Improving the detection sensitivity

of dark-matter axion search

with a Rydberg-atom single-photon detector

M.Saeed For

newCARRACK CollaborationKyoto

FPUA2010

T. Arai, A. Fukuda, A. Matsubara,T. Mizusaki, A. Sawada,M.Saeed:

S. Ikeda, K. Imai, T. Nakanishi,Y. Takahashi:

Y. Isozumi, T. Kato, D. Ohsawa,M. Tosaki:

K. Yamamoto:

H. Funahashi,J.Uda:

Y. Kido, T. Nishimura, S. Matsuki:

Research Center for Low Temperature and Materials Sciences, Kyoto University

Department of Physics, Kyoto University

Radioisotope Center, Kyoto University

Department of Nuclear Engineering, Kyoto University

Institute for the promotion of excellence in higher education Kyoto University

Department of Physics, Ritsumeikan University

T. Arai, A. Fukuda, A. Matsubara,T. Mizusaki, A. Sawada,M.Saeed:

S. Ikeda, K. Imai, T. Nakanishi,Y. Takahashi:

Y. Isozumi, T. Kato, D. Ohsawa,M. Tosaki:

K. Yamamoto:

H. Funahashi,J.Uda:

Y. Kido, T. Nishimura, S. Matsuki:

Research Center for Low Temperature and Materials Sciences, Kyoto University

Department of Physics, Kyoto University

Radioisotope Center, Kyoto University

Department of Nuclear Engineering, Kyoto University

Institute for the promotion of excellence in higher education, Kyoto University

Department of Physics, Ritsumeikan University

newCARRACK Collaboration

(1) Principle of Rydberg-atom single-photon detector

(2) Performance of detector : measurements of blackbody radiations in a cavity at low temperature

(3) Sensitivity limit: effect of stray electric field

(4) Practical design for improving the sensitivity

Contents

ＡｘｉｏｎA hypothetical particle postulated by Peccei-Quinn in 1977 to resolve the so called strong CP problem in QCD.is a well-motivated candidate for the Dark Matter

Dark MatterRotation-velocity distribution of a typical spiral galaxy A: expected B: observed

Rotation curve of a typical spiral galaxy, i.e. rotating velocity of the galaxy versus distance from the center of the galaxy, cannot be explained only by the visible matter. Existence of a roughly spherically symmetric and centrally-concentrated matter called galaxy halo explains the rotation curve. Non-visible form of matter which would provide the enough mass and gravity is called “DDark ark MMatteratter”.

10-6[eV] < ma < 10-3[eV] 240[MHz] < f < 240 [GHz]

4s1/2

Axion

B0

ns1/2

np1/2

Diode laser 766.7nm

4p3/2

Diode laser 455nm

γ

Primakoff effect Rydberg atom

｜ｇ 〉

｜e 〉

Ｌｏｗｅｒ　ｓｔａｔｅ　｜ｇ＞Ｕｐｐｅｒ　ｓｔａｔｅ　 |e ＞

Principle of the Kyoto Rydberg-atom single-photon detector

39K

Axion is resonantly converted to a single microwave photon by a Primakoff interaction ,enabling us to develop an effective axion detection by counting axion converted photons indirectly

Schematic

LaserElectron multiplier

Dilution fridge

electron

Fieldionizationelectrodes

Atomic beamMetal posts for tuning

mirror

7Tmagnet

Whole System

Liquid Helium

Dilution fridge and selective field ionization detector

Electron multiplier

Selective Fieldionization region

Laser set up

Top view of the Dilution Fridge

Noise source

Blackbody radiation in the cavity

Cavity temperature must be kept as low as possible

Stray electric field limited the

Sensitivity

Reduction of absorption probability of photon in the resonant cavity (Resonance broadening)

Degradation of the selectivity in the field ionization process (SFI) (Rotational effect of electric field)

Actual pulsed-field ionization scheme

Lower state

Upper state

111

111

111P

111S

111P

111S

M. Tada et al., Phys. Lett. A 349(2006)488

Measurement of blackbody radiationsin a resonant microwave cavity

SQL Limit

2527 MHz

p

st

sa

p

p

st

st

sa

sa

Improvements

1. Instead of Rb ,Potassium Rydberg atoms will be used (reduce the effect of Stark broadening in the microwave absorption Process)

2. Guiding field method to avoid the rotation of the electric field

3. A spatially collimated bunched packets of Rydberg atomic beam (by laser cooling)

time varying electric field will be applied to compensate the stray electric field.

Improvements

1. Instead of Rb ,Potassium Rydberg atoms will be used (reduce the effect of Stark broadening in the microwave absorption Process)

2. Guiding field method to avoid the rotation of the electric field

3. A spatially collimated bunched packets of Rydberg atomic beam (by laser cooling)

time varying electric field will be applied to compensate the stray electric field.

Improvements (1): Use of 39K Rydberg atoms instead of 85Rb

H.Haseyama et al J.Low Temp Phys150 549(2008)

39K 85Rb

Electric field [mV/cm]

2800

2900

3000

3100

0 10 20 30 40

39K: n =102

Experimental data of Stark shift in 39K for n=102

More Precise measurements are in Progress

s-p

ener

gy d

iffer

ence

[M

Hz]

Red solid circles : Preliminary experimental data for the s1/2 to p3/2 　 transitionsopen circles : those for the s1/2 to p1/2 transitions.

