Optics alignment is one of the dreaded tasks in closing up the EBEX cryostat. The procedure relies on using an articulated measuring arm to measure various locating points on the various optical components and then trying to adjust the positions and angles of these components so they meet our specifications. More often than not, this goes relatively smoothly. But sometimes...well, sometimes it doesn't. And when it doesn't it's possible to spend hours running in circles, chasing a seemingly unattainable tail.
Thankfully, today was mostly the former. After having set up the arm yesterday, Kyle and I started the task of actually doing the measurements and adjusting the optics. After a few false starts (due to tooling balls that had shifted in their holes and flex in the arm's mounting, both easily fixed), we managed to get nice, predictable results for the first three lenses we aligned. The last component, the polarizing grid, gave us some problems with some strange behavior when we tried to adjust it, but eventually it, too, succumbed to its inexorable, inevitable, aligned fate. This took up most of the day for myself and Kyle. During some stretches while Kyle was puzzling over confusing data, I was able to finish assembling our 77K optical filter stack, which helps prevent infrared radiation from penetrating into the depths of the cryostat and shortening our liquid helium hold time.
Today also marked the arrival of a new addition to the EBEX high bay personnel -- another Kyle, this one a grad student from collaborator Brown University, arrived in Palestine late last night and met us at the high bay in the morning. Due to the obvious potential for confusion between Kyle and, uh, Kyle, I shall dub the new Kyle as KyleH. KyleH's arrival was fortuitous, as Franky was starting to get bogged down with both doing the heatsinking of the DfMUX boards as well as testing them. So Franky put KyleH to work gluing heatsinks while he focused on testing. Jeff's day was spent finishing up some HWP hardware and then working with Seth from Columbia on getting HWP system commanding through our flight control software working. Which, seemingly, it now does!