ISCT6 realignment, power measurement, shutter test

[Evan, Alexa, Koji]

We worked on the ISCT6 yesterday after noon before the vent recovery.

- AS_AIR and OMCR paths were realigned

- AS_AIR path attenuations (ND filter, BS) were removed.

- Power at various points on the table were measured.

- OMC PZT shutter and HAM6 fast shutter were tested. Their shutter speeds are 4usec and 2msec, and fast enough for higher power operation.

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Optical path alignment

- The alignment of the beams in the AS_AIR and OMCR paths were revisited.

- The OMCR path had the SRC length setup which had undamped reflections.
  A beam dump formed by two ND filters (OD1.0) and knife-edge dump were inserted in the path.

- Two power-attenuation elements in the AS_AIR path were removed.
  A 50:50 BS common for AS_AIR_A (1f) and AS_AIR_B (2f) were replaced with an HR mirror.
  The other was OD1.0 ND filter fro AS_AIR_A.

Power measurement

The naming of the optics is based on D1201210-v7.
AS-BS2 = 50:50 BS common for the PDs
AS-BS3 = 50:50 BS for the PDs

Before AS-BS2 replacement (but no ND filter for AS_AIR_A)

After the periscope/before the 1st steering mirror: 8.05 uW (@Apr 10 4:52PM local)
After the periscope/after the 1st steering mirror:  8.04 uW
AS-BS2 incident:   4.20uW
AS-BS2 refl:       2.53uW (R(AS_BS2)=60.2%)
AS-BS3 trans:      1.51uW (T(AS_BS3)=59.7%)
AS_AIR_B incident: 0.79uW (R(AS_BS3)=31.2%)
AS_AIR_A incident: 1.31uW (No ND filter)

ND filter (tested at OMCR)

ND incident 1.90 mW
ND trans    0.180mW (T(ND) = 9.5%)

After AS-BS2 replacement

AS-BS2(HR) incident: 4.15uW
AS-BS2(HR) refl:     4.08uW (R(AS-BS2) = 98.3%)
ASAIR_B incident     1.45uW (R(AS-BS3) = 35.5%)
ASAIR_A incident     2.44uW (T(AS-BS3) = 59.8%)
 

Previous
AS_AIR Periscope -> AIR_B thruput:  9.8%
AS_AIR Periscope -> AIR_A thruput:  1.6%

New
AS_AIR Periscope -> AIR_B thruput:  18.0%
AS_AIR Periscope -> AIR_A thruput:  30.3%

=> We decreased the OM1 transmission from 5% to 800ppm = 1/63
     This was compensated by the inclease of the PD incident by
     x1.8 for AS_AIR_B => x35 gain missing
     x19 for AS_AIR_A => x3.3 gain missing

OMCR after the periscope (OMC unlocked): 1.95mW

Shutter test

We performed an end-to-end test of the fast shutter and the OMC PZT shutter.

- Procedure (See also LHO ALOG 16355)

Fast Shutter test:

1) Confirm the shutter threshold level. It was 2V.

2) Thorlabs PDA255 (50MHz) was set on the ICST6 table. The OMCR beam was aligned. Confirmed the OMC was unlocked.

3) Disconnect the analog signal to the trigger logic module, and plug it on a function generator.
    QPD Transimpedance Amp for AS_C (Rack ISC-R5 U18) has QPD SUM1 output at the back side.
    This cable is connected to the trigger logic module on the top of the ISCT6 enclosure.

4) Set the function generator to produce the triangular signal with an offset of 0.7V and the amplitude of 2V. The frequency was 100Hz.
    => The signal ramps from -1.3V to 2.7V.

5) First, the amplitude of the FG was set to be 0. Open the shutter if it is closed.

6) Set an oscilloscope to watch AS_C Sum, Thorlabs PD, and trigger signals. Set the scope to "Single Sequence" mode with "Normal" trigger.

7) Set the amplitude is to be 2V. This already triggers the shutter. Return the amplitude to 0V.

OMC PZT Shutter test:

1) Lock the OMC. Place the PD at the OMC trans (leak) beam.

2) Otherwise the same setup as above.

- Result

- The trigger occured at 2V and almost immediate.
- The fast shutter was closed with the shutter time of 2.3ms between the trigger and the complete close.
- The OMC shutter was closed with the shutter time of 3.9us between the trigger and the complete close.

- Analysis: Are the diodes safe now?

This threshold level shuts off the shutters when the incident power to HAM6 is 1.2W (cf. Dan's LHO ALOG 17787)

According to the lock loss observation at LLO, the AS port power during lock loss is not impulsive but rather slow.

