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www.minigrail.nl
Kamerlingh Onnes LaboratoryLeiden UniversityThe Netherlands
Arlette de WaardLuciano GottardiGiorgio Frossati
http://www.minigrail.nl
www.minigrail.nl
Kamerlingh Onnes LaboratoryLeiden UniversityThe Netherlands
Collaboration with:
RomePadovaSão Paulo
Twente
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www.minigrail.nl
• Large cross section compared withtraditional bar detector with L~5D
• Determine direction andpolarization (TIGA)
• Very short cool-down time• Cheap (< € 500k / antenna)
• Omni-directional
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www.minigrail.nl
Material CuAl6%
Density ρ = 8000 kg/m3
Diameter Φ = 0.65 m
Mass M = 1150 kg
Sound velocity v = 4000 m/s
Resonant freq. f = 3160 Hz
Operating temperature ~ 20 mK
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www.minigrail.nl
Sphere+ 6 transducers
7 damping stages
Dilution refrigerator
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www.minigrail.nl
T = thermodynamic temperature
β -1 = the ratio of the energy deposited into the detector andthat converted into electromagnetic energy in the transducer
Q = mechanical quality factor
TN = noise temperature SQUID
NN
Neff TQ
T
QT
TTT 2
2122
2
1
+≈
+≅
ββ
Minimum detectable energy kBTeff:
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www.minigrail.nl
Minimum detectable energy kBTeff:
NN
Neff TQ
T
QT
TTT 2
2122
2
1
+≈
+≅
ββ
HzhTkE NBN 3160with1 === νν
SQUID noise energy (quantum limit):
KT N 105.17−×≅
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www.minigrail.nl
NN
Neff TQ
T
QT
TTT 2
2122
2
1
+≈
+≅
ββ
KT N 105.17−×≅
710−<Q
T
β
β ~ 0.1 expected
Q ~ 107mKT 20~
measured
Minimum detectable energy kBTeff:
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www.minigrail.nl
mRl
kgMm
s
s
195.06.0
1150
====
sfml
kTH eff 24
21
40
2
min0
−×≈
=π
The Fourier transform H0(f ) of a burst h(t) of duration τgconsidered constant within the bandwidth ∆f assumingSNR=1 is:
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www.minigrail.nl
200 HffS h ∆= π
For SNR = 1:
2/10 )()(
~ −= HzfSh h
HzQT
Tff
N
2242
17.021
0 ≈
+=∆
ββwith
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www.minigrail.nl
4.7×10-231.5×10-224.7×10-224.3×10-211.3×10-214.3×10-20h0
230224224∆f
0.10.10.1β
4.5×10-74.5×10-64.5×10-5Teff
1.6×10-71.6×10-61.6×10-5TN
1 hυ10 hυ100 hυEN
Quantum limitAdvancedInitial goal
2/10 )(
−HzfS h
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www.minigrail.nl
MiniGRAIL
MiniGRAIL
∆f ~ 10% f
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MiniGRAIL narrow band
MiniGRAIL
∆f ~ 10% f
MiniGRAIL narrow band
∆f ~ 1% f
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www.minigrail.nl
MXylophone of spherical detectors
From 1 – 3 kHz:10 detectors with ↓ = 0.65 → 2 meters
∆f ~ 10% f
MiniGRAIL
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Xylophone of narrow band detectors
∆f ~ 10% f∆f ~ 1% f
MiniGRAILMiniGRAIL narrow band
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Arrays of spherical detectors
MiniGRAIL3 spheres CuAl6%
100 spheres100 spheres (↓ =1.2 m)
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Beryllium sphere
MiniGRAIL
Beryllium (↓ =2 m)
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www.minigrail.nl
• Cryogenics• Suspension• Transducer development
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www.minigrail.nl
• Repair leak in cryostat and testdr with continuous heat exchangers
• Install sintered heat exchangersand cool below 50 mK
• Test double stage SQUIDat low temperature
• Measure thermal noise MiniGRAILwith capacitive transducer
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www.minigrail.nl
→
→_____________________________
→
2Mvn
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www.minigrail.nl
2Mvn
1800
6537
7516
8000
2500
Density(kg/m2)
12000
5400
4668
4000
5400
Soundvelocity (m/s)
Crosssection
Diameter(m)
Material
38.83.06Be
2.61.38CuBe10%
1.41.19CuBe5%
0.71.02CuAl6%
11.38Al5056
Several spheres at 2 kHz
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www.minigrail.nl
3155 3160 3165 3170 3175
Frequency (Hz)
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www.minigrail.nl
www.minigrail.nl
0,01 0,1 1 10 100104
105
106
107
MiniGRAIL (φ = 65 cm)MicroGRAIL (φ = 17 cm)
Temperature (K) Tmin= 1.8 KelvinQmax= 950 000
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silver epoxy
WBW3k piezoCu wire↓ =400µm
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Nitrogen Dewar
Copper tube
N2
Roots 1200
Roots 250
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27 hours !
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Thermal anchoring of the massesof the suspension
To 600 mK plate
To 50 mK plate
To mixing chamber (20 mK)
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600 mK platestill1 K plate 1 K pot
50 mK plateMixing chamber
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Attenuation > 40 dBper stage 1
234567
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flat Nb coil2 stage SQUID
3 mode system
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Nb film Twente
Imax stored ~ 4 A
Icrit Nb film ~ 6 A
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Padova(2 stage )
Twente(2 stage)
Carelli(2 stage)
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