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ID Date Author Type Category Subject
  10172   Thu Jul 10 01:02:13 2014 ranaUpdatePSLmore PMC science

Increased gain and SNR in PMC LO monitor circuit.

  1. R20: 499 -> 50k Ohms (increases gain by 100)
  2. Used Marconi to drive the LO input and readout C1:PSL-PMC_LODET
  3. Fit this function and loaded it into the psl.db file. The old Kalmus way used LOGE, but I wanted to use log10, so I did. The sensor is only useful in a narrow band. Since the signal is so low at low levels, I just fit to the highest 4 points because I was too lazy to do proper weighting. Do as I say, not as I do.

Plot with data and fit attached.

** N.B.: in order to update the calibration without rebooting, I used the following command: z write C1:PSL-PMC_LOCALC.CALC "2.235*LOG(B)+12.265". This allows us to update EPICS CALC records without rebooting the IOC.

Attachment 1: PMCloCal.pdf
PMCloCal.pdf
  10171   Thu Jul 10 00:38:20 2014 manasaUpdateGeneralAOM and PSL Ringdown

Quote:

RXA: some more comments...

  1. The fact that the AOM can only modulate the power by a tiny bit means that it is very mis-aligned or that the driver is broken.
  2. You need to take into account the AOM step time in the calculation of the PMC step time. Its not a step response if the input step is not a step, but a exponential.
  3. I wouldn't trust that old John Miller entry for the PMC Finesse. As you can see from his elog, even he didn't trust it.
  4. As we were discussing before, making a little step is not the same as a full ringdown. cf. G000413 and T900007

 

I think we should revisit the AOM alignment because the last time it was aligned, PMC trans dropped from 0.84 to 0.15 (a little more than 80%) for 0-1V modulation input to the AOM driver [elog]. The drop in power right now is ~10-15% only.

I could not find any elogs of AOM alignment touchups after Oct 2012.
But can the ISS team throw some light on the status of AOM when they were installing the ISS servo before we decide on touching the AOM alignment? [elog

  10170   Wed Jul 9 23:02:33 2014 HarryUpdateGeneralBeam Waists via Beamscan

 Today, I borrowed the beam profiler from Brian (another SURF) in order to double check my razor blade measurement figures, using the below setup:

beamscanSetup.png

Measurements are included in the a la mode code that is attached entitled beamfit.m. The beam fitting application yielded me waists (after the lens) of 35.44 um in the x plane, and 33.26 um in the y plane. These are both within 3 um of the measurements I found using the razor blade method. (I moved and resized the labels for the waists in the figure below for readability purposes.)

beamScanWaists.png

I then plugged these waists back into ALM, in addition to the lens specifications, to determine waist size and location of the NPRO, which turned out to be 543 um in the x located at Z = 1.160m, and 536 um in the y, located at 1.268m. These measurements are based upon zero at the waist after the lens, and the positive direction being back toward the NPRO.

beamProfileX.pngbeamProfileY.png

The only systemic difference between these measurement and my original razor blade measurements was that I had taken the focal length of the lens as 75mm, which is advertised on the manufacturer's site. However, the more detailed specs revealed that the focal length was 85.8mm at 1064nm, which made a difference of about 400 um for the final waist determination.

Attachment 4: beamScanWaist.zip
  10169   Wed Jul 9 21:43:41 2014 JenneUpdateElectronicsPMC servo card modifications in DCC

[Rana, Jenne]

We have decided to keep better track (using new-fangled digital "computers") of our modifications to electronics boards. 

The idea will be to create a new DCC document for every electronics board (when we pull a board and modify it, it should receive this treatment) that we have, and that document will become a history of the board's life.  Version 1 will be a copy of the original drawing.  Version 2 should be a modified version of that drawing with the current situation.  All future versions should be modified from the most recent version, to reflect any changes.  Notes for each updated version should include an elog reference to the work, so that we know why we did things, and have a place to find photos of the actual modifications.  Elogs should also include a link to the DCC version.  DCC titles should include the phrase "40m Revisions" for ease of searching.

Patient Zero for this new system will be the PMC servo card.  The DCC number is D1400221.  As of this moment, this just has the V1 original drawing with no modifications.

This has been included in the 40m's DCC document tree that Jamie started back in November 2012.

  10168   Wed Jul 9 21:05:31 2014 manasaUpdateGeneralAOM and PSL Ringdown

After the fits, here are the numbers!

Component Measured Expected
AOM 85.1 ns 200 ns (spec sheet) 
PMC 164.6 ns  Finesse/(2*pi*FSR)  = 163.4 ns

* We have a huge difference to the AOM switching time that was measured. The spec sheet mentions acoustic velocity in the material to be 4.2 mm/us and the well matched diameter in the AOM to be 1100 um. This would give a switching time ~ 200 ns. We could probably be having a much smaller beam size in the AOM for the measured switching time.

* The PMC  parameters that I had been referring to from the wiki were actually wrong and which was the reason for the mismatch that I was finding. I modified the wiki according to the found references to the actual measurement here: PMC parameters The measured values now and then match pretty well.

* Since the AOM does not change the power of the output beam by very much, what we see is actually a step response. Also, we have a lot of noise in the data obtained at the PD. 

RXA: some more comments...

  1. The fact that the AOM can only modulate the power by a tiny bit means that it is very mis-aligned or that the driver is broken.
  2. You need to take into account the AOM step time in the calculation of the PMC step time. Its not a step response if the input step is not a step, but a exponential.
  3. I wouldn't trust that old John Miller entry for the PMC Finesse. As you can see from his elog, even he didn't trust it.
  4. As we were discussing before, making a little step is not the same as a full ringdown. cf. G000413 and T900007

 

Attachment 1: data_code.zip
Attachment 2: PSL_ringFit.pdf
PSL_ringFit.pdf
Attachment 3: AOMringFit.pdf
AOMringFit.pdf
  10167   Wed Jul 9 19:53:34 2014 ranaUpdatePSLPMC LO monitor trend (5 years)

LODET.png

The first step is

The second uptick (In Nov 14, 2013) is when I removed a 3 dB attenuator from the LO line. Don't know why the decay accelerates after that.

