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Mining for imbh gravitational Waves Fabrizio Barone
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tarix | 15.08.2018 | ölçüsü | 2,11 Mb. | | #62502 |
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Fabrizio Barone Enrico Campagna Yanbei Chen Giancarlo Cella Riccardo DeSalvo Seiji Kawamura
Pushing the Low Frequency Limit of ground based GWIDs Three limiting noise sources impede GWID at Low Frequency - Newtonian Noise (NN, alias Gravity Gradient)
- Suspension Thermal Noise (STN)
- Radiation Pressure Noise (RPN)
All three can be reduced by means of an underground interferometer
Is gravity gradient going to stop us?
In LG-GWID the first limitation is Newtonian noise, followed by Suspension thermal noise and Radiation pressure noise
LF-GWID the lowest frequency feasible surface GW detector
Newtonian Noise NN derives from the varying rock density induced by seismic waves around the test mass It generates fluctuating gravitational forces indistinguishable from Gravity Waves It is composed of two parts, - The movement of the rock surfaces or interfaces buffeted by the seismic waves
- The variations of rock density caused by the pressure waves
Newtonian Noise How to shape the environment’s surface to minimize NN? The dominant term of NN is the rock-to-air interface movement
Cella Cancellation of NN If the cavern housing the suspended test mass is shaped symmetrically along the beam line and around the test mass tilting and surface deformations, the dominant terms of NN, cancel out - (with the exception of the longitudinal dipole moment, which can be measured and subtracted).
Cella Cancellation of NN The result is also fluctuating gravitational forces on the test mass
Cella cancellation of NN Larger caves induce smaller test mass perturbations The noise reduction is proportional to 1/r3 The longitudinal direction is more important =>elliptic cave
Cella cancellation of NN
Newtonian Noise gains Minimal (multiplicative) Gains ~ 104 from symmetry and size of cave Gain 101.5 in frequency (=> ~1 Hz) Now we can try kissing LISA
The physics, frequency reach
The physics, Universe range
Reducing the suspension thermal noise Noise ~ 1/√L Suspensions tens of meters long How to shape the facility to allow this?
Vertical cross section
How far can we turn the knobs? Large symmetric underground halls for NN Longer suspension wires for STN Large mass mirrors for RPN
For lowest frequencies, turn more the same knobs
Suspension thermal noise limitations Can make one more step improving the materials (silicon instead of fused silica) getting to 3-4 Hz After that, cryogenics or alternative solutions will be needed
You have never seen a seismic attenuation filter Gosh, where do you come from? I will show you one!
Mirror design - a way out A clear no action band is present
Summarizing An underground facility permits to overcome or reduce Newtonian, Suspension Thermal and Radiation Pressure Noise the three limitations for Low Frequency operation of GWIDs Going underground is a very attractive option to explore the IMBH Universe Chinese scientists got interested and have proposed to their government the construction of an underground GW detection facility CEGO
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