Category Archives: Lab

Adventures in fume hoods

I’m still occupied with other activities (like unpacking boxes, and discovering just how many bugs I can inadvertently cram into 100 lines of perl), but in the absence of blogging I invite you to enjoy the latest PhD Comics strip on fume hoods.
This rings especially true since my lab in grad school needed a fume hood only occasionally, and therefore had only one which sat mostly neglected in the fabrication lab. This made it a fantastic storage closet for unknown chemicals until somebody actually needed to use it for science, at which point hazmat teams would need to be called. (Note to Berkeley EH&S: joking!)
In contrast, the most hazardous chemical at my new job is the curry from Teriyaki Boy, a.k.a. “The Yak”. (Angelenos: Picture the Japanese-food equivalent to Tommy’s chili.)

Just call it entropy research

I thought our lab was a mess, but it could be worse… via Chad Orzel, here’s a chemistry professor (at UT San Antonio) whose lab had to be forcibly cleaned by the university:

“Clean your room or get out!” Words from a frustrated parent to a messy teenager? Not quite. The mess-maker in this case was a chemistry professor at the University of Texas, who ignored repeated warnings to clean up his dangerously cluttered lab space. When University officials decided to clean it themselves, the professor caused such a disturbance that campus police had to lead him away in handcuffs. The professor was eventually fired, which prompted a lawsuit claiming that the University retaliated against him and denied him equal protection.

The legal opinion notes that apart from the problems in the lab, the professor’s office was an “extreme fire hazard”, which still puts him a step below the physics professor here at Berkeley who actually set his office on fire. In any case, this makes me feel better about the disordered state of our lab. We cleaned it only a few months ago but it returns rather rapidly to equilibrium.
(I also want to point out that the legal blogger linked above is evidently a fan of Arrested Development, and has chosen the obvious pseudonym to use on his law blog…)

Publication: Solid-State Qubits with Current-Controlled Coupling

As some of you know, we recently had a paper accepted to Science. The paper appears in the latest issue, and is now available online.
I will try to post something in the next few days that explains these results for the non-physicists in the audience. In the meantime, there’s this post from March about these experiments (from before we had the major findings), and here’s the abstract:

Solid-State Qubits with Current-Controlled Coupling
T. Hime, P. A. Reichardt, B. L. T. Plourde, T. L. Robertson, C.-E. Wu, A. V. Ustinov, John Clarke
The ability to switch the coupling between quantum bits (qubits) on and off is essential for implementing many quantum-computing algorithms. We demonstrated such control with two flux qubits coupled together through their mutual inductances and through the dc superconducting quantum interference device (SQUID) that reads out their magnetic flux states. A bias current applied to the SQUID in the zero-voltage state induced a change in the dynamic inductance, reducing the coupling energy controllably to zero and reversing its sign.

Clarke group research in Physics Today

I’m late noticing this, but the August issue of Physics Today has an article (subscription required) about axion detection experiments, which mentions some work being done in the Clarke group:

An amplifier whose noise temperature approaches the quantum limit would dramatically improve the sensitivty and search rate of the axion experiment. To achieve that goal, our collaborator John Clarke and his coworkers at the University of California, Berkeley, developed a new amplifier based on a microstrip-coupled superconducting quantum interference device in 1996. Unlike the noise behavior of heterojunction transistor amplifiers at low temperatures, the intrinsic noise of the SQUID is proportional to the physical temperature, the origin being thermal noise in shunt resistors across the SQUID’s Josephson junctions. Cooling reduces the noise until it flattens out within 50% of the quantum limit. Newer SQUID designs with micro-cooling fins that enhance the coupling of electrons to the lattice are pushing these devices closer still to the quantum limit.

Unfortunately the full article is only available to subscribers, but those of you who are APS members can check it out. The quantum-limited amplifier is pretty cool and some groups are looking at using it for qubit experiments as well. Ironically, the vacuum pumps required to cool this low-noise amplifier are really loud, and so having to work in the same room as this experiment is sort of annoying.

Rough Superconductor

Niobium is a metal that we frequently use here for its superconducting properties (Tc = 9.3 K). At lunch today we were wondering where it comes from: are there niobium mines somewhere? Perhaps, I suggested, it is mined in Africa under highly exploitative conditions, and we’ll find protestors picketing the lab for our use of blood niobium.
Turns out this is disturbingly close to the truth:

Coltan is the colloquial African name for (columbite-tantalite), a metallic ore comprising niobium and tantalum.
Coltan smuggling has also been implicated as a major source of income for the military occupation of Congo. To many, this raises ethical questions akin to those of conflict diamonds. Owing to the difficulty of distinguishing legitimate from illegitimate mining operations, several electronics manufacturers have decided to forgo central African Coltan altogether, relying on other sources.

