Vertical Shape determination of a stretched wire from oscillation measurements

The Geodetic Metrology group at CERN uses stretched wires as a reference for the position monitoring and alignment of accelerator components. Until now, stretched wires find in particular use as horizontal offset measure- ment references, since their vertical projection is a line. However, the wire positioning system is able to measure not only the horizontal but also the vertical wire position. In order to use this data as vertical reference of the alignment system, a framework to describe the vertical wire shape is required. This work re-conceptualises a previously proposed optimization based algorithm, that calculates the vertical wire shape via its fundamental frequency from oscillation measurements. As a result, the determination of the vertical shape with respect to a static parabola fitting model was improved one order of magnitude compared to the previously available oscillation-based algorithm. Now, it is possible to determine the wire position with respect to static wire measurements with a precision of the same order of magnitude as the static parabolic fitting model for wires of up to 140 m length. Furthermore, the study of wire oscillations revealed methods to localize restrictions of the wire. With these means, an alternative evaluation method to the static parabolic fitting model is provided that adds information to already existing alignment systems and offers new sensor configuration possibilities for future alignment systems

Challenges for the FCC-ee machin detector interface alignment

The Future Circular Collider (FCC), a 93 km long circular collider, is one of the projects under study at CERN for the post Large Hadron Collider (LHC) era. Its goal will be to search for new particles while confirming and refining measurements on known ones, such as the Higgs Boson. In order to reach the designed luminosity and the requested accuracy of the collider, the Machine Detector Interface (MDI), and more precisely the components inside, such as the final focusing quadrupoles, the Luminosity Calorimeter (LumiCal), screening and compensation solenoids, will need to be extremely precisely aligned and monitored. The alignment of the accelerator components of the MDI is always difficult due to the detector components around the interaction point. This non continuity in the accelerator also creates an inevitable hole in the alignment system. One needs to design a system around the detector in order to align both sides of the accelerator as no space is available through the detector and therefore no line of sight through the detector is allowed. Though, the MDI currently designed is an innovative and elegant solution, having the final focus components of the accelerator, such as quadrupoles or Beam Position Monitor (BPM) and the LumiCal supported by a skeleton to hang in cantilever configuration inside the detector. This design raises additional challenges as it will limit the type of sensors usable in these confined conditions due to the lack of space, radiations, cryogenic cold and magnetic fields. Today, preliminary known alignment requirements for the inner components are extremely tight and current alignment systems cannot reach these values. This paper will underline these complexities and show why they represent challenges for the FCC-ee MDI alignment. Design, sensors, technology, and alignment tolerances will be discussed

Improving high precision cam mover’s stiffness

Pre-alignment is a key challenge of the Compact Linear Collider (CLIC) study. The requirement for CLIC main beam quadrupole (MBQ) alignment is positioning to within 1 μm from target in 5 degrees of freedom (DOF) with ± 3 mm travel. After motion, the position should be kept passively while the system’s fundamental frequency is above 100 Hz. Cam movers are considered for the task. Traditionally they are used for the alignment of heavier magnets with lower accuracy and stiffness requirement. This paper presents a new CLIC prototype cam mover with design emphasis on the fundamental frequency. A finite element method (FEM) model predicts the mode shapes and eigenfrequencies of the system and can be used for further improving the design. Experimental modal analysis (EMA) of the prototype shows that the prototype’s fundamental frequency is at 44 Hz. It also validates the FEM model

Design and study of a 6 Degree-of-Freedom universal adjustment platform for HL-LHC components

In the accelerator domain, the safe and easy alignment of components located in radioactive areas is a main concern. The position of devices, such as magnets and collimators, has to be adjusted in a fast and ergonomic way to decrease the ionizing dose received by the personnel. Each equipment type has its own unique set of requirements such as the weight, or the desired position accuracy. The two opposite approaches are, on one hand, a simple and time-consuming manual adjustment, using regulating screws and shims, and on the other hand, the use of precise and expensive automatic positioning stages and platforms. In the frame of the High Luminosity LHC project, in order to fulfil the safety and technical requirements of alignment for lightweight components, a standardised system is under development. Its target is to provide an easy, low-cost and fast adjustment capability for several type of components that could be embarked on it. This paper describes the design, the study and the test results of such a universal adjustment solution. The engineering approach, the lessons learned (“know how”), the issues to be addressed and the mechanical components behaviour are presented

Remote Qualification of HLS and WPS Systems in the LHC Tunnel

The position of the inner triplets of the LHC is monitored using Hydrostatic Levelling System (HLS) and Wire Positioning System (WPS). A regulation of these systems is needed to guarantee the sensors’ function. Such a regulation was done in-situ up to now, but the level of residual radiation at the level of the inner triplets will significantly increase with the next steps of LHC operation. Two systems have been designed to perform such a remote qualification: a filling/purging system for the HLS system and a wire displacer system for the WPS. In the paper, the requirements and the solutions proposed are described, with the emphasis on the conceptual design and the results obtained

Managing the Survey Activities during LS1

The survey and alignment section has realised a huge campaign of measurements and re-alignment of accelerators and detectors components for the LHC and injectors complex. The permanent monitoring system around the triplets was also strongly upgraded and maintained. This paper describes the motivations for this campaign, the strategy to realise it from the technical and the manpower point of view as well as the first results

A quality assurance approach for the Full Remote Alignment System

The Full Remote Alignment System is a multi-sensor monitoring and alignment system for the position de- termination and adjustment of accelerator components in the High-Luminosity Large Hadron Collider. The objective of this development was the creation of an asset management for equipment of the Full Remote Alignment System that allows a simple, intuitive and time-optimised handling. Experience from previous interventions was analysed regarding the parameter definition and work steps management. Furthermore, tools available at CERN were identified and reviewed for their use in the asset management and information tracking of the sensors. This work evaluates the framework to fully provide an asset management allowing to store the obtained information during validation, calibration, deployment and maintenance processes of the equipment and provide this information to other interfaces during the lifetime of the installation. The overall concepts for asset management and group internal coordination are established. The created, structured analysis allows the implementation of a CERN tools-based asset management for mechanical components together with an infrastructure to efficiently track these assets

HL-LHC Alignment Requirements and Associated Solutions

To increase by more than 10 times the luminosity reach w.r.t the first 10 years of the LHC lifetime, the HL-LHC project will replace nearly 1.2 km of the accelerator during the Long Shutdown 3 scheduled in 2024 [1][2][3]. This paper presents the HL-LHC alignment and internal metrology requirements of all the new components to be installed, from the magnet components to the beam instrumentation and vacuum devices. As for the LHC, a combination of Hydrostatic Levelling Sensors (HLS) and Wire Positioning Sensors (WPS) is proposed for the alignment of the main components, but on a longer distance (210 m instead of 50 m), generating technical challenges for the installation of the stretched wire and for the maintenance of the alignment systems. Innovative measurements methods and instrumentation are under study to perform the position monitoring inside a cryostat of cold masses and crab cavities, in a cold (2K) and radioactive (1 MGy/year) environment, as well as to carry remote measurements in the tunnel of the intermediary components. The proposed solutions concerning the determination of the position and the re-adjustment of the components are detailed in this paper