Jenne, Kiwamu,

We aligned the SHG and ALS comm paths on ISCT1 this morning. After the alignment, we obtained the following power leves:

• incident on SHG  = 200 mW @  1064nm
• second harmonic power = 1.2 mW @ 532nm
• beatnote of ALS comm = 800 mV p-p @ 80 MHz observed by a scope.

(SHG path alignment)

The beam going through the crystal had been tiled downward -- it was too high on the incident side and too low on the output side of the crystal. We tweaked a 1" steering mirror in front of the bottom periscope mirror to correct it. Also the beam was off in the horizontal direction on the first 2" lens and therfore we shifted the position of this lens to have the beam centered on the lens. We noticed that the HWP after the 2" lens was a bit too low. However, since it was not terrible too low, we left it as it was.

Then we steered a 1" mirror before the crystal to level the beam tilt. It looked like a lens and PBS after the crystal were too high by a bit. Since the first lens strongly deflects the beam, it was difficult to center the beam on both optics. We compromised the beam pointing such that it is not clipped on either of the optics.

We then steered the crystal mount in order to match the crystal to the beam pointing. A screw knob at center bottom was already all the way in and it seemed we needed to go further more, but we could get a green power of 1.2 mW in this configuration and we decided not to touch it any more. We optimized the other three knobs to maximize the green power.

(ALS comm path alignment)

We touched the following optics:

• ALS-PBS1
• ALS-M12
• ALS-BS3
• ALS-BS4
• ALS-BS5
• ALS-M6

in order to optimize the beatnote setup. Since the alignment of the X arm was not stable, we did not really optimize the beat note power. But it the maximum we saw was about 800 mV p-p observed with a scope terminated with a 50 Ohm.

(Green power monitor's feedthrough was bad)

We did not see signals in the green power monitor. We eventually found that this was due to a bad feedthrough (or perhaps the cable was not plugged all the way in). We changed the feedthrough from the top one to the bottom one and it solved the issue. Now the signal is acquired to an ADC. Good.