Nutsinee, Dan, Jeff K, Angus

This is a follow up on the alog17529. Below you'll find the list of violin mode frequencies we found and averaged frequencies including possible alternatives. The fiber is determined using data gathered in alog16614 (which cites alog11184, alog9359, alog11044, and alog6858). The air frequency included in the last column. 

The way alternatives work is that, if you choose to use one, you have to use the next alternative as well. For instant, if you decide for 508.00075 line to be averaged violin mode for the ETMY FR, you have to use 508.176 as the ETMY FL line. Or if you were to pick 508.21725 as the ETMY FL, you have to use 508.213 as the ETMY BL. This seems a little bit confusing so I attached the original Excel file as well. 

Any comments, questions, and suggestions welcome.

Ps. I don't know why alog keeps making new entries everytime I add things to the table and update the file. Sorry for the spam!

Jim, Krishna,

After the troubles described in alog 17386, BRS was turned off to allow it to damp down naturally. This morning Jim and I restarted the BRS as attempted earlier in 17309. This time, the amplitude of the balance was low enough and we simply had to reposition the damper and start the software. Everything worked as designed. The attached plot shows the damping of the beam-balance.

After things had settled down I checked the spectra of the signals coming out of BRS and the tilt-subtracted super-sensor and everything looks normal. Wind speeds were at 0-10 mph and the subtraction looked good as seen in the attached pdf. The first plot shows the ground T240 X motion, the BRS_RY ( * w^2/g), ST1 T240 X and the super-sensor. The next plot shows coherences between these sensors.

model restarts logged for Sat 28/Mar/2015
2015_03_28 18:46 h1fw0

one unexpected restart.

model restarts logged for Sun 29/Mar/2015

no restarts reported

model restarts logged for Mon 30/Mar/2015
2015_03_30 15:43 h1fw0
2015_03_30 19:47 h1fw0
2015_03_30 22:28 h1fw1

three unexpected restarts

model restarts logged for Tue 31/Mar/2015
2015_03_31 10:04 h1iopsusex
2015_03_31 10:11 h1iopsusex
2015_03_31 10:14 h1iopsusex
2015_03_31 10:18 h1susetmx
2015_03_31 10:18 h1sustmsx
2015_03_31 10:37 h1iopsusex
2015_03_31 10:37 h1susetmx
2015_03_31 10:37 h1sustmsx
2015_03_31 10:42 h1iopsusey
2015_03_31 10:46 h1susetmy
2015_03_31 10:46 h1sustmsy
2015_03_31 11:07 h1calcs
2015_03_31 11:12 h1iopsusauxex
2015_03_31 11:12 h1susauxex
2015_03_31 11:16 h1iopsusauxex
2015_03_31 11:17 h1susauxex
2015_03_31 11:19 h1iopsusex
2015_03_31 11:20 h1iopsusex
2015_03_31 11:21 h1susetmx
2015_03_31 11:21 h1sustmsx
2015_03_31 11:43 h1iopsusauxey
2015_03_31 11:43 h1susauxey
2015_03_31 11:47 h1iopsusey
2015_03_31 11:47 h1susetmy
2015_03_31 11:47 h1sustmsy
2015_03_31 11:48 h1susetmy
2015_03_31 11:54 h1iopsusb123
2015_03_31 11:57 h1pemcs
2015_03_31 11:57 h1susitmy
2015_03_31 11:59 h1pemex
2015_03_31 11:59 h1pemey
2015_03_31 11:59 h1susbs
2015_03_31 11:59 h1susitmx
2015_03_31 12:24 h1broadcast0
2015_03_31 12:24 h1dc0
2015_03_31 12:24 h1fw0
2015_03_31 12:24 h1fw1
2015_03_31 12:24 h1nds0
2015_03_31 12:24 h1nds1
2015_03_31 12:26 h1pemex
2015_03_31 12:26 h1pemey
2015_03_31 21:43 h1nds1

one unexpected restart. Maintenance day, SUS, CAL and PEM model changes with associated DAQ restart.

model restarts logged for Wed 01/Apr/2015
2015_04_01 06:43 h1fw0
2015_04_01 09:11 h1susitmx
2015_04_01 09:16 h1susitmy
2015_04_01 09:29 h1broadcast0
2015_04_01 09:29 h1dc0
2015_04_01 09:29 h1fw0
2015_04_01 09:29 h1fw1
2015_04_01 09:29 h1nds0
2015_04_01 09:29 h1nds1
2015_04_01 12:07 h1broadcast0
2015_04_01 22:43 h1fw0

two unexpected restarts. Continuation of SUS work with associated DAQ restart. DMT reconfiguration of DAQ broadcaster.

