(Rana, Yuta)

Motivation:
 We wanted to see thermal effects on the PMC.

What I did yesterday:
 Changed the current of the NPRO from 2A to 0.8A and measured the power of the reflected/transmitted light from the PMC when locked.
 I also measured the power of the reflected light when PMC is not locked (It supposed to be proportional to the output power of the laser).

Result:
 Attached. Hmmmm......
 At several points of the laser current, I could'nt lock the PMC very well. The power of the reflected/transmitted light depend on the offset voltage of the PZT.
 When the laser power was weak(~<0.9A), the power of reflected/transmitted light changed periodically(~ several minutes).

It was a bit difficult to comprehend the result.
Is it good? or bad? Have you seen the thermal effect? or not?

- Put linear lines to show the visibility of the cavity.

- Calibrate the incident power and make another plot to show the visibility (%) vs the incident power (W).

We got two small RF filter for the PMC from Valera  They are made by http://www.larkengineering.com/   "MC35.5-3-AB" sma, 29300-01

Result2:
 Attached is the visibility vs incident power(assuming output of the PD is proportional to the input laser power).
 Ideally, the graph should be flat. (In another words, attached graph in the elog #3667 shoud be linear.)
 But the visibility reduces with higher laser power in this graph. This is maybe because of the thermal effect. I'm thinking about how to confirm this.

Innolight PSL laser is set to @2.1A , ~1.6W output ! Please scan out when finished! 

The output monitoring pick up window W2-LW-2-2050-UV-1064-45S is in place. IOO_ANG_OPD and IOO_POS_QPD roughly aligned.

The PMC alignment and/ or mode matching is bad. PMC reflected is 50%, throughput 600mW

Remember to block PSL output ! into IFO

 The NPRO at the PSL table still can generate 2W laser !  He is still alive.

  When I reduced the temperature to  25 deg, the output power increased to 2W successfully.

  As Steve wrote down in his last entry (see here), the NPRO output was at 1.6 W currently, which is supposed to be 2W.

We were suspicious about the laser crystal's temperature because the current temperature looks a bit high.

In fact the setpoint of the temperature was 45.9 deg instead of 25 deg that is the previous setpoint.

Background:
 I measured the PMC's visibility vs incident power relation last week to see the thermal effect, but I didn't calibrated the laser power(see elog #3672).
 So, I calibrated it on Oct 12.

Setup:
 Attachment #1
 The laser grade window PW-1025-UV-1064-45P had power reflectivity of about 0.5% in this setup.

What I did:
1. Calibrated the laser power(Attachment #2).
  To measure the laser power, I put the Ophir power meter at just in front of "PMC REFL PD".

2. For the calculation of the visibility K, I used the following formula;
 K= [1-(R1-R0)/(R2-R0)]*100
where R0, R1 and R2 are the PD outputs in voltage when laser is off, PMC locked and not locked respectively.

3. Plotted the visibility vs the incident power(Attachment #3).

Result:
 Attachment #2
  From the linear fit by least squares, the calibration turned out to be 1.12±0.07 mV/uW. The error of this value is calculated from assuming PD output error~1mV and laser power error~3uW for all measured value.
  The largest error was from the position and the angle of the power meter probe.

 Attachment #3
  I used the same data I took last week(see elog #3672), but better plot.
  I put the error bars for just several points. When the laser power is weak, the errors are large because of the cancellation error. When the laser power is high, the errors are estimated to be so small that you can't see it in the plot(~1%).
  At the several points, I couldn't lock the PMC well and  the power of the reflected light depended on the offset voltage of the PZT.
  The horizontal axis has about 6% error because of the calibration error.

Note:
 Now the condition is a bit different from this measurement(NPRO temperature changed, optics moved slightly), so the visibility may be changed.

I cleaned up the scattered tools, optics, and mounts of the PSL table. I gathered those stuffs at the two coners.

At the end of the work I scanned the table with an IR viewer. (This is mandatory)
I put some beam block plates to kill weak stray beams.

One thing I like to call the attention is:

I found that some beam blocks were missing at around the PBSs just after the laser source.
Those PBSs tend to reject quite a lot of beam power
--- no matter how the HWPs/QWPs are arranged.
--- even at the backward side. (remember that we have a faraday there.)

Particularly, there was no beam block at the forward rejection side of the first PBS where we dump the high power beam.

