Using The Lhc To Study High Energy Density Physics?

The Large Hadron Collider (LHC) will be the most powerful particle accelerator around when, according to the plans, it will start operating in the year 2007. Each of its two 7-TeV proton beams will consist of 2808 bunches and each bunch will contain about 100 billion protons, for a total energy of 362 megajoules, enough to melt 500 kg of copper. What if one of these full-power beams were to accidentally strike a solid surface, such as a beam pipe or a magnet?

To study this possibility, scientists have now simulated the material damage the beam would cause. (In the case of an actual emergency, the beam is extracted and led to a special beam dump.) The computer study showed, first of all, that the proton beam could penetrate as much as 30 m of solid copper, the equivalent of two of LHC's giant superconducting magnets. It is also indicated that the beam penetrating through a solid material would not merely bore a hole but would create a potent plasma with a high density (10 percent of solid density) and low temperature (about 10 eV).

Such plasmas are known as strongly coupled plasmas. One way of studying such plasmas would therefore be to deliberately send the LHC beam into a solid target to directly induce states of high-energy-density (HED) in matter, without using shock compression. This is a novel technique and could be potentially a very efficient method to study this venerable subject. (Tahir et al., Physical Review Letters, upcoming article; contact Naeem Tahir of the GSI Laboratory in Darmstadt, n.tahir@gsi.de