This is very nice. We have, for the first time, a real time plant with which we can test our changes of the control system. From my understanding, we have a control system with the usual POS/PIT/YAW matrices and filter banks. The outputs go to a separate real-time system which is running something similar and where we have loaded the pendulum TF as a filter. Cross-couplings, AA & AI filters, and saturations to come later.

The attached plot is just the same as what Peter posted earlier, but with more resolution. I drove at the input to the SUSPOS filter bank and measured the open loop with the loop closed. The loop wants an overall gain of -0.003 or so to be stable.

Big thumbs down to whoever put a beam dump on the PSL table in front of the PMC yesterday afternoon without noting it in the elog

The offending beam dump has been removed, and the PMC relocked.

The second set of Guralp channels is now plugged into the PEM ADCU, into channels which are confirmed to be working.  (Method: 1Vpp sine wave into channel, check with DataViewer).

Direction, Channel Name, .ini chnum, BNC plug # on ADCU

Vertical: C1:PEM-SEIS_GUR_VERT, 15023, #24

N/S (should be Y when the seismometer is put in place): C1:PEM-TEMP_2, 15001, #2

E/W (should be X when the seismometer is put in place): C1:PEM-TEMP_3, 15002, #3

There is IFO work going on, so I don't want to rename the channels / restart fb40m until a little later, so I'll just use the old TEMP channel names for now. 

There is something totally wrong with the E/W channel.  I can look at all 3 channels on a 'scope (while it's on battery, so the op-amps in the breakout box aren't grounded), and VERT and NS look fine, and when I jump around ("seismic testing"), they show spikes.  But the EW channel's signal on the 'scope is way smaller, and it doesn't show anything when I jump. 

I might use the handheld Guralp tester breakout box to check the seismometer.  Also, a suspicion I have is that whoever put the box back in on Friday night after our final noise measurements left the inputs shorted for this one channel.  It's the 3rd channel in the set, so it would be most likely to be stuck shorted...  Investigations will ensue.

 Maybe it was Russell Crowe

I aligned the MZ.  The reflection went from .86 to .374

I've added the PIT and YAW dofs to the MDC and MDP systems.  The pendula frequencies in MDP are 0.8, 0.5, 0.6 Hz for POS, PIT, and YAW respectively.  The three dofs are linear and uncoupled, and stable, but there is no modeled noise in the system (yet) and some gains may need bumping up in the presence of noise.  The MDC filters are identical for each dof (3:0.0 and Cheby). The PIT and YAW transfer functions look pretty much like the one Rana recently took of POS, but of course with the different pendulum frequencies.  I've attached one for YAW.

Pete, Koji

We discussed a preliminary game plan for this project.  The thing I really want to see is an ETMX RCG controller hooked into the existing frontend via reflective memory, and the 40 m behaving normally with this hybrid system, and my list is geared toward this.  I suspect the list may cause controversy.

+ copy the MDC filters into SAM, and make sure everything looks good there with DTT and SR785.

+ get interface / wiring boards from Wilson House, to go between megatron and the analog ETMX system

+ test tying the ETMX pendulum and bare-bones SAM together (use existing watchdogs, and "bare-bones" needs defining)

+ work some reflective memory magic and create the hybrid frontend

In parallel with the above, the following should also happen:

+ MEDM screen design

+ add non-linear bits to the ETMX MDP/MDC model system

+ make game plan for the rest of the RCG frontend

 All the channels are now good, and all the names are back to making sense. 

The problem with EW2 was in fact that the alligator clip used to short the inputs during the noise test Friday night was left in the box.  Not great, but now it's taken care of, and we have recorded data of the noise of the breakout box, so we can include that in our plots to see if we're at the limit of how good we can do at subtracting noise.

