i disconnected all signal from the PSL RT system running on fb0 this afternoon, so this model doesn't have to run anymore.
They are all hooked up to the VME system now.

I will remove the configuration file for those channels from the fb0 framebuilder the next day. Right now it's still running but not used anymore...

i replaced some cables going from the 9-pin D-SUB connection block connecting the VCO with the DAQ by bi-colored, twisted ones.
Someone used yellow cables for everything when he set this up. Now the ADC and DAC channels are bi-colored (black-LO, yellow-HI).

I also removed one connection from ground to the rack frame, so protective earth. I don't see why we need that as we have one at the power supply already. There ground=earth.

i've killed the PSL RT frontend. Everything else should be ok, so plz check if everything is working.

To test the temperature stability of our cavities, Frank and I decided to run the heat gun at 800 degrees Fahrenheit for a bit of time. Coincidentally, this is the perfect temperature for roasting marshmallows. Complete coincidence, of course. After setting up a stable marshmallow roaster, er, heat gun,

we roasted marshmallows successfully (with the help of Zach) for a little while.

While this was a successful test for our tastebuds and need for sugar, the impact on the cavities is uncertain, and so this entire setup should probably be tested again. Including the marshmallows.

i updated the database for epics channels for the PSL lab and restarted the framebuilder on fb1.
I didn't restart the framebuilder on fb0, but once it will be restarted it' will load the new channel list too.

I saw that something seems to be wrong with the network as we have several lost packets which also shows up in the saved data.
I will investigate this later as it seems to be a problem for the slow channels from the PSL lab only.

changed setpoint for ACAV to 37.2 degrees, disabled the FSS loop and enabled feedback to laser temp using VCO input signal (C3:PSL-ACAV_VCOMON)

RCAV resonant at -0.1154,  AOM centered at -0.0987

changed the ACAV temp to 37.3 degrees. Both cavities are locked now.

I'll monitor the VCO input signal to center the range by adjusting the temp a little bit more.

i lost lock of both cavities for some unknown reason. Also the crate seemed to stop working as some channels are dead now...

relocked both cavities. The second crate containing the output card to control the ACAV power supply stopped working and i can't login from here. It's blocking the telnet request.

So Tara, plz reboot the crate in the other "rack", above the SR785. Simply push the reset button... Thanks

Dmass helps me initializing two channels for DAQ.

PSL1 connected to channel 28 which is C2:ATF-ACCoup_AC2_OUT_DAQ

PSL2 to channel 29 which is                    C2:ATF-ACCoup_AC3_OUT_DAQ

rebooted the crate.

plz change the channel names. Those names are bullshit...

  I use COMSOL to simulate the temperature distribution inside the mirror. 

The mirrors are separate into 3 regions for different meshing quality see attached figures.

This model assume 0.95 emissivity on the surface, and 310 K at the surface between the mirror and the spacer.

The temperature between 10 mW and 10mW + RIN*10mW is plotted and fitted with polynomial function of order 9.

*the unit of y axis on fig3 is Kelvin

The Temperature difference will be applied to the coating surface and calculated the upper limit for photo thermal noise. 

The function is

T = p1*z.^9 + p2*z.^8 + p3*z.^7 + p4*z.^6 + 

    p5*z.^5 + p6*z.^4 + p7*z.^3 +

    p8*z.^2 + p9*z + p10;

       p1 =  -5.335e-10 ; %(-5.806e-10, -4.864e-10)

       p2 =   1.602e-08 ;% (1.474e-08, 1.731e-08)

       p3 =  -2.041e-07 ;% (-2.188e-07, -1.894e-07)

       p4 =   1.438e-06 ;% (1.347e-06, 1.528e-06)

       p5 =  -6.144e-06  ;%(-6.47e-06, -5.818e-06)

       p6 =   1.645e-05  ;%(1.576e-05, 1.715e-05)

       p7 =  -2.773e-05  ;%(-2.858e-05, -2.687e-05)

       p8 =   2.912e-05  ;%(2.857e-05, 2.967e-05)

       p9 =  -1.893e-05  ;%(-1.908e-05, -1.877e-05)

       p10 =   7.548e-06 ;% (7.534e-06, 7.562e-06)

I was measuring the power fluctuation behind PMC and RCAV, during that the beam was not locked and the medm screens were frozen, so I restarted the crate.

  C3:PSL-ACAV_TEMPAVG that tells the average temperature from ACAV is dead. Frank told me to reboot the PSL crate.

