Nuclear spin maser for 129 Xe atomic EDM measurement - present status -

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1 Nuclear spin maser for atomic EDM measurement - present status -. Inoue a), K. Asahi a), S. Kagami a), N. Hatakeyama a), M. Uchida a), and A. Yoshimi b) a) Department of Physics, okyo Institute of echnology b) Nishina Center, RIKEN ADVANCED SUDIES INSIUE "SYMMERIES AND SPIN" (SPIN-PRAHA-8)

2 Electric Dipole Moment (EDM) and time reversal Non-zero EDM associated with spin is direct evidence of time reversal symmetry violation s s ime reversal : --- Vector (parallel to spin) d = dsˆ time spin EDM : : : t -t s -s d d Classical representation e d = rρ particle d :-violation CP-violation (by CP theorem) 3 ( r) d r EDM : sensitive to the CP violation beyond SM Standard Model (SM) : Predicted neutron EDM is by five orders magnitude smaller than the present experimental upper limits. Beyond SM : Predicted neutron EDMs are detectable in the current experimental condition. Search for EDM est of the SM and beyond SM

3 C.A. Baker et al., PRL. 97 (6) d n < e cm EDM of what? Neutron EDM predicted values Neutron Direct measurement of nucleon EDM Unstable particle : τ 1/ = s Low density : ρ 1-1 UCN/cm -3 Diamagnetic Atom (, 199 Hg, Ra, Rn ) Stable particle High density : ρ cm -3 Schiff shielding 6 d( ) < ecm (1) Rosenberry and Chupp, PRL. 86 (1) d( 199 Hg) < ecm (1) M.V. Romalis et al., PRL. 86 (1) 55 Standard Model (d n = 1-31 ~1-33 ecm) In an external electrostatic potential, the atomic system consisting of non-relativistic, point-like, charged particles doesn t show an energy shift due to EDM. not complete EDM induced by the Schiff moment :S of the nucleus d 17 S ( ) =.38 1 e cm 3 e fm V. A. Dzuba et al., PRA 66, 1111 ()

4 Why atom? (1)Stable particle high density : ~ atom/cm room temperature AFP-NMR signal ()High polarization and long relaxation time polarization : P( ) ~ 4% 18 torr (n ~ atom/cm 3 ) 1 ~ min. (3)A spin maser technique is applicable. Free precession Sustained oscillation (maser oscillation) Spin maser δν 1/ m δν 3/ m We aim at an experimental search for d( ), by using Active Spin Maser. Goal; d( ) = 1-8 ~ 1-9 ecm

5 Principles of experiment Energy shift according to E direction Hamiltonian:H = µ B d E E parallel to B H = µ B de E anti-parallel to B H = µ B + de 1 m = B E = B E // B B E // B Small shift of spin precession frequency B = E = h ν hν + hν + µ B + de = h ν ( E // B) µ B de = h ν ( E // B) EDM measurement measurement of difference between frequency shifts ν + ν = 4dE h 1 m = ν + B E s ν B E s Long measurement time of spin precession spin maser

6 Conventional (passive) spin maser M.G. Richards, JPB 1 (1988) 665: 3 He spin maser. Chupp et al., PRL 7 (1994) 363: spin maser Nuclear spin maser:strong coupling between nuclear spins and a feedback coil Sustained spin precession Static magnetic field : B ~ G Relaxation, pumping B Feed back field : B FB Feedback coil L Induced current I npq Pumping light γ Capacitor C 1 B = LC Feedback torque Polarization : P Feedback field : B FB Operation condition 1 1 = γ ηµ hi[ n] P Q > τ RD 1 Radiation dumping time transverse relaxation time Large Q-factor : operation frequency ~ khz = strong static field (~G) Large fluctuation in the static field Large fluctuation in the precession frequency

7 Active spin maser A. Yoshimi et al., PLA 34 () 13. Static magnetic field : B (3) Probe light Feedback coil mg (1) () Generation of active feedback signal Lock-in detection (1)Detection of spin precession without pick-up coil (optical detection of spin precession) ()Generation of feedback field by using detected signal (orthogonal to the spin) Pumping light Photo diode Spin precession signal (3) Sustained spin precession by active feedback field (maser operation) Maser operation in low static field (~ mg) Small field fluctuation small frequency fluctuation Improvement of experimental setup Magnetic shield : 3 layers => 4 layers A current source for static magnetic fields: stability 1-4 => 1-6

