MONALISA an Update David Urner Paul Coe Matthew Warden Armin Reichold Monitoring, Alignment & Stabilisation with high Accuracy

Nanobeam'08D. Urner2 MONALISA Is an interferometric metrology system for continuous monitoring of position critical accelerator components Consists of a fixed network of evacuated interferometric distance meters

Nanobeam'08D. Urner3 Concepts

Nanobeam'08D. Urner4 QD0 Shintake Monitor Table Compact Straightness Monitor Very Schematic View of ATF2 Setup 10cm

Nanobeam'08D. Urner5 Compact Straightness Monitor 6D position transferred from left to right –breaking of symmetries is important Preliminary simulation results of CSM Resolution: –  y :10nm – distance meter resolution: 1nm = Resolution in z-direction – Positional change of optics components with respect to each other: 1nm. That’s the challenge! 10cm

Nanobeam'08D. Urner6 Measurement lines We measure distances along measurement lines using two techniques: Absolute distance interferometry <  m resolutions Displacement interferometry nm resolutions Each line is the same, and is capable of performing both types of measurement. Absolute distance Displacement

Nanobeam'08D. Urner7 Interferometer operation Intensity

Nanobeam'08D. Urner8 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 frequeny scanning

Nanobeam'08D. Urner9 Distance meter Measurement Frequencies: –FFI:up to 10kHz –FSI:up to 1Hz Long term stability determines low frequency behaviour –Minutes possible –Lot of work needed to extend to hours or days. Advantage of interferometric measurement system is fairly low cost per line. –Use of telecom frequency allows use of cheap commercial hardware –Cheap amplification of light –Current estimate: as low as £800 per distance metre

Nanobeam'08D. Urner10 Current Status

Nanobeam'08D. Urner11 Vacuum System 8 way fibre ribbon Tapered hole Vacuum vessel wall

Nanobeam'08D. Urner12 First Measurements in Vacuum Unexpected mechanical behaviour Tensioning of a drum –more mechanical vibrations in vacuum –Hard to separate these from resolution effects Need for vibration isolation and possibly damping Change in Length Measured Frequency Pressure1 Atmvac Vacuum features air Atm Vac

Nanobeam'08D. Urner13 Atm vac Changing Pressure Good agreement between FSI and FFI Decent correlation between pressure and measured OPD Displacement (microns) Calculated overall change: 69  m

Nanobeam'08D. Urner14 FSI Dominated by actual vibrations! –Need damping –Need better launch head

Nanobeam'08D. Urner15 Compact Launch Head Launch Head needs following features: –Compact –Stable/rugged Temperature Vibrations –Cheap Prototype: –Adjustable –Currently being built Future: Jig to position –Glue components onto substrate Titanium

Nanobeam'08D. Urner16 Fixed Frequency Interferometry Improvement of amplifier to reduce temperature dependence Test of Amplifier for White Noise behavior: –Linear with laser power –With high laser power translates to 1pm/√Hz Spectrum above 1kHz seems to be white noise dominated Spectrum below 1kHz clearly vibration dominated –Vibration Isolation –Stable launch head Eventually see effects from –Air turbulences –Laser frequency instabilities Frequency [kHz]

Nanobeam'08D. Urner17 Frequency Stabilisation Lock laser to spectral feature of rubidium Use a frequency doubling crystal to reach this frequency

Nanobeam'08D. Urner18 Frequency Stabilisation All parts are at Oxford Mechanical assembly in progress

Nanobeam'08D. Urner19 Old design Vacuum System at KEK

Nanobeam'08D. Urner20 Double bellow system: - Advantage: - smaller frame - Disadvantage: - active feedback - slightly less good compensation of forces New Design Vacuum System at ATF2

Nanobeam'08D. Urner21 Double bellow system: Optics Vacuum Compensation Chamber 2 Atmosphere pressure Active feedback: - measure pressure in inner and outer bellow chamber - stabilize sum of pressures + Valve to air Valve to pressured air <<>>

Nanobeam'08D. Urner22 Summary Very first measurements in vacuum Compact Launch Head Frequency Stabilization Vacuum System for ATF2

Nanobeam'08D. Urner23