While closing out the recently replaced SUS ITMY R0 RT OSEM (alog 40634), found short on UIM chain. Short is on cable SUS_ITMY_16, pin 5, cathode side of LED for UIM UR.

This morning, Kyle and Bubba finished removing the door to BSC1.  I entered the chamber and began poking the ITMY R0 Right BOSEM cable from the OSEM connection out through the structure to the Table Cable Bracket.  No change.  I then also tried all of the following which produced no improvement to the spectra:

- Reseating the cable in the Table Cable Bracket

- Unbundling the cables that were secured to the upper structure leg

- Reseating the cable on the BOSEM itself

- Swapped the RT cable with the Side - problem went away - which meant that the problem was the BOSEM itself.

Removed BOSEM from structure and attempted to find short on the unit - no luck.  Swapped unit which meant removing it from it's adjustment bracket and rebuilding before reattaching.

Once back on the structure found it was OK.  Set OLV and 50% flag setting.

Cleaned flooring, removed tools, looked for cable routing issues in case I undid some other nice work.

Left chamber.  Kissel ran a few TFs which showed healthy.  Fil checked for HIPOT on the ESD connection and started another rounf of ground loop checks.  Tacked up door.

FAMIS 6938

The script reports: "ETMY_ST2_CPSINF_V1 high freq noise is high!"

The following appear elevated:
ITMX_ST2_CPSINF_V1
ITMY_ST1_CPSINF_V2
ITMY_ST2_CPSINF_V2
BS_ST1_CPSINF_H1_I
BS_ST1_CPSINF_V2_I
BS_ST2_CPSINF_H2_I
BS_ST2_CPSINF_V1_I
BS_ST2_CPSINF_V2_I
HAM3_CPSINF_V1

This is just a FYI for future re-enabling of BSC10 ISI, the EY HWWD tripped after an LED fault persisted for more than 20 minutes. The fault condition has subsequently been removed, however the ISI trip is latched (ISI coil drivers are powered down) until such time the front panel reset button on the HWWD chassis is pressed.

TravisS and RickS

Yesterday, we switched on the Pcal laser at Yend to check the alignment of the beams after the replacement of the ETM.

With the ETM in the nominal alignment according to the optical lever, we found that the Pcal beams at the Rx side are badly misaligned, one beam actually missing the relay mirror.

This is likely due to either a) the ETM not being properly oriented or b) the Pcal periscope orientation having shifted during B&K measurements or the addition of vibration dampers back in January.

We plan to investigate early next week, going inside the vacuum envelope and installing the Pcal target on the ETM suspension structure.

See alogs 39484 to start, this covers the corner3 CPS laying on the rail and attempts to clear it.  It seemed okay after in chamber work on  30 November, alog 39579.  However, as I look again in an effort to close the ticket, it looks like while the position has not shifted (like it was doing before,)  the noise on the channel has increased.  The increase is not causal with door removal and the other corners' sensors do not show any similar time series noise expression.  This corner3 CPS satellite box is maybe the most vulnerable to proximal activity and there is of course the 5-way cross installation complication. Dang!  I will change the FRS status from PENDING to what ever it should be now.

The attached 120 day plot shows the HAM6 CPS local sensors.

J. Kissel, B. Weaver

Far more details to come, but we've replaced the H1 SUS ITMY R0 LF OSEM in order to fix the noise / shorting problem (see LHO aLOG 40555, FRS Ticket 9683, Work Permit 7358). It's new open light current values are 

         Open Light Current / ct     GAIN          OFFSET
         (as ADC Counts)             (30000/olc)   (-olc/2)

R0 RT    29804                       1.007         -14902

I've accepted the new values in the SDF system.

Following yesterday's work on BSC1 (alog 40622), we tested the ITMY ESD cables with the HI-POT tester. All pins were tested to 1KV and passed.