Be careful. 

[Suresh and Kevin]

We placed the quarter wave plate in front of the 2W laser and moved the half wave plate forward. To make both wave plates fit, we had to rotate one of the clamps for the laser. We optimized the angles of both wave plates so that the power in the reflection from the PBS was minimized and the transmitted power through the faraday isolator was maximized. This was done with 2.1 A injection current and 38°C crystal temperature.

Next, I will make plots of the reflected power as a function of half wave plate angle for a few different quarter wave plate rotations.

[Koji Suresh]

We found the beat at 1064nm. T(PSL)=26.59deg, T(X-end)=31.15deg.

The X-end laser was moved to the PSL table.

The beating setup was quickly constructed with mode matching based on beam profile measurements by the IR cards.
We used the 1GHz BW PD, Newfocus #1611-FS-AC.

As soon as we swept the Xtal temp of the X-end laser, we found the strong beating.

[Koji / Suresh]

We worked on the 1064 beating a bit more.

- First of all, FSS and FSS SLOW servo were disabled not to have variating Xtal temp for the PSL.

- The PSL Xtal temp (T_PSL) was scanned from 22deg-45deg while we search the Xtal temp (T_Xend) for the Xend laser to have the beat freq well low (f<30MHz).
The pumping current for each laser was I_PSL = 2.101 [A] and I_Xend = 2.000 [A]

For a certain T_PSL, we found multiple T_Xend because the freq of the laser is not a monotonic function of the Xtal temperature. (see the innolight manual).

T_Xend to give us the beating was categorized in the three sets as shown in the figure. The set on "curve2" is the steadiest one. (Use this!)
The trends were quite linear but the slope was slightly off from the unity.

- T_PSL was scanned to see the trend of the PMC output.

The PMC was sometimes locked to the mode with lower transmission (V_PMCT ~ 3.0V).
When T_PSL ~ 31deg we consistently locked the PMC at higer transmission (V_PMCT ~ 5.3V).

At the moment we decided the operating point of T_PSL = 32.25 deg, V_PMCT = 5.34, where we found the beat at T_Xend=38.28deg.

- We cleaned up the PSL table more than how it was. Returned the tools to their original places.
The X-end laser was shut down and was left on the PSL table.

NEXT:
Kiwamu can move the X-end laser to the Xend and realign it.
Then we should be able to see the green beating quite easily.

[Koji and Kevin]

We measured the reflection from the PBS as a function of half wave plate rotation for five different quarter wave plate rotations. Before the measurement we reduced the laser current to 1 A, locked the PMC, and recorded 1.1 V transmitted through the PMC. During the measurements, the beam was blocked after the faraday isolator. After the measurements, we again locked the PMC and recorded 1.2 V transmitted. The current is now 2.1 A and both the PMC and reference cavities are locked.

I will post the details of the measurement tomorrow.

I measured the reflected power from the PBS as a function of half wave plate rotation for five different quarter wave plate rotations.

The optimum angles that minimize the reflected power are 330° for the quarter wave plate and 268° for the half wave plate.

The following data was taken with 2.102 A laser current and 32.25° C crystal temperature.

For each of five quarter wave plate settings around the optimum value, I measured the reflected power from the PBS with an Ophir power meter. I measured the power as a function of half wave plate angle five times for each angle and averaged these values to calculate the mean and uncertainty for each of these angles. The Ophir started to drift when trying to measure relatively large amounts of power. (With approximately 1W reflected from the PBS, the power reading rapidly increased by several hundred mW.) So I could only take data near the minimum reflection accurately.

The data was fit to P = P0 + P1*sin^2(2pi/180*(t-t0)) with the angle t measured in degrees with the following results:

where V is the visibility V = 1- P_max/P_min. These fits are shown in attachment 1. We would like to understand better why we can only reduce the reflected light to ~150 mW. Ideally, we would have V = 1. I will redo these measurements with a different power meter that can measure up to 2 W and take data over a full period of the reflected power.

Q1. Suppose the laser beam has a certain (i.e. arbitrary) polarization state but contains only TEM00. Also suppose the PSB is perfect (reflect all S and transmit all P). What results do you expect from your expereiment?

Q2. Suppose the above condition but the PBS is not perfect (i.e. reflects most of S but also small leakage of P to the reflection port.) How are the expected results modified?

