ET- WG2 kick-off Meeting

1. ET- WG2 kick-off Meeting Fulvio Ricci Cascina, November, 7th 2008

2. Participants: • 1 - EGO (FRA-ITA) • 2 - INFN (ITA) • 3 - MPG (DEU) • 4 - CNRS (FRA) • 5 - University of Birmingham (UK) • 6 - University of Glasgow (UK) • 7 - VU (NL) • 8 - University of Cardiff (UK) + Science Team

3. WG2 - Mission • Pave the road to get the sensitivity of a GW detector as near as • possible to 1 Hz, by beating Newtonian and thermal noise • Underground • Passive and active seismic attenuation • Low dissipation materials for mirror suspensions • Cryogenics

4. Material Intrinsic losses requirements at low temperatures (12 Months – M12) Identify the materials with best properties for: Mirror Bulk, Mirror Coating, Mirror Suspension Wires Quantify the constraints from the thermal, optical and anelastic point of view and identify possible tradeoffs. Identify a possible R&D path to materials selection. Seismic Attenuation Requirements of the suspension (100 days – M26) Suspension seismic attenuation requirements (3 Months – M26) (input from site selection) Identification of control strategy and optimal mode frequencies for suspension elements An extended simulation of the suspension must be developed, where the best control strategy can be identified and tested. It is necessary to verify that the system has no mechanical modes which involve critical degrees of freedom and are not sensitive to the foreseen control loops.

5. Preliminary Conceptual Design of the overall Cryogenic Suspension (12 Months – M23): Upper Suspension preliminary Design: Active vs. Passive Super Attenuator (4 Months) Conceptual design of damping, alignment and control strategy (12 Months) Cryogenic compatibility of Upper Suspension Design (12 Months) Identify the constraints on the upper suspension elements due to the connection with the low temperature last stage elements. Identify a suspension interface between last stage element and suspension chain which minimize thermal conduction. Last Stage Suspension Preliminary Design Test Mass Requirements (460 days – M22) Test Mass Geometry and Size definition (Input from Optical Configuration) Test Mass Mechanical and Optical losses requirements (12 Months – M12) Test Mass Definition (4 Months – M23) Suspension Wires material and size choice (Input from Material Selection) Definition of last stage actuation strategy and technology Actuation and Sensing at low temperatures allow the use of superconducting techniques which are the lowest noise technologies available, at the cost of an increased complexity of the system and of the necessity to be at low temperatures to make it work. It is possible to design hybrid systems which could have traditional sensing and actuation, working also at room temperature, in parallel with superconducting low noise sensors, which could be used once the proper operating point of the antenna is reached.

6. Cooling Requirements and Cooling Strategy definition Identify the requirements on test mass temperature in order to have a negligible thermal noise, with respect to seismic, newtonian and radiation pressure noises. Identify the best cooling strategy (refrigeration only, cryogenic liquids, hybrid techniques) regarding: underground facilities safety and costs (input from site selection), power to extract from the test mass (input from mirror optical properties) noise input constraints Thermal Path definition and Thermal Links Requirements Identify the best possible path depending on the cooling strategy: tradeoff between the necessity to have a short thermal link and a very low frequency, (hence very long) connection of the mirror to the refrigeration apparatus. Identify the constraints on the acoustic attenuation chain for the thermal links. Thermal Links Conceptual design (3 Months – M24) Finalization of the conceptual design of thermal links attenuation chain, including the thermal contacts between refrigeration apparatus and last stage elements.

7. Thermal Noise Requirements for the Suspensions of the 3rd Gen ITF - Task ID 18 Material Intrinsic losses requirements at low temperatures Seismic Attenuation Requirements of the suspension (100 days – M15) Suspension seismic attenuation requirements (input from site selection) Identification of control strategy and optimal mode frequencies for suspension elements Preliminary Conceptual Design of the overall Cryogenic Suspension (360 days – M24) Upper Suspension preliminary Design: Active vs. Passive Super Attenuator (4 Months) Conceptual design of damping, alignment and control strategy (12 Months) Cryogenic compatibility of Upper Suspension Design (12 Months) Last Stage Suspension Preliminary Design (300 days - M24) Test Mass Requirements (3 Months – M13) Test Mass Definition (4 Months – M23) Suspension Wires material and size choice (Input from Material Selection) Definition of last stage actuation strategy and technology Cooling Requirements and Cooling Strategy definition (360 days - M26) Thermal Path definition and Thermal Links Requirements (6 Months - M21) Thermal Links Conceptual design (6 Months – M26) Finalization of the Conceptual Design of the Overall Cryogenic Suspension Month 1-33 Month 1-12 Month 1-15 Month 10-26 Month 12-26 Month 10-26 Month 10-24 Month 26-33

8. Outcome of the meeting: • Agreement on task list, reference person and involved groups • Periodic (bimonthly or quarterly) meetings • Encourage exchanges and coordination between groups and in particular in the Science Team

9. Definition of Tasks and involved Groups (to be completed) • Definition of substrates and coating properties at low temperature: Leading Groups: LMA, Glasgow, Firenze, Genova, Perugia, Trento Science team: Jena, Trieste • Design of Upper Suspensions: Leading Groups: Pisa - EGO • Design of Lower Supension Mechanics: Leading Groups: Roma1, Perugia, Pisa • Design of Cooling System: Leading Groups: Roma1, Roma2, Genova, Padova Science Team: ICCR – Japan(?) • Design of Lower Suspension Sensing and Actuation: Leading Groups: Roma2, Napoli, Pisa, Roma1, Science Team: Genova (Vaccarone), Trieste • Design of Lower Suspension Fibers: Leading Groups: Glasgow, Firenze, Perugia,

10. Activity organization of the WG2: • Meetings open to the entire ET community • Monthly phone or video meetings should include at least the reference scientists • Quarterly Face-to-Face Meetings of the WG2 group Brief report with activity highlights to be sent to the entire ETlist following each quarterly meeting

11. WG2 – Task and reference scientist list to be filled Definition of substrates and coating properties at low  temperature (XXXX,XXXX)  Design of Upper Suspensions (XXXX,XXXX)  Design of Lower Suspension Mechanics (XXXX,XXXX)  Design of Cooling System and impact on vacuum (XXXX,XXXX) Design of Lower Suspension Sensing and Actuation (XXXX,XXXX) Design of Lower Suspension Fibers (XXXX,XXXX)

12. The end

13. Current ILIAS-Strega activity @ Cascina

14. The Prototype of Cryogenic Payload installed at the EGO West hall @1.5 km

15. The Cryostat Full scale cryogenic payload (with silicon). 15