Displaying reports 69401-69420 of 77116.Go to page Start 3467 3468 3469 3470 3471 3472 3473 3474 3475 End
Reports until 17:36, Wednesday 02 October 2013
H1 General
jeffrey.kissel@LIGO.ORG - posted 17:36, Wednesday 02 October 2013 (7968)
Current IMC Status Captured before IMC ODC channel implementation 
J. Kissel, A. Pele, C. Wipf, S. Dwyer

In hopes to further progress towards a speedy recovery from a power failure, we have done the following:
(1) Captured and committed the following safe.snap files:
${userapps}/release/sus/h1/burtfiles/h1susmc1_safe.snap
${userapps}/release/sus/h1/burtfiles/h1susmc2_safe.snap
${userapps}/release/sus/h1/burtfiles/h1susmc3_safe.snap
${userapps}/release/sus/h1/burtfiles/h1susim_safe.snap

${userapps}/release/asc/h1/burtfiles/h1ascimc_safe.snap

${userapps}/release/lsc/h1/burtfiles/h1lsc_safe.snap

(2) ensured that all relevant safe.snaps in the target directory are soft links to the userapps repo
/opt/rtcds/lho/h1/target/h1susmc1/h1susmc1epics/burt/safe.snap -> /opt/rtcds/userapps/release/sus/h1/burtfiles/h1susmc1_safe.snap
/opt/rtcds/lho/h1/target/h1susmc2/h1susmc2epics/burt/safe.snap -> /opt/rtcds/userapps/release/sus/h1/burtfiles/h1susmc2_safe.snap
/opt/rtcds/lho/h1/target/h1susmc3/h1susmc3epics/burt/safe.snap -> /opt/rtcds/userapps/release/sus/h1/burtfiles/h1susmc3_safe.snap
/opt/rtcds/lho/h1/target/h1susim/h1susimepics/burt/safe.snap -> /opt/rtcds/userapps/release/sus/h1/burtfiles/h1susim_safe.snap

/opt/rtcds/lho/h1/target/h1ascimc/h1ascimcepics/burt/safe.snap -> /opt/rtcds/userapps/release/asc/h1/burtfiles/h1ascimc_safe.snap  ## This one wasn't a soft link before now 

/opt/rtcds/lho/h1/target/h1lsc/h1lscepics/burt/safe.snap -> /opt/rtcds/userapps/release/lsc/h1/burtfiles/h1lsc_safe.snap
(3) edited MClockwatch code to ensure that the ASC outputs on all stages of each IMC optic (H1:SUS-MC[1,2,3]_M[1,2,3]_LOCK_[P,Y]), and the the lowest stage LSC output on MC2 (H1:SUS-MC2_M3_LOCK_L) are turned ON in the "unlocked" portion of 
/opt/rtcds/userapps/release/ioo/h1/scripts/imc/sballmer/MClockwatch
which are now the only LOCK settings that are different between the SAFE state and the READY state.

Note, in absence of the transitions between SAFE and READY, the user still has to turn on the MASTERSWITCH (to get to DAMPED) and the OPTICALIGN alignment offsets (to get to ALIGNED) for MC1, MC2, and MC3. Simply starting the MClockwatch script will then transition MC2 to its READY state, and begin to try and lock the mode cleaner. Remember that turning on the ASCIMC control is now triggered by the front end, so as long as its settings are properly restored on startup (which the above three steps should now ensure), the user and MClockwatch script should not have to worry about it.
H1 SUS
arnaud.pele@LIGO.ORG - posted 16:52, Wednesday 02 October 2013 (7967)
Snapshots

Captured and commited on the svn MC1 MC2 MC3 and IMs safe snapshot with its most recent alignment offset values.

When restoring those snapshots, the lock filters output switches need to be engaged to lock the cavity.

H1 CDS
james.batch@LIGO.ORG - posted 16:46, Wednesday 02 October 2013 (7966)
Repaired Simulink Webview for creating web pages of models

The process to generate the simulink webview pages for browsing models with web browsers has been repaired to be functional again.