Q3. In reality, the laser may also contain some thing dirty (e.g. deporarization in the laser Xtal, higher order modes in a certain polarization but different from the TEM00's one, etc). What actually is the cause of 170mW rejection from the PBS? Can we improve the transmitted power through the PBS?

Q4. Why is the visibility for the lambda/4 with 330deg better than the one with 326deg? Yes, as I already explained to Kevin, I suppose it was caused by the lack of the data points in the wider angle ranges.

I copy section 6.2 into here to share with you all what the diagnostic capabilities of the new NPRO are. Its not a lot.

We'll need to record a sample of the NPRO output beam on a regular photodiode in order to get a real power monitor. My plan is to use a regular 25-pin Dsub and run it fron the NPRO controller over to the PSL rack and hijack the old MOPA monitoring channels (3113 and 3123 ADCs).

The laser power was attenuated to 40 mW yesterday for ensuring that the power built up within the MC does not damage the optics. 

This however stopped us from the doubling work and besides also reduced the power available for locking the PMC. 

Therefore, today the laser attenuation was removed and once again 500mW is available at the exit of the PMC .  

However the power sent to the MC has been reduced to 60mW by changing one of the mirrors in the zig-zag to a 33% beam splitter.  Though about 450mW is incident on the beam splitter the reflected beam is only about 55mW since the mirror reflectance is specified for P polarised light incident at 45deg while ours is S-polarised incident at less than 45deg.   The light transmitted through the beam splitter has been blocked by a beam dump.

[Rana and Kevin]

I made a low pass filter for the piezo driver for the 2W laser that is now installed. The filter has a pole at 2.9 Hz. The transfer function is shown in attachment 1.

Attachment 2 shows the outside of the filter with the circuit diagram and attachment 2 shows the inside of the filter.

[Koji and Kevin]

Since there was still a lot of power being reflected from the PBS before the Faraday rotator, I placed another PBS at the reflection from the first PBS to investigate the problem. If everything was ideal, we would expect the PBS to transmit P polarization and reflect S polarization. Thus, if the laser was entirely in the TEM00 mode, with the quarter and half wave plates we should be able to rotate the polarizations so that all of the power is transmitted through the PBS. In reality, some amount of P is reflected in addition to S reducing the power transmitted. (We are not sure what the PBS is since there are no markings on it but CVI says that their cubes should have less than 5% P reflection).

For the following measurements, the laser crystal temperature was 31.8° C, the current was 2.1 A, the half wave plate was at 267° and the quarter wave plate was at 330°. I first measured the power reflected from the first PBS then added the second PBS to this reflected light and measured the transmitted and reflected powers from this PBS with the following results:

This shows that approximately 81 mW of P polarization was being reflected from the first PBS and that there is approximately 48 mW of S polarization that could not be rotated into P with the two wave plates. Attachment 1 shows the shape of the reflected (S polarization) beam from the second PBS. This shows that the S polarization is not in TEM00 and can not be rotated by the wave plates. The transmitted P polarization is in TEM00.

We then rotated the first PBS (in yaw) to minimize the amount of P being reflected. Repeating the above measurement with the current alignment gives

Thus by rotating the cube to minimize the amount of P reflected, ~70 mW more power is transmitted through the cube. This adjustment moved the beam path slightly so Koji realigned the Faraday rotator and EOM. The PMC was then locked and the beam was realigned on the PMC. At 2.1 A, the transmission through the PMC is 6.55 V and the reflection is 178 mV. With the PMC unlocked, the reflection is 312 mV. This gives a visibility of 0.43.

Note by KA:
We realigned the beam toward the PMC at 1.0A at first so that we don't cook any parts. Once we get the TEM00 resonance, the steering mirrors were aligned to maximize the PMC transmission. Then the pumping current was increased to 2.1A.

At the PSL table I aligned the wideband EOM more carefully.

Amplitude modulation (AM) components in the main beam at 29.5MHz were successfully diminished by 24 dB. 

Last night when we were locking the MC, we noticed that the reflected light had AM which somewhat disturbes the Pound-Drever-Hall locking of the MC.

So I aligned the wideband EOM to reduce the AM components.

(method)

  In order to observe AMs I put a photodiode PDA255 whose bandwidth is 50MHz after the wideband EOM.

