Alexandra, Shoshana, Arnaud, Fil, Dean (remote)
Today we completed the balancing of the CRS with a period of 61s (or 16.4mHz, which is our target frequency), aligned and tuned the HOQIs (with >75% fringe visibility) and connecterized the picomotor to the mighty mouse connector. Tomorrow, after verifying the balancing and alignments have not changed, we will mount the HOQIs to the CRS, which will complete this first assembly.
In detail :
- Alexandra fixed the miswiring of the monitor signals on the HOQI board which allows us to connect those outputs directly to the oscilloscope
- Fil wired a 18V power cable to the interlock so it can be used for the laser driver. This allowed the transition of the H2-PSL to laser hazard.
- Shoshana rebalanced the CRS to achieved the target frequency of 61s. picture 1 shows the vertical mass arrangement : x2 8-32x3/8 on the back side, and x2 8-32x3/8 on the front siide +2 washers. picture 2 shows the measured resonant frequency.
- After deciding to use the SPI spare pico channel, the picomotor was connecteriized to the might mouse connector via an extension cable (red (+) wire to pin 1, and white (-) wire to pin 2). Thanks to Jeff for offering the components and tooling. (picture 3)
- x2 HOQIs (x1 Left and x1 Right versions) were setup on the optical table with a fixed target to align the various components. We tested with the laser driver knob at 6.3 and an output monitor voltage of 9.3V, which corresponds to ~20mW of laser power. We achieved the following fringe visibility:
- The alignment was done as follow :
- Rotate the Fiber Coupler to maximize the power out of the first PBS (in the hoqi)
- Align the Fiber Coupler in Yaw to center the beam on the 3 PDs
- Align the HOQI baseplate to the target so the retro beam is centered on the 3 PDs - at this point we should see fringing when tapping on the table.
- Continue aligning to the target to maximize fringe amplitude
- Optimize the Lissajou figure with the 2 waveplates (see video for Lissajou figure)
Note1: We did break a set of flexures during balancing today (SN 18 and 11)
Note2: We could not get good fringe visibility on a 3rd HOQI (max 60%) we tested. We will have to get back to this one.
Note3: The Right HOQI has a PD wire that seem to have been pinched during assembly (see last photo). This doesn't seem to be an issue, we will just have to be careful when routing that it doesn't touch the baseplate.
