Nuclear spin maser at highly stabilized low magnetic field and search for an atomic EDM

1. Nuclear spin maser at highly stabilized low magnetic field and search for an atomic EDM A. Yoshimi RIKEN K. Asahi, T. Inoue, M. Uchida, N. Hatakeyama Dept. Phys., Tokyo Inst. Tech. The 18th International Symposium on Spin Physics (SPIN08), UVa,2008/10/6-11.

2. EDM and physics beyond the standard model Non-zero EDM associated with spin Direct evidence of violation of time reversal symmetry + + + + Time Reversal + + No EDM effect from one loop diagram ­ ­ ­ ­ ­ ­ Time: t -t Spin: s -s EDM: dd E EDM effect from one loop diagram In the standard model…. only possibility is CKM complex phaseδCKM: → predicted EDM is too small to detect (105 smaller than the present experimental upper limit) Beyond the standard model … detectable size of EDM is suggested : more than two CP violating phases W W fL e+iδ e -iδ fL f’ E fL fR

3. EDM search with various species From experimental upper limit of different elements … Neutron EDM Direct detection of neutron Experiment with UCN CP phase in SUSY: qA, qm Phase pattern in M=500GeV case |dn| < 2.9×10-26ecm (C.A. Baker et al., PRL. 97(2006)131801) EDM in diamagnetic atom 129Xe, 199Hg, Ra, Rn Small EDM due to “Schiff shielding” Sensitive to T-violating interaction between nucleons. |dHg| < 2.1×10-28ecm (M.V. Romalis et al., PRL. 86(2001)2505) EDM in paramagnetic atom Cs, Tl, Fr Detection of electron EDM (small) Large enhancement in heavy element T. Falk et al., hep-ph/9904393 |de| < 1.6×10-27ecm (B.C. Regan et al., PRL. 88(2002)071805) Limit the SUSY-particle mass Other Molecule (YbF, PbO), deuteron, …

4. EDM search in diamagnetic atom Optical pumping of Hg atom Optical pumping spin-exchange in Rb-Xe • Vold et. al., PRL 52 (1984) 2229. 1987. Lamoreaux et. al., Phys. Rev. Lett. 59 (1987) 2275. Repetition of FID measurement …. 300 – 500 sec/1run 2001. Rosenberry and Chupp, PRL 86 (2001) 22. 2001. Romalis et. al., Phys. Rev. Lett. 86 (2001) 2505. Operation of continuous spin maser One shot measurement … 2000 sec.

5. Rb 129Xe Free precession ‘Spin maser’ state Transverse spin Transverse spin Time Time About 129Xe Large spin polarization through spin exchange with polarized atom Spin exchange with optical pumped Rb atom P > 10 % for Xe atomic density of 1018 /cm3 Long coherence time of atomic spin No chemical interaction No quadrupole interaction of nucleus ( I=1/2 ) Continuous spin maser technique Optical detection of nuclear spin precession • Low static field experiment(  mG ) •  Small field fluctuation • Use of the ultra high sensitive magnetometer

6. Spin maser with 129Xe at low static field Spin maser with the tuned coil of tank circuit Artificial feedback through the optical spin detection M. Richards et al., J. Phys. B 21 (1988) 665. T. Chupp et al., PRL 72 (1994) 2363. A. Yoshimi et al., PLA 304 (2002) 13. L B0mG B0 Probe laser beam Feedback coil BFB Phase shifter Induced current Lock-in detection InPQ C Photo diode Nuclear spin Pumping laser beam Pumping light Oscillation threshold Operation at low magnetic field Small field fluctuation High-sensitive magnetometer Long intrinsic T2 n> kHz(B0 = 1 G)

7. 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

8. Experimental Setup Magnetic shield (3 layers ) Permalloy Size : l = 100 cm, d = 36, 42, 48 cm Shielding factor : S = 103 Solenoid coil (for static field) B0 = 28.3 mG ( I = 3.58 mA) Pumping LASER Tunable diode laser l = 794.7 nm ( Rb D1 line ), Dl = 3 nm Output: 18 W Si photo diode Freq. band width: 0 – 500 kHz NEP: 810-13 W/Hz Xe gas cell PEM Mod. Freq. 50 kHz Enriched 129Xe : 230 torr Rb : ~ 1 mg Pxe ~ 10 % Heater Tcell = 60 ~ 70 ℃ 18 mm Pyrexspherical grass cell SurfaSil coated Probe LASER Tunable diode laser with external cavity l = 794.7 nm ( Rb D1 line ), Dl = 10-6 nm Output: 15 mW

