aLIGO LHO Logbook

H1 TCS

camilla.compton@LIGO.ORG - posted 10:09, Tuesday 29 November 2022 (66036)

ITMX and ITMY absorption plot

Dan, Mitchell, Camilla. ITMX (which has known point absorbers) is absorbing ~30% more power than ITMY.

Measured IFO beam self-heating absorption using this morning's lockoss. Dan left on the the CO2's on after loosing lock (66054) so that they don't change the state of the ITMs. I have now turned both CO2'soff to start locking and Dan's reverted ISC_LOCK.

See attached plot made using Aidan's absorption plot script (instruction in TCS wiki) from in /ligo/gitcommon/labutils/hws_absorption_fit/nov2022.

ITMX: 115mW absorbed = 490ppb

ITMY: 90mW absrobed = 385ppb

with arm power 235kW from H1:ASC-{X/Y}_PWR_CIRC_OUT16. Previously measured 430ppb for ITMX (62782) and 370ppb for ITMY (62468) .

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Also tried similar comparison of spherical power during power up after 50W and got same result:

	Ring heater test 1350878491		Power up 25W to 50W* @1353397628 compared to +1h30 (locked with no CO2)
	Measured Spherical Power (uD)	Simulated	Measured Spherical Power (uD)	Simulated (different from self-heating gains)
ITMX	-157	-67	80	17
ITMY	-150	-67	60	23

Measured Spherical Power (uD) ITMX/ITMY at power up 80/60=1.33 ~ 30% more absorption in ITMX. Both ring heater test results are similar to within 5%.

Using self heating after 50W is reached as when moving spots the HWS measured probe pixel power at IX slightly changes.

Previously tried after ring heater test in 65286

Simulated = H1:TCS-SIM_ITMX_SUB_DEFOCUS_FULL_SINGLE_PASS_OUTPUT channel.

Images attached to this report