Reports until 18:44, Monday 12 February 2018
H1 SUS
jeffrey.kissel@LIGO.ORG - posted 18:44, Monday 12 February 2018 - last comment - 09:28, Wednesday 14 February 2018(40509)
H1SUSETMY Newly, Fully Suspended Test Mass Fiber Violin Modes Mostly Measured 
J. Kissel, T. Sadecki

Travis and I used a HeNe Laser, QPD, and speaker array to begin characterizing H1SUSETMY's PUM-to-TST fused silica fiber violin modes. We were able to complete the characterization of 3 of the 4 fibers, but we began to have (we believe to be) electronics problems during characterization of the last fiber, so we've left the set turned off but otherwise as is, in hopes the the gremlins will go away by tomorrow morning to characterize the final fiber.

I've exported the data, and intent to process it in detail as I've done for ITMX (see LHO aLOG 39163), but for now preliminary results are as follows (under the "Answer" column):

Freq resolution 62.5mHz
(400 lines with 25 Hz span)

+X / +Y (S1400157; Partial Suspended Fundamental: 504.5 Hz)

	Freq Band / Hz	Answer / Hz	nAvgs	Exc Amp / mV		FileName
1st 	490 515		504.8 		10 	250 		0003
2nd 	990 1015	999.8125	10	250 		0004
3rd	1460 1485	1471.3125	10	250		0005
4th	1975 2000	1980		10	250	        0006
5th	2450 2475	2460.3125	10	500 		0007
6th	2925 2950	2939.625	10	500 		0008

-X / +Y (S1400159; Partially Suspended Fundamental: 503.0 Hz)

1st	490 515		503.625		10	500		0009
2nd	990 1015	1000.3125	10	500		0010
3rd	1460 1485	1470.375	10	500		0011		
4th	1975 2000	1979.4375	10	500		0012
5th	2450 2475	2459.4375	10	500		0013
6th	2925 2950	2939.375	10	500		0014

+X / -Y  (S1800486; Partially Suspended Fundamental: 513.25 Hz)

1st	500 525		512.75		10	500		0015
2nd	1000 1025	1016.8125	10	500		0016	
3rd	1490 1515	1500.375	10	500		0017
4th	1975 2000	1979.5625	10	500		0018
5th	2450 2475	2459.375	10	500		0019
6th	2925 2950	2939.3125	10	500		0020


So far, the difference between fully suspended and partially suspended values look consistent with the ~0.5 Hz shift down in frequency as seen on ITMX.

Note, we tried upgrading the HeNe laser to a spare fiber-coupled optical lever laser as requested by Angus in LHO aLOG 40300, but the output coupler we were given collimated the beam to much larger than we needed (a ~10mm beam for a ~3mm QPD). Also, we were seeing a large amount of glitch-like impulses while taking the ASD of the QPD SUM output. A scope, time-series reading of the QPD output showed no glitching at any time scale. Suspecting the new laser, we tried out the old, supposedly noisy one. Simultaneously, I found that the SR785 input settings were DC coupled, and switched to A-B with AC coupling. Either the laser swap or the AC coupling fixed the problem, but since we were on a roll, we didn't switch back to the new spare optical lever laser. All of today's measurements were taken with the old HeNe laser.
Comments related to this report
jeffrey.kissel@LIGO.ORG - 09:28, Wednesday 14 February 2018 (40525)
Link 

I've fully processed the data, and I'm sad to say that this data set us much more poor than what we got for ITMX (LHO aLOG 39163).

(1) With all of the electronics problems, and the lack of outside-world wifi at the end stations, we couldn't look at ITMX's results results during the measurement, and I ended up chasing features of the electronics above the 3rd harmonic. In other words, the frequencies of the ~2kHz and above modes are junk. Don't trust them.

(2) We didn't spend the time to characterize the partially suspended violin mode fibers beyond the fundamental, so the comparison between partially suspended and fully suspended is not as complete.

Attached are the same plots as before however, just for consistency.

Below is the completed table -- to the best we can -- for the fully suspended, in-air violin mode measurements.

Fiber       S/N         Harmonic     Partially      Fully       df (F-P)
+X / +Y     S1400157    1st          504.5          504.81       +0.31
                        2nd          No Data        999.81       n/a
                        3rd          No Data       1471.31       n/a

-X / +Y     S1400159    1st          503.0          503.63       +0.63
                        2nd          No Data       1000.19       n/a
                        3rd          No Data       1470.38       n/a

+X / -Y     S1800486    1st          513.25         512.75       -0.50
                        2nd          No Data       1016.75       n/a
                        3rd          No Data       1500.31       n/a

-X / -Y     S1800491    1st          510.5          509.88       -0.63
                        2nd          No Data       1008.69       n/a
                        3rd          No Data       1492.31       n/a

Please note I state in the above entry that "So far, the difference between fully suspended and partially suspended values look consistent with the ~0.5 Hz shift down in frequency as seen on ITMX." From the table in this entry, it is obvious this is incorrect, and some skew up and others skew down in frequency.
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