Attached are the Phase 3b damped and undamped TFs of SR2 taken over the last few months.

Note, there is only the damped M2 stage TF due to the fact that there is a broken coil o magne at that stage and I was leary of driving too hard or too much.

Attached are the Phase 3b damped and undamped TFs of SRM taken over the last few months.

I looked into the coherence of DARM with all channels, using 10 minutes of data from 2015-04-02 11.00.00 UTC, which seems a period of high and stable range from the detchar summary page. Here is the result:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1112007616/

And as usual, my digest. In very brief summary, nothing really new above 10 Hz, OMC noise below 10 Hz.

• Low frequency noise (below 10 Hz) shows significant coherence with OMC suspension and alignment signals, for example SUS-OMC_M1_NOISEMON_T3, SUS-OM3_M1_LOCK_P_IN1, SUS-OM2_M1_LOCK_P_IN1 etc (see first plot)
• In the 10 to 100 Hz region there is quite some coherence with ITMY longitudinal control signals. Is this due to some subtraction scheme? Even if that's the case, a good subtraction should make DARM incoherent with anything else (see second plot). The same level of coherence is visible with MICH signal (third plot), so my guess is that this is indeed the residual coupling of MICH noise.
• In the 10 to 40 Hz region there is some coherence with BS yaw control (4th plot)
• Coherence with SRCL and PRCL is quite high too in the 20 to 80 Hz region (5th plot).
• The 56.75 Hz line is coherent with ETMY ISI signals, for example ISI-ETMY_ST2_BLND_RZ_GS13_CUR_IN1. Same at 170.5 Hz, 398 Hz, 534.75 Hz
• At 100 Hz there is some coherence with EX magnetometers
• Usual coherence with IMC and PSL periscope signals at the peaks between 180 and 400 Hz
• The band between 414 and 420 Hz is highly coherent with PRCL, same for 971-973 Hz
• At 750 Hz there is high coherence with intensity noise. Same (but slightly lower coherence) at 1980 Hz
• At high frequency intensity noise is still a safe factor below the measured DARM noise
• There is large coherence at 1009.75 Hz with LVEA magnetometer signals: PEM-CS_MAG_LVEA_OUTPUTOPTICS_QUAD_SUM
• In the band 1186-1195 there is coherence with SRCL/PRCL but most interesting with MCL and REFLSERVO signals (plot 6)
• At high frequency there is still the usual broadband low coherence with PRCL and SRCL signals, projecting about a factor ~3 below the DARM noise floor.

v1.0   2015April 02

Plan for HAM6 Vent, April 2-8, 2015

Approved work to be done:

1. OM1 mirror replacement.
2. Install a 90:10 BS in OMCR.
3. Lubricate beam diverter with Krytox LVP  (verbal approval by D. Coyne, 4/1/2015, for limited use)
4. QPD cables strain relief.
5. Measure HAM6 power budget.

DCC Vent Documents referenced in this plan:

• E1201035-v17, "aLIGO Chamber Entry & Exit Procedures"  https://dcc.ligo.org/LIGO-E1201035
• M1100039, "Hanford Checklist - HAM Door Removal"  https://dcc.ligo.org/LIGO-M1100039
• M1300464-v4, "Procedure for preparing aLIGO IFO for pumpdown"  https://dcc.ligo.org/LIGO-M1300464

Additional Documentation:

• The ECR approving the use of Krytox LVP is E1400353.
• The Beam Diverter assmbly is described in E1100686-v3 .

The HAM6 door to be removed is the "East" door.

Schedule

Thursday, April 2, 2015

1. 1st cleaning of HAM6 area [technical cleaning crew]
2. Move Clean Room (CR) into position for HAM6, turn on fans, and verify fans are working [Bubba, Gerardo]
3. Set up dust monitor and verify it is working. [Jeff B.]

