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
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
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
Experience: CLIO – Prototype for LCGT
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 gain 103 at 4 Hz
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
NN reduction in caverns
Reduction factor
Cavern radius [m]
Spherical Cavern G.Cella
5 Hz 10 Hz 20 Hz 40 Hz
NN reduction of 104 @5 Hz with 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
Ultra soft vibration isolation: sensitivity at low frequency
Upper experimental hall
Credit: R.De Salvo
50-100 m tower to accommodate long suspension for
low frequency goal
Ellipsoidal/spherical cave for newtonian noise reduction 10 km tunnel
Working group 2
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.
ILC, NLC, Tesla, VLHC, Muon Source – Site requirements
Dusel in USA: NSF – July 10, 2007 – 15 M$ study
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
Logistics for FP7
Define detailed strategy in first WP1 meeting
FP7 foreseen resources
• 44 kEuro travel
• 1 postdoc for 3 years, 1 postdoc for 2 years
• 30 kEuro for external work
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
Discussion issues
Join the N2 network `Deep Underground Science Laboratories:
DLnet (0.8 MEuro)’.