8 hree key ingredients for active spin maser (a) Polarization of nuclear spin (b) Optical detection of nuclear spin precession (c) Generation of active feedback field Static magnetic field : B mg Probe light Generation of active feedback signal Feedback coil Pumping light Photo diode Lock-in detection Spin precession signal

9 Polarization of nuclear spins Atomic polarization of atoms by using optical pumping technique Selective excitation by circularly polarized light,,n m s = -1/ m s = + 1/ 5P 1/ 5P 1/ σ + : nm / 3 1/ 3 5S 1/ m s = -1/ m s = + 1/ 5S 1/ Nuclear polarization by spin exchange interaction with atom N I S wo body collision with Formation of van der Waals molecule with Spin exchange rate se P P se + Γsd = γ γ Spin relaxation rate N

10 Optical detection of nuclear spin precession ransverse polarization transfer : nuclei atoms (re-polarization) nuclear spin precession Optical detection by probe light ( D1 line : nm) Probe light λ:794.7nm Circular pol. ransmission Max After half-period spin precession ransmission Min Intensity transverse pol : P I 1 + P Cross σ 1 P section : Experiments Circular polarization of probe laser is modulated with a photo-elastic modulator (PEM). Suppression of transverse polarization Phase-sensitive detection by using a Lock-in Amplifier Signal [mv] transverse pol : Cross σ section : Intensity P I 1 P 1 + P ypical free precession signal ime [s]

11 Generation of active feedback field Probe laser light Attenuator Feedback coil Photo diode V cos( πν PEMt + δ PEM ) cos(πν t + δ ) PEM frequency:5 khz, spin precession frequency: ~ 36. Hz V ( t fd ) ref : ν PEM = V Y ( t) 5 khz Lock-in Amplifier V sig ( t) cos(πν t + δ ) (1)Probe light detection with Photo Diode Operation circuit V V V X ( t) ref1 t) cos ( πν t + ) ( δ ref t) sin r ( πν t + ) ( δ r r r Lock-in Amplifier ref : ν = 36.1 Hz ν r Function Generator V ref1 :φ = º V ref :φ = 9º ()Low noise signals by Lock-in detection (3)Phase is delayed by 9º to the detected signal in an operation circuit V Generation of feedback signal fd ( t) = V X ( t) V sin(πν t + δ ) ref ( t) V Y ( t) V ref1 ( t) V V Noise filtering by a low-pass filter (BW~.5Hz) X Y ( t) cos ( t) sin ν { π ( ν r ν ) t + ( δ r δ )} { π ( ν ν ) t + ( δ δ )} r r ν.1hz r (4)he signal is applied to a feedback coil for maser operation

12 Experimental apparatus Si photo diode Freq. band width : ~ 5 khz NEP : W/Hz Magnetic shield (4 layers ) Parmalloy (Fe-Ni alloy) B Solenoid coil (for static field) B = 3.6 mg (I = ma) Circularly polarizing plate Heater 7 o C gas cell PEM Pumping laser wavelength : nm ( D1 Line) λ = 3 nm output : 11 W 18 mm : 18 torr ~ cm -3 N : 1torr ~ cm -3 : ~ 1 mg Pyrex glass cell (Corning 756) SurfaSil coated Probe laser DFB Laser wave length : nm ( D1 Line) λ = nm output : 15 mw

13 Magnetic shield (4 layers) φ : 4 mm, L = 16 mm for the outermost layer Solenoid coil φ : 54 mm, L = 94 mm Feedback coil Pumping laser PEM gas cell ube for a heater Probe laser

14 Feedback system on Result : Maser Operation B = 3.6 mg ν = 36. Hz Signal [mv] Star-up enhancement ime [s] Steady oscillation Signal [mv] Signal [mv] ime [s] ime [s]

15 Result on the frequency analysis Precession phase Phase [rad] A linear χ fitting was performed on the phase data for 3 s frequency precision : 9.3 nhz EDM precision : ecm (E = 1 kv/cm) ime [s] ν ref ν = ±. 93 Hz Frequency precision [Hz] Measured frequency precision ν 1 m ime [s] ν 3/ m he frequency precision is not proportional to m -3/ ( m :measurement time) simply. he frequency precision is getting worse beyond 3s. some noises in addition to white noise

16 Correlation with the static field current source Frequency fluctuation static field fluctuation current source fluctuation Average static field current (1 s) Average detected frequency (1 s) Current [ma] na B ~ 8 ng ν ~.1 mhz frequency [mhz]. mhz ime [s] ime [s] I I 6 6 mean = 1 1 ν = 3 1 ν he stability of current source should not be the main source of the frequency fluctuation.