Monday, April 6, 2015

1. 2nd cleaning of HAM6 [technical cleaning crew]
2. Verify and confirm CR (clean room) supplies are in place (gowns, change room, ...). [Jeff B. or Betsy]
3. Verify safe.snap files. [CDS: Dave Barker]
4. Review and follow E1201035-v17, "aLIGO Chamber Entry & Exit Procedures" checklist as annotated by Calum and Dennis for abbreviated entry. https://dcc.ligo.org/LIGO-E1201035
5. Review and follow M1100039, "Hanford Checklist - HAM Door Removal" https://dcc.ligo.org/LIGO-M1100039 . [Betsy is keeper of the list]

Tuesday, April 7, 2015

1. Vacuum crew: Follow M1300464-v4, "Procedure for preparing aLIGO IFO for pumpdown". https://dcc.ligo.org/LIGO-M1300464 . Note on Fast Shutter: De-energize HAM6 Fast Shutter High Voltage (HV) and Low Voltage (LV) as per the following steps:
   1.  Set HV switch on fron of panel on D1400078 to “disable”.
      
   2.  Shut off Kepco power supply (LV Power Supply Room) serving fast shutter.
      
   3.  Back at D1400078 set rocker switch to off position on back of D1400078.
2. CDS controls crew check: The controls system needs to be up and running during the HAM6 work, so make sure that normal Tuesday maintenance activity on CDS doesn't interfere with the vent activities.
3. Verify Purge Air on.
4. Wipe down of door. [Technical Cleaners]
5. Lock HEPI, apply HEPI dust covers
6. Transition to "Laser Safe" (IR, TSC 10um); End Station green lasers to remain on as closed gate valves block beams into LVEA [clarify with P. King]
7. Close Gate Valves to Arm Cavities
8. Start vent on HAM6, estimate 1-2 hours duration. [Kyle or Bubba]
9. Dust Monitors - verify operation and take readings for before and after entry. [Jeff B.]
10. Remove door, following M1100039
11. In-chamber work (ISI lockers access through East door ) [Koji A. is team captain]:

In-chamber Work Plan:

Preparation

- Open East door of HAM6
- ISI locking
- Align the beam on the AS_C QPD
- Align the beam on the OMC QPDs
- Confirm the beam is on the WFS QPDs

OM1 mirror replacement

- OM1 mirror replacement

New optic
Usual CLASS B Allen wrenches
First contact removal kit: UHV N2 & ionizing blow kit
If removal of the optics does not work:
=> CG: Tip Tilt Spare
S/N 28 is in a bag on the bottom shelf of rack in the Optics Lab, if needed.

- Align the spots on OMC QPDs/WFS QPDs with OM1 and OM2
- Check if the BOSEM values are OK or not.

If not, we need to retune the BOSEM positions (debiasing)
A hex box wrench for BOSEM adjustment

- Check or align the AS_AIR path
- Align AS_C QPD

At LLO, pitching up of the OM1 suspension was observed. This case, the balancing screws needs to be replaced. Therefore it’s better to prepare
CLASS A #8-32 set/cap screws/nuts

Inserting a 90:10 BS in OMCR

- Check if the small mirrors at the OMC REFL have no clipping
- Insert the 90:10 BS in the path.

The optic on the mount
CG: 2” Mount for new BS & post
We definitely do not have 2" Mirror Mounts. We have plenty of 2" lens holders. We have varying posts, so we should confirm what works with lens holder.
=> This is OK

As Lisa states, we have a bag of these (E1500009) in the Optics Lab. They still need to be cleaned.

ISC Dog Clamps:
There are bags of both type of ISC-specific dog clamps on the shelf in Optics Lab.

- Dump the reflection with the beam dump

The beam dump on the mount
CG: V-Holder Beam Dump Assembly
We have these parts in the Optics Lab.

- Align the OMC REFL AIR path to recover the alignment
- Align the OMC REFL QPDs

QPD cable strain relief

- Attach QPD cable strain relief to AS_C/OMCR_A/OMCR_B QPDs

3x D1101910
3x D1101911
3x SHCS 1/4-20 x1/2” non plated
6x SHCS 8-32 x 1/2” non plated
CG: I have both Peek parts & we also must have c&B-ed the hardware for them, because two bags of bolts were with the parts.
I have put all (4) bags in the H1 Spare QPD tote under the optics Table.

