T. Inoue,1 T. Nanao,1 M. Tsuchiya,1 H. Hayashi,1 T. Furukawa,1 A. Yoshimi,2 M. Uchida,1 H. Ueno,2 Y. Matsuo,2 T. Fukuyama,3 and K. Asahi1
1 Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan2 RIKEN, 2-1 Horosawa, Wako-shi, Saitama 351-0198, Japan
3 Ritsumeikan University, Nojihigashi, Kusatsu, Shiga 525-8577, Japan
Search for an electric dipole moment in 129Xe atom using a nuclear spin oscillator
Workshop on Fundamental Physics Using Atoms 7 - 9 August 2010, Osaka
OUTLINE:
1. Introduction
2. "Optically coupled" spin oscillator
3. Present status
4. Summary
s
+ ++-
--+
-
+q
-q
a = d ≡ qa
Electric Dipole Moment (EDM) d
3
particle( ) dd r r ror,
5EDM 2
id F
L
or,
Electric Dipole Moment
1. Introduction
Eext
(Permanent) Electric Dipole Moment
+ ++
= 0
Electric dipole moment (EDM)Electric dipole moment (EDM)
time reversal time reversal s →→ -sd →→ d
spinspinEDMEDM
::::
s
-- -
++ +
d s
-- -
++ +
d
d ≠ 0 : : Violation of T ⇒ Violation of CP (CPT theorem)
● The violation of CP is implemented in the Standard Model (SM), but ...
● CP violation in SM (K-M mechanism) is not sufficient to explain the matter-antimatter asymmetry observed in the universe.
Thus, ...● An extra CP-violation is required.
Electric dipole moment (EDM)Electric dipole moment (EDM)
time reversal time reversal s →→ -sd →→ d
spinspinEDMEDM
::::
s
-- -
++ +
d s
-- -
++ +
d
d ≠ 0 : : Violation of T ⇒ Violation of CP (CPT theorem)
Sites of EDM searches• neutron dN
• paramagnetic atoms (Tl, Fr, Cs, ...) de
• diamagnetic atoms (129Xe, 199Hg, Rn, Ra, ...) S
• molecules (TlF, YbF, PbO, ThO, ...) de
• charged particles (d, , ...) dN, d
⇒ Probing different facet s of anticipated new physics
Electric dipole moment (EDM)Electric dipole moment (EDM)
time reversal time reversal s →→ -sd →→ d
spinspinEDMEDM
::::
s
-- -
++ +
d s
-- -
++ +
d
d ≠ 0 : : Violation of T ⇒ Violation of CP (CPT theorem)
Tl, Fr, Cs… 129Xe, 199Hg, Rn, Ra…
M. Pospelov and A. Ritz,Annals of Phys. 318, (2005) 119-169
EDM in 129Xe atoms
•stable particle•macroscopic number of particles•EDM generated by a nuclear
Schiff moment•P,T-violating NN interaction
Schiff moment
How does the EDM appear in a diamagnetic atom?
Point nucleus in an atom
Electrostatic (r)
due to a cloud of atomic electrons
+d
q
=
x = d/q Atomic electrons do not "know" whether the nucleus has EDM.
Atomic electrons feel a non-trivial charge distribution unside the nucleus.
EDM d
Nucleus with a finite size
q EDM d
q
=
Nucleus
q q
Nontrivial charge distribution in the nucleus generates an EDM in atom:
Schiffatom
0
ˆ0 0 ˆ2 , where iP iP
P P ee
E E
D
d D R
Schiff 4 ( ) S R
2 2 3
nucleus
1 5( ) d
10 3r r S r r r Schiff moment
d(129Xe) = 3.8×105 fm2 ·S(129Xe)
d(199Hg) = 2.8×104 fm2 ·S(199Hg)
datom ≠0
Nucleus
Electron cloud
[Ginges & Flambaum, Phys. Rep. 397 (04) 63]
What generates a Schiff moment ?
199 (0) (1) (2) 3( Hg) 0.0010 0.074 0.018 fmNN NN NN NN NN NNS g g g g g g e
with SkO' effective interaction,[J.H. de Jesus and J. Engel, Ann. Phys. 318 (05) 119]
--- (In language of nuclear physics)
CP-violating components of the NN interaction generate S.
●Case of 199Hg
●Case of 129Xe Flambaum, Khriplovich, Sushkov, 1985 Dzuba, Flambaum, Porsev, 2009 Yoshinaga's group, consideration fro shell model in progress.
