Probing QED in strong fields via the magnetic moment of highly charged ions. Sven Sturm May 25 th, 2016

Transcription

1 Probing QED in strong fields via the magnetic moment of highly charged ions Sven Sturm May 25 th, 2016

2 Quantum ElectroDynamics (QED) Quantum Electrodynamics (QED is tested and proven in the weak field limit But what about extreme conditions? Non-linear QED processes? Photon-photon interaction Richard P. Feynman Lorentz symmetry violation? Standard Model Extension (Kostelecky)? Combine strongest fields and highest precision!

3 QED of Bound States Few or single electron systems are calculable to very high accuracy in QED series solution

4 The g-factor of a bound electron B e - g 2(1 abreit a loop anuclearsize a2 1 loop recoil a...) Results allow determination of fundamental constants (m e, α) [Z. Harman et al., 2016]

5 QED of Bound States Few or single electron systems are calculable to very high accuracy in QED series solution Low field strength High to ultra-high field strength Extract fundamental constants (electron mass, ) The Standard Model in extreme conditions

6 Measurement Principle Measurement of the Larmor frequency in a well-known magnetic field: L g 2 e m e B B e - Measurement of the free cyclotron frequency to determine the magnetic field: B q c m ion ion B g L qion me 2 2 m e c ion q m ion ion m e e has to be determined Measured by independent precision experiments

7 Experimental Requirements Requirements of the experiment: Extremely homogeneous magnetic field (3.7 T) Single, cold ion Long storage times (months) Perfect vacuum Experimental conditions Cryogenic temperatures (4.2K) Vacuum better than mbar less than 20 gas atoms in the trap volume! The worst part about the ion trap is the cold and the loneliness [P. Evers, Wundersame Welt der Atomis]

8 Our measurement tool - the Penning trap B Three independent eigenmotions Reduced cyclotron frequency: Magnetron drift frequency: ~2π 27 MHz ~ 2π 9 khz Axial frequency: ~ 2π 700 khz Free cyclotron frequency c z (Brown-Gabrielse invariance theorem)

9 Oscillating ion induces image charges in trap electrodes Eigenfrequency Detection

10 Eigenfrequency Detection A Oscillating ion induces image charges in trap electrodes Tank circuit with high impedance R p = 50 MΩ Q = 3200

11 Eigenfrequency Detection A Oscillating ion induces image charges in trap electrodes Tank circuit with high impedance R p = 50 MΩ Q = 3200 Cryogenic ultra lownoise amplifier e n = 400pV/ Hz i n 10fA/ Hz

12 Eigenfrequency Detection A Oscillating ion induces image charges in trap electrodes Tank circuit with high impedance R p = 50 MΩ Q = 3200 Cryogenic ultra lownoise amplifier e n = 400pV/ Hz i n 10fA/ Hz Fast Fourier Transformation to obtain the frequency information

13 Eigenfrequency Detection A Ion is resistively cooled until it reaches thermal equilibrium with the tank circuit Oscillating ion induces image charges in trap electrodes Tank circuit with high impedance R p = 50 MΩ Q = 3200 Cryogenic ultra lownoise amplifier e n = 400pV/ Hz i n 10fA/ Hz Fast Fourier Transformation to obtain the frequency information

14 Eigenfrequency Detection A 25 Signal strength (dbv rms ) Ion is resistively cooled until it reaches thermal equilibrium with the tank circuit Oscillating ion induces image charges in trap electrodes Tank circuit with high impedance R p = 50 MΩ Q = 3200 Frequency khz (Hz) Cryogenic ultra lownoise amplifier e n = 400pV/ Hz i n 10fA/ Hz Fast Fourier Transformation to obtain the frequency information

15 Ultra Precise Detection Method: PnA Phase-sensitive detection technique allows coherent detection of the modified cyclotron frequency ν + rapid measurement time ( ~ 5s instead of ~ 3min) reduction of impact of B-field fluctuations small radial kinetic energies during phase evolution smaller magnetic and relativistic shifts [S.Sturm et al., PRL 107 (2011)]

16 Spin-State Detection Probe Zeeman transition with millimeter waves Detect spin quantum state with continuous Stern-Gerlach effect Magnetic inhomogeneity maps spin-state onto axial frequency Ferromagnetic ring produces a magnetic bottle # Measurement (20s) Axial frequency -411 khz (Hz) 0,6 0,5 0,4 0,3 0,2 0,1 0,0-0,1-0,2 240 mhz

