Welcome to MONALISA

A brief introduction

Who we are...

David Urner

Paul Coe

MatthewWarden

Armin Reichold

Electronics support from CEGCentral Electronics Group

...also collaborate closely with the LiCAS project

The context of our work

• HEP High Energy (particle) Physics

• Linear accelerators

• Need for alignment monitoring

• ATF-2 Advanced Test Facility

• An envisaged monitor system

• Five summer projects

High Energy "Frontier"

• To "boldly" accelerate particles in large numbers

• Nature does this already:accelerated particles strike the earth

continuously as cosmic rays– but the results are hard to monitor– there's no control over the particles

Collaborations of physicists build: • accelerators to collide beams and • detectors to monitor the results

Exploring natures spectrum• Particle on particle centre of

mass energy is the spectral variable.

• Collisions between beams excite resonances

• Particles are created• The resulting debris is

– detected– filtered and – recorded for analysis

Linear accelerators• Bunches of particles travel

kilometres in evacuated tube along a tunnel

• Bunches kept tightly focused using magnet "doublets"

• Pumped by energy in RF cavities through which they travel

Example RF accelerator cavity

Proposed ILC

• 30 km International Linear Collider (e+ e-)

• Electron against Positron collisions

• (Particle) Physics programme complements LHC – Large Hadron Collider at CERN

• Beam energy can be tuned up to 500 GeV and later up to 1 TeV

e+

Positron

The ILCs functional elements

main linacbunchcompressor

dampingring

source

pre-accelerator

collimation

final focus

IP

extraction& dump

KeV

few GeV

few GeVfew GeV

250-500 GeV

One half of a linear collider

Electrons bunches are accelerated along a 12km main linac

Focused here

Collide here300 x 6 nmspot size

To see rare particlesthey need particle collisions with tightly focused beams

What do physicists want from the international linear collider?

Large aspect ratio, few 100 nm x few nm......and they must be made to collide!

Detector

Axial view of beams at the focuselectrons

positrons

Machine performance : Luminosity

InteractionPoint

Final focusquadrupolemagnet

• One shot with each bunch!• Most electrons in a bunch do NOT produce “events”• Bunches focused to less than 10 nm in vertical

Performance depends on good alignment…

…but ground motion creates micron displacements in 100 s

Want relative motion information …

Advanced Test Facility (Japan)

ATF2 extraction line: 08 Feb 2008

QD0

QD1

Advanced Test Facility (Japan)

ATF2 Final focus region

Shintake Monitor

Final Focus Quadrupole

Stabilisation monitoring

• Between neighbouring accelerator components

• Most important is the vertical component

• Resolution target nm

• Typical range up to 10 m

Monitoring grid

Straightness monitor concept

• Displacements along 8 interferometer lines

Compact Straightness Monitor (CSM)

Distance Meter Interferometers

Simulated fringe pattern – as would be seen on a camera

2 techniques deployed together in same interferometer• Frequency Scanning Interferometry (FSI) – range• Fixed Frequency Interferometry (FFI) - changes

Interferometer operation

Intensity

Interferometer phase is calculated from fibre intensity: One photodiode per fibre

System data flow overview

Length Measurement

System

GridRecon.

Control

Temperature/Pressure

“Alignment”

Alignment model

SOFTWARE

SOFTWARE

HARDWARE + SOFTWARE

Summer projects 2008

• Data read out for our hardware– FPGA programming– USB control and readout

• Understanding the interferometer grid– Multilateration– Piezo and retroreflector calibration

• Data display and analysis– Employing LiCAS Analysis Framework

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

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

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

Straightness monitor concept