(0)u d
(1)u d
,NN
NN
g d d
g d d
d(129Xe) < 4.1×10-27 ecmRosenberry and Chupp, PRL 86 (2001) 22
d(199Hg) < 3.1×10-29 ecm
Grifith et al., PRL 102 (2009) 101601Standard Model(dn = 10-(31-33) )
Neutron EDM predicted values
d = 1027 e·cmE = 10 kV/cm
= 10 nHz( 1°/day )
[Pendlebury and Hinds, NIM A 440 (00) 471]
dEBH E // B
dEBH E // B
Energy shift upon an E-field reversal
Shift in a precession frequency
h
dEB 22
)//( BEh
dEB 22
)//( BE
the difference ⇒ signal of an EDM
EdBμ H
2
1m
2
1m
0
0
E
B
0h h hν
BE
B
//
0BE
B
//
0
0
0
E
B
B E
s
B E
s
Energy levels for a spin 1/2(for a case of > 0, d > 0)
h
E 4 d
Detection of an EDMDetection of an EDM
Desires long precession times => Spin maser
― Realization of a long precession time
Key issue for a high-sensitivity EDM detection:
Free precession
TimeTra
nsve
rse
spin ‘Spin maser’ state
TimeTra
nsve
rse
spin
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 = I/I
● Static field B0 = (Bx, By, B0)
1,2
1
T P B P P
Pumping term
relaxation term
[T.E. Chupp et al, Phys. Rev. Lett. 72 (94) 2363][M.A. Rosenberry and T.E. Chupp, Phys. Re. Lett. 86 (2001) 22]
● 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
[T.E. Chupp et al, Phys. Rev. Lett. 72 (94) 2363][M.A. Rosenberry and T.E. Chupp, Phys. Re. Lett. 86 (2001) 22]
● If a capacitor C is connected to form a resonating circuit, the coil produces a transverse B field, B(t),
( ) ( )
( ) ( )
x y
y x
B t P t
B t P t
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
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 oscillator
B(t)
● Now we devise the transverse part of the B field, B(t), to follow P
( ) ( )
( ) ( )
x y
y x
B t P t
B t P t
B(t)
Spin detection
Setup for the maser experimentSetup for the maser experiment
Probe laserProbe laser・ DFB laser・ = 794.76 nm (Rb D1line)・ = 8.4×10-6 nm・ Power : 15 mW
Pumping laserPumping laser・ = 794.76 nm (Rb D1line)・ = 3 nm・ Power ~ 11 W
PEM
Heater
/4 plate
Si photodiode・ Bandwidth : 0 ~ 500 kHz
magnetic shield (4-layer)・ permalloy
Solenoid coil (static field)・ B0 = 30.6 mG (I = 7.354 mA)
0B
C70T
spin precession signal
129Xe : 230 torrN2 : 100 torr Rb : ~ 1 mgPyrex glass
SurfaSil coating
129Xe gas cell
18 mm
Spin polarization of 129Xe and Optical detection of nuclear precession
Spin polarization of 129Xe Detection of precession of 129Xe
2
1sm
2
1sm
2/1P5
2/1S5
D1 line : 794.7 nm
IS
129Xe
Rb
Rb
129Xe
N2
N2
129Xe Rb
Rb 129Xe
Rb
Xe
Xe Xe
Circular polarization(modulated by PEM)
RbXe
Xe
Xe
RbXe
Probe laser beam : single mode diode laser (794.7nm)
Transverse polarization transfer : 129Xe nuclei → Rb atoms (re-pol)
Spin-echange in Rb-Xe
Optical pumping Rb atom
After half-period precession
B0
Detector
Spin oscillatorSpin oscillator
Realization of maser oscillation at very low fields ( mG)Suppression of drifts in the B0 field => Suppression of drifts in
“Optically coupled” spin maserwith a feedback field generated according to optical spin detection
P(t)
B(t)
B0
0
P(t)
Feedback torque
Pumping and relaxation effect
Static magnetic field : B0 mG
Pumping light
Photodiode
Feedback coil
Probe light Feedbackcircuit
Lock-in detection
precession signal
Feedback system
② Optical detection of the spin precession
①129Xe nuclear spin polarizationby optical pumping
③Generation of a feedback field
④Self-sustained spin precession
Probe Laser(DL-DFB)
PEMArray-type
Laser
Mirror
Glan Laserprism
Fiber-coupledLaser
HeaterMagnetic Shield
Ookayama Campus,Tokyo Inst. of Technology,Tokyo, Japan
Frequency determination
Time [rad]
Pha
se [
rad] bxaxf 2)(
)(
)(tan)( 1
tV
tVt
X
Y
Lock-in Amplifier output
Δa = 9.310-9 Hz freq. precision
Time [s]
Sig
nal [
V]
VX VY
・ Phase
fitting function
))()(2sin(
))()(2cos(
0ref0ref
0ref0ref
tV
tV
Y
X
・ Lock-in amplifier output signals
νref Reference frequencyν0 Xe precession freq.