1.2W x 4us = 4.8 uJ
We deliver half of this power on the OMC DCPD. => 4.8/2 = 2.4uJ

This is x400 smaller than the minimum pulse energy level (1mJ) tested in Frank's diode blasting experiment,
which did not show any (or significant) damage of the diode.

Therefore we can conclude that the OMC DCPDs are safe.

OMCR QPDs and OMC QPDs receive 1/20 and 1/250 attenuated pulse with 600 times longer time.
So the below calculation is for the OMCR QPDs.

1.2W x 2.3ms / 20 = 0.14 mJ

This is still x7 smaller than the above 1mJ.
Therefore the OMCR/OMC QPDs are also safe even the beam is on a single element by chance.

CDS model and DAQ restart report, Thursday 2nd - Friday 10th April 2015

report attached.

Starting vent recovery

Alexa, Evan, Sheila, Koji

Koji, Evan and Alexa tested both the OMC PZT shutter and the fast shutter, realinged ISCT6, removed the ND filter from AS AIR and installed ND filters as beam dumps in the OMC refl path.  More details about that are coming in a latter alog.  

After Dave helped us get the h1boot back, we got a late start on trying to recover locking.  We got through the inital alingment procedure, evan set the whitening gain so that the signals out of AS AIR should be roughly similar to what they were before the change of OM1 and removal of the ND filter (he changed it from 42 dB to 15dB).  Some gains still had to be readjusted X arm IR locking gain was changed from 0.04 to 0.12, MICH dark locked gain was changed from -2000 to -1000.

We ran into a few problems along the way, the PSL noise eater was oscillating (and has been for a few days).  After togling the switch the ISS would not lock, we reset the reference level to get it locking again.  We also found a variety of settings which seem to have been wrong, the COMM PLL input was disabled, the DARM input was off, the SRM top stage length was on.  

We have been able to lock ALS COMM, but DIFF is not working.  We can engage it with a low gain, see that the PLL is kept in range, but we cannot turn the gain up. This is behavior similar to what happens when the ESD is not working, but we tried exicting the ESD in angle and watching the OpLev, we can see that it does respond.  

Also, the ETMY ESD has been tripping many times tonight, even though we have not tried to actuate on ETMY at all. 

As Kyle requested, we disabled the HV in HAM6. For the OMC PZT, we disabled the output of the 100 V Kepco supply. For the shutter, we flipped the HV enable/disable switch on the driver chassis next to HAM6.

For Jeff, we are leaving both arms locked in green with neither ALS COMM or DIFF locked.  The wind is not as high as it was forecast to be tonight.  

TCS X CO2 laser

After the h1boot restart finally got a chance to measure the power output of the X CO2 laser versus the rotation stage angle. The minimum power angle was measured at 38° (a change of 1° from previously). The maximum power output was reduced to 5.01W from 5.44W, measured before the periscope. The configuration was modified to reflect these new measurements. 

The X-arm CO2 laser is now unblocked and running stable. 

Initial Attempt at Characterizing Noise of Beckhoff ADCs

J. Kissel, P. Thomas, D. Sigg

Patrick grabbed ten seconds of data from the following Beckhoff ADCs with three different input signals: +/- terminals shorted, +/- terminals connected to a 9 [V] battery, and +/- terminals fed with a 1 [Vrms] amplitude, 10 [Hz] sine wave. 
EL 3004, billed as a 12-bit ADC, "presented as 16-bits" datasheet.
EL 3104, billed as a 16-bit ADC datasheet.
EL 3602, billed as a 24-bit ADC datasheet.

The messages:
- Datasheets are deceiving and misleading. So are the default settings. So is what it means to be a 12-bit or 24-bit ADC, since there's no guarantee that all bits are significant.
- The calibration for these ADCs, regardless of what the ADCs are billed as, is 20 / 2^16 [Vpp / ct] for EL3004 and EL3104, and is 20 / 2^32 [Vpp / ct]
- The noise performance of the EL 3104 16-bit ADC makes the most sense, and is a consistent 30 [uV/rtHz] regardless of input.
- The noise performance of the EL 3004 12-bit ADC is confusing, but makes sense if you consider it to be a 12 bit internal ADC chip running at 50 [Hz] whose [least significant / "last"] bit is not random, sampled by the internal processor at 1 [ms] padded to produce 16 bits. If we treat the injected sine wave's noise performance as the expected noise, 200 [uV/rtHz].
- The noise performance of the EL 3602 24-bit ADC (two channels of which were measured) is non-sense. Further investigation is required.
- The noise performance of the EL 3104 looks like it would be just about good enough to handle the pressure sensor signals as they stand in the HEPI Pump Servo (recall LHO aLOG 16500).
- We should consider looking into some Beckhoff PID modules as well, such that the computation and control is all done inside the Beckhoff system, and EPICs is merely used as a monitor.

