LGC: Analysis and pratical example of direct levelling observations referenced on the CERN local Geoid model

Direct levelling is performed extensively in the CERN surveying processes for accelerator elements’ alignment and positioning. LGC software (Logiciel Général de Compen- sation1) computes results and associated statistics for ob- servations used by surveyors. Traditionally, direct levelling campaigns are computed separately from the planimetry, using simple differences of height -called in LGC *DVER observation- between two measured points. LGC provides another observation model, called *DLEV, using offsets to a horizontal plane at the position of the station. The level plani- metric position must therefore be known or be computable by additional observations. This more rigorous model al- lows a better integration in 3D computation involving other instruments, such as laser trackers or total stations. This article reviews the traditional method and analyses the use of geo-referenced levelling stations for accelerator element surveying. The influence of the station planimetric position precision and of the geoid model used are studied and illustrated with a practical case

SurveyPad, a common interface to Geode & data processing tools

The metrology and alignment of components installed in accelerators is a very complicated process requiring many calculations to ensure the best performance of the CERN complex. Throughout the years, surveyors at CERN have been relying on several pieces of different offline processing software that were meant to function without an internet con- nection in the tunnels. Most of the programs were operating as clunky command line tools. They required text input files, formatted in a specialized and unique way, and generated non-standardized text file outputs. At the same time, sur- veyors had to use a survey database, and its web interface named Geode, as the source of theoretical positions and all related measurements and computations. Since a need to simplify this workflow arose, SurveyPad was created. SurveyPad is a C++ plugin-based software meant to in- tegrate and govern multiple pieces of processing software. It requires a plugin to be created for each one of them. The plugins provide communication with their corresponding software and come with a graphical user interface that can be displayed within SurveyPad providing easy manipulation of the project files. The plugins share some more advanced features. These include elaborate text editing and one token look-ahead, left-to-right grammars (LALR(1)) for a tailor- made parsing of the contents of software files. Lastly, al- though the pieces of survey software cannot communicate with one another, the plugins can. They cooperate and share some functionalities via SurveyPad. Current feedback from users indicates that despite ongo- ing developments, SurveyPad has already proved to be a functional and convenient tool used by surveyors on a daily basis

HIE-Isolde: Commissioning and first results of the Mathilde system monitoring the positions of cavities and solenoids inside cryomodules

The new superconducting HIE-ISOLDE Linac replaced most of pre-existing REX ISOLDE facility at CERN. This upgrade involves the design, construction, installation and commissioning of 4 high-β cryomodules. Each high-β cryomodule houses five superconducting cavities and one superconducting solenoid. Beam-physics simulations show that the optimum linac working conditions are obtained when the main axes of the active components, located inside the cryostats, are aligned and permanently monitored on the REX Nominal Beam Line (NBL) within a precision of 0.3 mm for the cavities and 0.15 mm for the solenoids at one sigma level along directions perpendicular to the beam axis. The Monitoring and Alignment Tracking for HIE-ISOLDE (MATHILDE) system has been developed to fulfil the alignment and monitoring needs for components exposed to non-standard environmental conditions such as high vacuum or cryogenic temperatures. MATHILDE is based on opto-electronic sensors (HBCAM) observing, through high quality viewports, spherical retroreflectors made of high index (~2) glass. Precise mechanical parts, metrological tables and the, so called, MATHIS software were designed to be able to reconstruct the position of the active elements within a precision of 0.1 mm. The commissioning of MATHILDE and its first results to monitor the cavity and solenoid positions, especially during the installation and tests of the two first cryomodules on the HIE-ISOLDE Linac, are reviewed in this contribution

Mathis software for controlling BCAM-based monitoring and alignment systems

The MATHIS Software (Monitoring and Alignment Tracking for HIE-Isolde Software) aims at providing 3D positions of physical components of the HIE-Isolde superconducting modules, accurately and permanently measured by well-designed networks of BCAM devices (Brandeis Camera Angle Monitoring). Although it is originally intended for the HIE-Isolde project, its architecture and its use cases have been extended and optimized for more general setups. Most of the configuration data are stored either within XML-formatted files or within databases. The adaptation of MATHIS for different BCAM monitoring systems therefore does not require any further code rewriting. Moreover, the software is fully cross-platform and can either be run on the specific Linux machines driving the accelerator electronic devices, or be used on independent Windows workstations as a stand-alone software. In the first case, the software mainly relies on FESA (Front End Software Architecture) which is an object-oriented real-time framework that ensures equipment software portability across CERN accelerators. Through this standardized module, MATHIS communicates with dedicated servers networks and publishes in real-time the computed positions to any workstation, and more specifically to the concerned control room operators. This paper describes the main features and explains the modular architecture of the software

First experience on python development for survey software, advantages and drawbacks

