1. Pre-isolator Update 18 th MDI Meeting F. Ramos, A. Gaddi, H. Gerwig, N. Siegrist December 17, 2010

2. “State of the art” update Mechanical vibrations requirements: Velocity less than 500 nm/s (x,y,z), below 16 Hz and less than 100 nm/s above the 16 Hz band. Description: Separated tool platform vibro-acoustically decoupled from building and operator platform; Massive concrete pedestal (> 65 tons), suppressing frequencies above 25 Hz; Tool platform with passive mechanical damping, suppressing frequencies above 3 Hz; Active mechanical damping down to 0.5 Hz; Operator platform decoupled from tool platform. IBM/ETH Nanotechnology Center – Zurich Due to be completed by the spring of 2011 Yet another great example of a pre-isolator 2

3. Quick look at the numerical simulations of the pre-isolator’s performance (LCD Note 2010-011) 3

4. FE Model Layout Things missing in the model: Pre-alignment mechanics Final doublet’s geometries (using, for now, lumped masses with estimated inertias) Final doublet’s supporting structures (girders, etc.) Pre-isolator’s supports (using, for now, 1-D springs with appropriate stiffnesses) LumicalBeamcalQD0SD0MULTQF1SF1 4

5. Harmonic excitation in the vertical direction Vertical steady-state response at QD0 1 Hz 51.2 Hz Good performance above the first resonance peak Main eigenfrequency (design) Inner support tube (tunned) 5

6. Harmonic excitation in the horizontal directions Vertical steady-state response at QD0 0.05 0.32 There is a good decoupling between the different directions 6

7. Test set-up @ Point 5 (ongoing work) 7

8. Goals of the test Validate the results from the finite element model 8 Assess the influence of external perturbations in a noisy environment (workshop floor) Check for energy loss mechanisms (friction, plastic deformation,...) Evaluate the performance of a real system with the pre-isolator’s characteristics (heavy mass and low natural frequency) + + =

9. 9 40 ton dead-load 4 tapered steel beams 4 flexure hinges Support beams

10. Static Deformation 203 to 205 mm 205 mm The measured static deformation matches (within 1%) the results from the finite element model. 10

11. Vertical direction – Center dead-load/support beam 1.1Hz6Hz 12Hz A. Slaathaug – EN/MME 11 First resonance peak at 1.1 Hz (very close to the pre-isolator’s design goal of 1 Hz); Good behavior up to 5 Hz; Amplitude decreasing with ~1/ω^2 between 1.5 Hz and 5 Hz indicates very low damping of the set-up (below 1%); Above 5 Hz, higher order resonance peaks appear and degrade the performance of the set-up; WHY? Dynamic Performance

12. New simulations 12 using a detailed model of the set-up

13. Eigenfrequencies and Eigenmodes 1.1Hz6.7Hz 17.8Hz57.2Hz *Main vibration modes 13

14. Harmonic response in the vertical direction Vibrations in the longitudinal direction induce significant movement in the vertical direction (not the case for the actual design of the pre-isolator); Must combine the two effects to get an accurate representation of the set-up. 14 1 Vertical direction – Center of dead-load/ground (excitation in the vertical direction) Vertical direction – Center of dead-load/ground (excitation in the longitudinal direction)

15. Vertical direction – Center of dead-load Combined harmonic response in the vertical direction + A. Slaathaug – EN/MME Good match at frequencies up to 50Hz 15 Combine Simulated Measured

16. Harmonic response in the longitudinal direction A. Slaathaug – EN/MME Good match at frequencies up to 40Hz. 16 Longitudinal direction – Support beam/ground (excitation in the longitudinal direction) Simulated Measured

17. Harmonic response in the vertical direction The model doesn’t match the measure data above 40Hz. A. Slaathaug – EN/MME 17 Vertical direction – Support beam/ground (excitation in the vertical direction) Simulated Measured

18. Summary of things to address dead- load not “rigid” Flexure hinges added Support structure not “rigid” ±50 mm A. Slaathaug – EN/MME 18 Not valid if the dead-load isn’t “rigid” Additional higher order eigenfrequencies Insufficient stiffness in the longitudinal direction Uncertainty in the position of the sensors

19. Proposed changes Replace the steel supports by concrete blocks ; Add 4 sets of horizontal stiffeners to improve the longitudinal stiffness of the set-up; Change the distribution of the steel blocks that make up the dead-load to improve its internal natural frequency. 19

20. + Expected improvements 1.1Hz 1.3Hz 6.7Hz 17.8Hz 57.2Hz 8.7Hz 31.5Hz 72.7Hz 20 Isolation Initial design New design

21. Summary (1) When compared with the initial simulations, the first set of measurements made on the pre-isolator test set-up showed unexpected results in the mid to high frequency range; A refined F.E. model was created and the results match much better the measured data in low to mid range frequencies; High frequency data calculated using the average between sensors might not be usable due to the relatively low internal eigenfrequencies of the dead-load; 21

22. Summary (2) New measurements will be performed with a sensor placed at the center of the “dead load”, concrete blocks as a support to the set-up and horizontal stiffeners in the longitudinal direction; The good performance of the set-up at low frequencies is promising. Nevertheless, it should be acknowledged that this design, with its several high frequency modes, is not representative of the future final design of the pre-isolator. 22

23. News Following Holland@CERN exhibition, contacts were established with TNO Science & Industry; They developed a 6 DOF passive/active vibration isolation table top (Kolibrie); Includes innovations in sensor technology and placement. Current performance (transmissibility) Passive Passive+active 23