We're (as in Patrick) going to get a longer data on Monday set so we can better assess the low-frequency performance, and we'll focus on why the time series of the EL 3602 seems to be pre-averaging the data, causing a huge increase in noise when an AC signal is driven through it.

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Data, plots, and analysis script live in
/ligo/svncommon/SeiSVN/seismic/Common/Documents/T1500159_BeckhoffADCNoise/

h1boot server crashed 07:05 UTC

J. Kissel, A. Staley, D. Sigg, S. Dwyer, E. Hall, K. Arai, G. Grabeel [remote D. Barker]

The stuff that only happens on a Friday evening.

At 07:05 PDT, the h1boot server crashed. We'd discovered this because all EPICs information from the front-ends (StripTools, MEDM screens, etc) had suddenly flat-lined. After a few calls to Dave, he'd suggested resetting the h1boot computer in the computer Mass Storage Room (MSR, the noisy computer room right adjacent to the control room, where all the front ends live). Unfortunately, because the file system had not been checked in 381 days, it had to go through 2 excruciatingly long system checks on its way back up. An hour later, the initialization completed, and all work-station displays of data instantly came back. 

No apparent hiccups in any front end processes, and they picked up right where they left off. Some work stations had to be rebooted, but others continued on without issue. We continue on to restoring the IFO post HAM6-vent!  

In the mean time, we were able to squeeze in some valuable offline commissioning time (see attached).

79.2 MHz fixed frequency source powered off

Daniel, Sheila

I powered off the 79.2 MHz fixed frequency source in the CER ISC C4 rack.  There were two long cables connected to this, one of which was in patch panel 1, signal 2 (see page 10 of the RF distribution plan). This cable was not in the plan, but had a handwritted masking tape label that said ALS COMM VCO.  It went to the long cable that should have been labeled 10-2 (the label seems to have fallen off).  This went to the field rack R4, where it was similarly labeled and had a cable attached that was just dangling in the rack.  This cable has been removed, and the long cable is terminated at both ends.  the cable which is in the RF distribution plan is still in place and terminated in R2.  

This should mean that there is one less frequency to cause the type of wandering lines seen in alog 17506.  

We think that we have now made some efforts that should mitigate the three types of glitches that have been pointed out so far.  

2^16 crossing DAC glitches alog 17654 reducing the range needed for ETMY and turning off the linearization alog 17713

tidal nitting software limiter: 17555 saturations in tidal should be less common now that we have re done the way that we engage the tidal while locking ALS 17624.  Dan also has written a tool that could be used to alert us when something is close to its software limit, 17791.  We could also think of adding only a few of these filter banks to the sys diag guardian.  

Beam Tube Washing

Scott L. Ed P. Chris S.

This report will include the following dates, 4/8-4/10/15.

Wednesday the crew was able to clean 75 meters of tube between X-1-8 double doors and 1st single door north to mid station. Safety meeting @ 3 P. M. Still a good day.

Thursday the lights and equipment were relocated to last single door to mid station. Vacuumed tube supports and sprayed bleach/water solution on soiled floor areas. Cleaned 12 meters of tube.

Today the crew was able to clean 70 meters from last single door north to mid station. 

Testing results are posted here.

Opened GV5 and GV7

Kyle, Gerardo

!ATTENTION * COMMISSIONERS * ATTENTION!

LVEA COMMISSIONING ACTIVITIES ALLOWED ONLY UNDER THE FOLLOWING CONDITIONS (until further notice): 

1. Vacuum equipment pump carts, AC cords and connecting "flex lines" in vicinity if HAM6 not be touched or disturbed in any way 

2. High Voltage systems in HAM6 (picomotors, PZT, Shutter) only be enabled/energized if someone is present to monitor HAM6 pressure trend (use StripTool to display PT 110B).  If trend changes, i.e. starts to increase instead of decrease, disable/de-energize HAM6 picomotor, PZT and Shutter and notify Kyle @ 509.308.0755, Gerardo @ 509.438.0828 or John @ 509.438.0823

Ops Summary

08:52 Hugh to HAM6 to unlock HEPI
08:53 Richard pushing reset button on h1nds1
09:01 Filiberto near BSC1, 2, 3 measuring lengths for new CPS cables
09:07 Gerardo to LVEA to start preparation for leak checking HAM6
09:24 Kyle leak checking HAM6
09:41 Hugh done
      Hugh running linearity test on HAM6 HEPI
10:36 Sudarshan and Travis to end X to work on PCAL calibration
11:24 Gerardo, Corey and Keita to HAM2 to install beam dump
11:28 Robert to end X and end Y to measure IO chassis
12:03 Gerardo done helping Corey and Keita, Peter K. transitioning the LVEA to laser hazard
12:15 LVEA transitioned to laser HAZARD
12:28 Kyle switching HAM6 to ion pump
12:39 Travis and Sudarshan back
      Corey and Keita back to HAM2
12:56 Greg G. turning on TCS X laser
13:36 Dick G. to squeezer bay looking for optic
14:35 Kyle and Gerardo roping off area around HAM6 to protect turbo pump
15:09 Corey and Keita done, Kyle starting work to open GVs

