Aligning the mirrors

The laser beam needs to hit each mirror perpendicularly, so that it is reflected into the same direction that it came from. You want to check this at the position farthest away from the mirrors, to be most sensitive to angular deflection. This is right at the laser head.
The first step in alignment is to rotate the black laser head cover to the small aperture (the large aperture is for normal operation). It is this black cover, that you later need to observe the laser reflection on.
To be able to see the reflected beam at this position, you need to get it past the interferometer head. You can do this by putting an "Alignment Aid" (Agilent P/N 10706-60202) into the beam between interferometer head and mirror. This introduces a phase shift to the beam.
If the mirror is a little misaligned, you will now see the laser reflection appear close to the small hole in the black laser head cover. You then need to correct the tilt of the mirror (turning the screws in the mirror mounts with Allen-keys) until the beam is reflected back into the small hole. Some of the screws are hard to reach, so you will need at least one other person to observe the beam while turning the screws. Also you will need to move ZSTG to its downstream limit to be able to turn the screws of some of the sample mirrors. See Tab. 12.2 for which Allen keys to use for the different flexure mirror mounts:

Table 12.2: Allen keys for flexure mirror mounts

Axis	Allen Key	Flexure Stage
zone plate mount
xZ	1.5mm	New Focus 9873M/9761
yZ	2.0mm	MM-050-M
zZ	1.5mm	New Focus 9873M
sample mount
xS	2.0mm	M-MM-075
yS	2.0mm	M-MM-075
zS	3/64"	MFM-050

If you don't see a reflection of the laser beam, there are two possibilities:

1. The beam is well aligned. You can check this by turning a screw a little. If the reflected spot moves out of the small hole, move it back and you're good.
2. The beam is so misaligned, that you first need to do a coarse prealignment further upstream. For this make a tiny hole in a piece of paper and insert it onto one of the beam-benders, such that the original beam can pass through the hole. You should then be able to see the reflection on the paper. Move the mirrors to bring the reflection onto the hole like you would normally do. Then remove the paper and go back to the laser head position.

After correcting the tilt of all 6 mirrors don't forget to move the laser head aperture back to large.