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