Testing new IO Chassis DC power supply on x1iscex

Richard, Filiburto, Robert, Jim, Dave:

we have installed the test DC power supply in the x1iscex IO Chassis. Here are the current draw numbers on the +24V power supply for this unit

IO Chassis On, computer Off	2.5A
IO Chassis On, computer On	3.5A

(The IO Chassis contains: 4 ADC, 1 16bit-DAC, 1 18bit-DAC)

Porcupine beam dump installed (Corey, Gerardo, Bubba, Evan, Sheila, Betsy, Patrick, Keita)

This us a follow up of https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=17788.

What was done:

1. A round piece of Lexan was cut out by Bubba. It is dropped in over the viewport such that it securely sits on top of the viewport flange without touching the viewport.
2. The old lexan cover was removed and the new one was dropped in.
3. The old lexan protector assy was removed.
4. The new beam dump optical table assy was installed.
5. LVEA was transitioned to the laser hazard, MC was locked at 2.2W, PRM was misaligned.
6. The beam was not found, so PRM was scanned until we have a reasonable beam. At this point, we were only getting 1W out.
7. Alignment of the PRM was further adjusted until we get 1.6W or so through the lexan. Steering mirror was aligned to send the beam to SiC plate.
8. Lexan plate was removed, the beam dump alignment was still good, and we were getting 1.8W out of 2.2W we sent in. The beam goes through MC and then Faraday twice, and this is a reasonable number. According to Paul, MC (one way) and FI (one way) combined efficiency is about 85%. Assuming that FI is 90% one way, in our case it's a total of 0.85*.9=0.77. And 2.2W*0.77=1.7W.
9. The lid of the assy was put on.
10. Though unrelated to the beam dump, Gerardo found that the accelerometer on HAM2 was knocked/moved from its intended position. It was already like that when we climbed up on HAM2 yesterday.

Corey took a bunch of pictures, which he will post on resource space.

WHAM6 ISI Target Positions Adjusted--PitchRoll of Table causes Isolation Difficulty

When attempting to Isolate the ISI, the CPS would trip (now that I think about it, this is weird, I would think it would have been the Actuators,) as the horizontal loops were turning on.  During this time, the ISI has just restored the locations for the Vertical DOFs.  Jim reminds me that the stuff added to the HAM6 Optical Table tilted the vertical CPSs nearly out of spec.

We reset the CPS Targets to the Free Hanging Positions so the ISI wasn't driving anywhere.  It worked first time there.

Our theory is that when the vertical loops are closed and the old Targets are loaded for servoing, the horizontal GS13s are tilted sending a large signal into the CPS via the Damping loops and possibly the just starting horizontal isolation loops.

Resetting the CPS Targets Locations shifted the Pitch of the ISI ~70000nrads.  Dan & Koji say this is nothing to worry about.  I'll leave the SDF diffs alone for now as an easy reference to change the alignment.  If you want to return to the previous alignment, just type the Burt Target value into the Requested Setpoint Field (e.g. H1:ISI-HAM6_CPS_X_SETPOINT_NOW) on the CART_BIAS medm.  Increasing the Ramp Time to something more than the current 5 seconds might be prudent.

I've attached an image that may help.

SUS SDF update effort continued

More work today on SUS SDF weeding.  What I changed:

 

OM1, OM2, OM3 - Y DAMP gain and OSEMINF gains/offsets updated in safe.snap due to recent tuning. (For Dan, fixed OM2 M1 UL gain which Dan set to 0.136 in error when it should have been 1.363.)

SDF ignore PR M1/M3 LOCK and TEST switches that are now under GRD control.

Finished setting SDF to ignore PR & SR M3 BIO state and associated M3 coil SW1S now under GRD control.

SDF ignore TMS LOCK and TEST switches that are now under GRD control.

~1230 hrs. local -> Valved-in HAM6 ion pump

HAM6 being pumped by both turbo and ion pump for now

Ion pump controller "protect" feature shut down after 15 minutes -> Can't handle relative high pressure (3000V @ 0.05A 150W unit) -> Valved-out ion pump from HAM6 -> Restarted ion pump -> OK now