phase camera development for gravitational wave detectors

Phase camera development for gravitational wave detectors

Kazuhiro Agatsuma

Martin van Beuzekom, David Rabeling, Guido Visser, Hans Verkooijen, Wilco Vink, Jo van den Brand

4th/June/2014TIPP at Amsterdam

2014/June/4 TIPP@Amsterdam 1

ContentsPhase camera is prepared for Advanced VIRGO

• Background– Gravitational waves– GW detector– VIRGO– Marginally stable power recycling cavity

• Phase camera– Principle– Setup plan in AdV

• Prototype experiment at Nikhef• Selection of components• Summary and plan

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Gravitational waves

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x

yz

Gravitational waves

Predicted by A. Einstein (1916)Nobody detect it directly yet

Indirect evidence¨ Hulse and Taylor pulsar (1974)

=> Nobel prize (1993)¨ BICEP2 (2014 in discussion)

Direct observations will make a new method to observe universe¨ Binary neutron star¨ Black hole¨ Super nova¨ Inflation¨ Unknown source¨ etc…

¨ General relativity¨ Beginning of universe

Gravitational wave detector

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Laser

Input ModeCleaner

Output Mode Cleaner

Photo detector

y

x

Michelson InterferometerFabry-Perot Michelson InterferometerPower recycled Fabry-Perot Michelson InterferometerDual recycled Fabry-Perot Michelson Interferometer

Fabry-PerotCavity

BS

Signal recycling mirror

Power recycling mirror

Modulation-Demodulation(Pound–Drever–Hall technique)is used to operate IFO(control position and angle)

EOM

fp

VIRGO

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Nikhef contributes to VIRGO(Collaboration between France, Italy, Netherlands, Poland and Hungary)

UpgradeVIRGO => advanced VIRGO (AdV)

Worldwide competition to the first detection¨ LIGO (USA)¨ KAGRA (Japan)

After the first detectionWorld competition => World corroboration

(Italy, Pisa)[http://www.ego-gw.it/public/about/welcome.aspx]

Marginally stable recycling cavity

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VIRGO uses marginally stable recycling cavityÞ Degeneration of higher

order modes (HOMs)(Sideband power reduction can easily happen by aberration of mirrors)Þ Control becomes unstable

Aberrations¨ Thermal lens¨ Substrate inhomogeneities¨ Surface shape errors

Solution: Thermal Compensation System (TCS) Sensor: Phase camera, Actuator: CO2 laser with compensation plate

ITMBSPRM

ITM

Pick-off

Wave front sensor

CO2 laser

Phase CameraFrequency selective wave front sensor¨Heterodyne detection¨Pin-hole scanning

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Test beam(with PM: fp)

Reference beam(Frequency shift by fH)

Pin-hole

Scanner

BSDemodulationfH, fH+fp, fH-fp

IQ

Mapping of amplitude and phase

EOM

IFO(Pick-off mirror in IFO)PM for IFO

fH

fpAOM

Setup plan in AdV

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: Arm cavity control (common)

: SRC

: PRC

: Support for f1

: Input MC

EOM

IMC

OMC

PC1PC2

PC3

CO2 laser

Phase camera will be placed on three portsPC1: Input beam [f1 - f5]PC2: Power recycling cavity [f1, f4]PC3: Output beam [f2]

Five sidebands will be used

Setup plan in AdV

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Frequency shifter: Fiber coupled AOMPC1: Input beam (Injection bench)PC2: Power recycling cavity (B4)PC3: Output beam (B1p)

Prototype test at Nikhef

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- Current setup -• Test beam:

Phase modulator (EOM): DC -> 250 MHz

• Reference beam: Frequency shift (AOM): 80 MHz

• Scanner: Galvanometer (GVS012)• Photo-detector : New focus 1811 (125 MHz)• DSP:

– LAPP fast ADC/FPGA board (400MHz Clock)– AdV Real-time system signal processing

Each sideband is selective

Prototype test at Nikhef

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AOM

EOM

Laser

Galvanometer

PD

Mapping result (preliminary)• Test beam: 10MHz PM• Power ratio (test beam and

reference beam) is not optimized here

=> Calculation of SNR using actual parameters is in progress

• The phase between carrier and sidebands should be identical in the ideal IFO

=> Subtraction of those shows aberration map!

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Carrier

USB

Test Reference

Scanning pattern (Archimedes' spiral)

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32 x 32 pixels: 16 Hz 128 x 128 pixels: 64 Hz 256 x 256 pixels: 128 Hz

In the case of the total acquisition time of 1 second to make one pattern(According to a simulation, a total acquisition time of at least 2-5 s [0.03 s] is necessary in order to keep sufficient precision of the phase measurement)Standard aperture diameter: 5 mmTest beam size: w = (2.5) / 3 = 833 um

Quickest acquisition is 0.25 s (128 x 128 pixels, 256 Hz) with our scanner(Requirement: 100 x 100 pixels)

Scanner (PZT scanner)

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Tilt angle range: 50 mrad (±25 mrad)

Þ to scan 5 mm range,a half a maximum voltage is necessary with 20 cm distanceÞ The quickest operation is 300 Hz

~300 Hz

20 cm

PD5 mm

Photodiode board

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• DC output and • RF TIA: HITTITE 799LP3E• 10 kOhm• DC – 700MHz• 46 nV/rtHz output noise (spec)• = 4.6 pA/rtHz input referrred• Shot noise limited if Idiode > ~66 uA

• FCI-InGaAs-55• Active area diameter = 55 mm (pin-hole)• NEP 2.66e-15 W/rtHz• Flat window, AR coated

(VIR-0439A-13)

New PD has been developed at Nikhef (close to completion)Flat response up to 700MHz

Digital demodulation board

• Digital Demodulation at 11 (fixed) frequencies (fh+/f1..f5) in parallel• 14 bit ADC at 500 MS/s + Xilinx Virtex-7 FPGA• Measure phase (and power) using 16k samples per ‘pixel’

– can measure 32 k ‘pixels’ per second, frequency resolution ~30 kHz• Best resolution when using external ref. frequencies (i.e. diff. phase measurement)

– s = ~0.3 mRad at 211 MHz

ADC

ADCfh

fh +/- f1..f5

Hann*cosine

LUT 16k

Hann*sine

LUT 16k

PD in atan

I

Q

atan

Q

I

Df

11x ‘DFT-slice’

cntr0..N-1

sampleclock

power

to DAQblock

fh +/- f1..f5f1..f5

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(VIR-0439A-13)

Optical layout design (PC1)

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z=0 ( ) preliminary design※

Optical layout is in progress

Summary and PlanSummary• Phase camera can observe wave fronts for each PM sideband

=> Useful monitor for TCS in Virgo• Prototype experiment is on going

– Component selection has done– High speed PD and digital board are being prepared at Nikhef

Plan (in progress)• SNR calculation using actual parameters• Optical layout drawings

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