1. Characterization of the PArametric COnverter detector
Ilias
Task M3
“Investigation Of Superconducting Materials”

2. Renzo Parodi INFN-Genoa
Task Aim
Development of an innovative detector based on superconducting resonant cavities suitable for High Frequency Gravitational Waves (5-10Khz)
Proof of feasibility of the detector to ascertain the feasibility of the development of advanced superconducting RF detectors with high sensitivity.
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Renzo Parodi INFN-Genoa

3. Renzo Parodi INFN-Genoa
Detector’s Basics
The weak electromagnetic (EM) coupling between two equal RF cavities generates two Resonant Modes (symmetric and anti-symmetric on the fields) at slightly different frequencies f1 and f2. One of the modes is fed with RF power Pin [watt]
A gravitational wave of amplitude h deforms the cavities: when the G-Wave frequency W matches the frequency difference between the two modes W=(f2 -f1), a maximum RF energy transfer between the two modes occurs (parametric conversion) with output power
Pout~h2PinQel 2 [watt]
The detector is Tunable with constant sensitivity on a quite broad range of frequencies (~2-10KHz) by changing the RF coupling of the cavities not the cavity dimensions or mass.
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Renzo Parodi INFN-Genoa

4. Renzo Parodi INFN-Genoa
Prototype detector
A detector (inner radius of Niobium spherical cell ~0.1 m, thickness 2 mm) is designed and built.
The foreseen sensitivity is ~10-19 for a detector having the following parameters:
overall mass M ~ 4 kg
RF frequency ~ 2 GHz,
stored energy U ~ 10 J,
detection frequency range: 5 kHz < Fgw < 20 kHz.
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Renzo Parodi INFN-Genoa

5. Prototype construction
The cavity was built using the procedure established along the Task M3
using the tooling developed for the construction of the cavity mock-up
The prototype was delivered to the Genoa-INFN lab on October 16, 2006
Test started January
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Renzo Parodi INFN-Genoa

6. Renzo Parodi INFN-Genoa
Rf Charecterization
The Prototype was tested for the RF parameters in the Standard parallel Cryostat.
To reduce to a minimum the RF a Cryoperm ® magnetic shield was used.
The measured unloaded RF Quality factor was 4.7×1010 at a surface RF magnetic field of 56 mT, corresponding to 10J of stored energy, exceeding by a factor 4 the design Goal
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Renzo Parodi INFN-Genoa

7. Magnetic field (Gauss)
RF Results
Paco Cavity
Magnetic field (Gauss)
QL factor
Q0 factor (b 13) 35
5.5×109
7.7×1010
260
4.5×109
6.3×1010
560
3.4×109
4.7×1010
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Renzo Parodi INFN-Genoa

8. PaCo Detector RF System
Lock the the master RF oscillator to the resonant frequency of the cavity
Drive the coupled resonators purely in the symmetric mode and receive only the RF power up–converted by the perturbation of the cavity walls to the antisymmetric mode.
Cancel the contribution to the output of the detector produced either by the drive RF signal and by the common mode mechanical perturbation of the cavity walls.
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Renzo Parodi INFN-Genoa

9. Sensitivity enhancement RF System
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Renzo Parodi INFN-Genoa

10. Renzo Parodi INFN-Genoa
Results
Using the prototype
Parametric conversion Frequency ~7 Khz
100mm radius
4Kg
Qem ~ 3x109 (4.2 K)
Stored energy U~1 Joule
Quad Mechanical mode frequency~4KHz
Qmec ~ 103
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Renzo Parodi INFN-Genoa

11. Renzo Parodi INFN-Genoa
Results (Continued)
We get the signal reported for .1 V peak sinusoidal signal applied to the drive piezos.
Using a Room temperature low noise amplifier with 350K Noise temperature (0.6 dB Noise Figure)
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Renzo Parodi INFN-Genoa

12. Renzo Parodi INFN-Genoa
Detector Output
The demodulated Output of the PArametric COnverter operated at 4.2 K is reported
The conversion signal at the W=f2-f1 Frequency is clearly seen
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Renzo Parodi INFN-Genoa

13. Renzo Parodi INFN-Genoa
Detector sensitivity
The plot of the output of the PACO detector for 5 Volts Peak and 0 volt (no Drive) sinusoidal drive of the piezo are reported
The estimated strain sensitivity at 4.2 kelvin is shown on the same plot
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Renzo Parodi INFN-Genoa

14. Renzo Parodi INFN-Genoa
Conclusions
The Prototype of the PArametric COnverter detector is now Running at the design sensitivity as planned, without unforeseen surprises.
The construction thecnique chosen was proven adequate.
A suitable cavity manufacturer is selected and a second alternate supplier was still found.
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Renzo Parodi INFN-Genoa

15. The PACO Group INFN Genoa
Renzo Ballantini
Philippe Bernard
Renzo Parodi
Emilio Picasso
Renzo Vaccarone
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Renzo Parodi INFN-Genoa