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T. Inoue, 1 T. Nanao,1 M. Tsuchiya, 1 H. Hayashi, 1 T. Furukawa, 1 A. Yoshimi, 2

Workshop on Fundamental Physics Using Atoms 7 - 9 August 2010, Osaka. Search for an electric dipole moment in 129 Xe atom using a nuclear spin oscillator. T. Inoue, 1 T. Nanao,1 M. Tsuchiya, 1 H. Hayashi, 1 T. Furukawa, 1 A. Yoshimi, 2

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T. Inoue, 1 T. Nanao,1 M. Tsuchiya, 1 H. Hayashi, 1 T. Furukawa, 1 A. Yoshimi, 2

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  1. Workshop on Fundamental Physics Using Atoms 7 - 9 August 2010, Osaka Search for an electric dipole moment in 129Xe atom using a nuclear spin oscillator T. Inoue,1 T. Nanao,1 M. Tsuchiya,1 H. Hayashi,1 T. Furukawa,1 A. Yoshimi,2 M. Uchida,1 H. Ueno,2 Y. Matsuo,2 T. Fukuyama,3 and K. Asahi1 1Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan 2RIKEN, 2-1 Horosawa, Wako-shi, Saitama 351-0198, Japan 3 Ritsumeikan University, Nojihigashi, Kusatsu, Shiga 525-8577, Japan OUTLINE: 1. Introduction 2. "Optically coupled" spin oscillator 3. Present status 4. Summary

  2. + + + - - - + + + - - - 1. Introduction Electric Dipole Moment (Permanent) Electric Dipole Moment Electric Dipole Moment (EDM) d s +q + = a d≡ qa - -q Eext = 0 or, or,

  3. Electric dipole moment (EDM) s d s + + d + + + + - - - - - - spin EDM : : s →-s d →d time reversal d ≠ 0 ： Violation of T ⇒ Violation of CP (CPT theorem) ● The violation of CP is implemented in the Standard Model (SM), but ... ● CP violation in SM (K-M mechanism) is not sufficient to explain the matter-antimatter asymmetry observed in the universe. Thus, ... ● An extra CP-violation is required.

  4. Electric dipole moment (EDM) s d s + + d + + + + - - - - - - spin EDM : : s →-s d →d time reversal d ≠ 0 ： Violation of T ⇒ Violation of CP (CPT theorem) Sites of EDM searches • neutron dN • paramagnetic atoms (Tl, Fr, Cs, ...) de • diamagnetic atoms (129Xe, 199Hg, Rn, Ra, ...) S • molecules (TlF, YbF, PbO, ThO, ...) de • charged particles (d, m, ...) dN, dm ⇒ Probing different facetｓof anticipated new physics

  5. Electric dipole moment (EDM) s d s + + d M. Pospelov and A. Ritz, Annals of Phys. 318, (2005) 119-169 + + + + - - - - - - spin EDM : : s →-s d →d Tl, Fr, Cs… 129Xe, 199Hg, Rn, Ra… time reversal d ≠ 0 ： Violation of T ⇒ Violation of CP (CPT theorem) Schiff moment EDM in 129Xe atoms •stable particle •macroscopic number of particles •EDM generated by a nuclear Schiff moment •P,T-violating NN interaction

  6. EDMd q q + = d EDMd q = Dx = d/q How does the EDM appear in a diamagnetic atom? Point nucleus in an atom Nucleus with a finite size Nucleus Electrostatic F(r) due to a cloud of atomic electrons q -q Atomic electrons feel a non-trivial charge distribution unside the nucleus. Atomic electrons do not "know" whether the nucleus has EDM.

  7. Electron cloud Nucleus

  8. Electron cloud Nucleus datom≠0 Nontrivial charge distribution in the nucleus generates an EDM in atom: Schiff moment d(129Xe) = 3.8×10-5 fm-2·S(129Xe) d(199Hg) = -2.8×10-4 fm-2·S(199Hg) [Ginges & Flambaum, Phys. Rep. 397 (04) 63]

  9. What generates a Schiff moment ? --- (In language of nuclear physics) CP-violating components of the NN interaction generate S. ●Case of 199Hg with SkO' effective interaction, [J.H. de Jesus and J. Engel, Ann. Phys. 318 (05) 119] ●Case of 129Xe Flambaum, Khriplovich, Sushkov, 1985 Dzuba, Flambaum, Porsev, 2009 Yoshinaga's group, consideration fro shell model in progress.