17 Correlation with environmental magnetic fields Static field fluctuation environmental magnetic fields fluctuation in the experimental room Residual magnetic field in the shield : about.7 mg shielding factor : 1 3 but original :1 4 Secular change of magnetic shield Average environmental field (1 s) magnetic field [mg] Residual field (static field direction) position [cm] recent introduction Average detected frequency (1 s) Magnetic field [mg]. mg B ~ ng (shielding factor : 1 3 ) ν ~.4 mhz frequency [mhz]. mhz ext B = 5 1 B ime [s] 6 ime [s] ν = 3 1 ν 6 he fluctuation in the environmental magnetic field was the dominant noise source.

18 Frequency stability for a long term measurement Average detected frequency (1 s) Average environmental field (1 s) Frequency [mhz] ν 1.5 mhz B 1.3 µg ν mhz B 1.7 µg Magnetic field [mg] ime [s] Average static field current (1 s) ime [s] Average maser amplitude (1 s) Current [ma] I 35 na B 1.4 µg Amplitude [mv] ime [s] ime [s] Frequency change from 4 s to 6 s current shift Sudden jump of frequency no correlation data accidental magnetization of the shield? he long term stabilization for the current source and the demagnetization of the shield

19 Summary he active spin maser has been successfully operated in an upgraded experimental apparatus. he frequency precision was 9.3 nhz for 3s measurement time. It corresponds to the EDM precision of ecm, when E = 1 kv/cm. Due to the secular degradation of the magnetic shield, the fluctuation in the environmental magnetic field is considered the main noise source. For a long term stability of the maser frequency, a long term stabilization of current source and the demagnetization of the shield are necessary.

20 Future prospects he introduction of new current source tolerant of the low frequency and thermal noises. he demagnetization of the magnetic shield for one day measurement (864 s) ν = d( 9.3 nhz ) = e 3/ cm ( E = 1 kv/cm) And HV application tests and reduction of leakage current Incorporation of a magnetometer ; An optical magnetometer by using the technique of nonlinear magneto-optical rotation with frequency-modulated light (FM NMOR) -EDM precision : 1-8 ~ 1-9 ecm = 1.9 nhz

21 signal [mv] Frequency precision in the previous setup V x Lock-in Amplifier outputs V Y ime [s] 1 V φ( t) = tan V ( t) ( t) Measured frequency precision X Y Phase (rad) 1 Precession phase 5 1 ime [s] ν = ±.96 mhz δν =.96 µhz Frequency precision (µhz) σ(ν) τ -3/ ime [s] Current [ma] Averaged static field current (stability:1-4 ) ime [s] δi ~.1 µa for time scale of 1 s (δb ~.8 µg, δν ( ) ~ 1 mhz)

22 Result : leakage current test (Preliminary) Leakage current [na] Leakage current for two materials Preliminary Corning 774 Corning High voltage [kv] 6 ILeak = 1nA BLeak =.6 ng 7 nhz d = 7 1 ecm = ( E 1 kv/cm)

23 Optical magnetometer Fluctuation of magnetic field Main source of frequency noise in spin maser operation d 1 8 atom ecm δν 1nHz E =1 kv/cm δb 1pG Neutron EDM experiment.. Hg atomic magnetometer EDM Michigan Gr... 3 He co-magnetometer Atomic magnetometer with using magneto-optical rotation k Linear polarized light B D. Budker et al., PRA 6 () Alkali vapor Faraday rotation rotation angle [mrad] 18 Sensitivity δb = 4 [ µg] magnetic field [G]

24 Analysis about the frequency Part of Lock-in Amp outputs in steady state V X V Y Signal [mv] ime [s] V V X Y wo Lock-in Amp outputs (V X,V Y ) ( t) = V ( t) = V = V L.A. L.A. L.A. cos[π ( ν cos π ( ν sin[π ( ν ref ref ref ν ) t + ( φ φ )] π ν ) t + ( φref φ) ν ) t + ( φ φ )] ref ref φ( t) = tan 1 = π ( ν V V ref Y X ( t) ( t) ν ) t + ( φ ref φ ) he frequency is decided by the phase data

25 emperature dependence of the current source Averaged static field current (1s) Current [ma] 3 na ime [day] Averaged experimental room temperature (1s) emperature [ºC] 1 ºC ime [day]