After a lot of experimentation, I have found a way to improve the attenuation of frequencies below 9 Hz in the calibration by 1-2 orders of magnitude, without significantly increasing the computational cost or latency of the pipeline. Here is a list of what I've changed and what I've kept the same:

• In the actuation path, before the actuation filter, I have added a separate high-pass filter using Matlab's firls() function (documentation). firls() designs a linear-phase FIR filter that minimizes the weighted integrated squared error between the desired frequency response in specified intervals and the approximated response of the filter. The filter I've found most effective is designed to have a frequency response of 1 from 9 Hz to the Nyquist rate, and 0 from DC to 8 Hz.  I found improvement when I weighted the stop band more heavily by a factor of 100.  This filter was 2 seconds in length for the tests that I ran.
• I shortened the actuation filter itself from 6 seconds to 4 seconds. (The main reason we needed such a long filter before was to prevent spectral leakage, which is now taken care of by the previous high-pass filter.) It still contains half of a Hann window to the fourth power to roll off low frequencies, in order to further attenuate those frequencies. I found that this roll-off actually worked better than any version of least squares filter I tried in its place.
• In the inverse sensing filter, I replaced the half Hann window to the fourth power with Matlab's least squares filter using firls(). For some reason, this worked better in the inverse sensing filter than the Hann window stuff, even though it did not work better for the actuation. I designed this filter to have a frequency response of 0 from DC to 5 Hz (weighted by a factor of 100) and a frequency response of 1 from 9 Hz to the Nyquist rate. This is what seemed to produce the best results. I did not add a separate high-pass filter in the inverse sensing path, as it seemed unnecessary, and filtering at 16384 Hz gets expensive.

Of all the things I tried, this is what worked the best. Reasons I did not make this even better include:

• I haven't figured out a better way yet
• It is possible to do better with longer or more filters, but since we are doing this in the time domain with FIR filters, adding more filtering gets computationally expensive and adds latency. It is necessary to balance computational cost with quality, as we do not want the pipeline falling behind in low-latency or taking forever to produce offline data on the clusters.

Several plots are attached to show the new features. The first 5 plots are the frequency responses and comparisons to the ideal models for each of the filters used. The last 3 plots are comparisons of C01 data with data produced using the new filters. The attenuation is better by about 1-2 orders of magnitude, and there is just a very small amount of ripple added below 20 Hz.

WP 7364 -- Locked EndX HEPI this morning, pretty close to operating position, Z not so much.  Will leave this WP open until the HEPI is unlocked.

ETMX found in ISI DAMPED HEPI OFFLINE.  Took SEI guardian manager to DAMPED--this took the HEPI to Robust Isolated.  The HEPI was then locked onto its stops as closed to the Isolated position as possible: dX dY dRX dRY are all under 10um(urad), and dRZ is less than 200nrads. dZ is 83um but I figured this was the least significant dof for the upcoming task.  These di values are the difference from the nominal isolated position.  HEPIs for the BSC don't have a 'down' lock so it is difficult to keep it from squirting up as the sides are pinched into position.

Of note, when the ETMX Optical Lever was recentered on 15 Feb, it was done without the HEPI holding the nominal orientation.  Fortunately, Jim and I have debiased the HEPI position onto the DSCW springs and as you can see on the attached plot, the isolated/not isolated amounts to about 6 Oplev yaw plot units (urads?Yes urads).  Still, nominally, oplev centering should be done with the HEPI fully isolated (ISI not so important.)

The attached 3 hour plot has the HPI & SEI guardian states (chans 1 & 2), the OpLev Pit & Yaw (3 & 4), with the rest being the HEPI position residuals. Note the annotations showing the shift in the OpLev Yaw when the HEPI Isolates and the residuals go to zero.

Summary:
The core functionality of the Matlab DARM model has now been replicated in Python. Attached are figures in a single PDF file showing the primary results. By eye, these look reasonable. A more detailed study comparing to the Matlab model is forthcoming. I also replicated a study made for the L1 detector by Joe B. (see LLO aLOG 29622). I propose to call this code pyDARM.

