Day 14: Neutron Reactor at HZB

Bioref Reflectometer - neutrons pass through "guide" pipe on the right

The neutron research reactor at the Helmholtz Zentrum Berlin was my destination this morning. I arrived at Wannsee, and took the bus to Hahn-Meitner Platz (recognise those names?). I was about a half-hour early, so I decided to take a walk through the surrounding forest. The facility was surrounded by an overgrown forest and double barbed wire fences with security cameras every twenty metres or so.

After I had given my passport details at the security gate, my host, Robert Wimpory, came and welcomed me to the facility. We put on our electronic radiation badges, recorded the starting radiation level in a little book, and headed past another security gate into the reactor area. At the centre of the facility there were stacks of concrete blocks, and behind them, I was told, was the reactor itself - a uranium fission reactor. It emits neutrons radially outwards in all directions, and "guides" lead out to an array of diverse, ingenious experiments (see setup here):

Some experiments were geared towards determining the fundamental properties of matter, some were investigating the structure and behaviour of molecules involved in biochemistry, some were investigating the paints used in artwork masterpieces, while others were testing the structural properties of materials for engineering purposes. In some places diffraction of neutrons through materials was exploited, in others, their magnetic properties were used. One enormous new piece of equipment, the High Field Magnet (HFM), being installed was capable of producing magnetic fields up to 25T (this, Robert informed me, was why the ceiling was so high) to deflect the neutrons. Here is an animation explaining the operation of the HFM.

How cool would it be to be working on one of these experiments, shoulder to shoulder with teams engrossed in their own investigation, COMPLETELY different in nature? According to Robert, all you have to do is come up with an experiment and then apply for "beam time." Then, pending approval by a panel, your experiment can be scheduled.

The physics question for today is: If a neutron carries no overall charge, how is it that it can interact with a magnetic field?

Source for image (labelled for reuse with modification): http://nmi3.eu/news-and-media/photos-and-videos/winners-of-the-1st-illustrating-nmi3-competition-announced.html 

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