The channels are now named thusly:

C1:PEM-SEIS_GUR_VERT  (BNC input #24, .ini channel #15023)

C1:PEM-SEIS_GUR_EW     (BNC input #3, .ini channel #15002)

C1:PEM-SEIS_GUR_NS      (BNC input #2, .ini channel #15001)

C1:PEM-SEIS_MC1_X         (BNC input #11, .ini channel #15010)

C1:PEM-SEIS_MC1_Y        (BNC input #12, .ini channel #15011)

C1:PEM-SEIS_MC1_Z       (BNC input #10, .ini channel #15009)

C1:PEM-SEIS_MC2_Y (Ranger, which for the Huddle Test is oriented VERTICALLY)   (BNC input #4, .ini channel #15003)

Now we wait.....and tomorrow extract the noise of each of the seismometers from this!

Rana, Alberto

This afternoon we tried to improve the mode matching of the beam to the PMC. To do that we tuned the positions of the two lenses on the PSL table that come before the PMC.

We moved the first lens back an forth the without noticing any improvement on the PMC transmitted and reflected power. Then we moved the first backwards by about one cm (the order is set according to how the beam propagates). That made the things worse so we moved also the second lens in the same direction so that the distance in between the two didn't change significantly. After that, and some more adjustments on the steering mirrors all we could gain was about 0.2V on the PMC transmission.

We suspect that after the problems with the laser chiller of two months ago, the beam size changed and so the mode matching optics is not adequate anymore.

We have to replace the mode matching lenses with other ones.

the servo needs some work. 

2 day trend

While writing my progress report, I redrew the Guralp breakout box circuit diagram with all the changes marked. Since only one hard copy exists, I thought it might be useful to post my drawing up in case it is needed for any reason. The two drawings are the same - the second has just been broken into two parts to make it easier to fit on a normal 8.5 x 11 or A4 sheet of paper. The gains for each opamp have not been marked, but they could very easily be added in if necessary. The black resistances and capacitances are the originals. All changes have been indicated in blue.

I was able to observe the three sets of modulation sidebands created by the EOM + triply resonant circuit yesterday. Quantitative results will be posted later.

Spent a lot of time aligning tonight.  The BS is not staying put--sometimes after a lock loss it gets badly mis-aligned. 

DD handoff is working, after putting beam on REFL diodes and running senseDRM script.

I measured the magnitude of modulation as a function of frequency using the optical spectrum analyzer and an oscilloscope while generating signals using a Marconi signal generator; the results are shown in the attached plot and are compared to the expected modulation given the measured transfer function of the circuit and the nominal modulation index of the EOM used (13 mrad/V). Using the oscilloscope, I found the resonant peaks to be at 11.11 MHz, 29.57 MHz, and 54.70 MHz. There are several different colors on the plot; this is because I had to take the data in several different segments and had to switch to measuring a different sideband partway through the measurment. I also separately found the modulation at each resonant peak for each sideband. The magnitude of modulation was measured  by finding the ratio between the magnitude of the carrier and sideband powers using an oscilloscope, and calculating the magnitude of modulation from this. This method was also used to quantify the dependence of modulation magnitude on input power at each resonant peak; these results are also attached. These same results can also be plotted as modulation magnitude as a function of voltage into the resonant circuit; this is also attached (I'm not sure which is more useful).

In order to produce these results (get the measurements in mrad/V) it was necessary to measure the gain of the amplifier. I used the signal generator to input signals of varying power and measured the output signal voltage using the oscilloscope; I then repeated this process at each resonant frequency. From this I was able to calculate the gain of the amplifier to be 28.1 dB at 11.11 MHz, 27.4 dB at 29.57 MHz, and 25.7 dB at 54.70 MHz. These values are in the same ballpark as the values in the Mini Circuits data sheet (all values are ~25-28 MHz).

Today I set up the EUCLID long range michelson design on the SP table; It's the same as the setup posted earlier, but without the pickoff (at PD1), which can be added later, and a few other minor changes (moved lenses, mirrors, PDs - nothing major).  I hooked up the two PD's to the oscilliscope and got a readout that pointed to more power hitting PD2 than PD3.

So that I can collect a bit of free-swinging Mode Cleaner data, I started a script to wait 14400 seconds (4 hours), then unlock the mode cleaner.  It should unlock the MC around 4am.  As soon as someone gets in in the morning, you can relock it.  I should have plenty of data by then.

