Since the measurement is not done yet, I asked Jeff to give me the model of the TF from PUM to the test mass angle to angle.
Since I don't know enough about the model, I made the model generate the TF data, and used my wrapper for vectfit3 named happyVectfit to fit the model TF and invert it. This way when the real TF is measured I can use the same script without much modification.
You want to give happyVectfit a large order of fit, which initially produces many useless poles and zeros, but the script weeds out useless ones automatically, making things almost always hands-free. If you want you can give the script some criteria regarding what poles/zeros are useless.
~controls/keita.kawabe/fit/invertPUM2TSTmodel.m looks at the model, calls happyVectfit, inverts the fit, discards unstable poles and outputs plots (attached) as well as foton-compatible filter definitions.
In the attached plots, each DOF for each mass has two pages, the first one being the model TF and the fit, the second one being the filter generated and the residual that is just a pendular type TF. The difference between ITM and ETM is wire VS fiber.
According to Jeff the PIT resonance of the model is inconsistent with reality so we still need to wait for the real measurement.
Just to make sure, the newly generated filters are put in H1:SUS-ITMX_L2_DRIVEALIGN_P2P, Y2Y, ETMX P2P and Y2Y as invP2P and invY2Y.
In the plots showing the model and the fit, legend say "fit*roll off" but actually the plot doesn't include the roll off filter.
Here is the list of commissioning task for the next 7-14 days:
Green team:
Red team:
Blue team (ALS WFS):
Blue team (ISCTEY):
TMS:
SEI/SUS team:
Kiwamu, Yuta, Stefan Since all our OLG functions in PRMI never really made any sense, we locked PRY and carefully measured the actuation functions from BS to REFL_45_I and from PRM to REFL_45_I. Plot 1 shows both BS and PRM transfer functions in ctsREFL45 / cts ISCinf drive (i.e. total actuation function). Both are closed loop corrected. The BS makes sense: it is almost 1/f^2. I don't understand the PRM - need to sleep over it. Plot 2 shows the OLG and the CLG. Plot 3 is a snapshot of (almost) all relevant settings. The data is in ~controls/sballmer/20140302: BSdrive.xml PRMdrive.xml data/BS2REFL_mag_rad.txt data/PRM2REFL_mag_rad.txt data/plotIt.m To do next: -Understand PRM: for one we should check that the acquire mode TF of PRM M3 is as expected. -Fit inverse actuation filters that make PRM and BS match
Stefan, Kiwamu
We then performed a fitting to get the zpk parameters out of the PRM actuator data. We used LISO. Here are the best parameters. We started from the HSTS suspension model, which was in the SUSsvn directory, as our initial guess. Since the data was not available at the low frequencies, we left the resonance at 68 mHz untouched.
=== fit parameters ===
zero 2.3327562304 7.4260090788 ### fitted (name = zero0)
zero 79.7052984298 ### fitted (name = zero1)
zero 7.1547795456 ### fitted (name = zero2)
zero 9.3953133943 ### fitted (name = zero3)
pole 2.8624375188 10.8992566943 ### fitted (name = pole0)
pole 1.6227455287 9.5958223237 ### fitted (name = pole1)
pole 6.839318e-01 2.754374e+01
factor 3.3153778483 ### fitted
We did the same fitting business on BS. We left the resonance at 42 mHz untouched.
=== fit parameters ===
zero 1.5468779344 47.4044594423 ### fitted (name = zero0)
pole 1.5752161758 20.5781923052 ### fitted (name = pole0)
pole 1.1385114613 8.7983560598 ### fitted (name = pole1)
# from BSFM model
pole 4.201750e-01 3.057337e+01
# from foton
pole 37.5835 1.04298
pole 104.999 0.95652
pole 400
pole 100
zero 1.14018 0.814411
zero 112.186 1e7
zero 30
factor 47.5420319676 ### fitted
Update on the PRM fitting:
We took some more data points of PRM at higher frequencies to make the fitting more accurate at the high frequencies. We extended the swept sine to about 250 Hz.
