WP-M3 Superconducting MaterialsPArametric COnverter Detector INFN_Genoa Renzo Parodi
An innovative tunable detector based on superconducting resonant RF cavities is proposed. • The weak electromagnetic (EM) coupling between two equal RF cavities gives two RF Resonant Modes (symmetric and anti-symmetric in the fields) at slightly different frequencies f1 and f2.. • One of the modes isfed with RF powerPin[watt] • The key feature of the system is the High (~1011) Electromagnetic Quality Factor Qelof the cavities The detector – tuning system
The Electromagnetic behaviour The mechanical interaction with the G-Wave.
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 feasibility study results • Two pill-box niobium cavities mounted end-to-end and coupled through a small aperture on the axis • Working frequency 3 GHz • Mode splitting 500 kHz • Quality factor (e.m.) 2 109 @ 1.8K • Stored energy1.8 J • dL/L~10-20 Hz-0.5 @ 500 KHz • Two piezoelectric crystals A and B mounted on the end walls are used to simulate the g.w. Effects. A B
Starting from the small-scale prototype experience , a detector (inner radius of Niobium spherical cell ~0.2 m, thickness 5 mm) could be designed and built. • The foreseen sensitivity is ~10-20for a detector having the following parameters: • overall mass M ~ 45 kg • RF frequencie ~ 1 GHz, • stored energy U ~ 200 J, • detection frequency range: 2 kHz < Fgw< 10 kHz.
-19 10 hmin 6 x 10-21 h < 10-20 over 400 Hz (-1/2) [Hz] -20 10 (1/2) hh S -21 10 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 Frequency [Hz]
Main Outcomes • The new detection method, based on Radio Frequency cavities, is further developed to build a fully operational gravitational wave detector. • Superconducting RF cavities may be also used as transducers in the resonant detectors, as well in the selective read-out schemes. • The use of Niobium coated cavities will allow for a wide choice of materials (with High Mechanical Quality factor) and Refrigeration schemes, keeping to a minimum the cavity-coolant interaction and the coolant (LHe) inventory. • This last point will be beneficial in improving the detector sensitivity, further reducing the noise contribution of the cavity wall Thermal Fluctuations
Modified Facilities • Helium liquefier and equipment for cryogenic tests in the temperature range 1-300 K • RF test set-up in the frequency range 50 MHz – 20 GHz for materials and RF components • Design Tools and test set-up for Superconducting (S/C) RF cavities