When Rob and I were getting started on locking for the evening, Mode Cleaner lost lock a few times, but every time it lost lock, it took forever to reaquire, and was pretty insistent on locking in the TEM10 mode.  I proposed that the alignment might be sketchy.  I've been fiddling with the MC alignment sliders for the last hour and a half or so, but I think I'm not 100% in tune with the 3 mirror parameter space.  The mode cleaner now locks, but I'm not in love with its' alignment.  The WFS are definitely catywhompus.  Before doing hardware things like recentering the WFS, I'm going to wait until tomorrow to consult with an alignment expert.

In case this is helpful for tomorrow, before I touched any of the sliders:

Optic, Pitch, Yaw

MC1, 3.1459, -0.7200

MC3, -0.8168, -3.0700

MC2, 3.6360, -1.0576

Now that mode cleaner locks, although not in a great alignment:

MC1, 3.1089, -0.7320

MC3, -0.7508, -3.0770

MC2, 3.6610, -1.0786

If I knew how to kill my script to unlock the mode cleaner, I would.  But I sourced it, and Rob didn't know earlier this evening how to kill something which is started with 'source' since it doesn't seem to get a process number like when you './'  to run a script. So the Mode Cleaner will probably be unlocked in the morning, and it may be persnickity to get it relocked, especially if the tree people are doing tree things with giant trucks again in the morning.

Rana, Jan, Jenne

We noticed that the Ranger data was all bogus at low frequencies. So we checked it and found that the proper procedure had not been used when changing it from horizontal to vertical last week. So the huddle test data from the weekend is not valid for the ranger; we will have to repeat it sometime.

So we used the manual, and extended the hanger rod on top of the Ranger to free the mass. It now has good response and coherence with the Guralps down to 0.1 Hz. See attached plot soon.

I put all three seismometers and all six accelerometers together in the foam box with peanuts. Three of the accelerometers are facing in the x-direction and three are in the y-direction. Both Guralps are aligned on the NS axis and the Ranger is pointing vertically.

**EDIT: The accelerometers are in the x and z directions, not x and y. Sorry, I was sleepy when I wrote this.**

One of the accelerometers was refusing to show anything, and after a few hours of checking connections and swapping cables, I discovered that someone had unplugged the cable from the ADC. A quick glance in the dataviewer shows that the channel has been unplugged since about 3 in the afternoon on August 8th (Saturday). So... obviously all the accelerometer measurements made with that channel since then did not actually get recorded. Yay.

Anyway, as of 2:45, everything is working and taking data. Clearly we're not getting a full night's worth... hopefully that's okay.

When I came in earlier today, I noticed that c1susvme2 was red on the DAQ screens.  Since the vme computers always seem to be happier as a set, I hit the physical reset buttons on sosvme, susvme1 and susvme2.  I then did the telnet or ssh in as appropriate for each computer in turn.  sosvme and susvme1 came back just fine. However, I couldn't cd to /cvs/cds/caltech/target/c1susvme2 while ssh-ed in to susvme2.  I could cd to /cvs/cds, and then did an ls, and it came back totally blank.  There was nothing at all in the folder. 

Yoichi showed me how to do 'df' to figure out what filesystems are mounted, and it looked as though the filesystem was mounted.  But then Yoichi tried to unmount the filesystem, and it claimed that it wasn't mounted at all.  We then remounted the filesystem, and things were good again.  I was able to continue the regular restart procedure, and the computer is back up again.

Recap: c1susvme2 mysteriously got unmounted from /cvs/cds!  But it's back, and the computers are all good again.

Rather than make a new elog post every time I move something, I'm going to just keep updating this Google spreadsheet, which ought to republish every time I change it. It's already got everything I've done for the past week-ish. The spreadsheet can be accessed here, as a website, or here, as a pdf. I will still post something nightly so that you don't have to search for this post, but I wanted to be able to provide more-or-less real-time information on where things are without carpet-bombing the elog.

