Handling and Transport of Oversized Accelerator Components and Physics Detectors

For cost, planning and organisational reasons, it is often decided to install large pre-built accelerators components and physics detectors. As a result surface exceptional transports are required from the construction to the installation sites. Such heavy transports have been numerous during the LHC installation phase. This paper will describe the different types of transport techniques used to fit the particularities of accelerators and detectors components (weight, height, acceleration, planarity) as well as the measurement techniques for monitoring and the logistical aspects (organisation with the police, obstacles on the roads, etc). As far as oversized equipment is concerned, the lowering into the pit is challenging, as well as the transport in tunnel galleries in a very scare space and without handling means attached to the structure like overhead travelling cranes. From the PS accelerator to the LHC, handling systems have been developed at CERN to fit with these particular working conditions. This paper will expose the operating conditions of the main transport equipments used at CERN in PS, SPS and LHC tunnels

Informed consent in critically ill adults participating to a randomized trial.

The 2014 update of the Swiss law on research increases patients' protection; it adds specific requirements for emergency situations, implying an active search for patients' wishes regarding research participation; the possibility of consent waivers is not clearly stated. We explored its practical impact in a RCT on critically ill adults. We considered prospectively collected consents of a multicenter trial addressing the impact of continuous EEG on survival. We assessed the proportions of consents obtained strictly according to the law, of specific waivers for this study obtained from the IRB (early death; relatives' unavailability despite repeated attempts), and the yield of retrieving statements on willingness to research participation. We compared the proportion of consent refusals with those of recent trials in similar environments, and estimated the potential impact on study results. Of 402 recruited patients, six had double inclusions, one died before intervention, and 27 (6.7%, alive on long-term) were excluded following consent refusal or withdrawal, leaving 368 analyzable patients. Specific waivers allowed inclusion of 134 (36.4%) patients, while informed consents were obtained for all others. A statement of willingness to research participation was found in only 14.1%. In recent trials, consent refusal oscillated between 0%-23%, according to different waiver policies. Consent waivers should be specifically foreseen to prevent losing a potentially relevant proportion of patients reaching endpoints, and ensure results generalizability. The yield of looking for willingness to research participation seems low; this questions its current usefulness and calls for a public awareness campaign

Mechanical robustness of HL-LHC collimator designs

Two new absorbing materials were developed as collimator inserts to fulfil the requirements of HL-LHC higher brightness beams: molybdenum-carbide graphite (MoGr) and copper-diamond (CuCD). These materials were tested under intense beam impacts at CERN HiRadMat facility in 2015, when full jaw prototypes were irradiated. Additional tests in HiRadMat were performed in 2017 on another series of material samples, including also improved grades of MoGr and CuCD, and different coating solutions. This paper summarizes the main results of the two experiments, with a main focus on the behaviour of the novel composite blocks, the metallic housing, as well as the cooling circuit. The experimental campaign confirmed the final choice for the materials and the design solutions for HL-LHC collimators, and constituted a unique chance of benchmarking numerical models. In particular, the tests validated the selection of MoGr for primary and secondary collimators, and CuCD as a valid solution for robust tertiary collimators

The "Multimat" experiment at CERN HiRadMat facility: advanced testing of novel materials and instrumentation for HL-LHC collimators

The increase of the stored beam energy in future particle accelerators, such as the HL-LHC and the FCC, calls for a radical upgrade in the design, materials and instrumentation of Beam Intercepting Devices (BID), such as collimators Following successful tests in 2015 that validated new composite materials and a novel jaw design conceived for the HL-LHC collimators, a new HiRadMat experiment, named “HRMT36-MultiMat”, is scheduled for autumn 2017. Its objective is to determine the behaviour under high intensity proton beams of a broad range of materials relevant for collimators and beam intercepting devices, thin-film coatings and advanced equipment. The test bench features 16 separate target stations, each hosting various specimens, allowing the exploration of complex phenomena such as dynamic strength, internal damping, nonlinearities due to anisotropic inelasticity and inhomogeneity, effects of energy deposition and radiation on coatings. This paper details the main technical solutions and engineering calculations for the design of the test bench and of the specimens, the candidate target materials and the instrumentation system

Mechanical Design Analysis of MQXFB, the 7.2-m-Long Low-β Quadrupole for the High-Luminosity LHC Upgrade

As part of the High-Luminosity Large Hadron Collider (LHC) Project, a set of Nb Snquadrupoles are being developed, aiming to enhance the performance of the inner triplets. The new magnets, identified as MQXFA and MQXFB, will share the same cross section with two different lengths, 4.2 and 7.2 m, respectively. During the magnet development, three short models were tested, along with a number of mechanical models, demonstrating the capability of the magnet cross section to achieve the specified performances. The same performances are now required for the full-length magnets. To ensure this, the authors studied the impact of the magnet length on the capability of the structure to provide an adequate support to the coils. Finite element and simplified analytical models were used to evaluate the impact of the magnet length on the stresses in the magnet ends and coil elongation during powering. The models were calibrated using the results from the short model tests, and used to provide an indication on the required prestress and its foreseen impact on the magnet performance.

Assembly of a Mechanical Model of MQXFB, the 7.2-m-Long Low-β Quadrupole for the High-Luminosity LHC Upgrade

The Nb Sn low-β quadrupole MQXF is being developed as a part of the High-Luminosity large hadron collider (LHC) upgrade project. The magnet will be produced in two different configurations, sharing the same cross section but with different lengths. A 7.2-m mechanical model of MQXFB was recently assembled at european organization for nuclear research (CERN) with one copper coil, two low-grade coils, and one rejected coil. Coil dimensions were measured with a portable coordinate measurement machine. The coil pack shimming was designed in order to optimize the field quality and the contacts between the coils and the collars. The azimuthal preload target was defined using the short models experience. The mechanical behavior during loading was monitored by means of strain gauges. The results demonstrated that the structure can provide the required prestress to the coils.

Mechanical Performance of Short Models for MQXF, the Nb3Sn Low-β Quadrupole for the Hi-Lumi LHC

In the framework of the Hi-Lumi LHC Project, CERN and U.S. LARP are jointly developing MQXF, a 150-mm aperture high-field Nb3Sn quadrupole for the upgrade of the inner triplet of the low-beta interaction regions. The magnet is supported by a shell-based structure, providing the preload by means of bladder-key technology and differential thermal contraction of the various components. Two short models have been produced using the same cross section currently considered for the final magnet. The structures were preliminarily tested replacing the superconducting coils with blocks of aluminum. This procedure allows for model validation and calibration, and also to set performance goals for the real magnet. Strain gauges were used to monitor the behavior of the structure during assembly, cool down and also excitation in the case of the magnets. The various structures differ for the shell partitioning strategies adopted and for the presence of thick or thin laminations. This paper presents the results obtained and discusses the mechanical performance of all the short models produced up to now