Nuclear spin maser at highly stabilized low magnetic fieldand
search for an atomic EDM
A. YoshimiRIKEN
K. Asahi, T. Inoue, M. Uchida, N. HatakeyamaDept. Phys., Tokyo Inst. Tech.
The 18th International Symposium on Spin Physics (SPIN08), UVa,2008/10/6-11.
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+++
Time: t -t
Spin: s -s
EDM: d d
EDM and physics beyond the standard model
Non-zero EDM associated with spin Direct evidence of violation of time reversal symmetry
Time Reversal
In the standard model…. only possibility is CKM complex phase δCKM : → predicted EDM is too small to detect (105 smaller than the present experimental upper limit)
Beyond the standard model … detectable size of EDM is suggested : more than two CP violating phases
W W
f’fL fLe+iδ e -iδ
E
fL fR
E
Lie Rie
f~
f~
~
No EDM effect from one loop diagram
EDM effect from one loop diagram
EDM search with various species
Neutron EDM
EDM in diamagnetic atom
EDM in paramagnetic atom
Direct detection of neutronExperiment with UCN
Small EDM due to “Schiff shielding”Sensitive to T-violating interaction between nucleons.
Detection of electron EDM (small)Large enhancement in heavy element
129Xe, 199Hg, Ra, Rn
Cs, Tl, Fr
Other Molecule (YbF, PbO), deuteron, …
|dn| < 2.9×10-26 ecm (C.A. Baker et al., PRL. 97 (2006) 131801)
|de| < 1.6×10-27 ecm (B.C. Regan et al., PRL. 88 (2002) 071805)
|dHg| < 2.1×10-28 ecm (M.V. Romalis et al., PRL. 86 (2001) 2505)
Limit the SUSY-particle mass
CP phase in SUSY:A,
Phase pattern in M=500GeV case
From experimental upper limit of different elements …
T. Falk et al., hep-ph/9904393
EDM search in diamagnetic atom
cm10)3.37.0( 27 ed
cm10)1.13.0( 26 ed
Xe12954
1984. Vold et. al., PRL 52 (1984) 2229.
2001. Rosenberry and Chupp, PRL 86 (2001) 22.
1987. Lamoreaux et. al., Phys. Rev. Lett. 59 (1987) 2275.
cm10)5.17.0( 26 ed
cm10)49.006.1( 28 ed
Hg19980
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
Optical pumping of Hg atomOptical pumping spin-exchange in Rb-Xe
About 129Xe
Large spin polarization through spin exchange with polarized atom
Spin exchange with optical pumped Rb atomP > 10 % for Xe atomic density of 1018 /cm3
Long coherence time of atomic spin
No chemical interactionNo quadrupole interaction of nucleus ( I=1/2 )
Continuous spin maser technique
129Xe
Rb
Free precession
TimeTra
nsve
rse
spin ‘Spin maser’ state
TimeTra
nsve
rse
spin
Optical detection of nuclear spin precession
• Low static field experiment ( mG ) Small field fluctuation Use of the ultra high sensitive magnetometer
Spin maser with 129Xe at low static field
Inducedcurrent
C
B0
L
I nPQ
BFB
Pumping light LCB
10
Spin maser with the tuned coilof tank circuit
200
2 1
2
1
TInPQ
> kHz (B0 = 1 G)
Oscillation threshold
Artificial feedback throughthe optical spin detection
Operation at low magnetic fieldSmall field fluctuationHigh-sensitive magnetometerLong intrinsic T2