Before the PD I also put a convex lens together with a stack of ND filters and put a steering mirror to control the beam spot on the PD.

First I aligned the EOM such that the DC voltage from the PD was maximized. This process corresponds to a coarse alignment.

And then I tried reducing a peak at 29.5MHz seen in the spectrum analyzer. 

(results)

At the beginning the AM peak in the spectrum analyzer was at about -48 dBm.

After the alignment of the EOM it went down below the PD's dark noise floor of -72 dBm.

I checked the alignment also with an IR viewer, it looks quite good.

The box is electrically isolated from the optical bench.

Underneath the box there are four rubber legs and two Delrin plates (black and white) on the top of the box. 

As everyone knows this box is a prototype, so I will make another nicer box with a PCB in this November.

I moved the lens just before the PMC to check the mode matching landscape. The PMC trans went up from ~6.5 to ~6.8. That's 5% with ~1 hour of work.

As per the micrometer, this took ~7-8 mm of travel. Since there's so much power left in the HOMs, we we we will have to do a proper mode scan and re-calculate the solution.

The measured transmission is now ~610 mW. The power reflected from the PMC with it unlocked is ~1400 mW.

 The PMC mode matching was initially done at low power ~150 mW. It was expected and found that at full power ~2 W (injection current 2.1 A) the mode matching got much worse:

the visibility degraded from 80% to 50% (1 - refl locked/refl unlocked) . The thermal lensing could be in the laser, EOM, or FI.

The first attached plot shows the scan of the beam after the EOM at low and full laser power. At full power the waist position is 10 mm after the turning mirror after the EOM and the waist size is 310 um.

The second plot shows the ABCD calculation for the mode matching solution.

I removed the MM lens PLCX-25.4-77.3-C and placed the PLCX-25.4-180.3-UV about 20 mm after the first PMC periscope mirror (the second mirror after the EOM).

The PMC visibility improved to 94% and the power through the PMC, as measured by the PMC transmission PD, went up by a factor of 2.

I maximized the laser power by rotating the HWP after the NPRO.

If someone works on the MC locking, one should decrease it again.

Has C1PSL rebooted? Has burtrestore been forgotten? Even without elog?

We found some settings are wrong and the PMC has pretty low gain.

Yeah. Joe and I rebooted c1psl a couple of times this morning. I didn't realize the burtrestore wasn't automatic.

[Valera Yuta Kiwamu Koji]

Kiwamu burtrestored c1psl. We measured the power levels around the PMC.

With 2.1A current at the NPRO:

Pincident = 1.56W
Ptrans_main = 1.27W
Ptrans_green_path = .104W

==> Efficiency =88%

----

We limited  the MC incident power to ~50mW. This corresponds to the PMC trans of 0.65V.
(The PMC trans is 1.88V at the full power with the actual power of 132mW)

Valera and Haixing and I installed a PMC REFL camera today. We stole the camera control box from the MC2 trans area (because I don't know why we need a camera there).

We installed it such that it is looking at the leak through of the last turning mirror before the PMC REFL RFPD. This beam was previously going into a Thorlabs razor blade dump.

There is no steering mirror to align into this camera; we just positioned the camera such that the REFL beam fills up the monitor. WE cable tied the cable to the table and the

output of the camera control box is piped into the control room correctly as PMCR. The "IMCR" quadrant is actually the PMCT beam. JoonHo is going to fix this promptly.

Also, I noticed how beautiful  the MC2 Simulink diagram is so I post it here for your viewing pleasure. We should take this as a reference and not produce any new diagrams which are less useful or beautiful or easy to understand.

I ramped the PMC gain slider to find where it oscillates. It starts going bad at ~13 dB, so the new default gain is 7 dB to give us some margin for alignment improvements, etc.

I also fixed the TIME field in our MEDM screens by adding the following text to the C1IFO_STATE.db file which runs on c1iscaux:
grecord(stringin, "C0:TIM-PACIFIC_STRING")
{
    field(DESC, "Current time and date")
    field(DTYP, "EPICS IOC VAR")
    field(SCAN, "1 second")
    field(INP, "C1:FEC-34_TIME_STRING")
}

grecord(stringin, "C0:IFO-TIME_PACIFIC")
{
    field(DESC, "Current time and date")
    field(DTYP, "EPICS IOC VAR")
    field(SCAN, "1 second")
    field(INP, "C1:FEC-34_TIME_STRING")
}
This gets the time info from the c1ioo processor via channel access and gives it these mroe reasonable names. The first record is for backwards compatibility. The second record is a better name and we should use it in the future for all new screens. I had to reboot c1iscaux several times to figure out the right syntax, but its OK now. You have to reopen stale screens to get the field to refresh.