The EUCLID-style Michelson readout is on the SP table now and is aligned.  See image below.  I took several power spectra with the plotter attached to the HP3563 (not sure if there's another way to get the data out) and I'm still waiting to calibrate (since dP/dL isn't constant as it isn't locked, this is taking a bit longer).  When put into XY mode on the oscilliscope (plotting Voltage at PD2 on the x and Voltage at PD3 on the y), a Lissajous figure as in the first plot below.  It's offset and elliptical due to imperfections (noise, dc offset, etc) but can ideally be used to calculate the L_ target mirror movement.  By rotating the first quarter wave plate by ~80.5deg counter-clockwise (fast axis was originally at Pi/8, now at 103deg), I was able to turn the Lissajous figure from an ellipse into a more circular shape, which would ideally allow for us to use a circular approximation (much simpler) in our displacement calculations.

As Rob noted last Friday, the UPS which powers the Vacuum rack failed. When we were trying to move the plugs around to debug it, it made a sizzling sound and a pop. Bad smells came out of it.

Ben came over this week and measured the quiescent power consumption. The low power draw level was 11.9 A and during the reboot its 12.2 A. He measured this by ??? (Rob inserts method here).

So what we want is a 120 V * 12.2 A  ~ 1.4 kVA UPS with ~30-50% margin. We look for this on the APC-UPS site:

On Monday, we will order the SUA2200 from APC. It should last for ~25 minutes during an outage. Its $1300. The next step down is $200 cheaper and gives 10 minutes less uptime.

It was fine when I came in earlier today, but I just got back from dinner, and it's not good. I looked in dataviewer, and it seems to have been sliding out for the past couple of hours... Here is a picture:

I swear I am not responsible this time... all I've been doing is working in the control room.

 Mode cleaner bounced back on its own about 2 hours ago.

I shorted the inputs on three channels and the outputs on three channels of the Guralp box, and I did similar things with the accelerometers. I was going to move the instruments themselves back, but I didn't have time, so they are still in the box in the corner. If the setup could stay as-is for at least a few hours, that would be awesome.

The Mach Zehnder and I got to know each other today.  The reason for redoing the alignment was to improve pointing from the PSL table into the MC/IFO in hopes that this would solve the MC unlocking problems that we've been having lately.  Since Rana had aligned the IOO QPDs a few weeks ago when all of the alignments and things were good, I used them as a reference for my Mach Zehnder alignment activities. 

 
The order of operations were approximately as follows:

1. Block the secondary (west) arm of the Mach Zehnder using either an aluminum or razor dump.

2. Use SM1 in the MZ to align the beam to the IOO_QPDs (Pos and Ang).  I unfortunately also touched BS2 at this juncture, which made the refl path no longer a reference.

3.  Make sure that the QPD Sum on both Pos and Ang was sensible.  Since there are 2 beamsplitters in a Mach Zehnder, the power on the QPDs should be a quarter when only one beam is on them.  Be careful not to allow the beam no clip on anything.  The biggest problem was the bottom periscope mirror - if you hit it too high or too low, since it is a very thick optic, you end up coming out its side!  This is the frosty part on the edges, totally inappropriate for beams to go through!  Since the side of the periscope mirror isn't HR coated, when going through it like this, I was able to saturate the QPDs.  Not so good. 

4. Also, make sure that this first beam is on the MZ Refl PD.  Do this using the steering optics after the beam has left the MZ.  Use a viewer to look at the PD, and see the small spot of the beam on the diode.  We closed the iris which is present and was standing fully open to remove a spurious beam which was a parallel split-off of the main beam.  Since it was very weak, it is fine.

5.  Unblock the west arm, and block the east arm of the MZ.

6. Align this arm to both the IOO QPDs and the MZ refl diode using the adjustments on BS1, the PZT mirror and if necessary, BS2.  Note that the adjust knobs on the PZT mirror have lock screws.  Make sure to unlock them before adjusting, and relock afterward, to avoid slipping while the PZT is moving.

