I opened the notebook but I was not sure where you have the loss per bounce for the arm cavity.
PRC_RT_Loss = 2 * PR3_T + 2 * PR2_T + 2 * Arm_Cavity_Finesse * ETM_T + PRM_T
Do you count the arm reflection loss to be only 2 * 13ppm * 450 = 1.17%?
Yeah, I counted the loss from arm cavities as the transmission from ETMs on each bounce. I assumed Michelson to be perfectly aligned to get no light at the dark port. Should I use some other number for the round-trip loss in the arm cavity?
I labeled all the newly installed flanges and connected the in-air cables (40m/16530) to appropriate ports. These cables are connected to the CDS system on 1Y1/1Y0 racks through the satellite amplifiers. So all new optics now can be damped as soon as they are placed. We need to make more DB9 plugs for setting "Acquire" mode on the HAM-A coil drivers since our Binary input system is not ready yet. Right now, we only have 2 such plugs which means only one optic and be damped at a time.
I updated the arm cavity roundtrip losses due to scattering. Yehonathan told me that arm cavity looses 50ppm every roundtrip other than the transmission losses. With the updated arm cavity loss:
The Xilinx RFSoC 2x2 board arrived right before the winter break, so this is kind of an overdue elog. I unboxed it, it came with two ~15 cm SMA M-M cables, an SD card preloaded with the ARM processor and a few overlay jupyter notebooks, a two-piece AC/DC adapter (kind of like a laptop charger), and a USB 3.0 cable. I got a 1U box, lid, and assembled a prototype box to hold this board, but this need not be a permanent solution (see Attachment #1). I drilled 4 thru holes on the bottom of the box to hold the board in place. A large component exceeds the 1U height, but is thin enough to clear one of the thin slits at the top (I believe this is a fuse of some sort). Then, I found a brand new front panel, and drilled 4x 13/32 thru holes in the front for SMA F-F connectors.
I powered the board, and quickly accessed its tutorial notebooks, including a spectrum analyzer and signal generators just to quickly check it works normally. The board has 2 fast RFADCs and 2 RFDACs exposed, 12 and 14 bit respectively, running at up to 4 GSps.
Came this morning, the gluing of the magnets was 100% successful. Side blocks, counterweights were assembled. We suspend AS4 and adjust the roll balance and the magnet height (attachments 1,2). OpLev was slightly realigned.
The pitch was balanced. We had to compensate for the pitch shift due to the locking of the counterweights. Once we got good pitch balance, the motion spectrum was taken (attachment 3). Major peaks are at 755mHz, 953mHz, 1040mHz.
Previous peaks were 755mHz, 964mHz, and 1.062Hz so not much has changed. We pushed back the OSEMs, adjusted OSEM plate and locked it tightly. We lock the EQ stops and transfer AS4 to the vacuum chamber in foil. We open the foil inside the chamber. No magnets were broken. Everything seems to be intact. We connect the OSEMs to CDS.
Is this the correct status? Please directly update this entry.
LO1 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
LO2 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
AS1 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
AS4 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
PR2 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
PR3 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
SR2 [Glued] [Suspended] [Balanced] [Placed In Vacuum] [OSEM Tuned] [Damped]
Last updated: Thu Jan 20 17:16:33 2022
I have further updated my calculation. Please find the results in the attached pdf.
Following is the description of calculations done:
Reflection fro arm cavity is calculated as simple FP cavity reflection formula while absorbing all round trip cavity scattering losses (between 50 ppm to 200 ppm) into the ETM transmission loss.
So effective reflection of ETM is calculated as
The magnitude and phase of this reflection is plotted in page 1 with respect to different round trip loss and deviation of cavity length from resonance. Note that the arm round trip loss does not affect the sign of the reflection from cavity, at least in the range of values taken here.
The Michelson in PRFPMI is assumed to be perfectly aligned so that one end of PRC cavity is taken as the arm cavity reflection calculated above at resonance. The other end of the cavity is calculated as a single mirror of effective transmission that of PRM, 2 times PR2 and 2 times PR3. Then effective reflectivity of PRM is calculated as:
Note, that field transmission of PRM is calculated with original PRM power transmission value, so that the PR2, PR3 transmission losses do not increase field transmission of PRM in our calculations. Then the field gain is calculated inside the PRC using the following:
From this, the power recycling cavity gain is calculated as:
The variation of PRC Gain is showed on page 2 wrt arm cavity round trip losses and PR2 transmission. Note that gain value of 40 is calculated for any PR2 transmission below 1000 ppm. The black verticle lines show the optics whose transmission was measured. If V6-704 is used, PRC Gain would vary between 15 and 10 depending on the arm cavity losses. With pre-2010 ITM, PRC Gain would vary between 30 and 15.
LO power when PRFPMI is locked is calculated by assuming 1 W of input power to IMC. IMC is assumed to let pass 10% of the power (). This power is then multiplied by PRC Gain and transmitted through the PR2 to calculate the LO power.
Page 3 shows the result of this calculation. Note for V6-704, LO power would be between 35mW and 15 mW, for pre-2010 ITM, it would be between 15 mW and 5 mW depending on the arm cavity losses.
The power available during alignment is simply given by:
If we remove PRM from the input path, we would have sufficient light to work with for both relevant optics.
I have attached the notebook used to do these calculations. Please let me know if you find any mistake in this calculation.
Today I suspended AS1. Anchal helped me with the initial hanging of the optics. Attachments 1,2 show the roll balance and side magnet height. Attachment 3 shows the motion spectra.
The major peaks are at 668mHz, 821mHz, 985mHz.
