Design study for 3rd generation interferometers Work Package 1 Site identification and infrastructure

Jo van den Brand

e-mail: jo@nikhef.nl

Tübingen, October 9, 2007

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Rüdiger, ‘85

Improved sensitivity compared to LIGO and Virgo

– Sensitivity below 10-24 1/sqrt(Hz)– Ultra-low frequency cut-off

Underground site Multiple interferometers

– 3 interferometers; triangular configuration?

– 10 km long arms– 2 polarization + redundancy

Design study part of FP7 & ILIAS

Site identification issues: science

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Seismic displacement noise

Seismic displacement noise – Driven by wind, volcanic, seismic activity– Ocean tides, cultural noise (e.g. humans, cars)– Ground-water variations– Complicates operation of ITF, certainly in future

designs with high finesse cavities– Active control systems, seismometers feedback to

mirrors Underground

– Surface and compression waves– Die exponentially with depth

Surface waves

Compression waves

Courtesy: G.Cella

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Experience: CLIO – Prototype for LCGT

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Experience: underground interferometers LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved

from Mitaka (ground based) to Kamioka (underground)

Seismic noise much lower:

Operation becomes easier

102 overall gain103 at 4 Hz

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Gravity gradient noise

Gravity gradient noise– Time varying contributions to Newtonian

background driven by seismic compression waves, ground-water variations, slow-gravity drifts, weather, cultural noise

– Determines low-frequency cut-off– Cannot be shielded against

Counter measures– Network of seismometers and development of

data correction algorithms– Analytical studies: G. Cella

– Numerical studies

Figure: M.Lorenzini

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NN reduction in caverns

Reductionfactor

Cavern radius [m]

Spherical CavernG.Cella

5 Hz10 Hz20 Hz40 Hz

NN reduction of 104 @5 Hzwith a 20 m radius cave

106 overall reduction (far from surface)

(Compression waves not included)

102 less seismic noise x 104 geometrical reduction

Compression waves: R. De Salvo

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Ultra soft vibration isolation: sensitivity at low frequency

Upper experimental hall

Credit: R.De Salvo

50-100 m tower to accommodatelong suspension for low frequency goal

Ellipsoidal/spherical cave fornewtonian noise reduction

10 km tunnel

Working group 2

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Other criteria

Site selection and evaluation– Site availability and acquisition risk

– Acquire land rights in reasonable time frame– Scientific suitability

– Various noise sources– Construction suitability

– Geological conditions (topography, hydrology)– Environmental considerations– Legal issues– Earthwork costs (local soil waste, labor costs)

– Operations suitability– Supporting technical infrastructure (local University support)– Nearby communities (travel time, schools, etc.)– Operation costs (power, utilities, etc.)

– Risks from environmental sources or future development – Future developments (noise sources)– Earthquakes, etc.

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ILC, NLC, Tesla, VLHC, Muon Source – Site requirements

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Dusel in USA: NSF – July 10, 2007 – 15 M$ study

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Site identification

Gran Sasso

Salt mines

Geological issues – Collaborate with earth science

community– Roma 3, VU Amsterdam

– Perform seismic measurements– Salt mines, granite

– Geotechnical site reports

– Existing mines / tunnels– Horizontal site access

Cost issues– Excavation costs

– Equipment costs

– Crushed rock disposal

Infrastructure– Vacuum, cryogenics

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Logistics for FP7

Define detailed strategy in first WP1 meeting

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FP7 foreseen resources

• 44 kEuro travel • 1 postdoc for 3 years, 1 postdoc for 2 years• 30 kEuro for external work

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Summary

Site selection for 3rd generation ITF – Underground site– Seismic activity, gravity gradient noise– Numerous technical issues

Collaborative design study– Interest expressed by

– Caltech - LIGO– CNRS - Annecy– EGO– Florence – GEO600– Gran Sasso – Nikhef / VU– Pisa– Roma 1, 3

– Start regular meetings (as soon as EC formalities are completed)– First meeting at Gran Sasso (E. Coccia)(Underground Lab. Community)

Contact me: jo@nikhef.nl

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Discussion issues

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