CERN, Geneva
A single-sided mobile diluter (TCDQ) and a horizontal secondary collimator(TCSG) are installed in the extraction region of the LHC to protect the downstream elements from damage in case of asynchronous beam dump. These collimators have to be precisely setup to shield the arc aperture at 450 GeV, the triplet apertures and the tungsten tertiary collimators (TCT) at the low-beta collision points. During the LHC beam commissioning, several machine protection tests were carried out to validate collimator setup and hierarchy at different beam energies and intensities. The outcomes of these measurements are presented in this paper together with the results of particle tracking simulations for asynchronous beam dump. These studies allowed to quantify the leakage expected from dump protection collimators to the downstream elements, and to validate the system performance towards higher beam intensity.
CERN, Geneva
The LHC transfer lines, injection and beam dump systems are equipped with a series of active and passive protection systems. These are designed to prevent as many failures as possible, for example through surveillance and interlocking, or to absorb any beam which is mis-kicked or mis-steered on passive absorbers. The commissioning, validation tests and performance of the different systems are described, and the implications for the protection of the LHC against different failures during beam transfer are discussed.
CERN, Geneva
The very demanding LHC beam parameters put very strict requirements on the beam quality along the SPS-to-LHC transfer. In particular, the budget for the emittance increase is very tight. During the LHC commissioning, the emittances have been measured in the SPS, the two SPS-to-LHC transfer lines and in the LHC. Preliminary results show the importance of a very well controlled beam steering in the transfer lines together with the need of a robust trajectory correction strategy in order to guarantee long-term reproducibility. Another source of emittance comes from the tilt mis¬match be¬tween the LHC and its trans¬fer lines which generates cou¬pling at in¬jec-tion into the LHC and in turn will contribute to emittance increase. Preliminary results are also discussed.
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.