7.  Unblock all the beams, and make sure there is only one spot both on the transmission side and the reflection side, i.e. the 2 spots from the 2 arms are completely overlapping.  For the Trans side, make sure to look both in the near field and the far field (even after the periscope) to ensure that you really have one spot, instead of just the 2 spots crossing at a single location.

8.  Look at the MZ refl DC out and the PD out from the ISS box (which is essentially MZ trans, looking at Morag and Siobhan) on a 'scope.

9.  Touch / gently wiggle BS1 or another optic, and watch the 'scope.  At the same time, adjust BS1, the PZT mirror and BS2 to maximize the contrast between light and dark fringes.  Ideally, the refl PD should go almost to zero at the dark fringes.

10.  Check that you still have only one overlapping beam everywhere, and that you're actually hitting the MZ refl PD.

11. Because I was concerned about clipping while still figuring out the status of the lower periscope mirror, I removed the beam pipe holders between the last optic before the periscope, and the lower periscope mirror.  The beam pipe had already been removed, this was just the pedestals and the snap-in clamps.

All done for now!  Still to be done:  Optimize the position of the EOMs.  There is a waveplate out front and the EOMs are mounted in such a way that they can be moved in several directions, so that we can optimize the alignment into them.  They ideally only should see a single polarization, in order to apply solely a phase modulation on the beam.  If the input polarization isn't correct, then we'll get a bit of amplitude modulation as well, which on PDs looks like a cavity length change.  Also, the little blue pomona-type box which has the RF signals for the EOMs needs to be clamped to the table with a dog clamp, or better yet needs to be moved underneath the PSL table, with just the cables coming up to the EOMs.  The SMA connections and the SMA cable kept interfering with the MZ refl beam...it's a wonder anyone ever made the beam snake around those cables the way they were in the first place. Right now, the box is sitting just off the side of the table, just inside the doors.

 
Something else that Rana and I did while on the table:  We moved the PMC trans optics just a teensy bit toward the PSL door (to the east) to avoid coming so unbelievably close to the MZ refl optics.  The PMC trans beam shown in the lowest part of my sketch was very nearly clipping on the MZ refl steering optic just near it.  This situation isn't totally ideal, since (as it has been in the past), the first optic which is dedicated to the PMC trans isn't fully sitting on the PSL table.  The pedestal needs to hang off the edge of the table a bit to keep this beam from clipping.  Unfortunately there really isn't space to make a better beam path.  Since we're planning on getting rid of the MZ when the upgrade happens, and this isn't causing us noticeable trouble right now, we're going to let it stay the way it is.

Also, we dumped the reflection from the PMC RFPD onto a razor blade dump. And we noticed that the PZT mirror and BS2 in the MZ are badly vibrationally sensitive. BS2 has a ~400 Hz resonance (which is OK) but a ~150 ms ringdown time!! PZT mirror is similar.

Q = pi * f * tau = 200!  Needs some damping.

Rob, Yoichi

The MC WFS have apparently been bad for a few days, causing the MC alignment to drift away at DC.  We tried a few things to fix it, including jiggling some EPICS settings in the WFS head & demod screens.  This seemed to work for WFS1 but not WFS2.  Confused, we decided to go stare at the rack 1Y2.  While doing that, we noticed that the top two Sorensens in 1Y1 (these are directly below the Guralp box) were at different voltages from nominal.  The 5V had dropped to 4.2V and the 24V was at 24.6V.  We adjusted the knobs until these were set correctly.  After this, the MC WFS appear to work again.

When working in a rack, you must be as careful about accidentally touching things as when working on an optical table.

In the future, mirrors shouldn't be so close together that you can't get at their knobs to adjust them No good.  I ended up blocking the beam coming out of the PMC to prevent sticking my hand in some beam, making the adjustment, then removing the dump.  It worked in a safe way, but it was obnoxious. 

- we finished the MZ alignment; the contrast is good.

- we did the RFAM tuning using a new technique: a bubble balanced analyzer cube and the StochMon RFPD. This techniques worked well and there's basically no 33 or 166 RFAM. The 133 and 199 are as expected.

