The ESA (European Space Agency) is using the UNILAC to test materials for their suitability as radiation shielding for deep space expeditions. I'm thinking this could be a prototype of a reaction motor for an interstellar spacecraft. It they can reach 20% of the speed of light in just over 100 meters, how fast could they get going if they had a thousand meters to work with? Might be pretty quick.
Looks like it is made out of copper. Odd that. Once upon a time I was an apprentice machinist in the radiology department at the OSU (Ohio State University) Hospital. One of my projects there was to make a cyclotron target for irradiating gas. The device was made out of copper and some little bits of brass. I'm guessing we're using copper because it is less susceptible to becoming radioactive, though my little bit of Googling did not turn up any evidence along those lines.
GSI is the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany.
Part 1 here.