Thursday, July 11, 2013

Charlie and the X-ray Factory: ZeroMQ at ESRF and CERN

Last week I had the pleasure of visiting not one major European physics research facility, but two. My first stop was at ESRF in Grenoble, then I went to visit CERN in Geneva. Both these organizations are moving to use ZeroMQ for their control systems. In this article I'll explain what that means.

First, the Physics
I'm not a physicist, but my kind hosts — Emmanuel Taurel at ESRF, and then Wojtek Sliwinski at CERN — explained the basics to me. ESRF and CERN both have large circular accelerators, though "large" is relative. ESRF's is the size of a small airport. CERN's is the size of a small town. They also have linear accelerators (LINACs) that act as injectors for the larger circular ones. Actually CERN has a dozen different accelerators, built over time.

The major difference — from the physics point of view, not the software — is that ESRF accelerates beams of electrons, while CERN accelerates beams of protons, because the physics experiments they're conducting on both sites are very different.

ESRF scientists basically want to shoot streams of X-rays at samples to get information about their molecular structure. I assume that it's like shining a very bright light at them.

How do you get streams of X-rays? It turns out that if you take electron beams and bend them (or perhaps it's twist them, I'm not sure), they emit X-rays along the direction they wanted to go in. I've not tried this at home, but it makes sense.

So ESRF shoots electron beams (from very big cathode ray guns, like we used to have in TVs) into a ring and speeds them up, getting them to go faster and faster, and as they spin around, they emit X-rays where they get bent by the massive magnets. There are several kinds of magnets, the size of fridges. The X-rays are guided down with more magnets, filtered and bounced off mirrors, and whatnot, and focused on the samples, where high-speed cameras record the results. The ring carries forty independent beams of electrons, and along the ESRF ring there are forty corresponding experiment rooms.

Read more: DZone
QR: Inline image 1