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Ultrahigh precision observation of nuclear spin precession and application to EDM measurement

Ultrahigh precision observation of nuclear spin precession and application to EDM measurement. T. Inoue, T. Furukawa, H. Hayashi, M. Tsuchiya, T. Nanao, A. Yoshimi A , M. Uchida, and K. Asahi Department of Physics, Tokyo Institute of Technology A Nishina Center, RIKEN.

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Ultrahigh precision observation of nuclear spin precession and application to EDM measurement

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  1. Ultrahigh precision observation of nuclear spin precession and application to EDM measurement T. Inoue, T. Furukawa, H. Hayashi, M. Tsuchiya, T. Nanao, A. YoshimiA, M. Uchida, and K. Asahi Department of Physics, Tokyo Institute of Technology ANishina Center, RIKEN International Workshop onPhysics of Nuclei at Extremes @TITech, Japan 26. Jan. 2010

  2. Outline • ◇Electric Dipole Moment (EDM) • - EDM and T - violation • - Status of EDM experiment • ◇129Xe “active” nuclear spin maser • Character of 129Xe atom • - Experimental apparatus • - Optical pumping and optical detection • - Nuclear spin maser • ◇Experimental result • - Present status of spin maser • ◇On going R & D • Feedback system of solenoid current • - Improvement of the optical pumping efficiency • ◇Summary and future

  3. s -s + + d d + + + + - - - - - - Time reversal ： T Electric Dipole Moment (EDM) Time Spin EDM : : : t→ -t s →-s d →d Classical representation Vector (parallel to spin) ：T-violation CP-violation (by CPT theorem) EDM : sensitive to the CP-violation beyond SM Non-zero EDM associated with spin is direct evidence of time reversal symmetry violation Standard Model (SM): Predicted neutron EDM isabout 105 smaller than the present experimental upper limits. Beyond SM: Detectable EDM Search for EDM Test of the SM and beyond SM (no SM background)

  4. Historical Limits of EDMs d(129Xe) < 4.1×10-27ecm Rosenberry and Chupp, PRL86 (2001) 22 d(199Hg) < 3.1×10-29ecm W.C. Griffith et al., PRL 102 (2009) 101601 Neutron EDM predicted values |dn| < 2.9 × 10-26ecm C.A. Baker et al., PRL. 97(2006)131801 Pendlebury and Hinds, NIM A 440 (00) 471 Standard Model (dn = 10-31 ~ 10-33ecm)

  5. Hamiltonian: E parallel to B E anti-parallel to B Principles of EDM measurement B E B -E s s Energy level of spin1/2 system (if m > 0, d > 0) Energy shift according to E direction Small shift of spin precession frequency EDM measurement => measurement of the tiny shift in the frequency of the spin precession

  6. ●Stable particle High density：1018～ 1019 atom/cm3 @ room temperature ●High polarization and Long relaxation time Polarization : P (129Xe) ~ 40 % (AFP-NMR) Relaxation time :Tw～ 20 min ●Spin maser technique ☐ Accumulation of free spin precession AFP-NMR signal + + · · · · + Transverse spin Character of 129Xe atom Free spin precession Steady oscillation (maser state)  Continuous spin precession (maser oscillation) Transverse spin spin maser Search for d(129Xe) using “Active” nuclear spin maser Goal : d(129Xe) ~ 10-29ecm

  7. Magnetic shield (4 layers) ・Permalloy (Fe-Ni alloy) Solenoid colil (for static field) ・B0 = 30.6 mG (I0= 7.354 mA) Si photo diode ・Band width: 0 ～ 500 kHz ・NEP : 8  10-13 W/Hz 129Xe Rb Circularly polarizing plate Rb N2 129Xe 129Xe nuclear spin polarization Typical 129Xe free spin precession signal Optical detection of nuclear spin precession Heater Nuclear spin polrization through spin exchange interaction with Rb atom Experimental apparatus Polarization transfer from 129Xe nuclei to Rb atom (re-pol.) Rb atomic polarization by optical pumping 129Xe Rb 129Xe nuclear spin precession : detected by using probe light (Rb D line) 129Xe Rb N2 Pumping laser ・Wavelength : 794.76 nm (Rb D1 line) ・Dl = 3 nm ・Output : 11 W B0 Probe light ：794.76 nm circular polarization (modulated by PEM) Transmission intensity Max Transmission intensity Min PEM Rb 129Xe 129Xe 129Xe 129Xe gas cell Rb atomic energy level B0 129Xe : 230 torr N2 : 100 torr Rb : ~ 1 mg Pyrex glass SurfaSil coated Selective excitation by circularly polarized light 129Xe Probe laser ・DFB laser ・Wavelength : 794.76 nm (Rb D1 line) ・Dl= 8.4×10-6 nm ・Output : 15 mW After half period of 129Xe spin precession 18 mm Rb Rb 129Xe 129Xe 129Xe

  8. PEM Pumping laser Feedback coil Probe laser Heater - tube 129Xe gas cell Magnetic shield (4 layers) f : 400 mm, L = 1600 mm for the outermost layer Cell Box Solenoid coil f : 254 mm, L = 940 mm Heater

