Search for electric dipole moment of the electron
with laser-cooled radioactive atoms
Cyclotron and radioisotope center (CYRIC) Tohoku Univ.
Hirokazu Kawamura
Tohoku University Scienceweb GCOE The 5th gcOE International Symposium on “Weaving Science Web beyond Particle-Matter Hierarchy”
March 4 – March 6, 2013
Contents
1. Physics motivation
2. Rubidium factory
3. Francium factory
4. Summary and plan
H. Arikawa, S. Ezure, K. Harada, T. Hayamizu, T. Inoue, T. Ishikawa, M. Itoh, T. Kato, T. Sato, T. Aoki, T.
Furukawa, A. Hatakeyama, K. Hatanaka, K. Imai, T. Murakami, H.S. Nataraj, Y. Shimizu,
T. Wakasa, H.P. Yoshida and Y. Sakemi.
CYRIC; Univ. of Tokyo; TMU; TAT; RCNP; JAEA; Kyoto Univ.; IITR;
Tohoku Univ.; Kyusyu Univ.;
Collaborators
Symmetry and its violation • Parity (spatial inversion symmetry)
is violated. – 1956 T.D.Lee and C.N.Yang
– 1957 C.S.Wu
60Co 60Ni + e- + ν -
• How about the time reversal symmetry?
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Search for the violation of time reversal symmetry
spin J -J
d d
Permanent electric dipole moment (EDM) d
• Nonzero EDM d will violate the time reversal symmetry as well as the parity.
• Require extremely-high experimental precisions!
Laser cooling and trapping techniques
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Multi Higgs
Left- Right
SUSY
f~1
f~a/p
Journey of electron-EDM search
J.J.Hudson et al., Nature 473, 493 (2011) May 2011
An electron EDM can induce a net atomic EDM. The net EDM of a heavy atom can be many times larger than the electron EDM.
YbF
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
No experimental result of EDM search for cooled/trapped radioactive atoms
GOAL
EDM measurement
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Cs EDM CELL experiment
(Phys. Rev. Lett., 63, 965, 1989)
Tl EDM BEAM experiment
(Phys. Rev. Lett., 88, 071805, 2002)
B=0
E=0
B≠0
E=0
B≠0
E//B
B≠0
E//-B
2μB 2μB + 2dE 2μB - 2dE
m = +1/2
m = - 1/2
E B
Magnetic dipole moment
Electric dipole moment
μ
d
Limitations of cell and collinear beam experiment
Systematic errors in EDM experiments Motional magnetic fields, Misalignment of static magnetic field B0 with static electric field E; cause a component of Bm to lie along B0
Magnetic field BE, generated by leakage and/or changing currents, inaccuracy of high voltage electric field reversals, correlated with E Geometric phase shifts generated by complicated field gradients Magnetic Johnson noise generated by traditionally used metals in Electric field plates, vacuum chamber, magnetic shield etc
2c
EvBm
v E
B0
These effects limit the precision of e-EDM measurement…
Some of effects originate from the motion of the particles.
To overcome these systematic errors, laser cooling and trapping is employed for measuring the e-EDM.
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Laser cooling and trapping
atom photon
Absorption = one-sided Emission = isotropic
Cool down
1-dimensional cooling (e.g. deceleration of atomic beam)
ωa
ωl
ωl + kv = ωa
3-dimensional cooling (e.g. trap of atom)
Anti-Helmholtz coil
Atom cloud
Doppler shift … Zeeman shift
MOT: magneto-optical trap
Zeeman coil
Two-level system
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Absorption and emission Change momentum
Fr ed
Frd
Francium
Enhancement factor:
Heaviest alkali metal = Francium : ⇒simple electronic structure and large nucleus ⇒Enhancement of EDM: Z=87 K~103
No stable isotopes: radioactive atom Several isotopes with long half-life ⇒210Fr =3.2 min, 211Fr =3.1 min, 212Fr =20. min.
Laser cooling and trapping techniques: localize atoms ⇒ Reduce systematic errors
23~~ aZd
dK
e
atom
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Overview of Fr EDM experiment
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Francium: heaviest alkali element Advantage to EDM experiment
EDM measurement
Laser cooling
& trapping
Neutralization
Rubidium: one of alkali elements Useful for pilot experiments
Ion beam
transport
Ionization
Stable isotopes
Production
using cyclotron
Mini Laser-Cooled Rubidium Factory
Rb-ion source
(Ionization)
Ion-beam focus lens & diagnosis
(Ion beam ransport) Beam converter
(Neutralization)
MOT
(Laser cooling & trap)
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Rb+ Rb
Trap!
1 meter
Rubidium-Ion Source
Rb
Rb
Rb
Rb
Rb+
Rb+
Rb+ Rb+
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Thermal ionization EIP(Fr)<EWF(Mo)
kT
EE
n
n IPWFexp2
10
EIP (Ionization potential): Fr 4.1 eV
EWF (work function): Mo 4.6 eV
Saha-Langmuir equation
Hot metal
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Ion beam focus lens (electrostatic quadrupole triplet)
50mm
Ion trajectory simulation
by TOSCA (finite-element technique)
z
z
y
x
y
x
+
+
- -
Ion beam
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Beam converter
Thermal ionization EIP < EWF(Mo)
kT
EE
n
n IPWFexp2
10
EIP (Ionization potential): Fr 4.1 eV
EWF (work function): Mo 4.6 eV
Saha-Langmuir equation
for ionizer
Thermal neutralization EIP > EWF(Y)
EWF (work function): Y 3.1 eV
for neutralizer
Atom: ion potential
Positive ion
Neutral atom
Target: work function
HIGH Ionization LOW Neutralization
Rb+
Rb
Hot metal
Magneto-optical trap (MOT)
σ+ σ-
σ-
σ- σ+
σ+
Neutralized Rb Trap!
