Experiment
drorzel | August 4, 2008I've been slacking a bit, lately, in terms of putting science-related content on the blog. Up until last week, most of my physics-explaining energy was going into working on the book, and on top of that, I've been a little preoccupied with planning for the arrival of FutureBaby.
I'd like to push things back in the direction of actual science blogging, so I'm going to implement an idea I had a while back: I'm going to go back through the papers in my CV, and write them up for ResearchBlogging.org.
This offers a couple of nice benefits from my perspective. First of all, I already know what's in…
drorzel | July 30, 2008Over at Backreaction, Bee has a nice post about uncertainty, in the technical sense, not the quantum sense. The context is news stories about science, which typically do a terrible job of handling the uncertainties and caveats that are an essential part of science.
Properly dealing with uncertainty is one of the hardest parts of science. Which is why I'm particularly impressed by people who spend their whole careers measuring nothing but uncertainties-- looking for an electric dipole moment for the electron, or parity non-conservation, or Lorentz violation, or any of a bunch of other things…
drorzel | July 29, 2008In the Reader Request Thread, Ian asks:
I'd like to hear what you think we'll learn (if anything!) when the LHC comes online next month.
Well, that sort of depends on the time scale. I'm not a big accelerator guy, but my sense from reading the blogs of people who are is that we're not likely to learn anything at all this year, other than the answer to the question "do the components of the LHC work?" They've got a few weeks of preliminaries before they start any particles going through, and then a whole bunch of sanity checks and calibration tests to do, and a scheduled shut-down in December…
drorzel | July 10, 2008I'm currently revising the book chapter based on the original "Bunnies Made of Cheese" post, which deals with virtual particles and Quantum Electro-Dynamics. The best proof of the power of QED is the measurement of the anomalous magnetic moment of the electron, where experiment and theory agree to something like thirteen decimal places.
In double-checking things this morning, I find that the Gabrielse group has released yet another improved measurement of the electron g-factor since the last draft of this chapter. I've updated the current draft accordingly, and continue to be amazed by the…
drorzel | May 15, 2008Over at Swans on Tea, Tom has a great story of his Frankenstein Moment, that moment in science when the lightning flashes, and it's immediately clear that everything just worked, and you have successfully reanimated your creation, or split the atom, or discovered high-temperature superconductivity, or whatever.
As he says, these are rare. My own career has been lacking in real, definitive laughing-maniacally-during-the-thunderclap Frankenstein Moments. It's not that I haven't had experimental successes-- I've done some things that I like to think are pretty cool-- but most of them have been…
drorzel | May 9, 2008There's a news piece in Physics World this week titled "Atom laser makes its first measurement" and you might think this would be right up my alley. Mostly, though, it serves to remind me that the term "atom laser" has always kind of pissed me off.
This is somewhat ironic, as it's a beautiful piece of "framing," the sort of thing I've spoken in favor of numerous times here. I have a principled technical objection to the term, though, in that I think the analogy it draws is deliberately misleading.
I should stress that there's really nothing wrong with the analogy on the face of it. The basic…
drorzel | May 7, 2008As seen in a recent links dump, gg at Skulls in the Stars posted a fun challenge for science bloggers:
My "challenge", for those sciencebloggers who choose to accept it, is this: read and research an old, classic scientific paper and write a blog post about it. I recommend choosing something pre- World War II, as that was the era of hand-crafted, "in your basement"-style science. There's a lot to learn not only about the ingenuity of researchers in an era when materials were not readily available, but also about the problems and concerns of scientists of that era, often things we take for…
drorzel | April 29, 2008Via Swans on Tea, a new article on the arxiv reports the possible discovery of a new stable element:
What they did was fire one thorium nucleus after another through a mass spectrometer to see how heavy each was. Thorium has an atomic number of 90 and occurs mainly in two isotopes with atomic weights of 230 and 232. All these showed up in the measurements along with a various molecular oxides and hydrides that form for technical reasons.
But something else showed up too. An element with a weight of 292 and an atomic number of around 122. That's an extraordinary claim and quite rightly the…
drorzel | April 8, 2008(This is the second of two background posts for a peer-reviewed research blogging post that has now slipped to tomorrow. I started writing it, but realized that it needed some more background information, which became this post. And now I don't have time to write the originally intended post...)
Making a quantum computer is a tricky business. The process of quantum computing requires the creation of both superposition states of individual quantum bits (in which the "qubit" is in some mixture of "0" and "1" at the same time) and also entangled states of different qubits (states where the state…
drorzel | April 7, 2008Having brought in a huge new audience at the end of last week-- partly through the "framing"/"screechy monkeys" things, but mostly because my What Everyone Should Know About Science post hit the front page on Reddit-- I figured I should take this opportunity to... Well, drive them all right the hell away again with a peer-reviewed physics post.
Unfortunately, I seem to have misplaced the papers I was going to write about, on experiments with qubits in diamond. They're probably on my desk at work, doing me no good at all. That's OK, though, because it would probably benefit from a little bit…
drorzel | March 28, 2008Back in the comments of one of the "Uncomfortable Question" threads, Matthew Jarpe asked (as background research for a new novel):
If someone were to hand you the keys to your own particle accelerator and you could do any experiment you wanted, what would it be?
