Ultrahigh precision observation of nuclear spin precession

andapplication to EDM measurement

T. Inoue, T. Furukawa, H. Hayashi, M. Tsuchiya, T. Nanao, A. YoshimiA, M. Uchida, and K. Asahi

Department of Physics, Tokyo Institute of TechnologyANishina Center, RIKEN

International Workshop on Physics of Nuclei at Extremes@TITech, Japan 26. Jan. 2010

Outline◇Electric Dipole Moment (EDM)- EDM and T - violation- Status of EDM experiment

◇ 129Xe “active” nuclear spin maser- Character of 129Xe atom- Experimental apparatus- Optical pumping and optical detection- Nuclear spin maser

◇ Experimental result- Present status of spin maser

◇ On going R & D- Feedback system of solenoid current- Improvement of the optical pumping efficiency

◇ Summary and future

0d ： T-violation CP-violation (by CPT theorem)

Search for EDM Test of the SM and beyond SM Search for EDM Test of the SM and beyond SM (no SM background)(no SM background)

Non-zero EDM associated with spin isdirect evidence of time reversal symmetry violation

Standard Model (SM) : Predicted neutron EDM is about 105 smaller than the present experimental upper limits.Beyond SM : Detectable EDM

EDM : sensitive to the CP-violation beyond SM

rrrd 3

particlede

Classical representation

sd ˆd

Vector(parallel to spin)

Time reversal Time reversal ： ： TT t →→ -t

s →→ -sd →→ d

TimeTimeSpinSpinEDMEDM

::::::

s

-- -

++ +

d -s

-- -

++ +

d

Electric Dipole Moment (EDM)

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

Pendlebury and Hinds,

NIM A 440 (00) 471d(129Xe) < 4.1×10-27 ecmRosenberry and Chupp, PRL 86 (2001) 22

d(199Hg) < 3.1×10-29 ecm

W.C. Griffith et al., PRL 102 (2009) 101601

Neutron EDM predicted values|dn| < 2.9 × 10-26 ecmC.A. Baker et al., PRL. 97 (2006) 131801

Historical Limits of EDMs

dEBH E parallel to B

dEBH E anti-parallel to B

Energy shift according to E direction

Small shift of spin precession frequency

h

dEB 22 )//( BE

h

dEB 22 )//( BE

h

dE4

EDM measurement => measurement of the tiny shift in the frequency of the spin precession

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

EdBμ HHamiltonian:Energy level of spin1/2 system

(if > 0, d > 0)

Principles of EDM measurement

Character of 129Xe atom

●Stable particle　　　　 High density ： 1018 ～ 1019 atom/cm3

@ room temperature

●High polarization and Long relaxation time　　　　 Polarization : P (129Xe) ~ 40 % (AFP-NMR)　　 Relaxation time :Tw ～ 20 min

●Spin maser technique

AFP-NMR signal

spin maserspin maser

Free spin precession

2/1mT 2/3

mT

Steady oscillation (maser state)

Search for d(129Xe) using “Active” nuclear spin maser

Goal : d(129Xe) ~ 10-29 ecm

Continuous spin precession (maser oscillation)

mT

Tra

nsve

rse

spin

☐ Accumulation of free spin precession

+ + · · · · +

T T T

Tra

nsve

rse

spin

2/1m

indfinal

11 TTnn

t timemeasuremen : m

m

T

TnT

21mm

2/3m

mfinal : points data

11 :dth Fourier wi :

/TTT

T

Probe laser・ DFB laser・ Wavelength : 794.76 nm (Rb D1 line)・ = 8.4×10-6 nm・ Output : 15 mW

Pumping laser・ Wavelength : 794.76 nm (Rb D1 line)・ = 3 nm・ Output : 11 W

PEM

Heater

Circularly polarizing plate

Si photo diode・ Band width : 0 ～ 500 kHz・ NEP : 8 10-13 W/Hz

Magnetic shield (4 layers)・ Permalloy (Fe-Ni alloy) Solenoid colil (for static field)

・ B0 = 30.6 mG (I0 = 7.354 mA)0B

C70T

129Xe : 230 torrN2 : 100 torr Rb : ~ 1 mgPyrex glass

SurfaSil coated

18 mm

129Xe gas cell

Experimental apparatus

129129Xe nuclear spin polarizationXe nuclear spin polarization

IS

129Xe

Rb

Rb

129Xe

N2

N2

129Xe Rb

Rb 129Xe

Nuclear spin polrization through spin exchange interaction with Rb atom

Selective excitation

by circularly polarized light

Rb atomic energy level

Rb atomic polarizationby optical pumping

nm 76.794:

1/2ms

1/2ms 1/2P5

1/2S5

1/2P5

1/2S5-1/2ms

-1/2ms

Optical detection of nuclear spin precession

129XeRb

B0

Rb

129Xe

129Xe 129Xe

Probe light ： 794.76 nm

circular polarization (modulated by PEM)

Transmission intensityMax

After half periodof 129Xe spin precession

Polarization transfer from 129Xe nuclei to Rb atom (re-pol.)

