phase camera development for gravitational wave detectors
DESCRIPTION
Phase camera development for gravitational wave detectors. Kazuhiro Agatsuma Martin van Beuzekom , David Rabeling , Guido Visser , Hans Verkooijen , Wilco Vink , Jo van den Brand 4 th /June/2014 TIPP at Amsterdam. Contents. Phase camera is prepared for Advanced VIRGO Background - PowerPoint PPT PresentationTRANSCRIPT
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
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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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