  10166   Wed Jul 9 17:34:11 2014 NichinUpdateElectronicsPDFR: Beam pointing adjustments and DC measurements

 [Nichin, Manasa]

AIM: Taking DC output readings with multimeter for each PD to create a database (required for transimpedance calculations), by taking off the table tops. Also, making sure each PD is illuminated properly.

What we did:

  • In rack 1Y1: Diode laser controller was set to 150.0 mA at all times. This gave powers in the neighbourhood of 1mW at the end of fibers illuminating all PDs. The laser outputs light of 1064nm wavelength. The laser was switched off in the end.
  • Checked the collimation of the fiber for each PD. In some cases they were not focused to give a sharp spot, so we had to unmount the fibers and fix it and mount them back. Manasa did it initially and I learnt how it was done properly. Eventually I got better and did it myself (under her supervision)
  • Set the mount alignment for maximum illumination of the PD.
  • Record the power falling on the laser and also the DC voltage output. Any light that did not come from my fiber was blocked when taking the readings and then unblocked. I also took care of offset voltage present when taking the DC readings.

Recorded measurements:

REFL11:   Pinc = 0.91 mW         VDC = 34.9 mV 

REFL33:   Pinc = 0.83 mW         VDC = 33.2 mV 

REFL55:   Pinc = 1.08 mW         VDC = 42.7 mV 

REFL165: Pinc = 0.79 mW         VDC = 115.3 mV

AS55:         Pinc = 0.78 mW         VDC = 31.3 mV

POX11:      Pinc = 0.83 mW         VDC = 34.7 mV

POP22**:   Pinc = 1.08 mW         VDC = 5.82 mV

POY11:      Not illuminated; there was no optical fiber mount. Although, there was a fiber near it with a cap on the end. It also looks like there is no space to put in a new mount near the PD. 

REF PD:    Pinc = 1.19 mW         VDC = 8.2 V     (REF PD = New focus 1611)

**Note: The current POP 22 PD does not have 2 different outputs for DC and RF signals. I unplugged the RF cable from the output, took readings with the multimeter and then plugged back the RF cable.

Further work:

I will calculate the responsivity for each PD and compare it to the expected values. 

  10165   Wed Jul 9 17:08:29 2014 JenneUpdateCDSc1auxex "Unknown Host"

c1auxex has forgotten who it is.  Slow sliders for the QPD head were not responding, so I did a soft reboot from telnet. The machine didn't come back, so I plugged the RJ45-DB9 cable into the machine and looked at it through a minicom session.  When I key the crate, it gives me an error that it can't load a file, with the error code 0x320001.  Looking that up on a List of VxWorks error codes, I see that it is:    S_hostLib_UNKNOWN_HOST (3276801 or 0x320001)

I'm not sure how this happened.  I unplugged and replugged in the ethernet cable on the computer, but that didn't help.  Rana is going in to wiggle the other end of the ethernet cable, in case that's the problem.  EDIT:  Replacing the ethernet cable did not help.

Former elogs that are useful:  10025, 10015

EDIT:  The actual error message is:

boot device          : ei                                                      
processor number     : 0                                                       
host name            : chiara                                                  
file name            : /cvs/cds/vw/mv162-262-16M/vxWorks                       
inet on ethernet (e) : 192.168.113.59:ffffff00                                 
host inet (h)        : 192.168.113.104                                         
user (u)             : controls                                                
flags (f)            : 0x0                                                     
target name (tn)     : c1auxex                                                 
startup script (s)   : /cvs/cds/caltech/target/c1auxex/startup.cmd             
                                                                               
Attaching network interface ei0... done.                                       
Attaching network interface lo0... done.                                       
Loading...                                                                     
Error loading file: errno = 0x320001.                                          
Can't load boot file!! 

  10164   Wed Jul 9 16:33:05 2014 manasaUpdatePSLPMC ringdown setup

Quote:

Quote:

I moved stuff on the PSL table to accommodate the PMC ringdown setup.

I used the beam that leaks from the steering mirror at the PMC transmission that was dumped to a razor blade dump. I installed a Y1 to steer the beam to the ringdown PD. Power in the beam 75mW. 

 I am guessing that 75 mW will burn / destroy any Thorlabs PD. I hope that mW is supposed to be uW.

 It was ~7.5mW and measured ~2V at the PD output (given its range 0-5V ) on the oscilloscope . So PD is safe !

  10163   Wed Jul 9 12:01:43 2014 AkhilConfigurationElectronicsSetup Plan for placing the Frequency Counter inside the lab

Today, me and Manasa went inside the lab to figure out a place for the place for the FC. The whole setup will be placed in a chassis box . The chassis in figure(setupforFC.pdf) will be placed in the highlighted(red) box in the figure(setup.png). All the cables will be routed to the computers from behind the box and the RF cables from the beat box will be routed from the front end of the box. The two raspberry Pi boxes will be placed inside the box and the Frequency counters will be mounted as shown so that the frequency count can be seen from outside. 

Attachment 1: setup.png
setup.png
Attachment 2: SetupFC.png
SetupFC.png
  10162   Wed Jul 9 11:41:12 2014 KoushikUpdatePSLPMC local oscillator is going wonky

Quote:

Koushik replaced an ERA-5 in the PC path. We put the module back to the rack and found no change.
The epics LO level monitor monitor is still fluctuating from 6~11dBm. We need more thorough investigation
by tracing the signals everywhere on the board.

Despite the poor situation of the modulation, PMC was locking (~9PM). Rana suspect that the PMC demodulation
phase was not correctly adjusted long time. 

Koushik has the measured power levels and the photos of the board. I'll ask him to report on them.