Here are the new set of parameters:
=======================================
zero 2.3228474583 7.4113193282 ### fitted (name = zero0)
zero 377.9190677283 41.5971099178m ### fitted (name = zero1)
zero 15.9199488645 ### fitted (name = zero2)
zero 7.4012889472 ### fitted (name = zero3)
pole 2.8669608985 10.2813809068 ### fitted (name = pole0)
pole 1.6247562788 9.6336403562 ### fitted (name = pole1)
pole 144.4376381898 487.5251791891m ### fitted (name = pole2)
pole 6.839318e-01 2.754374e+01
# foton poles and zeros
pole 314.966 0.95652
factor 3.3634583469 ### fitted
I forgot to attach the plot.
We resolved the the non-sensical Q's below 0.5, removed a meaningless pole-zero pair and refitted. This tie we also added a small delay: ======================================= zero 2.3543597867 8.0633003881 ### fitted (name = zero0) zero 16.3221439613 855.9042353766m ### fitted (name = zero1) zero 3.5808330704 ### fitted (name = zero2) pole 2.8457926226 10.9197851152 ### fitted (name = pole0) pole 1.6165053404 8.7715269619 ### fitted (name = pole1) pole 37.2960505517 ### fitted (name = pole2) pole 6.839318e-01 2.754374e+01 # foton poles and zeros pole 314.966 0.95652 delay 120u factor 3.2012088652 ### fitted ======================================= In foton: zpk([0.139329+i*2.35023;0.139329-i*2.35023;9.53503+i*13.2475;9.53503-i*13.2475;3.58083], [0.130304+i*2.84281;0.130304-i*2.84281;0.092145+i*1.61388;0.092145-i*1.61388; 0.0124154+i*0.683819;0.0124154-i*0.683819;37.2961],1,"n") Its inverse (including a Q=1, f=1 pendulum): ======================================= zpk([0.130304+i*2.84281;0.130304-i*2.84281;0.092145+i*1.61388;0.092145-i*1.61388; 0.0124154+i*0.683819;0.0124154-i*0.683819;37.2961], [0.139329+i*2.35023;0.139329-i*2.35023;9.53503+i*13.2475;9.53503-i*13.2475;3.58083; 0.5+i*0.866025;0.5-i*0.866025],1,"n")
Attached is a plot of measured and fitted actuation functions for BS and PRM. Plot 2 shows the residual relative gain of BS/PRM - certainly a lot better than before... Also, for completeness, here are the foton filters for the BS plant: zpk([0.0163157+i*1.54679;0.0163157-i*1.54679], [0.0382738+i*1.57475;0.0382738-i*1.57475;0.0647002+i*1.13667;0.0647002-i*1.13667; 0.00687158+i*0.420119;0.00687158-i*0.420119],1,"n") as well as the inverse plant. Again, it includes a f=1Hz, Q=1 pendulum. Since the BS is 1/f^4, this also includes two 300Hz real poles as roll-off: zpk([0.0382738+i*1.57475;0.0382738-i*1.57475;0.0647002+i*1.13667;0.0647002-i*1.13667; 0.00687158+i*0.420119;0.00687158-i*0.420119],[0.0163157+i*1.54679;0.0163157-i*1.54679],1,"n") zpk([],[0.5+i*0.866025;0.5-i*0.866025],1,"n")zpk([],[300;300],1,"n")
For the green team:
The IMC ASC gain was set back to 1 from 0.25.
While Yuta claimed that the recycling gain was roughly 3 for the 45 MHz sideband (alog 10441), I did an independent estimation of the power recycling gain.
I got a recycling gain of about 0.6 for the 9 MHz sideband based on the measured aboslute RF power on POPAIR_B at 18 MHz. Hmmm....
This estimation relies on the absolute power on the POPAIR_B and therefore it is less reliable than the ordinary unlocked-to-locked-comparison measurement. Note that the ring heater on ITMY was off when measured. Also, the detail of the estimation is attached.
- - - POPAIR_B_RF18 calibration:
According to alog 9845, the PD was calibrated to be 7803/(5.13 mW x 0.93 x 0.1) = 1.6e7 counts/W at 18 MHz. Since it gave 18000 counts when it was locked, this corresponds to
Pam@POPAIR_B = 18000 counts / 45 dB whitening gain / 1.6e7 counts/W = 6.2 uW at 18 MHz.
- - - Estimation of the recycling gain:
There are three mirrors which attenuate the 9 MHz sideband on its way to the POPAIR_B diode.