1. The main script became broken when a directory path was changed to a non-existent directory.

2. The simlink directory in which the generated files were to be placed changed ownership such that the controls user could no longer create new files and directories.

The web page to view the models is https://lhocds.ligo-wa.caltech.edu/simulink and new pages have been generated as of 12:00 PDT. New pages are generated 4 times each day at 6 hour intervals.

LHO General
patrick.thomas@LIGO.ORG - posted 16:37, Wednesday 02 October 2013 (7957)
Ops Summary 
Low level alarms for mid X instrument air pressure, Kyle R. notified

09:32 Sheila D., Pablo H. and Kiwamu I. entering HAM1 to measure the beam profile of the reflected light from the PRM through the Faraday isolator
09:40 Cheryl V. going to the end X TMS lab
09:57 Safety review tour
10:29 Ace portable toilets onsite for maintenance
10:50 Betsy W. found the dust monitor at end X inside the electronics rack. She set the audible alarm limits and moved it into the clean room over ETMX
10:53 Sheila D., Pablo H. and Kiwamu I. done with the measurement in HAM1
11:26 Safety review tour has left the LVEA
12:37 Betsy W. getting parts from the rack by HAM2
12:43 Large dust spike reported by dust monitor at end X, nobody appeared to be in the VEA (see below)
13:01 Cheryl V. heading back from end X
13:29 Filiberto C. and Aaron S. working on cabling in middle high bay at end Y
13:49 Timing errors for end Y ISC, Aaron S. had powered down the IO chassis
15:47 Dave B. attempting to bring back the SEI, SUS and ISC frontends at end Y
15:53 Thomas V. done working on baffles
15:59 Justin B. transitioned the LVEA to laser safe (WP 4161)

Kyle R. replaced the instrument air transducer at end X (WP 4160)

Large spike in only > .3 micron particle counts measured in the clean room at end Y from 12:41 - 13:13. (see attached plot)
Dust monitor is labeled 'S'. Calibration date: 8/9/13 Calibration due date: 8/9/14. Cause as of yet undetermined.
Non-image files attached to this report
endY.pdf
H1 CDS
david.barker@LIGO.ORG - posted 16:09, Wednesday 02 October 2013 (7965)
EY front ends restarted

Following DC power work at EY which powered down h1iscey's IO Chassis, I restarted all the dolphined front ends at EY. There was an mx_stream glitch in the process, which may have corrupted other front end's data for a minute or so.

LHO VE
kyle.ryan@LIGO.ORG - posted 13:48, Wednesday 02 October 2013 (7961)
Replaced X-mid instrument air transducer 


			
			


		
		


		
		


	
	


	
	


		
		


			
			


		
		


		
		


			
			


		
		


		
		


	
	


	
	


		
		


			
			


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			stefan.ballmer@LIGO.ORG - posted 11:56, Wednesday 02 October 2013 (7959)
			
			


		
		


		
		


			IMC phase jump investigation
			
			


		
		


		
		


			
Rich A., Stefan

In response to yesterday's IMC phase jump (alog 7941) we measured the cable impedance reflection coefficient for the 24.078360MHz cable heading from the PSL rack to the EOM inside the PSL.

Attached is a picture of the measurement. Note
1) The FieldFox internal clock is not very good, but the reference marker corresponds to the actual IMC modulation frequency of 24.078360MHz.
2) The EOM resonance is about one hundred kHz low - we don't get much resonant gain at all.
3) Wiggling that cable didn't produce any visible impedance change.


			
			


		
		


		
		


				Images attached to this report
			
			


		
		


		
		


			
			
			


		
		


		
		


		
		


	
	


	
	


		
		


			
			


		
		


		
		


			
			


		
		


		
		


	
	


	
	


		
		


			
			


				 LHO VE 
				
				


			
			


			
			

			
			


		
		


		
		


			kyle.ryan@LIGO.ORG - posted 11:47, Wednesday 02 October 2013 (7960)
			
			


		
		


		
		


			Changed CP5 PID proportional gain from 1.3 to 1.5
			
			


		
		


		
		


			


			
			


		
		


		
		


	
	


	
	


		
		


			
			


		
		


		
		


