My Lab
drorzel | May 23, 2007As sort of a counterpoint to the previous entry, here's a more positive poll question:
What's the most useful antiquated tool you keep around?
That is, what dusty old relic do you keep around because there's no modern alternative that works as well for what it does?
In one of the pictures in the previous post, you can just make out the edge of a chart recorder. That's there for a reason-- it isn't often that I want to use a chart recorder, but when you need one, there's nothing else that will do the job. When it comes to long-term monitoring of electronic signals over periods of hours,…
drorzel | May 23, 2007Welcome to the laboratory graveyard:
This picture shows the back room in one of the labs, and most of the gear in it is broken or useless. There's a computer that's so old it has a 5 1/4" floppy drive, the skeleton of a vacuum evaporator, a crappy student STM system, and an electrometer that's so old it has a nicely carved wooden frame. Actually, that last one probably counts as an antique, and might be worth something on that basis. It's certainly not being used, though.
And yet, we keep this stuff around, because we can't bear to throw it out. Which brings us to the Dorky Poll question:…
drorzel | February 7, 2007So, what's the deal with last night's silly obituary? Basically, the main laser in my experiment died because I'm a jackass.
More specifically, the laser in question is a diode laser, similar to the kind found in CD and DVD players. These are broadly tunable, available in a wide range of powers and wavelengths, and relatively cheap. They're also extremely sensitive to static shock, to the point where I have to be careful to always touch something metal before working on the laser or anything close to it.
To check that we have successfully tuned the laser to the right wavelength, we need to do…
drorzel | February 6, 2007SDL 5401-G1, October 2001- February 6, 2007
SDL 5401-G1 ("Sid" to friends) died today of static shock, after five years of service in a grating-locked diode laser system. He had survived three lab floods, and more than a dozen power outages, but succombed to electric shock following a mishap with a Tesla coil.
He is survived by three siblings from the same batch, one of whom has already taken his place in the grating-locked laser mount. In lieu of flowers, the family asks that you send research grants.
Sic transit gloria laseri.
drorzel | February 2, 2007Late spring/ early summer is Conference Season in academic science, with lots of meetings scheduled during the academic break, so that everybody can attend without cutting into their teaching responsibilities (of course, our trimester calendar means we're still in session for most of these, but whatever...). The peak time for conferences in my subfield is late May and early June-- the main meeting I go to, the Division of Atomic, Molecular, and Optical Physics is actually later than usual this year, presumably because it's in Calgary, and they need an extra week or two to thaw out.
Of course…
drorzel | January 17, 2007I spent the better part of an hour putting nail polish on mirror mounts yesterday.
No, this isn't a tragic misinterpretation of my students' advice to "wear more pink." It's because the optical table looks like this:
All those black things are mirror mounts like the one in the top picture, holding mirrors that are precisely positioned as part of one beam line or another. There are at least four different important paths in the picture above, and they tend to bend around a lot, and cross each other. Here's the same picture with the beam lines roughly sketched in:
There's one laser under the…
drorzel | January 3, 2007A little bit before Christmas, I spent an afternoon swapping mirrors out of one line of the apparatus. I was losing too much of the laser light before it went into the chamber, and replacing the mirrors increased the power entering the apparatus by a factor of two or so.
Here's a picture of the two types of mirrors, side-by-side:
"Well, of course you had to replace them," you say. "The one on the left is a perfectly nice mirror, but the one on the right is utter crap. You dolt."
The thing is, the mirror on the right is the type I was putting in. The one on the left is the type that wasn't…
drorzel | December 1, 2006So, what's the deal with that graph I was talking about the other day? I sort of left it hanging at the end, there, but I ought to actually interpret the figure. It also serves as a nice and fairly simple illustration of how physicists approach experimental data.
Here's a newer version of the plot in question, made using more recent data:
shows the fluorescence signal detected in our metastable atoms source as a function of the gas pressure on the source inlet. There's a clear peak in the data at a pressure of 60-70 milliTorr (ignore that one point flying way up above all the others-- that's…
drorzel | November 27, 2006One of my current thesis students has been plugging away for a while at the project described in the A Week in the Lab series last year, and he's recently been getting some pretty good data. I've spent a little time analyzing the preliminary results (to determine the best method for him to use on the rest of the data), and I thought I'd explain a little of the process here.
Here's the key graph from the first set of results:
What we're working with here is a system where we feed krypton gas into a vacuum system, and illuminate it with light from two sources: a really expensive ($7000) vacuum…
drorzel | November 4, 2006I'm in charge of the senior major seminar, in which we have the senior physics and astronomy majors meet once a week to talk about topics of interest to them. I've also been making them give short "progress reports" on their thesis research projects. Last week, one of my students was tapped for a progress report, and started out by saying:
As I'm sure you know, in the Orzel lab, we're in the business of creating dreams. Sort of like Disneyland.
