Search for an Atomic EDM with The 17th International Spin Physics Symposium (SPIN 2006) , October 2-7, 2006, Kyoto Search for an Atomic EDM with Optical-Coupling Nuclear Spin Oscillator M. Uchida, A. Yoshimi,* T. Inoue, S. Oshima, and K. Asahi, Dept. Physics, Tokyo Inst. Technology *Nishina Center, RIKEN

­ ­ ­ ­ ­ ­ + + + + + + ●Electric dipole moment (EDM) of a particle T t ⇒ -t + + + + d ­ ­ ­ ­ ­ ­ d  d ∙ (s / s )

­ ­ ­ ­ + + + + ●Electric dipole moment (EDM) of a particle T t ⇒ -t + ­ ­ ­ d  d ∙ (s / s )

- ­ ­ ­ + + + + ●Electric dipole moment (EDM) of a particle T t ⇒ -t + ­ ­ ­ d  d ∙ (s / s ) d  -d ∙ (s / s )

 - ­ ­ ­ + + + + ●Electric dipole moment (EDM) of a particle d  d ∙ (s / s ) d  -d ∙ (s / s )

= Thus… an EDM violates T, hence CP (by CPT) Predicted sizes of EDMs, from CP within SM unmeasurably small! -- 10-6 smaller than the present limits. ⇒ Observation of a non-zero EDM Clear evidence for new physics = SM EDM = 0

Neutron EDM |dn| < 2.9×10-26 ecm Milliweak Weinberg Multi-Higgs Sept. 29, 2006 SUSY Cosmology Standard Model (dn = 10-(31-33) )

Schiff’s theorem -- a shielding effect EDM of what ? “There is a complete shielding for a system of ・non-relativistic ・point-like, ・charged electric dipoles in an external 　electromagnetic potential.” where EDM of what ? --- a neutral particle (otherwise, E field readily sweeps it away!) Neutron EDM Quark EDM or Chromo EDM EDM of “bare” nucleon Neutron EDM ・direct measurement of the nucleon EDM but... ・unstable particle ― t1/2 = 614.8 s ・density extremely low ― r  1-100 UCN/cm3 ・needs accelerator or reactor Neutron EDM Diamagnetic atom ….. 129Xe, 199Hg, Ra, Rn T-violating interaction in nuclei Nucleon EDM Atomic EDM is generated mainly from EDM in nucleus Atomic EDM ・stable particle ・macroscopic density ― r  1010-20 atoms/cm3 ・setup can be "table-top" but... ・Schiff's shielding Nuclear Schiff moment Schiff moment Atomic EDM Orbital electron: j=0 Paramagnetic atom …. 133Cs, Fr, Rb, Tl Electron EDM Atomic EDM is generated mainly from electron EDM Enhancement Electron EDM Atomic EDM

(P, T- violating p-N couplings) Ways out of the shielding effect in Atomic EDM Ginges & Flambaum, Phys. Rep. 397 (04) 63 (1) Finite nuclear size effect ― nuclear Schiff moment (P, T- violating p-N couplings) nucleus P, T-odd N-N int. E  S datom Nuclear EDM diamagnetic atom (nucleon EDM) Schiff moment S Atomic EDM datom

Schiff moment induced by the P, T-odd N-N interaction Ginges & Flambaum, Phys. Rep. 397 (04) 63. Dzuba, Flambaum, Ginges, Phys. Rev. A 66 (02) 012111. ●Comparisons with dn ・Neutron EDM induced through virtual p- creation (assuming )

―free from Schiff shielding Ways out of the shielding effect in Atomic EDM Oshima-Fujita-Asaga (private comm.) (2) Relativistic effect ― relativistic EDM operator Relativistic EDM Hamiltonian for nucleon small component ―free from Schiff shielding

Thus, we aim at the experimental search for an EDM in diamagnetic atom 129Xe, by using an Optical-coupling Spin Maser. Goal: d(129Xe) search in a 10-(28-29) e cm scale

