Search for electric dipole moment of the electron with ...

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


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


No experimental result of EDM search for cooled/trapped radioactive atoms

GOAL

EDM measurement


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.


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


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


Overview of Fr EDM experiment


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)


Rb+ Rb

Trap!

1 meter

Rubidium-Ion Source

Rb

Rb

Rb

Rb

Rb+

Rb+

Rb+ Rb+


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


Ion beam focus lens (electrostatic quadrupole triplet)

50mm

Ion trajectory simulation

by TOSCA (finite-element technique)

z

z

y

x

y

x

+

+

- -

Ion beam


Beam converter

Thermal ionization EIP < EWF(Mo)

kT

EE

n

n IPWFexp2

10


EWF (work function): Mo 4.6 eV


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!


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)


Rb+ Rb

Trap!

1 meter

Image b

rightness

Experimental results

This guy is the trapped Rb!

The maximum 106 atoms in trap


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


10 meter

Fr+-ion source ~ Thermal ionizer

Thermal ionization EIP(Fr)<EWF(Au)

kT

EE

n

n IPWFexp2

10


EWF (work function): Au 5.1 eV


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.




Wall

18O5+ (100MeV)

Fr+ (5 keV) Fr atom


AVF Cyclotron

Beam swinger


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


Experimental results (2012.Nov.)


Gold target (room temperature)

Molten gold (~ 1000 C)

Achieved 210Fr+ yield: ~106 ion/sec



Wall

18O5+ (100MeV)

Fr+ (5 keV) Fr atom


AVF Cyclotron

Beam swinger


10 meter

2012 November


Fr beam transport (2012.Nov.)


1st beam diagnosis system

4th beam diagnosis system




Wall

18O5+ (100MeV)

Fr+ (5 keV) Fr atom


AVF Cyclotron

Beam swinger


10 meter

2012 November


Beam converter

2013 February

Fr neutralization (2013.Mar.)


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


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


Optical tweezer

EDM measurement chamber

Summary and Outlook


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

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