of dark-matter axion

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15 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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Improving the detection
sensitivity

of dark
-
matter
axion

search


with a Rydberg
-
atom

single
-
photon detector



M.Saeed

For

newCARRACK Collaboration

Kyoto




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


Axion

A 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 Matter

Rotation
-
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 “
D
ark
M
atter
”.

10
-
6
[eV] < m
a

< 10
-
3
[eV]


240[MHz] < f < 240 [GHz]

4s
1/2

Axion

B
0


ns
1/2

np
1/2

Diode laser 766.7nm

4p
3/2

Diode laser 455nm

γ

Primakoff effect

Rydberg atom

|g







Lower

state

|g>

Upper

state

|e


Principle of the Kyoto Rydberg
-
atom single
-
photon detector

39
K

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

Laser

Electron multiplier

Dilution

fridge

electron

Field

ionization

electrodes

Atomic beam

Metal posts

for tuning

mirror

7T

magnet

Whole System

Liquid Helium

Dilution fridge and selective field

ionization detector

Electron
multiplier

Selective
Field

ionization
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 radiations

in a resonant microwave cavity

SQL Limit

2527 MHz

p

s
t

s
a

p

p

s
t

s
t

s
a

s
a

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
39
K Rydberg atoms instead of
85
Rb

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

39
K

85
Rb

Electric field [mV/cm]

2800

2900

3000

3100

0

10

20

30

40

39

K:

n


=102

Experimental data

of

Stark

shift in
39
K for n=102

More Precise measurements are in Progress

s
-
p energy difference [MHz]

Red solid circles : Preliminary experimental data for the s
1/2

to p
3/2

transitions

open circles : those for the s
1/2

to p
1/2

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 field

Improvements(2):


Cavity and electrodes

cavity

Stark electrode

SFI electrodes

electrodes for

field rotation

atomic beam

y

z

field direction

Stark field direction

Cavity electro
-
magnetic field: TM
010

E

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

-
40

-
30

-
20

-
10

0

10

20

30

40

x=0,y=0

excitation point

cavity

SFI box

-
100

-
50

0

50

100

x=0,y=0

θ

φ

excitation point

cavity

SFI box

50

100

150

200

z [mm]



[

m

V

/

c

m

]

A

n

g

l

e



[

d

e

g

r

e

e

]

x

y

z

θ

φ

|
E|

Ex

Ey


Ez

Electric field

Cavity and electrodes

structure

i.d. 90, length 958

cylindrical TM
010

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 m

V=350 m/s

t = 3.9 ms

Spatial Spread

of
39
K at the position
of the Resonant Cavity

V = 350m/s

t 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=145
mK

Summary




Obtained preliminary data of Stark Shift of
39
K


Constructed the Guiding Field system in the cavity.





More precise measurement of Stark Shifts of
39
K


Experimental testing of Guiding electric field


and sensitivity up to 10 mK


Designing and construction of laser cooling


apparatus for collimated bunched beam of
39
K Rydberg


atoms

Improvements in Progress

Present Status


Thank you




For



your kind Attention

Room Temp

39
K 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=
m
o
nIr
2
/2(r
2
+z
2
)
3/2

If separation is twice of the

Radius of the coil

B=

(4/5)
3/2
m
o
nI/r

Coil Radius (r)

=

30mm

Separation (z)

=

60mm

Number of turns

(n)=25

Current=3A

Required 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

0.53

micro
meter

53

micro

meter

Binding
energy

1/n2

1100cm
-
1

11cm
-
1

0.1m
-
1c

Period of
electronic
motion

n3

0.15pico
second

0.15ns

0.1micro
second

Polarizebi
lity

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

33000

v/cm

3.3

v/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/h

Cavity length=20cm

V=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
I
tot

Some Parameters
dependence of
39
K
Trap


1.
Number of Trapped atoms(N)


2.
Loading Rate Coefficient(l)


3.
Trapped atoms density(n)


4.
Loss Rate


I
tot
=220mW/cm
2

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 beam

e
-

0.15kV

1kV

CEM

Cross Sectional View

20K