Lubrication of the beam diverter

- Apply Krytox on BD
Krytox: Permission received from Dennis Coyne, application tips from Matt H./Rich A. => Some information will be provided in a couple of days)

Counterweight for Beam Diverter

Need to see what type of screw can be used for the hole on the Beam Diverter and see what we have. We should be OK.

HAM6 Power Budget

- Measure optical power (OMC Unlocked) OM1 incident

OM1 transmission
OM1 BS incident
OM1 BS transmission vs AS_C sum OM1 BS reflection
AS_AIR (window transmission) OM2 incident
OM3 incident
OMC incident
OMC Reflection (Unlocked)
OMCR BS90/10 incident
OMCR BS90/10 reflection
OMCR BS90/10 transission
OMCR BS50/50 transission
OMCR BS50/50 reflection
OMCR QPDA incident (vs OMCR QPDA digital reading) OMCR QPDB incident (vs OMCR QPDB digital reading) OMCR AIR (window transmission)

- Lock OMC

(OMC incident)
OMC transmission (DCPDA/DCPDB analog/digital reading)
OMC REFL
OMC leakage trans?
For locking the OMC, we need to turn stop the purge air, and probably stop/lower the HEPA fans.

Exit procedure

- Take photos of the table => Send them to Eddie - Ground loop check
- ISI unlock

The following may take place on Wednesday.
- Hang door
- OM1 TF check
- Prepare for Door closing and Pumpdown

Wednesday, April 8, 2015

1. After completion of in-chamber work, obtain approval and signatures for volume closure, LHO (see E1400474-v1). [Vern]
2. Obtain sign off signatures for chamber closure.
3. Verify ISI unlocked.
4. Notify door crew to hang door.
5. Assess status of suspension, TF measurements. [Betsy or Jeff K.]
6. Verify readiness to pump down, follow M1300464-v4, "Procedure for preparing aLIGO IFO for pumpdown". Re-confirm that all high voltages are off.
7. Notify Vacuum crew of readiness to start pumps.
8. Restore HEPI
9. Return to Laser Hazard Condition
   

The transitions to and from "Laser Safe" need to be reviewed with Peter King.  The is the possibility of additional transition cycles during the in-chamber time period.  There may be independent cycling of the CO2 (10um) lasers. These need to be worked out in more detail.

The pump down is at the time and discretion of the Vacuum crew.

Reminder: File work permits for all door openings and closings. [Vacuum Crew]

For Reference:

ISC Prep Work (Corey's List)

Strain Relief Assy:
I have both Peek parts & we also must have c&B-ed the hardware for them, because two bags of bolts were with the parts.  I have put all (4) bags in the H1 Spare QPD tote under the optics Table.

Krytox
I have a tube of it in my desk (center drawer).  John was asking about waivers from Dennis for this (so we should look to see if those are around; perhaps in some Heintze documentation?).

Tip Tilt Spare
S/N 28 is in a bag on the bottom shelf of rack in the Optics Lab, if needed.

2" Mount for new BS & post
We definitely do not have 2" Mirror Mounts.  We have plenty of 2" lens holders.  We have varying posts, so we should confirm what works with lens holder.

V-Holder Beam Dump Assembly
We have these parts in the Optics Lab.
90% BS
As Lisa states, we have a bag of these (E1500009) in the Optics Lab.  One still needs to be cleaned for next week.

ISC Dog Clamps
There are bags of both type of ISC-specific dog clamps on the shelf in Optics Lab.

Counterweight for Beam Diverter
I need to see what type of screw can be used for the hole on the Beam Diverter and see what we have.  We should be OK.

OM1 Mirror
An OM1 mirror (E1100056) should be found and cleaned by Corey.

Ed, Jason

ISS Diffracted Power seems to be trending higher on the order of ~5%/day since the 28th. Yesterday, 4/1/15 I set it to ~ 7% at 17:45UTC.This morning it's up to ~ 12%. I've adjusted the power back down to 7% at a refsignal of (-)2.08. Funny thing is, it seems to have been doing just the opposite between the 23rd and the 27th. Between the 19th and the 23rd it did a bit if both.

Aidan et al.

A few bugs have cropped in the TCS system up since Acceptance. There are also some measurements that we should perform. The following is a list of these and the current status/plans to tackle them.

