Take a Load Off

Flat-ish horizontal space always seems to be at a premium in any lab I’ve worked, and it always fills up. Portable area, which isn’t on the floor (less bending and lifting), is even more so — we have several carts that are supposed to be for temporary equipment, but “temporary” is subjective — sometimes the cart sits there for months on end. Since that invariably leaves nothing free, we have this:



No place for people to sit, but the frequency synthesizer and some tools/components can relax. It gets bad enough that there are times when only one lab stool is free, but it turns out not to be a big deal, since only one section of lab bench (where the best soldering station is located) is remotely likely have any free space on it.

Found in the Lab of the Day

Found a bottle in the back corner of the fire locker recently. This dates back to the early days of the lab, when the shop shared some storage space with us.

This was really good acetone for cleaning vacuum parts, and we didn’t want anyone to mistake it for the cheaper acetone one might use to degrease parts. It’s just a matter of putting it in terms a wider audience might understand.

Clang II: The Wrath of Oersted

When last we left our intrepid physicists, they (meaning we) had, after many trials and tribulations, found a magnetic washer that was messin’ with our clock. We removed it, killed it and had it stuffed and mounted on the wall. A couple of you posted congratulatory notes on the success of the mission. I had delayed posting the story until we had confirmed that the vacuum was intact, because Murphy has a way of penalizing premature celebration. And the vacuum was fine the next day. Nope, no problems with the vacuum.

But I still should have waited. The problem is that there was still an icky nasty foreign magnetic field. At first we thought that maybe we (meaning I) had screwed up the shields by getting a magnet too close. And by too close, I mean I accidentally waved my hand too close to one part and heard a resounding THUNK! as the magnetic attraction (however the funk that works) overwhelmed my grip. We routinely degauss the shields, but there’s always the spectre of “burning” in a strong enough localized field that the degauss-o-tron can’t handle. That made for a bit of stomach acid on my part until we confirmed that the shields were fine. The problem was localized to the location of another bolt.


But it wasn’t just a washer this time. There was another one, even though we had asked the magic eight-ball if the problem was fixed and we got a “Signs point to YES” answer. At this point we were incredibly paranoid and with good reason — the pathology was far more sinister. We had noticed that some of the titanium bolts we used would have titanium chips inside the socket head, from the broaching process used to create the hexagonal shape. But they’re titanium chips, right? It’s only a problem if they keep you from tightening the bolt. Or so we had thought, and while we did clean the bolts up, we weren’t as anal meticulous as we needed to be: the problem (most likely one, at least) is that the tool itself is steel, and tools will occasionally chip. And that chip can get caught in with the broaching chips, lodged inside the cap-screw, and that, my friends, is pure evil.

So we scraped and tested — I did my best Nick Stokes impersonation and gathered the specks on some tape so I could wave it in front of the detector, and pretty soon we found one that buried the needle (metaphorically, at least; it was a digital meter)

That’s the one who slimed me. The ugly little spud above the 5″ line. (Yes, we have English-system rulers in the lab. They are a nanosecond long.)

Everything seems to be fine now. This time I waited until I could check that things were running well, and confirm we’re moving on to tackling the next gremlin in the lab.


Imagine, as I sometime ask, that you are doing an experiment which is very sensitive to external magnetic fields. (Like, oh, I don’t know, an atomic clock). And you find evidence of some stray field gremlin that has taken up residence. Since every previous time this has happened it has been the result of a thermoelectric current, you might be lulled into thinking that it’s the same thing, and fixing it will be a piece of cake. A colleague might even announce something to that effect: “It’s a current. It’s always a current. If there’s one thing you can depend on, it’s that stray fields are always currents.”

Welcome to the phenomenon of the sportscaster’s curse.

The sportscaster’s curse, in case you’re not familiar with it, is a phenomenon seen during sportscasts, in which the announcer will basically guarantee an outcome, which then dooms the effort to failure. The athlete is tagged as “Mister Automatic” in some way, with a mention of how he hasn’t missed a free throw/short putt/chip-shot field goal in X attempts, at which point the attempt clangs off the upright or rim, or lips out of the cup. (I’m sure a fair bit of confirmation bias is present here, since the curse doesn’t strike every time, but I cringe nonetheless if it’s a player on my team being lauded for his reliability)

So this is what happened. After we convinced ourselves that it was a simple problem and a quick fix, as happened earlier, we took all the steps to fix it. These steps include taking off the nested layers of magnetic shielding which make the fountain look like a Russian-doll hot-water heater. (or really just a water heater, because you don’t need to heat the water if it’s already hot)

(Such a device might look something like this)

Nada. No obvious connections. We let it cool down to room temperature to minimize gradients and reassembled, but there was no change in the signal. OK, disassemble again and start checking for some magnetic component. But we’re looking for a milligauss-ish field, which isn’t going to be seen amidst the half a gauss of the earth’s field, so the only real way to do this systematically is to change one thing and reassemble it so we can look at the signal in a shielded environment.