 Updates from Koushik:

The power levels measured (before and after relacement of ERA-5) are as follows:

LO to Servo : Vout = 2.3 Vpp / Pout = 11.21 dBm at f = 35.5 MHz

RF to PC   :   Vout = 354 mVpp / Pout = -5.1 dBm at f= 35.5 MHz

The measurements were done using an oscilloscope with 50 ohms load impedance. Unfortunately the photos are not available from the camera.

  10161   Wed Jul 9 08:50:30 2014 AkhilUpdateGeneralWeekly Update

 

Last Week's Work:

  • Worked on the setup to mitigate timing issues arising due to the non-synchronization of clocks of the Frequency counter and Raspberry Pi .
  • Took measurements with the mentioned setup and generated PSD plots of the FC.
  • Completed the setup for phase measurements by using an external ADC.

 

Work Plan for this Week:

  • Complete the installation of the Mini Circuits Frequency Counter on the EPICS. This involves installation of EPICS base on Raspberry Pi, creating an IOC server on the R Pi and writing the data from the FC into a specific IOC  channel. 
  • Complete phase measurements and obtain the delay in the FC thus completing the characterization of the FC.
  • Install the FC at a suitable place inside the 40m so that the beat note system can be remotely managed from any of the Control computers thus effectively replacing the spectrum analyzer(This will be done with proper supervision once the recently ordered FC is shipped)

 

Inside the 40m :

  • I will be going inside the lab today around 9 am with Manasa to make a plan about where the FC must be placed and the routing of the RF cables and the cables which run  into computers from the FC.
  • Once the channel is created and tested, we will install the FC inside the lab possibly by the end of this week or by next week.
  10160   Wed Jul 9 00:59:09 2014 ranaUpdatePSLPMC local oscillator is going wonky

Quote:

Koushik and Koji try to fix the PMC oscillator issue. So we remove the module from the rack.
This means we don't have the PMC transmission during the work.

 After the ERA-5 was replaced (see Koushik elog) we relocked the PMC.

The new LO level going into the PMC servo card is +11.5 dBm. The LO mon on the PMC card reads 9 dBm and seems so flat I now suspect the monitor circuit.

I also measured the RF drive to the EOM as a function of C1:PSL-PMC_RFADJ on the Phase Shifter screen.

The phase shifter slider gives ~75 deg/V in phase shift of the RF out to the EOM. I tried to optimize the loop gain quickly using the fluctuations in the reflected power. The loop oscillates at high frequency with the slider at 21 dB and also at 9 dB. So I set the gain at +14 dB. Needs to be optimized correctly in the daytime.

 

Attachment 1: PMC_RFslider.pdf
PMC_RFslider.pdf
  10159   Wed Jul 9 00:47:22 2014 KojiUpdatePSLPMC local oscillator is going wonky

Koushik replaced an ERA-5 in the PC path. We put the module back to the rack and found no change.
The epics LO level monitor monitor is still fluctuating from 6~11dBm. We need more thorough investigation
by tracing the signals everywhere on the board.

Despite the poor situation of the modulation, PMC was locking (~9PM). Rana suspect that the PMC demodulation
phase was not correctly adjusted long time. 

Koushik has the measured power levels and the photos of the board. I'll ask him to report on them.

  10158   Tue Jul 8 23:59:49 2014 HarryUpdateGeneralWeekly Plan (7.8.14)

 Last Week:

-I continued to struggle with the razorblade beam analysis, though after a sixth round of measurements, and a lot of fiddling around with fit parameters in matlab, there seems to be a light at the end of the tunnel.

 

Next Week:

-I plan to check my work with the beamscan tomorrow (wednesday) morning

-Further characterize the light from the fibers, and set up the collimator

-Design and hopefully construct the telescope that will focus the beam into the collimator

 

Materials:

- Razorblade setup or beamscan (preferably beamscan)

- Fiber Illuminator

- Collimator (soon to be ordered)

- Lenses for telescope (TBD)

 

  10157   Tue Jul 8 22:53:02 2014 Jenne, RanaUpdateElectronicsTransmon QPD / whitening

We need to work farther on checking out the end transmission QPD electronics situation. 

In bullet-point form, we need to:

* Ensure that the Weiss QPD head modifications have been made on these diodes.  (cf. Rai W's LLO elogs on QPDs)

* Ensure that the QPD biases are somewhere in the range of 10-15V, not the old 100V.  (Because we only need HV to make the capacitance low for RF use. Low voltage means less power dissipation in the head)

* Ensure the Rana/Rob modifications have been propagated to the whitening boards, so that we have full dynamic range.  (Steve is looking for the marked up paper schematics)

* Replace signal path resistors with low noise metal film resistors.

* Check QPDs / whitening boards for oscillation (with a scope probe), ensure that we chose an appropriate analog gain.

 

In thinking about the transimpedances that we want, we thought about the current that we expect.  We should get about 100 mW of light transmitted through the ETMs when we have full IFO lock.  There is a 50/50 BS to split the light between the QPD and the Thorlabs transmission diode, so we have about 50 mW incident on the QPDs, which is about 13 mW per quadrant.  With a sensitivity of about 0.15 Amps/Watt for silicon, this means that we're expecting to see about 2 mA of current per quadrant once we have the IFO fully resonant. We want this to correspond to about 5V, which means we want a transimpedance gain of around 2.5 kOhm. 

 

For the things that need checking, each quadrant has:

Photodiode  ------  Gain Switch 1 ----- Gain Switch 2  ------ Gain Switch 3 ------ Variable Gain Amplifier ------- Whitening stage 1 (z @ 4 Hz, p @ 40 Hz)  ------- Whitening stage 2 (z @ 4 Hz, p @ 40 Hz)

We want to check on the status of each of these switches, and whether they actually do what they say on the QPD Head screens.  Q has checked out and fixed the bit outputs for the whitening stages, but the rest still needs to be checked out.  Also note that the Switch 1, Switch 2 and Switch 3 are common to all 4 quadrants (i.e. enabling switch 1 on one quadrant enables it on all quadrants), but the variable gains and the whitening stages are individual for each quadrant.