Xe and Hg 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. Rosenberry and Chupp, Phys. Rev. Lett. 86 (2001) 22. 2001. Romalis et. al., 　　　　Phys. Rev. Lett. 86 (2001) 2505. Operation of continuous spin maser One shot measurement … 2000 sec. 100 s

Detection of EDM x z y B +E w+ t x z y -E w- t B

Three key issues for an EDM detection: (1) Polarization of spins (2) Detection of the spin precession (3) Realization of a long precession time

(1) Polarization of nuclear spin Spin exchange interaction between optically pumped alkali atom and Xe nucleus 5P1/2 5S1/2 m = -1/2 m = +1/2 Rb D1 line (794.7 nm) Rb Xe Xe Xe Xe Rb Circularly polarized laser light for the pumping of Rb atomic spins W. Happer et al., Rev. Mod. Phys. 44 (1972) 169. Spin exchange rate Depolarization rate Rb S NMR signal P0 ~ 60%@1018 /cm3 129Xe I H = AIS + gNS + aKS + gmNBI +   

Xe cell Glass cell f 20 mm Xe 102 torr Rb mg Cleaning　　baking  　Coating  　Rb 　  　Xe　  　confinement Coating agent : SurfaSil 　 　　suppression of the spin relaxation of Xe Glass cell f 20 mm Xe 102 torr Rb mg Spin relaxation：　due to wall collision Non-coating： TW ≈ 3 min. Coated cell： TW ≈ 20 min. @ Xe 100 torr

(2) Detection of the nuclear spin precession (1) Conventional NMR pickup (feasible for B0 ≥ 1 G) B0 (2) Optical detection through a Rb repolarization (B0 < 1 G) next slide

half-period precession Optical detection of 129Xe nuclear precession Transverse-polarization transfer : Rb atom Xe nuclei (re-polarization) Rb Xe g’[Xe] = 7 × 103 /s, Gsd = 0.2 /s 0.3 ms PRb (ms) 0 0.4 0.8 Time constant of spin transfer: 10-4 s Precession frequency of < kHz Probe laser beam : single mode diode laser (794.7nm) After half-period precession Rb Xe Rb Xe Circular polarization (with a PEM modulation)

129Xe free precession signal (FID signal) 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

Self-sustained precession (3) Realization of a long precession time Free precession ●Normally, spin precession is subject to decoherence (or, transverse relaxation) due to field inhomogeneity, spin-spin interaction, ….. While... ●Accuracy of frequency determination: Transverse spin Time (t : measurement time) Spin Maser Self-sustained precession

Spin Maser B relaxation term Pumping term ● 129Xe polarization vector P = S/S ● Static field B0 = (0, 0, B0) ● Oscillating field B = (Bx, By, 0) ● P follows the Bloch equations: or, B relaxation term Pumping term

Spin Maser B(t) B(t) ● Now we devise the B(t) field to follow P M.G. Richards, JPB 21 (1988) 665: 3He spin maser T. Chupp et al., PRL 72 (1994) 2363: 3He-129Xe two-species spin maser ● Now we devise the B(t) field to follow P B(t) B(t)

Spin Maser B(t) B(t) Present work Spin detection ● Now we devise the B(t) field to follow P B(t) B(t) Spin detection

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

Masing mechanism B0 w0 P(t) B(t) Relaxation and pumping effects Torque from B w0 P(t) ● Balancing between the torque produced by B(t) and relaxation and pumping effects ●Only occurs when the spin is polarized oppositely to B0 ---- population inversion ●Only occurs when a > Pz /T2 ---- threshold B(t) pump Feedback system Zeeman level An analogue of LASER

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 Pyrex　spherical 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

Pumping and probing laser system Xe-cell

Optical-coupling Spin Maser (1) Precession signal from the probe light (2) The signal is filtered ( BW ~ 0.8 Hz ) to obtain S/N > 300 (3) Phase is delayed by 90 in an operation circuit. (4) The signal is sent to a feedback coil for maser operation. Detection of precession (33.5 Hz) Noise filtering by a low-pass filter Lock-in amp. Operation circuit Wave generator Modulated signal 　　PEM　Modul. Freq.（50 kHz) 129Xe Larmor Freq.(33.5 Hz) Probe light 4 turns f 20cm f = 0° f = -90° Si photo-diode R = 10 – 50 kW VX VY PSD-signal （0.2 Hz) Feedback signal (33.5 Hz) Feedback field BFB = 1 gT2 Feedback coil 1 mG ( T2=100s) 1V 3.6 mG Pumping light ref. (  33.3 Hz ) ref. (50kHz) (0.2 Hz) Generation of the feedback signal (33.5 Hz)