On the other hand, it looks like coltan is more important as a source of tantalum, and most niobium comes from Brazil and Canada. So probably our research isn’t built on slave labor and exploitation (postdoc salaries aside).

Types of laboratory scientists

Via Syaffolee, an over-the-top but amusing list of personality types one encounters in a science lab. In fact, I believe I’ve met most of these people. I’ve put a lot of effort into not becoming #5 (the obsessive perfectionist with no life), but this probably just makes me closest to #1 (the antisocial weirdo)—although my personal hygiene isn’t that bad and I’ve been more social lately. Of course it’s not an exhaustive list, so maybe I need to add to it:

7. The Blogger
He seems quiet, but he’s actually telling the world about the latest lab mishaps on the Internet. These scientists prefer highly automated experiments so as to spend more time surfing the web. They’re good with computers and publicizing results to a broad audience. They are communicative provided the medium is e-mail or IM, and happy to come to parties if there’s a proper Evite or MySpace announcement. If the network goes down they are likely to display withdrawal symptoms.

Measurements of gravity using cryogens [Updated]

This is what Chad Orzel refers to as a True Lab Story:
Condensed matter labs such as ours receive frequent deliveries of liquid nitrogen in one- or two-hundred liter dewars. Unfortunately, most of the Berkeley cond-mat labs are in Birge Hall, which has no loading dock, so that the LN2 dewars arrive on the first floor of neighboring LeConte where they must be wheeled over to their destination by some low-seniority student. Since the Berkeley campus is on a hill, the loading dock at the back of the building is one floor higher than the other entrances to LeConte and all the entrances to Birge. One can push the dewar around the outside of LeConte, but a shorter route is to take the elevator down one floor and go out the side door.
Yesterday the LeConte elevator was out of order, which for most of us would have meant taking the long way around. However, one undergrad, tasked with transporting a full 230L dewar, simply decided to take the stairs.
At about 80% the density of water, 230 liters of liquid nitrogen weighs about 400 pounds, not counting the additional weight of the steel vessel containing it. When rolled onto the stairs, the dewar promptly tipped over and plummeted downward on its side, knocking deep gouges in the marble steps and dragging along the unfortunate student, who inexplicably held on as his cargo began to tumble. Miraculously both student and dewar arrived at the landing without rupturing, but the dewar was still on its side and pressure was building up.
This was the situation when we got the frantic call from the building manager; once enough of us arrived at the scene we were able to pull the dewar upright and release the pressure. This averted any imminent explosion, but now we had a different problem: 400 pounds of liquid nitrogen stranded on a landing between the ground and first floors. Suggestions were floated including emptying the nitrogen out the nearby window, but ultimately we found another dewar which was wheeled to the top of the stairs on the first floor, and the nitrogen was transferred there through a long hose. The empty dewar was then carried up the stairs, a task requiring four men and gouging new (but shallower) grooves in the staircase.
Recalling what happens when a LN2 cylinder does rupture, it’s the general consensus that this student is lucky to have survived and LeConte Hall is lucky to still have a staircase.
Photos below the fold [updated with photo of wall damage]:

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Friday Lab Blogging: Proper Laboratory Attire

Safety is a major concern in any lab, and in this group we are very dedicated to maintaining a safe environment. We are so dedicated that our last safety warden left to become a Buddhist monk. We’ll see how long the next one lasts.
Some processes, such as silvering glass dewars, are sufficiently hazardous to alarm even the most reckless among us, and so we have assembled an appropriate set of gear, modeled below by Iskander:
safety boy
The stylish yellow lab coat, with detachable hood for the emo hoodie look, is flame- and acid-retardant, perfect for handling the fulminate byproducts of the silvering process. The face shield adds that edgy “riot gear” touch, but since a face shield only qualifies as secondary eye protection it is complemented by an elegant pair of safety goggles. Heavy gloves complete the outfit, removing any possibility that one might handle something delicately and thereby avoid the inevitable explosion.
Chemists in the audience are welcome to mock our misplaced concern and/or one-up us with stories of yet more elaborate lab outfits.