Low-frequency nuclear spin maser and search for atomic EDM of 129 Xe

1. Low-frequency nuclear spin maser and search for atomic EDM of 129Xe A. Yoshimi RIKEN Collaborator : K. Asahi (Professor, Tokyo Inst. of Tech./RIKEN) S. Emori (Tokyo Inst. of Tech.) S. Oshima (Tokyo Inst. of Tech.) SPIN2004 2004/10/11-16 Trieste, ITALY

2. s s +++ +++ --- --- Time reversal Time: t -t Spin: s -s EDM: dd d 0 T-violation CP-violation Electric Dipole Moment Non-zero EDM associated with spin Direct evidence of violation of time reversal symmetry CPT theorem Standard Model (SM) : Predicted EDM is about 105 smaller than the present experimental upper limit Beyond the SM : Detectable EDM Detection of non-zero EDM CP-violation beyond the standard model

3. Recent EDM experiment of diamagnetic atoms • Vold et. al., • Phys. Rev. Lett. 52 (1984) 2229. 1987. Lamoreaux et. al., Phys. Rev. Lett. 59 (1987) 2275. Repetition of FID measurement …. 300 – 500 sec/1run 2001. Romalis et. al., Phys. Rev. Lett. 86 (2001) 2505. 2001. Rosenberry and Chupp, Phys. Rev. Lett. 86 (2001) 22. Operation of continuous spin maser One shot measurement … 2000 sec.

4. EDM theory Standard model Supersymmetric model (O.P. Sushkov et al., JETP 60 (1984) 873) Energy scale of superpartner (T. Falk et al., hep-ph/9904393) M=500GeV M=250GeV Present experimental upper limit Upper limit of CP-violating complex phases in Supersymmetric model T. Falk et al., hep-ph/9904393

5. Rb 129Xe Project of atomic EDM experiment of 129Xe at RIKEN-TIT Large polarization of Xe nucleus Spin exchange with optical pumped Rb atom Nuclear polarization O(10) % @ 100 torr (1018 /cc) Continuous nuclear spin maser Free Induction Decay Continuous oscillation Rapid decrease of frequency precision Spin maser at low frequency • Low static field experiment(  mG ) •  Small field fluctuation • Use of the ultra high sensitive magnetometer

6. pump Feedback system Zeeman level Spin MASER Transverse magnetic field - synchronism with spin precession - Phase : perpendicular to the transverse polarization Amplitude : proportional to the transverse polarization Relaxation, pumping B0 Polarization’s growing (pumping effect) Feedback torque T2 relaxation Polarization vector : M Polarization Feedback torque Feedback field : Bfb Population inversion Feedback EM-field synchronism with emitted photon

7. Optical-detection-feedback spin maser NMR-based spin maser 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)

8. Experimental apparatus Magnetic shield (3 layers ) Parmalloy 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

10. 0.4 0.0 Signal (V) -0.4 88940 88950 88960 0 10 20 302910 302920 ( 84 hours) Time (s) Typical maser oscillation signal B0 = 28.3 mG , nref = 33.20 Hz, feedback gain: 18 mG/0.1mV 0.2 0.0 Signal (mV) -0.2 0 1000 2000 3000 4000 Time (s) Steady state oscillation 0.1 0.0 Feedback system ON -0.1 3000 3010 3020 Measured frequency:

11. f (rad) 10000 0 0 10000 5000 Frequency characteristics Fourie spectrum ( 1 hr. run ) Precession angle Low-frequency spin maser ( n = 33.5 Hz ) t (sec) n = 277.20844  0.00096 mHz dn = 0.96 mHz s(n) t-3/2 100 Conventional spin maser ( n = 3.56 kHz ) 10 Frequency precision (mHz) 1 0.1 10 100 1000 Time (s)

12. Linear polarized light k Alkali vapor Faraday rotation B 1×104 rad/G, 4×10-12 G/Hz (B < 0.1G) On-going developments 1 – magnetometer - Fluctuation of magnetic field  Main source of frequency noise in spin maser operation Neutron EDM experiment….. Hg atomic magnetometer Xe EDM experiment @ Michigan Gr. ….. 3He co-magnetometer Atomic magnetometer with Rb using magneto-optical rotation D. Budker et al., PRA 62 (2000) 043403. calibration run

13. On-going developments 2 – magnetic shield - Construction of 4-layer shield l = 1600 mm, R= f 400 mm Estimated shielding factor Transverse: S ≈106 Longitudinal: S ≈104 Measured residual field z (cm) transverse Field (mG) longitudinal Shielding factor : S ≈104

14. 1000 100 10 1 0.1 0.01 Precision ( mHz ) Estimation of experimental EDM-sensitivity Estimation of frequency precision 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 ) 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) Time (s) 1 10 100 1000 10000 Conceptual setup (E=10kV/cm) Probe light (Magnetometer) 

15. Summary and Future • Construction of the nuclear spin maser with an artificial feedback system, and operated it at low frequency 33 Hz ( under B = 28 mG ). • Frequency precision of 1 contiguous measurement presently reaches to 1 mHz. (without magnetometer/free-running) • Construction of 4-layer magnetic shield. • Installing the Rb magnetometer with magneto-optical rotation. Aiming atsearch for the atomic electric dipole moment in Xe ; d(Xe) = 10-29 10-30 ecm.