129Xe nuclear spin precession : detected by using probe light (Rb D line)

Rb

129Xe

129Xe

129Xe

B0

Transmission intensityMin

s 802 T

Typical 129Xe free spin precession signal

Magnetic shield (4 layers): 400 mm, L = 1600 mm for the outermost layer

Solenoid coil : 254 mm, L = 940 mm

Heater

Cell Box

129Xe gas cell

Feedback coil

Heater - tube Probe laser

PEMPumping laser

Maser operation in low static field (~ mG)Small field fluctuation => Small frequency fluctuation

Yoshimi et al., (2002) “Active” nuclear spin maserProduction of the feedback field by using optical detection method

P(t)

B(t)

B0

0

P(t)

Feedbacktorque

Relaxation , pumpingeffect

Static magnetic field : B0 　 mG

Pumping light

Photodiode

Feedback coil

Probe light Feedbackcircuit

Lock-in detection

Spin precession signal

Feedback system

②Nuclear spin precession detectionby optical detection method

①129Xe nuclear spin polarizationby optical pumping method

③Feedback signal generationby feedback system

④Sustained Spin precessionthrough the coupling between

nuclear spin and feedback field

Nuclear spin maser

Feedback system on

Steady oscillation

BB00 = 30.6 mG => = 30.6 mG => 00 = 36.0 Hz = 36.0 Hz

Start-up enhancement

Maser signal

kV/cm) 10( cm 109

sec) 000,30( nHz 3.928

Eed

t

2/3T1T

Frequency precision

~ 1.5 mHz<=> ~ 40 ppm

Frequency fluctuation

~ 350 nA<=> ~ 40 ppm

Solenoid current fluctuation

t > 30,000sec -> precision getting worse

⇔ drift of the solenoid current

Frequency precision (present status)

○ constructing the feedback system for the solenoid current.

○ constructing the electric field application system.

○ developing the highly sensitive magnetometer.

k

Linear polarized light

Rb atom

B

○ simulating the frequency analysis.

We are now

○ installing the fiber laser for the optical pumping laser.

Convex lens

129Xe gas cell

○ constructing the feedback system for the solenoid current.

○ constructing the electric field application system.

○ developing the highly sensitive magnetometer.

k

Linear polarized light

Rb atom

B

○ simulating the frequency analysis.

We are now

○ installing the fiber laser for the optical pumping laser.

Convex lens

129Xe gas cell

Present situationSolenoid coil for static field ~ 1

current : ~ 7 mAvoltage : ~ 10 mVCurrent fluctuation : ~ 500 nA/dayStability : ~ 70 ppm

Stabilization of the solenoid current

High precision Current monitor

Stable current source1 : ~ 7 mA

www1

Voltage reading precision : 1ppm/dayReference resistor precision :

1ppm/day

www

www

1 k

10

100:1 resistance splitting = 140 pA/day stability

FeedbackFeedback

@1 mA range±12 ppm ± 2nA/day = 14 nA/day stability

Stable current source1 : ~ 7 mA

Solenoid coil for static field ~ 1

Stable current source2: ~ 1 m

KETHLEY 2002High precision

Voltage monitor, 8.5 digit

ADC inc, model 6161@10mA range±7 ppm ± 20 nA/day = 70 nA/day stability

Stabilization of the solenoid current

Goal : ~ 5 ppm(~ 35 nA) Stability

kV/cm) 10( cm 109

sec) 000,30( nHz 3.928

Eed

t

2/3T1T

Frequency precision

~ 1.5 mHz<=> ~ 40 ppm

Frequency fluctuation

~ 350 nA<=> ~ 40 ppm

Solenoid current fluctuation

Improvement of Frequency precision

Suppression of solenoid current drift ~ 0.1 nHz for one week measurement d ~ 10-29 ecm (E = 10 kV/cm)

Introduction of the fiber laser for the optical pumping

• present pumping laser : array type high output laser <- it is difficult to irradiate the cell uniformly.

• introduction of the fiber laser - uniform irradiation to the cell - increase of the unit area intensity : 0.6 W/cm2 ⇒ 0.9 W/cm2

=>improvements of Rb polarization and 129Xe nuclear polarization : suppression of maser amplitude fluctuation

Introduction of fiber laser

Probe laser・ DFB laser・ Wavelength : 794.76 nm (Rb D1 line)・ = 8.4×10-6 nm・ Output : 15 mW

PEM

Heater

Circularly polarizing plate

Si photo diode・ Band width : 0 ～ 500 kHz・ NEP : 8 10-13 W/Hz

Magnetic shield (4 layers)・ Permalloy (Fe-Ni alloy) Solenoid colil (for static field)

・ B0 = 30.6 mG (I0 = 7.354 mA)0B

C70T

129Xe : 230 torrN2 : 100 torr Rb : ~ 1 mgPyrex glass

SurfaSil coated

18 mm

129Xe gas cell

Pumping laser (Fiber laser)・ Wavelength : 794.76 nm (Rb D1 line)・ = 3 nm・ Output : 11 W

Prism

Introduction of fiber laser

Fiber laser

convex lens(f = 70 mm)

Gran laser prism

Circularly polarizing plate

convex lens(f = 200 mm)

PEM

Convex lens

129Xe gas cell

Spherical cell・ good symmetry・ scattering of pumping light<= decrease of optical pumping efficiency?

Cubic cell preparation

Am

plit

ude

[V]

Am

plit

ude

[V]

Am

plit

ude

[V]

Am

plit

ude

[V]

time [sec]

time [sec] counts

counts

Maser amplitude (steady state)Fiber laser

Array laser

Maser amplitude : Fiber laser v.s. Array laser

~ 4 times deterioration

Summary and Future

○ The frequency precision of 9.3 nHz (measurement time 30,000 sec) was obtained by operating the “active” spin maser.

○ The feedback system of the solenoid current is being constructed in order to suppress the current drift.

○ The fiber laser as the pumping laser was installed. However the fluctuation of the maser amplitude did not improve. The cubic cells are now being prepared.

Further improvements and developments are now in progress. :◎ Constriction of the electric field application system

◎ Development of the highly sensitive magnetometer based on NMOR; Nonlinear Magneto-Optical Rotation.

◎ Frequency analysis simulation

=> search for d(129Xe) in the level of 10-29 ecm