Now that the 3f locking looks so cool for the PRMI, I suppose that the PRMI + arm stuff will be very successful.

At LLO, I've just noticed the screens that they have for the single pendulums / TTs. I'm attaching a screenshot of the one Zach is using for the steering into the OMC. We should grab these and replace our existing SUS screens with them.

Totally agree. The old suspension screen should be driven away.

With the help of an expansion card,  I verified that the + 15V and + 24V from the eurocrate in the slot I've identified for the PZT driver boards are making their way to the board. The slot is at the right-most end of the eurocrate in 1Y4, and the rack door was getting in the way of directly measuring these voltages once I hooked up the driver board to the expansion card. So I just made sure that all the LEDs on the expansion card lit up (indicating that the eurocrate is supplying + 5, + 15 and + 24V), and then used a multimeter to check continuity between the expansion card and the driver board outside of the eurocrate. The circuit only uses + 15V and + 24V, and I checked for continuity at all the IC pins marked with these voltages on the schematic.

Since the whole point of this test was to see if the slot I identified was delivering the right voltages, I think this is sufficient. I will now need to fashion a cable that I can use to connect a DC power supply to the PZT driver boards so that these can be tested further.

The high voltage points (100V DC) remain to be tested.

I am prepping to do the POP QPD calibration, and so have turned off the POP QPD, and put it onto a micrometer stage.  My plan is to (after fixing the ASC servo filters to make the servo AC coupled, rather than DC coupled) lock the PRM-ITMY half cavity, and use that beam to calibrate the QPD.  While this isn't as great as the full PRMI, the PRMI beam moves too much to be useful, unless the ASC servo is engaged.

While on the table, I noticed 2 things:

* In order to place the micrometer, I had to temporarily move the POP55 RFPD (which has not been used in quite a long time).  I think it's just that the panel-mount SMA connector isn't tight to the panel inside, but the RF out SMA cable connector is very loose.  I have moved the POP55 RFPD to the very very south end of the SP table, until someone has time to have a quick look. (I don't want to get too distracted from my current mission, since we haven't put beam onto that PD for at least a year).

* The ITMX oplev beam setup isn't so great.  The last steering mirror before the beam is launched into the vacuum is close to clipping (in yaw... pitch is totally fine), and the steering mirror outside of vacuum to put the beam on the QPD is totally clipping.  The beam is falling off the bottom of this last steering mirror.  Assuming the beam height is okay on all of the input optics and the in-vac table, we need to lower the last steering mirror before the oplev QPD.  My current hypothesis is that by switching which in-vac steering mirror we are using (see Gautam's elog 8758) the new setup has the beam pointing downward a bit.  If the problem is one of the in-vac mirrors, we can't do anything about it until the vent, so for now we can just lower the out of vac mirror.  We should put it back to normal height and fix the oplev setup when we're at atmosphere.

Alex and Eric

For the photodetector frequency response automation project, we plan to add modules to rack 1y1 as shown in the attached picture (Note: boxes are approximately to scale). 

The RF switch will choose which photodetector's output is sent to the Agilent 4395A Network Analyzer.

The Diode Laser Module is powered by Laser Power Supply, will be modulated by the Network Analyzer and will be output to a 1x16 optical splitter which is already mounted in another rack (not pictured). 

The Transformer Module has not been built yet.

We would like to install the power supply and the laser module tomorrow and will not begin routing fibers and cables until we post a drawing in the elog.

Also, our reference photoreceiver arrived today.

[Koji, Manasa]

I wanted to investigate on the ALS electronics(in particular the beatbox and the phase tracker) and find out if the beatbox is showing a linear behavior
as we expect it to and as to why we have been seeing sudden jumps at the phase tracker output.

I have been using the Xarm part of the beabox.
I used Marconi as well as signal generator to do frequency sweep/modulation at the RF input of the beatbox and looked at the I_MON output of the beatbox.

We observed sudden jumps in the beatbox output from time to time while we either varied the carrier frequency or the RF amplitude.
Also the beatbox output shows high frequency oscillations at ~95MHz (source unknown). It is for sure that the beatbox is not behaving the way it should
but we could not tell more or troubleshoot with the beatbox mounted on the rack.

I am going to let Annalisa do her Y arm ALS scan tonight and pull out the beatbox tomorrow to fix it.

[Koji, Nic]

- Locked PRMI with REFL165 I/Q

- Aligned the POP beam on the QPD. We found that the vertical motion of the beam appeared in the yaw signal, and horizontal motion in the pitch signal.
  This was fixed by swapping the cables to the ADC. Later it turned out that this was caused by the calibration setup for the QPD.
  We requested Jenne to fix the QPD on the table with the current orientation.

- Re-implemented the AC-coupled ASC servo. The filters were just copied from the previous PRM ASC servo (in the SUS ASC filter).
  The same filter was installed to the pitch and yaw filter modules for now. The gains were adjusted to have some stable lock stretches.
  C1:ASC-PRCL_YAW_GAIN: -0.01
  C1:ASC-PRCL_PIT_GAIN: -0.01

  The power spectra of C1:ASC-PRCL_YAW_IN1 and C1:ASC-PRCL_PIT_IN1 were attached.
  The reference curves are the ones with the servo on. The other two are the free-running stability of the QPD output.

