1. 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

2. LISA Rüdiger, ‘85  Improved sensitivity compared to LIGO and Virgo – Sensitivity below 10 -24 m/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

3. LISA 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

4. LISA Experience: CLIO – Prototype for LCGT

5. LISA 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 10 2 overall gain 10 3 at 4 Hz

6. LISA 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

7. LISA NN reduction in caverns Reduction factor Cavern radius [m] Spherical Cavern G.Cella 5 Hz 10 Hz 20 Hz 40 Hz NN reduction of 10 4 @5 Hz with a 20 m radius cave 10 6 overall reduction (far from surface) (Compression waves not included) 10 2 less seismic noise x 10 4 geometrical reduction Compression waves: R. De Salvo

8. LISA 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

9. LISA 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.

10. LISA ILC, NLC, Tesla, VLHC, Muon Source – Site requirements

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

12. LISA 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

13. LISA Logistics for FP7 Define detailed strategy in first WP1 meeting

14. LISA FP7 foreseen resources 44 kEuro travel 1 postdoc for 3 years, 1 postdoc for 2 years 30 kEuro for external work

15. LISA Summary  Site selection for 3 rd 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

16. LISA 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

17. LISA Possible strategy  Join the N2 network `Deep Underground Science Laboratories: DLnet (0.8 MEuro)’.