  10. d(129Xe) < 4.1×10-27ecm Rosenberry and Chupp, PRL86 (2001) 22 d(199Hg) < 3.1×10-29ecm Grifith et al., PRL 102 (2009) 101601 Neutron EDM predicted values d = 10-27e·cm E = 10 kV/cm Dn = 10 nHz （ Dw  1°/day） Standard Model (dn = 10-(31-33) ) [Pendlebury and Hinds, NIM A 440 (00) 471]

  11. Detection of an EDM E // B E // -B B B E E the difference 　⇒　signal of an EDM s s Energy shift upon an E-field reversal Energy levels for a spin 1/2 (for a case of m > 0, d > 0) Shift in a precession frequency Desires long precession times => Spin maser

  12. Free precession ‘Spin maser’ state Transverse spin Transverse spin Time Time Key issue for a high-sensitivity EDM detection: ― Realization of a long precession time

  13. [T.E. Chupp et al, Phys. Rev. Lett.72 (94) 2363] [M.A. Rosenberry and T.E. Chupp, Phys. Re. Lett. 86 (2001) 22] Spin maser ●129Xe polarization vector P = I/I ● Static field B0 = (Bx, By, B0) ●P follows the Bloch equations: or, B relaxation term Pumping term

  14. [T.E. Chupp et al, Phys. Rev. Lett.72 (94) 2363] [M.A. Rosenberry and T.E. Chupp, Phys. Re. Lett. 86 (2001) 22] Spin maser ● If a capacitor C is connected to form a resonating circuit, the coil produces a transverse B field, B(t), B

  15. Taking (1) + i (2)and setting The steady state solutions 　・Trivial solution: 　・Non-trivial solution:

  16. Spin oscillator ● Now we devise the transverse part of the B field, B(t), to follow P B(t) B(t) Spin detection

  17. steady oscillation transient Maser oscillation

  18. Setup for the maser experiment Solenoid coil (static field) ・B0 = 30.6 mG (I = 7.354 mA) magnetic shield (4-layer) ・permalloy Si photodiode ・Bandwidth: 0 ～ 500 kHz l/4 plate Heater spin precession signal Pumping laser ・l = 794.76 nm (Rb D1line) ・Dl = 3 nm ・Power ~ 11 W PEM 129Xe gas cell 129Xe : 230 torr N2 : 100 torr Rb : ~ 1 mg Pyrex glass SurfaSil coating Probe laser ・DFB laser ・l = 794.76 nm (Rb D1line) ・Dl = 8.4×10-6 nm ・Power : 15 mW 18 mm

  19. Rb Rb 129Xe 129Xe N2 Xe Rb 129Xe Rb 129Xe Rb N2 Spin polarization of 129Xe and Optical detection of nuclear precession Spin polarization of 129Xe Detection of precession of 129Xe Optical pumping Rb atom Transverse polarization transfer : 129Xe nuclei → Rb atoms (re-pol) D1 line： 794.7 nm B0 Probe laser beam : single mode diode laser (794.7nm) Xe Rb Xe Xe Circular polarization (modulated by PEM) Detector Spin-echange in Rb-Xe After half-period precession Xe Xe Rb Xe

  20. Spin oscillator ①129Xe nuclear spin polarization by optical pumping Pumping and relaxation effect B0 Feedback circuit ② Optical detection of the spin precession n0 Feedback torque Lock-in detection P(t) P(t) B(t) “Optically coupled” spin maser with a feedback field generated according to optical spin detection Static magnetic field : B0mG Feedback system Probe light ③Generation of a feedback field Feedback coil Photo diode Pumping light precession signal ④Self-sustained spin precession Realization of maser oscillation at very low fields ( mG) Suppression of drifts in the B0 field => Suppression of drifts in n

  21. Magnetic Shield Heater Mirror Fiber-coupled Laser Probe Laser (DL-DFB) Glan Laser prism PEM Array-type Laser Ookayama Campus, Tokyo Inst. of Technology, Tokyo, Japan