			
			


		
		


		
		


	
	


	
	


		
		


			
			


				 H1 ISC 
				
				


			
			


			
			

			
			


		
		


		
		


			keita.kawabe@LIGO.ORG - posted 02:13, Wednesday 02 October 2013  - last comment - 09:23, Tuesday 08 October 2013(7950)
			
			


		
		


		
		


			REFL mode profile measured to be very different from what was expected (Pablo, Keita)
			
			


		
		


		
		


			

	We placed Mode Master downstream of three-mirror Gouy phase matching telescope comprising two tip-tilts and one fixed mirror that is used for REFL WFS. (See the last picture for layout and distances.)



	Note that the measured TT1-TT2 distance is about 1cm shorter than nominal described in Sam Waldman's document (http://dcc.ligo.org/T1000247), TT2-M5 distance is about 14mm longer than nominal, both of which should have been quite acceptable.



	Anyway, we made this measurement and the beam was much smaller than what was expected. The first plot as well as the table below show the measured VS  the expected mode profile coming out of HAM1 propagated through the telescope with the measured mirror distances.



	
		

			
				 
			
				measured, x
			
				measured, y
			
				expected
		

		

			
				M^2
			
				1.04
			
				0.98
			
				1-ish
		

		

			
				Waist radius
			
				1.38 mm
			
				1.15 mm
			
				1.92mm
		

		

			
				Waist position (away from MM head into HAM1)
			
				4.31 m
			
				4.35 m
			
				1.78 m
		

		

			
				Mode overlap between measured and expected
			
				0.872
			
				0.753
			
				1
		

	




	The total mode overlap between the actual beam and what is expected is somewhere between 0.75 and 0.87 (sort of tedious to do the real calculation so I leave it).



	The 2nd plot shows that IF the incoming beam from HAM1 is as expected, in order to explain the measured mode the TT1-TT2 distance labeled as delta1 should be shorter by 4.5cm than was measured for X, or by 5.7cm for Y. This is a huge number, there's no way my distance measurement was that much off.



	The 3rd plot  shows the Gouy shift between TTs (i.e. actuation orthogonality) and WFSs for the WFS sled (i.e. sensing), and it seems like both are quite poor for the measured mode, 26deg for actuation and 35 for sensing are sad though not a complete disaster.



	Anyway, since it's hard to imagine that the ROC of TT1 (+1.7m), TT2 (-0.6m) and M5 (+1.7m) are grossly wrong, and since it's hard to imagine that the distance measurement has a 5 to 6cm error, this should mean either (or some) of the followings:


    
	
  1. 
		T1000247 is wrong about the mode coming out of HAM1.
    2. 
	
  2. 
		IMC mode is not mode matched to the IFO well.
    3. 
	
  3. 
		Astigmatism of curved optics at an angle (there are 3 such optics on HAM1, more on HAM2), each has small effect but maybe they add up. Neither Sam nor I have included this.
    4. 




	The third one doesn't sound likely, but neither Sam nor I have thought about this.


			
			


		
		


		
		


				Images attached to this report
			
			


		
		


		
		


			
			
			
			
			
			


		
		


		
		


		
		


				Non-image files attached to this report
			
			


		
		


		
		


			

				

				
REFL_msmt1.m

			

			
			


		
		


		
		






	
	


		Comments related to this report
		
		


	
	


	
	


		keita.kawabe@LIGO.ORG - 02:06, Wednesday 02 October 2013 (7951)
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	One quick thing to do is to measure the beam before it gets to the telescope by inserting M6 upstream of the TT1 to direct the beam to the Mode Master.


		
		


	
	


	
	


		lisa.barsotti@LIGO.ORG - 06:17, Wednesday 02 October 2013 (7952)
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Yes, please, measure the beam before the TTs. 
The original calculations were done by assuming that beam reaching HAM1 was perfectly matched to PRM.
I don't think we have reasons to believe that's true..
The "nominal" q of the beam right before the first tip-tilt RM1 is:

% REFL in-vacuum path beam propagation, HAM1 drawing v10
% https://dcc.ligo.org/LIGO-D1000313-v10
% LisaBar, August 14, 2013

q_in = 1.03+13.1i;  % Beam on HAM1 calculated from CalculatePRM.m 
                    % Lisa: we don't have a measurement yet which confirms
                    % this number! 




