Global control using a laser strainmeter for KAGRA Kouseki Miyo - PowerPoint PPT Presentation

Global control using a laser strainmeter for KAGRA Kouseki Miyo Sep 9, 2019, TAUP2019 at Toyama

Contents 3000 m 500 m 1500 m 1000 m X arm Y arm Laser Strainmeter 1. Introduction 2. Strainmeter of KAGRA 3. Sensor Correction Technique 4. First trial 5. Results 2

Seismic noise under ground Earth Tides 
 ~100 um 
 ~10 -5 Hz) Microseismic Wind, trafic, human activity In lower frequencies, reduction is not so much. K. Yamamoto, JGW-T1000218, (2010) 3

potentially limits the duty cycle of KAGRA. TestMass The range is enough, but small actuator range Actuator range and seismic noise (MN) MarionetteMass Mass (IM) Intermediate 
 (TM) * * * 50th 90th 99th MN IM TM klog:9386 * Y. Michimura, et. al., (2017) 4

• Strainmeter can FeedForward the seismic motion to the arm to reduce the feedback force. 2nd floor 1st floor 3 km 1.5 km IX EX Strainmeter X arm Global Control Feedback Global Control on the Arm cavity 5

In the case of LIGO 4 km EX Arm Local Control • Seismometers can also measure the arm fluctuation . 6

N LVDT N STRAIN (Trillium120Q) N SEIS • However, seismometers can not measure the ground motion below 80 mHz. • The strainmeter can measure below that. Seismometers and Strainmeter 7

Earth Tides (KAGRA strainmeter) Microseismic • Strainmeter can measure almost all seismic motion in low frequency. Bandwidth of the Strainmeters A. Araya et. al., (2017) 8

Strainmeter of KAGRA PBS • Wide dynamic range length changes • Rotation indicates arm detection • Quadrature phase 1500 m ΔL Laser Stabilized Frequency circular - polarized sin s - polarized p - polarized sin cos QWP HWP End Reflector Front Reflector -ΔL ＋ΔL cos 9

The strainmeter KAGRA X arm Stand Alone DAQ End Reflector KAGRA X arm Frequency Stabilized Laser Front Chamber Center 
 Area X End Me 10

Sensor Correction Technique + - - Strainmeter X TM(EX) Position sensor X STG X GND where, X GND(IX) - + X TM X STG - H TM (r=0) X GND(EX) Hs S ff C fb C sc C ff Pa S fb N ff N fb r - - - + Test Mass Actuator IP 11

Sensor Correction Technique EX follow IX by using SC. X TM + - X GND(IX) where, If G is high and SC will subtract, 
 X GND - X STG Position sensor X TM(EX) Strainmeter - - X STG + H TM S fb Hs S ff C fb C sc C ff Pa X GND(EX) N ff N fb r - - - + (r=0) Test Mass Actuator IP 12

Sensor Correction Technique X GND X TM + - X GND(IX) If G is high and SC will subtract, 
 EX follow IX by using SC. X STG + Position sensor X TM(EX) Strainmeter - - Test Mass 1 X STG - H TM X GND(EX) Hs S ff C fb C sc C ff Pa S fb 1 N ff N fb r - - - + (r=0) Actuator IP 13

Sensor Correction Technique EX follow IX by using SC. X STG X TM + - X GND(IX) If G is high and SC will subtract, 
 X GND H TM X STG Position sensor X TM(EX) Strainmeter - - - + (r=0) X GND(EX) Hs S ff C fb C sc C ff Pa S fb N ff N fb r - - - + Test Mass Actuator IP 14

Sensor Correction Technique EX follow IX by using SC. X STG X TM + - X GND(IX) If G is high and SC will subtract, 
 X GND H TM X STG Position sensor X TM(EX) Strainmeter - - - + (r=0) X GND(EX) Hs S ff C fb C sc C ff Pa S fb N ff N fb r - - - + Test Mass Actuator IP 15

Sensor Correction Technique X GND X STG X TM + - X GND(IX) If G is high and SC will subtract, 
 X STG H TM Position sensor X TM(EX) Strainmeter - - Test Mass - + (r=0) S fb Hs S ff C fb C sc C ff Pa We can make the EX follow the IX motion! X GND(EX) N ff N fb r - - - + Actuator IP 16

First trial • Correction signal was feedforwarded to the EX suspension point. The singnal was injected in all frequencies. • No arm length control to the test mass. The FP was locked by the feedback loop to the AOM. Laser Feedback Signal Not use Correction Signal 17

OFF ON • Slow motion was subtracted from FeedBack signal Result • High frequency motions are not seemed so. Worked! e d i T h t r a E 18

Higher frequency band • Noise was injected 
 (~ 0.8 Hz) 
 →Need lowpass filter • No big difference in RMS, because of a peak at 150 mHz. RMS (ON) RMS (OFF) We need more investigation 19

Summary • Actuator range is limited near the test mass not to introduce electric noises on the GW signal. • Unlike seismometers, the laser strainmeter has an advantage to measure the change of arm length directly. It also covers frequency range where seismometers cannot measure the ground motion accurately. • Sensor correction technique using strainmeter can make the EX test mass follow the IX test mass motion. • We need more investigation to improve the subtraction 20

Backup 21

Frequency Stabilized Laser AM Nd:YAG s - polarized p - polarized Prob Pump Derivative Signal Absorption Signal 6 kHz 97 kHz FM - + Stabilized Light QWP AOM Iodine cell FI PBS1 PBS2 BS1 BS2 PZT TMP 22