I wonder if I could get that on business cards?
drorzel | October 27, 2006I've had a tab open for a while containing an Inside Higher Ed article on a new approach to introducing science at Emory University:
David Lynn, who chairs the department of chemistry at Emory University, spoke about Emory's seminar program for entering freshmen. All Emory freshmen must take a seminar the first semester and the one for math and science teaches students how to think like a scientist.
The course consists of five modules. Each module is taught by a grad student who presents his own research, guiding students through the research process, from designing studies to defending…
drorzel | October 27, 2006Steinn reports a new metric for research productivity that some people are using: the "H-number":
The H-score, takes all your papers, ranked by citation count; then you take the largest "k" such that the kth ranked paper has at least k citations.
So, you start off with a H-score of zero.
If your 5th highest cited paper has 5 citations but your 6th highest cited paper has 4 citations then your H=5.
If your 10th highest cited paper has 11 citations, but your 11th highest cited paper has 9 citations, then your H=10.
And so on. High H is better.
Yeah, that's just what we need, another quasi-…
drorzel | October 20, 2006After months and months of nothing, behold! Signal!
Explanation below the fold.
What you're looking at here is a graph showing the signal from our optically excited metastable krypton source prototype. The red dots are fluorescence detected by a photomultiplier tube (PMT) from metastable atoms created in the source, and excited by a probe laser passing through the source region. The black dots show the intensity of another beam from the same laser passing through a plasma discharge in a vapor cell, which creates metastbles that absorb the light when the laser is at the right frequency.
The…
drorzel | October 17, 2006Sean Carroll is offering more unsolicted advice (though it is in response to a comment, which makes it borderline solicited...), this time about choosing an undergraduate school. He breaks the options down into four categories, with two small errors that I'll correct in copying the list over here:
Liberal-Arts College (LAC), such as Williams or Union.
Specialized Technical School (STS), such as MIT or Caltech.
Elite Private University (EPU), such as Harvard or Stanford.
Large State School (LSS), such as UCLA or Michigan.
There. That's much better.
I should note two things up front: the…
drorzel | October 13, 2006The previous post was written at about 9:30 last night, and ends on an optimistic note. Of course, any hint of optimism demands retribution from the Lords of Karma, so I got a phone call at 9:45 telling me the power had gone out on campus. The power was apaprently off for something like an hour and a half, which is distressingly typical.
Happily, the person who called me was my research student, calling from the lab to tell me that he had shut down the valves on the roughing pumps. This is an important step, because the turbopumps don't automatically re-start, but the roughing pumps do, and…
drorzel | October 13, 2006We've continued plugging away at the optical excitation experiment discussed in the Week in the Lab series last year, and have finally managed to get a decent metastable signal out of the thing. The signals are at pressures that are considerably higher than I would like (and quite a bit higher than the turbopump is happy with), but recent results from a colleague at Argonne National Lab suggest that this may well be due to the fact that one of our lasers is operating at much lower power than would be ideal. Still, it's data, and data are always good.
As always with experimental work, getting…
drorzel | September 26, 2006(Apologies to Lou Barlow...)
Earlier, I explained why it is that I bought parchment paper for the lab, as part of the process of making magnetic field coils for an atom trap. What's the actual coil-making process like? Details and pictures below the fold:
Here's the form again:
That's a brass pipe wrapped in parchment paper, with some cooling water lines soldered to the pipe. To turn it into a magnet, we need to put about 500 loops of wire around the pipe. This is more than I'm willing to do entirely by hand, so I took it to the machine shop, and popped it onto the lathe:
We wedged an…
drorzel | September 26, 2006I end up buying a lot of weird things for my lab-- really expensive sand, for example-- but the latest purchase was a little strange even by my usual standards:
The other day, on my way into work, I stopped by the store and bought a roll of parchment paper, for use in the lab. It actually makes perfect sense, though it'll require a little explanation, below the fold
The brass thing in the picture above is a length of 3" diameter pipe, which is intended for use as a holder for a magnetic field coil. The coil, one of a pair used to produce a magnetic trap for neutral atoms, will consist of…
drorzel | July 24, 2006As promised in the previous post, some thoughts on superstition in science. This was originally posted in October 2004, and astute readers may note that my opening comments about sports went horribly awry not long after. I take this as proof of my point: talking about these things only screws them up.
Long-time readers of this site may have noticed a lack of sport-related posts in recent weeks, despite the fact that my teams are doing pretty well at the moment. This is not really a coincidence-- I'm as surprised as anyone to see the Giants winning games (though you will note that they lost to…
drorzel | July 6, 2006The last couple of days at work have been Shop Days, with a fair bit of time spent in the department's machine shop making holes in a metal box. This would, I'm sure, be the occasion of much hilarity among my old junior high shop teachers, as my ineptitude in both metal and wood shop was pretty impressive, back in the seventh and eighth grades. I've gotten considerably more coordinated since those exceptionally gawky days, though, and I can use a drill press or a mill without too much trouble now, though no-one will ever mistake me for a machinist.
In a certain sense, Shop Days are among the…