- Modified the up and down scripts for the PRM ASC for the new setup.
  It first turns on the inputs of the filters and then turn on FM2/3.
  It assumes that the outputs are engaged all time.

The bank marked channel 9-16 is free, but the connector is a 40 pin IDC and I need to know the exact pin-out configuration before I can set about making the custom ribbon cable that will send the control signals from the DAC card to the PZT driver board. 

The DAC interface board on rack 1Y4 seems to be one of the first versions of this board, and has no DCC number anywhere on it. Identical modules on other racks have the DCC number D080303, but this document does not exist and there does not seem to be any additional documentation anywhere. The best thing I could find was the circuit diagram for the ADL General Standards 16-bit DAC Adapter Board, which has what looks like the pin-out for the 68 pin SCSI connector on the DAC Interface board. Koji gave me an unused board with the same part number (D080303) and I used a multimeter and continuity checking to make a map between DAC channels, and the 40 pin IDC connector on the board, but this needs to be verified (I don't even know if what is sitting inside the box on 1Y4 is the same D080303 board).

Jenne suggested making a break-out cable to verify the pin-outs, which I did with a 40-pin IDC connector and a bit of ribbon wire. The other end of the ribbon wire has been stripped so that we can use some clip-on probes and an oscilloscope to verify the pin-outs by sending a signal to DAC channels 9 through 16 one at a time. On the software side, Jenne did the following:

• Restarted the mx_stream on c1iscey  (unrelated to this work)
• 8 Excitation points added in the simulink model on c1scy 
• Model compiled and installed

We have not restarted c1scy yet as Annalisa is working on some Y-arm stuff right now. We will restart c1scy and use awggui to perform the test once she is done.

 Pink edits by JCD

I was bad, and forgot to elog the most important part of my work yesterday - that I had rotated the POP QPD by 90 degrees, so that I could fit the micrometer onto the table.  There is a sticker on the front of the QPD to indicate which direction is "X" and "Y" for the output of the readout box.  Right now (and the way that I will mount the QPD to the table, after I redo the calibration today), X is PITCH, and Y is YAW.  Koji and Nic swapped the cables to the ADC to make this all consistent.

Yesterday, I locked the PRM-ITMY half cavity, and tried to take calibration data.  However, with no ASC servo engaged, the beam was still moving.  Also, with only the half-cavity, I had very little light on the QPD, and since it has internal normalization, the outputs can get a little funny if there isn't enough light.  I had checked, and even with the gain cranked up to maximum, the "light level too low" LED was illuminated.  So, my calibration data from yesterday isn't really useful.

Today, hopefully after lunch, I will lock the PRMI with the new AC-coupled ASC servo, so that I can have the servo on, and the PRMI locked on the sideband, so that I have more light on the QPD. 

After that, it seems that the final thing we need to do before we vent is hold an arm near, but off resonance, lock the PRMI, and then swing the arm in and out of resonance a bit.

 Jenne just rebooted c1scy and daqd on the framebuilder. We will do the actual test after lunch.

[Jenne, Alex] 

Calibration data for the POP QPD has been taken, with the PRMI locked on sideband (with AS55Q and REFL33I, since it stayed locked longer with those 2).  ASC was on, AC coupled. 

We didn't get too far on either side of center of the QPD, since the ASC servo would go unstable, so we only explored the roughly linear region.  Data / plots / analysis to follow.

Alex, Gautam and Steve,

Single mode fiber 50m long is layed out into cable tray that is attached to the beam tube of the Y arm.

It goes from ETMY to PSL enclosure. It is protected at both ends with " clear- pvc, slit corrugated loom tubing " 1.5" ID

The fiber is not protected between 1Y1 and 1Y4

  Summary:

The pin-outs for the DAC interface board have been determined.

Details:

• I used a temporary break-out cable (pic attached) and connected the 40pin IDC connector on this to the DAC interface board at 1Y4.
• I had a hypothetical pin-out map which was to be verified. So I connected pairs of ribbon wire to an oscilloscope in the configuration which I believed to be correct, and then used awggui to send a 3Hz, 10000 count sine-wave to the corresponding channel via the excitation points set up earlier.
• I verified that the correct waveform showed up on the scope screen. I then tried sending the same signal to another DAC channel and verified that there were no accidental shorts/bad connections. The signal was fairly noisy, but this was probably because of the makeshift connections.
• Repeated the above for all 8 channels in the bank marked 9-16 on the DAC interface board.

Turns out that my deductions using the D0902496 wiring diagram, a spare D080303 DAC to IDC adaptor and a multimeter were correct! The pin outs as determined by this test are sketched in the graphic below.

To Do:

•  Now that the pin-outs have been determined, I need to go about making the custom ribbon that will connect the 40pin IDC on the DAC interface board to the 10-pin IDC on the PZT driver board. Because there is a pair of wires that will have to be 'skipped' while going from the 40-pin to the 10 pin IDC (corresponding to the pair not-connected between two DAC channels on the 40-pin IDC), this may be tricky.

Misc:

The excitation points added to the simulink model are still there, I plan on keeping it as such till I finish installation of the boards as they will be useful for testing purposes.