                                       RCAV      ACAV

C3:PSL-XXXX_SETPT      35.0       36.75

C3:PSL-XXX_HEATER    1.47521   4.9

I rebooted the crate, reload the cavity.stp file, the channel is still inactive. (only this channel)

set temp for the ACAV should be 37.3, that was the value since about a week. see here : http://131.215.115.52:8080/PSL_Lab/307

 I measured RIN from beam behind PMC and RCAV. Photodiodes are connected to SR785 and measured at the same time. 

DC level from PMC and RCAV are 3.56 V and 1.58 V, respectively.

The HEPA filters above the table were turned off during one measurement to see how much it would effect the RIN (turn out to be not that much)

Only PMC and RCAV were locked during the measurement.

The results are plotted together with RIN from 40m's RCAV ( 40m elog. ) PSL has lower noise at lower frequency f< 50Hz, and about 1.5 order of magnitude higher

between 50Hz to 10 kHz. 

I haven't tried to optimize any cavities yet. This is just walk-in,plug-in and measure as a reference for the current setup.

if I try to re-center the beam into the cavities, the result might be better (or worse).

 I think ants are now building their colony in the lab, even though there is no garbage, they can find some food around here.

That seems like a cricket's leg (see attached pic). A few of them walk around the optic table/ optics too.

I think we should let an aardvark roam around the lab for a day.

any results from the poison from 40m they tried in the TCS lab? Did it work?If yes we should get some for the other labs too....

Yesterday, I reset the PSL crate behind the SUN computer, but the channel C3:PSL-ACAV_TEMPAVG is stil inactive.

looks like some fault of the database. /usr1/epics/psl/db/acav.db does not contain the correct entry. check rcav.db and copy the record for "C3:PSL-RCAV_TEMPAVG" into acav.db. Then simply change "RCAV" into "ACAV" everywhere for this record. Also change the setpoint for the ACAV in the startup.cmd file to 37.3 and the ACAV-heater value to 4.653. Those are the latest values when both where locked for several hours. Reset the crate again.

 Will do in a moment, I'm taking data from ACAV for now just to compare with yesterday results.

made the changes a minute ago. simply reboot after changing the values in the startup.cmd (those i didn't change)

be carefull with the data you are taking right now. it's wrong for your projection as the power fluctuations are different when locking only the ACAV using the AOM. The largest contributor might be the pointing from the AOM itself, which is different if the laser isn't locked to the other cavityat the same time.

Why don't you use the new fast channels you have hooked up last week? And don't forget to change the names of those :-)

can you plz check this channel as it is constantly at -14.4797 since yesterday. Did you disconnect it? If yes, plz elog those things!! Everything must be eloged

if you wanna measure anything in the ACAV loop without the RCAV locked, don't forget to DISABLE the FSS loop.
If you don't, your measurements will be shit as the PC is fluctuating like hell making the laser noisy which can't be handled by the other loops due to limited bandwidth...

 I didn't do anything on that channel. I just removed the BNC cable that connect to a T behind the PD and connected it to an oscilloscope this afternoon. I'll take a look.

was it grey? If yes the cable already connected to the T is the cable going to the DAQ. That's why there is a T already. Don't disconnect any signals without checking in advance what they are and what they are used for. Some of them are required for locking, e.g. the transmitted light is required for the servo as a feedback if it is locked or not for the temp feedback. If you have to disconnect anything do it but put an entry in the elog.

 No, it's the black one that goes to a multimeter. The grey cable to DAQ is untouched.

 I didn't disabled the loop when I measured it, and yeah it looks bad. I think I'll just try to lock both cavities for now.

I'll connect the signals from PDs behind Rcav and Acav to the new fast channels(32k).

About changing the channels' names, I asked DMASS to help and he suggested to use them as they are for now because of the risk of screwing the system up from a typo.

 I checked the beam. It hit the PD and gives ~500 mV output when only ACAV is locked. when I disconnected the grey cable that connects the PD to DAQ, the

value is still the same (-14.5).

The connection at DAQ looks good.

The cable is good, the signal can go through.

I thought 0the setup in  RCAV.db and ACAV.db files were wrong so I changed it to the red values

                             rcav.db                     acav.db

field DTYP        VMIVME-3113          VMIVME-3123 ->VMIVME-3113

INP                   #c0 S61@                     #c0 S1@  -> #c0 S62@

 ,and now it's working.

I remember changing these before Frank went to Hanford, I might not save the file. Anyway, now I saved it.

The fluctuation in VCOMON goes down to less than +/- 1V.

I adjust SLOWDC to see what value to lock each cavity.