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
σ+ σ-
m = 0
m = 0 z
E
ωlaser ωatom
Mini Laser-Cooled Rubidium Factory
Rb-ion source
(Ionization)
Ion-beam focus lens & diagnosis
(Ion beam ransport) Beam converter
(Neutralization)
MOT
(Laser cooling & trap)
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Rb+ Rb
Trap!
1 meter
Image b
rightness
Experimental results
This guy is the trapped Rb!
The maximum 106 atoms in trap
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
dia. ~ 2 mm
More trapped atoms are required!!
Laser-cooled francium factory @ CYRIC
Laser room
Optical fiber
Ext. room
Cyclotron
Target room
Target room EDM meas. area (Ext. room)
Wall
18O5+ (100MeV)
Fr+ (5 keV) Fr atom
197Au + 18O Fr + xn neutralize trap
AVF Cyclotron
Beam swinger
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
10 meter
Fr+-ion source ~ Thermal ionizer
Thermal ionization EIP(Fr)<EWF(Au)
kT
EE
n
n IPWFexp2
10
EIP (Ionization potential): Fr 4.1 eV
EWF (work function): Au 5.1 eV
Saha-Langmuir equation
18O5+
Fr+
Primary beam
Einzel lens
Oven
Gold target ~1000oC
Extraction electrode
Fusion reaction: 18O + 197Au → 210Fr + 5n
Ions can be extracted by electric fields.
Available for molten gold.
Desorption from high-temperature liquid target
⁃ Faster diffusion ⁃ Convection flow ⁃ Clear surface
Efficient Ion Production
Rb beam test w/o cyclotron.
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Laser-cooled francium factory @ CYRIC
Target room EDM meas. area (Ext. room)
Wall
18O5+ (100MeV)
Fr+ (5 keV) Fr atom
197Au + 18O Fr + xn neutralize trap
AVF Cyclotron
Beam swinger
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
10 meter
2012 November
1st beam diagnosis system 4th beam diagnosis system
Alpha-decay spectrum from produced Fr
241Am (5.5MeV)
210Fr (6.5MeV)
209Fr (6.6MeV)
Fr+
SSD
Solid State Detector: detect alpha particles from unstable nuclei.
Checking source (241Am) placed near SSD for energy calibration.
Blue:
originating from 241Am
Green:
originating from 208-212Fr and also daughter nuclei
preliminary
Francium is identified using SSD in Diagnosis system.
Diagnosis system
Alpha-decay spectrum was obtained at a diagnosis system
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Experimental results (2012.Nov.)
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Gold target (room temperature)
Molten gold (~ 1000 C)
Achieved 210Fr+ yield: ~106 ion/sec
Laser-cooled francium factory @ CYRIC
Target room EDM meas. area (Ext. room)
Wall
18O5+ (100MeV)
Fr+ (5 keV) Fr atom
197Au + 18O Fr + xn neutralize trap
AVF Cyclotron
Beam swinger
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
10 meter
2012 November
1st beam diagnosis system 4th beam diagnosis system
Fr beam transport (2012.Nov.)
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
1st beam diagnosis system
4th beam diagnosis system
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Laser-cooled francium factory @ CYRIC
Target room EDM meas. area (Ext. room)
Wall
18O5+ (100MeV)
Fr+ (5 keV) Fr atom
197Au + 18O Fr + xn neutralize trap
AVF Cyclotron
Beam swinger
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
10 meter
2012 November
1st beam diagnosis system 4th beam diagnosis system
Beam converter
2013 February
Fr neutralization (2013.Mar.)
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
241Am (5.49 MeV)
211Fr (6.53 MeV) 210Fr (6.54 MeV)
preliminary
208Fr (6.64 MeV) 209Fr (6.65 MeV)
Neutralizer target: Y (Tmelt=1526oC, EWF=3.1eV)
Ionizer oven: Pt
(Tmelt=3825oC, EWF=5.6eV)
Orthotropic type beam converter
Heated yttrium
f20
f2
Ion
atom
23mm
+1V Shield
-300V Neutralizer (Y)
Ionizer (Pt) GND
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Electric field simulation by OPERA-3d/TOSCA
f50
f2
Towards the highly efficient trap and EDM measurement…
Beam converter Transverse cooling Zeeman slower
1st MOT (diagnosis)
2nd MOT (reservoir)
Push
lase
r
Magnetic shield
Optical trap
laser
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
Optical tweezer
EDM measurement chamber
Summary and Outlook
Hirokazu Kawamura / Search for electric dipole moment of the electron with laser-cooled radioactive atoms
GOAL Fr-EDM experiment
SETUP Mini laser-cooled Rb factory
Rb ionization Ion transport Neutralization Trap
Laser-cooled Fr factory at Cyclotron & Radioisotope Center
Fr ion production Ion transport Neutralization Trap Not yet
PLAN - Upgrade of each device - Francium trapping - Development of EDM measurement system