Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

1

Options for interferometric monitoring of CLIC test magnet

M. S. Warden, P. A. Coe, D. Urner, A. Reichold

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

2

Outline

• Interferometers– Distance Meters– Compact Straightness Monitors

• Complementary to accelerometer readings

• Options for the CLIC test magnet– Sequence of instrumentation

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

3

Interferometer: Distance meter

Absolute distanceDisplacement

• Operates in two modes– Absolute Distance (< m resolution)– Displacement measurement (nm resolution)

• Two modes combined– Displacements referred to absolute distance– Tolerant to interruption of measurements

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Instruments: CSM• Compact Straightness Monitor• Example from ATF2

– Measures plane to plane• Internal displacements and rotations measured• CSM always blind to 6 external DoF

100 mm

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Interferometers: Make relative measurements

• Distance Meters measure point to point– Range and displacements ( changes)

• Compact Straightness monitor– Combines distance meters to measure object

to object• 3 translational degrees of freedom• 3 rotational degrees of freedom

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Compare and contrast with accelerometer

• CSM measures internal DoF– network distances between lines of sight– blind to external rotations / translations

• Accelerometer measures local deviations from free fall– multiple axes of test mass(es)– blind to free fall

• (local 1g can be cancelled off)

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Flexible range of options

• Interaction on CLIC is still in its infancy– No process yet for

• drawing up interferometer required specifications• understanding conflicting uses of space

• Initial discussions lead to “bizarre” first ideas• We envisage flexible programme

– First: making simple studies– Later: Installing more sophisticated systems

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Instrumentation could be staged

• Build up number of interferometers

– First study with simple distance meters• May increase number of distance meters

– Upgrade later to simple CSM arrangement

– Final stage complete suite of CSMs

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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First measure most important DoF

• Start with simplest interferometers– Distance meters (DMs)

• measuring the vertical coordinate wrt floor

– Learn which issues are most important

• Suitable reference datum• Structural Vibrations• Vacuum / Protected air

– Would compare with accelerometers• one accelerometer at each end of line

Reflector

Launch Head

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Monitor several points independently

Floor

Magnet• Test several points along the magnet– at first independent DMs

• Compare readings with accelerometers– on the magnet– and on the floor

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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These might be cross linked DMs

• Subject to constraints– we don’t know these

• Only possible– if planned in advance

• We would like to understand– what is possible– what is impossible– with respect to using spaces under/around the magnet

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Ultimately: Install cross linked CSMs

• With some form of enclosure– Although it need not take this form

Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC

CLIC stabilisation day 5 - LAPPOXFORD MONALISA

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Summary

• We propose a staged build up of interferometer installation

• Many DoF can be measured with CSMs

• Can learn a lot with simple instruments (DMs)– These can be installed as soon as magnet is ready– Would like to compare with accelerometers

• We need to better understand the constraints