		
		


	
	


	
	


		guido.mueller@LIGO.ORG - 07:35, Wednesday 02 October 2013 (7953)
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I don't think the table in T1000247 is correct. The beam from PMMT2 goes through the Faraday, hits PMMT1 and is then send to HAM1. 
This is a) longer than 2.5m and b) adds PMMT1's curvature to it. 
Did you include this?


		
		


	
	


	
	


		lisa.barsotti@LIGO.ORG - 08:33, Wednesday 02 October 2013 (7956)
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Yes, PMMT1 is included, it is just a typo in the note (there are two PMMT2!). 

Anyway, let's redo the calculations with the as-built parameters, and cross check with the measurements before the REFL telescope.


		
		


	
	


	
	


		sheila.dwyer@LIGO.ORG - 11:18, Wednesday 02 October 2013 (7958)
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Kiwamu and Pablo and I measured the mode before the TTs by moving the BS for the RF detector to 16 inches after M2, with the front of the mode master 40 inches from the BS we measured:




 
xyr




M^2	0.971.031.00




2Wo (mm)3.588	3.532	3.567




Z0	(m)-2.387-3.578	-3.026 







		
		


	
	


	
	


		sheila.dwyer@LIGO.ORG - 17:06, Wednesday 02 October 2013 (7962)
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The overlap between the mode measured before the Tip tilts and the mode measured after is 93% for X, 87% for Y.  I used Lisa's alm mode model attached to D1000313, added Keita's measurements of the distances from RM1 to RM2 and M5, but didn't include the tilt of the optics.  

From this measurement before the tip tilts (projected through Keita's measurements of distances), the gouy phase separation is a little better than from Keita's measurement, WFS X=65 degrees, WFSY 60 degrees, TT x=56 TT y 50 degrees.  





		
		


	
	






Non-image files attached to this comment
	
	













	
	


		paul.fulda@LIGO.ORG - 16:03, Wednesday 02 October 2013 (7963)
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	I checked to see how far wrong things in HAM2 would have to be in order to explain the beam waist sizes measured by Sheila before the tip-tilts. 



	I used the design parameters for IM2 and IM3 Rcs (except where varied), design parameters for HAM2 optics placement as found in E1200616 (except where varied), the measured value of PRM HR Rc of -10.9478m, and the design IMC parameters to get the starting beam parameter. The attached plots show the forward beam waist size (identical to the IMC waist size) and the return from PRM beam waist size, over variations in IM2 and IM3 Rc, and IM2->IM3 and IM4->PRM distance. At the design values (at the x-axis midpoint), the return x-waist size matches the forward waist size.



	It looks like things in HAM2 would have to be further off from the design than is probably likely, in order to explain the measured beam waist size before the tip-tilts.


		
		


	
	






Non-image files attached to this comment
	
	













	
	


		paul.fulda@LIGO.ORG - 11:18, Thursday 03 October 2013 (7973)
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	Propagating the IMC transmission beam through the "as-built" IMs, back from the PRM, off the FI rejected beam pick off mirror and onto HAM1 to the location where Sheila measured gives:



	
		

			
				axis
			
				parameter
			
				value
		

		

			
				x
			
				w0
			
				2.123mm
		

		

			
				y
			
				w0
			
				2.101mm
		

		

			
				x
			
				z
			
				-2.469m
		

		

			
				y
			
				z
			
				-2.150m
		

		

			
				x
			
				q
			
				-2.469+13.310i
		

		

			
				y
			
				q
			
				-2.150+13.035i
		

		

			
				x
			
				w
			
				2.159mm
		

		

			
				y
			
				w
			
				2.129mm
		

		

			
				x
			
				Rc
			
				-74.21m
		

		

			
				y
			
				Rc
			
				-81.16m
		

	




	I did not yet consider the calcite wedge polarizer effect on the beam parameter, and I didn't account for the thickness of the septum viewport.



