Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Acoustic Emission Sensor Systemof Subaru Primary Mirror

to Monitor Micro-Vibrationsdue to External Impacts

Iye,M., Takato,N., Miyashita,A., Nabeshima,Y., Oshima,N., Namikawa,K., Okita,K., Usuda,T., Sasaki,T.(SubaruTelescope),

Miyagawa,R., Shigemori,K.,(Kumamoto Industrial Research Institute)

Sonoda,M., Kubota,H.(Kumamoto Univ.)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Subaru M1 has 261 Back pockets, most “fragile”large mirror.

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Microcrack Damage Cure Treatment

49chips/cracks found during the first 4 years of which 7 were cured.

Mostly due to fallen bolts/nuts.

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

• Objectives: Record the time and location of sound generating events on M1 (e.g. fallen bolt/nut, earthquake...) for inspection on recoating to repair any microcrack damages.

• Method: Deploy 6 AE sensors (Piezo-transducers) to record micro-vibrations.

• Seismology analysis is used to identify the epicenters and the events are recorded in automatic data logger and alarm emails are issued.

• System in operation from March 16, 2007.

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Preliminary Test Configuration

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Sensor Deployment for test

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Test Procedure

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Three Modes of Sound Waves

Slow strong

vR=3.29km/sSurface Rayleigh Wave

Not detected

vT=3.62km/sTransversal Wave

Fast weakvL=5.74km/sLongitudinal Wave

SignalSpeedMode

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Measured Sound Signals

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Travelling echoes

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Signal attenuation

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Sound Propagation

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

System

Sensors: Fuji Ceramics, 6x M204A, 180kHz

Preamp Unit: Fuji Ceramics A1002

Data Recorder:YOKOGAWA DL750 ScopeCorder

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

First Sounds

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)

Earthquake WS, March 23, 2007, Keauhou, M.Iye(Subaru Telescope)