The Aladin experiment: status and perspective

1
The Aladin experiment status and perspective

• Aladin is a cryogenic experiment aimed at
  measuring
• vacuum energy variations in a rigid cavity

• Measurement method measure of the magnetic
  field
• necessary to destroy superconductivity in a
  superconductive layer
• being part of a rigid Casimir cavity.

INFN (Istituto Nazionale Fisica Nucleare
Italy) INFM (Istituto Nazionale Fisica della
Materia Italy) IPHT (Institut fur Physikalische
HochTechnologie Germany)
E. Calloni Barcelona -
September 05 2005
2
Scientific motivations

• first demonstration of a phase transition
  influenced by
• vacuum fluctuations
• evaluation of zero-frequency transverse-mode
  contribution
• to Casimir energy
• Opening the way to different cavity geometries
• Long-Term ? Measurement of weight of vacuum energy

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Cosmological constant problem ? experimental
verification of applicability of General
Relativity to vacuum fluctuations
Force on a RIGID Casimir cavity in gravitational
field
A proper Area L proper length
From Casimir Cavity Minkowski ? gravitational
field
4
Gravitational Force on a rigid cavity
The force is positive (directed upward)
MULTILAYER and NECESSITY OF FORCE MODULATION

• Dielectric thickness 5 nm
• Number of layer N106
• Area 300 cm2
• h modulation factor 0.5

7
5
The Expected force compared with a Gravitaional
waves detector Virgo Sensitivity
1 month integration time
Present GW Sensitivity

Foreseen 2 years
And this has triggered us to search a method to
modulate Casimir Energy in a rigid cavity G.
Esposito QFEXT_01
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Modulation method normal metal-supercondutor
transition of a cavity plate
modulation factor with respect perfect
reflectivity
Plot of real part of conducibility s normalized
to zero frequency Drude conducibilty s0 for
different temperatures T Tc (Drude)
T/Tc 0.9 T/Tc 0.3
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Modulation magnitude
To evaluate its effect on the superconducting
transition we calculate the Free Energy FC.
Lifshtz theory for a three-layered system at
temperature T gives
where zl2p l kBT/h are the Matsubara modes.
For calculation details see G. Bimonte. talk
8
Orders of magnitude of Dh
Numerical Evaluation
D10 nm, L10nm, y05, Tc0.5 K, (1-T/Tc)0.1,
wp18.9 eV (Be)
When the mirror is superconducting it is like
the reflectivity was a bit higher
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Measurement method
Casimir lowers the free energy of the system
A 1 cm2
The change of free energy in the transition due
to condensation is Comparable with change of
free energy due to Casimir effect
Measured by measuring the thermodinamical
critical field Hc
The critical field Hc is measured and compared
with critical field of simple film. Statistic is
done with different dielectric thickness and film
thickness.
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Typical measurement of parallel critical field in
simple film
Tin D 287 nm
G. Robinson Proc. Phys. Soc 1966
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Expected behaviour for in-cavity film
t 410-13 s
Element Hc/Tc(Oe/K) wP(ev) Be
44 18.9 Al
89 11.9 Zn
54 11.3
t 110-13 s
t 0.99
The measurement is limited by sensitivity not by
accuracy !
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Parallel field on simple film
Cryostat Oxford Instruments HelioxVL 300 mK Al
300 nm film 100 mA ? 92 Gauss
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Plot versus
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Correction for nucleation and expected
three-layer signals
Residual lt 0.3 dt lt 0.5 mK
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Three-Layer Layout
Statistics 50 Structures 50 Au coated for
comparison on each structure Two different areas
on each structure
D 10 nm L 10 nm Au-layer 100 nm
Al2O3
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Short-term

• Measure sensitivity with Al three layer

First Run 12-September-2005
Most critical points ? - broader transition (10
nm) - low
RRR
Long Term 2 years

• - Reaching the desired sensitivity by
• Improving RRR in Al
• Using Zn films (experimental tests already
  started )
• Using Be films

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Conclusion
Aladin is aiming (trying) at

• Measuring energy variations in a rigid cavity
• Demonstrating the first transition influenced by
  vacuum
• fluctuations
• Contribute to clarify the effect of the Zero
  frequency
• transverse mode
• Open a (very) long term RD on the possibility
  to weight
• vacuum fluctuations

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References

• E. Calloni, L. Di Fiore, G. Esposito, L. Milano,
  L. Rosa, Int. Journal of Mod. Phys A , A17,
  804-807, 2002
•  
• E. Calloni, L. Di Fiore, G. Esposito, L. Milano,
  L. Rosa Phys Letters A, 297, 328-333, 2002
• G.Bimonte, E. Calloni, G. Esposito, L. Milano and
  L.Rosa, Phys. Rev. Lett. 94 (2005), 180402.
• G.Bimonte, E. Calloni, G. Esposito and L.Rosa,
  Nucl. Phys. B (in press) hep-th/0505200.