	The overlap of these beam parameters with Sheila's measured parameters are:



	x overlap = 0.945



	y overlap = 0.934



	I'm including the Finesse kat file I used for the calculation, which has a list of all the parameters I used at the top. I also include that list here for convenience:



	# H1_IMCtoPRC_matching.kat

	# A file for checking the expected beam parameter in direct reflection from the PRM

	# as a function of HAM2 optic RCs and placement positions

	#

	# Mirror curvature parameters taken from the nebula page, except IM2 and IM3 for

	# which the design values were taken

	#

	# Distances taken from E1200616_v7 except where otherwise noted

	#

	# IMCC Curvature = 27275mm

	# MC1->MC2 = 16240.6mm

	# MC2->MC3 = 16240.6mm

	# MC3->MC1 = 465mmm

	# MC3 substrate path length = 84.5mm

	# MC3-AR surface to IM1 = 428.2mm

	# IM1->IM2 = 1293.8mm

	# IM2 Rc = 12800mm

	# IM2 AOI = 7deg

	# IM2->IM3 = 1170.4mm

	# IM3 Rc = -6240mm

	# IM3 AOI = 7.1deg

	# IM3->IM4 = 1174.5mm

	# IM4->PRM-AR surface = 413.5mm

	# PRM substrate path length = 73.7mm

	# PRM Rc = 10947.8mm (from Rodica's measurement value)

	# IM2->FIrejected pick off mirror = 1.012m (From Luke Williams)

	# FI rejected pick off mirror->HAM1 mode master location =3.0175m (Estimated from

	# Sheila's alog entry, HAM2 drawing, and 27.6" for HAM1 table edge to HAM2 table edge)

	#####################################################################################


		
		


	
	






Non-image files attached to this comment
	
	













	
	


		keita.kawabe@LIGO.ORG - 13:36, Thursday 03 October 2013 (7974)
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	If anything, my measurement is a bit more suspicious than Sheila's, as mine is downstream of TTs in air and they are moving (mostly in PIT).


		
		


	
	


	
	


		giacomo.ciani@LIGO.ORG - 08:33, Monday 07 October 2013 (8016)
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	x: w0=2.1214815mm  w=2.1611823mm z=2.5828797m z_R=13.28883m Rc=70.953463m



	   q=(2.58288 + 13.2888i) gamma=159.64397urad



	   y: w0=2.1012776mm  w=2.1297726mm z=2.1542686m z_R=13.036923m Rc=81.049425m



	   q=(2.15427 + 13.0369i) gamma=161.17895urad



	

		x: w0=2.1214815mm  w=2.1611823mm z=2.5828797m z_R=13.28883m Rc=70.953463m

	

		   q=(2.58288 + 13.2888i) gamma=159.64397urad

	

		   y: w0=2.1012776mm  w=2.1297726mm z=2.1542686m z_R=13.036923m Rc=81.049425m

	

		   q=(2.15427 + 13.0369i) gamma=161.17895urad

	

		

			x: w0=2.1214815mm  w=2.1611823mm z=2.5828797m z_R=13.28883m Rc=70.953463m

		

			   q=(2.58288 + 13.2888i) gamma=159.64397urad

		

			   y: w0=2.1012776mm  w=2.1297726mm z=2.1542686m z_R=13.036923m Rc=81.049425m

		

			   q=(2.15427 + 13.0369i) gamma=161.17895urad

		

			

				x: w0=2.1214815mm  w=2.1611823mm z=2.5828797m z_R=13.28883m Rc=70.953463m

			

				   q=(2.58288 + 13.2888i) gamma=159.64397urad

			

				   y: w0=2.1012776mm  w=2.1297726mm z=2.1542686m z_R=13.036923m Rc=81.049425m

			

				   q=(2.15427 + 13.0369i) gamma=161.17895urad

			

				

					x: w0=2.1214815mm  w=2.1611823mm z=2.5828797m z_R=13.28883m Rc=70.953463m

				

					   q=(2.58288 + 13.2888i) gamma=159.64397urad

				

					   y: w0=2.1012776mm  w=2.1297726mm z=2.1542686m z_R=13.036923m Rc=81.049425m

				

					   q=(2.15427 + 13.0369i) gamma=161.17895uradx: w0=2.1214815mm  w=2.1611823mm z=2.5828797m

				

					 

				

					 

				

					z_R=13.28883m Rc=70.953463m

				

					I retraced the beam, this time accounting for the calcite wedges. The results are not much different, and are summarised in the table below.