  9. ①129Xe nuclear spin polarization by optical pumping method Relaxation ,pumping effect B0 Feedback circuit Static magnetic field : B0mG Feedback system ②Nuclear spin precession detection by optical detection method n0 Probe light Nuclear spin maser Feedback torque Lock-in detection ③Feedback signal generation by feedback system P(t) Feedback coil Photo diode P(t) ④Sustained Spin precession through the coupling between nuclear spin and feedback field B(t) Pumping light Spin precession signal “Active” nuclear spin maser Production of the feedback field by using optical detection method Yoshimi et al., (2002) Maser operation in low static field (~ mG) Small field fluctuation=> Small frequency fluctuation

  10. Maser signal Feedback system on B0 = 30.6 mG => n0 = 36.0 Hz Start-up enhancement Steady oscillation

  11. Frequency fluctuation Frequency precision ~ 1.5 mHz <=> ~ 40 ppm Frequency precision (present status) Solenoid current fluctuation ~ 350 nA <=> ~ 40 ppm t > 30,000sec -> precision getting worse ⇔ drift of the solenoid current

  12. We are now ○ installing the fiber laser for the optical pumping laser. 129Xe gas cell Convex lens ○ constructing the feedback system for the solenoid current. ○ constructing the electric field application system. ○ developing the highly sensitive magnetometer. Linear polarized light k Rb atom B ○ simulating the frequency analysis.

  13. We are now ○ installing the fiber laser for the optical pumping laser. 129Xe gas cell Convex lens ○ constructing the feedback system for the solenoid current. ○ constructing the electric field application system. ○ developing the highly sensitive magnetometer. Linear polarized light k Rb atom B ○ simulating the frequency analysis.

  14. Stabilization of the solenoid current Present situation Solenoid coil for static field ~ 1 W High precision Current monitor Stable current source1 : ~ 7 mA current: ~ 7 mA voltage: ~ 10 mV Current fluctuation: ~ 500 nA/day Stability: ~ 70 ppm

  15. Stabilization of the solenoid current @1 mA range ±12 ppm ± 2nA/day = 14 nA/day stability Solenoid coil for static field ~ 1 W Goal : ~ 5 ppm(~ 35 nA) Stability ADC inc, model 6161 @10mA range ±7 ppm ± 20 nA/day = 70 nA/day stability Voltage reading precision: 1ppm/day Reference resistor precision: 1ppm/day 1 W KETHLEY 2002 High precision Voltage monitor, 8.5 digit Stable current source1 : ~ 7 mA www 100:1resistance splitting = 140 pA/daystability www 10 W 1 kW Stable current source2 : ~ 1 mA www Feedback

  16. Frequency fluctuation Frequency precision ~ 1.5 mHz <=> ~ 40 ppm Improvement of Frequency precision Solenoid current fluctuation ~ 350 nA <=> ~ 40 ppm Dn ~ 0.1 nHz for one week measurement  Dd ~ 10-29ecm (E = 10 kV/cm) Suppression of solenoid current drift

  17. Introduction of fiber laser Introduction of the fiber laser for the optical pumping • present pumping laser : array type high output laser <- it is difficult to irradiate the cell uniformly. • introduction of the fiber laser - uniform irradiation to the cell - increase of the unit area intensity : 0.6 W/cm2 ⇒ 0.9 W/cm2 =>improvements of Rb polarization and 129Xe nuclear polarization : suppression of maser amplitude fluctuation

  18. PEM convex lens (f = 200 mm) Circularly polarizing plate Introduction of fiber laser Gran laser prism convex lens (f = 70 mm) 129Xe gas cell 129Xe : 230 torr N2 : 100 torr Rb : ~ 1 mg Pyrex glass SurfaSil coated 18 mm Fiber laser Magnetic shield (4 layers) ・Permalloy (Fe-Ni alloy) Solenoid colil (for static field) ・B0 = 30.6 mG (I0= 7.354 mA) Si photo diode ・Band width: 0 ～ 500 kHz ・NEP : 8  10-13 W/Hz Circularly polarizing plate Heater Prism PEM Pumping laser (Fiber laser) ・Wavelength : 794.76 nm (Rb D1 line) ・Dl = 3 nm ・Output : 11 W Probe laser ・DFB laser ・Wavelength : 794.76 nm (Rb D1 line) ・Dl= 8.4×10-6 nm ・Output : 15 mW 129Xe gas cell Convex lens

  19. Maser amplitude (steady state) Fiber laser Amplitude [V] Amplitude [V] Maser amplitude : Fiber laser v.s. Array laser counts time [sec] Array laser Amplitude [V] Amplitude [V] counts time [sec] Spherical cell ・good symmetry ・scattering of pumping light <= decrease of optical pumping efficiency? Cubic cell preparation ~ 4 times deterioration

  20. Summary and Future ○ The frequency precision of 9.3 nHz (measurement time 30,000 sec) was obtained by operating the “active” spin maser. ○ The feedback system of the solenoid current is being constructed in order to suppress the current drift. ○ The fiber laser as the pumping laser was installed. However the fluctuation of the maser amplitude did not improve. The cubic cells are now being prepared. Further improvements and developments are now in progress. : ◎ Constriction of the electric field application system ◎ Development of the highly sensitive magnetometer based on NMOR; Nonlinear Magneto-Optical Rotation. ◎ Frequency analysis simulation => search for d(129Xe) in the level of 10-29 ecm

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