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

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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

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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