2007/11/02 nEDM Meeting @ BOSTON 1

Dressing Field Study

Pinghan Chu

University of Illinois at Urbana-Champaign

nEDM Collaboration Meeting @ Boston

• Dressed Spin in nEDM• Study with polarized 3He beam• Study with polarized 3He in cell• Comparison between experiments and

calculations• Future Plan

2007/11/02 nEDM Meeting @ BOSTON 2

Dressed Spin in Neutron EDM

• Neutrons and 3He naturally precess at different frequencies (different g factors)

• Applying a RF field (dressing field), B1Sin(dt) , perpendicular to the constant B0 field, the effective g factors of neutrons and 3He will be modified (dressed spin effect)

• At a critical dressing field, the effective g factors of neutron and 3He can be made close!

2007/11/02 nEDM Meeting @ BOSTON 3

Dress field can modify neutron and 3He g

factors:

3neutron

Larmor 0 0

He

3 1n 1n 0 3 0

0 0

= = B

d d

c c

BBJ J

J x J x

Critical dressing of neutrons and 3He

0If / 1 dY B

3Heneutron 1.19

3.86

6.77

9.72

cx3

n 1

0

1.1127

/

/

n

d

d

x B

y

Effective dressed

g factors:

X=nB1/d

X=1.19

0 d

P

Y 0.01, B 1[mG], ω

ro

=

posa

2π 1[kHz]

:l

2007/11/02 nEDM Meeting @ BOSTON 4

Measurement using polarized 3He Beam

1 K cold head

Injection nozzle

Polarizerquadrupole

Spin flip region

Analyzerquadrupole

3He RGAdetector

B1 dressing

B0 static

Polarizer Analyzer RGA

36 in

3He Spin dressing experiment

Ramsey coils

2007/11/02 nEDM Meeting @ BOSTON 5

Observation of 3He dressed-spin effect

Esler et al, nucl-ex/0703029, to appear in Phys. Rev.

2007/11/02 nEDM Meeting @ BOSTON 6

The Goal of the UIUC measurement

1. To explore other dressing field settings (different B0, B1 and d).

2. To explore the dressed spin effect of polarized 3He in a cell at room temperature (rather than polarized 3He beam).

3. Dressing effect for 3He in superfluid 4He

4. The effect of the dressing field on the 3He relaxation.

2007/11/02 nEDM Meeting @ BOSTON 7

Experimental Setup @ UIUC

Z

X

Dressing Coils /2 Coils

RF discharge

3He Cell

Laser

B0 Coils

B0

Photo diodeB1

Pickup Coils

2007/11/02 nEDM Meeting @ BOSTON 8

Experimental Setup @ UIUC

Pickup Coils

3He Cell

/2 coils

Dressing Coils

Helmholtz Coil Pair

Laser

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Experimental Setup @ UIUCDAQ

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Experimental Steps1. Polarize 3He nuclear spins. (Metastability exchange with

optical pumping) (by Laser and B0)

2. /2 burst to rotate the spin to x-y plane. (by B/2Sin(0t))

3. Apply dressing field, B1Sin(dt), and measure precession frequency by the pickup coils and Lock-in amplifier.

X

Y

Z

X

Y

Z

X

Y

Z

B0 B0 B0

/2 burst NMR signalPolarize spins

B/2Sin(0t) B1Sin(dt)

2007/11/02 nEDM Meeting @ BOSTON 11

To Polarize 3He with metastability exchange

C9 C8

C9Circular Photons

RF discharge

Metastability Exchange

fluorescence light (optical

signal)

Optical Pumping

Laser Frequency

Dio

de

sig

nal

Deplete mF= -3/2,-1/2 states

2007/11/02 nEDM Meeting @ BOSTON 12

Tb

2 / 2

1 2 4b b b

bb b b

f B

Tf B

Optical Signal

1. Demonstrate 3He polarization.

2. /2 coils or dressing coils magnetic field calibration.

Applying a continuous rotating field

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Pickup Coils Signal

20

t

TR Ae C

*Lockin Reference freq = Precession freq

2007/11/02 nEDM Meeting @ BOSTON 14

Dressed Spin Effect (Measurement)

[Volts]P

icku

p A

mp

litu

de (

A)

2007/11/02 nEDM Meeting @ BOSTON 15

Dressed Spin Effect (For Y<1)

Y=0.423

Y=0.176

0 0

1 1

d d

d d

By

Bx

dre

ssed

/

Bessel Function J0

2007/11/02 nEDM Meeting @ BOSTON 16

Dressed Spin Effect (For Y>1)

Y=7.153

Y=4.763

Y=2.381

Y=1.43

dre

ssed

/

0 0

1 1

d d

d d

By

Bx

2007/11/02 nEDM Meeting @ BOSTON 17

Dressed Spin Effect

† †int 0

1/21

0 0

1 1

number of photons

( )

/ 2

M RF Z d X

d d

d d

n

H H H H S a a S a a

B n

BY

BX

C. Cohen-Tannoudji and S. Haroche, J. Phys. (Paris) 30, 125, 153 (1969)

1 0 0 0 02 4

0 1 0 0 02 4

0 0 04 2 4

0 0 04 2 4

0 0 0 1 04 2

0 0 0 0 14 2

Y Xn

Y Xn

X Y Xn

X Y Xn

X Yn

X Yn

6x6

46x46

Jaynes-Cummings Hamiltonian

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Dependence of effective in dressing fieldWithout dressing field

0 0

E E

B B Y

0( )B

Y

2007/11/02 nEDM Meeting @ BOSTON 19

Dependence of effective in dressing fieldWith dressing field

E E

B B Y

E

E

0( )B

Y

2007/11/02 nEDM Meeting @ BOSTON 20

Dressed Spin Effect (For Y<1)

Y=0.423

Y=0.176

0 0

1 1

d d

d d

By

Bx

dre

ssed

/

Bessel Function J0

2007/11/02 nEDM Meeting @ BOSTON 21

Dressed Spin Effect (For Y>1)

Y=7.153

Y=4.763

Y=2.381

Y=1.43

dre

ssed

/

0 0

1 1

d d

d d

By

Bx

2007/11/02 nEDM Meeting @ BOSTON 22

Future Plans

• Study dressing field effect in different situation at room temperature and further in the low temperature,

• Study of systematic uncertainties,• Study the effect of the dressing field

on 3He relaxation time.

2007/11/02 nEDM Meeting @ BOSTON 23

Acknowledgment

• D. Beck, S. Clayton, A. Esler, J.-C. Peng, S. Williamson, J. Yoder.

• J. Blackburn, E. Thorsland

• B.-Z. Hu, S. Y. Ngan, C. H. Sham, L, H. So (Summer Student)

• Z. H. Yu, M. H. Yung (Theory)

2007/11/02 nEDM Meeting @ BOSTON 24

Bloch Equation Simulation

0 1

( )

ˆ ˆ sin z

dB

dt

B kB iB t

Undressed 3He and Neutron Spins Dynamics http://www.youtube.com/watch?v=7V3lUVWFybE

Undressed 3He spin and dressed 3He spin http://www.youtube.com/watch?v=L-dF3Vca5PA

Dressed 3He and Neutron Spins Dynamicshttp://www.youtube.com/watch?v=vlPHb-DeCMc