During long shutdown and maintenance periods at CERN, the surveying teams intensively use in-house data processing software, developed in the last decades and mostly written in C++ language. The accurate measurement of the deviations of hundreds of successive accelerator components with respect to their theoretical positions, in either vertical or radial direction, is part of survey activities. The final smoothing operations consist of mechanically re-positioning some of those com- ponents to ensure smooth transitions between elements and to limit optical corrections of the particle beams orbits. RABOT is the survey software currently used to process the measured deviations and provide such smoothed data. Initially designed in Fortran language in the ’90s, it had been fully rewritten in C++ ten years later. However, the unnecessary complexity of its code, as well as missing doc- umentation made it difficult to maintain. Based on reverse- engineering methods, it was recently decided to rewrite this essential software using Python language. The usage of Python as a software development language is a questionable choice from a performance point of view. Indeed, the compiled nature of the C++ language makes it incomparably faster than equivalent algorithms coded in scripting languages such as Python. Nonetheless, there are multiple benefits of choosing Python for simple software development. Amongst them: a more comprehensive syn- tax and automatized implementation such as memory man- agement and dynamic typing. It can drastically reduce the development time and enhances the legibility for non-expert programmers. As a direct consequence, available resources and development efforts can be oriented towards algorithmic optimization and improvements. Moreover, the development relies on robust and efficient numerical libraries such as NumPy that offer a wide variety of tuneable methods. The first in-house survey software implemented fully in Python was achieved and performances improved compared to its older C++ implementation

HIE Isolde – General Presentation of MATHILDE

In the frame of the HIE-ISOLDE project a superconducting Linac will upgrade the energy and intensity of the REX ISOLDE facility at CERN. It will be made of 2 low β and 4 high β cryomodules. Each high β cryomodule houses five superconducting RF cavities and one superconducting solenoid (respectively 6 and 2 for the low β). Beam physics simulations show that the optimum linac working conditions are obtained with components aligned and monitored on the Nominal Beam Line within 0.3 mm for the cavities and 0.15 mm for the solenoids at one sigma level. The Monitoring and Alignment Tracking for HIE-ISOLDE (MATHILDE) system is based on opto electronic sensors, optical and mechanical elements partly exposed to high vacuum and cryogenic temperatures. This paper summarizes the MATHILDE studies and focuses on the viewport crossing, the MATHIS software, the newly designed HBCAM cameras and the retro-reflective targets based on high index glass properties

Alignment and Monitoring Systems for Accelerators and Experiments Based on BCAM - First Results and Benefits of Systems Developed for ATLAS, LHCb and HIE-ISOLDE

In the last few years alignment and monitoring systems based on BCAM* cameras active sensors, or their HBCAM evolution, have been developed at the request of the Technical Coordination of LHC experiments and HIE-ISOLDE facility Project Leader. ADEPO (ATLAS DEtector POsition) has been designed to speed up the precise closure - 0.3 mm - of large detector parts representing in total ~2500 tons. For LHCb a system has been studied and installed to monitor the positions of the Inner Tracker stations during the LHCb dipole magnet cycles. The MATHILDE (Monitoring and Alignment Tracking for HIE-ISOLDE) system has been developed to fulfil the alignment and monitoring needs for components of the LINAC enclosed in successive Cryo-Modules. These systems have been in each case configured and adapted to the objectives and environmental conditions: low space for integration; presence of magnetic fields; exposure to non-standard environmental conditions such as high vacuum and cryogenic temperatures. After a short description of the different systems and of the environmental constraints, this paper summarizes their first results, performances and their added value

HIE-ISOLDE: First Commissioning Experience

The HIE ISOLDE project [1] reached a major milestone in October 2015, with the start of the first physics run with radioactive ion beams. This achievement was the culminating point of intense months during which the first cryomodule of the HIE ISOLDE superconducting Linac and its high-energy beam transfer lines were first installed and subsequently brought into operation. Hardware commissioning campaigns were conducted in order to define the envelope of parameters within which the machine could be operated, to test and validate software and controls, and to investigate the limitations preventing the systems to reach their design performance. Methods and main results of the first commissioning of HIE ISOLDE post accelerator, including the performance of the superconducting cavities with beam, will be reviewed in this contribution

Full remote alignment system for the High-Luminosity Large Hadron Collider HL-LHC

The High Luminosity Large Hadron Collider (HL-LHC) is an upgrade of the LHC to achieve instantaneous luminosities, a factor five larger than the LHC nominal values. During the Long Shutdown 3, scheduled between 2026 and 2028, nearly 1.2 km of accelerator components will be replaced by new ones, relying on key innovative technologies. The Full Remote Alignment System (FRAS) is being developed to perform the remote alignment of these new HL-LHC components. FRAS will enhance the accelerator performance, decrease the required orbit corrector strengths, all of this while limiting the radiation doses for surveyors working in the tunnel, therefore allowing for more frequent alignment campaigns. Innovative solutions for the remote adjustment and position determination of the components are being qualified, including the internal monitoring of the position of cold mass and crab cavities inside their cryostat. This paper will provide a status of the systems under development and qualification, from the sensors and motor assemblies to the low level / high level acquisition and control/command systems and their corresponding software