  10156   Tue Jul 8 18:20:15 2014 jamieOmnistructureElectronicsJamie 1811 power supply fixed!

 Placed in PD cabinet in Y arm, next to the OTHER Jamie-made 1811 power supply from 1998.

  10155   Tue Jul 8 17:59:12 2014 jamieOmnistructureElectronicsJamie 1811 power supply fixed!

I finally made good on the LIFE TIME WARRANTY on the ancient, Jamie-made 1811 power supply with the faulty switch:

20140708_165010.jpg

Back to fully working form.  Hopefully I'll still be around the next time it breaks in 16 years.

  10154   Tue Jul 8 16:45:15 2014 NichinUpdateGeneralWeekly plan

 My plan for next week is...

1)    1) Taking DC output readings with multimeter for each PD to create a database for all the PDs. Requires taking off the table tops for each PD.  Also, making sure each PD is illuminated properly.

    2 - 3 Hours inside the lab 

    Requires presence of expert

Occupies all the PDs , RF switch and the Network analyzer.

2)    2)  Integrate the switch selection script with the Network analyzer script to complete the automation part of the project.  (If time permits, build a simple GUI for easy operation)

Occupies the control room computer, RF switch and the Network analyzer

3)    3)  Create a database of canonical plots for each PD to compare with the current plot and maybe even plot the difference between the current plot and canonical plot.

Occupies the control room computer, PDs , RF switch and the Network analyzer.

4)    4)  Fit the transfer function or transimpedance using vector fitting. (vectfit4.m)

5)    5) Update 40m-Wiki

6)    6) Progress Report to be submitted to SFP.

  10153   Tue Jul 8 15:28:32 2014 KojiUpdatePSLPMC local oscillator is going wonky

Koushik and Koji try to fix the PMC oscillator issue. So we remove the module from the rack.
This means we don't have the PMC transmission during the work.

  10152   Tue Jul 8 15:07:24 2014 NichinHowToElectronicsRF Multiplexer in rack 1Y1

The RF multiplexer is configured as shown in the figure. It is now effectively a 15x1 RF mux.

RF_Multiplexers.png

To select a required channel:

Run the script as shown below 

/opt/rtcds/caltech/c1/scripts/general/rfMux.py

>python rfMux.py ch11

For channel 10 to 16, you can just enter the required channel number and it is routed to the output.

For channel 1 to 8, you only need to input the required channel number as above. No need to run the code again to select ch9 after selecting ch1-8

 

How the NI-8100 controller works:

Whenever any channel of one switch is selected, the output of the other switch is set to its ch0 (ch1 and ch9 in the figure).

So selecting ch1-8 will automatically select ch9 as output for the other switch. IF you send a command to select ch9 afterwards, the first switch will be automatically set to ch1 and not stay on what you had selected before.

  10151   Tue Jul 8 09:02:02 2014 AkhilUpdateElectronicsPSD Plots for different sampling times of the Frequency Counter

 Although there were few timing issues with the FC and the Raspberry Pi at the lowest sampling time of the FC (0.1s) even after adding an external trigger circuit, it turned out that most of these issues are not prevalent at higher sampling times(>0.5 s)(narrow peaks of PSD seen for higher sampling times). Rana suggested me to look at the PSD plots at different sampling times of the FC so that we can decide which would be the optimal sampling time to work with the FC before replacing the spectrum analyzer. I took the measurements with the setup discussed in my previous elog(http://nodus.ligo.caltech.edu:8080/40m/10129) . However, the  noise of the R Pi- FC interface should be taken care of (I will discuss it with my mentors).

Attached are the plots at 100 MHz carrier frequency at  different sampling times of the FC( 0.1s, 0.2s, 0.3s, 0.5s, 1s) (pdfs and code attached in a zip file)

RXA: Put all the plots in a single PDF file and use the same axis limits for all plots so that its easy to compare.      (Attached in PSD.pdf)


 

 

Attachment 1: 0.1s.png
0.1s.png
Attachment 2: 0.2s.png
0.2s.png
Attachment 3: 0.3s.png
0.3s.png
Attachment 4: 0.5s.png
0.5s.png
Attachment 5: 1s.png
1s.png
Attachment 6: Pdf.zip
Attachment 7: PSD.pdf
PSD.pdf
  10150   Tue Jul 8 01:55:21 2014 JenneUpdateSUSETMX glitching

[Jenne, Rana]

A few times this evening, I had been having trouble locking CARM and DARM with ALS, and holding it for very long.  When it started happening again, I switched over to locking the individual arms with ALS.  Yarm seems to be totally fine, but Xarm has something funny going on. 

Rana and I have narrowed it down to being a problem with ETMX.  We were watching ETMX's oplev and local damping error signals, and would see occasional glitch events.  This happened when oplev + local damping were both on, both off, and when only local damping was on.  We believe that this points to something weird with the coil driver and actuator chain.

We tried to watch for a while to see if it was a step event (something switching on and off periodically), or an impulse event (some transient oscillation in an opamp perhaps), but the problem went away again.  We have come to no conclusions other than we have a problem that needs watching.

During our investigations, to more softly turn off the damping, Rana set the local damping gains, as well as the oplev gains to zero using a ramp time.  We don't recall the precise numbers, and conlog doesn't have the gains recorded, so we made an educated guess.  The local damping seems fine, but the oplev damping should be re-confirmed.  Steve, can you please show Harry how, and have him help you measure the ETMX pitch and yaw oplev loops, and set the gains so that they match up to the references, and then post the measured bode plots when you're done? 

  10149   Mon Jul 7 23:19:55 2014 ranaUpdatePSLPMC ringdown setup

Quote:

I moved stuff on the PSL table to accommodate the PMC ringdown setup.

I used the beam that leaks from the steering mirror at the PMC transmission that was dumped to a razor blade dump. I installed a Y1 to steer the beam to the ringdown PD. Power in the beam 75mW. 

 I am guessing that 75 mW will burn / destroy any Thorlabs PD. I hope that mW is supposed to be uW.