Well, if somebody just gave me the keys to CERN, and left for the weekend, I'd be sorely tempted to steal some vacuum pumps and digital electronics. Because, dude, they've got some awfully nice stuff, and they'd hardly miss it...
I assume that the question is really intended to be what sort of particle physics experiment would I do…
drorzel | March 25, 2008Here's a picture of the gas-handling line leading to the discharge region seen in the plasma post:
How many valves can you count in that picture? If you said "seven," give yourself a pat on the back. Here's the same picture with the valves numbered for your convenience:
("Seven! Seven valves! Ha ha ha ha ha ha ha!!! thunder, lightning)
So why all the hardware?
Well, the gas bottle contains krypton gas at a pressure of several atmospheres. The discharge tube feeds into a vacuum system at 10-7 torr, thanks to some honkin' big pumps. We'd like both of them to stay that way, so some valves are…
drorzel | March 24, 2008A couple more pretty pictures of the apparatus, to pass the time:
This is the plasma discharge source that we use to make metastable atoms. We excite the gas using a RF coil (under the tinfoil) with a couple of watts of power at 145 MHz (local ham radio people must love me...), which creates a discharge in the glass tube. Some small fraction of the atoms are excited to the state that we want in the chaos of the plasma, and we work with those downstream.
When it's working right, there's a pretty steep pressure drop across the discharge region:
The pressure is much lower on the left (there's…
drorzel | March 24, 2008Behold, the end of the world is at hand!
They said I was mad-- mad!-- but now they'll pay...
Well, ok, it's not actually a doomsday weapon. It's a shot of the main experiment chamber in my lab, taken in very low light in an attempt to capture the orange glow of the ion gauge inside the chamber. It only looks like an instrument of apocalypse.
Here's a better lit picture:
And here's one showing a bit of the atomic beam line behind the chamber:
The large copper coils in the foreground are for the magneto-optical trap, while the longer coil stretching off to the right is the Zeeman slower. The…
drorzel | March 18, 2008Stephen asks:
Why do you try to hide your secret desire to be a high-energy particle physicist?
Heh. Seriously, honestly, I have no desire whatsoever to be a high-energy particle physicist. I wish I had a somewhat better understanding of particle physics, becuase that way I would have an easier time reading a lot of news stories and Cosmic Variance comment threads, but particle physics is not for me, for a variety of reasons.
The main reason is really that I like doing table-top physics. I like knowing that all of my apparatus is in one place, and under my direct control. I don't have to…
drorzel | March 17, 2008In one of his March Meeting posts, Doug Natelson writes about laser cooling experiments that explore condensed matter phenomena:
While the ultracold gases provide an exquisitely clean, tunable environment for studying some physics problems, it's increasingly clear to me that they also have some significant restrictions; for example, while optical lattices enable simulations of some model potentials from solid state physics, there doesn't seem to be any nice way to model phonons or the rich variety of real-life crystal structures that can provide so much rich phenomenology.
I would dissent…
drorzel | March 14, 2008The next lab visit experiments I want to talk about are really the epitome of what I called the "NIST Paradigm" in an earlier post. These are experiments on "four-wave mixing" done by Colin McCormick (who I TA'd in freshman physics, back in the day), a post-doc in Paul Lett's lab at NIST. As Paul said when I visited, if they had had a better idea of the field they were dabbling in, they would've thought that what they were trying was impossible; thanks to their relative ignorance, though, they just plowed ahead, and accomplished something pretty impressive.
The basic scheme is laid out in…
drorzel | March 13, 2008As I mentioned a few days ago, I visited Luis Orozco's lab during our trip to DC last week. I already talked about his cavity QED stuff, but that's only one of the projects under development. He's also working on a next-generation apparatus for the laser cooling and trapping of francium, to be done at the TRIUMF accelerator in Vancouver-- francium is an element with no stable isotopes, and at most a few grams of it exist on the earth at any given moment. Luis and his students demonstrated the laser cooling of francium a few years back, using atoms made in an accelerator at Stony Brook out on…
drorzel | March 11, 2008Another of the labs I visited while in DC was Steve Rolston's lab at the University of Maryland. This actually contains the apparatus I worked on as a graduate student, including many of the same quirky pieces of hardware-- Steve was the PI (Principal Investigator) for the metastable xenon lab in the Phillips group at NIST, and when he left NIST to take a faculty position at Maryland, he took the apparatus with him.
The xenon lab is now dedicated to work on ultracold plasma physics, which they were just starting when I graduated. The idea is that you can use laser cooling to accumulate a…
drorzel | March 11, 2008In the previous post on this topic, I discussed the various types of noisy vacuum pumps, both clean and dirty varieties. This time out, we'll deal with the quiet pumps, the ones that don't deafen people working in the lab.
Quiet and Dirty: The quintessential quiet and dirty pump is an oil diffusion pump. These have no moving parts, but operate by heating a low-vapor-pressure oil inside a series of baffles so that it sprays out in a downward jet. The oil jet will collide with air molecules in the way, and force them back into the reservoir region of the pump, where they can be pumped away by…