Pin-Outs of the DAC to IDC Adaptor (D080303) inside the "DAC Interface Box at 1Y4":

Makeshift break-out ribbon cable:

The low UGFs of the MC WFS servos made the MC insane thesedays:
The servos are too slow and we kept having significant misalignment left uncompensated.

I increased the total gain of the MC WFS from 0.01 to 0.4 (x40) to make the UGFs of the
WFS paths to ~2Hz. This was too much gain for the QPD path so the gains for the QPD paths
were reduced by a factor of 4 (x10 in total).

The script mcwfsup was also modified accordingly.

The MICH actuation with PRM/BS was investigated again.

(ITMX -1 / ITMY +1) is equivalent to (PRM -0.267 and BS +0.50).

- PRMIsb was locked with REFL33I&AS55Q.

- Using the locking module in the LSC model, actuate ITMX (-1) and ITMY (+1) at 580.1Hz. Note that the notch filters in the MICH/PRCL servos were on.

- Look at the peak in the AS55Q spectrum. Tune the BS element in the output matrix of the lock-in to minimize the peak height.
=> The peak was minimized at BS = -0.50.

- Look at the peak in the REFL33I spectrum. Tune the PRM element in the output matrix of the lock-in to minimize the peak height.
=> The peak was minimized at PRM = +0.267

- These measurement leads to the conclusion mentioned above.

 [Annalisa, gautam]

Summary:

We have measured the open-loop transfer function of the Y-end green PDH loop. From the measurement, the loop UGF is ~12kHz.

Details:

We have been trying to measure this transfer function for some time now, and playing around with various points of injecting the excitation and measuring the output. Koji helped arrive at one that actually worked, and the scheme used to make this measurement is shown in the sketch below. The SR785 signal analyzer was used to make the measurement, while an SR560 preamp was used to sum the output from the PDH box (PZT-OUT) and the excitation, with this sum being delivered to the auxiliary laser PZT via a pomona box that sums the servo output and the signal from the LO. The transfer function measurement made was a1/a2 w.r.t the sketch attached.

• The swept-sine measurement was done from high to low frequencies, as the open-loop gain was expected to be high at low frequencies.
• After some trial and error, we realised that the excitation amplitude on the SR785 can be varied continuously during the course of a swept sine measurement using the dial on the front panel. We started out with a 1mVpp signal at the high end of the frequency sweep (~102kHz, the upper limit on the SR785) and went up to 17mVpp at ~30Hz). These values were determined by trial and error, and were approximately the maximum that did not kick the loop out of lock/into a higher order mode.

Remarks:

• As per this paper, the expected bandwidth of this loop is expected to be ~30kHz, while the measured UGF was more like 11.7kHz. Perhaps we can get this closer to the expected 30kHz by increasing the servo gain. The measurement shown was done with the servo gain knob on the Universal PDH box set to ~7.86. We tried two other values, ~8.2 and 10 (this was the limit on the knob), but the UGF first increased to ~13kHz (for the 8.2 gain), and then decreased to ~5kHz with a gain of 10. Not sure why this was, but it can be looked into further. 
   

Set-up to measure Y-end Green PDH transfer function:

Measured Open Loop Transfer Function:

 The beatbox output showed high frequency oscillations during the troubleshooting process yesterday. I removed the beatbox from the rack. With no RF inputs, just powering the beatbox showed these high frequency oscillations at the beatbox output. This confirms that these oscillations are from the op-amp AD829JR. I replaced these with low noise OP27G. Also I removed the AD829JR that were soldered to the frequency divider and comparator which are not being used. Output buffer U10 was also removed.

After replacing with OP27G, I rechecked the beatbox with and without the RF input. There were no more high frequency contaminations and beatbox seemed to behave as it is supposed to when a frequency modulated RF input is fed. I put the beatbox back on the rack and did  a quick recheck.

Before (top) and after (bottom) pictures

[Manasa, Jenne, Annalisa]

I was going to find the beat note to start the cavity scan, but I couldn't.

These are the steps I followed:

• locked the arm with IR to reduce the arm swinging
• locked the green on the arm
• started changing the green temperature setting the offset from the slow servo2 in the ALS. The PSL slow actuator ADJ was always set approximately to zero, and the PSL temperature was checked in order to set the auxiliary laser temperature where the beat was expected (as in the plot)

After spanning the temperature by approximately 4degC, we started be suspicious that I couldn't find the beat in the range of temperature where it was supposed to be found, and we started making several trials:

• PD output disconnected from the beatbox and connected to the cable running to the Control Room
• Checked that the cable going to the Control Room was working by sending a signal with the Marconi (the cable was working)
• Put back the amplifier that had been previously removed
• PD DC output checked with the oscilloscope
• Spectrum analyzer connected to the PD output without passing trough the cable

The same trials were done also for the X arm, but we didn't succeed in finding the beat for the X neither.

I found the beat note for X arm. I did not change anything this morning (to the best of my knowledge). Hooking up the spectrum analyzer, I could find the beatnote signal at the PD RF output, after the amplifier and also at the MON port of the beatbox. I still don't know what changed from the last night set of trials

I found the beat note for the Y arm. Nothing was changed with respect to yesterday night, but the beat is back!