Improvements

1. Instead of Rb ,Potassium Rydberg atoms will be used (reduce the effect of Stark broadening in the microwave absorption Process)

2. Guiding field method to avoid the rotation of the electric field

3. A spatially collimated bunched packets of Rydberg atomic beam (by laser cooling)

time varying electric field will be applied to compensate the stray electric field.

Guiding electric fieldImprovements(2): Cavity and electrodes

cavityStark electrode

SFI electrodes

electrodes forfield rotation

atomic beam

y

zfield direction

Stark field direction

Cavity electro-magnetic field: TM010

E

M.Shibata et al J.Low Temp Phys 151 1043(2008)

-40

-30

-20

-10

0

10

20

30

40

x=0,y=0excitation point

cavity SFI box

-100

-50

0

50

100x=0,y=0

θ

φ

excitation point

cavity SFI box

50 100 150 200

z [mm]

[m

V/c

m]

Ang

le [

deg

r ee]

xy

z

θ

φ

|E|

Ex

Ey

Ez

Ele

ctri

c fi

eld

Cavity and electrodes structure

i.d. 90, length 958cylindrical TM010 mode

A distinctive step to overcome the stray electric field dynamically

• Instead of continuous beam a spatially collimated bunched packets of Rydberg atomic beam will be used by laser cooling technique and by applying time varying field to compensate the stray field

• Increasing absorption probability and state selectivity

Improvements

1. Instead of Rb ,Potassium Rydberg atoms will be used (reduce the effect of Stark broadening in the microwave absorption Process)

2. Guiding field method to avoid the rotation of the electric field

3. A spatially collimated bunched packets of Rydberg atomic beam (by laser cooling)

time varying electric field will be applied to compensate the stray electric field.

Time to reach the bunched beam from trap to Resonant Cavity

S=1.365 mV=350 m/st = 3.9 ms

Spatial Spread 　 of 39K at the position of the Resonant Cavity

V = 350m/st 1(time taken for accelerated motion)=1.4

ms

S1(Distance Traveled to attain V ) = 0.24 m

S2(Distance to Resonant Cavity)=1.365m

t2(Time to reach the Cavity)=3.9 ms

Velocity spread after acceleration=2m/s

Spatial spread after acceleration is about 2mm

at the position of cavity spatial spread increase

Improvements(3): Laser cooled bunched beam

T=145mK

Summary

Obtained preliminary data of Stark Shift of 39K Constructed the Guiding Field system in the cavity.

More precise measurement of Stark Shifts of 39K Experimental testing of Guiding electric field and sensitivity up to 10 mK Designing and construction of laser cooling apparatus for collimated bunched beam of 39K Rydberg atoms

Improvements in Progress

Present Status

Thank you For

your kind Attention

Room Temp39K source

Ion Pump

Anti Helmotz coils

Laser Beams

s+

s-

s-

-

C.Monroe et all Phy.Rev.Lett,65,1571(1990)

Omit this slide

B=monIr2/2(r2+z2)3/2

If separation is twice of the Radius of the coilB= (4/5)3/2monI/rCoil Radius (r) = 30mmSeparation (z) = 60mmNumber of turns (n)=25Current=3ARequired Field Gradient=0.20T/m

Anti -Helmholtz coils

z

x

y

I

I

s-

s+

s+

s-

s-

s+

n=10 n=100 n=1000

Mean radius

n2 53A0 0.53micro meter

53micrometer

Binding energy

1/n2 1100cm-1 11cm-1 0.1m-1c

Period of electronic motion

n3 0.15pico second

0.15ns 0.1micro second

Polarizebility

n7 0.2 0.2x107 0.2x1014

Spacing between adjacent level

n-3 200cm-1 0.2cm-1 2x10-4cm-1

Ionization field

n-4 33000v/cm

3.3v/cm

3.3x10-4 v/cm

Some parameters regarding axion-photon-atom system

Initial average quantum state occupation number of axion=5.7x1025

Spread in the axion energies=10-11eV/h

Axion- photon- photon coupling constant=4x10-26eV/h

Collective coupling constant between the resonant photons and the N

Rydberg atoms=1x10-10eV/hCavity length=20cmV=350m/s

Ma=10-5ev

Q=2x10-4

Loading Rate Coefficient also depends upon the beam diameter and the Total intensity of the trapping laser as shown in fig.3

Fig. 3 .Loading rate coefficient l as a function of (a) beam

diameter d and of (b) intensity Itot

Some Parameters dependence of 39K Trap

1.Number of Trapped atoms(N)

2.Loading Rate Coefficient(l)

3.Trapped atoms density(n)

4.Loss Rate

Itot=220mW/cm2 and beam diameter is 1.2cm Williamson III JOSA B Vol 12 ,1393(1995)

Kitagawa, Yamamoto, and Matsuki, 2000.

From Kitagawa,Yamamoto, and Matsuki, 1999.

33

Shibata et al., Rev.Sci.Inst. 74(2003)3317.

atomic beamatomic beam

e-

0.15kV

1kV

CEM

Cross Sectional View

20K