For ACAV I adjust SLOWDC so that VCOMON fluctuates around 0 and record the value of SLOWDC

I adjust ACAV_SETPT to see how the DC changes (in RED), it seems I have to reduce the ACAV_SETPT

                             ACAV                              RCAV

SLOWDC       -0.1118 ->-0.1151             -0.1051

SETPT           37.3      -> 37.35                       35

Now, ACAV_SETPT is changed to 37.15, but ACAV_TEMPAVG goes up (after 30mins.) to ~37.43 (from 37.3).

The variance from ACAV's 4 temp sensors are getting larger.

don't change anything until it is stable and you thought about it carefully. The system was totally out of control, check the dataviewer!.
So there is no way to make an estimate for the values as you have no equilibrium!! That takes several hours after ANY change to the system, like rebooting the crate or turning on a temp control loop.
Remember: time constants are several hours!

So be patient and wait until tomorrow or late tonight before you make estimates and changes. Both temperatures are NOT close to their original setpoint and largely fluctuating.
RCAV is at 34.8 instead of 35 and ACAV changed from 37.1 to 37.45 within the last hours.
So no way to make the right adjustments right now, as your laser SLOWDC value does not reflect the actual temperature of the chamber.

Changed it back to the original settings (37.3) as those were working over several days before the system stopped working properly...

 Frank, did you remotely change ACAV_SETPT back to 37.3? I came back and it was back to 37.3.

i tried to figure out where the network problems come from. Looks like it's the fiber connection between fb1 and the switch in the PSL lab.

Here a result from a simple ping between fb1 and the other computers. It acrually doesn't matter which one.

--- 10.0.0.1 ping statistics ---
1000 packets transmitted, 817 received, 18% packet loss, time 201397ms
rtt min/avg/max/mdev = 0.169/0.233/0.381/0.025 ms

--- 10.0.0.2 ping statistics ---
1000 packets transmitted, 786 received, 21% packet loss, time 202036ms
rtt min/avg/max/mdev = 0.617/0.694/2.658/0.152 ms

--- 10.0.0.3 ping statistics ---
1000 packets transmitted, 796 received, 20% packet loss, time 201696ms
rtt min/avg/max/mdev = 0.410/0.453/2.655/0.081 ms

Pings between computers within the PSL lab but connected to the same switch are OK:

--- 10.0.0.1 ping statistics ---
1000 packets transmitted, 1000 received, 0% packet loss, time 202998ms
rtt min/avg/max/mdev = 0.000/1.092/13.755/1.340 ms

--- 10.0.0.2 ping statistics ---
1000 packets transmitted, 1000 received, 0% packet loss, time 203161ms
rtt min/avg/max/mdev = 0.200/1.719/13.230/1.545 ms

So i think it's the fiber connection.

 

 A tentative layout for almost symmetric layout for beat measurement. The double 1/4 objects  in the beam paths should be 1/4 and 1/2 waveplates.

Lenses might be used to focus the beam somewhere.

   Temperature on both cavities are fairly constant over -8 hrs, still can't simultaneously lock both cavities.                        

                              ACAV                      RCAV

XXX_SETPT          37.3                       35.0

XXX_TEMPAVG        37.301                 34.997

SLOWDC              -0.11645 (VCOMON center @ 0),    -0.1114

XXX_HEATER      4.72971              (FSS)1.49154

Since everything is stable now, I'll lock RCAV and adjust ACAV temperature to lock them together withing AOM range.

I'll change ACAV_SETPT from 37.3->37.4, to see how SLOWDC has to change to lock ACAV.

Wed Sep 01 21:04:24 2010

After 6 hrs, ACAV_TEMPAVG is stable around 37.4 C.

SLOWDC for ACAV is -0.1200 (VCOMON center @ 0)

 This means For ACAV, dV(slow dc) per dT(ACAV) = (0.1203-0.11645)/0.1 = 0.039 V/K.

Since RCAV is locked when SLOWDC = -0.1114, we have to decrease the temperature from 37.4 C by (0.1203 - 0.1114)/0.039 = 0.2282 K.

That is 37.4 - 0.2282 = 37.1718.

Now I set ACAV_SETPT to 37.2 C.

