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 New entries since: Wed Dec 31 16:00:00 1969
ID Date Author Type Category Subject
16588   Fri Jan 14 14:04:51 2022 PacoUpdateElectronicsRFSoC 2x2 board arrived

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.

Attachment 1: PXL_20220114_211249499.jpg
16589   Fri Jan 14 17:33:10 2022 YehonathanUpdateBHDAS4 resurrection

{Yehonathan, Anchal}

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.

Attachment 1: AS4_roll_balance2.png
Attachment 2: AS4_magnet_height2.png
Attachment 3: FreeSwingingSpectra.pdf
16597   Wed Jan 19 14:41:23 2022 KojiUpdateBHDSuspension Status

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]

16598   Wed Jan 19 16:22:48 2022 AnchalUpdateBHDPR2 transmission calculation updated

I have further updated my calculation. Please find the results in the attached pdf.

Following is the description of calculations done:

### Arm cavity reflection:

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

$r_{ETMeff} = \sqrt{1 - T_{ETM} - L_{RT}}$

$r_{arm} = \frac{-r_{ITM} + r_{ETMeff}e^{2i \omega L/c}}{1 - r_{ITM}r_{ETMeff}e^{2i \omega L/c}}$

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.

### PRC Gain

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:

$r_{PRMeff} = \sqrt{1 - T_{PRM} - 2T_{PR2} - 2T_{PR3}}$

$t_{PRM} = \sqrt{T_{PRM}}$

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:

$g = \frac{t_{PRM}}{1 - r_{PRMeff}r_{arm}e^{2i \omega L/c}}$

From this, the power recycling cavity gain is calculated as:
$G_{PRC} = |g|^2$

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

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 ($L_{IMC}=0.1$). This power is then multiplied by PRC Gain and transmitted through the PR2 to calculate the LO power.

$P_{LO, PRFPMI} = P_{in} L_{IMC}G_{PRC}T_{PR2}$

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:
P_{LO, align, PRM} = P_{in} L_{IMC} T_{PRM} T_{PR2}

P_{LO, align, no PRM} = P_{in} L_{IMC} T_{PR2}

If we remove PRM from 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.

Attachment 1: PR2transmissionSelectionAnalysis.pdf
Attachment 2: PR2_Trans_Calc.ipynb.zip
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