1. TCS-CO2-Y laser is outputting <50% of expected power. (see alog 17586). We suspect a problem with the RF laser driver. Bug 1036 has been added to Bugzilla.
2. The CO2 laser power cable connectors are too flimsy for the patch panel feedthroughs (given the weight of the cables). We are working on a more heavy-duty solution. Temporarily, the cables bypass connection at the patch panel and are connected on the inside of the enclosure (see alog 17586). 
3. Guardian needs further extensions for:
   1. ETM HWS automation: procedure for turning on the ETM HWS for measurements of thermal lensing is being worked out. Elli & Nutsinee are also going to tweak the longitudinal locations of the ETM HWS cameras next week (to ensure they're at the conjugate planes of the ETMs).
   2. RH diagnostics (will work with Jamie in the coming weeks)
   3. The delivered CO2 power needs to be matched to the requested power using a step in Guardian (working with Jamie next week)
   4. FLIR camera needs to be automated to measure the CO2 laser profile (no plans yet to tackle this).
4. There is currently no remote indication when the AOM warning lights become illuminated. Bug 1014 has been added to Bugzilla to address this. 
5. TCSY-CO2-X AOM needs to be moved to an independent power supply from the CO2 laser. This will be done next week during the vent.
6. Absorption measurements of the ETMs and ITMY need to be made (some time in the coming weeks/months).
7. Both ITM HWS are out of alignment following adjustments to the SRC alignment over the last two months. We need to realign these. There are QPDs on the HWS that sense the location of the ALS green beam. These should be used in future, in conjunction with the picomotors on the periscope, to remotely adjust the HWS alignment - but first a sensing matrix will need to be established.

Koji, Sheila, Dan, Evan

Summary

Noise coupling measurements for MICH, SRCL, PRCL, intensity, and frequency have been taken.

We also tried a few small noise-hunting activities.

Details

Coupling measurements

For PRCL, MICH, and SRCL, we excited each dof with a swept sine and then recorded the transfer function from the error signal (IN1) to the DARM channel. MICH was already done previously.

For intensity, we did the same as described earlier.

For frequency, we used the same DAC channel (LSC-EXTRA_AO_2) to drive the common-mode board excitation point with a few millivolts of swept sine. Then we recorded the transfer function from REFL_A_9I (which is out of loop) to the DARM channel.

The dtt files are attached. More analysis to follow.

Other

Koji and I saw that ASC-MICH_P had significant cohrence with the DARM spectrum between 20 and 40 Hz. We took an OLTF and found that the UGF was 2 Hz with 60° of phase. We installed an elliptic LPF at 20 Hz, which removed most of this coherence (see attached). Correspondingly, the DARM spectrum dropped by a factor of 1.5 or so around 30 Hz.

We then tried to tune the bias of the EX ESD to see if we could improve the DARM spectrum. We could not find a sharp optimum; rather, anything from −190 V to 0 V seemed to be OK.

Koji then suggested trying to excite a scattering shelf in DARM by driving the OMC suspension. We drove the suspension longitudinally, transversely, and then vertically by a few microns at 0.15 Hz, but we found we could not make anything appear in the DARM spectrum.

Twice today the high voltage for the OMC PZT tripped, requriring the power supply to be reset by hand. The voltage is set at 100 V and the current limit is 2 mA. The quiescent draw is 0.8 mA.

Here are results from an SR785 spectrum of the output of the DCPD whitening field amp for OMC DCPD 1. I have included the ASD plot as a PDF and listed the major frequencies below. Below Nyquist the frequencies are consistent with H1:IOP-LSC0_MADC0_TP_CH12, so I have used these instead of the frequencies derived from the SR785 data. The amplitudes are from the SR785 data throughout. Those amplitudes differ from H1:IOP-LSC0_MADC0_TP_CH12 as they are measured before the whitening filter / antiwhitening DSP.