 Installed 0.5" ID 10 ft long protective tubing at the PSL end of the  ETMY fiber this morning. Here I had to cable tie a bunch of cables at the east side of the PSL enclosure.

They were hanging off the table blocking space were the sliding doors move.

 At the ETMX end of the X-arm fiber received the same protective tubing.

 I did the following with the PZT Driver Board: 

•  With an expansion card attached to the driver board, I used an Agilent E3620A power supply to verify that the 15V and 24V supplies were reaching the intended ICs. It turns out that the +24 V supply was only meant to power some sort of on-board high voltage supply which provided the 100V bias for the PZTs and the MJE15030s. This device does not exist on the board I am using, jumper wires have been hooked up to an SMA connector on the front panel that directly provides 100V from the KEPCO high voltage supply to the appropriate points on the circuit.

•  All the AD797s as well as the LT1125CS ICs on the board were receiving the required +15V.

    

The next step was to check the board with the high-voltage power supply connected.

•  The output from the power supply is drawn from the rear output terminal strip of the power supply via pins TB1-2 (-OUT) and TB1-7 (+OUT). I used a length of RG58 coaxial cable from the lab and crimped a BNC connector on one end, and stripped the other to attach it to the above pins.

•  There are several options that can be configured for the power supply. I have left it at the factory default: Local sensing (i.e. operating the power supply using the keypad on the front of it as opposed to remotely), grounding network connected (the outputs of the power supply are floating), slow mode, output isolated from ground.
  

• I was unsure of whether the grounding network configuration or the 'positive output, negative terminal grounded' configuration was more appropriate. Koji confirmed that the former was to be used so as to avoid ground loops. When installed eventually, the eurocrate will provide the ground for the entire system.
• I then verified the output of the HV power supply using a multimeter from 2V up to 150V.
• I then connected the high voltage supply to the PZT driver board with a BNC-SMA adaptor, set, for a start, to output 30V. Ensured that the appropriate points on the circuit were supplied with 30V.
  

I then hooked up a function generator in order to simulate a control signal from the DAC. The signal was applied to pin 2 of the jumpers marked JP1 through JP4 on the schematic, one at a time. The signal applied was a 0.2 Vpp, 0.1 Hz sine wave.

•  The output voltage was monitored both using a DMM at the SMB output terminals, and at the monitor channels using an oscilloscope. The outputs at both these points were as expected.
• There are 4 potentiometers on the board, which need to be tuned such that the control output to the piezos are 50V when the input signal is zero (as this corresponds to no tilt). The gain of the amplifier stage (highlighted in the attached figure) right now is ~15, and I was using 30V in place of 100V, so an input signal of 2V would result in the output saturating. This part of the circuit will have to be tuned once again after applying the full 100V bias voltage. 
• Koji suggested decreasing the gain of the amplifier stage by switching out resistor R43 (and corresponding resistor in the other 3 stages on the board) after checking the output range of the DAC so that possibility of unwanted saturation is minimised. I need to check this and will change the resistors after confirming the DAC output range. 
• The potentiometers will have to be tuned after the gain has been adjusted, and with 100V from the high-voltage DC power supply. 

To Do:

• Switch out resistors
• Tune potentiometers with 100V from the HV supply
• Verify that the output from the board after all the tuning lies in the range 0-100V for all possible input voltages from the DAC.
• Once the output voltage range has been verified, the next step would be to connect a PZT to the board output, affix a mirror to the tip/tilt, and perform some sort of calibration for the PZT. 

I ran a series of diagnostics on the X arm ALS to look at how the beatbox behaves after the makeover.

Diagnostic tests run:
1. X arm ALS in-loop spectrum
2. X arm ALS out-of loop spectrum
3. X ALS scan of the X arm cavity

The noise suppression looks better after the makeover at the lower frequencies. To suppress the noise at high frequencies, we would have to add more whitening filters.

[Annalisa, Jenne, Nic]

After having troubles with the Xarm earlier (maybe Manasa can write/say something about this?  Something about perhaps seeing the phase tracker jump, and cause it to lose lock?), we moved on to the Y arm. 

Annalisa locked the Yarm green, and closed the ALS loop.  I believe that earlier today, she tuned the gain such that we don't start getting gain peaking at a few hundred Hz.  We would like to get a script going, so that it's not so labor intensive to reclose the ALS loop after an MC lockloss....but that's a daytime task.

We then found the IR resonance, using only the Yarm ALS system.  After Manasa's work yesterday, the Yarm was very stable while locked with the ALS.  We took a power spectrum of POY11_I_ERR, which I have calibrated using the number in elog 6834 of 1.4e12 cts/m, or 7.14e-13 m/ct.  See the figure below.

After that, we changed the offsetter2 offset such that the arm was off resonance, but not so far off that we crossed any significant resonances (in particular, we wanted to not go as far as the 55MHz resonance). 

Then, I tried to lock the PRMI for a while, but the alignment wasn't very good.  We knew that the Yarm was well aligned, since our IR resonance was > 0.98, but it had been a while since we had aligned the X arm.  I tweaked the ITMX position to make the Michelson dark, and then tried acquiring PRMI lock.  At first, I tried with REFL165 I and Q, but with the non-ideal alignment and the offset in the 165 diode (LSC offsets was not run this evening), I wasn't catching any locks.  I then switched to AS55Q and REFL33I, but wasn't able to catch lock there either. 