26 Deviations for some observables Current Maser frequency : ν Environmental field (Shielding factor:1 3 )

27 Other data Average detected frequency (1 s) Average maser amplitude (1 s) Frequency [mhz] Amplitude [mv] ime [s] ime [s] Average cell temperature (1 s) Average fluorescence (1 s) temperature [ºC] PD output [mv] ime [s] ime [s]

28 Frequency precision Normally, spin precession is subject to decoherence (or, transverse relaxation) due to field inhomogeneity, spin-spin interaction,.. ransverse spin Free precession : δν ime 1/ m While... Accuracy of frequency determination: σ ν 1 Fourier width m 1 ( m : measurement time) 3/ m 1 [# of data points ] 1/ m ransverse spin Steady oscillation : δν ime 3/ m

29 Optical detection of nuclear spin precession Re-polarization rate Development of transverse-polarization ime [sec] dp dt ransverse-polarization transfer nuclei atoms (re-polarization) = γ repol se ν / P 1 repol γ se Γ sd P ~ 1kHz repol γ se :re-polarization rate Γ :re-polarization relaxation rate sd exp ν = 36. Hz Probe light λ:794.7nm Circular pol. ransmission Max After half-period spin precession ransmission Min Intensity transverse pol : P I 1 + P Cross σ 1 P section : transverse pol : P Cross σ 1 + P section : I Intensity 1 P

30 Maser equation Modified Bloch equation dpx Px = γ ( P B) x dt dp dt dp dt γb x y z = γ ( P B) = γ ( P B) Py = β P, y z γb P y y Pz 1 feedback gain + Px = β P ( P P ) rotation frame: ω = γb spin exchange z γ se dp dt dp dt Z 1 / P P eq 1 = PZ = β P P = P τ x = 1 / P P = β 1 + RD + γ P y se β P P P Z, P eq Z = P β ransverse polarization β =. rad s β =.5 rad s -1-1 β =.15 rad s -1 Longitudinal polarization β =. rad s β =.5 rad s -1-1 β =.15 rad s -1 ime [s] ime [s]

31 Result : Measurement Static magnetic field : B =3.6 mg ν =36. Hz ν = ±. Hz (χ fitting) ν =. µhz = 81.8 ±.1 s Signal [mv] ime [s]

32 Atomic EDM induced by finite nuclear size effect Wˆ 3 = 4πS δ Schiff moment S = e rr ρ 1 nucleus 3 Z ϕ P,-odd interaction between nucleons G η G ρ () ( ) = σ ρ r = η A σ U m m U ( ) ρ = ψψ + η Schiff d atom d S d S 3 () r d r d r ρ() r nucleus ( R) E = ϕ I Schiff ) D M M ϕ ) Schiff =, D = e ri E E M p G m p ρ U ( ) ( ) M p ( ψσψ ) P,-odd nuclear density 5 - ( ) = fm S( ) 8 3 ( = η efm ( Hg) =.8 1 fm S( Hg) ( Hg) = η efm d () r 3 r d J.S.M. Ginges, V.V. Flambaum, Phys. Rep. 397 (4) 63 V. A. Dzuba et al., PRA 66, 1111 () atom nucleus E I d atom 6 ( ) = η ecm d ( Hg) = η ecm

33 , 199 Hg EDMs induced by Schiff moment J.S.M. Ginges, V.V. Flambaum, Phys. Rep. 397 (4) 63 he largest contribution to the constant η: G η gg π mπ g π where g and are the constant of the strong and -odd π meson-nucleon interaction: ( gniγ n + g ) + ( + )( ) pp π gpiγ n g pn π + L 5 5 π π Neutron EDM induced through virtual creation of π meson d n = e m p gg π 4 π π d n ~ 1 ecm η ln g = M ~ m ρ M m g π π ~ 77 MeV CP-even CP-odd from M. Pospelov, A. Ritz, Ann. Phys. 318 (5) 119. d d π n g p n g π 4 ( ) ~ dn ( Hg) ~ dn γ

34 Schiff shielding In an external electrostatic potential, the atomic system consisted of non-relativistic, point-like, charged particles doesn t show an energy shift due to EDM, even if the components of atomic system have the EDMs. Diamagnetic atom e - Nucleus e - E ext Diamagnetic atom Nucleus Ze + E int Ze + apply an electric field : E ext e - e - e - e - e - e - Electron cloud Electron cloud E eff = Eext + Eint = he electron cloud moves to cancel an external electric field he effective electric field is zero.