MONALISA

09:40 – 10:00 (JST)Wed 5 Mar 2008

MONALISA : JAI OxfordMDI ATF2 TILC08 Sendai Japan

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MONALISA

Laser based alignment and stability monitoring

09:40 – 10:00 (JST)Wed 5 Mar 2008


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The Oxford MONALISA Group

David Urner

Paul Coe

MatthewWarden

Armin Reichold

GeoffreyRayner

MPhys

alumnus

• Interferometer experience at Oxford – built up since mid 1990s

• Interferometer based alignment is "coming of age"– Key results imminent from 3 interferometer groups– IWAA 08 presentations http://www-conf.kek.jp/iwaa08/

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Interferometers: Best of old & new

• In 2008 we have– laser sources– fibre amplifiers– fibre coupling

• Enabling – radiation tolerance– cost effective– scaleable– rapid read out

High precision in fundamental physics since 1887

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Why 2008 is so exciting for us• MONALISA enjoying fruitful

collaboration in Oxford:– LiCAS

• Prototype rapid survey system

(tests in DESY)

– ATLAS: SCT optical alignment• being completed at CERN

• The whole is greater than the sum of the parts

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Beam based feedback• Is essential for ILC, CLIC• Requires an operational

beam– prerequisite initial alignment– components move after

survey • Working alignment needs to be maintained / restored

– between trains• 200 ms is long enough for several 100 nm movement

– after push-pull events: • IR hall floor will move after rolling two heavy detectors

– after shutdown periods

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Component Alignment Challenge

• relative mechanical DoF between many neighbouring components– choose important rotations / displacements

• in-situ– hostile radiation environment– cramped spaces

• ILC, CLIC require large dynamic range• (sub) nm precision over range of metres• micron precision over many 10s of metres

09:40 – 10:00 (JST)Wed 5 Mar 2008


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MONALISA: Benefits 1

Monitoring fiducial locations on key components

• after interruption of beam– independently follows changes in alignment

• during commissioning / start up – improves understanding of machine behaviour

• before accelerator operation– speeds up initial convergence of machine

09:40 – 10:00 (JST)Wed 5 Mar 2008


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MONALISA: Benefits 2

Return detector / QDzero position after push-pull

• expect to get micron repeatability – for return of magnet positions

• get machine within beam based capture range – improves switchover time

• more reliable accelerator operation– lower chance of damage– luminosity can only win

09:40 – 10:00 (JST)Wed 5 Mar 2008


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MONALISA : Requirements

• The ideal for any survey/monitor system – measure distances along clear lines of sight– use evacuated narrow tubes

• MDI issues for detector LoI – issues broadly as discussed here at SENDAI in

Tuesday MDI session– e.g. push pull vacuum connections

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Personal comments to add to Sendai meeting MDI discussion

• QD zero in tunnel scenario very exciting– MONALISA (as other systems)

• much simpler / cheaper• much easier to achieve target performance

– Personal plea to consider it favourably– IMHO:

• Achievable luminosity probably greater with simpler ILC

09:40 – 10:00 (JST)Wed 5 Mar 2008


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MONALISA illustration

• Returning to buried QDzero scenario

• following sequence shows an ILC study

– simulated example geometry

– compact straightness monitor (CSM) • concept arises from necessity

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Geometry

Measure movement of QD0s with respect to some points radially outwards through detector field yoke

Then must measure the relative motion of these end points

Exact geometry to be determined in synch with detector design

Final Vertically Focussing Quadrupole

Solenoid return yoke

Distance Meter

Straightness Monitor

Detail for single QDzero

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Geometry

Measure movement of QD0s with respect to some points radially outwards through detector field yoke

Then must measure the relative motion of these end points

Exact geometry to be determined in synch with detector design



Straightness monitor concept

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Geometry

Extension into tunnels possible. Allows monitoring of other magnets positions with respect to QD0



09:40 – 10:00 (JST)Wed 5 Mar 2008


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Measurement lines

We measure distances along measurement lines using two techniques:•Absolute distance interferometry•Displacement interferometry

Each line is the same, and is capable of performing both types of measurement.

Absolute distanceDisplacement

09:40 – 10:00 (JST)Wed 5 Mar 2008


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FSI: Frequency scanning Interferometry

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Interferometer operation

Intensity

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Interferometer operation

Phase = 2π (Optical Path Distance) / Wavelength

Φ = 2π D / λ = 2π D (ν / c)

D = (c/ 2π) (ΔΦ/Δnu)

R = (c/ 2π) (Δθ/Δnu)D = R (ΔΦ/Δθ)

ΔD = (c/2π ν) ΔΦ

Fixed Frequency Interferometry

Frequency Scanning Interferometry

09:40 – 10:00 (JST)Wed 5 Mar 2008


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FSI: recent results in airMHzrawsignal

=750nm=70nm

Add box to reduce air turbulence

Distance RMS < 1m

09:40 – 10:00 (JST)Wed 5 Mar 2008


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FFI: recent results in air

0 200 4000.2

0.4

0.6

0.8

1.0

Ph

oto

dio

de

sig

na

l / a

.u.

time / ms

0 200 400

-4

-2

0

Dis

pla

cem

en

t / m

Time / ms

Following displacements

5 nmRMS

Fourfibres'rawsignal

Displacement

Static resolution estimate

MHzrawsignal

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Up coming work at Oxford

• Have vacuum vessel ready for testing interferometers down to below 1 mbar

• Frequency stabilised ultra-narrow linewidth laser will improve reliability of FFI displacement measurements

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Vacuum Vessel (0.1-1mbar)Equipped with 4 x 8 way fibre

AFTER

BEFORE

800mm

LID NOT SHOWN HERE!

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Rb-87 frequency reference (FFI)

Laser Erbium doped fibre amplifier

Tuning Piezos

Photodiodes

Stabilised laser outputat 1560 nm

Residual1560 nm

Freq doubled at 780 nm

RF Amp

Lock-in amplifier

Summingcircuit (2)

Differencecircuit (5)

Summingcircuit (1)

Attenuation & phase shiftcircuit (3)

Stable DC level

PBS

NPBS 50:50

HWP

Dump

Dump

Dump Rb vapour cell

PBS

Stable DC level0 to 200 V

RF VCO (4)

Acousto-Optic Modulator

Periodically poledLiNbO3 (PPLN)

Tuning Input

1W Dichroic Mirror

Mirror

Mirror

Mirror

+-

f3f

• Target ~3 khz linewidth• Need 19 kHz for 1nm @ 10m

Almost all equipment has been ordered or purchased : setting up from March on

09:40 – 10:00 (JST)Wed 5 Mar 2008


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ATF2 extraction line: 08 Feb 2008

QD0

QD1

09:40 – 10:00 (JST)Wed 5 Mar 2008


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ATF2 beam direction

QD0

Shintaketable

ATF2: Monitor relative vertical motion

09:40 – 10:00 (JST)Wed 5 Mar 2008


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Summary

• MONALISA will be a boon to ILC– QDzero nanometre vertical alignment– Repositioning after push-pull to microns

• Needs to be included in MDI engineering and detector layout– push to get MONALISA concepts into detector – greatly encouraged by creative thinking at TILC08

• Performance demonstrations on going– Oxford: Vacuum and frequency reference systems– ATF2: Final focus monitoring system to be installed

Documents

MONALISA