The MC lost lock, which made us lose the ALS loop, but the ALS had been locked for more than 30 minutes, at least.  I tried locking the PRMI with the current alignment (after having misaligned ETMY), but was only able to get lock stretches of 1 second at maximum.

We are calling it a great success for the night, since we have confirmed that, at least for the Yarm, Manasa's beatbox work has improved things.  Also, we have a pretty solid plan for trying the PRMI+arm tomorrow, even though it didn't work out tonight.

 The X arm was locked with TRX>0.98 earlier last night while I was measuring the out of loop noise of the phase tracker.

ETMY optical table top was grounded to the ETMY chamber through 1 Mohms this morning. I  also strain releifed relieved a few cables that were pulling on components directly.

There are 4 oscilloscopes left on the AP optical table top.... It's only 25 lbs... Do not leave anything on the optical table tops!

[Eric, Alex]

We mounted our Laser Module and Laser Power Source in rack 1y1. We plan to add our RF Switch and Transformer Module to the rack, as pictured. (Note: drawn-in boxes in picture are approximately to scale.) Note that the panel of knobs which the gray boxes overlap is obsolete and will soon be removed.

There are essentially two major portions of the ISS I am designing. One system has the voltage reference, differential amplifier and filtering servo (schematic attached) while the other has a comparator circuit and a triggering mechanism. The first system amplifies an error signal obtained from the PD output and the voltage reference, which is then fed back through the AOM. I've done a lot of work designing/prototyping this first half and now I'm starting to design the second half.

The second system's main purpose is to maintain loop stability as the ISS is engaged. Let's assume a user has decided they want noise suppression. They would first close the ISS feedback loop and an error signal would pass through three unity-gain buffers, providing minimal noise reduction. The user can then send a signal to theTRIGGER 1 port to switch the first stage from its unity-gain position to its filtering position and reduce the intensity noise further. This signal will most likely be digital in origin. Alternatively, when the user first closes the ISS loop, the first stage can already be in its filtering position rather than necessitating two commands.

A test channel (not drawn in the included schematic) will monitor the RMS level of the incoming signal from the PD. This noisy AC signal will first be amplified and then passed through an RMS-to-DC converter. The resulting DC signal is used as a part of the triggering mechanism for later stages. Once the first stage has been switched manually, and the DC signal corresponding to RMS noise of the PD output drops below a certain threshold, stages 2 and 3 will be internally triggered with a short delay between them. Toward being able to detect this threshold, I have designed a simple comparator circuit with an LT1016. The circuit has a fairly low-level output when the input voltage is larger than the threshold (about 1.6 V for my simple prototype), but when the input passes below the threshold, the comparator puts out almost 4 V, a number limited by the supply voltage. The schematic is shown below.

The component V2 and the various voltage dividers serve to establish the reference/threshold voltage. Note that although the LT1016 is not powered in the schematic, it requires ±5 V (a max of 7 V). The above circuit was also prototyped on a breadboard and I characterized it with an oscilloscope. Using a CFG253, I made a low frequency (~0.3 Hz) triangle wave with an amplitude and DC offset such that it oscillates between 0 and 5 V. This was applied to the IN node in the above schematic. The input waveform and the circuit's response (voltage at the OUT node) are shown below. As expected, R2 serves to establish hysteresis. The comparator switches to 'high' output until the input drops below 1.6 V, and then it doesn't switch back to the 'low' output until the input goes up to ~3.4 V.

This behavior is ideal for our application as we can detect when the DC signal from the RMS-to-DC converter drops below a certain level (i.e. the first stage that has been activated does some amount of filtering to lower RMS noise), and then we can trigger subsequent filter stages off of the comparators high-level output. 

This circuit could easily be used to drive the MAX333a switches shown in the first schematic attached. I believe the low-level output is not sufficient to switch the MAX333a although the ~4 V high-level output is quite sufficient. Regardless, these exact values (thresholds, outputs etc) will be determined after I have a better idea of the RMS noise of the laser without any intensity stabilization as well as a solid understanding of how the AD8436 RMS-to-DC converter works. This was simply a proof of concept for lower threshold detection using basic Schmitt trigger topology.

Yesterday I did a cavity scan with IR while holding the Yarm with green.

ALS servo tuning:

• C1ALS-BEATY_FINE_PHASE

             The gain of the loop is set such that BEATY_FINE_Q_ERR x GAIN = 120k. This is a kind of "empirical low" in order to have the UGF around 1kHz. 

• C1ALS_YARM

             Start with FM5 [1000:1] enabled, determine the sign of the gain increasing it in small steps and making sure that the mirror doesn't get a kick. Then gradually raise it while looking at the BEATY_PHASE_OUT power spectrum.

             Enable FM7 [RG16.5], FM6 [RG3.2], FM3 [1:5], FM2[0:1], FM10 [40:7].

Plot 1 shows the power spectrum of BEATY_PHASE_OUT (calibrated in Hz).