  22. Signal [V] Time [s] Frequency determination B0 Lock-in Amplifier output PhotoDiode detector VX VY Xe 35.1Hz Rb Xe Xe Xe Lock-in amplifier 35Hz Function Generator νrefReference frequency ν0Xe precession freq. Result ・Lock-in amplifier output signals fitting function Phase [rad] ・Phase Δa = 9.310-9 Hz freq. precision Time [rad]

  23. [From; T. Inoue et. al., Poster, INPC2010]

  24. Long term stability of the oscillation frequency Frequency Solenoid current time (0 - 30,000 sec) Frequency 129Xe cell temperature

  25. At present, there are a number of concerns: ・Do imperfections in spin detection, signal processing, feedback field generation, ... affect the oscillation frequency? ・Does the presence of Rb atoms interfere the measurement? ・Does the low frequency operation really help in reducing the spourious drifts? These should be tested and investigated by using actual setup.

  26. Expt. Simulation Frequency pulling effect ●A phase deviation Df in the feedback field will induce a shift in the Maser frequency.

  27. Ongoing developments ・Pumping laser ・Double cell ・B0 stabilization ・Simulation study ・Magnetometry [T. Inoue, ... ] φ [Inoue et al.] [Tsuchiya et al.] [M. Tsuchiya, ... ] NMOR magnetometry [T. Furukawa, ... ] [Furukawa et al.] [Hayashi et al.] [H. Hayashi, T. Furukawa, ... ] B|| Paraffin coating 0.6 z 0.4 [T. Nanao, A. Yoshimi, ... ] 0.2 0.0 -0.2 [Nanao, Yoshimi et al.] fitting -0.4 -0.6 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 z In paraffin coated cell

  28. HV application system preparation [T. Inoue, ... ] Picoammeter High voltage Transparent electrode Protection circuit for picoammeter R : 1 MW R : 1 MW Cell Leakage current test preliminary Xe cell for an E-field a trial piece - Cubic cell size : 20 mm × 20 mm × 20 mm Pyrex glass (corning 7740) - Transparent electrode : ITO (Indium Tin Oxide) transmittance ~ 85%@795 nm size : 30 mm × 30 mm × 1.75 mm resistance : ~ 30 W C : 2 nF spark Leakage current [nA] A HV HV [kV]

  29. HV application system preparation Next step… - Smaller cell (10 mm gap) - Using 2 high voltage source (positive and negative) - N2 or SF6 gas atmosphere - Low pass filter for reducing the noise output by HV source …

  30. Magnetic field stabilization Current fluctuation 300nA, ~40ppm In magnetic shield: ~28 mG magnetic field with a solenoid coil & stabilized current source (applying 7mA current) 1.5mHz ~40ppm Current instability = magnetic field fluctuation → Frequency instability Fluctuation of Xe precession Frequency instability : mostly due to current fluctuation

  31. Previous current source • stabilized current source • drift : <50nA in a few hour • slow & large drift (up to 1uA) • in long-term operation Current source ~ 7 mA

  32. A new current supply system Feedback of current fluctuation (measured with Dig. Voltmeter) to correct the current drift Current source 1 ~ 6.5 mA Two current sources are installed in parallel for setting resolutions Current source 2 ~ 0.5 mA Using an accurate voltmeter with a reference resistance to obtain high resolutions Digital Voltmeter Feedback

  33. Performance of new current source Stability improved ! Fluctuation:<1/200 This fluctuation is mainly due to the accuracy of current measurement. Conclusion: The current stability is improved successfully (x200) with the feedback of current fluctuation. stability – limited by accuracies of current measurement Future : More accurate measurement of current drift → More stabilized magnetic field for EDM measurement

  34. Future Spherical cell ・good symmetry ・Reflection ⇒ lowering of the pumping efficiency? Cubic cells Taper Amplifier Optical Isolator DFB Laser Diode Introduction of a narrow-line laser (TA DFB, TOPTICA) Power : ~ 430 mW line width : ~ 4MHz (cf. pressure broadening ~ 7.5 GHz) 20 times enhanced pumping efficiency => suppression of amplitude fluctuations