Maser oscillation signal B0 = 28.3 mG , nref = 33.20 Hz, feedback gain: 18 mG/0.1mV 0.2 Signal (mV) 0.0 -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: 0 10 20 88940 88950 88960 302910 302920 ( 84 hours) 0.0 0.4 -0.4 Signal (V) Time (s)

Various transients depending on the feedback strength Feedback Gain 0 1000 2000 3000 4000 0.0 0.2 -0.2 Signal (mV) Time (s) 4 mG/0.1mV 10 mG/0.1mV 14 mG/0.1mV 28 mG/0.1mV

Frequency shift due to the feedback phase error 33.592 33.588 33.584 33.580 T2 = 6.2 s T2 = 240 s T2 = 14.8 s 33.480 33.484 33.488 33.492 -20 -10 d (deg) ●Ideal feedback field: Frequency (Hz) Effect of a phase error d in the feedback field spin d Feedback field Frequency shift due to the feedback phase error d T2=300 s, d = 0.1º dn = 1 mHz

Frequency characteristics Fourie spectrum ( 1 hr. run ) Frequency precision vs. meas. time Low-frequency spin maser ( n = 33.5 Hz ) s(n)  t -3/2 100 10 Frequency precision (mHz) 1 0.1 Conventional spin maser ( n = 3.56 kHz ) 10 100 1000 Time (s) Current fluctuation in solenoid coil 3.5870 3.5866 3.5862 dB0 ~ 0.8 mG (mA) 0 2000 4000 6000 Time (s)

(1) Incorporation of a low-noise current source for solenoid PSE-1101 Ｔａｋａｓａｇｏ 5nA 200nA Replacement of the reference voltage diode  low-noise battery dI ≈ 200nA dn ≈ 1mHz dI ≈ 5nA dn ≈ 25nHz

(2) Installation of a new 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

Free precession signal 27-Sept-2006 Free precession signal χ2 fitting: f = 36.60605206 +/- 0.00000130 Hz

Fourier spectra with old and new current sources （for 5500s period） Previous system New system Beat freq. (Hz)

Xe cell for an E-field: a trial piece (3) Electric field application Xe cell for an E-field: a trial piece

Electrodes currently under testing are: ・Al (0.1 mm thich) plated on Pyrex glass endcaps (40 mm f x 1 mm t) ・Mesh pattern produced by etching ・Size: 0.2 mm width, 1 mm pitch,　and 0.4 mm width, 2 mm pitch

Expected sensitivity to EDM ● Frequency noise (intrinsic frequency fluctuation in spin maser) Feedback phase error : s [fn] Estimation of frequency precision 1000 100 10 1 0.1 0.01 Precision ( mHz ) dn = 0.7 nHz (S/N=1000) for 5 days run ● Magnetic field fluctuation 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 ) 1 10 100 1000 10000 Time (s) ● Magnetic fluctuation due to collision with Rb atoms interaction with Rb atomic spins (109/cc) P(Rb)  0.01 % ( re-polarization from Xe )  Dn(Xe)  0.2 nHz (dT  0.01˚C)

Summary ● 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) ● Measured fundamental characteristics indicate that this scheme would provide promising means to pursue a serach for EDM in 129Xe atom down to a level of d(129Xe) = 10-29 ecm. ( 0.1 nHz). ● There still remain several things to be done: 　　・ HV application tests and reduction of leakage current 　　・ Incorporation of a magnetometer; Rb co-magnetometer? or 3He co-maser? 　　・ Development of double-cell technique to separate pumping and maser cells 　　・ Establishment of techniques for precision control of maser and cancellation of spurious effects: spin echo technique