Installation and Quality Assurance of the Interconnections between Cryo-assemblies of the LHC Long Straight Sections

The interconnections between the cryomagnets and cryogenic utilities in the LHC long Straight Sections constitute the last machine installation activity. They are ensuring continuity of the beam and insulation vacuum systems, cryogenic fluid and electrical circuits and thermal insulation. The assembly is carried out in a constraining tunnel environment with restricted space. Therefore, the assembly sequence has to be well defined and specific tests have to be performed during the interconnection work to secure the reliability of the system and thus to ensure the global accelerator availability. The LHC has 8 long straight insertion zones composed of special cryomagnets involving specific interconnection procedures and QA plans. The aim of this paper is to present the installation and quality assurance procedures implemented for the LHC LSS interconnections. Technologies such as manual and automatic welding and resistive soldering will be described as well as the different quality controls, such as visual and radiographic inspection of welds, electrical checks and leak testing. An evaluation and statistical analysis of the results of the interconnection work will be presented

The Interconnections of the LHC Cryomagnets

The main components of the LHC, the next world-class facility in high-energy physics, are the twin-aperture high-field superconducting cryomagnets to be installed in the existing 26.7-km long tunnel. After installation and alignment, the cryomagnets have to be interconnected. The interconnections must ensure the continuity of several functions: vacuum enclosures, beam pipe image currents (RF contacts), cryogenic circuits, electrical power supply, and thermal insulation. In the machine, about 1700 interconnections between cryomagnets are necessary. The interconnections constitute a unique system that is nearly entirely assembled in the tunnel. For each of them, various operations must be done: TIG welding of cryogenic channels (~ 50 000 welds), induction soldering of main superconducting cables (~ 10 000 joints), ultrasonic welding of auxiliary superconducting cables (~ 20 000 welds), mechanical assembly of various elements, and installation of the multi-layer insulation (~ 200 000 m2). Defective junctions could be very difficult and expensive to detect and repair. Reproducible and reliable processes must be implemented together with a strict quality control. The interconnection activities are optimized taking into account several constraints: limited space availability, tight installation schedule, high level of quality, high reliability and economical aspects. In this paper, the functions to be fulfilled by the interconnections and the various technologies selected are presented. Quality control at different levels (component/ interconnect, subsystem, system) is also described. The interconnection assembly sequences are summarized. Finally, the validation of the interconnection procedures is presented, based in particular on the LHC prototype cell assembly (STRING2)

Qualification and Start of Production of the Ultrasonic Welding Machines for the LHC Interconnections

The Large Hadron Collider (LHC) is presently under installation at CERN, Geneva. The approximately 4000 superconducting corrector magnets required by the machine are powered through copper-stabilized Nb-Ti busbars. To interconnect the magnets along the machine, about 50 000 joints between superconducting cables rated at 600 A have to be performed in-situ during the interconnection activities. An ultrasonic welding technique has been developed and optimised by CERN which led to the development of a dedicated machine which was qualified during the assembly of the STRING II, a 110-m chain of cryomagnets assembled as a prototype of the LHC. The realization of the â series â interconnections together with the procurement of the tooling based on functional specifications have been contracted to a consortium of firms. Qualification tests and acceptance criteria in terms of electrical contact resistance, mechanical resistance, reliability and reproducibility have been defined by CERN. This paper presents the tests and some results of the qualification process relevant to the industrialized tooling provided by the contractor. Results of pre-series junctions done in the LHC tunnel are presented together with the perspective for the continuation of the work

The Interconnections of the LHC Cryomagnets at CERN: Strategy Applied and First Results of the Industrialization Process

The final interconnections of the LHC superconducting magnets in the underground tunnel are performed by a contractor on a result-oriented basis. A consortium of firms was awarded the contract after competitive tendering based on a technical and commercial specification. The implementation of the specific technologies and tooling developed and qualified by CERN has required an important effort to transfer the know-how and implement the follow-up of the contractor. This paper summarizes the start-up phase and the difficulties encountered. The organization and management tools put in place during the ramping-up phase are presented. In addition to contractual adaptations of the workforce, several configuration changes to the workflows were necessary to reach production rates compatible with the overall schedule and with the different constraints: availability of magnets, co-activities with magnets transport and alignment, handling of non-conformities, etc. Also the QA procedures underwent many changes to reach the high level of quality mandatory to ensure the LHC performance. The specificities of this worksite are underlined and first figures of merit of the learning process are presented

Copper Heat Exchanger for the External Auxiliary Bus-Bars Routing Line in the LHC Insertion Regions