Index. Frequency (Hz) ; Amplitude (uVrms/rtHz)
1. 8160 Hz ; 595 uV
2. 9880 Hz ; 177 uV
3. 10426 Hz ; 206 uV
4. 13000 Hz ; 135 uV
5. 13857 Hz ; 145 uV  (wideband cluster in H1:IOP-LSC0_MADC0_TP_CH12 - looks narrower in SR785 data)
6. 15072 Hz, 15218Hz ; 136uV (double narrow peak in H1:IOP-LSC0_MADC0_TP_CH1 - unresolved in SR785 data)
7. 19554 Hz ; 52 uV
8. 21128 Hz ; 23 uV
9. 23109 Hz ; 22 uV
10. 25000 Hz ; 21 uV
11. 26607 Hz ; 19 uV
12. 29769 Hz ; 25 uV
13. 32693 Hz ; 47 uV (wideband, but not resolved well on SR785)
14. 35775-38594Hz ; peak 87 uV (wideband collection of unresolved lines in SR785)
15. 39964 Hz ; 27 uV
16. 42467 Hz ; 22 uV
17. 47287 Hz ; 5.2uV
18. 47762 Hz; 3.6uV
19. 75107 Hz ; 13uV (very large peak relative to surrounding background)
20. 98000 Hz ; 3.2uV
21. 101630 Hz ; 21uV (very large peak relative to surrounding background)

The CO2 power supply cables, which normally connected with a Delrin feedthrough, are now directly connected. Unfortunately this did not solve the problem of the low laser power. The max power output was ~5 watts and the power consumption was under 10 amps. After looking through the usual suspects I'm guessing that the RF driver has crapped out again. Replacing it will have to wait until an opportunity comes up. 

The AOM had it's power supply switched from the Instek (which was being shared with the laser) to the Kepco power supply. The AOM is now running at 25v and ~2 amps. This will be checked over when the laser is once again running full power.

Sheila, Daniel, Kiwamu

Since we moved the ALS fiber AOM from a fixed frequency drive to the IMC VCO on saturday, we have had some annoying ALS locklosses.  This morning we thought through what we are using as a frequency reference now, and made some changes to the way that we lock and engage tidal. 

• We request the arms to unlock after each lock loss, so that the tidal can bleed off, and don't ask them to lock again until the IMC is locked. 
• We are no longer using the slow servo that moved the IMC VCO to beign the COMM PLL in range.  This is no longer needed, and doesn't make sense anymore.  
• We start with each arm running local high bandwidth tidal on each arm, (which means that they are also following the IMC VCO through the fiber)
• We first lock COMM, and turn off the local tidal on the X arm.  Now the IMC length is following the X arm, and the X arm VCO stays in range because the fiber light also follows the IMC VCO
• Then we lock DIFF, as soon as DIFF starts to ramp on the gain, we turn off the Y arm local tidal.  The local tidal is needed to bring the DIFF PLL in range, but would cause a verry slow instability in the system if it stays on when DIFF is locked.  
• The common tidal servo now only has to compensate for the slow motion that really is tidal, (not micorseism).  We have been leaving it off until we get off of ALS, and this seems fine for now, although we might need to engage it earlier with a very low bandwidth if we want to keep ALS locked for long time periods. 

So the final configuration is that the Y arm is the reference, the X arm length follows the Y arm length, and the IMC follows the X arm.  This is working much better I think, we haven't had the frustrating locklosses this afternoon and evening. 

Elli, Sheila

Using the OMC suspension as an actuator for HAM6 centering caused large motion of OMC, and added scattering noise to DARM (17273.)  For this reason we rearranged the centering loops to center only on AS A and not AS B (alog 17325). This is what livinsgton does, but they only use AS A WFS for feedback.  We had difficulty with our ASC on monday 17577, which we though was due to the beam nt being well centered on WFS B, and indeed reverting our HAM6 centering fixed the problem.  Now we would like to see if we can use only one of our AS WFS for control. 

One option would be to move D ETM control to WFS B, however we saw that there is a sign flip in the WFS B signal between the CARM offset where we first engage the D etm wfs and the signals on resonance, this was similar to what was seen at LLO.  Today we looked into switching the BS and SRM loops from WFS B to WFS A.  First Elli tuned the phase of the indivual segments to minimize the SRM signal seem in the Q phase.  We were able to switch the BS loops over to WFS A, we replace the input matrix element with a -1 for AS A 36 Q yaw and -0.5 for AS A 36 Q pit.  We could close the loops like this and they seemed stable, but the build up in AS 90 was lower than when we locked using AS B.  In full lock we looked at this again, we were able to switch YAW over to AS A using the same matrix element, but the zero crossing for the pitch error signal was at an alingment where the build up was not very good.  