  10148   Mon Jul 7 22:18:26 2014 KojiUpdatePSLPMC local oscillator is going wonky

It seems that there is no better chip in MiniCircuits line-up with the same form factor.
ERA-5 is the most powerful one in the ERA (or MAR) series.

If the output is ~0dBm we have MAR-6SM in stock. But I suspect that ERA-5 was driven at the power level close to its saturation (~18dBm).

If we allow different form factors, we have GVA-** or GALI-** in the market and also in the blue tower, in order to gain more performance margin.
If it is difficult to apply them, I would rather use another ERA-5 with enhanced heat radiation.

I'm sure that Downs has EAR-5 replacement.

  10147   Mon Jul 7 22:07:29 2014 ranaUpdateElectronicsRF cables rerouted

This Red Ladder movement also probably included some bumping of the MC2 stack (be more careful when working in the lab). Around 5 PM today, the MC lost lock.

When I came in later, I found that the MC was flashing the TEM17,9 mode and had been misaligned like this for ~1 hour. I looked through the MC SUS sensor trends and moved MC2 back to its old position to get the locking back. I disabled the WFS, tweaked the TEM00 mode alignment using only MC2 sliders, and then re-enabled WFS. Its been OK for the past 5 hours.

Attachment 1: Untitled.pdf
Untitled.pdf
  10146   Mon Jul 7 21:36:33 2014 Jenne, ranaUpdatePSLPMC local oscillator is going wonky

The PMC local oscillator is going a little weird dyingWe need to check out why the level is fluctuating so much.

Here's a 6 month plot, where you can see that the lower level keeps getting lower (y-axis is dBm):

PMC_LO_failing.pdf

This LHO entry from 2008 shows where we first discovered this effect. As Rick Savage and Paul Schwinberg later found out, the ERA-5SM+ amplifier slowly degrades over several years and was replaced for both of the eLIGO interferometers. We have spares in the Blue box and can replace this sometime during the day.

Our PMC LO is made by this obsolete crystal oscillator circuit: D000419. There are many versions of this floating around, but they all have the ERA-5 issue.

  10145   Mon Jul 7 18:38:27 2014 NichinUpdateElectronicsRF cables rerouted

Quote:

The RF cables have been routed incorrectly. The cables run to the module from the front of the rack. We cannot close the doors to the racks if they are to remain this way.

I have asked Nichin to reroute the cables properly.

RF cables have been rerouted from the side of the rack, under the supervising eye of Manasa.

I moved the red ladder from near 1X4 to 1Y1 and back again.

Current list of RF cables:

REFL11, REFL33, REFL55, REFL165,

AS55

POX11

POP22

POY11

I have not connected them to the RF switch yet. ( until I figure out how to get both the switches working properly)

Attachment 1: 1.png
1.png
Attachment 2: 2.png
2.png
  10144   Mon Jul 7 18:11:04 2014 KojiUpdateGeneralBeam Waists

- Plots should be directly attached on the elog. (Attaching codes in a zip is OK.)

- Plot legends should not touch or hide any data points.

- Don't exclude data points.

- The model for the beam profile fitting is incorrect: zr and w0 are dependent

- The code needs to be reviewed by someone for refinement.
  (
EricQ, or possibly Jamie, Jenne while he is absent).

  10143   Mon Jul 7 17:20:09 2014 NichinUpdateElectronicsRF PDs needed

Quote:

Quote:

 REFL33, AS55, REFL55,REFL165,REFL11,POX11,POP22

There were quite a few more demodulator units labelled with PD names. Do any of them need to be included in the automated frequency response measurement system? Please let me know so that I can include them to the RF switch and check them for proper illumination, which i will do for all the above PDs next week.

 In the order that makes more sense to me, it looks like you have:

REFL11, REFL33, REFL55, REFL165,

AS55

POX11

POP22

We don't really need POP22 right now, although we do want the facility to do both POP22 and POP110 for when we (eventually) put in a better PD there.  Also, we want cabling for POP55, so that we can illuminate it after we re-install it.  If we're working on 2f PDs, we might as well consider AS110 also, although I don't know that there was a fiber layed for it.  The big one that you're missing is POY11.

 A new RF cable has been included for POY11. Cabling for POP55 and POP110 might or might not exist. I will check and report it.

  10142   Mon Jul 7 16:52:02 2014 manasaUpdateElectronicsRF cables need to be rerouted

The RF cables have been routed incorrectly. The cables run to the module from the front of the rack. We cannot close the doors to the racks if they are to remain this way.

I have asked Nichin to reroute the cables properly.

  10141   Mon Jul 7 16:39:26 2014 SteveUpdatePEMants on the PSL table

Quote:

Quote:

We observed one or two ants climbing over PMC optics without booties and safety glasses.

The floor was mopped with strong Bayer Home Pest Control solution in the Vertex area.

Do not work inside the 40m lab if you are sensitive to chemicals!

 

 The floor is mopped again with strong PEST CONTROL SOLUTION in water in the Vertex area.

Do not plane to work in the IFO-room till noon if you are sensitive to chemicals!

 Ants are back on the PSL table. We'll be mopping the floor with pest control solution tomorrow morning.

  10140   Mon Jul 7 16:39:09 2014 manasaUpdatePSLPMC ringdown setup

I moved stuff on the PSL table to accommodate the PMC ringdown setup.

I used the beam that leaks from the steering mirror at the PMC transmission that was dumped to a razor blade dump. I installed a Y1 to steer the beam to the ringdown PD. Power in the beam 75mW.

Results are in here elog 

Attachment 1: PMC_ring.png
PMC_ring.png
  10139   Mon Jul 7 14:42:33 2014 HarryUpdateGeneralBeam Waists

I was finally able to get a reasonable measurement for the beam waist(s) of the spare NPRO.