Then assuming the 18 MHz beatnote is only made of the 9 MHz sideband, we get an AM component of the light at the diode:
P_am@POPAIR_B = 2 x J1^2 x Pin x Gpr x T_PR2 x R_M12 x T_BS,
where Pin is the incident power on PRM, Gpr is the power recycling gain. If we assume that the modulation depth for 9 MHz is 0.17 (alog 9979) and Pin = 8.8 W x (Timc 80%) = 7.04 W, the power recycling gain Gpr should be
Gpr = 0.594
Update:
Actually I forgot to correct the responsivity for 1064 nm. The BBPD uses FFD-100 which has a responsivity of 0.4-ish and 0.15-ish at 980 nm and 1064 nm respectively. Because the calibration measurement was done for 980 nm, I should have corrected the counts/W by the ratio of the responsivity. This means that the POPAIR_B was detecting a bigger laser power than I estimated. The laser power at 18 MHz must have been 6.2 uW x (0.4 / 0.15) = 16.53 uW.
Therefore, the correct power recycling gain for 9 MHz is
Gpr = 0.594 x ( 0.4 / 0.15 ) = 1.584
First PRMI noise budget from the NB tool is attached.
Optical gain estimated from the openloop transfer function measurements are 5.5e3 W/m for MICH loop, 8.6e4 W/m for PRCL loop.
Power recycling gain estimated from this optical gains is ~ 3. This estimation was done by comparing the optical gain in simple Michelson and PRMI MICH.
Note that this estimation assumes perfect diagonalization of MICH and PRCL loop, but actually they are not diagonalized yet.
[Method]
1. Lock PRMI on sideband using REFLAIR_A_RF45_I_ERR and Q_ERR (see alog #10427).
2. Take OLTF of MICH loop and PRCL loop.
3. Keep it locked for a while to take feedback signal data (H1:LSC-MICH_OUT_DQ and H1:LSC-PRCL_OUT_DQ) for the noise budget. Data I used started from Feb 28 2014 18:25:00 UTC (local Friday morning).
4. Use the NB simulink model to plot OLTFs. Change optical gain for MICH loop and PRCL loop to match those with the measured OLTFs. Here I assumed that the error signal from BS motion only appear in REFLAIR45_Q, and PR2/PRM motion only appear in REFLAIR45_I. See attached Simulink diagram I used. Optickle block is not used since we want to make the measurement based NB model. The model lives in /ligo/svncommon/NbSVN/aligonoisebudget/trunk/PRMI/H1
.
5. Use the same model to plot noise budgets for MICH loop and PRCL loop. Sensitivity curve is estimated from the feedback signal data.
[Result]
1. OLTF_MICH_1077647116.png: OLTF of MICH loop from the measurement and the model. UGF is ~6 Hz and phase margin is ~40 deg. For the model curve, optical gain of 5.5e3 W/m was used. The measurement and the model agrees pretty well.
2. OLTF_PRCL_1077647116.png: OLTF of PRCL loop from the measurement and the model. UGF is ~60 Hz and phase margin is ~30 deg. For the model curve, optical gain of -8.6e4 W/m was used. The measurement and the model agrees OK except for the dip at ~13 Hz, which comes from closs coupling with MICH loop. This is because we only use BS for MICH loop, but BS also changes PRCL.
3. NB_MICH_1077647116.png, NB_PRCL_1077647116.png: Noise budget for MICH and PRCL loop. Note that seismic noise is not real (copied from LLO model). Sensor noise is currently not contributing very much. MICH motion is larger than PRCL motion (because of BS motion?).
[Discussion on PRMI optical gain]
1. Measured optical gain (from BS motion * sqrt(2) to REFLAIR45_Q) for simple Michelson was 1.9 W/m, including the cable loss (see alog #10213). The things changed in MICH loop for simple Michelson and MICH in PRMI are;
MI PRMI MICH
PD whitening gain 45 dB 0 dB
H1:LSC-MICH_GAIN 900 5
output matrix for BS 0.05 1
measured optical gain 1.9 W/m 5500 W/m
This gives overall gain ratio of MI/(PRMI MICH) = 1.3. Since the UGFs for simple Michelson and PRMI MICH loop was 8 Hz (see alog #10127) and 6 Hz respectively, this ratio is consistent.
