Sunday, February 23, 2014

What you missed while I was learning new facts about sheet polarizers last fall. Also: Hey, we're going back to Eureka!

It's that time of year again! The sun comes up on the Arctic, the polar stratospheric ozone does interesting things, and the ACE Validation Campaign Team treks back to Eureka to do an intensive measurement campaign. Thus, it's clearly time to write some blog posts!

If you only know me in blogspace (which is highly unlikely, but certainly possible), then you're one Eureka Trip behind the times at the moment. I was there in October/November for a couple of weeks doing some more calibrations. I learned a lot of things that I didn't know I'd ever wonder about.

I didn't THINK that I had blogged zero times on my fall trip to Eureka, but couldn't find any posts here today. Turns out that I was right... but that I had blogged somewhere else. Please consider the following transcription of the email I sent to my parents last fall as your Official Catch Up, and click on the link in it:

Hi Mum and Dad,
I wrote a blog post for our research group. It's here:
Critter count:
0 wolves
8 bunnies
2 muskoxen (one of which was running, so he gets bonus points)


That CREATE Arctic Science blog has things written by my fellow grad students, some of whom do research at Eureka. My post is just one contribution.  Check out in particular, if you want to see what's going on during the campaign in other ways.

If you're link-shy, here's a screenshot:

Part two of this post:

In case you are a scientist yourself, for school, or work, or because you like to tinker, here's a public service announcement of several facts:

1. Waxed paper CAN be a great depolarizing material. Not all of it is. Try various brands. Archival-Quality waxed paper ("Glassine") works better than any kitchen brand I've tried. You'll be familiar with this stuff if you are a museum archivist, but also if you've ever read one of those books that has a colour plate in it with that waxed-paper-like protective sheet over the picture. That waxed paper is the stuff I'm talking about. Buy a new pack from an art supply store, though. Don't hurt the books to get it!

2. Linear sheet polarizers. Three different brands threw us for a loop last November. Linear polarizers act like a fence, allowing through only light that oscillates in one plane, and blocking anything wiggling along a different plane. That's what I expected my sheet linear polarizers to do. They're way more affordable than crystalline polarizers (i.e. they do not cost 700$/one-inch-circle), and they're easy to transport because you can just roll them up. Turns out, (pun not quite intended, but I just noticed it :) that although these sheet polarizers allow only one plane of polarization to pass through (good!), sheet polarizers can ALSO send that light out the other side of the polarizer in not-the-same-plane-it-came-in-as (not so helpful!). If you have an application in which you put your detector directly behind the polarizer, you'll never know (or care) the difference. If you've got more polarizing optics downstream.... well, it makes a difference. Be warned. Not impossible to compensate for, but mighty confusing at 3am when you were not expecting your polarizer to do that.

More about our 2014 spring trip tomorrow as the team heads to Yellowknife!

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