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

The 17th International Spin Physics Symposium (SPIN 2006) , October 2-7, 2006, Kyoto

●Electric dipole moment (EDM) of a particle

+++

d

d d ∙ (s / s )

T

t ⇒ t

+++

T

t ⇒ t

●Electric dipole moment (EDM) of a particle

+++

d d ∙ (s / s )

+++

T

t ⇒ t

●Electric dipole moment (EDM) of a particle

+++

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

=EDM = 0

SM

Sept. 29, 2006

|dn| < 2.9×1026 ecm

Neutron EDM

Weinberg Multi-Higgs

SUSY

Cosmology

Standard Model(dn = 10(31-33) )

Milliweak

EDM of what ?

Neutron EDM

Diamagnetic atom ….. 129Xe, 199Hg, Ra, Rn

Paramagnetic atom …. 133Cs, Fr, Rb, Tl

Orbital electron: j=0

Nuclear Schiff moment

EDM of “bare” nucleon

Atomic EDM is generated mainly from EDM in nucleus

Atomic EDM is generated mainly from electron EDM

Electron EDM

T-violating interaction in nucleiNucleon EDM

Schiff moment

Atomic EDM

Electron EDM

Enhancement

Atomic EDM

Quark EDM or Chromo EDM

Neutron EDM

--- a neutral particle (otherwise, E field readily sweeps it away!)

Schiff’s theorem -- a shielding effect

“There is a complete shielding for a system of

・ non-relativistic

・ point-like,

・ charged

electric dipoles in an external

electromagnetic potential.”

0H T V V U W

E D

0 where

ii

D d

Neutron EDM

・ direct measurement of the nucleon EDM

but...

・ unstable particle ― 1/2 = 614.8 s

・ density extremely low ― 1-100 UCN/cm3

・ needs accelerator or reactor

Atomic EDM

・ stable particle

・ macroscopic density ― 1010-20 atoms/cm3

・ setup can be "table-top"

but...

・ Schiff's shielding

Ways out of the shielding effect in Atomic EDMGinges & Flambaum, Phys. Rep. 397 (04) 63

(1) Finite nuclear size effect ― nuclear Schiff moment

Schiffatom

0

ˆ0 0 ˆ2 , where iP iP

P P ee

E E

D

d D R

Schiff 4 ( ) S R

diamagnetic atom

datom

E S

nucleus

P, T-odd N-N int.

Nuclear EDM

Schiff moment S

Atomic EDM datom

2 3 2 3

nucleus nucleus

1 5 1( ) d ( ) d

10 3e r r

Z S r r r d r r

p

( )22

A

GW

m

σ r

p

(0)

(0)2 2A

I

G Zd e q t

U Am

(P, T- violating -N couplings)

(nucleon EDM)

Schiff moment induced by the P, T-odd N-N interaction

129 5 -2 129 129 8 3

26

199 4 -2 199 199 8 3

25

( Xe) 3.8 10 fm ( Xe), ( Xe) 1.75 10 fm

6.7 10 cm

( Hg) 2.8 10 fm ( Hg), ( Hg) 1.4 10 fm

3.9 10 cm

d S S e

e

d S S e

e

・ Neutron EDM induced through virtual creation

(assuming )23

n 5 10 cmd e

129 3n

199 3n

( Xe) 1.3 10

( Hg) 8 10

d d

d d

0g g

Ginges & Flambaum, Phys. Rep. 397 (04) 63.Dzuba, Flambaum, Ginges, Phys. Rev. A 66 (02) 012111.

●Comparisons with dn

Ways out of the shielding effect in Atomic EDMOshima-Fujita-Asaga (private comm.)

(2) Relativistic effect ― relativistic EDM operator

Relativistic EDM Hamiltonian for nucleon

(rel) 5EDM

1

0

1 1

1

0where

0

N

i ii

N N

i i ii i

H ge

ge ge

γ E

Σ E Σ E

σΣ

σ

129 3n

199 3n

( Xe) 3.2 10

( Hg) 4.3 10

d d

d d

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 1028-29) e cm scale

Xe and Hg

27(0.7 3.3 0.1) 10 cmd e

cm10)1.13.0( 26 ed

01129

54 S5Xe

1984. Vold et. al., Phys. Rev. Lett. 52 (1984) 2229.

2001. Rosenberry and Chupp,

Phys. Rev. Lett. 86 (2001)

22.