This avoids the previous idea of changing all of the MEDM screens.

[Rana, Jenne, Suresh]

Yesterday, We replaced the existing beam steering mirror and the PZT it was mounted on with a Gooch and Housego mirror (20ppm transmission at < 30deg incidence @1064nm) and a Polaris-K1 Newport steel mount. (JD)

We realigned the G&H mirror to get the MC flashing. 

We then had to reduce the gain in the servo circuit to accommodate the increased optical power going into MC. 

MC locked to PSL once again.

Note: 

      the old mirror stuck on the PZT has been removed.  The mirror had no markings and has been stored in the 'Unknown Optics' Box along the East Arm.

      The PZT has been stored in the PZT cabinet along with its 2in mirror mount.

Back in the days when we were talking about getting a new 2W PSL, I was given naming rights by Rana for this new laser. 

Today, the 40m PSL was given its new name: Edwin.

Here he is, with his shiny new label:

I noticed that the RMTEMP channel was spiking myteriously when Kiwamu opened the PSL door. We found out that the LEMO connectors would intermittently short to the case and cause ~1 deg steps in the temeprature.

We have removed the case and examined it. Not only were the connections to the box intermittent, there was a cold solder joint inside on an unsecured flying add-on opamp. The whole thing is a giant hack.

PK was the last person to work on this box, but I'm sure that he wouldn't have left it in this state. Must be gremlins.

The LEMO connectors on the front are the ones touching. The LT1021 is the badly soldered part.

 We swapped the PMC s/n 2677 for s/n lho006.

The table below summarizes the power levels before and after the PMC swap.

- The power into the PMC (1.67 W) was measured with Scietech bolometer before the first steering PMC mirror. The leakage through the steering mirrors was measured with Ophir power meter to be 12+8 mW. There is also a lens between the mirrors which was not measured. 

- The power through the PMC was measured after the doubler pick off (105 mW), steering mirror (4 mW), and lens (not measured).

- The estimated reflection from four lens surfaces is 1-2% hence 1% uncertainty in the losses in the table.

- The beams into the PMC and on REFL PD were realigned. The beams downstream of the PMC are blocked as we did not realigned the PMC and doubler paths.

- The trans PD ND filters were removed. The VDC=1.28 V now.

- The NPRO current is 2.102 A

Atm 1 old

Atm2  new

Uniblitz mechanical shutter was placed into the beam path of the PSL output with razor beam trap. The output power was 1.39W at 2.08A

It is working from the MEDM screen "old map" C1IOO_Mech_Shutter.adl

Its been well noted in the past that sweeping the PMC at high power leads to a distortion of the transmitted power curve. The explanation for this was coating absorption and thermo-elastic deformation of the front face of the mirrors.

Today, I did several sweeps of the PMC. I turned off its servo and tuned its PZT so that it was nearly resonating. Then I drove the NPRO via the HV driver (gain=15) with 0-150 V (its 1.1 MHz/V) to measure the PMC transmitted light. I adjusted the NPRO pump diode current from 2A on down to see if the curves have a power dependent width.

In the picasa web slideshow:

There are 3 significant differences between this measurement and the one by John linked above: its a new PMC (Rick says its the cleanest one around), the sweep is faster - since I'm using a scope instead of the ADC I feel free to drive the thing by ~70 MHz in one cycle. In principle, we could go faster, but I don't want to get into the region where we excite the PZT resonance. Doing ~100 MHz in ~30 ms should be OK. I think it may be that going this fast avoids some of the thermal distortion problems that John and others have seen in the past. On the next iteration, we should increase the modulation index for the 35.5 MHz sidebands so as to get a higher precision calibration of the sweep's range.

By eye I find that the FWHM from image #4 is 11 ms long. That corresponds to 300 mV on the input to the HV box and 15 V on the PZT and ~16.5 MHz of frequency shift. I think we expect a number more like 4-5 MHz; measurement suspicious.

