Started annealing run Annealing run (489-490) on 3" wafers - Crime 01/18/2017 https://dcc.ligo.org/T1700027 using new hardware
Annealing run (449-453) on 3" wafers - Crime 11/01/2016 https://dcc.ligo.org/T1600507
Started annealing of S1600577 S1600580 S1600582 S1600585 at 5pm
ramp up to 600C at 100C/h
hold at 600C for 10 h
ramp down at 100C/h
Started annealing of S1600579 S1600581 S1600583 S1600586 at 5:00pm
At 11:35am, started annealing of ten fused silica wafers (50.8mm / 0.1 mm) [S1800611 S1800612 S1800613 S1800614 S1800615 S1800616 S1800617 S1800618 S1800619 S1800620]
Started annealing of S1600579 S1600581 S1600583 S1600586 at 3:25pm
Samples S1600519 S1600522 S1600565 S1600566 S1600567 S1600568 S1600569
Started annealing of S1600579 S1600581 S1600583 S1600586 at 7:00pm 03/30
Started annealing of blank disks: S1600541 S1600542 S1600545 S1600546 S1600551 S1600552 S1600554 S1600555
900C for 9 hours, starting at 10:30am
Annealing of 8 fused silica substrates (50mm/0.5mm) started at 3:30pm, January 25th 2018. Standard program: 9 hours ramp up to 900 C, 9 hours hold, 9 hours ramp down
Annealing run (447-448) on 3" wafers - Crime 10/27/2016 https://dcc.ligo.org/T1600485-v1
Here's a ongoing summary of the substrate aging tests.
Mark Optics with polished edges and CO2 polished, stored in the CR0 vacuum chamber.
Mark Optics with polished edges, stored in standard wafer container in the dessicator cabinet
Mark Optics with polished edges, stored in standard wafer container in vacuum sealed envelope with dessicant
Mark Optics with polished edges and CO2 polished, stored in standard wafer container in the dessicator cabinet
I added to the model CR0 an additional bias path for the ESD driver:
Some funny RGC idiosyncrasy: if you have a filter bank named "SUM", you can't add a summation block: if you do you get a name conflict at compilation time. That's why I used a matrix
Updated the MEDM screen accordingly
A quick test shows that working with a bias does not improve the ability to excite the modes. The DAC saturates at +-32k, which corresponds to +-10V out of the ADC, matched to the input range of the HV amplifier. The largest excitation of high frequency modes is obtained by using white noise, no bias, and maximum amplitude.
Installed the ADC and DAC boards into a proper box. Also, swapped the temporary DAC board (with cale hack) with the final one. Schematics and PCB are in the DCC: D1600196 and D1600301
The box is sitting on top of the cymac computer, on the back, since I don't have any long cable to connect the ADC.
Last night measurements didn't work well: even without exciting the modes, the ADC was saturating because of the low frequency signal, particularly a 58 Hz peak:
When the modes were rang up, thing got clearly even worse:
So I modified the whitening filter, changing C6 from 2.2u to 220nF. The old and new whitening filters are shown below. We have the same amount of whitening at high frequency, but less amplification of the junk at ~50-100 Hz
With this modification, there's no more saturation, even when the modes are excited.
This afternoon I completed the assembly of the electronics boards to interface the ADC and DAC. The ADC is interfaced with a new custom board, which accepts up to eight QPD inputs, the syncronization signal, and it's connected to the ADC:
For the DAC I used one spare board from the Crackle experiment. However, that board had a wrong pinout for the DAC side connector, so I had to implemented again the same hack I did for the crackling noise experiment.
All boards are connected to the ADC and DACs, and to the syncronization signal generated with a SR DS345. No boxes for the moment being, I'll figure out a better organization of the boards in the future if needed. I still haven't tested if the real time system is able to communicate properly with the new interfaces.
Here are some screenshots of the disk assembly and a look at how four of them will sit into the vacuum chamber. The Solidworks models are available here: D1600197
The 12 following substrates have been measured and are ready for the first coating experiment in Montreal:
In normal conditions the RMS of the QPD signals is dominated by the 58 Hz line generated by the roughing pump. Also, when the modes are excited, they exhibit large sidebands at +- 58 Hz that are an annoyance for the analysis.
I improved a bit the level of the 58 Hz in the QPD signals by putting the roughing pump on top of a "Very Useful Box":
Despite the fact that this advanced vibration isolation is already a little bit effective, it might be good to try to build some better suspension and maybe add an acoustic isolation around the pump.