Transcript G080583-00 - DCC

Enhanced LIGO
Kate Dooley
University of Florida
On behalf of the LIGO Scientific Collaboration
SESAPS Nov. 1, 2008
LIGO-G080583-00-D
Gravitational Wave Sources
THE CRAB PULSAR
• spinning neutron star
• remnant from supernova in year 1054
• gw frequency ngw = 59.8 Hz
• spin down due to:
• electromagnetic braking
Pulsars
• GW emission?
BURSTS (GRBs, supernovae)
STOCHASTIC BACKGROUND (from the Big Bang)
COALESCING BINARIES (NS/NS, NS/BH, BH/BH)
LIGO-G080583-00-D
2
2G d 2 I
h 4 2
r c dt
Ripples in Space-time
Physically, h is a strain: dL/L
LIGO measures h < 10-22
dL = 10-18 m !
Gravitational waves
A Michelson type interferometer is the ideal tool to measure GWs.
mirror
laser
detector
LIGO-G080583-00-D
LIGO Scientific Collaboration
3
Hanford (H1 = 4 km, H2 = 2 km)
LIGO Interferometers
Livingston (L1 = 4 km)
Livingston (L1 = 4 km)
LIGO-G080583-00-D
LIGO Scientific Collaboration
4
Gravitational Wave Detectors

Frequency stabilized laser

Suspended masses
eLIGO powers
» Isolated from ground motion

~ 60000 W
30 W
Fabry-Perot cavities
» Effectively lengthens arms

Laser
Recycled reflected light
» Enhances phase sensitivity
1500 W
Courtesy D. Reitze
Photodiode
LIGO-G080583-00-D
LIGO Scientific Collaboration
5
LIGO Sensitivity
Motivation for eLIGO:
2x increase in sensitivity
 ~ 8x inc. in detection rate
Changes:




4x more laser power
New GW readout scheme
Upgraded Input Optics
Prototype of advanced
seismic isolation
 Upgraded Thermal
Compensation System
h(f) [Hz -1/2]
Initial LIGO
Enhanced LIGO
Advanced LIGO
Frequency [Hz]
LIGO-G080583-00-D
LIGO Scientific Collaboration
6
35 Watt Laser
LZH (Germany) built us a custom 35W laser
• 2W NPRO amplified by a 4 rod Nd:YVO4
• lambda = 1064 nm
• frequency stabilized by reference cavity
Laser produces beautiful
TEM00 Mode
LIGO-G080583-00-D
LIGO Scientific Collaboration
7
Gravitational Wave Readout
Hardware:
• Output Mode Cleaner
• advanced seismic
isolation
Improves:
• shot noise
• laser intensity noise
LIGO-G080583-00-D
LIGO Scientific Collaboration
8
Input
Mode CleanerModulator
Electro-optic
– 3 mirror–
crystalfilters
cavity
oscillator
out higher
phase
modulates
modes
carrier
delivered
light to
Opticsorder
createlaser
from
reference sidebands
The Input Optics include all the elements from the
EOM to the Mode-Matching Telescope.
Reference
cavity
air
Recycling mirror
vacuum
Faraday
isolator
EOM
Faraday Isolator – optical
Laser
diode
protects laser from
reflected light
Pre-Mode
Cleaner
Mode matching
telescope
Mode
Cleaner
Mode Matching Telescope – 3
spherical mirrors deliver
correct beam size and shape to
LIGO Scientific Collaboration
interferometer
LIGO-G080583-00-D
9
Faraday Isolator
Faraday rotator
QR
1.6 mW
1.0 W
919 mW
CWP
TFP
DKDP
For higher power need:
Isolation
ratio: 14 dB  28 dB
minimal thermal lensing
Transmission:
89%  92%
minimal thermal drift
Thermal
Drift: 100 urad/W
high transmission
 10 urad/W
high isolation ratio
LIGO-G080583-00-D
TGG
TGG
HWP
CWP
New Design:
low absorption crystals
compensating negative lens
increased thermal contact
high extinction ratio polarizers
LIGO Scientific Collaboration
10
Status Today
LIGO-G080583-00-D
LIGO Scientific Collaboration
11
Summary


Enhanced LIGO hardware upgrade nearly complete
Challenges we still face:
» Angular instabilities from higher radiation pressure
» Alignment control of Output Mode Cleaner
» Blasting for oil in Louisiana requires night-time work



Much noise hunting to do!
Expect the detection rate for BH/BH to increase from
1/100 years to 1/9 years (uncertain by 2 orders of magnitude in either direction)
Enhanced LIGO science run to begin Spring 2009
LIGO-G080583-00-D
LIGO Scientific Collaboration
12
LIGO Scientific Collaboration
LIGO-G080490-00-I
Gravitational Waves
Electromagnetic waves
Source:
moving charge
Speed:
c
Wavelength:
c/f
r r
0
rÝ
Solution:
Ý
E r,t  ~
rˆ  rˆ  p
4 r
  
Polarizations:
Particle:
Spin:

LIGO-G080583-00-D
Gravitational waves
moving mass
c
c/f
hn  , t  
s+, sphoton
1
LIGO Scientific Collaboration
2G 
I ( , t )
4 n
rc
h+, hx
graviton
2
14
RF vs. DC Readout
RF Readout
(heterodyne detection)
-RF
• Operate at dark fringe
• GWs beat against sidebands
-GW
+GW
+RF
DC Readout
(homodyne detection)
LIGO-G080583-00-D
-GW
carrier
Optical frequency
• Operate off dark fringe
• Sidebands removed by Output
Mode Cleaner
• GWs beat against carrier
+GW
LIGO Scientific Collaboration
15
Noise Budget
LIGO-G080583-00-D
LIGO Scientific Collaboration
16