The current status of Photon Calibrator in KAGRA Bin-Hua Hsieh On behalf of Calibration group ICRR, The University of Tokyo Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 1
Outline • Overview • Instruments of Photon Calibrator • Requirements • Optical Follower Servo and feedback loop • Measurement plan • Results • Summary Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 2
Why Calibration is important? • LIGO and Virgo have already detected gravitational wave, we need the calibration to extract parameters accurately from gravitational wave signal. Goal of accuracy • 1% in amplitude • 1 degree in phase Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 3
Why we need Photon Calibrator? Rx Tx Rx Laser Tx displacement 1. Characterize the displacement of mirror 2. Understand the parameter in realtime interferometer control in order to reconstruct the gravitational wave signal. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 4
Where is ETM Photon Calibrator in KAGRA? Transmitter module Tx PCal Rx Tx EYA Receiver module Rx Pcal: Photon Calibrator 36m Beam Splitter Rx EXA Laser 3km Tx ETM: End Test Mass Photodetector Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 5
Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 6
Transmitter Module 900mm OFSPD 900m m OFSPD 20W 2 innovations compared to LIGO: 1. 20 watts high power laser 2. 2 Acousic optic modulator Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 7
Receiver Module QPD RxPD Quadrant Integrating Photo Diode: sphere at Rx Monitoring the beam position Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 8
Relative Power Noise Requirements KAGRA strain sensitivity 19 − 10 ∆ L ( f ) = 2 ∆ P cos( θ ) M (2 π f ) 2 < 1 1 10 ∆ h ( f ) L 20 − 10 c ) Hz − 21 10 Sensitivity(1/ Force Force to strain sensitivity − 22 10 length curve of KAGRA transfer − 23 10 function = Mc (2 π f ) 2 ∆ h ( f ) L − 24 10 RPN = ∆ P 3 2 10 10 10 Frequency(Hz) 20 P cos( θ ) P Pcal requirement 0 − 20 M: ETM Mass (23kg) 40 − c: Speed of light ) Hz Magnitude(dB RPN/ − 60 L: Arm length of Interferometer (3km) − 80 P: Laser Power (10W) − 100 − 120 140 − 3 2 10 10 10 Frequency(Hz) Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 9
Calibration Lines 0 Preliminary OFS 1 20 OFS 2 − 40 − ) Hz 60 − Magnitude(dB/ 80 − − 100 120 − 140 − 3 2 10 10 10 Frequency(Hz) 7Hz 35Hz 330Hz 1kHz 3kHz Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 10
Harmonic Noise Requirements 35Hz 70Hz 105Hz 140Hz 35Hz modulation FFT To decide whether the peak is within requirements or not, first we need to define the noise requirement of Photon Calibrator. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 11
Power stabilization O ff set Gain Laser Injected OFS AOM Signal Mirror -1 PD OFS Optical Follower Servo AOM Acoustic Optic Modulator PD Photodetector We use Optical Follower Servo and photodetector to make a closed-loop in order to reduce the noise of laser. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 12
Optical Follower Servo OFS Back Board Ver. 1 OFS Front Board Ver. 4 Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 13
OFS & Interface Chassis OFS Chassis Back Board Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 14
Measurement Plan • Develop Photon Calibrator Lab test: KEK • Measurement: 1. Transfer function 2. Relative Power Noise Analysis is 3. Higher Harmonic Noise still ongoing 4. Peak stability • Assemble Photon Calibrator Ｗ e are here! Kamioka test: • Measurement: KAGRA site 1. Transfer function 2. Relative Power Noise 3. Higher Harmonic Noise 4. Peak stability Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 15
Lab test in KEK From/To DGS OFS & Interface module Tx module Rx module Laser beam Laser Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 16
Lab test in KEK Tx module OFS & Interface module Rx module Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 17
Takaaki Yokozawa Bin-Hua Hsieh Yu-Kuang Chu (Cory) Takahiro Yamamoto Yuki Inoue Takayuki Tomaru Sadakazu Haino Nobuyuki Kanda Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 18
Gain budget diagram Laser DAC Gain O ff set Beam AOM NDF PD OFS Sampler 2.3OD 20.70 0.004 31.808dB =0.005 26.31dB 0.87 -1.21dB injected -0.92dB 0.90 signal Beam PD AOM NDF OFS Sampler 20.39 0.004 2.3OD 31.808dB =0.005 26.18dB OFS1:56.91dB Open-loop TF OFS2:56.07dB Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 19
