Phase camera development for gravitational wave detectors Kazuhiro

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 2014/June/4 TIPP@Amsterdam 1

Contents Phase camera is prepared for Advanced VIRGO • Background – – Gravitational waves GW detector VIRGO Marginally stable power recycling cavity • Phase camera – Principle – Setup plan in Ad. V • Prototype experiment at Nikhef • Selection of components • Summary and plan 2014/June/4 TIPP@Amsterdam 2

Gravitational waves Predicted by A. Einstein (1916) Nobody detect it directly yet Gravitational waves Indirect evidence ¨Hulse and Taylor pulsar (1974) => Nobel prize (1993) ¨BICEP 2 (2014 in discussion) Direct observations will make a new method to observe universe ¨Binary neutron star ¨Black hole ¨Super nova ¨Inflation ¨Unknown source ¨etc… z y x ¨General relativity ¨Beginning of universe 2014/June/4 TIPP@Amsterdam 3

Gravitational wave detector Michelson Interferometer Fabry-Perot Michelson Interferometer Power recycled Fabry-Perot Michelson Interferometer Dual recycled Fabry-Perot Michelson Interferometer Laser x Power recycling BS mirror EOM fp Signal recycling mirror Input Mode Cleaner Modulation-Demodulation (Pound–Drever–Hall technique) is used to operate IFO (control position and angle) 2014/June/4 y Fabry-Perot Cavity Output Mode Cleaner Photo detector TIPP@Amsterdam 4

VIRGO Nikhef contributes to VIRGO (Collaboration between France, Italy, Netherlands, Poland Hungary) Upgrade VIRGO => advanced VIRGO (Ad. V) (Italy, Pisa) [http: //www. ego-gw. it/public/about/welcome. aspx] Worldwide competition to the first detection ¨LIGO (USA) ¨KAGRA (Japan) After the first detection World competition => World corroboration 2014/June/4 TIPP@Amsterdam 5

Marginally stable recycling cavity VIRGO uses marginally stable recycling cavity Þ Degeneration of higher order modes (HOMs) ITM (Sideband power reduction can easily happen by aberration of mirrors) Aberrations ¨Thermal lens ¨Substrate inhomogeneities ¨Surface shape errors Þ Control becomes unstable PRM Wave front sensor CO 2 laser BS ITM Pick-off Solution: Thermal Compensation System (TCS) Sensor: Phase camera, Actuator: CO 2 laser with compensation plate 2014/June/4 TIPP@Amsterdam 6

Phase Camera Frequency selective wave front sensor ¨Heterodyne detection ¨Pin-hole scanning IFO (Pick-off mirror in IFO) PM for IFO EOM fp AOM f. H BS Reference beam (Frequency shift by f. H) Scanner Test beam (with PM: fp) Demodulation f. H, f. H+fp, f. H-fp I Q Pin-hole Mapping of amplitude and phase 2014/June/4 TIPP@Amsterdam 7

Setup plan in Ad. V Phase camera will be placed on three ports PC 1: Input beam [f 1 - f 5] PC 2: Power recycling cavity [f 1, f 4] PC 3: Output beam [f 2] PC 1 PC 2 CO 2 laser EOM IMC : Arm cavity control (common) PC 3 : SRC : PRC OMC : Support for f 1 : Input MC Five sidebands will be used 2014/June/4 TIPP@Amsterdam 8

Setup plan in Ad. V Frequency shifter: Fiber coupled AOM PC 1: Input beam (Injection bench) PC 2: Power recycling cavity (B 4) PC 3: Output beam (B 1 p) 2014/June/4 TIPP@Amsterdam 9

Prototype test at Nikhef - Current setup • • • Test beam: Phase modulator (EOM): DC -> 250 MHz Reference beam: Frequency shift (AOM): 80 MHz Scanner: Galvanometer (GVS 012) Photo-detector : New focus 1811 (125 MHz) DSP: – LAPP fast ADC/FPGA board (400 MHz Clock) – Ad. V Real-time system signal processing 2014/June/4 TIPP@Amsterdam Each sideband is selective 10

Prototype test at Nikhef Laser EOM AOM Galvanometer PD 2014/June/4 TIPP@Amsterdam 11

Mapping result (preliminary) Carrier • Test beam: 10 MHz PM • Power ratio (test beam and reference beam) is not optimized here Test Reference => Calculation of SNR using actual parameters is in progress USB • The phase between carrier and sidebands should be identical in the ideal IFO => Subtraction of those shows aberration map! 2014/June/4 TIPP@Amsterdam 12

Scanning pattern (Archimedes' spiral) 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 mm Test 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) 2014/June/4 TIPP@Amsterdam 13

Scanner (PZT scanner) ~300 Hz 5 mm PD 20 cm Tilt angle range: 50 mrad (± 25 mrad) Þ to scan 5 mm range, a half a maximum voltage is necessary with 20 cm distance ÞThe quickest operation is 300 Hz 2014/June/4 TIPP@Amsterdam 14

Photodiode board New PD has been developed at Nikhef (close to completion) Flat response up to 700 MHz • • FCI-In. Ga. As-55 Active area diameter = 55 mm (pin-hole) NEP 2. 66 e-15 W/rt. Hz Flat window, AR coated (VIR-0439 A-13) 2014/June/4 • • DC output and RF TIA: HITTITE 799 LP 3 E 10 k. Ohm DC – 700 MHz 46 n. V/rt. Hz output noise (spec) = 4. 6 p. A/rt. Hz input referrred Shot noise limited if Idiode > ~66 u. A TIPP@Amsterdam 15

Digital demodulation board 11 x ‘DFT-slice’ I PD in ADC atan fh +/- f 1. . f 5 power to DAQ block Q sample clock Hann* cosine LUT 16 k cntr 0. . N-1 Hann* sine LUT 16 k Df I fh f 1. . f 5 ADC atan fh +/- f 1. . f 5 Q • • • Digital Demodulation at 11 (fixed) frequencies (fh+/f 1. . f 5) in parallel 14 bit ADC at 500 MS/s + Xilinx Virtex-7 FPGA Measure phase (and power) using 16 k samples per ‘pixel’ – can measure 32 k ‘pixels’ per second, frequency resolution ~30 k. Hz • Best resolution when using external ref. frequencies (i. e. diff. phase measurement) – (VIR-0439 A-13) s = ~0. 3 m. Rad at 211 MHz 2014/June/4 TIPP@Amsterdam 16

Optical layout design (PC 1) z=0 (※) preliminary design Optical layout is in progress 2014/June/4 TIPP@Amsterdam 17

Summary and Plan Summary • 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 2014/June/4 TIPP@Amsterdam 18