FF magnets pre-isolator & experimental set-up proposal

FF magnets pre-isolator & experimental set-up proposal 2nd WG5 Meeting F. Ramos, A. Gaddi, H. Gerwig, N. Siegrist April 20, 2010

Objective Stabilize FF magnets to: 0.1 nm RMS @ 4 Hz Using an integrated approach: - passive pre-isolator - active mechanical stabilization - beam-based stabilization 1

Pre-isolator – How does it work? Low dynamic stiffness mounts (nat. frequency around 1 Hz) Acts as a low-pass filter for the ground motion + Large mass (50 to 200 ton) Provides the inertia necessary to withstand the external disturbances (air flow, acoustic pressure, etc.) 2

How can it be accomplished? 3 Drawings by N. Siegrist *Conceptual design

How can it be accomplished? QF1 Walk-on-floor QD0 QD0 support tube Mass Mount 4 *Conceptual design

“State of the art” example Vibration isolation system at the Centre for Metrology and Accreditation – Helsinki, Finland 4 independent seismic masses (3x70 ton + 1x140 ton) 0.8 Hz pneumatic vibration isolators (“air springs”) 5 *Infos provided by

“State of the art” example Provided measurement data Transmissibility Vertical displacements @Mass 10x @Ground 1 Hz Note: Ground motion noise level below CMS measurements (A. Kuzmin – EDMS 1027459) 6 *Infos provided by

Experimental set-up – Why? The previous example is promising, but... Is the system’s performance amplitude dependant? How will it react to different noise sources? And air blows? What about energy loss mechanisms (friction...)? What performance can we expect? There are lot of unanswered questions. We need to unequivocally demonstrate that the concept can work 7

Experimental set-up – How? It needs to be: Simple to design/build/assemble Easy to “debug” & tune Cheap Proposal: 40 ton mass supported by 4 structural beams 8

Experimental set-up – How? Drawings by N. Siegrist 9

Experimental set-up – Design Average stress: <280 MPa Deformation: 187 mm Design criterias: High deformations (i.e. low bending stiffness) Acceptable stresses Shape optimization 10

Experimental set-up – Performance Performance in ideal conditions (ground motion only) 1.55 Hz @CMS @Pre-isolator Transmissibility Displacement P.S.D. 2.2nm @CMS Displacement @Pre-isolator Ground Motion 15x 0.15 nm @Pre-isolator Integrated R.M.S. Displacement 11

Experimental set-up – Measurements A set-up like the one below is foreseen Measure Reference 1 Reference 2 ~10 m At least 3 seismometers/geophones Synchronous measurements Help needed for the measurements 12

Summary • A passive low-frequency pre-isolator has been proposed as a support for the FF magnets; • This pre-isolator will constitute the first “layer” of the stabilization chain; • This concept has already been used in other facilities; • Experimental tests should be performed to understand how the system behaves in “real life” conditions (no simulation can, accurately, take into account all these effects); • A simple and relatively inexpensive experimental set-up has been conceived and proposed. 13

FF magnets pre-isolator & experimental set-up proposal