Lock-in amplifier
PhotoDiodedetector
FunctionGenerator
refout 0ref
0
35Hz
35.1HzRb
Xe
Xe
Xe
B0
Xe
Result
Long term stability of the oscillation frequency
Solenoid current
129Xe cell temperature
Fre
quen
cyF
requ
ency
time (0 - 30,000 sec)
At present,
there are a number of concerns:
・ Do imperfections in spin detection, signal processing, feedback field generation, ... affect the oscillation frequency?
・ Does the presence of Rb atoms interfere the measurement?
・ Does the low frequency operation really help in reducing the spourious drifts?
These should be tested and investigated by using actual setup.
Frequency pulling effect
Simulation
Expt.●A phase deviation in the feed
back field will induce a shift in the Maser frequency.
0
2
tanT
zi
i
z
PeiT
tPeitB
tBtPiiT
tPdt
d
02
TT
T02
T
1
)()(1
)(
Ongoing developments
・ Pumping laser
・ Double cell
・ B0 stabilization
・ Simulation study
・ Magnetometry
B||
φ
fitting
Paraffin coating
z
z 0.0-2.0-4.0-6.0 2.0 4.0 6.0
0.0
0.2
0.4
0.6
-0.2
-0.4
-0.6
NMOR magnetometry
15
0
4 10 GB
dB
dB
[Tsuchiya et al.]
[Hayashi et al.]
[Furukawa et al.]
[Inoue et al.]
[Nanao, Yoshimi et al.]
[M. Tsuchiya, ... ]
[T. Furukawa, ... ]
[H. Hayashi, T. Furukawa, ... ]
[T. Nanao, A. Yoshimi, ... ]
[T. Inoue, ... ]
HV application system preparation
- Cubic cell size : 20 mm × 20 mm × 20 mm Pyrex glass (corning 7740)
- Transparent electrode : ITO (Indium Tin Oxide) transmittance ~ 85%@795 nm size : 30 mm × 30 mm × 1.75 mm resistance : ~ 30
High voltagePicoammeter
Transparent electrode
Xe cell for an E-fielda trial piece
HV
A
Cell
R : 1 MR : 1 M
C : 2 nF
Protection circuit for picoammeter
Leakage current test
HV [kV]
Lea
kage
cur
rent
[nA
] preliminary
spark
[T. Inoue, ... ]
HV application system preparation
Next step…- Smaller cell (10 mm gap)- Using 2 high voltage source (positive and negative)- N2 or SF6 gas atmosphere- Low pass filter for reducing the noise output by HV source …
300nA, ~40ppm
1.5mHz~40ppm
Current fluctuation
Fluctuation of Xe precession
Frequency instability : mostly due to current fluctuation
In magnetic shield: ~28 mG magnetic field with a solenoid coil
& stabilized current source (applying 7mA current)
Current instability = magnetic field fluctuation → Frequency instability
Magnetic field stabilization
Previous current source- stabilized current source
drift : <50nA in a few hour
- slow & large drift (up to 1uA) in long-term operation
Current source
~ 7 mA
Using an accurate voltmeter with a reference resistanceto obtain high resolutions
Two current sourcesare installed in parallelfor setting resolutions
Feedback of current fluctuation(measured with Dig. Voltmeter)
to correct the current drift
Current source 1
~ 6.5 mA
Current source 2
~ 0.5 mA
Digital Voltmeter Feedback
A new current supply system
Stability improved ! Fluctuation:<1/200
This fluctuation is mainly due to the accuracy of current measurement.
Conclusion: The current stability is improved successfully (x200) with the feedback of current fluctuation.