B0 mG
Probe laserbeam
Pumping laser beam
Lock-in detection
Phase shifter
Photo diode
Feedback coil
Nuclear spin
M. Richards et al., J. Phys. B 21 (1988) 665.T. Chupp et al., PRL 72 (1994) 2363. A. Yoshimi et al., PLA 304 (2002) 13.
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
Enriched 129Xe : 230 torr Rb : ~ 1 mg Pxe ~ 10 % 18 mm
Xe gas cell
Pyrex spherical grass cellSurfaSil coated
Magnetic shield (3 layers ) Permalloy 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 ℃
Experimental Setup
129Xe cell
Feedback coil
Heater - tube Probe Laser
PEMPumping Laser
Magnetic shield (4 layer)Φ : 400 mm, L = 1600 mm
Solenoid coilΦ : 254 mm, L = 940 mm
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 ;
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
T2 350 s
Free precession signal of 129Xe
0 20000 40000 60000 80000
0 1000 2000 3000 4000 5000 60000 60020 60040
0.8
0.4
0.0
-0.4
-0.8
Sign
al (V
)
Time (s)
transient steady-state oscillation
-0.8
-0.4
0.0
0.4
0.8
0.00.10.2
-0.2-0.1
B0 = 30.6 mG 0 = 36.0 Hz
Maser oscillation signal
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)
New one
Previous current source
5nA
200nA
Improvement of field fluctuation
Replacement of the reference voltage diode low-noise IC at low frequency
I ≈ 200nA (610-5)
I ≈ 5nA (1.410-6)
Main source frequency fluctuation
B0 - field fluctuation Current fluctuation for solenoid
At time scale of 10000 s…
Fabrication of new current source
)(X tV )(Y tV
Frequency precision
Measurement by lock-in detection ( beat freq. = maser freq. – reference freq. )Two signals (X, Y – compnents) ; their phases differ by π/2.
)()(2
)(
)(tan)(
0ref0ref
1
t
tV
tVt
X
Y
X, Y signals Precession phase φ Phase fluctuation : obs(t) – fit(t)
4500 4505 4510 4515 4520 4525 4530
0.00
-0.20
0.20
0
10000
20000
0 10000 20000 30000
0.0
0.4
0.8
-0.8
-0.4
0 10000 20000 30000
(9nHz)
Hz0000000090 123115067.00ref .ν
(rad) (rad)
(V)
(s)
(s) (s)
Determination precision of the maser with different measurement time
Frequency precision
10-5
10-6
10-7
10-8
10-9
Fre
qu
en
cy p
recis
ion
(H
z)
10-4
102 103 104 105
Measurement time (s)
10
with previous setup
2/3
0.6 μHz@ 3x104 s
Determination precision of the maser with different measurement time
10-5
10-6
10-7
10-8
10-9
Fre
qu
en
cy p
recis
ion
(H
z)
102 103 104 105
Measurement time (s)
9 nHz@ 3x104 s
2/3
1
Frequency precision
10
10-4
with previous setup
with present setup
750 nHz@ 3x104 s
2 orders improvement
350 nA ; 1.4 μG ∼ 1.7 mHz
1.5 mHz
Drift of solenoid current
Frequency drift of the maser
2mHz driftNow investigating
Long term stability of the maser frequency
why δν -1/2 in t > 1000 s ? why δν get worse in t > 30000 s ?
Frequency fluctuation in 1000s-avaraging
10 nA ; 40 nG ∼ 50 μHz
100 μG → 100 nG → 125 μHz
1.) drift of solenoid current in 1000 s time scale
2.) drift of environmental magnetic field in 1000 s time scale
100 μHz
0 20000 40000 60000 80000(s)
0 20000 40000 60000 80000(s)
123.0
122.9
123.1
123.2
123.3
0 10000 20000 30000
(mHz)
(s)
Long term drift in solenoid B0 field
122
123
124
125
7.3537
7.3538
7.3539
7.3540
7.3541(m
A)
(mH
z)
Ongoing R&D for EDM experiments
High-sensitive Rb magnetometerTemperature control and current
Solenoid current
Temperature
∼2.5℃
Time (h)0 24 48 72 96 120
Long term drift of room temperature : δT 2.5 ℃ → drift of solenoid current : δI 500 nA
Temperature stabilization of current source → 0.1 ℃ in 1-day time scale → 5 nA fluctuation ( 20 nG )
Nonlinear Magneto-Optical effect of Rb atom
High sensitive magnetometer
D. Budker et al.,PRA 62 (2000) 043403.
k
Linear polarized light
Rb atom
Faraday rotation
B
1×104 rad/G, 4×10-12 G/Hz (B < 0.1G)
7.3530
7.3520
500 nA
20
22
24
( )℃
(mA)
10-13 G → 0.1 nHz → 10-29 ecm
Ongoing R&D for EDM experiments
Electric field application
Now testing the fabricate the field plate and cell in which the leakage current is Suppressed.
Digital feedback control
Temperature control
Test cell for electric field applicationAl – electric plate : 40 mmφGlass cell (Corning 7740, 7056) : 20 mm(h)
Calculation of feedback field by computer-based device.
