The outer leak appears to be located on the BSC side of the septum plate and near 7:00 (bottom left)  looking towards HAM1.

The alignment jumped twice by a large amount and it took us some time to recover.

Once it was supposedly Kyle hitting something, and ITM didn't come back exactly to the same position.

Another time I don't know what happened.

More Serial Numbers:

Actuators (installed 6/27)

• H1:  179
• V1:  097
• H2:  178
• V2:  118
• H3:  176
• V3:  007

CPS Probes (as slotted in satelite boxes)

• H1:  12009
• V1:  12025
• H2:  12012
• V2:  12016
• H3:  12036
• V3:  12030

And...lots of YAW bias gets the ETMY aligned to get the beam back on to the ITMY baffle PDs. The ETMY bias for rough alignment is:

P = -2700

Y = +14200

I haven't seen any flashing yet that looks like a Fabry-Perot resonance, but at least all of the suspensions are close enough in alignment to proceed. Since the TMSY and ETMY both have large yaw biases, we can still hope that they can be mostly relieved by yawing the HEPI (assuming they need the same direction of yaw). Because of the double-loop nature of the quads, we should also get some ITMY pitch relief from pitching its HEPI.

From the flashing that can be seen from the ITMY spool cam, it seems like the return green beam is hitting the ITMY baffle at the edge around the mirror, at the 2 o'clock position look at the ITM from the spool.

While trying to get the video rerouted to the control room as well as EY I will look at hooking up a FiBox to the green light signal. Will talk to Keita about this.

There is something funny about the numbers here. The claim is that the ITM alignment was off by about 25 micro-radians, and that correcting this uses about 1/2 of the pitch control range (I assume this is at the TOP stage). However, according to T1100595-v1, the control range of the quad, from the TOP stage, is 1.14 mrad in pitch; it is a little unclear as to whether this is +/- 1.14 mrad or a 1.14 mrad total swing; either way, it is much larger than 25 urad -- it should take less than 1/10 of the range to correct it.

I think its funny too. Using ~50000 cts (as measured at the DAC outputs for the face OSEMs on TOP) seems like its close to the 2¹⁷ limit for the DAC.

Should have checked the coil driver readbacks to find out how much current/voltage was being used to make sure there is no attenuation happening downstream.

Jeff K and I found the basic problem with the ITMY alignment numbers. There is a factor of 10 error in the observed pitch misalignment number. The 0.21 m above should be 2.1 m (6 * 0.34 m). The pitch offset is thus 250 micro-radians. We also noted that there seems to be a factor of 2 discrepancy between the designed input range for the TOP driver and the DAC output range, so that we can only access half the current range for each BOSEM: the TOP driver was designed to give +/- 200 ma for each coil, but we can only go to +/- 100 ma. So, the 250 micro-rad of offset is about half the pitch bias range we have available, which is about half of what we should have.

P. Fritschel, J. Kissel

The confusion lies in Rana's calculation of the total distance for beam travel:
1000 cts of torque = beam moves top to bottom of ETMY
the ETMY is 34cm in diameter.
So, a 6300 cts offset, is
6300 [ct]* 34/1000 [cm/ct] = 214 [cm] = 2.14 [m]
not ~0.210 [m] as Rana uses in his calculation (i.e. he's off by a factor of 10). So, correcting the number in his calculation, we get

pitch offset = torque [ct] / (2 L) % factor of two from "optical lever" effect see G1200698
             = (2.14 m / 4000 m) / 2 
             = 250 micro radians. 


This jives with the predicted range of the QUAD TOP driver and the current monitors:

Predicted Range
T0900232 says, in section 6.1: 
"As the input voltage is specified as 10V* and the voltage gain of the circuit is 1.2** the voltage swing of each output terminal is +/-12[V]. As each output resistor is 40 Ohms, and the [B]OSEM coil resistance is 40 Ohms, the total output resistance is 
     (40 [Ohms] + 40 [Ohms] + 40 [Ohms]) = 120 [Ohms]. 
The voltage across this resistance will be 24[V] maximim, so the [maxmimum] current will be
     24 [V] / 120 [V/A] = 200 [mA] "  

However,
* I've confirmed via direct measurement that the 18-bit DACs can only do +/- 10 [V] differentially NOT per leg. So the max possible voltage is
     DAC_MaxV = 10 [V] (differential output)
** The DC gain of the circuit is 
     CD_VoltageGain = (1+R3/R10) = 1.22 [Vin/Vout] 
(OK, 2% error, but just wanted to make sure we understood from where Ron's numbers came)
And just in case, to remove all suspicion:
From the QUAD Top Driver board schematic, D0902747:
-      Rout = (R1+R5)*(R90+R91)/(R1+R5+R90+R91) 
          = (22+22)*(220+220) / (22+22+220+220) [Ohms]
          = 40 [Ohms],
so that's correct, and Stuart just measured the BOSEMs to have a resistance of 
-      Rcoil = 42.7 [Ohms] , 
so that's correct as well.

