My Lab
drorzel | July 25, 2013The other day, I made a suggestion to one of my research students of an experiment to try. When I checked back a day later, she told me it hadn't worked, and I immediately realized that what I had told her to do was very stupid. As penance, then, I'll explain the underlying physics, which coincidentally has a nice summer-y sort of application alluded to in the post title.
If you're the sort of person who enjoys swimming, and can either open your eyes underwater or regularly wear a mask or goggles, you've probably notice that the underside of the surface of a swimming pool or other body of…
drorzel | October 22, 2010As promised, an answer to a question from a donor to this year's DonorsChoose Blogger Challenge. Sarah asks:
Chad, can I get a post about how you (or scientists in general) come up with ideas for experiments? You've covered some of the gory detail with the lab info posts, but I think it would be useful for your readers to see where the ideas come from.
The answer is obvious: Ideas come from Schenectady. Which, not coincidentally, is where I live...
More seriously, in my area of experimental physics, I think there are two main ways people come up with ideas for new experiments:…
drorzel | October 21, 2010Melissa at Confused at a Higher Level has a nice post on the tension between faculty research and teaching:
Malachowski writes, "We all know that working with undergraduates is time consuming and in some cases it slows down our research output, but work with undergraduates should be supported, celebrated, and compensated at a high level. For most of us, the process involved in research with students is as important as the product." If colleges adopt a narrow definition of scholarly productivity measured only by publications, they may unintentionally provide incentives for faculty not to…
drorzel | September 3, 2010Over at Confused at a Higher Level, Melissa offers an alphabetical list of essential supplies for a condensed matter experimentalist at a small college. This is a fun idea for back-to-school time, so I'll steal it, and offer the following alphabetical list of essentials for Atomic, Molecular, and Optical physics at a small college, kind of a condensed version of the three part series I did a few weeks ago.
A is for Acousto-optic modulator This is a device that uses sound waves in a crystal to deflect light and shift its frequency. It's essential for rapid control of laser properties.
B is for…
drorzel | September 1, 2010I doubt that this will actually work, but then the Web has brought me some improbable successes before, so it's worth a shot:
I have a sealed glass cell (Pyrex, I think, if it matters) that I would like to get re-filled with a mix of rare gases-- partial pressures of 100mT Ne, 30mT Ar, 30 mT Kr. This will contain an RF plasma discharge to serve as a spectroscopic reference for my experiments, and thus needs to be very clean-- I can't have impurities coming out of the walls and quenching the metastable atoms I'm producing in the discharge.
The company that initially made the cell has not…
drorzel | August 13, 2010The third category in our look at lab apparatus, after vacuum hardware and lasers and optics is the huge collection of electronic gear that we use to control the experiments. I'll borrow the sales term "test and measurement" as a catch-all description, though this is really broader than what you'll usually find in that category.
This category covers all sorts of stuff, from power supplies to data acquisition equipment, but we'll start with the oscilloscopes.
The picture above shows two of the many oscilloscopes that rattle around my lab. These are used for almost everything that involves a…
drorzel | August 12, 2010Following on yesterday's discussion of the vacuum hardware needed for cooling atoms, let's talk about the other main component of the apparatus: the optical system. The primary technique used for making cold atoms is laser cooling, and I'm sure it will come as no surprise that this requires lasers, and where there are lasers, there must also be optics.
There are lots of different types of lasers used for laser cooling experiments, but they all need to have certain properties: tunability, stability, and adequate power. Tunability is important because laser cooling requires light at exactly…
drorzel | August 11, 2010Over in the reader request thread, Richard asks for experimental details:
I'd be interested in (probably a series) of posts on how people practically actually do cold atoms experiments because I don't really know.
I needed to take some new publicity photos of the lab anyway, so this is a good excuse to bust out some image-heavy posts-- lab porn, if you will. There are a lot of different components that go into making a cold-atom experiment, so we'll break this down by subsystems, starting with the most photogenic of them, the vacuum system:
(Click on that for a much bigger version.)
This…
drorzel | January 4, 2010I spent most of Saturday in the lab, swapping out a turbopump that was starting to die. How could I tell? Well, for one thing, it made an awful noise, even more than usual for a noisy pump. But after it was stopped and unmounted from the chamber, there was a simple test: comparing the rotation to a second pump that I knew was in better shape:
The pump on the left (with the copper gasket stuck to it) is the old one; the pump on the right is the one that I replaced it with. As you can tell, even with a bearing starting to go, it's a pretty damn good rotor, but clearly worse than the…
drorzel | January 4, 2010Let's say you have some liquid that you want to contain without leaks, say, milk for a baby. What do you do?
Well, you put it in something like a baby bottle, the components of which are shown here:
You have a hard plastic bottle, a soft silicone nipple, and a hard plastic ring that screws onto the bottle. When you put it together and screw the cap down tight, it compresses the silicone between the two plastic bits, squeezing it into the small gaps, and plugging any leaks. Done properly, this will ensure that milk doesn't leak out of the bottle except through the whole in the nipple.