Details:
I have ported most of the core functionality of the DARM model from Matlab into Python. So far, I have done spot checks by eye to make sure that the results look sensible. I have not yet done a detailed study comparing to the Matlab version, but will do so soon.

I have produced plots showing:
1) DARM digital filters
2) Sensing function
3) Actuation function
4) Open loop gain
5) Frequency dependent actuation authority of each stage compared to inverse sensing
6) Ratio of each stage to the overall calibration

As can be observed, the scale of each figure appears reasonable (comparing with, e.g., G1700316), the OLG is stable, and with a UGF with the correct value (by eye). The contribution of each suspension stage is closely matching L1's results using the Matlab model (see LLO aLOG 29622).

What was done:
- Write python version of Matlab functions to parse Foton filter files and to compute IOP downsampling filters from RCG code coefficients
- Exported numerical values of zeros, poles, gain, delay from analog AA and AI models (these are objects in .mat files)
- Exported ASCII file of the frequency response for the suspension force-to-length for each stage. This is read in and used in the python DARM model, and so far can only be at specific frequency points
- DARM filter bank digital filters computed, sensing function and actuation functions are computed from parameters
- Intermediary data products can be accessed
- Code structure is "flatter", meaning less jumps between different functions/files. Hopefully this makes the code more accessible and readable.

Required python modules (so far): scipy (e.g., filters), numpy (e.g., arrays/array math), collections (for namedtuples), matplotlib (for plotting)

Quirks found along the way:
- You can't directly multiply or add filter objects together in Python (the + and * functions are not overloaded in Python). I had to code up my own version to 1) add filters by using polynomials from roots, computing a transfer function filter, and then converting to a zpk object, all using scipy built-in functions; and 2) multiply filters by appending zeros together, poles together, and multiplying gain.
- The scipy sos2zpk() function is not exactly like Matlab's version. I found an extra zero and pole when converting because Matlab removes any zeros in the 3rd and 6th positions of an sos section before computing a filter from the sos coefficients

To do list (short term):
- More detailed study comparing Python with Matlab models
- Read in a config file
- Make an L1 model to check for any differences
- See if there is a way to read Matlab .mat file and objects therein. This didn't look trivial when I tried at first, which is why the analog AA and AI models were exported as well as the frequency response of each suspension stage
- Address how to get the force-to-length transfer function for each stage for arbitrary frequencies
- Add computations for GDS / DCS pipelines

Longer term:
- Hook this into a pipeline from measurement to model to uncertainty estimate pipeline

Valved out CP4 turbo around 10:30 am local for bake enclosure work nearby. Expect pressure at PT-245B to drift up.

One of the PSL Enclosure's Mac minis is dead.  Its hard disc cannot be repaired.  The computer will be replaced in the near future.


Carlos / Peter

The installation of CP4's bake enclosure started today. All parts were delivered and the uni-strut framing is ~1/3 installed. We will resume at 6:30am tomorrow I'll post some pictures tomorrow.

This morning the purge air skid was turned on.  The dew point was measured at -33 ^oC after the drying towers cycled twice each.

After Kyle and Gerardo slow vented the corner, Gerardo and I pulled the 4.5" feed-thru for ITMY CABLE #7 and #8.  We then pulled both in-vacuum cables off the feed-thru in order to swap in a fresh copper gasket.  I re-tightened the back-shell screws and inspected cable #8 and then reseated it - it felt better going in that it came out so we had hope.  Running th spectra showed no improvement however.  We then tried to inspect the ~1ft of cable we were able to pull out through the feed-thru hole and wiggle things before reattaching it to the chamber.  Still no change in spectrum.  Boo.

We'll embark on pulling the door tomorrow.

(Sad face.)

Green beam was injected into TMSY and into EY, green centering on TMS QPD is working but no retro reflection from EY. I scanned TMSY PIT and YAW and observed green beam in ISCTEY but it would be much easier to just look at the beam in chamber. Will continue tomorrow.

EY was put back into laser safe.