ACAV_TEMPAVG still adjusting it self to 37.2 (SETPT)  three overshoots in the last 8 hrs (+/-0.01 C)

                     ACAV                   RCAV

SETPT             37.2                  35

TEMPAVG    37.215               35.005

SLOWDC       N/A            -0.10932

VCOMON              1.11 V

*RCAV_TEMPAVG is very noisy compared to ACAV_TEMPAVG

ACAV's PD for transmitted beam is connected to PSL1

RCAV's PD for transmitted beam is connected to PSL2

And now RCAV_RCTRANSPD dropped from ~5.3 to ~5.05

               ACAV_RCTRANSPD dropped from  ~2.5 to ~2.4

50 mins ago, medm on Sun machine is frozen, most channels are inactive (except  ACAV_HEATER, and it goes up to 7 which is the maximum value). 

I reboot the PSL crate, but ACAV_HEATER is still at 7 and heat up ACAV to 39 C.

So, I realized that I had to reboot another crate. Now ACAV_HEATER is at 4.6 and decreasing.

Now the system should try to bring the temperature back and might take many hours.

 When both cavities are locked, I measured

1) power fluctuation behind ACAV (DC@0.55V) and RCAV (DC@2.2V)

2) power fluctuation behind PMC (DC@3.17V)and RCAV (DC@2.2V)

the HEPA filter was on, the SLOWDC loop was engaged.

SR785 is set to AC couple mode, auto range on both channels.

The level of RIN from RCAV from two measurements are a bit different,see fig2.

RIN from ACAV is not significantly higher than that of RCAV. This is good news, I thought AOM might pose more pointing instability to the system.

 Frank showed me that the RIN level from PMC is too high and caused by back reflection. 

PMC's psd is reduced by blocking the beam going to ACAV and RCAV.  This can be seen

on SR785, by blocking the beam.

So I removed PBS in front of the laser, and replaced it with a Faraday isolator. 

The isolator is temporarily mounted on a post, we will use a more rigid  V-shape block holder later.

The isolator shifts the beam path a bit, and the beam is needed to be re-align to the PMC. 

I couldn't finished it by Friday night, I think Frank re-aligned it already.

I'll measure RIN  and compare them again.

 SInce the Faraday isolator alter the beam path and beam profile a bit. The mode matching efficiency drops.

I only realigned the beam to PMC and RCAV. Lenses before PMC haven't been moved yet.

                    efficiency (P_in/P_out)              DC level (from PD behind the cavity)

PMC        18.2mW/27.9mW = 65%                   2.5V

RCAV       4.56/4.94 [mW]  = 92% (this drops from ~96%)    1.3V

pmc_n and rc_n (blue/green) were taken together with Faraday isolator installed .

pmc and rc with no isolator (purple/brown) are data from Aug 30, 2010.    

pmc blocked (red)  is PMC RIN when the beam after the PMC is blocked, RCAV loop disabled, SLOWDC control is disabled.

There is no significant change here, I have to think about it.

 Today I investigated which optics reflect most power back to the PMC and the laser.

The back reflection seems to limit our sensitivity.

the power meter is placed to measure the reflected light that comes back and reflects off the PMC's mirror.

The beam path to the ACAV is blocked and ignore for now, since AOM in the path will act as an optical isolator.

The reflected power from this path will be smaller than that of Rcav's path.

periscope [M]  1/4&PBS  [L]  PLCX     [K]    Mirror

                                                                        [J]

                                                                      1/4

                                                                        [I]

                                                                       1/2

                                                                       [H]

                                                                    PLCX

                                                                      [G]                                                                                                         

                                             Blocked           PBS  [F]  PLCX [E]   1/2 [D]  EOM [C] PLCX  [B]   1/2 [A]      \  pmc  / <---- beam

                                                                                                                                                           power meter

A razor blade beam dump was placed at each position (alphabet in square brackets).

The red entries corresponds to second set of data after realignment

A

B 52.3 uW           49.2 uW 

C 0.184 mW        0.184mW

D 0.748 mW        0.745 mW

E 0.748 mW        0.752 mW

F 0.749 mW         0.754 mW

G 0.831 mW

H 0.831 mW

I 0.831 mW

J  0.831 mW

K 0.831 mW

L 0.831 mW           0.88 mW

M 0.831 mW          0.88 mW

reflection from RCAV     1.53  mW     1.96mW

It seems that the reflection from the cavity is giving us a hard time.

The PBS with 1/4 plate might not well adjusted to minimize the back reflection.

After I minimized it by tilting/rotating the PBS, the PBS was tilted around 5 degree  (judging by my eyes) and it looked bad.

The beam is almost clipped on the edge, and Frank noticed that the beam height was not right.

I realigned the beam again (the efficiency is ~97%).