Now,…
drorzel | December 11, 2009I was sitting in my office on campus, working on some computer stuff, when I noticed a bunch of guys from Facilities out in the hall, bustling around doing something. A few minutes later, one of them stopped right outside my door, and called into the main Facilities office on his cell phone.
"We're up here in Science and Engineering to do the annual fire alarm test but, um, there are a bunch of faculty still in the building. Could you, you know, send them an email or something to let them know we're going to ring all the alarms?"
This wouldn't be a big deal if it were a one-off thing-- we are…
drorzel | January 8, 2009My senior thesis student this year came to my office today to ask a question as he's starting to work on writing his thesis. I've given him copies of the theses of the last couple of students to work in my lab, and asked him to start on a draft of the background sections. He was worried that he wouldn't be able to make the background sections sufficiently distinct from the corresponding sections in the earlier theses.
This is a sort of tricky point when it comes to issues of academic honesty in science. Scientific questions always have definite right and wrong answers, and that limits the…
drorzel | November 15, 2008As mentioned briefly the other day, I recorded a Bloggingheads.tv Science Saturday conversation with Jennifer Ouellette on Thursday. The full diavlog has now been posted, and I can embed it here:
This was the first time I've done one of these, and it was an interesting experience.
I'm rocking the handset in this because of the aforementioned cell phone service problems, and because the whole thing was very hastily arranged, and I wasn't able to obtain a headset for the landline. If they ask me back again, I'm definitely getting one.
On the other hand, being tied to the handset did restrain…
drorzel | November 10, 2008SteelyKid has recently begun to figure out her hands. As I noted last week, within the last couple of weeks, she's started to be able to reliably grab things near her. Just within the last few days, she's discovered that she has two hands, and they can interact with each other:
She's started grabbing one hand with the other, and exploring them. I've also seen her start to use both hands in concert, holding a hanging toy steady with one hand, while manipulating bits of it with the other, like a good little scientist.
Hands are, of course, critical to science. You can't be a good scientist…
drorzel | October 7, 2008I got some interesting comments on last week's post about the science blogging bubble, and there were two in particular I wanted to highlight. Bee wrote (among other things):
But what I think are further obstacle to blogging is the inappropriateness of the medium to science. E.g. blogs put by format an emphasis on novelty, which occasionally disturbs me. There's the option to label posts, but who ever looks at this? I'd vastly prefer to be able if interesting topics stay on top, such that it would be easier to spin longer discussions around a specific topic. Not sure I'm making that very…
drorzel | September 2, 2008This was the last of the experiments that I did for my thesis (it's not the last xenon paper I'm an author on, but the work for that one was done while I was writing up), so my memories of it are bound up with the thesis-writing process.
My favorite story about this stuff was when I gave a talk about this work at NIST-- I don't recall if it was before or after my defense-- and somebody asked the obvious question about how the quantum statistical rules are enforced. That is, how is it that you never get two identical fermions colliding in an s-wave state? Since an s-wave collision is just a…
drorzel | September 2, 2008 This is the last of the five papers that were part of my Ph.D. thesis, and at ten journal pages in length, it's the longest thing I wrote. It was also the longest-running experiment of any of the things I did, with the data being taken over a period of about three years, between and around other experiments. As usual for this series of posts, I can sum up the key result in one graph:
(No spiffy color figure this time, as the experiment never made it onto the old web page, and my original figures are three or four computers ago.)
What we found was that when we prepared samples of metastable…
drorzel | August 28, 2008This paper is the third of the articles I wrote when I was a grad student, and the first one where I was the lead author. It's also probably my favorite of the lot, not just because of the role it played in my career, but because it packs a lot of science into four pages.
The whole thing is summarized in this figure from the old NIST web page, which is a simplified version of Figure 2 from the paper itself:
This shows the collision rate as a function of time after we hit a cold sample of atoms with a 40ns pulse of laser light tuned near the atomic resonance frequency. As discussed in the…
drorzel | August 26, 2008It's four am, and your children are safe and asleep. But there's a phone in a white house, and it's ringing. Something is happening in the lab.
What do you want to answer that phone? Is it a physicist with the experience and knowledge to deal with the apparatus?
Even if he's only just gotten back to bed after two hours of dealing with a colicky baby? Well, tough, because you're stuck with him.
Yesterday was Not A Good Day...
The Empress of Eastern New York decided to get fussy Saturday and Sunday nights, which was officially brushed off diagnosed as "colic" (that's medicalese for "your baby…
drorzel | August 21, 2008The experiment described in the previous post was published in early 1998, but the work was done in 1997. This was the year when things really turned around for me in grad school-- the optical control paper was done in the summer 0f '94, and '95 and '96 were just a carnival of pain. Everything in the lab broke, was repaired, and then broke again.
The lead guy on the lattice collision experiment was a post-doc named John Lawall, who really took charge. He completely re-vamped the lock system for the laser, and spent a huge amount of time re-doing the laser alignment for the trap and the…