17 ~14 cm 7 mm Triple Penning trap system Precision trap Very homogeneous magnetic field Measurement of the frequency ratio Γ Analysis trap Magnetic inhomogeneity (B 2 10mT/mm 2 ) Detection of spin direction Creation trap In-trap ion creation of highly-charged ions Miniature EBIT/S

18 ~14 cm 7 mm Triple Penning trap system Precision trap Very homogeneous magnetic field Measurement of the frequency ratio Γ Analysis trap Magnetic inhomogeneity (B 2 10mT/mm 2 ) Detection of spin direction

19 Cryogenic temperatures (4.2K) Vacuum better than mbar less than 20 gas atoms in the trap volume Experimental setup

20 Measurement cycle PT AT

21 Measurement cycle PT 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

22 Measurement cycle PT 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

23 Measurement cycle L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Frequency khz (Hz) z 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

24 Measurement cycle L L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Frequency khz (Hz) z 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

25 Measurement cycle L L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Signal strength (dbv rms ) Frequency khz (Hz) Frequency khz (Hz) z 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

26 Measurement cycle L L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Signal strength (dbv rms ) Frequency khz (Hz) Frequency khz (Hz) z + + = 2 c 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

27 Measurement cycle L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Signal strength (dbv rms ) Frequency khz (Hz) Frequency khz (Hz) z + + = 2 c 0.5 AT: Detection of spin orientation AT Fractional axial frequency difference (Hz) Measurement number

28 Measurement cycle L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Signal strength (dbv rms ) Frequency khz (Hz) Frequency khz (Hz) z + + = 2 c 0.5 AT: Detection of spin orientation 0.5 AT Fractional axial frequency difference (Hz) Measurement number Measurement number Fractional axial frequency difference (Hz)

29 Measurement cycle L PT: Measurement of frequency ratio c 24 PT Signal strength (dbv rms ) Signal strength (dbv rms ) Frequency khz (Hz) Frequency khz (Hz) z + + = 2 c 0.5 AT: Detection of spin orientation 0.5 AT Fractional axial frequency difference (Hz) Measurement number Compare spin state Measurement number Fractional axial frequency difference (Hz)

30 Many repetitions for random frequencies g-factor resonance g-factor Resonance Γ 0 is extracted from fit g-factor is calculated g 2 q e m m e Ion

31 g-factor Resonance Many repetitions for random frequencies g-factor resonance our measurement 10-2 Γ 0 is extracted from fit 10-3 a 1loop g-factor is calculated Relative contribution g 2 q e m m e Ion 10 g -6 exp = (5)(3)(8) 10 g -7 theo = (17) 10-8 [S. Sturm et al., PRL 107, 2 (2011)] 10 g -9 exp = (8)(6) 10 g -10 two-loop QED theo = (17) Error dominated by uncertainty of electron mass a Breit a 2loop a (Z)4 2loop a VP a recoil a (Z)2 2loop Uncalculated higher orders a Nuclear Size Theoretical 6 value 8 by: [S. Sturm et al., PRL 107, 2 (2011)] [Z. Hamann, J. Zatorski, Nuclear C. Pachucki charge et al. 2011] Theoretical value by: [Z. Harman, J. Zatorski, C.H. Keitel, C. Pachucki et al. 2011]

32 Lithiumlike ions: Other systems Probe relativistic 3 electron dynamics Specifically address nuclear contributions [A. Wagner et al., PRL 110, (2013)] Interelectronic interaction

33 Lithiumlike ions: Other systems Probe relativistic 3 electron dynamics Specifically address nuclear contributions Interelectronic interaction [A. Wagner et al., PRL 110, (2013)]

34 Isotopic effect in g( 40 Ca 17+ ) - g( 48 Ca 17+ ) Basically identical electron configuration Strong cancellation of theory uncertainties Significantly improved theoretical results (V. Shabaev)

35 Isotopic effect in g( 40 Ca 17+ ) - g( 48 Ca 17+ ) Calcium isotopes 40 Ca and 48 Ca have almost identical nuclear radius (Δr=0.5(9) m) Nuclear size effect cancels to large extent different mass (Δm 8u) Very sensitive to (fully relativisitic) nuclear recoil Ionic masses to high precision from SHIPTRAP Test physics beyond the Furry picture in strong field! [Nature Comm. 7, 2016]

36 Direct measurement of the electron mass Cyclotron frequency in a Penning trap electron c e 2 m e B 100GHz ion c q 2 M B 30MHz m e e q ion c electron c M