We did that a lot over the past few days.


We finally decided that looking with a magnet might be a good idea — a strong one might stick to the offending component. There shouldn’t be any downside — the nonmagnetic materials aren’t going to become magnetized, and if there is a magnetic part, it will only change the scale of the already-existing problem. The latter is exactly what happened. The magnet didn’t stick to anything, but all of the sudden (after yet another reassembling and degaussing of the shields) the problem was much bigger — we had induced more magnetization, and that made it easier to find the offending component. Kinda like finding a needle in a haystack by being able to make the needle a lot bigger.

It was the salmon mousse a washer on a bolt in the vacuum system. Somehow a shiny stainless steel washer had successfully been hiding among the copper ones, and nobody noticed; it either had acquired a similar-looking tarnish, or because of the shininess it looked coppery when it was in the bin. In any event, transplant surgery was indicated and carried out successfully without a vacuum breach (which is good because losing vacuum would have sucked in all the wrong ways)

Lab Story of the Day

The good news: The measurement box that had gone walkabout has been located.

The bad news: it was located just before I was able to construct a milk carton “Have you seen me?” sign to give to the owner.

The better news: They seem to have been breeding, since we found another of these boxes. They’re quite useful, so different divisions had purchased at least one and kinda lost track of how many we had. We borrow equipment from each other all the time (not so much sharing is caring as cooperation, because we are not of the Barney generation), and it didn’t help that we just called them measurement system boxes. Possibly from the town of Measurement System on Measurement System Island, near Measurement System cove. For all of our cleverness, we physicists are often an unimaginative lot when it comes to naming things.

Well, no more. The boxes are now named Larry, Moe, Curly and Harpo. Literally — they now have nametags on them. Harpo is a different model number, hence the comedy-paradigm-shift, and it does beep at us. This paints us into a corner, though. We now have to worry if we get a new model, if it is Abbot/Costello or Laurel/Hardy, and will that limit us to buying only two?

Lab Tale of the Day

We recently changed the details of our MOT coils (OK, we had to. We messed around and there were … consequences. There was a shotgun involved, as it were) The old MOT coils were wound on a form, which held the wires in place. The new geometry is tighter and required something smaller, so we decided to go with no holder — the wires would be free-standing, but since they had adhesive on them, they would stick together. And we could coat them with epoxy, just to make sure.

But this still required something on which to wind the coils, and in machining terminology, such a device is called a mandrel. Which I immediately named “Barbara.”

Overheard in the Lab of the Day

A laser recently died a violent death (probably natural, though foul play has not been ruled out; we are interviewing a component of interest), and during the autopsy we got a whiff of the tell-tale smell of burnt insulation and saw where the circuitry had failed. One colleague wondered aloud of the viability of selling an air freshener that smelled that way. This is the same one who thought that the scent of acetone would make a good cologne.
From the geek collection

Overheard in the Hallway of the Day

I may be posting more “overheard” stories in the near future; we’re in the phase where we’re assembling all of the parts we’ve been working on, more or less individually, so there’s a lot of team activity, which leads to a lot of chatter. Working alone leads to chatter, too, but that’s more cursing Microsoft or muttering about my own mistakes, usually in that order.

I had rearranged the power cords to segregate the modular ones which plug into equipment (i.e. NEMA M at one end, IEC F at the other) and the ones with exposed wires you could wire into a homemade box (or replace a permanent cord) and mentioned this in the hallway. One colleague termed those “power cords of death,” at which point another went all knifey-spooney, “That’s not a cord of death!”

From his lab:

Power cord of death: a power cord with prongs (i.e. male connectors) on both ends. It was apparently used to daisy-chain power strips together, where one had a bad cord on it. Since they’re just wired up in series, you can do this, but you run the risk of wiring a hot receptacle to another hot receptacle, at which point you might have fried grad student. And they don’t often smell good before frying, so that’s a bad thing™.

Son of power cord of death: this was a power cord, sans grounding plug (snipped off), wired into a cable with a BNC connector at the far end. Used to power a fan acting as a chopper in a vacuum system, and the only available vacuum feed-through was BNC. Proving the old adage that when all you have is a BNC feedthrough, all of your electrical problems look coaxial. (Also proving that most professors won’t spend money on new equipment if the old equipment can be kludged together to do the job)