Methods

I used a razorblade setup, pictured below, to characterize the beam waist of the spare 1064nm NPRO after a lens (PLCX-25.4-38.6-UV-1064) in order to subsequently calculate the overall waist of the beam. The setup is pictured below:

 

RzorbladeSetupFinal.pdf

After many failed attempts, this was the apparatus we (Manasa, Eric Q, Koji, and I) arrived with. The first lens after the laser was installed to focus the laser, because it's true waist was at an inaccessible location. Using the lens as the origin for the Z axis, I was able to determine the waist of the beam after the lens, and then calculate the beam waist of the laser itself using the equation wf = (lambda*f)/(pi*wo) where wf is the waist after the lens, lambda the wavelength of the laser, f the focal legth of the lens (75.0 mm in this case) and wo the waist before the lens.

We put the razorblade, second lens (to focus the beam onto the photodiode (Thorlabs PDA255)), and the PD with two attenuating filters with optical density of 1.0 and 3.0, all on a stage, so that they could be moved as a unit, in order to avoid errors caused by fringing effects caused by the razorblade.

I took measurements at six different locations along the optical axis, in orthogonal cross sections (referred to as X and Y) in case the beam turned to be elliptical, instead of perfectly circular in cross section. These measurements were carried out in 1" increments, starting at 2" from the lens, as measured by the holes in the optical table.

Analysis

Once I had the data, each cross section was fit to V(x) = (.5*Vmax)*(1-erf((sqrt(2)*(x-x0))/wz))+c, which corresponds to the voltage supplied to the PD at a particular location in x (or y, as the case may be). Vmax is the maximum voltage supplied, x0 is an offset in x from zero, wz is the spot size at that location in z, and c is a DC offset (ie the voltage on the PD when the laser is fully eclipsed.) These fits may all be viewed in the attached .zip file.

The spot sizes, extracted as parameters of the previous fits, were then fit to the equation which describes the propagation of the spot radius, w(z) = wo*sqrt(1+((z-b)/zr)^2)+c, w(z) = w0*sqrt(1+((((z-b)*.000001064)^2)/((pi*w0^2)^2))) where wo corresponds to beam waist, b is an offset in the z. Examples of these fits can be viewed in the attached .zip file.

Finally, since the waists given by the fits were the waists after a lens, I used the equation wf = (lambda*f)/(pi*wo), described above, to determine the waist of the beam before the lens.

Plots

 

note: I was not able to open the first measurement in the X plane (Z = 2in). The rest of the plots have been included in the body of the elog, as per Manasa's request.

Y_Waist_Fit.pngY_plane_measurement_6_(Z_7in).pngY_plane_measurement_5_(Z_6in).pngY_plane_measurement_4(Z_5in).pngY_plane_measurement_3_(Z_4in).pngY_plane_measurement_2_(Z_3in).png

 

Y_plane_measurement_1_(Z_2in).png X_plane_measurement_6_(Z_7in).pngX_plane_measurement_5_(Z_6in).pngX_plane_measurement_4_(Z_5in).pngX_plane_measurement_3_(Z_4in).pngX_plane_measurement_2_(Z_3in).pngX_plane_measurement_1_(Z_2in).pngX_Waist_fit.png

Conclusion

The X Waist after the lens (originally yielded from fit parameters) was 90.8 27.99 ± .14 um. The corresponding Y Waist was 106.2 30.22 ± .11 um.

After adjustment for the lens, the X Waist was 279.7 907.5 ± 4.5 um and the Y Waist was 239.2 840.5 ± 3.0 um.

edit: After making changes suggested by koji, these were the new results of the fits.

Attachments

Attached you should be able to find the razor blade schematic, all of the fits, along with code used to generate them, plus the matlab workspace containing all the necessary variables.

NOTE: Rana brought to my attention that my error bars need to be adjusted, which I will do as soon as possible.

Attachment 2: erFitFinal2.zip
  10138   Mon Jul 7 14:38:55 2014 SteveUpdatesafetysafety training

TaraV - geology major undergrad -  of Jenne's summer help received 40m specific basic safety training.

  10137   Mon Jul 7 13:56:13 2014 AkhilConfigurationElectronicsSetup Used for Characterization of Frequency Counter

When I was trying to plot PSD of the measurements, I still couldn't get better resolution. There still seems to be a problem with timing and synchronization of the R Pi with the FC even after addition of the external trigger circuit. Now, I am looking to debug this issue. Attached are the plots showing missing data points and data from the FC at uneven spacing(zoomed in plot).

 

Attachment 1: FreqVsTime.png
FreqVsTime.png
Attachment 2: Missing_Data.png
Missing_Data.png
  10136   Mon Jul 7 13:55:26 2014 JenneUpdateLSCc1cal model restarted

I'm not sure why the c1cal model didn't come up the last time c1lsc was rebooted, but I did an "rtcds start c1cal" on the lsc machine, and it's up and running now.

  10135   Mon Jul 7 13:44:21 2014 JenneUpdateCDSc1sus - bad fb connection

Quote:

 

I managed to recover c1sus.  It required stopping all the models, and the restarting them one-by-one:

$ rtcds stop all     # <-- this does the right to stop all the models with the IOP stopped last, so they will all unload properly.

$ rtcds start iop

$ rtcds start c1sus c1mcs c1rfm

I have no idea why the c1sus models got wedged, or why restarting them in this way fixed the issue.

 In addition to needing obnoxiously regular mxstream restarts, this afternoon the sus machine was doing something slightly differently.  Only 1 fb block per core was red (the mxstream symptom is 3 fb-related blocks are red per core), and restarting the mxstream didn't help.  Anyhow, I was searching through the elog, and this entry to which I'm replying had similar symptoms.  However, by the time I went back to the CDS FE screen, c1sus had regular mxstream symptoms, and an mxstream restart fixed things right up. 

So, I don't know what the issue is or was, nor do I know why it is fixed, but it's fine for now, but I wanted to make a note for the future.

  10134   Mon Jul 7 11:02:22 2014 manasaConfigurationGeneralIFO status post earthquake

Quote:

All suspension damping restored. There had to be an earth quake.

PMC was relocked.

MC did not need any fixing to its alignment. I had to lock it manually and autolocker is set running now. So that should take care of things

The arms were aligned and ASS'd for IR PDH.

