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LIGO-G000298-00-W Performance of the LIGO I PSL at the LIGO Hanford Observatory Rick Savage LIGO Hanford Observatory Laser Zentrum Hannover November 15,2000.

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Presentation on theme: "LIGO-G000298-00-W Performance of the LIGO I PSL at the LIGO Hanford Observatory Rick Savage LIGO Hanford Observatory Laser Zentrum Hannover November 15,2000."— Presentation transcript:

1 LIGO-G000298-00-W Performance of the LIGO I PSL at the LIGO Hanford Observatory Rick Savage LIGO Hanford Observatory Laser Zentrum Hannover November 15,2000

2 LIGO-G000298-00-W High-power Laser Development Meeting 2 Chronology 2-km Interferometer PSL »Begin installation – Fall 1998 »Begin operation – December 1998 –Frequency servo (FSS)operational –PMC servo operational –Power stabilization servo (ISS) operational »15-m modecleaner on-line 4-km Interferometer PSL »Begin installation – 10/00 –Power up laser – 10/00 »Simplified optical layout

3 LIGO-G000298-00-W High-power Laser Development Meeting 3 Topics … LIGO 10-W laser »Reliability –Head –Power supply »Output power stability »Beam quality »Frequency stabilization –Present noise level –Noise sources Mount resonances Acoustic coupling Table leg resonances Doppler shifts from bulk motion Simplified optical layout

4 LIGO-G000298-00-W High-power Laser Development Meeting 4 … Topics Pre-modecleaner »Atmospheric pressure sensitivity »Finesse too low »Cavity losses

5 LIGO-G000298-00-W High-power Laser Development Meeting 5 10-W Laser Reliability … Head – »>16,000 hours continuous operation without adjustment »Output power 8 watts –Power decreases when either MO or PA current increased Re-alignment not attempted – complicated by EOM between MO and PA »Beam quality - PMC visibility >93%

6 LIGO-G000298-00-W High-power Laser Development Meeting 6 … 10-W Laser Reliability Power supply - »Rotary encoder failures ~ 3 times –Unable to reduce PA diode current – <one hour to replace in field »PS fault failures ~ 20 times –Suspect over-voltage protection circuitry –Defeating circuitry may have helped on some supplies

7 LIGO-G000298-00-W High-power Laser Development Meeting 7 Frequency Stabilization

8 LIGO-G000298-00-W High-power Laser Development Meeting 8 Frequency noise – mount resonances - All New Focus mounts replaced with Newport U100A mounts -Lab measurements indicate New Focus clamping forks undesirable U100 A mounts preferred, Klinger mounts slightly worse

9 LIGO-G000298-00-W High-power Laser Development Meeting 9 Frequency noise - enclosure acoustics - Reverberation time of enclosure reduced. - Little affect on the mount resonances.

10 LIGO-G000298-00-W High-power Laser Development Meeting 10 Frequency noise – table acoustics - Acoustics driving bottom of optical table - Acoustic skirt for table being designed.

11 LIGO-G000298-00-W High-power Laser Development Meeting 11 Freq. noise – Table motion Doppler shifts Table and reference cavity acceleration Table Ref. Cav. Freq. noise from Doppler shift Doppler shift ~ f o (v/c) = v/ = a/(2  f  -Longitudinal table motion not the cause of noise -Vertical motion suspect – rotating periscope??

12 LIGO-G000298-00-W High-power Laser Development Meeting 12 Frequency noise – table leg resonances Bolts tight Bolts loose Six adjustable legs Being replaced with three fixed legs

13 LIGO-G000298-00-W High-power Laser Development Meeting 13 Revised Optical Layout

14 LIGO-G000298-00-W High-power Laser Development Meeting 14 Frequency glitches FSS Fast PMC Error Ref. Cav. RFPD DC -Observed at rate of 10’s per second - Eliminated by adjusting NPRO pump diode current by 0.02 amps

15 LIGO-G000298-00-W High-power Laser Development Meeting 15 Pre-modecleaner - performance Noise PSD ratio of ~ 5 >> f c ~ 0.8 MHz f c for present PMC ~ 1.7 MHz >> ASD ~ 2 x req.

16 LIGO-G000298-00-W High-power Laser Development Meeting 16 Pre-modecleaner – atmospheric pressure strain ~ 2.7 x 10 -9 per Pascal Sensitivity to atmospheric pressure changes

17 LIGO-G000298-00-W High-power Laser Development Meeting 17 Pre-modecleaner - losses P in = 7.84 W P out = 6.8 W  T = P out / P in = T 2 / (L+T) 2 T= 1.45% Measure:  T = P out / (P in x visibility) = 0.93 >> L = 515 ppm per mirror

18 LIGO-G000298-00-W High-power Laser Development Meeting 18 Relative power fluctuations 9/11/0011/07/00 Atmospheric pressure in LVEA 10-W laser output power monitor inside head 7.7 W 8.1 W 60 days


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