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?

More like this

Well, there is this one that one of my physics professors liked to tell about J. J. Thompson (his advisor had been one of Thompson's students, and claimed to have been there when this happened):

Thompson's group had just finished constructing the first mass spectrometer, the "Parabolic Mass Separator". This involved a large, expensive vacuum tube next to some pretty hefty electromagnets. Being a prototype, there was nothing to really indicate whether the magnets were energized or not. So, to see if it was on, Thompson picked up a wrench and went to wave it near the magnets to see if he could feel the magnet tug on the wrench. Unfortunately, he wasn't holding on to the wrench tightly enough, and the magnet pulled the wrench out of his and and into the glass tube, smashing it . . .

And then, in the stunned silence, Thompson announced "It's on!"

That German post-doc ought to be amazed. Over here in Germany it takes sometimes a week just to get a company telling us the prize of an item we're interested in. For some reason they also prefer to do it by FAX.

And to add to tceisele's story: with our supraconductivity 33 kG magnet, cooled with liquid helium and liquid nitrogen, with a price tag of several 100,000 Euro, things like that happen on a regular basis. It's always on, but everyone tends to forget once during their ph.d. thesis. Not a good feeling to hold some heavy device in your arms, trying to get it off that magnet while the little voice inside shrieks: "Have I broke it? Is it quenching?"
A rite of passage. You don't forget again.

I remember doing some comparatively high-power microwave measurements some years back, in this case being define as "over a Watt, and sometimes well over ten Watts." The sort of thing where I felt obligated to tell people what was going on when they entered the lab, if they were the types to get the heebie-jeebies standing next to the thing, even though I wasn't really radiating anywhere near that power into freespace.

And the boss walks in to see how things are going, and I have this complicated set-up of signal generator, amplifer, antique amplifier, antique GODDAM HUGE AMPLIFIER, device under test, measuring equipment, and computer control, stitched together like Dr. Frankenstein was trying to be a microwave engineer. Now, understand that the measuring equipment in that genre redlines at about 100 mW if it's robust, and unless specially designed, fries at no more than 200 mW. If it is specially hardened, it's good to maybe a Watt. And frankly, even finding attenuators that survive 10 Watts or more in a broad microwave realm is challenging (if you want precision, anyway.)

So the Boss quite properly asks, "Are you sure you know what you're doing?" And really, what other answer can you give other than, "Oh yeah, I've done this lots of times before, I'm just calibrating it now to make sure the GODDAM HUGE AMPLIFIER doesn't overdrive everything...."

And he left, satisfied. He made it out of the lab, but I don't think he made it all the way back to his office before the cal routine went horribly awry. The detector diodes redlined so hard I swear to this day I heard them physically burn up. Breaking one of those is not the biggest deal in the world-- at $5k, they're pricey, but everyone in this business destroys one once in their career. (And really, I've been in earshot of discussions wherein someone was trying to explain to someone else how he managed to damage "the other multi-million dollar test chamber," so I have some perspective....)

But, man, the timing on that one sucked.

(I still blame the GODDAM HUGE AMPLIFIER. It was... special.)

By John Novak (not verified) on 11 Jan 2008 #permalink

A friend was working in a company where their NMR magnet had problem - from time to time a sample got stucked in the magnet. Rather than taking out the probe and upper barrel cleaning and re-calibrating the magnet - a half day chore, the first attempt at getting a stucked sample out was to push the ejection button and then to take a thin wooden stick and try to poke the sample in the spinner gently from the top, to see if it can get unstucked and would eject.

One night a not so brilliant guy working late got his sample stuck in the magnet, he took an ordinary steel rod and tried to poke the sample in the magnet but the superconducting magnet sucked the rod out of hands and it disappeared in the magnet with an omnious crunching sound...So he thought he should try get the rod out, with a tweezer and gess what - the tweezer got ripped out of his hands and disappeared in the magnet hole - actually a half inch of it was stil sticking out as it was sitting on top of the iron rod. The man thought hard "I have to at least get the tweezer out" so he took heavy pliers...

It was an expensive season for thir NMR group, with the rod and tweezers in the magnet, pliers stucked ontop of it and ruined probe. They had to quench and repair the magnet and buy a new probe. About 60k total.

I don't have any one story, but rather a family of related ones, dating back to high school.

You see, I'm a klutz. Actually, I'm more than a klutz, I'm quite literally brain-damaged. The main effect of this damage is that I've got the worst spatial perception of anyone that I've ever known. I simply don't know where things are around me.

Back when I was in high school, I was a big-time physics geek. I used to hang out in the classroom of the physics teacher, a guy named (seriously) Baron Hicken, whenever I could. Unfortunately, in my inimitable fashion, I was prone to bumping into things, knocking things over, and just generally destroying anything unfortunate enough to get in my way.

At one point, the teacher was having us do an experiment to see if glass was actually elastic. We set up a 3 foot by 3 foot pane of glass, raised up on stacks of bricks at the corners, and with something like 50 kilos of bricks on the center. We were going to measure whether the glass sagged over a space of about 2 months. You can guess what happened.

As a result, the teacher invented "The Carroll Scale of Spasticity," as a tool for describing the various incidents of disaster that I managed to cause.

About 5 years later, I got a summer job teaching high school students. As prep for it, I went back to my high school and sat in on classes with my favorite teachers, to see how they handled kids. I didn't tell them I was coming - I just showed up.