1. blue curve - ALS disabled
2. green curve - in loop measurement, ALS enabled and servo tuned as described above
3. grey curve - RMS of the in loop measurement
4. red curve - out of loop measurement (arm locked with IR)
5. pink curve -  RMS of the out of loop measurement

Offset setting and cavity scan

The C1ALS_OFFSETTER2 was used to set an offset for ALS scan.

• LPF30m enabled
• Ramp time set to 150s
• Offset set to 1500 (approximately 3 FSR in this interval)

Many scans have been done to find the optimal offset conditions, I only attached one (Plot 2).

I also misaligned the END mirror in pitch to enhance the HOMs peaks, but it turned out that it was not enough, because I didn't see a very big difference between the "aligned" and the "slightly misaligned" measurements (Plot 3). 

NEXT STEPS

Increase the cavity misalignment both in pitch and in yaw and repeat the measurement.

 Summary:

Continued with tests on the PZT driver board. I made a few changes to replace defective components and also to modify the gain of the HV amplifier stage. I believe the board has been verified to be satisfactory, and is now ready for a piezo to be connected, tested and calibrated.

Changes made:

• I tested the board with the full 100V bias voltage today, working my way up from 30V in steps of about 20V and verifying the output at each stage.
• In order to deliver 100V to the board, it was necessary to change the maximum current limit on the KEPCO supply, which is set at default at ~1.6 mA. The KEPCO power supply placed near rack 1X2 (which I believe was used to power a piezo driver board) is labelled 150V, 12 mA, though I found that the board only drew 7mA of current when the power supply output 100V. I have set the limit to 10 mA for the time being.
• The potentiometer in the third stage (R44 in the schematic) was faulty so I replaced it with another 100K potentiometer, which was verified to work satisfactorily.
• We expect the DAC output to supply a voltage to the input of the PZT driver board in the range -10V to 10V. Today, I verified this by using my temporary break-out cable. I hooked this up to the DAC at 1Y4 and output a 3 Hz sine wave with amplitude of 32000 counts (the maximum) on channel 9. The output as observed on an oscilloscope (image attached) was a 10Vpp sinusoid, confirming the above hypothesis. As mentioned in my previous elog, the gain of the high-voltage amplifier stage is ~15, which would mean the output would saturate if the input were to be >6V. I have changed the gain of all 4 stages (M1-pitch, M1-yaw, M2-pitch and M2-yaw) to ~4.85 by swapping the 158k resistors (R43, R44, R69 and R70 in the schematic) for 51k resistors. 
• It was necessary to change the value of the biasing potentiometers after the change in gain so that 0 input voltage once again provided 50V at the output, as required by the PZTs for there to be no tilt. This was done and verified. This biasing voltage now is ~10.4V in all four stages.
• Having adjusted the gain, I tested the circuit over the expected full range of the input voltage from the DAC (from -10V to 10V) from the DS345 function generator (0.05Hz sinusoid). I monitored the output using a multimeter, as the monitor channels were peaking at ~7V, which was above the limit for the oscilloscope I was using. It was verified for all four channels that the output was between 0 V and 100 V (the safe range quoted in the datasheet for the tip-tilts, for this range of input voltages. So I think we are ready to connect a PZT to the board and conduct further tests, and calibrate the PZT. 

Pending Issues:

• Koji pointed out that there has to be an anti-imaging filter stage between the DAC output and the filter stage, which I had not considered till this point.Another subtle point is that the DAC output is differential while the driver boards have a single-ended input, which means we effectively lose half the range of the PZTs. 
• A suitable candidate is the D000186-rev D. Some information about the present state of this board is detailed in this elog. This board also solves the problem of the differential vs single input as the input to the AI board is differential while the output is single-ended. Koji has given me one of the boards he had collected. 
• Some changes will have to be made to this version of the board in order to make it compatible with the existing DAC. I will first have to measure the power spectrum of the DAC output to verify that the AI boards need notches at 64k and 128k. The existing notches are at 16k and 32k, and once the DAC power spectrum has been verified, I hope to affect the necessary changes by switching out the appropriate capacitors on the existing board. 
• The AI board is an extra element which I have now added to an updated wiring diagram, attached.

Revised Wiring Diagram:

DAC Max. Output Trace on Oscilloscope

[Koji, Manasa, Annalisa]

I made several trials to scan the arm on the IR TEM00 resonance while the PRMI was held with REFL165I&Q.
It was so hectic to keep multiple systems running correctly. We talked about how it should be automated.
We'll gradually offload the switching works on scripts.

In a good alignment condition, when I swept on the resonance, everytime the PRMI lost the lock. It reacquired
once the arm passed the resonance.

Lately I got difficulty to acquire lock of the PRMI while the arm is waiting at its off resonance.
If I change the ALS offset I got a stable lock in a certain offset, and did not get in another offset
so there could be something systematic. (The arm was in between the carrier resonance and the next sideband (55MHz) resonance).

-----

Procedure

[Preparation]

- Run LSCoffset script.

- Misalign PRM. Lock and align the arms with ASS.

- Go into the tables. Align the oplevs for ETMX/Y, ITMX/Y, and BS. (Very important for alignment stability)

- Align PRMI and lock PRMI. Unlock once.

- Go into the BS/PRM table. Align the oplev for PRM.

