acoustic emission sensor system of subaru primary mirror
TRANSCRIPT
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)