2. Optical gain ratio between simple Michelson without PRM and PRMI should be approximately equal to the power recycling gain (PRG). However, since we did optical gain measurement for simple Michelson with PRM misaligned, measured optical gain will be smaller by factor of T_PRM^2. Thus, the ratio between simple Michelson with PRM misaligned and PRMI will be approximately Gp/T_PRM^2. So, estimated power recycling gain is;
Gp ~ 5.5e3/1.9 * 0.03^2 = 2.6
Designed PRG for PRMI is 58 according to LIGO-T1300954. Considering the closs-coupling between PRCL loop and MICH loop, this estimation seems to be an upper limit to the actual PRG (see below).
3. According to Optickle simulation in LIGO-T1300328, sensing matrix for PRMI sideband is
PRCL MICH
REFL 45I 3.4e6 2.5e3
REFL 45Q 6.4e4 1.3e5 W/m
So, simulated ratio between diagonal elements is PRCL/MICH = 3.4e6/1.3e5 = 26. Our optical gain estimation gives 8.6e4/5.5e3 = 16.
Considering the fact that we are ignoring the off-diagonal elements in the optical gain estimation, I think this is reasonable. For example, BS to REFL 45Q could be 1.3e5+6.4e4 W/m and 3.4e6/(1.3e5+6.4e4) = 18.
[Next]
- Measure PRMI sensing matrix, compare with the simulation, and use it in the NB model
- Update the simulink model so that it can handle off-diagonal elements
- Output matrix diagonalization for PRMI
- Include online seismic noise, frequency noise and intensity noise in the NB model
[Yuta, Evan]
From the above work, we can place a bound on the reflectivity of the locked Michelson (Rmich), and therefore also the finesse and the contrast defect.
From eqs. 4 and 6 of Freise and Strain's LRR paper, the power recycling gain in the plane-wave approximation is Gp = Tprm / (1 − sqrt(Rprm Rmich))^2. Using Gp = 2.6 and Tprm = 1 − Rprm = 0.03, we find Rmich = 0.82. The finesse is then pi * (Rpm Rmich)^(1/4) / (1 − sqrt(Rprm Rmich)) = 27.
Of the power incident on the Michelson, we lose 0.014 through ITMX, and 0.03 through ITMY. With our estimated Tmich = 0.18, this gives 0.136 leaving through the AS port.
Beyond the plane wave approximation, any mode mismatch of the light incident on the PRM will decrease the observed power recycling gain, and thereby decrease the estimated value of Rmich. The above finesse value is therefore a lower bound, and the above contrast defect is therefore an upper bound.
Today was another good day of arm locking.
The comm handoff was still reliable this morning. I had a look at the open loop gain, and decided to try using higher gain. I was able to push the loop gain up to 35kHz, where we have 40 degrees phase margin. I turned the PLL gain down to 27dB to move the gain peaking to lower frequencies in order to make the higher ugf stable. With a CM board gain of 18, I was able to engage the first boost in addition to the common compensation. Data and plots of the new open loop gain are attached. (59 is a GIF, 58 is phase and 57 is magnitude)
Qualitatively, this makes the IR resonance in the arm more stable. I've attached a stiptool showing the transmitted IR at the settings we have been using up to now, 9dB, and in the laster part with 18dB and the first boost on. Maybe there is hope after all for ALS COMM.
I also lowered the UGF of the IMC VCO frequency servo to 0.7 Hz, since it oscillates sometimes.
We need to start thinking about how to align the IR to the arm cavity. Today I tweaked PR2 and IM4 by hand. The red team is already doing a dither alignment on PR2, it would be nice if we could add the IR transmitted signal to this so we could use it to align to the arm.
I also had made a twinCAT library a while ago that was intended to automate finding the IR resonance in the arm cavity. I added an medm screen to the ALS overview screen, but this still needs work.
Note to the Red team/blue team/anyone who cares to lock the IMC
Since ALS COMM has been locked for almost half an hour, I'm going to leave it on with the IR resonanting in the arm. Since we don't have a guradian yet, someone will have to run the COMM_down script before the IMC can lock again once this drops tonight
it is in userapps als/h1/scripts
./COMM_down
The green team had some sucess today.
We saw that there is a large wandering peak (similar to what we have seen in the IMC alog 10289 alog 10327) in COMM PFD Imon. This PFD chassis is directly under the diff RF doubler, by disconnecting the 79MHz input from this doubler we saw the peak become much smaller. We are leaving this unplugged since we don't need it yet. (Alexa has some movies of the two wandering peaks)
The Xarm guardian is working, at least the states up to LOCKED_W_SLOW. We didn't test the dither alingment states since the dither alignment isn't really working anyway.