[ALS]

- Misalign PRM by -0.2

- Find the beat note at around 50MHz by changing the Yarm SLOW control. Today the PSL SLOW was ~0.24, and the Yarm SLOW was -10981.

- Reset Phase Tracker History (Important)

- Engage Yarm ALS with FM5. Tested the sign of the servo by giving 0.01 or -0.01. In my case, the negative number worked fine.
  Gradually increase the gain up to -10. Turn on FM2/3/6/7/10.

- Use Filter module "C1ALS-OFFSETTER2" to give the ALS sweep. I used FM1 (30mHz LPF). Change the offset while looking at the IR TRY and POY11 error signal.

- Once the resonance is found, shift the beat note by giving +10 or -10 offset.

[PRMI]

- While the arm is kept off resonance, align PRM.

- Lock PRMI with REFL33I and AS55Q. Turn on PRM ASC.

- Once the stable lock is obtained, switch the input signals to REFL165I&Q. I used REF33I x1.0->REFL165I x0.8 and AS55Q x1.0 -> REFL165Q x0.5

[PRMI + one arm]

- Revert the ALS offset by 10 to bring the arm on the resonance the see what happens.

Alex and Steve,

Old halogen chamber illuminator cabling disconnected and potenciometer board removed at 1Y1 in order to give room for pd calibration fibre set up.

 During the process, they had also removed the power cable to the ITMY camera. Steve and I fixed this...so the camera is back.

I went out on the floor to look at the transmitted signal from the PMC to get a rough idea of the noise of the unstabilized laser. There was already a scope hooked up so I just used the measurement features to find the following:

Signal average = 875 mV.  Peak-to-Peak noise = 45 mV

Assuming the noise can be approximated as Gaussian noise, the heuristic for converting to RMS noise of the signal is RMS = Peak-to-Peak / 8 (or Peak-to-Peak / 6, I've used both...)

-> RMS Noise ~ 6.5 mV

When designing my filtering stages and RMS detection/triggering, I'll use relative RMS, i.e. 6 mV / 875 mV = 0.007, as a measure of unstabilized laser noise.

 Here is the list of automations that we need to work on for less hectic PRMI+ALS trials.

1. Enable/Disable ASC when PRMI is locked/unlocked.

2. Smooth transfer from REFL33/AS55 to REFL165 when PRMI is locked.

3. Change actuation from the ITMs to BS and PRM after PRMI lock.

4. Enable ALS.

5. IR resonance scan using ALS.

It would be better to measure the power spectrum density of the fluctuation.
The RMS does not tell enough information how the servo should be.
In deed, the power spctrum density gives you how much the RMS is in the entire or a specific frequency range.

I wanted the RMS noise simply to establish a very rough estimate of thresholds on RMS detectors that will be part of my device. If you refer to elog 8830, I explain it there. Essentially, when the ISS is first engaged, only one of the 2 or 3 filter stages will be active. Internal RMS threshold detection serves to create a logic input to switch subsequent filters to their 'on' stage.

These are the data, one plot for when the vertical QPD position was changed, and one for when the horizontal (yaw) QPD position was changed. 

The micrometer is in inches, so 1 unit is 0.1 inches, I believe.

Clearly, I need to redo the measurement and take more data in the linear region.

[Annalisa, Koji, Manasa]

In order to improve the ALS stability we went ahead to check if we are limited by the sensor noise of ALS.

What we did:
RF signals similar to the beatnote were given at the RF inputs of the beatbox.
The frequency of the RF signal was set such that I_OUT was zero (zero-crossing point of the beatbox).
We measured the noise spectrum of the phase tracker output.

Measurements:
Plot 1: X ALS noise spectrum
Plot 2: Y ALS noise spectrum

Discussion:
The X arm ALS noise is not limited by the sensor noise...which means we shoudl come up with clever ideas to hunt for other noise sources.
But this does not seem to be the case for the Y arm ALS. The Y arm part of the beatbox is noisy for frequencies < 100Hz.

After looking into the details and comparing the X and Y arm parts of beatbox, it looks that amplitude of the beat signal seem to affect the Y arm ALS noise significantly and changes the noise spectrum.

To do:
Investigate the effect/limitations of amplitude of the beatnote on the X arm and Y arm beatbox.

I started doing a scan of the Y arm cavity with IR with ALS enabled.

ALS servo tuning:

The servo tuning procedure is basically the same as described in elog 8831.

This time I had a stronger beat note(-14 dBm instead of -24 dBm of the last measurement) thanks to a better alignment.

Plot1 shows the Power spectrum of the BEATY_PHASE_OUT. The RMS is smaller by a factor of 2 (400Hz), corresponding to a residual motion of about 25 pm.

Offset setting avity scan

In order to give an offset linearly growing in time, I used the ezcastep script instead of giving the offset in OFFSETTER2. If the ramp time is long enough, it is not necessary to enable the 30mHz filter.

To span 2 FSR, I started from an offset of 450 and I gave a maximum value of 1600 with a delay of 0.2s between two consecutive steps.

Cavity scan

I did a first scan with the cavity well aligned, basically to know the position of the 00 peaks and choose the best offset range (Plot2)

Then I misaligned the TT2, first in PITCH and yhen in YAW, in order to enhance the HOMs. (Plot3 and Plot4)

More investigation and measurements needed. 

