Pre-isolator & QD0 support modeling 5th WG5 Meeting F. Ramos, A. Gaddi, H. Gerwig, N. Siegrist September 7, 2010

Layout 1Presented by H. Gerwig at the 15th MDI Meeting – 16/07/10 | Drawings by N. Siegrist

FE Model Layout 2 Things missing in the model: Pre-alignment mechanics Final doublet’s geometries (using, for now, 3-D point 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

QD0 Support tube 3 The tuning of the tube´s eigenfrequencies led to the reinforced polygonal cross-section shown

Assumptions of the FE model 4 The pre-isolator mass is assumed to be made out of concrete and the remaining parts of stainless steel; The QD0’s yoke mass is supported by the inner tube while the coils’ mass is supported by the outer tube; Mass of the remaining elements extrapolated from QD0’s mass; Spring stiffness's tuned to yield fundamental eigenfrequencies of 0.7Hz and 1Hz in the horizontal and vertical directions respectively;

Main vibration modes 5 Mode # Frequency [Hz]

Harmonic excitation in the vertical direction 6 Vertical steady-state response at QD0 1 Hz 51.2 Hz Good performance above the first resonance peak

Harmonic excitation in the horizontal directions 7 Vertical steady-state response at QD There is a good decoupling between the different directions

Out-of-phase vertical excitation 8 GOAL: Assess the impact of non-coherent ground motion UY=sin(ωt-90) UY=sin(ωt) UY=sin(ωt+90)

9 Out-of-phase vertical excitation Vertical steady-state response at QD Hz Good performance despite the “lever arm” effect

10 Random vibration response Ground motion measurements at CMS (A. Kuzmin – EDMS ) Vertical ground YB0

Random vibration response 11 Vertical ground CMS-YB0 Vertical QD0

Random vibration response 12 Vertical ground CMS-YB0 Vertical QD0 4 Hz 2.9 nm 0.1 nm Reduction in r.m.s. displacements by a factor 30 above 4 Hz

Summary A detailed FE model of the pre-isolator and support tube was created; The main eigenfrequencies where chosen to be 0.7Hz and 1Hz in the horizontal and vertical directions respectively, to match the specifications of commercially available mounts; QD0’s support tube was tuned to have an eigenfrequency around 50Hz (51.2Hz); The harmonic analysis shows the system’s good vertical isolation performance above the first resonance peak while assuring a good decoupling between the different directions; The random vibration analysis confirms the good performance of the system, yielding a reduction by a factor 30 in r.m.s. displacements above 4Hz; The model will need to be improved with the addition of detailed geometry for the magnets, forward calorimeters, supporting girders, pre-alignment mechanics, etc.. 13

Spare Slides

Mode #1Mode #2 Mode #3Mode #4

Mode #5Mode #6 Mode #7Mode #8

Mode #9Mode #10 Mode #11Mode #12

Mode #13Mode #14 Mode #15Mode #16

Mode #17Mode #18 Mode #19Mode #20

Harmonic excitation in the vertical direction Steady-state response at QD0 in the transversal direction Steady-state response at QD0 in the beam direction

Harmonic excitation in the horizontal (transversal) direction Steady-state response at QD0 in the transversal direction Steady-state response at QD0 in the beam direction

Harmonic excitation in the horizontal (beam) direction Steady-state response at QD0 in the transversal direction Steady-state response at QD0 in the beam direction

Random vibration response at QD0 Excitation in the transversal direction Excitation in the beam direction Ground CMS-YB0 Vertical direction Beam direction Transversal direction Ground CMS-YB0 Vertical direction Beam direction Transversal direction