[Daniel, Torrey]

The theory from post 11547 was that the centering of the piezo on the back of the mirror in the cavity was improved (accidentally) between swapping them out while Masayuki visited the lab. This potentially improved the quality of lock drastically. Because the small thorlabs piezo has proved the best in the cavity, we need a way to repeatedly align the piezo in the center of the back of the mirror. However, Daniel's compression design to hold the piezo in place was not designed for a piezo so small. To combat this Daniel has machined a part will help align the small thorlabs piezo in the piezo compression set up. See 5ED5222C-108A-401E-993C-77349E63ED9C.jpg. The skiniest cylinder on this piece is the same as the inner diameter as the small thorlabs piezo. 

Additionally, we noticed that the spacer being used in the piezo assembly was one with an inner diameter for a 1/4-20 screw. This is close to the size of the outer diameter of the small piezo. We swapped out this spacer to one with a smaller inner diameter so the piezo has more to rest on. With the previous spacer the piezo didn't have a full, flat surface to rest on. Alignment hasn't been recovered, update on the effects of centering/new spacer to follow.