Green light PDH locks to the arms alright.

  10133   Mon Jul 7 10:35:43 2014 JenneUpdateElectronicsRF PDs needed

Quote:

 REFL33, AS55, REFL55,REFL165,REFL11,POX11,POP22

There were quite a few more demodulator units labelled with PD names. Do any of them need to be included in the automated frequency response measurement system? Please let me know so that I can include them to the RF switch and check them for proper illumination, which i will do for all the above PDs next week.

 In the order that makes more sense to me, it looks like you have:

REFL11, REFL33, REFL55, REFL165,

AS55

POX11

POP22

We don't really need POP22 right now, although we do want the facility to do both POP22 and POP110 for when we (eventually) put in a better PD there.  Also, we want cabling for POP55, so that we can illuminate it after we re-install it.  If we're working on 2f PDs, we might as well consider AS110 also, although I don't know that there was a fiber layed for it.  The big one that you're missing is POY11.

  10132   Mon Jul 7 09:46:00 2014 SteveConfigurationSUSall sus damping restored

All suspension damping restored. There had to be an earth quake.

Attachment 1: 6.9MagMexico.png
6.9MagMexico.png
  10131   Mon Jul 7 08:13:41 2014 steveUpdateGeneralyes,there was firework
Attachment 1: 8days.png
8days.png
  10130   Sat Jul 5 04:18:45 2014 AndresUpdate40m Xend Table upgradeAdding Two Lenses After the Second Steering Mirror in Order Two Increase the Gouy Phase Difference Between the Sterring Mirrors

I had been working on the Xend table optical layout update. Since the two steering mirrors in the Xend green are too close to each, there is a very small Gouy Phase different between these two mirrors. It was suggested to place two lenses so that we can increase the Gouy Phase. I have been working with Nick on this problem, and we had found a solution by using a la mode. We had written an a la mode code that optimize the Gouy Phase and the Mode Matching at the same time. After trying different lenses, we found the following results: a mode matching of 0.9939 as it is show in the first attachment below, and we found a Gouy Phase different between the two mirrors of about 60 degrees. I took photos of the Xend Table. The first photo is the Xend table as we had it right now. In the second photo, I moved the 2nd lens, and I placed the two more lenses that we need it, with more or lenses the correct position where they will be placed. The three old lenses will be replaced by three lenses of different focal length as it can be seen in the first attachment below. The first lens and third lens will stay in the same position where the old first lens and old third lens are, and the second lens will be moved by about half of an inch. We might have one or two of the lenses that we need, but we will have to order the rest of the lenses that need. My plan is to verify the lenses that we already have. Then, I need to let Nick know with lenses we need to order. Hopefully, we will be able to update the table by the end of this week if everything turn out fine.

Attachment 1: OverlapAndComponentsOfTheSolution.png
OverlapAndComponentsOfTheSolution.png
Attachment 2: CloseLookToTheGouyPhaseBetweenMirr1AndMirr2.jpg
CloseLookToTheGouyPhaseBetweenMirr1AndMirr2.jpg
Attachment 3: EntireRangeOfBeamPath.jpg
EntireRangeOfBeamPath.jpg
Attachment 4: XendTableWithTwoNeedLensesAdding.JPG
XendTableWithTwoNeedLensesAdding.JPG
Attachment 5: SchematicOfSolutionForTheLensesGouyPhase.jpeg
SchematicOfSolutionForTheLensesGouyPhase.jpeg
Attachment 6: XendGreenModeMatchingAndGouyPhaseOptimization.m
clear all
% In this code we are using a la mode to optimatize the mode matching and
% to optimatize the Gouy phase between mirror 1 and mirror 2. All the units
% are in meter

w0=2.943*1e-5; % The Waist of the laser measured before the faraday
z0_laser=-0.039; % position measured where the waist is located 
lamb= 532*10^-9; % wavelength of green light in mm
lFaraday=.0638; % Length of the faraday

... 148 more lines ...
Attachment 7: BeforeIncludingLensesORMovingLenses.JPG
BeforeIncludingLensesORMovingLenses.JPG
  10129   Fri Jul 4 09:17:13 2014 AkhilConfigurationElectronicsSetup Used for Characterization of Frequency Counter

 Goal:

To complete the characterization of the Mini Circuits UFC-6000  RF Frequency Counter to be used for beat note measurement  as a part of frequency offset locking loop. The aim of this setup was to obtain the bode plots and PSD plots for the FC.

Detail about the Setup:

UFC RF Frequency Counter: Described in detail in one of my previous elog (http://nodus.ligo.caltech.edu:8080/40m/10020) 

Raspberry PiRaspberry Pi will be running Raspbian which is a version of Linux, and not a RTOS. When sampling data at a certain frequency we want samples to occur at fixed time intervals corresponding to the sampling period. A normal operating system cannot provide us with this functionality, and there will be jitter (variation) in the time difference between consecutive samples. Whether this is an issue depends on how much jitter we have and what the specific application is. In our application(measuring phase and noise), the jitter has to be taken into consideration. Hence for data acquisition we need  to sample with much more tightly defined sampling periods (reduced jitter) which can be done by providing an external timing standard(Like a square pulse of the frequency same as the sampling rate of the FC ).

ADC : The ADC serves for two different conversion processes in the setup:

            1)  For converting modulating analog signal(from SRS 30 MHz Wave Generator) into digital signal for data analysis on Raspberry Pi.

            2)  To provide an external clock reference to the Raspberry Pi.

Interfacing ADC(ADS1115) with Pi:

Configuring the ADS1115 - Configuration Register

In order to set the modes of operation defined above we must set the config register within the ADS1115. A register is simply a memory location within the chip. Registers are made up of bytes (8 bits) of data. Registers are typically either one or two bytes long. The bits are:

Bit [15] This bit is used to start a conversion, by setting this bit to 1 a conversion is initiated. When reading the config register this bit remains equal to 0 while the conversion is carried out, and is set to 1 once the conversion is complete, we can monitor this bit to find the status of a conversion

Bits [14:12] These bits set which pin to use as input to the ADC. Note that we can choose either single ended or differential mode through setting these bits. Note that each configuration has two inputs AIN~p~ and AIN~n~. By setting AIN~n~ to GND we obtain a single ended input with AIN~p~ as the input.

