LIGO Commissioning Update LIGO Collaboration Meeting Mar 18
LIGO Commissioning Update LIGO Collaboration Meeting, Mar 18, 2003 Peter Fritschel, Daniel Sigg, Nergis Mavalvala G 030068 -00 -D LIGO I
Commissioning History 10 -17 L 4 k strain noise @ 150 Hz [Hz-1/2] 1999 4 Q Inauguration 2 Q 3 Q E 1 10 -19 10 -20 2001 2000 1 Q 10 -18 1 Q 4 Q 2 Q E 3 E 4 E 2 3 Q E 5 10 -21 2002 4 Q E 6 E 7 1 Q 2 Q 2003 3 Q E 8 4 Q 1 Q E 9 One Arm S 1 S 2 Science Run Power Recycled Michelson Recombined Interferometer Full Interferometer Washington 2 K Louisiana 4 k Washington 4 K G 030068 -00 -D First Lock Washington earthquake LIGO I LHO 2 k wire accident Now 2
S 1 Noise Component Analysis, LLO 4 k G 030068 -00 -D G 020482 -00 -D LIGO I 3 5 Rana Adhikari noise analysis
"Estimated Noise Limits for S 2" (as foretold in October 2002) G 030068 -00 -D LIGO I 4
Changes Since S 1 (highlights) q Optical lever improvements Ø Structural stiffening (designed for thermal/kinematic stability, not low vibration) Ø Improved filtering to take advantage of reduced resonances Ø Pre-ADC "whitening" for improved dynamic reserve q Improved DAC "De-Whitening" Ø Match DAC dynamic range to spectrum of correction forces at each frequency Ø Tricky handoff; reciprocal analog & digital filters must switch roles after lock acquisition, without transients q New coil drivers & realtime control code for suspensions Ø Lower noise, switchable dynamic range (200 m. A acquisition, 5 m. A running) Ø Separate DC biases for alignment Ø Better filtering, diagonalization and control/sequencing features q MORE POWER Ø Ø Enabled by better alignment stability Also required control of "I-phase" photocurrent (overload) Now ~ 1. 5 W into mode cleaners, ~ 40 W at beamsplitter (R~40) Only 10 -20 m. A average DC photocurrent at dark ports !! (optics very good) G 030068 -00 -D LIGO I 5
Stability improvements q Wavefront sensing alignment control progress Ø H 1: 8 of 10 (14) alignment degrees-of-freedom now under feedback control v Greatly improves long term power stability v Still need: all DOF; more feedback bandwidth to reduce short term power fluctuations Ø L 1: Still 2 DOF under feedback control v Bandwidth of this loop increased 10 x since S 1, reducing short term fluctuations v Phase camera implemented: makes a 2 -D map of the RF amplitude and phase ü Proven useful as a manual alignment aid G 030068 -00 -D LIGO I 6
Optical characterization q Good news: optics quality is (almost all) good Ø Recycling gain meets or exceeds goals v L 1: Gain of nearly 50 seen, more usually about 45 v H 1: Gain of 40 -45 Ø Contrast defect meets or exceeds goals v L 1: Pas/ Pbs = 3 x 10 -5 v H 1: Pas/ Pbs = 6 x 10 -4 q Bad news: Very low RF sideband gain/efficiency Ø Ø q H 1: Sideband power efficiency to AS port: ~6% L 1: similarly low Cause: thermal lensing in the ITMs isn’t at the design level Achieving shot noise goal requires that this be fixed H 2: Cause of low recycling gain (20) discovered Ø Bad (no) AR coating on ITMX, must be replaced G 030068 -00 -D LIGO I 7
S 1 6 Jan G 030068 -00 -D LIGO I 8
Tasks at Hand q q q q Seismic retrofit at LLO Finish auto-alignment system RFI cleanup, linear power supplies Thermal lensing Optical gain increase of LSC photodiodes Shot noise sensitivity Acoustic coupling Others: microseismic peak reduction (LHO), ISS, photon calibrator, ASI servo, WFS 5, replace lossy PMCs, clean MC mirrors, digital IO WFS, tune up PSLs, remote power dial, 2 K ITMX replacement, read/ process more LSC channels, finish n stabilization servos, duty cycle G 030068 -00 -D LIGO I 9
Commissioning: SEI Upgrade q The Seismic Isolation System (SEI) at LLO needs to be upgraded Ø To mitigate the higher seismic noise environment (logging principally) Ø Plan is to add an active, external pre-isolation (EPI) stage without disturbing the alignment of the installed optics q Current Plan: Ø Continue prototype testing at LASTI, including migrating from d. Space to VME based controls Ø Order components, fabricate and assemble after successful review (planned for ~4/18); fabrication/assembly phase lasts ~5. 5 months Ø Installation starts ~Oct and should complete ~Jan 2004 Ø This frees up the piezoelectric, 2 DOF EPI systems at LLO for possible subsequent installation at LHO to help with high winds G 030068 -00 -D LIGO I 10
Commissioning: SEI Upgrade Hydraulic External Pre-Isolator (HEPI) electro-Magnetic External Pre-Isolator (MEPI) CROSSBEAM OFFLOAD SPRINGS HAM CROSSBEAM AM STIFFENING BE HYDRAULIC ACTUATOR (HORIZONTAL) OFFLOAD SPRING HYDRAULIC LINES & VALVES BSC PIER G 030068 -00 -D ELECTRO-MAGNETIC ACTUATORS LIGO I 11
Thermal Lensing q RF sideband efficiency is very low Ø Efficiency: TEM 00 SB power at antisymmetric port, relative to input SB power Ø H 1 efficiency: ~6% Ø Need a stable PRM: lack of ITM thermal lens makes g 1·g 2 > 1 Ø Currently see some lensing in H 1 Bad mode q Arm power Possible solutions RF sidebands in PRM overlap ITM Heating Ø Change RM (w/ new ROC); 6 month lead time Ø Add the missing heat to ITMs with another source Ø 20 -25 W PSL with additional LWE amplifier G 030068 -00 -D DC (carrier) LIGO I RF sidebands 12
Optical Gain Increase for LSC Photodiodes q Dynamic range problem: 1000 x Ø Locking ~100 m. A / running ~100 m. A Ø EO shutter range: 200 -700 Ø Solutions: v Two EO shutters running in series v Separate PDs for locking (low power) and running (high power) v Remote dial for laser power ASI Servo AS Port q q ASI signal dominant! Multiple AS port detectors Ø H 1: PAS = 500 -600 m. W 4 detectors Ø L 1: PAS = ~20 -30 m. W 1 detector G 030068 -00 -D LIGO I 13
Shot Noise Sensitivity q AS port: project a factor of ~2 shortfall H 2 Sensitivity with 50 -70 m. A of Light Ø Reasonable SB efficiency with thermal lensing will get us there Ø Output mode cleaner for AS would also get factor of ~2, may also be desirable to eliminate scattered/junk light q Factor of 6 short only 10 x more light avail. Pick-off detector G 030068 -00 -D LIGO I 14
Acoustic Peaks: Scattering/Clipping q q q Peaks occur in 80 -1000 Hz band, at a level 10 -100 x the SRD Source for H 1/H 2 coincidences(? ) Should consider: Ø Ø Ø Active ISCT beam direction stabilization Acoustic isolation improvements: ISC tables only, or all LVEA? Modify output periscopes/mirror mounts: stiffer, damped Mount Faraday isolators onto ISC tables Larger in-vacuum Faraday, larger EO shutters Acoustic In-vacuum, seismically isolated output bench Excitations loud quiet G 030068 -00 -D LIGO I 15
- Slides: 15