Transcript Document

FPUA2010
Improving the detection
sensitivity
of dark-matter axion
search
with a Rydberg-atom
single-photon detector
M.Saeed
For
newCARRACK Collaboration
Kyoto
newCARRACK Collaboration
T. Arai, A. Fukuda, A. Matsubara,
T. Mizusaki, A. Sawada,M.Saeed:
Research Center for Low Temperature
and Materials Sciences, Kyoto University
Arai, A.
A. Matsubara,
S.T.
Ikeda,
K. Fukuda,
Imai, T. Nakanishi,
Mizusaki, A. Sawada,M.Saeed:
Y. T.
Takahashi:
Research
Center
for Low Temperature
Department
of Physics,
Kyoto University
and Materials Sciences, Kyoto University
Ikeda, K.
Y. S.
Isozumi,
T. Imai,
Kato,T.D.Nakanishi,
Ohsawa,
Takahashi:
M.Y.Tosaki:
Department
of Physics,
Radioisotope
Center,Kyoto
KyotoUniversity
University
Isozumi, T. Kato, D. Ohsawa,
K.Y.
Yamamoto:
M. Tosaki:
Radioisotope
KyotoEngineering,
University
DepartmentCenter,
of Nuclear
Kyoto University
Yamamoto:
H.K.
Funahashi,J.Uda:
Department
of the
Nuclear
Engineering,
Institute for
promotion
of excellence in
Kyoto
University
higher education, Kyoto University
Funahashi,J.Uda:
Y. H.
Kido,
T. Nishimura, S. Matsuki:
Institute
for theof
promotion
excellence in higher
Department
Physics,ofRitsumeikan
education
Kyoto University
University
Y. Kido, T. Nishimura, S. Matsuki:
Department of Physics, Ritsumeikan University
Contents
(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
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 “Dark Matter”.
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
10-6[eV] < ma < 10-3[eV]
240[MHz] < f < 240 [GHz]
Principle of the Kyoto Rydberg-atom single-photon detector
Primakoff effect
Rydberg atom
γ
np1/2
｜e 〉
｜ｇ 〉
ns1/2
Axion
Schematic
Diode laser
455nm
4p3/2
B0
Diode laser
766.7nm
4s1/2
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
Ｌｏｗｅｒ ｓｔａｔｅ ｜ｇ＞
Ｕｐｐｅｒ ｓｔａｔｅ |e＞
Dilution
fridge
Whole System
Laser
Electron multiplier
electron
mirror
Field
ionization
electrodes
7T
magnet
Liquid Helium
Metal posts
for tuning
Atomic beam
Dilution fridge and selective field
ionization detector
Laser set up
Electron
multiplier
Top view of the Dilution Fridge
Selective
Field
ionization
region
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
111
111P
111
111S
111S
Upper state
Lower state
111P
p
st
Measurement of blackbody radiations
in a resonant microwave cavity
sa
2527 MHz
st
p
sa
SQL Limit
st
p
sa
M. Tada et al., Phys. Lett. A 349(2006)488
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
39K
H.Haseyama et al J.Low Temp Phys150 549(2008)
85Rb
Experimental data of Stark shift in 39K for n=102
39
s-p energy difference [MHz]
3100
K: n =102
3000
2900
2800
0
10
20
30
40
Electric field [mV/cm]
Red solid circles : Preliminary experimental data for the s1/2 to p3/2 transitions
open circles : those for the s1/2 to p1/2 transitions.
More Precise measurements are in Progress
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(2):
Cavity and electrodes
excitation point
Guiding electric field
x=0,y=0
40
cavity
Electric field [ mV/c m]
30
SFI box
Cavity electro-magnetic field: TM010
|E|
y
20
Ey
Stark field direction
10
0
field direction
Ex
-10
-20
-30
E
Ez
-40
excitation point
atomic beam
x=0,y=0
100
cavity
SFI box
z
φ
Angle [degree]
z
SFI electrodes
50
θ
y
0
x
θ
φ
-50
-100
50
100
150
z [mm]
200
cavity
M.Shibata et al J.Low Temp Phys 151 1043(2008)
Stark electrode
electrodes for
field rotation
Cavity and electrodes
structure
i.d. 90, length 958
cylindrical 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.
Improvements(3):
Laser cooled bunched beam
T=145mK
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 39K 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
Summary
Present Status
Obtained preliminary data of Stark Shift of 39K
Constructed the Guiding Field system in the cavity.
Improvements in Progress
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
Thank you
For
your kind Attention
Omit this slide
-
Anti Helmotz coils
sLaser Beams
s+
Room Temp
39K source
Ion Pump
C.Monroe et all
Phy.Rev.Lett,65,1571(1990)
s-
B=monIr2/2(r2+z2)3/2
If separation is twice of the
Radius of the coil
B= (4/5)3/2monI/r
Coil Radius (r) = 30mm
Separation (z) = 60mm
Number of turns (n)=25
Current=3A
Required Field Gradient=0.20T/m
Anti -Helmholtz coils
s-
s+
I
sz
y
x
s+
sI
s+
n=10
n=100
n=1000
0.53
micro
meter
53
micro
meter
Mean
radius
n2
53A0
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 n7
lity
0.2
0.2x107
0.2x1014
Spacing
between
adjacent
level
n-3
200cm-1
0.2cm-1
2x104cm-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 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.
Cross Sectional View
CEM
20K
1kV
0.15kV
eShibata et al.,
Rev.Sci.Inst. 74(2003)3317.
atomic beam
33