Bits [11:9] These bits set which setting of the programmable gain amplifier to use

Bit [8] Continuous conversion / No Continuous conversion

Bits [7:5] Set the samples per second (sps) value

Bit [4:2] Comparator setup, we will not use the comparator so these bits are irrelevant

Bit [1:0] Comparator mode, set to 11 to disable the comparator.

 Four channels are used in differential mode for A-D conversion of two analog signals, one the slow modulating signal input and the other for a square signal of 10 Hz (same as sampling rate of FC(0.1 s)).

The raspberry Pi reads the external trigger from ADC and starts reading input from the FC only when the square signal is 1. Thus in this way we can avoid the clock jitter and timing can be as accurate as the RTOS.

Function Generators:

Three function generators are used in the setup:

  1. IFR Marconi Generator used for RF Carrier signal.
  2. SRS 30 MHz Function Generator used for slow modulating signal (upto 5Hz).
  3. SRS 30 MHz signal for square wave used as clock(10 Hz).

 The setup is attached as pdf. The computer scripts will follow this elog.

Measurements Taken:

The input and output modulated signals are recorded and the delay and noise of the FC are to be estimated.

 

 

 

 

Attachment 1: setup.pdf
setup.pdf
  10128   Thu Jul 3 16:28:38 2014 NichinUpdateElectronicsRF cables installed

 [ Nichin, Eric G]

RF cables have been installed between deomodulator output PD RF MON and the RF switch for the following PDs:

 REFL33, AS55, REFL55,REFL165,REFL11,POX11,POP22

The cables are labelled on both ends and have been run on the overhead tray.

The cabling looks neat on 1Y2, but not so much in 1Y1(RF switch). I will better organize them later.

There were quite a few more demodulator units labelled with PD names. Do any of them need to be included in the automated frequency response measurement system? Please let me know so that I can include them to the RF switch and check them for proper illumination, which i will do for all the above PDs next week.

Test run:

I tested the RF switch selection code and then the data acquisition code for the NWAG4395A network analyzer and they both seemed to work fine. I selected the channel to which AS55 is hooked up to and then remotely got its transfer function.

There is quite some noise in the system as the plot shows. Especially the phase. Maybe my driving power was a bit too low. Have to figure out the reason behind this.

Further work:

  • Make sure all the PDs are properly illuminated.
  • Create a DC voltage reading's database for all PDs.
  • Canonical plots for each PD to compare with the current data.
  • Implement a script to fit the transfer function and extract required information about the PD.

 

 

 

Attachment 1: AS55_03-07-2014_162634.pdf
AS55_03-07-2014_162634.pdf
  10126   Wed Jul 2 22:58:11 2014 JenneUpdateLSCLittle Bo-Peep has found her phase

Never mind.  This is just the low pass filter that Den put in to try to deal with the moving cavity pole. 

Before I realized this, just in case it was a computer quirk, Koji and I rebooted the end station front end machines.  This had no effect other than to keep me searching and measuring until I figured it out.  If I turn off the low pass, the phase pops back up to very close to the reference.  The low pass currently comes on automatically as part of the carm_cm_up script.

  10125   Wed Jul 2 21:30:42 2014 JenneUpdateLSCLittle Bo-Peep has lost her phase
Little Bo-Peep has lost her phase,
And can't tell where to find it;
Leave it alone, and it'll come home,
Bringing its degrees behind it.
 
Seriously.  What?  I was holding CARM on sqrtTrans with arm powers of about 1, DARM was still ALS diff, PRMI on REFL33.  CARM was actuating on +ETMX+ETMX, since I kept kicking the MC out of lock, but other than that, everything was set by the carm_cm_up script, so I don't think there should be any big differences.  I took a CARM transfer function, and it seems like the phase bubble has all but disappeared compared to the reference from mid-May. 

CARM_loop_ArmPowers1_2July2014.pdf

I need to figure this out before it's worth trying any acrobatic AO path turn-on scenarios.

 

Also this evening, I went to the Yend and did another tweak-up of the green beam alignment. 

  10124   Wed Jul 2 16:18:32 2014 JenneUpdateASCIFO aligned, PRMI + 2 arms achieved

After the meeting, I aligned the IFO to the IR, and then I aligned the Ygreen to the Yarm.  I then found the beatnotes and used ALS to hold the arms with CARM/DARM, locked the PRMI, and reduced the CARM offset until I had arm powers of about 3.  Given that this was at 3pm, and people were tromping all over inside the IFO room, I feel positive about tonight.  

So, IFO seems ready, carm_cm_up script was successful, and got me to arm powers of 1, and then I further reduced the offset by a bit to go a little higher. 

  10123   Wed Jul 2 16:16:45 2014 NichinUpdateGeneralLAN wire added

 [Nichin, Eric Q]

We added a new LAN wire from Rack 1Y4 to 1Y1 to connect the RF switch at 1Y1 to the martian network. The wire is labelled "To RF Switch (1Y1)"

The wire was run along the Y arm in the tray right next to the vaccum chamber, not the one on top.

 

  10122   Wed Jul 2 15:35:34 2014 ericqUpdateComputer Scripts / ProgramsLocal Chiara backups

Koji has provided a 2TB USB3 external hard drive that will get daily backups of chiara:/home/cds, the idea being that if the internal HD at /dev/sdb1 fails, we can physically open the external up, and swap the hard drive into chiara. 

We're running an rsync job on it right now, which should be done in a few hours. (USB3 is fast!)

I've also written a backup script at scripts/backup/rsync_chiara.backup which keeps its books in scripts/backup/rsync_chiara.backup.log 

I'm adding a entry to the root crontab on chiara to execute the script every day at 7am. 

 

ELOG V3.1.3-