Unfortunately, I lost the beam so much I had to remove a few optics ( 2 mirrors adjacent to the RCAV) behind RCAV,

and used a CCD camera to see the beam while adjusting the knobs. I placed the optics back, but

I haven't adjusted the beam path for beat measurement yet.

Now the PBS is quite flat on the table.

I  measured the power reflected at each optic again (see red entries in the table above.)

I rotated the PBS to see if the power reflected from RCAV can be reduced. It turns out that

I couldn't do much, only from 1.96 - > 1.93 mW.

after a lot of test it turned out that the optically contacted QWP/PBS combinations used for the reference cavity so far are very bad alligned.
We tested two out of three we have in the PSL lab and both are bad, meaning about 10% of the linear polarized light entering the PBS are not converted into circular polarized light and so not reflected when comming in the reverse direction. By replacing the optically contacted version by individual PBS and QWP the amount of wrong light dropped by a factor of 100 or so.

Replacing the bad optics should reduce the effect from backscattered/reflected light, which increases the RIN a lot at low frequencies. It doesn't seem to be the laser itself, as with none, one or two FI the spectrum seems to be the same bad level when light is reflected back into the PMC. It looks like the source is the PMC itself or it's control loop.

So, Tara is replacing the bad ones and re-aligning everything. Temp is good, both cavities are resonant at the same time so i hope we can get new/better data tomorrow.

i have several channels, e.g "C3:PSL-RCAV_RCPID_SETPOINT", loaded on the VME system as software channels.

If i try to access those channels from the VME console everything is fine.

psl1> dbpr "C3:PSL-RCAV_RCPID_SETPOINT"
ASG :               DESC: SETPT- set point                  DISA: 0            
DISP: 0             DISV: 1             NAME: C3:PSL-RCAV_RCPID_SETPOINT       
OMOD: 0             OVAL: 0             RBV : 0x0           RVAL: 0x0                 
value = 0 = 0x0

If i try to use commands from any other machine, e.g. ezcaread for the same channels i get the message  "channel not accessible".
At the same time the VME system throws the following exception on the console.

psl1> task: 0Xca8f00 CA client
Illegal Lock Set Lock Set out of range:dbScanLock
task: 0Xf9f7f8 taskwd
task ca8f00 CA client suspended

This only happens to some channels. I don't see a system except that the channel names are long, but not longer than working ones. For R3.13 the name must be <= 28 characters, For R3.14 the name must be <= 60 characters.

What's the problem?

We have used an instant PBS/QWP which is a PBS optically contacted to an aligned QWP in front of a reference cavity

(for PDH locking and optical isolation.) It cannot properly block the reflected beam, so certain amount of power got reflected back to

the PMC and back to the laser. This causes higher value of RIN. ()

We have used an instant PBS/QWP which is a PBS optically contacted to an aligned QWP in front of a reference cavity

(for PDH locking and optical isolation.) It cannot properly block the reflected beam, so certain amount of power got reflected back to

the PMC and back to the laser. This causes higher PMC's RIN. (When the beam path behind the PMC is blocked, no back reflection, RIN decreases.)

The PBS/QWP is removed and replaced by a regular PBS and a QWP.

Now the reflected power is less than 0.15 mW, which is 1.11 mW from the cavity and 0.985 mW when the beam is blocked in front of the periscope.

( it's more than 1 mW before with a PBS/QWP), and I think it can be less. 

How we test it:

There are QWP and HWP(half wave plate) in front of the PBS/QWP in our RCAV path.

They are adjusted(rotated and tilted) and the PBS is rotated so that the beam split from the PBS is minimized.

This is done to make sure that we have a perfect linearly polarized wave going to the cavity.

 The reflected beam power is measured as it reflected off at PMC's outport.

With the instant coupled PBS/QWP set, there is considerable amount of power coming back to the laser,

about half of the power picked up at the power meter coming from the cavity(see yesterday entry here, how we measure power reflected at

each optic).

We tried to correct the polarization by adding another QWP behind the PBS/QWP, but this does not work.

After we change to a regular single PBS and QWP, we can reduce the power by at least a factor of 10.

Note: to replace the PBS/QPS, I have to move the PBS back a bit so there is enough space for a QWP.

When I re adjust the split power, the PBS is rotated so much and it's very disturbing. This did not happen

when I tried it at the first time.

I turned off the laser for people who will work on sprinkler in the lab tomorrow. The warning light is off.

the calibration value is 71.3 kHz/Volt

for the following setup

center freq = 159.294 MHz

FM DVN = 100 kHz

This calibration will be used to convert the V/rt Hz unit from spectrum analyzer to Hz / rt Hz unit for beat measurement.