The COMM PLL slow feedback to the IMC VCO had low bandwidth, which was limited by the randomization in the VCO servo library. Daniel edited the low noise VCO library, the servo now has two modes, internal where the frequency comparator is used for an error signal, and external, meant for use with the COMM PLL. The bandwidth is now limited to about 1 Hz, by the VCO response. Right now we have the gain setting for the COMM PLL slow feedback set to 14000Hz/V, and the ugf of the IMC VCO servo set to 0.8Hz. This seems stable. We also turn this off after the COMM handoff now.
We found a few gremlins in the COMM handoff- with the change to LSC input matrix our script was no longer setting the matrix element. For some reason the fast path was disabled in the REFL servo. Both of these things could be solves with state control code or for the time being by improving the script/writting a guardian. Now we are reliably doing the COMM handoff, which is stable for ~20 minutes to a half an hour right now. I've just committed the handoff and down scripts to the svn.
We rewired the REFL_DC_BIAS, so now it is routed into the CM board input 2
Once we had this locked we started looking at the IR transmission. When the alignment is good, we stay within about 160Hz (the transmitted power wanders over the peak back and forth, but doesn't move as far as we have seen some nights. We have seen that the amount of noise we see depends on the alingment.
We found the IR resonance, moved the ETM in YAW, and found the resonance again. We made three measurements like this and got 400Hz/urad. When the alingment was worse this measurement got harder.
It seems clear we need a good alingment to have a chance of locking COMM on resonance.
Right now COMM has been locked for half an hour.
Here is the video Sheila is refering to. The power spectrum in the top display is from the IMON of the PFD whereas the bottom display is from the output of the IMC.
After the MC2 trip, the MC2 guardian turned off the outputs from the lock fitlers for all three stages. The IMC guardian did not reset these (except for M1 and M2 lock) , so the IMC could not lock. I added a few lines in the acquire state of the IMC guardian that turn these back on.
We had another ocurence of TwinCAT near the time of a trip of HAM2+3. This is the first screen shot attached. (MC2 and PR2 were also tripped)
Then as the guardian was bringing back HAM3 it tripped again.
This report is a summary of some of the issues that came up during the recent ISI_HAMX guardian commissioning (alog 10394, alog 10300):
There is quite a bit of overshoot in the X/Y location when the platform are ramped to RX/RY setpoints with offsets. The image below shows the CPS_<dof>_LOCATION readback while the setpoint ramps with 10 urad offsets in RX and RY:
Note that X and Y locations swing through more than 100,000 counts during and after the ramp. Fabrice's suggestion is therefore that we break up the isolation procedure such that we engage the isolation loops and ramp the biases for the RX and RY degrees of freedom first, before engaging the isolation loops for the other degrees of freedom. This will help prevent the isolation loops from saturating during the isolation process, even if there are large cart bias offsets.
During deisolation we should also be ramping down any biases before we begin the deisolation procedure.
I have written two cron jobs which run on script0 as user controls. They log any front end restarts and produce daily reports of such restarts.
The logger runs every minute, the daily logger runs at 5 minutes past midnight.
Details are available in the wiki page:
https://lhocds.ligo-wa.caltech.edu/wiki/FrontEndModelRestartLogging
the code should be transparent to the front end model user except for the reboot.log file being removed within a minute of the restart completing.
The goal is to have the daily logger make a robo-log entry in the ALOG.
While TMS and SUS were removing extra (transport Payload) from the system, Jim & I confirmed corner connections on the SEI Sensors and wired up the remaining parts of position sensors. With the payload now very close to final, we'll do another level check maybe (Dial Indicators show ~0.2mm tilt change) and adjust that if needed. We'll then unlock and balance followed by locker/CPS Target adjustments in this final configuration. Maybe by days end Monday we'll be ready for SUS to unlock but plan on Tuesday earlist. Then TFs can ensue.
(Sheila, Daniel)
This afternoon the noise eater of the ALS laser in H1 EX was oscillating. After some TwinCAT work, we were able to toggle the noise eater off and on remotely. This worked as expected and cleared the noise eater oscillation.
PS. There are 2 relay contacts wired up. Only the first one seems to be needed. I disconnected the second.
