CERN, Geneva
JINR, Dubna, Moscow Region
The probability of inelastic nuclear interaction in crystals well aligned to the incoming beam is considerably smaller than for its amorphous orientation. Tests performed with 400 GeV/c protons of the CERN SPS and a short bent silicon crystal confirm this behavior: channeled protons interact with crystal nuclei at a rate more that 20 times smaller than protons with randomly oriented trajectories. On the other hand, the quasi parallel beam halo in a collider has a large probability of being channeled in a bent silicon crystals. Tests performed with 120 GeV stored protons in the SPS show that the inelastic nuclear losses decrease by more than five times when the silicon crystal is well oriented respect to the beam envelope. These observations suggest that bent silicon crystals used as a primary collimator in a hadron collider, such as the LHC, will produce a considerably reduced flux of nuclear losses respect to an amorphous material.
CERN, Geneva
HiRadMat is a new facility under construction at CERN that will provide the users with the possibility to investigate the behavior of materials when irradiated with pulsed high energy and high intensity beams extracted from the CERN SPS. The need for such a facility was raised by the LHC collimation project to bridge the gap in knowledge about the resistance of materials under impact with high energy protons. This talk will review the material parameters for which a deeper knowledge would be needed for extensive use in high energy accelerators, and the kind of test that can be conducted in HiRadMat to improve this knowledge. In particular we will discuss destructive testing, meaning test of materials beyond the limit of rupture or at phase change, and damage testing that should reveal changes in materials properties due to long term irradiation below the rupture limit. The facility could be used as well for calibration of radiation detectors like BLMs. The main difficulty connected with the test is how to observe material changes. Some preliminary ideas on on-line and post-irradiation tests will be outlined.