Stabilization of cell temperature → Polarization, magnetic noise
68.7
68.8
0 5 10 15 20 25Time (h)
( )℃ 0.04 ℃
Summary and Future
● 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)
● The spin maser has been operating with a stable static field (δB ~ 10nG).
● Frequency precision of the maser has reached 9 nHz, corresponding to an EDM sensitivity of 910-28 ecm (E=10kV/cm).
● Further improvements and developments are now being proceeded: Temperature control of current source and cell, Precise magnetometer, Electric field application, Precise maser feedback system.
● Measured fundamental characteristics indicate that this scheme would provide promising means to pursue a search for EDM in 129Xe atom down to a level of d(129Xe) = 10-29 ecm. ( 0.1 nHz).
Main frequency noise in EDM experiment
・ Sensitivity limit of the magnetometer : 10-13 G → 0.1 nHz → 10-29 ecm.
・ Magnetic noise of Rb atom in collision : 0.2 nHz → 10-29 ecm.
EDM in diamagnetic atom
SRd AA
EextEext + Eint = 0
0intext EEd
Eint
Schiff shielding
Total EDM effect with E is canceled I
SrdrZ
rdreSI
rdrr
3232 1
3
5
10
1
Electron angular momentum = 0
Sensitive to P,T- odd effect in nucleus
Atomic EDM is induced by the nuclear Schiff moment S
Schiff moment is induced by P,T-odd nuclear force
NRS
udF ddmf
mgG
~~32ππ
20πpp1
CP-odd pion exchange is dominated by chromo-EDM of quarks
cmfm/100.4)Hg( 317 eeSd
cmfm/107.2)Xe( 318 eeSd
Feedback system
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 磁場
BFB =1
T2
Feedback coil
1 G ( T2=100s) 1V
3.6 G
Pumping light
ref. ( 33.3 Hz )
ref.(50kHz)
Producing the feedback field delayed by 90° in phase to precession signal
Low pass filtering ( fcut ~ 0.8 Hz )Reconfiguration of precession – correlated signal
High S/N feedback signal
)sin()( 0 tVtV ss
)()(cos2
1)( 00 rrrsX tVVtV
)()(sin2
1)( 00 rrrsY tVVtV
Detection of spin precession
Frequency transformation forlow pass filtering
)sin()( 0rrr rtVtV
)()()()()( 21 tVtVtVtVtV rXrYFB
)cos(2
1 2srs tVV
Construction of feedback signal
(33.5 Hz)
(0.2 Hz)
(33.5 Hz)
Fre
quen
cy (
Hz) 33.592
33.588
33.584
33.580 T2 = 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
Phase error of feedback field
Frequency shift due to the feedback phase error
20
20
)(
)(
T
PBPBP
dt
dP
T
PBPBP
dt
dP
yxxz
y
xyzy
x
)(~
)(~
FB tPeitB Ti
)(~
)(~
FB tPitB TIdeal feedback field:
20 2
tan
T
)(~
)()(~
)(1
)(~
TT02
T tBtPitPiT
tPdt
dz
T2=300 s, = 1º = 10 Hz
Feedback
field
spin
Source of frequency fluctuation
10 nA ; 40 nG ∼ 50 μHz
100 μG → 100 nG ∼ 125 μHz
1.) drift of solenoid current in 1000 s time scale
2.) drift of environmental magnetic field in 1000 s time scale
Expected sensitivity for EDM experiment
cm1010)Xe( 3029 ed
Installation of atomic magnetometer into low frequency spin maser
sensitivity : 10-11 10-12 G/Hz B 10-13 G ( (Xe) 0.1 nHz )
Main source of frequency noise
interaction with Rb atomic spins (109/cc) P(Rb) 0.01 % ( re-polarization from Xe ) (Xe) 0.2 nHz (T 0.01˚C)
Conceptual setup
Probe light(Magnetometer)
(E=10kV/cm)
● 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 dB 10-13 G ( (Xe) 0.1 nHz )
interaction with Rb atomic spins P(Rb) 0.01 % ( re-polarization from Xe ) (Xe) 0.2 nHz (T 0.01˚C)
Expected sensitivity to EDM
Estimation of frequency precision
1
2/3
1
1 10 100 1000 10000
Time (s)