Mechanical dynamic load of the LHC arc cryo-magnets during the installation

About 1700 LHC main superconducting dipoles and quadrupoles will have to be transported and handled between the assembly, the magnet measurements and the storage that precedes the final installation in the LHC tunnel. To ensure the required mechanic and geometric integrity of the cryo-magnets, transport specifications and allowed acceleration loads were defined after detailed dynamic analysis. A large number of cryo-magnets are now arriving at CERN on a regular basis. The logistics for the handling and transport are monitored with tri-axial acceleration monitoring devices that are installed on each cryo-magnet. Measurements are made to commission new equipment like overhead cranes, tunnel transport and handling devices to guarantee that the defined acceleration limits are respected. The results from the acceleration monitoring that are stored in the same quality assurance system as the cryo-magnets allowed to give a first idea of the level of the mechanical dynamic load on each magnet throughout the logistics chain and were used to detect details such as out-of-specification accelerations that needed improvement

TRANSPORT AND INSTALLATION OF CRYO-MAGNETS IN CERN'S LARGE HADRON COLLIDER TUNNEL

The arcs of the Large Hadron Collider (LHC) will contain around 1700 main superconducting dipoles and quadrupoles. The long and heavy magnets are supported on fragile composite support posts inside a cryostat to reduce the heat in-leak to the magnets' super fluid helium bath. The presence of fragile components and the need to avoid geometry changes make the cryo-magnets very difficult to handle and transport. The transport and installation of the LHC cryo-magnets in the LEP tunnels originally designed for smaller, lighter LEP magnets has required development of completely new handling solutions. The paper explains the constraints imposed by the cryo-magnet characteristics, the existing tunnel infrastructure and schedule considerations. The development and realisation of transport and handling solutions are described, starting from conceptual design, through manufacture and testing to the installation of the first cryo-magnet. Integration studies to verify and reserve space needed for manoeuvre and the preparation of the infrastructure for transport and installation operations are also presented. The paper includes conclusions and some of the lessons learned

Measurement and Analysis of Axial End Forces in a Full-Length Prototype of LHC Main Dipole Magnets

A full-length, twin aperture prototype (MBP2N1) dipole magnet for the LHC project was assembled at CERN with collared coils delivered by industry. The design of this prototype is close to that foreseen for the dipole series manufacture as far the coil geometry and that of the yoke components are concerned. The bolts that transfer the axial magnetic forces from the coil ends to the cold mass end plates were instrumented to verify the axial coil support. These axial forces were initially measured after partial assembly, during a standard and an accelerated cool down Introduction to 1.9 K, and during magnet excitation up to 9.2 T. High force levels were observed, triggering a comparison with analytical models and measurements routinely made on 1-m single aperture dipole models. The prototype magnet was re-assembled with lower initial axial force settings and with additional instrumentation, to monitor these forces during the entire assembly process, and re-tested, to possibly correlate axial forces with training behaviour. This paper reports about the experimental observations and provides models towards their understandin

Study of Mechanical Disturbances in Superconducting Magnets using Piezoelectric Sensors and Quench Antenna

Mechanical disturbances in superconducting magnets were studied by recording and characterising the signals induced in piezo-electric ceramic sensors (piezos) and accelerometers by spontaneous acoustic emission (AE) during magnet excitation. The localisation of AE sources as recorded by the piezos corresponds to the localisation obtained by another, indirect technique, the so-called Quench Antenna. Dominant acoustic wave velocities along the magnet were measured by using selected piezos as active actuators. A mechanical disturbance energy calibration is shown and a way to estimate the minimum energy needed for quenching is proposed. A statistical approach is given in order to estimate the most probable amplitude of AE

The Tuning System for the HIE-ISOLDE High-Beta Quarter Wave Resonator

A new linac using superconducting quarter-wave resonators (QWR) is under construction at CERN in the framework of the HIE-ISOLDE project. The QWRs are made of niobium sputtered on a bulk copper substrate. The working frequency at 4.5 K is 101.28 MHz and they will provide 6 MV/m accelerating gradient on the beam axis with a total maximum power dissipation of 10 W on cavity walls. A tuning system is required in order to both minimize the forward power variation in beam operation and to compensate the unavoidable uncertainties in the frequency shift during the cool-down process. The tuning system has to fulfil a complex combination of RF, structural and thermal requirements. The paper presents the functional specifications and details the tuning system RF and mechanical design and simulations. The results of the tests performed on a prototype system are discussed and the industrialization strategy is presented in view of final production.Comment: 5 pages, The 16th International Conference on RF Superconductivity (SRF2013), Paris, France, Sep 23-27, 201

