Einstein gravitational wave Telescope Next steps: from technology reviews to detector design Andreas Freise for the ET WG3 working group 15.10.2009, 2nd.

Einstein gravitational wave Telescope

Next steps: from technology reviews to

detector design

Andreas Freisefor the ET WG3 working group

15.10.2009, 2nd general ET workshop, Erice

A. Freise A Freise, 2nd general ET workshop 15/10/2009

Slide 2

What will ET look like?

How many interferometers per site?

Quantum noise reduction

Alternative topologies

Practical considerations

Sensitivity Studies

List of reviews/reports

Discussion of trade-off study

Overview

In the ET design study we are soon reaching the milestones `Evaluation of XXX technique’ and then start the trade-off activity.


Slide 3

Detector Geometry

What will be the shape of ET?


Slide 4

Multiple Interferometers: the Triangle

Both solutions have an integrated tunnel length of 30 km, they can resolve both GW polarisations, feature redundant interferometers and have equivalent sensitivity.

The triangle reduces the number of end stations and the enclosed area!

[P Jaranowski et al, Phys Rev D 58 1998]


Slide 5

Geometry/TopologyHow Many Interferometers Arms per

Tunnel?

Picture by Jason Bacon used under a Creative Commons License

Rüdiger, Aspen 2007


Slide 6

Today's Michelsons in a Triangle

[S Hild]


Slide 7

Multiple Interferometers: a Xylophone

Low power (no thermal effects), cooled, long suspensions

High power, squeezing, LG modes, room temperature, `normal' suspensions

Maybe we can reach the target sensitivity easier by splitting the frequency range?

[S Hild et al, arXiv:0906.2655]


Slide 8

TopologyMain Driver: Reduction of Quantum Noise

[S. Hild et al, arxiv:0810.0604]

http://arxiv.org/abs/0810.0604

http://arxiv.org/abs/0810.0604


Slide 9

Quantum Noise Reduction

Optimised SR

[H. Rehbein und H. Mueller-Ebhardt, ET note ET-010-09 2009]

[S Chelkowski]


Slide 10


10dB frequency-dependentsqueezing


[S Chelkowski]


Slide 11


Variational output and10 dB squeezing


[S Chelkowski]


Slide 12


Sagnac with SR, variationaloutput and 10dB squeezing


[S Chelkowski]


Slide 13

Several QND topologies seem feasible: Micheslon with SR, variational output, squeezing Sagnac or Mach Zehnder Interferometer with SR, … Optical bars, optical levers, double optical spring, …

All can be build using the L-shape form factor!

QND Topologies

Optical Lever


Slide 14

Practical considerations

New technologies introducenew technical noises which might not be thought of in the first conceptual designs and have to be studied carefully.

Two examples …


Slide 15

Additional noise couplings: For Example: The Sagnac topology

Non-zero area Sagnac Near-zero area Sagnac


Slide 16

Sagnac effect in ET

Analysis involves two effects

1.Static effects due to Earth’s rotation

Much more sensitive than current Laser gyros

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

[S. Chelkowski, talk at WP3 meeting 01/2009]


Slide 17

Example: Seismic noise

Non-zero area Sagnac requirements on lateral mirror motion:

Zero area Sagnac requirements:

[S. Chelkowski, talk at WP3 meeting 01/2009]


Slide 18

Practical Considerations: Example, Beam Size


Slide 19

Interferometer topology selection will be driven by the quantum noise reduction scheme

All topologies can be build as an L-shape

We can assemble 3 L-shapes efficiently as a triangle

Multiple interferometers per site are beneficial for the sensitivity, yield redundancy and robust data analysis methods (null streams)

Technical details and noise couplings need to be investigated further before a topology can be selected

Summary of the overview


Slide 20

Sensitivity Studies

One of the WG3 tasks is to provide official sensitivity curves

See main ET webpage

Please use these for your studies and ask (email) if you have

questions!


Slide 21

Sensitivity Studies

The available data (currently internal to ET science team but should be opened): Plot as pdf file Data as .txt and .mat file Polynomial fit (coming soon)

These sensitivities are: Documented, version controlled, centrally stored data Generally discussed and accepted sensitivity examples

for activities such as trade-off studies These sensitivities are NOT:

Representing proposed ET detector options Always achievable using known technologies Taking into account detector geometry (triangle,

network effects,…)


Slide 22

Technology review

Technology review documented in internal notes and papers: Quantum noise reduction Detector geometry and topology High power lasers Parametric instabilities Diffractive interferometers Squeezed light Displacement noise free interferometry


Slide 23

Trade-off studies

Problem: New technology ideas are cheap, we have to stop

evaluating those at some point Everything depends on everything (e.g. thermal noise

on beam size, on free aperture, on tunnel size on available money): it is difficult to do trade-off studies with too many options

Proposal: Identify parameters/problems which can be separated,

such as the triangular shape from the QND topology For the rest, agree on one (maybe two) complete

design as reference and compute sensitivity, noise models, costs

Discussion now. Kick-off of dedicated activities in next WG3 meeting


Slide 24

…end


Slide 25

LL

45°

Fully resolve polarizations

5 end caverns

4×L long tunnels

45° stream generated by virtual interferometry

Null stream

Redundancy

7 end caverns

6×L long tunnels

60°

L’=L/sin(60°)=1.15×L

Fully resolve polarizations by virtual interferometry

Null stream

Redundancy

3 end caverns

3.45×L long tunnels L

Equivalent to

[Ruediger et al (1985), Freise et al, Class. Quantum Grav. 26 (2009)]

Einstein gravitational wave Telescope Next steps: from technology reviews to detector design Andreas Freise for the ET WG3 working group 15.10.2009, 2nd.

Documents

shape of et

et wg3

general et workshop

et design study

p jaranowski et

normal suspensionss

rehbein und

area sagnac requirements