Tag Archives: vacuum system

Open hardware for atomic physics from 1995

While I was researching how different labs built their atomic physics experiments, I came across a pair of articles by Carl Wieman and his team, which they wrote with the explicit purpose of helping others build their own lab. These articles can be really considered scientific open hardware, and I was very excited to dig into them.

The two papers are from 1992-1995. The first is “A narrow-band tunable diode laser system with grating feedback and a saturated absorption spectrometer for Cs and Rb” by MacAdam et al. (DOI: 10.1119/1.16955), followed by “Inexpensive laser cooling and trapping experiment for undergraduate laboratories” by Wieman et al. (DOI:10.1119/1.18072). While the first one lays the foundations with a very detailed description of a laser design (and a very verbose title), the second one that strikes me as doing something really awesome.

Before going any further, if you don’t have access to the above links, the Wieman paper can also be downloaded from the University of Oregon. Had a chance to take a look?

The “Inexpensive laser cooling …” paper does something rare: talks to (aspiring) researchers outside of the core academia. Its aim is to prepare an undergraduate lab to run such experiments, laser cooling and magneto-optical trapping, that was definitely cutting edge at the time of writing:

“Our principal goal was to develop an apparatus which could be built and operated reliably with minimal expense and technical support. In most respects, however, this trap’s performance is equal or superior to what is achieved with the “traditional” designs used in many research programs, […]”

The paper briefly introduces the reader to the basics of laser cooling and trapping, then goes on to their experience of designing and building the experimental apparatus.

Graphics from the original paper showing the optical layout
Optical system layout for the experiment

What strikes me brilliant, that besides the successes, the writers also list their errors, arrangements that didn’t work, alternative designs and choices that fall short in some respect (reliability, cost), and common gotchas they encountered in their progress. Way too few research papers I’ve seen lists these very important “negative information”. In some ways this aspect makes it a very modern, internet age open source project – not just that the design is open, but the way I read it, the intended audience is a community (as opposed to collection of single persons like researchers).

As they sum up the resources they needed to build a complete experiment, they list all the parts (part numbers, sources) and estimate a total cost of US$3000. I wonder how much that figure have changed in the 20 years since the publication. To follow up with that, I started a spreadsheet to list all the parts and their current prices (it’s a work in progress). I would guess, that the total should be less than the original, meaning that it might be even more affordable to set up a similar laboratory now (I’d definitely love to set up one:).

Having built and operated similar systems, I feel in some sections they might underestimate the resources available (especially related to welding and access to vacuum pumps). On the other hand that’s also an opportunity: I should check, where could people find access to these if they are really determined?

To encourage people to build this apparatus, the paper lists a number of open physics problems that can be studied (as of 1995) and parts with:

“We conclude with both an invitation and a warning about many experiments one can do with optical traps: this is a new and rapidly changing field; one is likely to observe phenomena which are not explained in the current research literature and there are no textbooks to provide answers. The student and instructor may find themselves in uncharted territory.”

Carl Wieman received the Nobel Prize in 2001 for his work on laser cooling, together with Eric Cornell and Wolfgang Ketterle. He’s working on science education ever since, and I think with papers like this, he is setting a very good example, as well as giving tools for aspiring scientists. Now onto further uncharted territories!