s. chelkowskislide 1et meeting, hannover 01/2009

S. Chelkowski Slide 1ET Meeting, Hannover 01/2009

Overview

Introduction ET

Sagnac topology

Sagnac effect

Consequences for ET with Sagnac topology Static effects

Noise couplings Frequency noise

Seismic noise

Beam jitter noise

S. Chelkowski ET Meeting, Hannover 01/2009 Slide 2

ET

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ET

Triangular geometry Topology currently

undefined Michelson,Mach-

Zehnder, Sagnac, etc

Configuration currently undefined

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Sagnac topology

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Non-zero area Sagnac Near-zero area Sagnac

Sagnac interferometer and effect

Named after Georges Sagnac Correctly explained only with

General Relativity Rotational induced phase shift

S. Chelkowski ET Meeting, Hannover 01/2009 Slide 6

Original experimental setup from 1913

Ref:[1] G. B. Malykin, "The Sagnac effect: correct and incorrect explanations", Physics-Uspekhi, Vol.43, (2000), 1229-1252

[2] G. E. Stedman, "Ring-laser tests of fundamental physics and geophysics", Reports on Progress in Physics, Vol.60, (1997), 615-688

Location dependency

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Earth rotation

Detector location

Equator

Sagnac effect today

Lasergyroscopes are used for geodesic measurements to determine variations in the Earth rotation rate

Also used to do seismometry

Current sensitivity:

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Images with courtesy Laser Gyro Group Wettzell, Germany

Sagnac effect in ET

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Non-zero area Sagnac Near-zero area Sagnac

A A = B - C

B

C

Sagnac effect in ET

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Analysis involves two effects1.Static effects due to Earth’s rotation

Much more sensitive than current Laser gyros

2.Noise couplings• Frequency noise• Seismic noise• Beam jitter noise

Static Sagnac effect

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Location Strasbourg:

Arm length of 10km

Sim

ula

tion

para

mete

rs

No longer on dark fringe!33% of laser power lost in “dark” port

10km

A = B - C

B

C

Change arm length to 10068m to achieve dark port condition again!

Include Matlab figure which Shows the fringes?

Noise coupling analysis

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Our aim is

@ 10Hz

Hild et al., (2008) arXiv:0810.0604v2

How does strain sensitivity translates into Sagnac phase shift?

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Clockwise propagating beam:

Counter-clockwise propagating beam

10km

Noise couplings – Frequency noise

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Non-zero area Sagnac

Noise couplings – Frequency noise

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A = B - C

B

C

Near-zero area Sagnac

Noise couplings – Seismic noise

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10km

Non-zero area Sagnac

Noise couplings – Seismic noise

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A = B - C

B

C

Near-zero area Sagnac

Noise couplings – Beam jitter noise

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Noise couplings – Beam jitter noise

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10km

Non-zero area Sagnac

Noise couplings – Beam jitter noise

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Noise couplings – Beam jitter noise

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A = B - C

B

C

Near-zero area Sagnac

Conclusion

Two possible solutions for ET with Sagnac topology Non-zero area Sagnac Near Zero area Sagnac

Noise coupling analysis performed for both cases Near-zero area Sagnac performs better! Seismic noise and frequency noise coupling are fine Only beam alignment has stringent requirement

S. Chelkowski ET Meeting, Hannover 01/2009 Slide 22