Once the BS was switched over to AS A, we had a look at switching over the SRM feedback in DRMI.  The offsets in the error signals were much smaller after we had already switched the BS control to AS A than before, and we did close the loops.  However, something became misaligned which was fixed as soon as we opened the loop.  

Aslo, we have had at least two lock losses in the last two days that I think were caused by engaging the SRC2 loop.  This is the loop from AS_C to SR2, which has a term in the output matrix that also feeds it to SRM.  The control signal sent to SRM has caused SRM to saturate in the two attached screen shots.  

J. Kissel

I've turned on the calibration lines that are injected into the DARM loop. Their frequency has been pre-chosen to be 34.7 and 538.1 [Hz] (see selection criteria from LLO aLOG 15870). For their amplitude, instead of going through the rigor of reverse-calibrating exactly the right amplitude in DARM_CTRL [counts] to get exactly a line of x [m] in DELTA L EXTERNAL to get an exact SNR of 30, I've just copied the amplitude Joe had chosen for comparable L1 sensitivity during ER6 (see LLO aLOG 15944).


Details:
- Important parameters of the line:
                       Channel                                    Parameter                   Value        Purpose
Line 1    H1:CAL-CS_GAMMA_LINE1_DEMOD_OSC_CLKGAIN    Line Amplitude (in DARM_CTRL [ct])    0.0112 [ct]     To track the DARM OLGTF near the UGF
          H1:CAL-CS_GAMMA_LINE1_DEMOD_OSC_FREQ       Line Frequency                         34.7 [Hz]      

Line 2    H1:CAL-CS_GAMMA_LINE2_DEMOD_OSC_CLKGAIN    Line Amplitude (in DARM_CTRL [ct])    0.957 [ct]      To track changes in the DARM Coupled Cavity Pole Frequency
          H1:CAL-CS_GAMMA_LINE2_DEMOD_OSC_FREQ       Line Frequency                         538.1 [Hz]
Attached is a desktop capture of the relevant screens. Where you actually enter in / change these important parameters is on the green-backgrounded DEMOD screens.

- The computation of the optical gain calibration is still off / zero, because I haven't entered in the values for the reference open loop gain at the line frequency (and various other dams are shut along the path to actually have it correct the DARM sensing function).

- All of the new optical gain compensation EPICs records had *not* been monitored but the SDF system, because the new channels did not, by default, have their SDF mask bits set to unity. So, I have to use sdf_set_monitor to turn on all the new bits in 
/opt/rtcds/userapps/release/cal/h1/models/h1calcs_safe.snap
and then update the table (only) for them to be monitored, and then I captured a new safe SDF file with all of the settings as shown in the screenshot.

- I've checked a 10 [Mpc] reference spectra from March 27th 2015 -- the 10 [hour] lock stretch, so I could get 1 [mHz] resolution -- for features at these calibration line frequencies. Nothing there! *phew*. See attached screenshots of "Reference DARM;" both the full spectra, and the zooms at 34.7 and 538.1 [Hz].

- After lots of hemming and hawing about the bandwidth of the DEMOD's signal bandpass and frequency of the DEMOD's demodulated outputs' low-pass, I decided to just try something "reasonable," and acknowledge that we'll have to iterate. As such, I chose a 1 [Hz] bandwidth for the band-pass and a corner frequency of 0.01 [Hz] for the lowpasses. The exact foton design strings are:
Band passes (4th order chebychev bandpass, with 1 [dB] ripple, with 1st and 2nd frequencies as defined below)
cheby1("BandPass",4,1,34.2,35.2)
cheby1("BandPass",4,1,537.6,538.6)
Low passes (3rd order elliptic low pass, with 1 [dB] ripple, with 40 [dB] stop-band suppression, with a corner frequency of 0.01 [Hz])
ellip("LowPass",3,1,40,0.01)
I attach bode plots.

- Things you only find out when you turn things on: the MEDM display of some critical channels like the line amplitude were displayed on the screen in the "truncated" format. That means that numbers less unity don't show up! This is obviously yuck, since the calibration line amplitudes are less than one DARM_CTRL counts. So, I've updated the 
userapps/release/cal/common/medm/CAL_CS_GAMMA_LINE_OVERVIEW.adl
userapps/release/cds/common/medm/LOCKIN_DEMOD.adl
MEDM screens to display a precision of either 3, 4, or 6 sig figs beyond the decimal by default, and committed to the repo.