				

					 

				

					

						
							

								
									axis
								
									parameter
								
									value
							

							

								
									x
								
									w0
								
									2.121mm
							

							

								
									y
								
									w0
								
									2.101mm
							

							

								
									x
								
									z
								
									-2.583m
							

							

								
									y
								
									z
								
									-2.154m
							

							

								
									x
								
									q
								
									-2.583 + 13.29i
							

							

								
									y
								
									q
								
									-2.154 + 13.04i
							

							

								
									x
								
									w
								
									2.161mm
							

							

								
									y
								
									w
								
									2.130mm
							

							

								
									x
								
									Rc
								
									-70.95m
							

							

								
									y
								
									Rc
								
									-81.05
							

						
					

				

				

					 

			

		

	




		
		


	
	


	
	


		paul.fulda@LIGO.ORG - 08:20, Tuesday 08 October 2013 (8033)
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	Apparently I posted the last comment as Giacomo, sorry about that!


		
		


	
	


	
	


		paul.fulda@LIGO.ORG - 09:23, Tuesday 08 October 2013 (8036)
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	After discussing with Lisa about sign conventions for the beam waist position parameter, I realised that there are errors in some of the parameters I posted above. The mode master gives results as "z0" for waist position relative to the measurement position (z0-z), whereas Finesse gives results as "z" for the measurement position relative to the waist position (z-z0).



	I had thought the convention was different, so I flipped my results to match the mode master convention. This was a mistake, because the conventions are the same, they just give different outputs. To get the q-parameter from the mode master results one should use the formula q = -z0 + i*zR. From the Finesse results one should use the formula q = z + i*zR.



	This means that the z-values, Rc values and the real part of the q-parameters I posted should all have their signs flipped.  Apologies for any confusion I caused here.


		
		


	
	


	
	






		
		


	
	


	
	


		
		


			
			


		
		


		
		


			
			


		
		


		
		


	
	


	
	


		
		


			
			


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			stefan.ballmer@LIGO.ORG - posted 18:38, Tuesday 01 October 2013 (7941)
			
			


		
		


		
		


			IMC demodulation phase rotated again
			
			


		
		


		
		


			

	(Kiwamu, Stefan)



	IMC demodulation phase rotated again for the 4th time...



	After the IMC sideband sweep measurement this morning we noticed that the IMC WFS were no longer stable, and the IMC locking was a bit shaky. Sure enough we found that  the RF phase rotated again, with most of the signal back in the I-phase (we use the Q-phase for feed-back.)



	The 1st attached picture shows the I signal along the x-axis, and the Q signal along the y-axis. Also note that the size of the signal is not much smaller than in the picture from alog 7181 (and we currently has a slightly reduced PSL input power due to the installed 10% and 30% BS for the FI isolation measurement).



	 



	
  • 
		An updated brief history of phase rotation:
		
	
    • 

    

    
	 
    

    
	For now we again adjusted the phase of both length and angle sensors.
    

    
	The new delay setting is in the 2rd attached picture (the old one is in alog 7119 - note that in alog 7119 we used the I-phase for feed-back). Picture 3 shows the I signal along the x-axis, and the Q signal along the y-axis after the LO delay change of 9.75nsec (~85deg).
    

