This afternoon Varun and I took some measurements in HAM7. We measured the beam size after the beam diverter now that ZM3 has been moved. We checked the power throughput on the squeezer chain (after beam diverter vs out of OPO), and we checked the F, G, and H fiber transmissions after the fiber protections were installed. We forgot to check the beam alignment on the irises.
To start out we looked at the power on the CLF-trig diode and tweaked up the alignment of ZM2 to minimize the dips in power (probably clipping). We moved ZM2 (P,Y) from (-450, -500) to (-350, -400). During we took the profile measurements we were seeing the beam pointing swing around and the power was back to being dippy again. Is this alignment needing to be touched up every ~30 mins?
Beam profile on reflection of beam diverter
The beam size is larger than our last measurement from before the ZM2 move, and by eye is close to the "nominal" trace in the last plot of Lee's alog.
d_rail_to_beam_diverter = 38 7/8” @ 0cm
d_rail = [0, 4, 8]
A1_13.5 = [1534, 1498, 1475]
A2_13.5 = [1691, 1639, 1638]
A1_d4s = [1537, 1507, 1486]
A2_d4s = [1767, 1692, 1728]
Turning down the averages to 2. The beam size was moving, suspect something HAM7 swinging
d_rail = [0, 4, 8]
A1_13.5 = [1518, 1497, 1470]
A2_13.5 = [1636, 1618, 1578]
A1_d4s = [1521, 1507, 1479]
A2_d4s = [1665, 1646, 1607]
Power check on sqz path - loss ~5% (using maxes)
We measured the power after A:DC1 and at the periscope, as done
here. Similar loss.
out of opo
108.2 uW
mean is 105.9 108.8(max)
meas at periscope:
103.1 uW (max) 100.6 uW (mean)
103.0 uW (max) 100.3 uW (mean)
Fiber throughput measurements
The fiber transmissions are also in line with what we measured previously (
here,
here) I haven't found the latest CLF fiber throughput meas.
pump
G:POL trans: 765 uW
G:POL refl 2.42 uW
G path fiber on sqzT0 1.7 mW
=45% trans
FCGS
H:BS1 trans 185 uW
H:BS1 refl 197uW
H fiber sqzt0 2.11mW
=18% trans
CLF
after F:COL 4.65 mW
F Fiber input sqzt0 12.2 mW
=38% trans
I compared the beam profiles Varun and I took yesterday with the nominal beam (blue curve) from Lee's alog. I'm still working on getting his mode matching code up and running, so I used a la mode. I took the nominal beam parameters (see the green dashed line in this plot), and compared that to a fit of the second beam profile Varun and I took yesterday. There are a couple of caveats: (1) the linked plot only has the beam parameters in the y-direction (solid lines) so I'm not sure of the overlap for x and (2) I don't know the distance from the beam diverter to ZM5, so I've just eyeballed that value from Lee's plot too (the beam profiler was at roughly the same location as our previous measurements, which looks like z~5.96m.
The overlap calculated by alm is 98.2% for y. While it looks like the overlap for x is really good (99.6%), the nominal beam waist looks like it will be smaller in the x direction than the y direction. This seems pretty good, and much closer to nominal than before the ZM3 move.