Stabilization of Focus at ATF2

David Urner

University of Oxford

ATF2 Meeting May 2006 2

StaFF→MonALiSA

Dr. David Urner Dr. Paul Cole Dr. Armin Reichold

Stephanie Yang(mechanical engineering)

Tony Handford(workshop)

Roy Wastie(electrical engineering)

StaFF Stabilization of theFinal Focus

→

MonALiSAMonitoring of Alignment

and Stabilization with high Accuracy

ATF2 Meeting May 2006 3

Interferometric Monitoring

• Develop 2 instruments:– Distance meter with nm resolution over 10m– Straightness monitor with nm resolution over

10m

Michelson mode: 1nm resolution relative distances

FSI mode: 1m resolution absolute distances

Distance meter:0.3 0.4 0.5

0

5

10

15

Am

plitu

de /

Arb

uni

ts

Length / m

ATF2 Meeting May 2006 4

= 7m

FSI Performance

=4m

• Using 5m conventional Michelson interferometer in air as reference.

• Running at small tuning speed• Tuning over small fraction of tuning range

ATF2 Meeting May 2006 5

Attaching Vacuum System Force-Free

Here attach vacuum tube for interferometerAttached to BPM.

Holds retro reflector.

Firmconnection

Strain Gauge• Needs bellow to allow motion of BPM– Vacuum causes a force

order of 100N!

• Develop small force vacuum mount using double bellow system.

• Allows small motion (~1 mm) of BPM-system

• Test stand to measure remaining (perpendicular) force on BPM frame. -1mm-3mm 1mm 3mm

1N

2N

-1N

0N

-2N

-3N

-3N

Force exerted on carbon frame (BPM)±1mm: < 0.5N/mm±3mm: < 0.8N/mm

Force exerted by perpendicular motion

ATF2 Meeting May 2006 6

A Straightness Monitor Made from Distance Meters

• Red lines: Distance meter. • Multilateration measure 6D coord. of A with respect to B.

A

B

ATF2 Meeting May 2006 7

A Straightness Monitor Made from Distance Meters

• Information related via central triangle

Floor node

A

B

Ceiling node 1Ceiling node 1

~2.5m

ATF2 Meeting May 2006 8

Compact Straightness Monitor

• Too big in perpendicular direction!• Develop compact version

– Need 2 devices to separate rotation from vertical translation. + length measurement

– Next step: Test different ideas

Pointsource

Retro

Mirror

Collimator

Fibre launchand readout

Long arm

Use reflection from fibreend as short arm

Distancemeter

ATF2 Meeting May 2006 9

Compact Straightness Monitor

• Too big in perpendicular direction!• Develop compact version

– Test different ideas

• Aspect ratio A/B is relevant• A 5m: B somewhere at 20cm – 50cm for 1nm

resolutions

BA

ATF2 Meeting May 2006 10

ATF2: Stabilization

• General strategy:– Use one active feedback system only, which can combine inputs

from several measurements• Difficult if active feedback system compete!

– Test of a system with several input measurements using StaFF setup that will be installed at ATF.

– Big question is where to locate the actuators to get best response

• Should consider a system moving beam with kicker rather than move Shintake monitor.– This is a feed forward system, which is easier to control than an

active feedback system.– Additional cost?– Do we introduce jitter by such a kicker, and how much?

ATF2 Meeting May 2006 11

Placement of MonALiSA monitoring system at ATF2

• Easiest if we have direct line of sight between FF quadrupole and Shintake monitor.– Which is the crucial element of Shintake monitor do

we have to monitor. • Are there several parts to monitor • Can we get optical access to the crucial element(s)

• We need room (30-50cm) above either the Shintake monitor or above the FF magnet– Probably easier to get above magnet.

ATF2 Meeting May 2006 12

Funding and Timeline

• We are currently preparing bids to get funding in the framework of LC-ABD – 1 postdoc 2007-2010– ½ DAQ expert– Resources in electronics engineering and

construction, mechanical design and workshop– Funds to develop prototype and final system for ATF2

• We expect to have a first system ready early 2009.– Any reason why we urgently should be ready earlier?

ATF2 Meeting May 2006 13

ATF2 Meeting May 2006 14

Distance meter simulation

• Simulation done with Zemax

• Use non-sequential mode– Take into account

polarisation → correct interference pattern

– Allows stray light analysis

• Allow analysis of chromatic aberrations

ATF2 Meeting May 2006 15

Simulated Interference Patters

ATF2 Meeting May 2006 16

Piezzo Driven Monitor

Detector

Detector

PZT

MovingMirror

Mirror

Mirror

Mirror

Splitter

Splitter

Splitter

Tuning laser

SinglePointmeasurement

980 1000 1020 1040 1060 1080

-4

-3

-2

-1

0

1

2

3

4

Phase stepping cycle

Laser is tuning continuously

Pha

se

/rad

ian

s

(Derive phases modulo 2from intensity data)

Moving mirror: Measure Intensity pattern

ATF2 Meeting May 2006 17

3–D mechanical model, detector side removed for clarity

ATF2 Meeting May 2006 180 10 20 30 40

-5

0

5

10

15

0 10 20 30 40-2

0

2

Te

mp

era

ture

ch

an

ge

/ m

K

Time / s

Re

f V

/ m

V

Time / s

Reference channels Thermometer channels

First Temperature Measurements