Beam feasibility study of a collimator with in-jaw beam position monitors

At present, the beam-based alignment of the LHC collimators is performed by touching the beam halo with both jaws of each collimator. This method requires dedicated fills at low intensities that are done infrequently and makes this procedure time consuming. This limits the operational flexibility, in particular in the case of changes of optics and orbit configuration in the experimental regions. The performance of the LHC collimation system relies on the machine reproducibility and regular loss maps to validate the settings of the collimator jaws. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with jaw-integrated Beam Position Monitors (BPMs) was proposed and successfully tested with a prototype (mock-up) collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper, the results of these experiments are discussed. The non-linear response of the BPMs is compared to the predictions from electromagnetic simulations. Finally, the measured alignment accuracy is compared to the one achieved with the present collimators in the LHC.peer-reviewe

Experimental verification for a collimator with in-jaw beam position monitors

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN-SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.peer-reviewe

Electromagnetic Design and Optimization of Directivity of Stripline Beam Position Monitors for the High Luminosity Large Hadron Collider

This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC

CD40-CD40 Ligand Disruption Does Not Prevent Hyperoxia-Induced Injury

Recent studies suggest that apoptosis plays a role in oxygen-induced injury, although the activation pathways and the executioner proteases that lead to cleavage of lung cell proteins and DNA, are not yet identified. We explored previously the tumor necrosis factor/tumor necrosis factor receptor and the Fas/FasL, belonging to the intrinsic pathway, and could not demonstrate any protective effect by interfering with these cell receptors. Lately, it has been shown that interacting with the CD40 system, also known to promote cell death, by administering anti-CD40 ligand (L) antibody was beneficial in several diseases and, in particular, in hyperoxia-induced injury. Using CD40- and CD40L-deficient mice (−/−) as well as administering anti-CD40L antibody, we examined the extent of lung injury in oxygen-breathing mice by several ways (lung weight, histology, inflammatory mediators, and DNA ladder) as well as the mortality. The development of lung injury was similar in wild-type, CD40−/−, CD40L−/−, or in wild-type mice treated with anti-CD40L antibody. Apoptosis was present in all conditions at 72 hours of oxygen exposure. These results show that oxygen-induced injury does not require CD40-CD40L interaction and that apoptosis of lung cells does not involve this pathway

First beam results for a collimator with in-jaw beam position monitors

With more than 100 collimators the LHC has the most complex collimation system ever installed in an accelerator. The beam-based setup time of the system was a nonnegligible factor during the commissioning of the LHC. In addition if the particle orbit at a collimator goes out of tolerance, this collimator needs to be setup again. To reduce the required setup time for the collimation system and to obtain the tight tolerances required for the LHC operation with small beta* and high beam energy, a new collimator design is being developed that integrates a beam position monitor (BPM) into the jaws of the collimator. A prototype of such a phase-II LHC collimator was installed in the SPS at CERN for the 2010 run. In this paper we present the first experimental results from the beam tests performed