1987. Lamoreaux et. al.,

　　　　　 Phys. Rev. Lett. 59 (1987) 2275.

cm10)5.17.0( 26 ed

28( 1.06 0.49 0.40) 10 cmd e

01199

80 S6Hg

2001. Romalis et. al.,

　　　　 Phys. Rev. Lett. 86 (2001) 2505.

Operation of continuous spin maserOne shot measurement … 2000 sec.

Repetition of FID measurement…. 300 – 500 sec/1run

cm101.2 28 ed

100 s

Detection of EDM

x

z

y

B +E

+t

02 2h B dE 02 2h B dE

4dE

h

x

z

y

E

t

B

281 nH 10 cmd e 10 kV/cmE

(1) Polarization of spins

(2) Detection of the spin precession

(3) Realization of a long precession time

Three key issues for an EDM detection:

(1) Polarization of nuclear spin

Xe

Xe

Xe

Rb

Rb

Xe

Circularly polarized laser light for the pumping of Rb atomic spins

Spin exchange interaction between optically pumped alkali atom and Xe nucleus

tePtP )(Rb

se

seXe

se1)(

Spin exchange rate Depolarization rate

NMR signal

P0 ~ 60%@1018 /cm3

Rb

129Xe

H = AIS + NS + KS + gNBI +

I

S

5P1/2

5S1/2 m = 1/2m = +1/2

m = 1/2m = +1/2

Rb D1 line (794.7 nm)

W. Happer et al., Rev. Mod. Phys. 44 (1972) 169.

Xe cell

Cleaning 　 baking Coating Rb 　 　 Xe 　 　

confinement

Coating agent : SurfaSil

　 　　 suppression of the spin relaxation of Xe

%9.14.69 P

@ Xe 100 torr

Xe 102 torrRb mg

Spin relaxation ：　 due to wall collision

Non-coating ： TW ≈ 3 min.Coated cell ： TW ≈ 20 min.

Glass cell 20 mm

(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

Rb

Xe

Xe XeRbXe

Xe

Xe

Transverse-polarization transfer : Rb atom Xe nuclei (re-polarization)

Optical detection of 129Xe nuclear precession

RbXe

RbsdRbXeseRb PPP

dt

dP RbsdRbXeXe' PPP

’[Xe] = 7 × 103 /s, sd = 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

Circular polarization(with a PEM modulation)

129Xe free precession signal (FID signal)

0 100 200 300 400 500 600Time (s)

0.0

0.2

-0.2

100 110 120

Sign

al (

mV

)

0.16

-0.16

0.00Frequency:

Hz23.0refprecbeat

Static magnetic field ： B0 = 28.3 mG ((Xe)=33.5 Hz)

90°RF pulse （ 33.5 Hz , t = 3.0 ms, B1 = 70 mG )

Transverse relaxation ： T2 = 350 s 　；

T2 350 s

●Normally, spin precession is subject to decoherence (or, transverse relaxation) due to field inhomogeneity, spin-spin interaction, …..

While...●Accuracy of frequency determination:

Free precession

Time

Tra

nsve

rse

spin

Spin Maser

1/ 2

3 / 2

1Fourier width

# of data points

1

1

(3) Realization of a long precession time

(: measurement time)

Self-sustained precession

● P follows the Bloch equations:

or,

02

02

01

d,

d

d,

d

d.

d

x xy z y

y yz x x

z zx y y x z

P PP B P B

t T

P PP B P B

t T

P PP B P B P P G

t T

Spin Maser

B

● 129Xe polarization vector P = S/S

● Static field B0 = (0, 0, B0)

● Oscillating field B = (Bx, By, 0)

1,2

1

T P B P P

Pumping term

relaxation term

02

02

01

d,

d

d,

d

d.

d

y

x

y x

x xy z

y yz x

z zx y z

P PP B P

t T

P PP P B

B

B

B B

t T

P PP P P P G

t T

Spin Maser

B(t)

● Now we devise the B(t) field to follow P

( ) ( )

( ) ( )

x y

y x

B t P t

B t P t

B(t)