A Wire-Based Methodology to Analyse the Nanometric Resolution of an RF Cavity BPM

Resonant Cavity Beam Position Monitors (RF-BPMs) are diagnostic instruments capable of achieving beam position resolutions down to the nanometre scale. To date, their nanometric resolution capabilities have been predicted by simulation and verified through beam-based measurements with particle beams. In the frame of the PACMAN project at CERN, an innovative methodology has been developed to directly observe signal variations corresponding to nanometric displacements of the BPM cavity with respect to a conductive stretched wire. The cavity BPM of this R&D study operates at the TM110 dipole mode frequency of 15GHz. The concepts and details of the RF stretched wire BPM testbench to achieve the best resolution results are presented, along with the required control hardware and software

Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets

A series of single and twin aperture 1 metre magnet models has been built and tested in the framework of the R&D program of main superconducting dipole magnets for the Large Hadron Collider project. The se models, designed for a nominal field of 8.3 T at 1.8 K, have been constructed to test the performance of SC coils and to optimise various design options for the full length 15 metre long dipoles. T he models have been extensively equipped with a specially developed mechanical instrumentation, enabling both the control of main assembly parameters - like coil azimuthal and axial pre-load, stress i n the outer shrinking cylinder - and also the monitoring of magnet behaviour during cooling and energising, under the action of electromagnetic forces. The instrumentation used, mainly based on strain gauge transducers, is described and the results of mechanical measurements obtained during power tests of the models are discussed and compared with the design predictions based on Finite Element calc ulations

Performance of Five and Six Block Coil Geometries in Short Superconducting Dipole Models for the LHC

A series of similar one meter long superconducting dipole models for the LHC is being manufactured and tested since 1995 for exploring design variants and assembly parameters.Until the end of 1997 all magnets of this series were based on a coil geometry subdividing the conductors in five distinctive winding blocks. In order to cope with new requirements of magnetic field distribution and coil design flexibility, one additional block has been added in the beginning of 1998. A significant number of models of both types have been built and tested, some of them re-built in a different version, adding up in more than 40 models tested so far. The paper reviews the performance of these two different coil designs in terms of manufacture, training behaviour and temperature margins as well as mechanical behaviour and magnetic field quality

Study on Ecosystem Status and its Evolution in Jiulongjiang River Estuary

随着社会经济的发展和自然环境的变化，我国的河口生态系统面临着日益严重的压力和一系列生态灾害频发的风险，迫切需要对河口生态系统开展评价，从科学的角度分析生态系统过去、现状、成因、发展趋势，以指导生态系统管理工作。因此，研究河口生态系统状态及其演变具有重要的理论和实际应用价值。 目前，我国对河口生态系统状态的研究和评价的开展尚在探索阶段，还未形成制度化的评价机制、指标体系及评价方法，虽然有少量与河口生态系统相关的研究成果，但长时间序列的河口生态系统评价少之又少。本文构建了河口生态系统PSR模型评价指标体系，并以中国特有的五年经济社会发展规划时间为划分评价时间单元，建立了长期的河口生态系统状态演变...According to the development of community economy and the changes of natural environment, the estuarine ecosystem in China are faced with growing pressure and a series of risks of environment disaster. It is necessary to assessment on the estuarine ecosystem, to analyze the past, current status, cause and ecolution trends by scientific angles, in order to guide ecosystem management. Therefore, res...学位：理学硕士院系专业：海洋与环境学院海洋学系_海岸带综合管理学号：2242007115083

Status of the Short Dipole Model Program for the LHC

The model program for the LHC main dipoles is dedicated to the study and validation of design variants and assembly parameters to achieve reproducible performance and optimise components and assembly costs. The topics investigated in the last year include the material of the coil end spacers, the use of polyimide films from different manufacturers, the definition of optimum azimuthal and longitudinal coil pre-stress values, shimming of coil ends, collaring around the "cold bore" and different layouts of the yoke ends. This paper presents the main characteristics of such recent models, the results obtained during cold tests and the plans for the final phase of the model program for the LHC dipoles