Fluka Estimations concerning Obstacles in the LHC Magnets.

The effect of the impact of the full energy LHC proton beam with an object left in the beam pipe is investigated in order to assess the conditions for a superconducting magnet's quench. FLUKA simulations indicate that a quench would happen about 20 m downstream from the impact for a current through the object being several orders of magnitude lower than the nominal beam current. If such a strict current limit (decreasing with increasing obstacle's thickness) is not exceeded in operational conditions, the obstacle might be destroyed without causing any quench, being the vaporization time dependent on its shape and movement. However, any rise of the traversing current above the mentioned limit would result in a beam dump and the obstacle remaining in the machine.