Be atoms PI laser cooling laser Sympathetic cooling of HCI: MK to mK produce laser cooled Be + Coulomb crystal in linear Paul trap inject, store and sympathetically cool & crystallize HCIs (Ar 13+ ) imaging lens trap electrodes cryogenic shields Science 347, 6227 (2015) ~1mm

T HCI ?

Sympathetic cooling of HCI – MK to mK T Be+ < 35 mK T Ar13+ < 235 mK (~2µeV/Q)

Mixed-species crystals  Ion strings Use limits to Mathieu stability in a-q parameter space  expel Be +, keep Ar 13+ M. Drewsen and A. Broner, Harmonic linear Paul trap: Stability diagram and effective potentials, PRA 62, (2000)

RMS spot size on camera Sympathetic cooling of HCI – MK to mK S. Knünz et al., Phys. Rev. A. 85, (2012)

Q HCI ?

Sympathetic cooling of HCI: Ar X+ Comparison of theoretical and experimental Be + ion positions

exposure time: 5s video: 7 fps trapping time: ~ 4 min 1mm 300 µm 20 µm Sympathetic cooling of HCI – Configurations Single ion stage: prerequisite for quantum logic spectroscopy P.O. Schmidt et al., Science 309, 749 (2005)

Summary – Versatile preparation technique

Motional control over trapped HCI enables:  High-precision optical laser spectroscopy (e.g. of 2 P 3/2 - 2 P 1/2 M1 transition in Ar 13+ at 441nm)  Quantum metrology: Ultimate accuracy using quantum logic readout at PTB  novel clock at level accuracy  test α-dot at /year  Highest-resolution VUV and x-ray spectroscopy of HCIs  …….

 Experiment\MPIK José Crespo López-Urrutia Stefanie Feuchtenbeiner Peter Micke Baptist Piest Lisa Schmöger Maria Schwarz Oscar Versolato Alexander Windberger Thomas Baumann  Experiment\PTB Piet Schmidt Joachim Ullrich Matthias Kohnen Tobias Leopold The team & acknowledgements  Experiment\Aarhus University Michael Drewsen Anders Hansen  Simulation\Marseille University Jofre Pedregosa-Gutierrez