9. Magnetic shield(4layer) Φ : 400 mm, L = 1600 mm Solenoid coil Φ : 254 mm, L = 940 mm Pumping Laser PEM Feedback coil Probe Laser Heater - tube 129Xe cell

10. Free precession signal of 129Xe Static magnetic field： B0 =28.3 mG (n(Xe)=33.5 Hz) 90°RF pulse（ 33.5 Hz , Dt = 3.0 ms, B1 = 70 mG ) Transverse relaxation：T2 = 350 s　； 0.2 Signal (mV) 0.0 T2 350 s -0.2 0 100 200 300 400 500 600 Time (s) 0.16 Frequency: 0.00 -0.16 100 110 120

11. Maser oscillation signal B0 = 30.6 mG n0 = 36.0 Hz 0.8 0.4 Signal (V) 0.0 -0.4 -0.8 0 20000 40000 60000 80000 Time (s) transient steady-state oscillation 0.8 0.2 0.4 0.1 0.0 0.0 -0.1 -0.4 -0.2 -0.8 0 1000 2000 3000 4000 5000 60000 60020 60040

12. Previous current source 200nA New one 5nA Improvement of field fluctuation Main source frequency fluctuation B0 - field fluctuation Current fluctuation for solenoid Fabrication of new current source Replacement of the reference voltage diode  low-noise IC at low frequency At time scale of 10000 s… dI ≈ 200nA (610-5) dI ≈ 5nA (1.410-6)

13. Frequency precision Measurement by lock-in detection( beat freq.= maser freq.– reference freq.） Two signals (X, Y – compnents) ; their phases differ by π/2. 0.20 (V) 0.00 -0.20 4500 4505 4510 4515 4520 4525 4530 (s) X, Y signals Precession phase φ Phase fluctuation : fobs(t) – ffit(t) (rad) (rad) 0.8 20000 0.4 0.0 10000 -0.4 -0.8 0 0 10000 20000 30000 0 10000 20000 30000 (s) (s)

14. Frequency precision Determination precision of the maser with different measurement time t 10-4 with previous setup 10-5 10-6 Frequency precision (Hz) 0.6 μHz @ 3x104 s 10-7 10-8 10-9 104 105 10 102 103 Measurement time (s)

15. Frequency precision Determination precision of the maser with different measurement time t 10-4 with previous setup 10-5 750 nHz @ 3x104 s 10-6 Frequency precision (Hz) 2 orders improvement 10-7 10-8 with present setup 9 nHz @ 3x104 s 10-9 104 105 10 102 103 Measurement time (s)

16. Long term stability of the maser frequency why δν get worse in t > 30000 s ? why δν -1/2 in t > 1000 s ? Long term drift in solenoid B0 field Frequency fluctuation in 1000s-avaraging Frequency drift of the maser 125 123.3 124 123.2 (mHz) 2mHz drift Now investigating (mHz) 123 123.1 1.5 mHz 122 123.0 100 μHz 0 20000 40000 60000 80000 122.9 (s) 0 10000 20000 30000 (s) 7.3541 1.) drift of solenoid current in 1000 s time scale Drift of solenoid current 7.3540 10 nA ; 40 nG ∼50 μHz 7.3539 (mA) 350 nA ; 1.4 μG ∼1.7 mHz 2.) drift of environmental magnetic field in 1000 s time scale 7.3538 7.3537 100 μG → 100 nG →125μHz 0 20000 40000 60000 80000 (s)

17. Ongoing R&D for EDM experiments Temperature control and current High-sensitive Rb magnetometer Long term drift of room temperature :δT 2.5℃ → drift of solenoid current :δI 500 nA Temperature stabilization of current source 　　　→ 0.1 ℃in 1-day time scale 　　　→　5 nA fluctuation （20 nG） Nonlinear Magneto-Optical effect of Rb atom High sensitive magnetometer D. Budker et al.,PRA 62 (2000) 043403. 7.3530 Solenoid current Linear polarized light (mA) k 500 nA Rb atom 7.3520 Temperature 24 Faraday rotation B ∼2.5℃ (℃) 22 (B < 0.1G) 1×104 rad/G, 4×10-12 G/Hz 20 10-13 G → 0.1 nHz → 10-29 ecm 0 24 48 72 96 120 Time (h)

18. Ongoing R&D for EDM experiments Temperature control Electric field application Stabilization of cell temperature → Polarization, magnetic noise Now testing the fabricate the field plate and cell in which the leakage current is Suppressed. 68.8 Test cell for electric field application Al– electric plate ： 40 mmφ Glass cell(Corning 7740, 7056) ： 20 mm(h) (℃) 0.04 ℃ 68.7 0 5 10 15 20 25 Time (h) Digital feedback control Calculation of feedback field by computer-based device.