Transfer function Simulation vs. Observed (amplitude) Simulation vs. Observed (phase) 0 60 − 10 50 20 − 40 Phase (degree) Magnitude(dB) 30 − Closed loop simulation 30 Closed loop observed − 40 Open loop simulation 20 50 − Closed loop simulation Open loop observed 60 Closed loop observed − 10 Open loop observed 70 − 0 Open loop observed − 80 3 3 2 2 10 10 10 10 10 10 Frequency(Hz) Frequency(Hz) Observed results consist G open G closed = with simulation result. 1 + G open Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Open Loop (amplitude) Open Loop (phase) 60 0 59 10 − 58 20 57 − Phase (degree) Magnitude(dB) 56 30 − 55 40 − 54 − 50 Path1 Path1 53 60 − 52 Path2 − 70 Path2 51 50 80 − 3 3 2 2 10 10 10 10 10 10 Frequency(Hz) Frequency(Hz) Closed Loop (amplitude) Closed Loop (phase) 1 10 0.8 8 0.6 6 0.4 4 Phase (degree) Magnitude(dB) 0.2 2 0 0 0.2 − 2 − Path1 Path1 0.4 − − 4 0.6 6 − − Path2 Path2 − 0.8 − 8 10 1 − − 3 3 2 2 10 10 10 10 10 10 Frequency(Hz) Frequency(Hz) Path 1 result consists G open G closed = with Path2 result. 1 + G open Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Summary • We built a Photon Calibrator with 20W laser for the reconstruction of gravitational wave. • We used Optical Follower Servo to make a closed- loop feedback control in order to decrease the noise of laser power. • We finished the lab test in KEK, and we are going to move on to KAGRA site test. • The measurement results of transfer function consist with simulation results, and each paths also consists with each other. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 22
Future Plan • We are assembling Photon Calibrator and will characterize it in KAGRA site. • We will measure the • transfer function, • relative power noise, • higher harmonic noise • peak stability in KAGRA site, and compare the result with lab test. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 23
Supplementary Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 24
AOM transmittance AOM transmittance divided by the peak value at 0.5V input AOM Transmittance 100 90 80 Ratio to value at 0.5V (%) 70 60 50 working point 40 30 20 Path1 10 Path2 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Input voltage (V) working point: input voltage at 0.23V Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Setup Laser DAC 0.03Hz pole Gain 100 gain O ff set P Beam injected HPF AOM NDF PD OFS Sampler signal P’ P = P 0 + n ADC P 0 = P 0 0 + n 0 ≈ gn (P 0 0 ≈ 0) = n 0 RPN = n P 0 g P 0 In our measurement, P 0 comes after PD. Therefore, g = 100 Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR 26
DAC noise • I use spectrum analyzer and g=1000 (60dB) amplifier to check the noise level of DAC. The noise level of DAC is -130Vrms/rtHz. In our measurement which DC signal of PD is around 3V, this DAC noise is around -140dB/rtHz. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Noise floor by changing Offset and Gain (Open loop) • I measured closed loop noise level and open loop noise level of OFSPD1 with di ff erent gain and o ff set using spectrum analyzer. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Noise floor by changing Offset and Gain (Open loop) To AOM(V) Gain (dB) OFS1 O ff set OFS2 O ff set OFS1 RPN OFS2 RPN 0 0.12 0.12 -108.73 -108.73 0.1 15.174 0.042 0.04 -97.73 -97.73 31.808 0.0288 0.0277 -77.73 -77.73 0 0.22 0.22 -112.6 -112.96 0.2 31.808 0.0314 0.0302 -87.6 -87.95 0 0.246 0.246 -114.13 -114.43 0.225 31.808 0.032 0.0308 -89.13 -89.43 0 0.325 0.32 -115.67 -115.67 0.3 31.808 0.0342 0.033 -92.67 -92.67 0 0.43 0.424 -114.82 -115.22 0.4 31.808 0.037 0.0356 -99.82 -100.22 Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Noise floor by changing Offset and Gain (Closed loop) To AOM(V) Gain (dB) OFS1 O ff set OFS2 O ff set OFS1 RPN OFS2 RPN 0.1 31.808 0.8 0.8 -127.73 -127.73 0.2 31.808 2.5 2.6 -124.60 -124.96 0.225 31.808 3 3.1 -124.40 -124.71 0.3 31.808 4.3 4.5 -122.61 -122.87 0.4 31.808 5.5 5.8 -127.74 -125.19 Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
Discussion 1. From closed Loop measurement, change the o ff set doesn’t e ff ect the noise level too much. 2. From open loop measurement, we can see that if the gain increases, the noise also increases. If we decrease the gain in close loop measurement, then the noise level might decrease. Then we need to sacrifice the high gain in close loop feedback control. Feb. 23 rd , 2018 2018 ICRR Thesis Workshop @ ICRR
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