So, the maximum output current of the circuit is actually

     DAC_MaxV * CD_VoltageGain / (2*Rout+Rcoil) = 10 [V] * 1.22 [V/V] / (40+40+42.7) [V/A] = 0.09943 [A] = 99 [mA]

which if all other numbers from T1100595 are correct, then this would produce a maximum displacement of

Pitch: 560 micro rad
Yaw: 580 micro rad


Current Monitors
The current monitors have a calibration of 

Amps across the BOSEM coil = ADC [V/ct] * Fast_I Mon Circuit Gain [V/V] / BOSEM Coil [V/A]
                           = 40/2^16 [V/ct] * 3/2 [(single ended Vout) / (differential Vin)] * / 42.7 [V/A]
                           = 2.1441e-05 [A/ct]

The current monitors for the primary Pitch OSEM (F1) on the ITM, with a 6400 [ct] torque offset from the sliders, show -2736 [ct] of current. (I use F1 and not either F2 or F3, because F2 and F3 also contain the Yaw offset). That means the current across the coil is

Icoil = 2736 [ct] * 2.1441e-05 [A/ct] = 0.059 [A] = 60 [mA] 

which is indeed about half the range of the coil driver, which jives with both the [corrected] calculation of 250 urads and the observation that Rana saw ~50000 cts (or half the range of the 2^17 ct DAC max).



Note that the original design intent was to have ~1 mrad of range from the TOP stage, so if we want to restore that intent, we should reduce the output resistance of each leg by a factor of 4, such that the range is

DAC_Max * CD_VoltageGain / (2*Rout+Rcoil) = 10 [V] * 1.22 [V/V] / (10+10+42.7) [V/A] = 0.19458 [A] = 194 [mA]

which could be done by changing the values of R1, R5, R90, and R91 to 10 Ohm resistors.

Angle calibration of TMS OSEM:

When tilting TMS without tilting the ALS beam on the table, the beam leaving the TMS telescope would tilt by almost the same amount (19/20 or 21/20) as the TMS itself. Here I just ignore 5% error and assume that the beam tilts as much as the TMS.

Using the baffle diode (https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?.submit=Number&docid=d0901376) we can calibrate the TMS OSEM. Note that the PD locations are not the same for H1 and H2. We're looking at H2 ITMY (left hole on page 3 of the above document).

There are three PDs horizontally aligned. The top one (PD3) is about 6.25 in away from the middle (PD2). The bottom one (PD4) is 11in lower than the middle. We know (from experience) that increasing P offset moves the beam down. And there's a fourth diode (PD1) that is at the same height as the middle one and horizontally off to the left by 11 in. PD1-PD4 naming convention is explained in E1100867, page 15.

For PIT, PD3-PD2 is about 6.25 in for 21000 counts, so it's 6.25*25.4e-3/21000/4000 = 1.9 nrad/count.

Also for PIT, PD2-PD4 is about 11 in for 38000 counts, 11*25.4e-3/38000/4000 = 1.8 nrad/cout.

For YAW, PD1-PD2 is about 11 inches  for 16800 counts, so 11*25.4e-3/16800/400 = 4.2 nrad/count.

There's no funny thing in the output matrix, PIT to coil matrix elements are just +-1, same for YAW, so you can multiply 131072 to get the range.

We can also get the initial alignment number using the offsets as of now (-42800 for PIT and +59200 for YAW)

Note that the order of the channel numbers (27, 28, 29, 30) is reversed. Right now PD1, 2, 3 and 4 = Chan30, 29, 28 and 17.

The M3 stage watchdog was observed to be perpetually tripping and could not be reset. This is due to watchdogs being triggered for the OPELV_RMS and OPLEV_SUM, which are not visible/settable in the medm screens. 

To rectify this I have manually set the following:- 
caput X1:SUS-HXTS_M3_WD_OPLEV_RMS_MAX 5
caput X1:SUS-HXTS_M3_WD_OPLEV_SUM_MIN -10

For now, this prevents the watchdog from tripping. 

These results look excellent. 

The only thing that concerns me (where the level of concern (from 1 = "it's awesome. no worries" to 10 = "OMG take it apart and rebuild it") is a 5.5) is the cross-coupling I see in the individual comparison with the model, i.e. in
2012-06-21_1700_X1SUSPR2_M1_ALL_TFs.pdf.
In there, I see cross-coupling between degrees of freedom which we don't normally expect to be there:

1st Yaw Mode (@ 1.09 Hz) into T and L
2nd Yaw Mode (@ 2.04 Hz) into T and L
2nd Roll/Pitch Mode (@ 1.51 Hz) into Y
2nd Vert or 3rd Long Mode (@ 2.80 Hz) into Y

I'm not terribly concerned, because -- as usual -- the cross coupling is reduced to barely visible with damping loops ON. But, it's something to watch out for with this guy as he progresses through the testing (i.e. we'll look with more scrutiny after the optic is swapped). To refresh one's memory -- the reason why we care:  
(1) When the model doesn't match measurements, we can't trust the model to accurately predict other transfer functions which we can't normally measure
(2) If the transfer functions (which are representative of the "plant" upon which we design control loops) are *different* between suspensions by some (as-yet-to-be-quantified) significant amount, then it will make copying and pasting control systems more difficult and time consuming to design.
I think with this suspension, and all others, we're doing fine in both these departments -- but again, we won't really know until we start locking some cavities and really try to push the SUS's to their limit.