PMC TRANS/REFL on MEDM showed red values for long time.
TRANS (a.k.a C1:PSL-PSL_TRANSPD) was the issue of the EPICS db.

REFL (a.k.a. C1:PSL-PMC_RFPDDC) was not physically connected.
There was an unknown BNC connected to the PMC DC output instead of dedicated SMA cable.
So they were swapped.

Now I run the following commands to change the EPICS thresholds:

ezcawrite C1:PSL-PMC_PMCTRANSPD.LOLO 0.8
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOW 0.85
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIGH 0.95
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIHI 1

ezcawrite C1:PSL-PMC_RFPDDC.HIHI 0.05
ezcawrite C1:PSL-PMC_RFPDDC.HIGH 0.03
ezcawrite C1:PSL-PMC_RFPDDC.LOW 0.0
ezcawrite C1:PSL-PMC_RFPDDC.LOLO 0.0

As these commands only give us the tempolary fix, /cvs/cds/caltech/target/c1psl/psl.db was accordingly modified for the permanent one.

grecord(ai,"C1:PSL-PMC_RFPDDC")
{
        field(DESC,"RFPDDC- RFPD DC output")
        field(DISV,"1")
        field(SCAN,".1 second")
        field(DTYP,"VMIVME-3113")
        field(INP,"#C0 S32 @")
        field(EGUF,"10")
        field(EGUL,"-10")
        field(EGU,"Volts")
        field(PREC,"3")
        field(LOPR,"-10")
        field(HOPR,"10")
        field(AOFF,"0")
        field(LINR,"LINEAR")
        field(LOW,"0.0")
        field(LSV,"MINOR")
        field(LOLO,"0.0")
        field(LLSV,"MAJOR")
        field(HIGH,"0.03")
        field(HSV,"MINOR")
        field(HIHI,"0.05")
        field(HSV,"MAJOR")
}

grecord(ai,"C1:PSL-PMC_PMCTRANSPD")
{
        field(DESC,"PMCTRANSPD- pre-modecleaner transmitted light")
        field(DISV,"1")
        field(SCAN,".1 second")
        field(DTYP,"VMIVME-3123")
        field(INP,"#C0 S10 @")
        field(EGUF,"10")
        field(EGUL,"-10")
        field(EGU,"volts")
        field(PREC,"3")
        field(LINR,"LINEAR")
        field(HOPR,"10")
        field(LOPR,"-10")
        field(AOFF,"0")
        field(LOW,"0.8")
        field(LSV,"MINOR")
        field(LOLO,"0.85")
        field(LLSV,"MAJOR")
        field(HIGH,"0.95")
        field(HSV,"MINOR")
        field(HIHI,"1.00")
        field(HSV,"MAJOR")
}

Solid door, numbered 4 at south west corner of PSL enclosure was replaced by laser protective window.

The carpenter shop's Mark is making 4 more identical ones for the east side.

The Lightwave NPRO126 of 700mW was moved from the AP-table into the PSL-enclosure temporarily.

It's emergency shutdown switch can be seen at the center bottom picture

I (think) I have finished the new PMC base riser.  The eDrawing of it (so you can view it on any computer) has been uploaded to the PMC wiki page.

I also attach it here, for comments.

Its going to need some kind of way to locate the PMC on the top. In the previous design, we had the 3 balls to decouple the body from the base. That design was flawed due to the roughness of the holes in the PMC body.

Also probably need some kind of relief on the bottom. Its possible that it would be OK like this, but I am unsure if the shop can maintain the flatness we want over the whole length and/or the flatness of any given (OLD) optical table over ~8". Its probably not a good idea to have to torque this (aluminum?) to make it conform to the optical table's shape.

 Hmmm, so, this was just meant to be a riser that goes underneath the old PMC mount, to raise it from 3" beam height to 4" beam height.  I will make another one that is a complete mount, designed for 4" beam height.  Please hold........... .......... ....... ..... ... .

The PSL enclosure now have 4 windows on each side. The bottom rail guides on the east side will be replaced by  one  U-channel for smoother, more gentle sliding.

Door position indicator- interlock switches are not wired yet.

Valera and I installed the the temp sensor and the interface box that Rana fixed. This may help with diagnosing the PSL drift.

eeek.  I've been running around all day, so this is an incomplete elog.  I'll fill in more stuff in the next hour or so, but just to let people know what's going on:

[Valera, Jenne]

Valera noticed that lots of things in and around the PSL table are drifting with temperature.  This is why he and Steve installed a temp sensor on the table earlier today.