So I head for Mr. Hicken's classroom. Baron Hicken is a big tall skinny guy - he actually sort of resembles a very tall version of Bill Nye - the same sort of tall, gangly, crazy guy. Instead of a normal desk, he had a drafting table, with an extra high stool, to accomodate his large legs. I knocked on the door and walked in, and his students were working on labs, and he was sitting in the stool at his drafting table. He looked up, saw me, and shouted "Look out! It's him! The guy I named the scale after!".

He'd taught every subsequent class after I graduated about the Carroll scale. Only fair, I suppose, considering how many things I managed to break.

By Mark C. Chu-Carroll (not verified) on 11 Jan 2008 #permalink

As an undergrad, I broke a billion-dollar Tokamak (fusion reactor) at the U of Wisconsin. Well, actually I just put it out of commission for a day by hitting a wire and breaking the vacuum, so it had to be pumped back down to some incredibly low pressure.

2 from grad school (I'm a theorist...)

Fellow is told to measure the voltage across an Argon laser tube. He's skittish, hooks up the leads. Turns laser on. Now the voltage is supposed to be a couple of hundred volts. BUT its really an Argon ION laser. To ionize the Argon you need about a 10,000 volt pulse. Two power diodes in the power supply literrally vaporized for the most part. The little plastic lid that you take off the Simpson voltmeter to change batteries was welded shut. He found a new advisor.....

2nd Fellow comes to his advisor, says he needs a new beamsplitter.

whats wrong with the old one

It's used up

How do you use up a beam splitter (this is like a half silvered mirror, just splits light into two paths)

It got black where the laser was, so I'd move it over, but now its all black....


What was going on was using a coated beamsplitter in a fairly intense beam. Beam cooks coating, makes black spot. At that point you still have a beam splitter that can be used for a small beam. But the new guy just kept moving it around till the black spots filled the side of the cube......He didn't need a new advisor.

Rather than seeing if glass is elastic (it most certainly is, in fact every solid is elastic), I'm guessing they were checking to see if glass was a fluid and would creep. It's not and it doesn't. What it is is a weird solid that doesn't have a sharp transition temperature to the fluid state.

I guess I'm lucky to have never seen anything really expensive burned up by an oaf move. At a company I worked at, we were designing a new graphics board that used a new processor chip. They were brand new and we could only get 2 from Texas Instruments.

They were in a pin grid array package. I admired the tool a lab tech used to move them. It was a rubber bulb that gave a slight vacuum to a suction cup. He showed me how it allowed him to pick up the expensive CPU without getting any fingerprints on it.

Of course the result of his demonstration was that he discovered that the vacuum wasn't perfect. As air leaked into the bulb, one of our only two test CPUs slipped off his tool and destroyed itself on the concrete floor three feet below.

By Carl Brannen (not verified) on 11 Jan 2008 #permalink

Grad school. Our 2-D MOT (funnel) was water-cooled, and the copper tubing also carried the several-amp current needed to run the trap, so there was a ceramic feedthrough that insulated the funnel from the rest of the vacuum system. The power supply had fairly hefty, stiff leads, too short to go all the way to the shelves where all the other equipment was, and also didn't reach the floor. So it was centered on a stool next to the vacuum system, and worked just fine until I bumped into the stool, hard enough to require the feedthroughs to support the power supply. They weren't up to the task. The chamber vented and signified so by the sound of all the pneumatic valves shutting -- I had wired up an interlock so that when the pressure got too high, all the valves shut and the diffusion pump turned off, and it actually worked, thus saving the diff pump fluid from turning into shellac.

At one point, later on, the tubing sprang a leak, and turned the vacuum system into a fishbowl. Again, the interlock saved us from much damage, though in replacing the ion gauge, I had a slip of the wrench, and broke the bulb of the replacement filament.

I also completely baked a vapor cell at one point while trying to heat it to make it optically thick. I was mesmerized by the blue fluorescence I saw (Rubidium, probably exciting two levels at 780 nm and 776 nm, and decaying through another channel that gives a 421 nm photon). Forgot to monitor the temperature, and the Rb ended up reacting with the glass, and turned brown.

I grow halide crystals for use as laser hosts. Said halide crystals take about a month and a half to grow, with a historical yield of laser-grade material well under 25%, and they are terribly fragile. I had grown a pretty sizable piece that looked to be pretty high-quality, and I was measuring its scattering and depolarization with a HeNe.

The crystal was resting in a V-block which was affixed via an optical post to a spring-loaded translation stage with a micrometer. I wanted measurements with the crystal in the laser and the crystal out of the laser (for reference) and I had grown tired of turning the (unnecessarily finely threaded micrometer) fifty rotations or so to push the crystal out of the laser beam. I noted that I could simply push the stage against its spring, moving it off the end of the micrometer, to get the crystal out of the way. I could then secure it by wedging a small 1/4"-20 screw lengthwise between the tip of the micrometer and the corresponding plate on the stage.

The danger inherent in this method was that is stored a fair amount of energy in the spring of the translation stage. If one holds the translation stage while removing the screw and allows it to gently relax back to the stop, this isn't a problem. If, however, one loses one's concentration during a pointless and annoying conversation with a coworker and one unthinkingly knocks the screw out of place with a balldriver, one can impart a fair amount of kinetic energy to the remarkably fragile and borderline irreplaceable crystal in the V-block...