The corrector magnets and the main quadrupoles of the LHC dispersion suppressors are powered by a special superconducting line (called auxiliary bus-bars line N), external to the cold mass and housed in a 50 mm diameter stainless steel tube fixed to the cold mass. As the line is periodically connected to the cold mass, the same gaseous and liquid helium cools both the magnets and the line. The final sub-cooling process (from around 4.5 K down to 1.9 K) consists in the phase transformation from liquid to superfluid helium. Heat is extracted from the line through the magnets via their point of junction. In dispersion suppressor zones, approximately 40 m long, the sub-cooling of the line is slightly delayed with respect to the magnets. This might have an impact on the readiness of the accelerator for operation. In order to accelerate the process, a special heat exchanger has been designed. It is located in the middle of the dispersion suppressor portion of the line. Its main function consists in providing a local point of heat extraction, creating two additional lambda fronts that propagate in opposite directions towards the extremities of the line. Both the numerical model and the sub-cooling analysis are presented in the paper for different configurations of the line. The design, manufacturing and integration aspects of the heat exchanger are described

On the Government’s Protection of Citizens’ Right to Know

本文讨论的是政府对于公民知情权的保护。文章主要分为三个部分：政府保护公民知情权的必要性、政府如何来保护公民的知情权以及我国政府保护公民知情权的现状和完善建议。文章由前言、第一章、第二章、第三章和结语组成。第一章论述政府保护公民知情权的必要性。本章分为两部分：政府为什么要保护公民的知情权和为什么是由政府来承担公民知情权的保护义务。信息失灵是信息社会信息不充分和信息占有不公平的现象。信息失灵的存在是不可避免的，同时信息失灵影响到了信息社会的各个方面，造成了信息社会信息资源利用的无效率和信息社会的不公平和不便利。这在一定程度上催生了公民对于知情权利的渴求，所以政府保护公民知情权也是政府解决信息社会信...The article discusses the government’s protection on citizen’s right to know. It contains three parts: the necessities for the government to protect citizens’ right to know, how to protect the right to know, the present situation and the perfection of our government’s protection mechanisms. It consists of the preface、chapter1、chapter2、chaper3 and the conclusion. Chapter 1 describes the nec...学位：法律硕士院系专业：法学院法律系_法律硕士(JM)学号：20040817

The Quality Control of the LHC Continuous Cryostat Interconnections

The interconnections between the Large Hadron Collider (LHC) magnets have required some 40 000 TIG welded joints and 65 000 electrical splices. At the level of single joints and splices, non-destructive techniques find limited application: quality control is based on the qualification of the process and of operators, on the recording of production parameters and on production samples. Visual inspection and process audits were the main techniques used. At the level of an extended chain of joints and splices - from a 53.5 m half-cell to a complete 2.7 km arc sector - quality control is based on vacuum leak tests, electrical tests and RF microwave reflectometry that progressively validated the work performed. Subsequent pressure tests, cryogenic circuits flushing with high pressure helium and cool-downs revealed a few unseen or new defects. This paper presents an overview of the quality control techniques used, seeking lessons applicable to similar large, complex projects

The Special LHC Interconnections: Technologies, Organization and Quality Control

In addition to the standard interconnections (IC) of the continuous cryostat of the Large Hadron Collider (LHC), there exists a variety of special ones related to specific components and assemblies, such as cryomagnets of the insertion regions, electrical feedboxes and superconducting links. Though they are less numerous, their specificities created many additional IC types, requiring a larger variety of assembly operations and quality control techniques, keeping very high standards of quality. Considerable flexibility and adaptability from all the teams involved (CERN staff, collaborating institutes, contractors) were the key points to ensure the success of this task. This paper first describes the special IC and presents the employed technologies which are generally adapted from the standard work. Then, the organization adopted for this non-repetitive work is described. Examples of non-conformities that were resolved are also discussed. Figures of merit in terms of quality and productivity are given and compared with standard IC wor

The Preparation of the Cryomagnets and the Assembly of the LHC Test String 2

The numerous complex activities required to prepare the cryomagnets for the installation in String 2 are described. These include the configuration of the mechanical interfaces, thee conditioning of the beam tubes, the installation of beam screens and the instrumentation as well as the final checks. The preparation of the cryomagnets for String 2 has been a dress rehearsal for the preparation that the cryomagnets will undergo before their installation in the tunnel. After a description of the interconnection procedures of the components for String 2, the tests carried-out to release the String for operation are described. A brief account of the lessons learnt is also given

The LHC Continuous Cryostat Interconnections: The Organization of a Logistically Complex Worksite Requiring Strict Quality Standards and High Output

The interconnections of the Large Hadron Collider (LHC) continuous cryostat have been completed in fall 2007: 1695 interconnections magnet to magnet and 224 interconnections between the continuous cryostat and the cryogenic distribution line have been executed along the 27 km of the LHC. The very tight schedule, the complexity of the interconnection sequence, the strict quality standards applied have required the creation of an ad hoc organization in order to steer and coordinate the activities on the worksite dispersed along the whole accelerator ring. The concatenation of construction and test phases carried out by CERN staff, CERN collaborating institutes and contractors have led to the necessity of a common approach and of a very effective information flow. In this paper, after having recalled the main technical challenges, we review the organizational choices that have been taken and we briefly analyze the development of the worksite in term of allocated resources and production