stability – limited by accuracies of current measurement
Future : More accurate measurement of current drift → More stabilized magnetic field for EDM measurement
Performance of new current source
FutureFuture
Spherical cell・ good symmetry・ Reflection ⇒ lowering of the pumping efficiency? Cubic cells
DFB Laser Diode
Optical Isolator
Taper Amplifier
Introduction of a narrow-line laser(TA DFB, TOPTICA)
Power : ~ 430 mWline width : ~ 4MHz(cf. pressure broadening ~ 7.5 GHz)
20 times enhanced pumping efficiency
=> suppression of amplitude fluctuations
-17 sec 10~
SetupSetup
ポンピング部分(偏極生成部分 )
偏極度測定部分Double cell for 129Xe gas
偏極度測定装置
129Xe : 227torrN2 : 133torr
Rbパイレックスガラス
SurfaSil コーティング
RF coil
pick-upcoil
ポンピングレーザー
保持磁場用コイル
Cell test benchCell test bench
・ Incorporation of anti-vibration system・ Orthogonality adjustment mechanism for pick-up coil
・ Incorporation of anti-vibration system・ Orthogonality adjustment mechanism for pick-up coil
High-precision, high-reproducibility assesment system for 129Xe cells High-precision, high-reproducibility assesment system for 129Xe cells
trim coil
pick-up coil
material:PEEK
pick-up coil 固定されていない→測定の再現性が低い , 調整が困難 , 振動に弱い pick-up coil が振動→NMRシグナルと同じ周波数である RFシグナルを検出→ノイズの発生
pick-up coil 固定されていない→測定の再現性が低い , 調整が困難 , 振動に弱い pick-up coil が振動→NMRシグナルと同じ周波数である RFシグナルを検出→ノイズの発生
New system
Current problems
Simulation study of the frequency precision
Incorporate the phase and amplitude fluctuations of the maser signal.
periflucnn
x
t
tAA
A
2
)(
sinV
1
0
A : シグナル振幅ε : 振幅のゆらぎ
Time [s]
Sig
nal [
V]
Time [s]
Pha
se d
evia
tion
[rad
]
Time [s]
Pha
sede
viat
ion[
rad]
ν :測定周波数φfluc :位相ゆらぎφperi :周期変動
Fre
quen
cy P
reci
sion
[Hz]
Time [s]
Simulation results
Should reach a 10-10 Hz precision in a 2-day measurement !!
2.3 x 10-10 Hz6.7 x 10-11 Hz2.0x10-11 Hz
Experiment
A , ≈ the experiment
A ≈ the experiment, peri ≈ 0.5A , ≈ 1/10
←1.9x10-30 ecm(E=10kV)
12days1dayHalf a day
periflucnn
x
t
tAA
A
2
)(
sinV
1
0
Simulation
Magnetometry ; Non-linear MagnetoOptical Rotation (NMOR) on Rb atoms
k
Linear polarized light
Rb atom
B
Resonant optical rotation in Rb vapor
(NMOR; Nonlinear Magneto-Optical Rotation)
D. Budker et al.,PRA 62 (2000) 043403.
HzpG/1~B
Optical Pumping magnetometers (Rb, Cs) : 30 pG/ √Hz
Magnetometry with SQUID : 2-3 fT/ √Hz = 20-30 pG /√Hz @ He temp. 50-60 fT/ √Hz = 0.5 – 0.6 nG/ /√Hz @ liq. N2 temp. High-Q resonator → 0.08 fT/√Hz = 0.8 pG /√Hz
Advantages:
Narrow width
Operation at room temp.
low field
x
z
y
B +E
+t
Required frequency precision
Field precision required in EDM measurements
cm10~ -28 ed A@ E=10kV/cm
nHz1f
pG1BField
mF = -1 mF = 0 mF = +1
gB
+ -
(F’=0)
(F=1)
1) 直線偏向光 により原子は alignment 状態になる → 原子集団の蒸気は linear dichroism を持つ
2) 原子 alignment が磁場の周りを歳差運動する → dichroism の軸が回転する
3) 回転する dichroic 軸を持つ原子と入射直線偏光ビームとの 相互作用で偏光面が回転する
原理
NMOR
00
00 2
21
iBg
nzBF
直線偏向光と原子の相互作用
0
2
0
0
221
2
2 l
l
Bg
Bg
nnl
zBF
zBF
右・左円偏向成分に対する原子系屈折率
直線偏向面の回転
-10 -5 0 5 10
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.60
B2
zF Bg
Ro
tatio
n a
ng
le (
mra
d)
00
112
1
112
1
F
FF
FF
m
mm
mm
基底状態
Summary
● Precession of 129Xe spins is maintained for unlimitedly long times, by application of a feedback field generated from optically detected spins. The merit of this optically coupled spin maser as a scheme for the EDM search is the capability of operation at very low B0 fields, as mG or below.
● Frequency precision presently reached is 9.3 nHz, which corresponds to an EDM sensitivity of 910-28 ecm (E=10kV/cm).
● There still remain drifts/fluctuations in the maser frequency that are correlated with ambient temperature and noises. Improvements and further developments are under progress.
・ Reinforcement of 129Xe polarization by introducing a narrow-line high-power
TA-DFB pumping laser ・ Stabilization of solenoid current ・ Stabilization of cell temperature by means of a heat transfer fluid GALDEN ・ Cell development for the E-field application ・ Magnetometry with NMOR,
aiming at detection of d(129Xe) in a 1028 -1029 ecm regime.