Post on 03-Jan-2016
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