37 Direct measurement of the electron mass Cyclotron frequency in a Penning trap electron c e 2 m e B 100GHz ion c q 2 M B 30MHz Limitation: Relativistic mass increase due to low mass of the electron c c E c 2 m c relat. e m e e q ion c electron c M

38 Direct measurement of the electron mass relative uncertainty of me 10-5 direct approach year CODATA Indirect measurement via B / Gärtner: v c via particle loss (first direct) Gräff: v c via ToF Van Dyck: v c via image currents (first non-destructive) Wineland: v c via laser fluorescence + v L + g theo (first bound electron) Gabrielse: v c via image currents Farnham: v c via image currents (first single ion) Häffner: v c /v L of 12 C 5+ + g theo Verdú: v c /v L of 16 O 7+ + g theo Hori: antiprotonic helium

39 The electron s mass Electron mass from ultra-high precision g-factor of hydrogenlike carbon: Theory (Pachucki et. al) x g mge 2 2 theo L cq ione mq c L ion ion m e e ion Experiment

40 The electron s mass Electron mass from ultra-high precision g-factor of hydrogenlike carbon: m e g 2 theo c L e q ion m ion m e = (16) u Order of magnitude improved value! Nature 506, , 2014

41 The proton s mass Compare cyclotron frequencies of a single proton and a 12 C 6+ ion m p f ( f 12 C ( p) 6 c m12 6 c ) e q C Proton mass in atomic mass units u

42 The proton s mass A specially tailored trap design

43 The proton s mass A specially tailored trap design Simultaneous measurement cancels magnetic field fluctuations We aim for δm/m<10-11

44 ALPHATRAP: Exploring the highest fields Schwinger-Limit Nonlinear contributions become increasingly important at high nuclear charge Z What happens if Zα 1?

45 ALPHATRAP: Exploring the highest fields Schwinger-Limit Access via MPIK HD-EBIT and HITRAP (José Crespo) (Experiments at GSI in preparation) Nonlinear contributions become increasingly important at high nuclear charge Z What happens if Zα 1?

46 ALPHATRAP: Exploring the highest fields 10 0 Contribution Relativistic QED g Breit = (Zα)2 3 New and independent access to finestructure constant α! Nuclear charge Z ALPHATRAP: Next-generation, online-coupled g-factor experiment for highly-charged ions

47 ALPHATRAP: Routes towards α and the ultimate test of QED g Breit = (Zα)2 3 Specific difference of charge-states cancels nuclear effects: g' g2 p g1 s Very precise theory, but Experimental precision has to be improved (δg ~ 10-13!) State-of-the-art experimental precision, Strong requirements to improve theory!

48 ALPHATRAP: Exploring the highest fields Goals: Probe QED in strongest fields Physics beyond the Furry picture Extract nuclear structure information Determine fundamental constants Probe relativistic electron dynamics with lithium- and boronlike ions

49 ALPHATRAP: Mini-EBIT permanent magnet EBIT Xenon charge breeding - extraction in leaky mode - electron energy ~2keV - electron current 4.3mA - gas pressure: 2.2x10-9 mbar Sikler lens Wien filter MCP with phosphor screen Xe charge-state distribution IE(26+) 860eV IE(27+) 1.5keV

50 ALPHATRAP: Exploring the highest fields

51 ALPHATRAP: Exploring the highest fields

52 ALPHATRAP: Current status LN2 cryostat LHe cryostat / trap section Trap

53 Summary Most stringent test of bound-state QED Most stringent test of relativistic electron dynamics in strong fields Isotopic effect in 40 Ca/ 48 Ca is sensitive test to physics beyond the Furry picture Electron mass improvement by an order of magnitude Next generation experiment ALPHATRAP Towards ultra-strong fields All charge-states available from HD-EBIT

54 Special thanks to Abteilung für gespeicherte und gekühlte Ionen at MPIK, Heidelberg MATS group within QUANTUM at the Institut für Physik, Mainz Atomic Physics Division at GSI Helmholtzzentrum, Darmstadt Funding Adv. Grant MEFUCO (#290870) Helmholtz Alliance (HA216) Experimental support: Theory support: F. Köhler, F. Heiße, R. Wolf, A. Weigl, I. Arapoglou, A. Egl., W. Quint, G. Werth, K. Blaum Z. Harman, C.H. Keitel, J. Zatorski, V. Shabaev, K. Pachucki

55 55

56 Probing QED in extreme fields Quantum Electrodynamics (QED) is tested and proven: g-2 of the free electron Lamb shift in hydrogenlike Uranium Combine strongest fields and highest precision!