Pre-isolator & QD0 support modeling5th 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)

Lumical Beamcal QD0 SD0 MULT QF1 SF1

QD0 Support tube

3

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

630

493

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]

1 0.422 0.493 0.704 0.705 0.796 1.007 14.298 21.699 22.08

10 33.5311 45.0312 51.1913 61.6714 63.6115 69.7416 70.6817 70.7818 77.1319 89.5620 105.57

Harmonic excitation in the vertical direction

6

Vertical steady-state response at QD0

1 Hz

51.2 HzGood performance above the first resonance peak

Harmonic excitation in the horizontal directions

7

Vertical steady-state response at QD0

0.05

0.32

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 excitationVertical steady-state response at QD0

0.49 Hz

Good performance despite the “lever arm” effect

10

Random vibration response

1 10 100Hz

OOR

OOR

OOR

OOR

1000z

10a

100a

1000a

10f

100f

1p

10p

((m)²/Hz)

GP_Ref (V)GP (V)

Ground motion measurements at CMS (A. Kuzmin – EDMS 1027459)

Vertical ground motion @ YB0

Random vibration response

11

Vertical ground motion @ CMS-YB0

Vertical motion @ QD0

Random vibration response

12

Vertical ground motion @ CMS-YB0

Vertical motion @ 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 #1 Mode #2

Mode #3 Mode #4

Mode #5 Mode #6

Mode #7 Mode #8

Mode #9 Mode #10

Mode #11 Mode #12

Mode #13 Mode #14

Mode #15 Mode #16

Mode #17 Mode #18

Mode #19 Mode #20

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

Steady-state response at QD0 in the beam direction

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

Steady-state response at QD0 in the beam direction

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

Steady-state response at QD0 in the beam direction

Random vibration response at QD0Excitation in the transversal direction

Excitation in the beam direction

Ground motion @ CMS-YB0

Vertical directionBeam directionTransversal direction

Ground motion @ CMS-YB0

Vertical directionBeam direction

Transversal direction