For some reason, I was not able to balance the pitch with 2 counterweights as I did with the rest of the thin optics (and AS1 before). Inserting the weights all the way was not enough to bring the reflection up to the iris aperture that was used for preliminary balancing. I was able to do so with a single counterweight (attachment 4). I'm afraid something is wrong here but couldn't find anything obvious. It is also worth noting that the yaw resonance 668mHz is different from the 755mHz we got in all the other optics. Maybe one or more of the wires are not clamped correctly on the side blocks?
The OSEMs were pushed into the OSEM plate and the plates were adjusted such that the magnets are at the center of the face OSEMs. The wires were clamped and cut from the winches. The SOS is ready for installation.
Also, I added a link to the OSEM assignments spreadsheet to the suspension wiki.
I uploaded some pictures of the PEEK EQ stops, both on the thick and thin optics, to the Google Photos account.
After some work on the reference database file, we now have a template for temporary watchdog implementation for LO1 located here "/cvs/cds/caltech/target/c1susaux/C1_SUS-AUX_LO1.db".
Basically, what I have done is swap the EPICS asyn analog input readout for the COIL and OSEM to accessible medm channels, then write out watchdog enable/disable to coil filter SW2 switch. Everything else in the file remains the same. I am worried about some of the conversions but the only way to know more is to see the output on the medm screen.
To test, I restarted c1su2 but this did not make the LO1 database available, so I am guessing that we also need to restart the c1sus, which can be done tomorrow.
As the new db is made for c1susaux, 1) it needs to be configured to be read by c1susaux 2) it requires restarting c1susaux 3) it needs to be recorded by FB 4) and restartinbg FB.
(^-Maybe not super exact procedure but conceptually like this)
IMC is not such lossy. IMC output is supposed to be ~1W.
The critical coupling condition is G_PRC = 1/T_PRM = 17.7. If we really have L_arm = 50ppm, we will be very close to the critical coupling. Maybe we are OK if we have such condition as our testing time would be much longer in PRMI than PRFPMI at the first phase. If the arm loss turned out to be higher, we'll be saved by falling to undercoupling.
When the PRC is close to the critical coupling (like 50ppm case), we roughly have Tprc x 2 and Tarm to be almost equal. So each beam will have 1/3 of the input power i.e. ~300mW. That's probably too much even for the two OMCs (i.e. 4 DCPDs). That's OK. We can reduce the input power by 3~5.
LO power when PRFPMI is locked is calculated by assuming 1 W of input power to IMC. IMC is assumed to let pass 10% of the power ().
I was wondering whether I should take AS1 down to redo the wire clamping on the side blocks. I decided to take the OpLev spectrum again to be more certain. Attachments 1,2,3 show 3 spectra taken at different times.
They all show the same peaks 744mHz, 810mHz, 1Hz. So I think something went wrong with yesterday's measurement. I will not take AS1 down for now. We still need to apply some glue to the counterweight.
Turns out, the shifting was likely due to the table level. Because I didn't take care the first time to "zero" the level of the table as I tuned the OSEMs, the installation was b o g u s. So today I took time to,
a) Shift AS4 close to the center of the table.
b) Use the clean level tool to pick a plane of reference. To do this, I iteratively placed two counterweights (from the ETMX flow bench) in two locations in the breadboard such that I nominally balanced the table under this configuration to zome reference plane z0. The counterweight placement is of course temporary, and as soon as we make further changes such as final placement of AS4 SOS, or installation of AS1, their positions will need to change to recover z=z0.
c) Install OSEMs until I was happy with the damping. ** Here, I noticed the new suspension screens had been misconfigured (probably c1sus2 rebooted and we don't have any BURT), so quickly restored the input and output matrices.
SUSPENSION STATUS UPDATED HERE
Temp software watchdog now operational for LO1 and the remaining optics!
Koji helped me understand how to write to switches and we tried for a while to only turnoff the output switch of the filters instead of the writing a zero that resets everything in the filter.
Eventually, I was able to move this effort foward by realising that I can pass the control trigger along multiple records using the forwarding option 'FLNK'. When I added this field to the trigger block, record(dfanout,"C1:SUS-LO1_PUSH_ALL"), and subsequent calculation blocks, record(calcout,"C1:SUS-LO1_COILSWa") to record(calcout,"C1:SUS-LO1_COILSWd"), everything started working right.
The PR2 candidate V6-704/705 mirrors (Qty2) are now @Downs. Camille picked them up for the measurements.
To identify the mirrors, I labeled them (on the box) as M1 and M2. Also the HR side was checked to be the side pointed by an arrow mark on the barrel. e.g. Attachment 1 shows the HR side up
AS4 is set to go through a free swinging test at 10 pm tonight. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.
To access the test, on allegra, type:
Then you can kill the script if required by Ctrl-C, it will restore all changes while exiting.
All done (almost)! I still have not sorted the issue of pitch and yaw gains growing together when modified using ramping time. Image of custom ADC and DAC panel is attached.
Indicated by the red arrow:
Even when the side damping servo is off, the number appears at the input of the output matrix
Indicated by the green arrows:
The face magnets and the side magnets use different ADCs. How about opening a custom ADC panel that accommodates all ADCs at once? Same for the DAC.
Indicated by the blue arrows:
This button opens a custom FM window. When the pitch gain was modified with a ramping time, the pitch and yaw gain grows at the same time even though only the pitch gain was modified.
Indicated by the orange circle:
The numbers are not indicated here, but they are input-related numbers (for watchdogging) rather than output-related numbers. It is confusing to place them here.
Camille@Downs measured the surface of these M1 and M2 using Zygo.
The free swinging test was successful. I ran the input matrix diagonalization code (/opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/sus_diagonalization.py) on the AS4 free-swinging data collected last night. The logfile and results are stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/AS4 directory. Attachment 1 shows the power spectral density of the DOF basis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.
The new matrix was loaded on AS4 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.