Annalisa notified me that the MC autolocker could not keep the MC locked.

I found the initial alignment was not good and the MC was too much excited when the WFS kicked in.

There might have been the WFS offset issue due to the miscentering of the spots on the WFS diodes.

I used the usual procedure of the maintenance and it looked OK if I followed the switching procedure the mc autolocker suppoed to do.
http://nodus.ligo.caltech.edu:8080/40m/7452

I still could not get the autolocker running smoothly. I opened mcup script and compared what was the difference
between my manual sequence and what the script did. The only difference was the lines related to MCL.
It was still turning on the filter module. I checked the MCL path and found that the gain was not zero but 1.0.
So now the MCL gain is set to zero. This solved all the remaining issue.

Yesterday evening Nic and me were in the lab. The Mode Cleaner was unlocked, but after many attempt we could fix it and we did many scans of the Y arm cavity.

Today I was not able to keep the MC locked. Koji helped me remotely, and eventually the MC locked back, but after half an hour of measurements I had to stop.

I made some more scan of the Y arm though. I also tried to do the same for the X arm, but the MC unlocked before the measurement was finished. I'll try to come back in the night.

 Summary:

I measured the maximum output of the DAC at 1Y4 as well as its power spectrum. The results are as follows (plots below):

• Maximum amplitude of differential output: + 10V.
• Power spectrum has a peak at 64 kHz.

Therefore, the gain of the high-voltage amplification stage on the PZT driver boards do not need to be changed again, as the required output range of 0-100V from the DAC board was realised when the input voltage ranged from -10V to +10 V w.r.t ground. The AI board converts the differential input to a single ended output as required by the driver board.

I will now change some resistors/capacitors on the AI board such that the position of the notches can be moved from 16k and 32k to 64k and 128k.

Procedure:

 Max. amplitude measurement

My previous measurement of the maximum output amplitude of the DAC was flawed as I made the measurement using a single channel of the oscilloscope, which meant that the negative pin of the DAC channel under test was driven to ground. I redid the measurement to avoid this problem. The set up this time was as follows:

• Positive pin of DAC connected to channel 1 of oscilloscope using break out cable and mini-grabber probe
• Negative pin of DAC connected to channel 2 of oscilloscope
• Grounds of channels 1 and 2 connected (I just hooked the mini-grabbers together)
• Measurement mode on oscilloscope set to channel 1 - channel2
• Used excitation points set up earlier to output a 3 Hz sine wave with amplitude of 32000 counts from channel 9 of the DAC. 

The trace on the oscilloscope is shown below;

So with reference to ground, the DAC is capable of supplying voltages in the range [-10V 10V]. This next image shows all three traces: positive and negative pins of DAC w.r.t ground, and the difference between the two.

 Power spectrum measurement

I used the SR785 to make the measurement. The set up was as follows:

• Positive pin of DAC to A-input of SR560
• Negative pin of DAC to B-input of SR560
• A-B output to Channel 1 input A of the SR785
• SR785 configured to power spectrum measurement

Initially, I output no signal to the DAC, and obtained the following power spectrum. The peak at 65.554 kHz is marked.

I then re-did the measurement with a 200 Hz (left) and 2000 Hz(right), 1000 counts amplitude (I had to change the Ch1 input range on the SR785 from -18dBm to -6dBm) sine wave from channel 9 of the DAC, and obtained the following. The peaks at ~64 kHz are marked.

Now that this peak has been verified, I will work on switching out the appropriate resistors/capacitors on the AI board to move the notches from 16k and 32k to 64k and 128k. 

We need the unit of the voltage power spectrum density to be V/sqrt(Hz).
Otherwise we don't understand anything / any number from the plot.

 Pumpdown 75, vacuum normal condition at day 144

 I redid the measurement with the appropriate units set on the SR785. Power spectral density plots for no output (top), 500Hz, 1000 counts amplitude sine wave (middle) and 2000Hz, 1000 counts amplitude (bottom) are attached, with the right unit on the Y-axis.

 [Eric Alex]

We are planning on testing our laser module soon, so we have added aluminum foil and a safety announcement to the door of OMC North. The safety announcement is as pictured in the attachment.

 [Eric, Alex]

We are planning to add our reference PD to the southern third of the AS Table as pictured in the attachment. The power supply will go under the table.

I tried to retake POP QPD calibration data again today.  The MC was mostly fine, but whenever the PRMI unlocked, both ITM watchdogs would trip.  I'm not sure what was causing this, but the ITM alignment wasn't perfect after this kind of event, so I felt like I was continuously locking and realigning the arms to get the alignment back.   Then, after turning on the ASC and tweaking up the PRM alignment for maximum POP110I signal, I had to recenter the QPD, so none of my previously taken data was useful.  Frustrating.  Also, I had recentered the PRMI-relevant oplevs, but I had these weird locklosses even with nicely centered oplevs.

I have given up for the daytime, and will come back to it if there's a spot in the evening when arm measurements aren't going on.

Here is the data from last week, and the data from today.  The micrometer readings have been calibrated into mm, and I have fit a line to the linear-looking region.  Obviously, for the Pitch calibration, I definitely need to take more data.