- the MC locked right up and then we used the periscope to align to it; the transmission was ~75% of max before periscope tuning. So the beam pointing after the MC should be fine now.

- the Xarm locked up with TRX = 0.97 (no xarm alignment).

If Rob/Yoichi say the alignment is now good, the we absolutely must center the IOO QPDs and IP POS and IP ANG and MC TRANS  today so that we have good references.

-----------------------------------

The first photo is of our nifty new setup to get the beam to the StochMon PD.  The MZ transmitted beam enters the photo from the bottom right corner, and hits the PBS (which we leveled using a bubble level).  The P-polarization light is transmitted through the cube, and the S-polarization is reflected to the left.  The pure S-polarized light hits a Beam Splitter, which we are using as a pickoff to reduce the amount of light which gets to the PD.  Most of the light is dumped on an aluminum dump.  The remaining light hits a steering mirror (Y1 45-S), goes through a lens, and then hits the StochMon PD.  While aligning the MZ to maximize visibility, we look at the small amount of P-polarized light which passes through the PBS on an IR card, and minimize it (since we want to be sending purely S-polarized light through the EOMs and into the MC).

The second photo is of a spectrum analyzer which is directly connected to the RF out of the StochMon PD.  To minimize the 33MHz and 166MHz peaks, we adjust the waveplates before each of the EOMs, and also adjusted the tilt of the EOM holders.

The final photo is of the EOMs themselves with the Olympus camera.

Once we finished all of our MZ aligning, we noticed that the beam input to the MC wasn't perfect, so Rana adjusted the lower periscope mirror to get the pointing a little better.  

The MZ refl is now at 0.300 when locked.  When Rana reduced the modulation depth, the MZ refl was about 0.050 .  Awesome!

 IOO_QPD_POS,    IOO_QPD_ANG,    MC_TRANS,    IP_POS, IP_ANG    have all been centered.

Also, the MCWFS have been centered.

I'm now working on making sure beam is hitting all of the RF PDs around.

All of the LSC RF PDs have been aligned.  I didn't really change much of anything, since for all of them, the beam was already pretty close to center.  But they all got the treatment of attaching a Voltmeter to the DC out, and adjusting the steering mirror in both pitch and yaw, finding where you fall off the PD in each direction, and then leave the optic in the middle of the two 'edges'.

Before aligning each set (PO, Refl, AS), I followed the procedure in Rob's new RF photodiode Wiki Page. 

Also, for superstitious reasons, and in case I actually bumped them, I squished all of the ribbon cable connectors into the PDs, just in case.

locking work proceeding apace tonight.

diagonalized DRM with setDDphases & senseDRM. 

initial locks are fairly quick, aqstep script succeeds reliably.

first part of cm_step (handoff CARM-> MCL) usually works.

tuning up later parts of cm_step (presumably due to optical gain changes resulting from MOPA decline). 

got to arm powers ~60.

[Kevin, Jenne]

Kevin's awesome final report/elog entry was so awesome that it crashed the elog.  It has been restarted.  We're going to put his pictures and documentation in the wiki, with a link from the elog to prevent re-crashing.

Using free-swinging Mode Cleaner OSEM data and Guralp seismometers, I have taken transfer functions of the Mode Cleaner stacks.

During this experiment, the MC was unlocked overnight, and one Guralp seismometer was underneath each chamber (MC1/MC3, and MC2).  Clara will let me know what the orientation of the seismometers were (including which seismometer was underneath which chamber and what direction the seismometer axes were pointing), but for now I have included TFs for every combination of suspension motion and seismometer channels.

I combined the 4 OSEM channels for each optic in POS and PIT, and then calibrated each of my sus channels using the method described in Kakeru's elog entry 1413. Units are meters for POS, and radians for PIT.  I also calibrated the guralp channels into meters.

The traces on each plot are: MC_{POS or PIT} / Guralp_{1 or 2}_{direction}.  So each plot shows the coupling between every seismometer direction and a single mirror direction.  The colors are the same for all the plots, ie the gold trace is always Gur1Z.

