Installation of new MPR

Harald Lück

ILIAS WP1 meeting, June 14th 2005

Old MPR: T=1.35%

New MPR: T≈ 900ppm

Timeline of MPR exchange

• 02.05: Opened vacuum vessel & exchanged MPR

• 03.05: Installed attenuator. Prealigned MPR• ….spent some time with aligning• 09.05 Ifo aligned and flashing• 12.05 stable PR Michelson lock• 19.05 1hour 2f lock @ 3.5kHz• 22.05 tuned down to 1kHz

Power in PR Cavity

• Input power: 1.7W incident to MPR.

• Old MPR (1.35%) ≈ 500W ≈ 1.7 * 4/ 1.35%

• New MPR: up to 2kW (normally ~1.5kW)

• Expected PR factor >2000 ↔ 3.4kW

• Have not yet determined where we lose the power (→Stefan)

Power measurements

• Power transmitted through mirrors– MFE: 13mW/10ppm → 1.3kW– MFN: 11mW/10ppm → 1.1W

10ppm for MFN guessed to be the same as MFE

– BS AR ca. 30mW/44ppm → 1.4kW– MCN, MCE very high losses due to lens

Cavity pole measurement

Curve fit gives: 15.14 Hz +-0.15 HzSimulations with 126ppm transm. for MCE/N, 50ppm for MFE/N, and 200ppm for BS/AR.BS thermal lens set to 10k for new configurations give a pole f of 15 Hz.

Simulations

Fit pole freq: 141Hz ----------------------------------------------------------- pole freq: 18.4 Hz------------------------------------------------------------ pole freq: 15.0 Hz

Transfer function with old MPR (1.35%)

Fit gives 147Hz pole frequency

Wire attenuator, 15µm glas fibre, 0.3% attenuation/round tripNot needed with the present losses

Wire attenuator in front of MPRr

Thermal lensing in BSoutput mode pattern

Directly after relocking

f=20km

A few minutes after relocking

f= 8km

Building up the thermal lensdark port power after relocking for PR and DR Michelson

0 10 20 30 40 50 60 70 80 90 1000

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Time (secs)

Am

pli

tud

e (V

)

DR MIDVIS

PR MIDV

IS

Increasing ROC heater powerdual recycled lock, 1kHz detuned

0 0.5 1 1.5 2 2.5 33

3.5

4

4.5

Time (Hours)

Am

pli

tud

e (V

-rm

s)

SPOTPOS:MCE:SUMfs = 1 : 2005-06-01 10:59:47

0 0.5 1 1.5 2 2.5 32.5

3

3.5

4

Time (Hours)

Am

pli

tud

e (V

-rm

s) SPOTPOS:MCN:SUMfs = 1 : 2005-06-01 10:59:47

0 0.5 1 1.5 2 2.5 3

-4

-3.5

-3

Time (Hours)

Am

pli

tud

e (V

-rm

s)

SPOTPOS:MFE:SUMfs = 1 : 2005-06-01 10:59:47

0 0.5 1 1.5 2 2.5 3-4

-3.5

-3

-2.5

Time (Hours)

Am

pli

tud

e (V

-rm

s)

SPOTPOS:MFN:SUMfs = 1 : 2005-06-01 10:59:47

0.5 1 1.5 2 2.51.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

Time (Hours)

Am

pli

tud

e (V

-rm

s)

AAMI:SCAN:DENOMfs = 1 : 2005-06-01 10:59:47Dark port power

PR cavity power

75W 80W 85W 90W 98W