  35. Setup ポンピング レーザー Double cell for 129Xe gas 偏極度測定部分 ポンピング部分 (偏極生成部分) pick-up coil 保持磁場用 コイル 129Xe : 227torr N2 : 133torr Rb パイレックスガラス SurfaSil コーティング 偏極度測定装置 RF coil

  36. Cell test bench pick-up coil Current problems pick-up coil 固定されていない →測定の再現性が低い, 調整が困難, 振動に弱い pick-up coil が振動 →NMRシグナルと同じ周波数であるRFシグナルを検出 →ノイズの発生 material：PEEK New system ・ Incorporation of anti-vibration system ・ Orthogonality adjustment mechanism for pick-up coil High-precision, high-reproducibility assesment system for 129Xe cells trim coil

  37. Simulation study of the frequency precision ν：測定周波数 φfluc：位相ゆらぎ φperi：周期変動 A : シグナル振幅 ε : 振幅のゆらぎ Signal [V] Phasedeviation[rad] Phase deviation[rad] Time [s] Time [s] Time [s] Incorporate the phase and amplitude fluctuations of the maser signal.

  38. Simulation results Experiment sA , sf ,sf per≈ the experiment sAsf≈ the experiment, sf peri ≈ 0.5 sA , sf ,sf per≈ 1/10 Simulation Frequency Precision[Hz] 2.3ｘ10-10 Hz 6.7ｘ10-11 Hz 2.0x10-11 Hz ←1.9x10-30ecm (E=10kV) Time [s] 1day 12days Half a day Should reach a 10-10 Hz precision in a 2-day measurement !!

  39. B +E z w+t y x Magnetometry；　Non-linear MagnetoOptical Rotation (NMOR) on Rb atoms Field precision required in EDM measurements Resonant optical rotation in Rb vapor (NMOR; Nonlinear Magneto-Optical Rotation) Linear polarized light @ E=10kV/cm k Rb atom Required frequency precision B Field D. Budker et al.,PRA 62 (2000) 043403. Optical Pumping magnetometers (Rb, Cs)：　30 pG/ √Hz Magnetometry with SQUID： 2-3 fT/ √Hz = 20-30 pG /√Hz @ He temp. 50-60 fT/ √Hz = 0.5 – 0.6 nG/ /√Hz @ liq. N2 temp. High-Q resonator → 0.08 fT/√Hz = 0.8 pG /√Hz Advantages: Narrow width Operation at room temp. low field

  40. NMOR 原理 直線偏向光と原子の相互作用 • 直線偏向光 により原子は alignment状態になる　 • 　　　　　　→　原子集団の蒸気は linear dichroism を持つ • 原子 alignment が磁場の周りを歳差運動する　 • 　　　　　　→　dichroism の軸が回転する • 回転する dichroic 軸を持つ原子と入射直線偏光ビームとの • 　　 相互作用で偏光面が回転する (F’=0) s - s+ gmB mF = -1 mF = 0 mF = +1 0.6 (F=1) 右・左円偏向成分に対する原子系屈折率 基底状態 0.4 0.2 0.0 -0.2 -0.4 直線偏向面の回転 Rotation angle (mrad) -0.6 -10 -5 0 5 10

  41. Summary ●Precession of 129Xe spins is maintained for unlimitedly long times, by application of a feedback fieldgenerated fromoptically detected spins. The merit of this optically coupled spin maser as a scheme for the EDM search is the capability of operation at very low B0 fields, as mG or below. ● Frequency precision presently reached is 9.3 nHz, which corresponds to an EDM sensitivity of 910-28 ecm (E=10kV/cm). ● There still remain drifts/fluctuations in the maser frequency that are correlated with ambient temperature and noises. Improvements and further developments are under progress. ・Reinforcement of 129Xe polarization by introducing a narrow-line high-power TA-DFB pumping laser ・Stabilization of solenoid current ・Stabilization of cell temperature by means of a heat transfer fluid GALDEN ・Cell development for the E-field application ・Magnetometry with NMOR, aiming at detection of d(129Xe) in a 10-28 -10-29ecm regime.

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