M.G. Richards, JPB 21 (1988) 665: 3He spin maserT. Chupp et al., PRL 72 (1994) 2363: 3He-129Xe two-species spin maser

02

02

01

d,

d

d,

d

d.

d

y

x

y x

x xy z

y yz x

z zx y z

P PP B P

t T

P PP P B

B

B

B B

t T

P PP P P P G

t T

Spin Maser

B(t)

● Now we devise the B(t) field to follow P

( ) ( )

( ) ( )

x y

y x

B t P t

B t P t

B(t)

Spin detection

Present work

Taking (1) + i (2) and setting

02

2

01

d 1, (4)

d

d. (3')

d

z

z zz

PP P

P P

it T

P PP Gt T

( ) ( ) ( )i tx yP t iP t e P t

The steady state solutions

　・ Trivial solution:

　・ Non-trivial solution:

d d0 and 0 .

d d zP P

t t

eq eq 10

1

0, 1z

GTP P P

GT

eq eq10 0

2 2

1 1/ 1, , with = .z

GTGP P P

T T

02

02

01

d, (1)

d

d, (2)

d

d. (3)

d

xy z

y yx z y

z zx x y

xx

y z

t T

t T

P Gt T

P PP P P

P PP P P

P PP P P P P

0 0

x y

y x

B P

B P

B

Masing mechanism

pump Feedbacksystem

Zeeman level

P(t)

B(t)

B0

● 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 > Pz /T2 ---- threshold

Torquefrom B

Relaxation and pumping effects

0

An analogue of LASER

Experimental apparatus

Enriched 129Xe : 230 torr Rb : ~ 1 mg Pxe ~ 10 % 18 mm

Xe gas cell

Pyrex spherical grass cellSurfaSil coated

Magnetic shield (3 layers )　 Parmalloy Size : l = 100 cm, d = 36, 42, 48 cm Shielding factor : S = 103

Pumping LASER

Tunable diode laser = 794.7 nm ( Rb D1 line ), = 3 nm Output: 18 W

Probe LASER tunable diode laser with external cavity = 794.7 nm ( Rb D1 line ), = 10-6 nm Output: 15 mW

Solenoid coil (for static field)　　 B0 = 28.3 mG ( I = 3.58 mA)

PEM Mod. Freq. 50 kHz

Si photo diode

Freq. band width: 0 – 500 kHz NEP: 810-13 W/Hz

Heater Tcell = 60 ~ 70 ℃

Pumping and probing laser system

Xe-cell

Lock-in amp.

Lock-in amp.

Operation circuit Wave generator

Modulated signal　　 PEM Modul. Freq. （ 50 kHz) 129Xe Larmor Freq.(33.5 Hz)

Probe light 4 turns 20cm

= 0° = -90°

Si photo-diode

R = 10 – 50 k

VX

VY

PSD-signal（ 0.2 Hz)

Feedback signal (33.5 Hz)

Feedback field

BFB =1T2

Feedback coil

1 G ( T2=100s) 1V

3.6 G

Pumping light

ref. ( 33.3 Hz )

ref.(50kHz)

(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.

)sin()( 0 tVtV ss

)()(cos2

1)( 00 rrrsX tVVtV

)()(sin2

1)( 00 rrrsY tVVtV

Detection of precession

Noise filtering by a low-pass filter

)sin()( 0rrr rtVtV

)()()()()( 21 tVtVtVtVtV rXrYFB

)cos(2

1 2srs tVV

Generation of the feedback signal

(33.5 Hz)

(0.2 Hz)

(33.5 Hz)

Optical-coupling Spin Maser

Maser oscillation signal

0 1000 2000 3000 4000

B0 = 28.3 mG , ref = 33.20 Hz, feedback gain: 18 G/0.1mV

Feedback system ON

Steady state oscillation

Measured frequency:

0.0

0.2

-0.2

3000 3010 3020

0.1

0.0

-0.1

Hz32.0refprecbeat

Sig

nal

(mV

)

Time (s)

0 10 20 88940 88950 88960 302910 302920( 84 hours)

0.0

0.4

-0.4Sig

nal

(V

)

Time (s)