    
	The new WFS phase settings are the same as back in alog 7119 :
    

    
	H1:IMC-WFS_A_SEG1_PHASE_R = -185
    
	H1:IMC-WFS_A_SEG2_PHASE_R = -112
    
	H1:IMC-WFS_A_SEG3_PHASE_R = -185
    
	H1:IMC-WFS_A_SEG4_PHASE_R = -185
    
	H1:IMC-WFS_B_SEG1_PHASE_R = -80
    
	H1:IMC-WFS_B_SEG2_PHASE_R = -132
    
	H1:IMC-WFS_B_SEG3_PHASE_R = -66.5
    
	H1:IMC-WFS_B_SEG4_PHASE_R = -173
    

    
	Before I changed them, the phases were
    

    
	H1:IMC-WFS_A_SEG1_PHASE_R = -90
    
	H1:IMC-WFS_A_SEG2_PHASE_R = -17
    
	H1:IMC-WFS_A_SEG3_PHASE_R = -27
    
	H1:IMC-WFS_A_SEG4_PHASE_R = -22
    
	H1:IMC-WFS_B_SEG1_PHASE_R = +15
    
	H1:IMC-WFS_B_SEG2_PHASE_R = -34
    
	H1:IMC-WFS_B_SEG3_PHASE_R = +28.5
    
	H1:IMC-WFS_B_SEG4_PHASE_R = -81
    

    
	In conclusion - we are back in the same "RF phase state" as in elog 7119.
    
	 
    

			
			
    

		
		
    

		
		
    

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				 H1 ISC 
				
				
    

			
			
    

			
			

			
			
    

		
		
    

		
		
    

			joseph.gleason@LIGO.ORG - posted 18:12, Tuesday 01 October 2013 (7949)
			
			
    

		
		
    

		
		
    

			HAM1 REFL path aligned through ISC sled
			
			
    

		
		
    

		
		
    

			
    I've aligned the REFL beam from RM2 through the ISC sled. The beam from the pick-off BS is temporarily dumped in a spare black glass V-dump. The beam in the sled is well aligned through the first two lenses and the first 2 turning mirrors but is about 8mm high on the last turning mirror. It seems that the turning mirrors on the sled need to be adjusted to fix this but I wanted to consult with Keita about this first as it was my understanding that these had already been aligned in the lab.
    

			
			
    

		
		
    

		
		
    

	
	
    

	
	
    

		
		
    

			
			
    

		
		
    

		
		
    

			
			
    

		
		
    

		
		
    

	
	
    

	
	
    

		
		
    

			
			
    

				 H1 IOO 
				
				
    

			
			
    

			
			

			
			
    

		
		
    

		
		
    

			stefan.ballmer@LIGO.ORG - posted 12:11, Tuesday 01 October 2013  - last comment - 07:49, Wednesday 02 October 2013(7934)
			
			
    

		
		
    

		
		
    

			Faraday isolation ratio measurement
			
			
    

		
		
    

		
		
    

			
    (Kiwamu, Paul, Stefan)
This morning we found the back-reflection from the PRM, leaking through the Faraday, back on the PSL table.
We measured the following powers:
- direct beam, sampled by ~30% BS: 339mWatt
- return beam, sampled by the same ~30% BS: 37.0uWatt
- as reference, we also measured the power on the REFL beam on ISCT1, just after the periscope: 6.94mWatt

Faraday isolation ratio: 37.0uW/339mW, minus other losses (IMC visibility, PRM reflectivity)
    

			
			
    

		
		
    



    

	
	
    

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		kiwamu.izumi@LIGO.ORG - 07:43, Wednesday 02 October 2013 (7954)
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	Some more small information regarding to this measurement:
    

      
	
    • 
		We left these two temporary beam splitters in the main beam path just in case somebody wants to return to this measurement in some near future.
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    • 
		When we obtained the returning beam at the PSL, we took this opportunity to realign the REFL path on ISCT1. The beam is aligned such that it hits the center of almost every optics, Length RFPD and BBPD.
      • 
	
    • 
		The reason why we didn't get the returning beam the other day (see alog 7926) was simply because of a big misalignment in PRM which we noticed after we came out from the PSL. It was not difficult find it once the PRM was coarsely aligned back to the nominal point.
      • 
	
    • 
		We used a hand-held type power meter, Ophir Vega, for this power measurement.
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		kiwamu.izumi@LIGO.ORG - 07:49, Wednesday 02 October 2013 (7955)
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	The "good" alignment in PRM is :
    

    
	
    

		
		
    

	
	
    



    

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