True Lab Stories: The Oaf Effect

It’s been a while since I did one of these (see “How to Tell a True Lab Story” for an explanation), but yesterday’s laser tech story reminded me of one.

The lab next to mine in grad school also used an argon ion laser to pump another laser, but they were much more cramped for table space than we were. Instead of putting the argon ion laser (which was about 6′ long) on top of the table, they put it on a bench that slid under the optical table, then used mirrors to direct the beam up onto the table top. Since the ion laser is pretty much a black box, this worked great, and they could drag it out when they needed to do major maintenance.

Eventually they needed a new tube in this laser, and called out the tech from the manufacturer, who pulled the bench out from under the table, and swapped in the brand new $20,000 tube. Then he called his bosses to report that the installation was complete, and started to put his tools away.

Can you guess where this is headed?

In tweaking up the laser, he had placed a power meter head in the beam, to allow him to tweak it up. The meter part, he put on the edge of the optical table. When he started cleaning up, he managed to snag the cable between the head and the meter, pulling the meter off the edge of the table…

… where it dropped about a foot, directly onto the brand-new tube, cracking it. So he had to call his bosses back, and say “Ummm…”

Most True Lab Stories involve people doing something that seemed like a good idea for some reason, and wound up leading to disaster for reasons beyond their control. There are some, though, that are the result of garden-variety clumsiness, inevitably ending with the destruction of some incredibly valuable piece of apparatus.

Happily, I didn’t break anything all that valuable, but I do have an Oaf Effect story of my own. As a part of one of the experiments for my thesis (the “one-afternoon experiment” that took three months), we needed to do a bunch of measurements at different laser intensities. The usual way to do this is to place neutral density filters in the beam, reducing the intensity by a known amount with each filter, but we didn’t have a very good selection of filters, for whatever reason.

We looked around, though, and found a company selling really nice filter wheel assemblies, allowing you to cover three or four orders of magnitude in intensity by clicking different filter combinations into place. They’re great gadgets, and perfect for our purposes, so we ordered one and had it shipped overnight (I remember that the German post-doc on the project was amazed we could get it that quickly).

The filter wheel arrived the next day, and we used it for some preliminary measurements, which took most of the afternoon. After everybody else had gone home, I started on the main measurement we had wanted to do, and put the filter wheel in position. Then, I thought better of the position– it would really work better on the other side of the optical table– picked it up and started to walk around the table…

… whereupon I snagged my foot on a BNC cable, tripped, and dropped the filter wheel directly onto the floor, cracking essentially every filter in it except for the clear glass plates. We were still able to use it, but the data in the paper have more scatter than they ought to, because the cracks introduced extra uncertainty in the intensity of the laser.

So, what’s your favorite “clumsy oaf” lab story?