Since the alignment into the PMC, and also the alignment downstream of the PMC have been drifting in angle, we supposed that it might be the PMC itself which is changing somehow with temperature.  We don't have a good idea of how exactly it is sensitive to temperature, but we're working on figuring it out.

Round 1 of testing:  We put a foil hat over the PMC to shield it from the HEPA air blowing directly down on top of it.  I made sure that the foil is also covering the PZT and the metal ring at the end of the PMC, because this could potentially be the problem (metal is usually more temperature sensitive than glass, or the PZT itself could be changing, either of which could make the end mirror twist, and change the alignment of the PMC).  We'll see later if this did anything useful or not. 

I have photos of the aluminum foil setup, which I will post later when I get back to the lab after teaching. 

 I was wrong. Rana did not fix the interface box. I removed the interface box and turned down the HEPA flow  from 100 to 20% on the Variac.

The PMC exhibited the reduction of the transmission, so it was aligned.

The misalignment was not the angle of the beam but the translation of the beam in the vertical direction
as I had no improvement by moving the pitch of one mirror and had to move those two differentially.

This will give us the information what is moving by the temperature fluctuation or whatever.

I looked at the PSL temperature box. It started out as D980400-B-C. Then it was revised by Peter King as per the LHO mods E020247.

There are some more things to do to it to make it useful for us:

1. R3, 4, 7, 8, 12, & 13 should be changed from 1k to 0 Ohms, I think. I cannot figure out their purpose.
2. All resistors should be made metal-film. Right now, its kind of a mish-mash.
3. The active filter U6B has a corner frequency of ~50 Hz. This seems not useful for keeping the 4116 DAC noise out of the temperature. We should lower this to ~30 mHz to take advantage of the stability of the LT1021 which was put in.

** Frank reminds me that we don't use the TIdal or VME external inputs anymore since we moved to the EPICS/Perl PID control. So all we have to do is make sure these inputs are hardware disabled/disconnected.

The attached plot shows 7 day trends of the MC and PMC power levels, PSL QPDs, and temperature. The MC stayed locked for ~40 hours over the weekend. The temperature swings were somewhat smaller over the past couple of days but one should remember to turn the PSL HEPA down after working on the table. Steve turned the HEPA flow from 100% down to 20% on Thursday and posted the reminder signs on the PSL enclosure.

[Valera, Joe]

Software Changes:

First we changed all the C1:IOO-QPD_*_* channels to C1:PSL-QPD_*_* channels in the /cvs/cds/caltech/target/c1iool0/c1ioo.db file, as well as the /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini file.  We then rebooted the frame builder via "telnet fb 8087" and then "shutdown".

This change breaks continuity for these channels prior to today.

The C1:PSL-QPD_POS_HOR and C1:PSL-QPD_POS_VERT channels were found to be backwards as well.  So we modified the /cvs/cds/caltech/target/c1iool0/c1ioo.db file to switch them.

Lastly, we changed the ASLO and AOFF values for the C1:PSL-QPD_POS_SUM and the C1:PSL-QPD_ANG_SUM so as to provide positive numbers.  This was done by flipping the sign for each entry.

ASLO went from 0.004883 to -0.004883, and AOFF when from -10 to 10 for both channels.

Hardware Changes:

The C1:PSL-QPD_ANG_SUM channel had been saturated at -10V.  Valera reduced the power on the QPD to drop it to about 4V by placing an ND attenuator in the ANG QPD path.

I re-installed the box (@ ~8:15) after reflowing some of the solder joints. I will observe it over night and then remove the 1K resistors. Attached is a 8 hour minute-trend.

I added calculation entries to the /cvs/cds/caltech/target/c1iool0/c1ioo.db file which are named C1:IOO-QPD_*_*, as the channels were originally named.  These calculation channels have the identical data to the C1:PSL-QPD_*_* channels.  I then added the channels to the C0EDCU.ini file, so as to once again have continuity for the channels, in addition to having the newer, better named channels.

The c1iool0 machine ("telnet c1iool0", "reboot") and the framebuilder process ("telnet fb 8087", "shutdown") were both restarted after these changes.

These channels were brought up in dataviewer and compared.  The approriate channels were identical.