LIGO-G000309-00-D “ First Lock” for the LIGO Detectors 20 October 2000 LIGO Hanford Observatory Stan Whitcomb
LIGO-G000309-00-D
“First Lock” for the LIGO Detectors
20 October 2000 LIGO Hanford Observatory
Stan Whitcomb
LIGO "First Lock" 2LIGO-G000309-00-D
Outline
The LIGO Detectors
What is “Locking an Interferometer”?» Why do we need to do it?
» ….and why is it so difficult?
Evidence for Locking
The Next Steps
LIGO "First Lock" 3LIGO-G000309-00-D
LIGO Interferometer (Detector)
Laser
end test mass
2 km (4 km) Fabry-Perotarm cavity
recyclingmirror input test mass
beam splitter
Power RecycledMichelsonInterferometerwith Fabry-PerotArm Cavities
Power RecycledMichelsonInterferometerwith Fabry-PerotArm Cavities
signal
LIGO "First Lock" 4LIGO-G000309-00-D
Suspending the Test Masses (Mirrors)
vibration-isolated platform
initial alignment
test mass suspended on fine wire
LIGO "First Lock" 5LIGO-G000309-00-D
Sensing the Effect of a Gravitational Wave
Laser
signal
Gravitational wave changes arm lengths and amount of light in signal
Change in arm length is 10-18 meters,
or about 2/10000000000000000 inches
LIGO "First Lock" 6LIGO-G000309-00-D
How Small is 10-18 Meter
One meter, about 40 inches
Human hair, about 100 microns000,10
Wavelength of light, about 1 micron100
LIGO sensitivity, 10-18 meter000,1
Nuclear diameter, 10-15 meter000,100
Atomic diameter, 10-10 meter000,10
LIGO "First Lock" 7LIGO-G000309-00-D
LIGO Interferometers
Laser
end test mass
Light bounces back and forth along arms about 100 times
input test massLight is “recycled” about 50 times
signal
Requires test masses to be held in position to 10-10 meter (atomic diameter)“Locking the interferometer”
LIGO "First Lock" 8LIGO-G000309-00-D
Why is Locking Difficult?
One meter, about 40 inches
Human hair, about 100 microns000,10
Wavelength of light, about 1 micron100
LIGO sensitivity, 10-18 meter000,1
Nuclear diameter, 10-15 meter000,100
Atomic diameter, 10-10 meter000,10
Earthtides, about 100 microns
Microseismic motion, about 1 micron
Precision required to lock, about 10-10 meter
LIGO "First Lock" 9LIGO-G000309-00-D
Steps to Locking an Interferometer
signal
LaserX Arm
Y Arm
Composite Video
LIGO "First Lock" 10LIGO-G000309-00-D
Watching the Interferometer Lock
signal
X Arm
Y Arm
Laser
LIGO "First Lock" 11LIGO-G000309-00-D
Lock Duration
2 Minutes
Locked
Unlocked
LIGO "First Lock" 12LIGO-G000309-00-D
Where Do We Go From Here?
Extend the time that the interferometer locks» Goal is 40 hours, not seconds or minutes
LIGO "First Lock" 13LIGO-G000309-00-D
Extending the Lock on a Single Arm
Change to X Arm» 2/12/00 18 minutes lock
» 3/4/00 90 minutes lock
» 3/26/00 10 hours lock
Start with Y Arm» 12/1/99 Flashes of light
» 12/9/99 0.2 seconds lock
» 1/14/00 2 seconds lock
» 1/19/00 60 seconds lock
» 1/21/00 5 minutes lock
Laser
Result of : -automatic alignment system -tuning electronics -reduction of noise sources
2 km Arm
LIGO "First Lock" 14LIGO-G000309-00-D
Extend the time that the interferometer locks» Goal is 40 hours, not seconds or minutes
Increase the sensitivity (reduce the noise)» Tune each subsystem for optimal performance
Where Do We Go From Here?
LIGO "First Lock" 15LIGO-G000309-00-D
Improvements in Laser Performance
Laser stability an important contributor to LIGO sensitivity
Steady improvement in laser noise performance
» electronics» acoustics» vibrations
Required
LIGO "First Lock" 16LIGO-G000309-00-D
Where Do We Go From Here?
Extend the time that the interferometer locks» Goal is 40 hours, not seconds or minutes
Increase the sensitivity (reduce the noise)» Tune each subsystem for optimal performance
Bring two more detectors on-line» Second detector here at Hanford Observatory
» Single detector at Livingston Observatory
LIGO "First Lock" 17LIGO-G000309-00-D
Summary
“Locking the Interferometer” marks a major transition for LIGO» Commissioning a full interferometer,
not individual subsystems
“First Lock” in the HanfordObservatorycontrol room
Akin to Wright brothers’ first flight
»It doesn’t stay up that long
»It isn’t very far off the ground
»But it does fly!