Various transients depending on the feedback strength

0 1000 2000 3000 4000

0 1000 2000 3000 4000

0 1000 2000 3000 4000

0 1000 2000 3000 4000

0.0

0.2

-0.2

0.0

0.2

-0.2

0.0

0.2

-0.2

0.0

0.2

-0.2

Sig

nal

(mV

)S

igna

l (m

V)

Sig

nal

(mV

)S

igna

l (m

V)

Time (s)

10 G/0.1mV

4 G/0.1mV

14 G/0.1mV

28 G/0.1mV

Feedback Gain

Fre

quen

cy (

Hz)

33.592

33.588

33.584

33.580T2 = 6.2 s

T2 = 240 s

T2 = 14.8 s33.480

33.484

33.488

33.492

33.480

33.484

33.488

33.492

-20 -10 0

-20 -10 0

-20 -10 0

(deg)

(deg)

Frequency shift due to the feedback phase error

Effect of a phase error in the feedback field

Frequency shift due to the feedback phase error

20

20

)(

)(

T

PBPBP

dt

dP

T

PBPBP

dt

dP

yxxz

y

xyzy

x

( ) ( )iB t i e P t

( ) ( )B t i P t

●Ideal feedback field:

20 2

tan

T

02

d 1 (4)'

d i

z

Pe P i P

t T

T2=300 s, = 0.1º = 1 Hz

Feedback

field

spin

Frequency characteristics

Fourie spectrum ( 1 hr. run )

Conventional spin maser( = 3.56 kHz )

Low-frequency spin maser( = 33.5 Hz )

10 100 1000

-3/2

Frequency

pre

cisi

on (

Hz)

Time (s)

1

10

100

0.1

Frequency precision vs. meas. time

Current fluctuation in solenoid coil

3.5870

3.5866

3.5862

(mA

)

0 2000 4000 6000Time (s)

B0 ~ 0.8 G

(1) Incorporation of a low-noise current source for solenoid

Replacement of the reference voltage diode low-noise battery

I ≈ 200nA ≈ 1Hz

I ≈ 5nA ≈ 25nHz

3.542600

3.542800

3.543000

3.543200

3.543400

3.543600

3.543800

3.544000

10000 12000 14000 16000 18000 20000 22000 24000 26000 28000 30000Time (s)

Sole

noid

cur

rent

(mA)

3.542820

3.542825

3.542830

3.542835

3.542840

3.542845

10000 12000 14000 16000 18000 20000 22000 24000 26000 28000 30000

Time (s)

Sole

noid

cur

rent

(mA)

PSE-1101

Ｔａｋａｓａｇｏ

PSE-1101

5nA

200nA

(2) Installation of a new magnetic shield

Construction of 4-layer shield

l = 1600 mm, R= 400 mm

Transverse: S ≈106

Longitudinal: S ≈104

Estimated shielding factor

- 100

- 80

- 60

- 40

- 20

0- 25 - 15 - 5 5 15 25

Measured residual field

z (cm)

Fie

ld (G

)

longitudinal

transverse

Shielding factor : S ≈104

χ2 fitting: f = 36.60605206 +/- 0.00000130 Hz

Free precession signal

27-Sept-2006

Beat freq. (Hz)

Previous system

New system

Fourier spectra with old and new current sources（ for 5500s period ）

Xe cell for an E-field: a trial piece

(3) Electric field application

Electrodes currently under testing are: ・ Al (0.1 mm thich) plated on Pyrex glass endcaps (40 mm 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)

● Magnetic field fluctuation

● Magnetic fluctuation due to collision with Rb atoms

Feedback phase error : [n] 22

][tan

Tn

1

)/(2

2

2

mase

TNS

tr

= 0.7 nHz (S/N=1000) for 5 days run

Installation of atomic magnetometer into low frequency spin oscillator

sensitivity : 10-11 10-12 G/Hz B 10-13 G ( (Xe) 0.1 nHz )

interaction with Rb atomic spins (109/cc) P(Rb) 0.01 % ( re-polarization from Xe ) (Xe) 0.2 nHz (T 0.01˚C)

Estimation of frequency precision

1

2/3

1

1000 100 10 1 0.1 0.01

Pre

cisi

on (

H

z )

1 10 100 1000 10000

Time (s)

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