19. Summary and Future ●New scheme of spin maser -optical-coupling spin maser- has been constructed, and successfully operated at frequency as low as 33 Hz (under B0 = 28 mG) ● The spin maser has been operating with a stable static field (δB ~ 10nG). ● Frequency precision of the maser has reached 9 nHz, corresponding to an EDM sensitivity of 910-28 ecm (E=10kV/cm). ● Further improvements and developments are now being proceeded: Temperature control of current source and cell, Precise magnetometer, Electric field application, Precise maser feedback system. ● Measured fundamental characteristics indicate that this scheme would provide promising means to pursue a search for EDM in 129Xe atom down to a level of d(129Xe) = 10-29ecm. ( 0.1 nHz). Main frequency noise in EDM experiment 　　・ Sensitivity limit of the magnetometer : 10-13 G → 0.1 nHz → 10-29ecm. 　　・ Magnetic noise of Rb atom in collision : 0.2 nHz → 10-29ecm.

21. EDM in diamagnetic atom Electron angular momentum = 0 Atomic EDM is induced by the nuclear Schiff moment S Sensitive to P,T- odd effect in nucleus Schiff shielding Total EDM effect with E is canceled Schiff moment is induced by P,T-odd nuclear force Eext + Eint = 0 Eext Eint CP-odd pion exchange is dominated by chromo-EDM of quarks

22. Feedback coil Modulated signal PEMModul. Freq.（50 kHz) 129Xe Larmor Freq.(33.5 Hz) Probe light 4 turns f 20cm Pumping light Si photo-diode ref. (50kHz) Lock-in amp. Feedback 磁場 R = 10 – 50 kW 1 PSD-signal （0.2 Hz) BFB = gT2 Lock-in amp. 3.6 mG VY ref. (  33.3 Hz ) 1 mG ( T2=100s) 1V VX f = 0° Feedback signal (33.5 Hz) f = -90° Wave generator Operation circuit Feedback system Producing the feedback field delayed by 90° in phase to precession signal Detection of spin precession Low pass filtering ( fcut~ 0.8 Hz ) Reconfiguration of precession – correlated signal High S/N feedback signal (33.5 Hz) Frequency transformation for low pass filtering (0.2 Hz) Construction of feedback signal (33.5 Hz)

23. 33.592 33.588 33.584 T2 = 6.2 s 33.580 -10 0 -20 d (deg) 33.492 33.488 33.484 T2 = 14.8 s 33.480 -10 0 -20 33.492 33.488 33.484 T2 = 240 s 33.480 -10 0 -20 d (deg) Frequency shift due to the feedback phase error Ideal feedback field: Frequency (Hz) Phase error of feedback field spin d Feedback field Frequency shift due to the feedback phase error d T2=300 s, d = 1º dn = 10 mHz

24. Source of frequency fluctuation 1.) drift of solenoid current in 1000 s time scale 10 nA ; 40 nG ∼50 μHz 2.) drift of environmental magnetic field in 1000 s time scale 100 μG → 100 nG ∼ 125μHz

25. Expected sensitivity for EDM experiment Installation of atomic magnetometer into low frequency spin maser sensitivity : 10-11 10-12 G/Hz  dB 10-13 G ( dn(Xe)  0.1 nHz ) Main source of frequency noise interaction with Rb atomic spins (109/cc) P(Rb)  0.01 % ( re-polarization from Xe )  Dn(Xe) 0.2 nHz (dT 0.01˚C) Conceptual setup Probe light (Magnetometer) (E=10kV/cm) 

26. 1000 100 10 1 0.1 0.01 Precision ( mHz ) Expected sensitivity to EDM ● Frequency noise (intrinsic frequency fluctuation in spin maser) Estimation of frequency precision Feedback phase error :s [fn] dn = 0.7 nHz (S/N=1000) for 5 days run ●Magnetic field fluctuation 1 10 100 1000 10000 Installation of atomic magnetometer into low frequency spin oscillator sensitivity : 10-11 10-12 G/Hz  dB 10-13 G ( dn(Xe)  0.1 nHz ) Time (s) ●Magnetic fluctuation due to collision with Rb atoms interaction with Rb atomic spins P(Rb)  0.01 % ( re-polarization from Xe )  Dn(Xe) 0.2 nHz (dT 0.01˚C)