EXPERIMENTAL AND SIMULATION STUDIES OF HYDRODYNAMIC TUNNELING OF ULTRA-RELATIVISTIC PROTONS*

The expected damage due to the release of the full LHC beam energy at a single aperture bottleneck has been studied. These studies have shown that the range of the 7 TeV LHC proton beam is significantly extended compared to that of a single proton due to hydrodynamic tunneling effect. For instance, it was evaluated that the protons and their showers will penetrate up to a length of 25 m in solid carbon compared to a static range of around 3 m. To check the validity of these simulations, beamtarget heating experiments using the 440 GeV proton beam generated by the SPS were performed at the HiRadMat test facility at CERN [1]. Solid copper targets were facially irradiated by the beam and measurements confirmed hydrodynamic tunneling of the protons and their showers. Simulations have been done by running the energy deposition code FLUKA and the 2D hydrodynamic code, BIG2, iteratively. Very good agreement has been found between the simulations and the experimental results [2] providing confidence in the validity of the studies for the LHC. This paper presents the simulation studies, the results of a benchmarking experiment, and the detailed target investigations. HYDRODYNAMIC TUNNELING The theoretical investigations of the beam–target heating problem at LHC showed that the energy deposited by few ten proton bunches leads to strong heating that produces very high pressure in the beam heated region. This high pressure generates a radially outgoing shock wave that leads to a continuous density reduction at the target center. As a consequence, the protons of the subsequent bunches, and their hadronic showers, penetrate deeper into the target. Continuation of this process leads to a substantial increase in the range of the projectile particles and their hadronic shower. This phenomenon is called hydrodynamic tunneling of ultrarelativistic protons in solid targets. [2] It has a important implications on the machine protection design of every high stored beam energy accelerator.