Looks like all of the accelerometers and seismometers have been disconnected since early AM last Monday when Clara disconnected them for her sensor noise measurement.

 Peter King is updating our temp box as Hugh did at Hanford Oct.22 of 2001 I still have not seen an updated drawing of this.

The LT 1021-7 reference chip will arrive tomorrow morning. This modification should be completed by noon.

 ** The link to the DCN from Hugh is here in the DCC.

I just found the elog down and I restarted it.

 Is that the reason of the PSL craziness tonight? See attachment.

There's no elog entry about what work has gone on today, but it looks like Peter took apart the reference cavity temperature control around 2PM.

I touched the reference cavity by putting my finger up underneath its sweater and it was nearly too hot to keep my finger in there. I looked at the heater power supply front panel and it seems that it was railed at 30 V and 3 A. The nominal value according to the sticker on the front is 11.5 V and 1 A.

So I turned down the current on the front panel and then switched it off. Otherwise, it would take it a couple of days to cool down once we get the temperature box back in. So for tonight there will definitely be no locking. The original settings are in the attached photo. We should turn this back on with its 1A setting in the morning before Peter starts so that the RC is at a stable temp by the evening. Its important NOT to turn it back on and let it just rail. Use the current limit to set it to 1 A. After the temperature box is back in the current limit can be turned back up to 2A or so. We never need the range for 3A, don't know why anyone set it so high.

The reference cavity vacuum chamber temp is plotted starting Feb 22 of 2005

This plot suggest that the MINCO temp controller is not working properly.

While Peter King is still working on the reference cavity temperature box, I turned the power supply for the reference cavity's heater back on. Rana turned it off last night since the ref cav temperature box had been removed.

I just switched it on and turned the current knob in the front panel until current and voltage got back to their values as in Rana's picture.

I plan to leave it like that for half an hour so that the the cavity starts warming up. After that, I'll turn the current back to the nominal value as indicated in the front panel.

It turned out that half an hour was too long. In less than that the reference cavity temperature passed the critical point when the temperature controller (located just below the ref cav power supply in the same rack) disables the input power to the reference cavity power supply.

The controller's display in the front shows two numbers. The first goes with the temperature of the reference cavity; the second is a threshold set for the first number. The power supply gets enabled only when the first number comes under the threshold value.

Now the cavity is cooling down and it will take about another hour for its temperature to be low enough and for the heater power supply to be powered.

 The cavity temp cooled below SP2 set point 0.1  The Minco SP1 (present temp in Volts) now reading -0.037 so DC power supply was turned on and set to 12V 1A  

Summary: This afternoon we managed to get the temperature control of the reference cavity working again.

We bypassed the MINCO PID by connecting the temperature box error signal directly into EPICS.

We couldn't configure the PID so that it worked with the modified temperature box so we decided to just avoid using it.

Now the temperature control is done by a software servo by using the channel C1:PSL-FSS_MINCOMEAS as error signal and driving C1:PSL-FSS_TIDALSET (which we have clip-doodle wired directly to the heater input).

We 'successfully' used ezcaservo to stabilize the temperature:

ezcaservo -r C1:PSL-FSS_MINCOMEAS -s 26.6 -g -0.00003 C1:PSL-FSS_TIDALSET

We also recalibrated the channels:

C1:PSL-FSS_RMTEMP

C1:PSL-FSS_RCTEMP

C1:PSL-FSS_MINCOMEAS

with Peter King on the phone by using ezcawrite (EGUF and EGUL) but we didn't change the database yet. So please do not reboot the PSL computer until we update the database.

More details will follow.

I stepped the TIDALSET and looked at what happened. Loop was closed with the very low gain.

The RED guy tells us the step/impulse response of the RC can to a step in the heater voltage.

The GREY SLOWDC tells us how much the actual glass spacer of the reference cavity lags the outside can temperature.

Since MINCOMEAS is our error signal, I have upped his SCAN period from 0.5 to 0.1 seconds in the database and reduced its SMOO from 0.9 to 0.0. I've also copied over the Fricke SLOW code and started making a perl PID loop for the reference cavity.