With the RF doubler for the 79.2 MHz source moved on top of the ALS distribution chassis, we took another look at the modecleaner error signal. The intermodulation product with the PSL VCO is still visible but small. It is about an order of magnitude smaller than before. This seems good enough for now, but could potential effect the noise of the full interferometer.
[Ed, Evan]
We are preparing to make a measurement of the length of the PRC using the phase-locked auxiliary laser technique described by Chris Mueller (T1400047). Previously, this has been used to measure the Livingston IMC length (LLO alog 9599).
We set down a 520 mW Lightwave NPRO on the IOT2R table, along with a Faraday isolator and steering mirrors. We will inject this beam into the PRM_refl side of the IOT2R periscope. The beam will hit the back of IM4, and a small fraction (2400 ppm) will be transmitted toward the PRM. This gives 1.2 mW of auxiliary power on the PRM, compared to 9 mW of 45MHz PSL single-sideband power on the PRM.
Most of the auxiliary power should reflect from the back of IM4 and return to the IOT2R table via the IO_forward side of the periscope. For mode-matching, we hope that we can simply send part of the IO_forward beam onto a New Focus 1611 and maximize the observed beat. Currently, there is 3 mW of power in the IO_forward beam.
Using this beat, or otherwise, we will phase-lock the auxiliary laser to the PSL carrier beam. Then with PRMI locked on the PSL sideband, we will sweep the offset to the auxiliary PLL and monitor the RF coming out of POPAIR_B. We should see the strength of the RF reach a maximum whenever the auxiliary beam is coresonant with the the PSL sideband. By tracing out the Lorentzian profile of the RF amplitude across successive resonances of the PRC, we can extract the FSR of the PRC. Given a design length of 57.6557 m, we expect an FSR of 2 599 850 Hz. If we can measure the FSR to within 100 Hz, we can get the PRC length to within 2 mm.
Yesterday we got the NanoScan back from EX and Ed used it to measure the beam parameter coming out of the Faraday isolator. The waist is about 100 µm and located more or less in the middle of the isolator. The size is maybe a bit smaller than we want, but we appear to be able to get more than 90% of the power through, with a reasonably Gaussian mode.
After the FI, we placed a HWP to set the beam to be s-polarized. After this, we placed a New Focus 5104 as a first steering mirror. As a second steering mirror, we use IO_PRMR_BS1.
We removed a lens from between IO_PRMR_M3 and IO_PRMR_BS1. It was unlabeled, and anyway there is nothing after that lens except beamsplitters and dumps.
We did an ALM optimization to mode match to the PRM. Joe Gleason's IOT2R layout (D0902284) gives the distance from the bottom of the IOT2R periscope to the PRM as 3.6 m. The spot size is 2.24 mm, with a ROC of 11 m (T0900407, p 5). ALM told us to put an f = 500 mm lens about 3 inches before IO_PRMR_M3 ("before" meaning "closer to the FI").
We put down two irises in order to constrain the pointing of the PRM_Refl beam. We then blocked this beam and steered the auxiliary beam through the irises. With a little tweaking, we were able to see our beam coming out on the IO_Forward part of the periscope. We measured the power of this beam and found that it was only about 5% of what we were putting in. This initially confused us, until we realized that our path in HAM2 has to go through a 90% reflector which is intended for the ISS. Given that IO_PRMR_BS1 is a 90% reflector and ROM LH1 (in HAM2) is also a 90% reflector, we in fact only expect 90% × 90% × 10% = 8% of the power to come back onto the IOT2R table.
Yesterday, we put down the New Focus 1811, aligned the PSL and auxiliary beams from IO_forward onto the PD. We found a beat with the auxiliary laser temperature around 37.7 °C. By tweaking the auxiliary input pointing, we were able to get -4 dBm of RF beat out of the 1811 with about 1 mW of DC power from each beam in front of the PD (so 2 mW total).
We were then able to implement a PLL using an HP function generator and the LB1005 servo box. We set the function generator to ~30 MHz and +7 dBm, and used it to drive the LO of a mixer. We took the beat and put it into the mixer RF. The IF was terminated, filtered at 1.9 MHz, and then fed into the LB1005. The output of the LB1005 was then fed into the fast input of the laser. We were able to catch lock by turning the laser's temperature control knob to push the beat toward 30 MHz. The lock would hold for about 1 minute before the controller saturated. To maintain sanity, I suspect it will be necessary to implement a slow temperature loop to relieve the fast controller.