5 December 2002 - Radiation tolerance assurance of LHC machine electronicsby Thijs Wijnands, SL Division ( refer to the RADWG HomePage) - A substantial amount of electronics equipment will be installed in the LHC tunnel and underground areas. Some of the equipment will be subject to radiation from beam losses. For several years electronics has been qualified in radiation test facilities. In the presentation the basic mechanisms for radiation damage on electronics will be explained (TID, NIEL and SEE). Some recent experimental results from the TCC2 radiation area of the SPS, from PSI and from Louvain will be given. The relevance of such tests to the operation of the equipment in the LHC will be discussed (radiation levels, safety factors, test methods and test facilities).
7 November 2002 - The manufacturing and test folder (MTF): description and examples of the application to the LHCby Sonia Mallon-Amerigo and Elena Manola-Poggioli /EST Division (EDMS Document No. 362149)
The MTF application is an integrated part of the Engineering Data Management System (EDMS) at CERN and was developed to capture manufacturing and test data for the LHC project. The basic requirement is to provide traceability for large quantities of complex parts manufactured in many different places and countries.This implies that a wide range of data, such as information about the manufacturer, the manufacturing procedures, test results, non-conformity reports and related documentation, must be stored and retrieved from data repositories around the world. As of about one year ago, the MTF application is in production and manages already an impressive amount of vital technical information about the LHC equipment. This seminar will present the MTF application and describe its practical use at the LHC.
24 October 2002 - Logistics of cryomagnet transport for the LHCby P. Bonnal /AC - The cryomagnet transportation into the LHC tunnel is scheduled to take place from March 2004 to August 2006. At this time the installation of all other LHC equipment will be taking place. To know whether it is possible to transport approximately 1750 cryomagnets to their specific position in the LHC tunnel without interfering with installation activities, a discrete-event simulation has been performed. Such a simulation is required to demonstrate the feasibility of cryomagnet transportation within the time frame, available resources and other boundary conditions.
10 October 2002 - Steering the field quality of the LHC dipolesby Ezio Todesco / LHC Division - The magnetic field of the LHC main dipoles must satisfy tight beam dynamics specifications to ensure good performance of the machine. After recalling the main features of the multipolar expansion of magnetic field, we summarize the specifications from beam dynamics and describe the corrective actions to improve field quality on prototypes and pre-series magnets. Magnetic measurements are also a powerful tool to control and follow up the production: we discuss how holding points have been organized and what critical cases have been found.
26 September 2002 - The alignment of the LHC components in the tunnelby Jean-Pierre Quesnel/EST (file > 25 MB) - Recently, the metrological work performed on the cryo-magnets before installation in the tunnel has been presented in a previous LHC Project Seminar by D.Missiaen and M. Bajko. In this seminar the metrological work on components in the tunnel is discussed. After a brief review of the main aspects of the metrology on large scale objects, such as a particle accelerator, the scenario of the metrological operations to be performed is presented, as well as the techniques to be used. Emphasis is given to the quality control aspects and the follow-up of the operations to be performed, and on the accuracy expected.
20 June 2002 - Reliability oriented optimisation of the magnet interconnects in the LHCby C. Garion - To achieve the maximum beam energy in the LHC, the accumulated length of spatial zones dedicated to the interconnections between the main cryo-magnets has been limited to 3 % of the total magnetic length in the Arcs and Dispersion Suppressors. Such a low ratio leads to a very compact design of systems and sub-systems situated in the LHC interconnections. The requirements concerning reliability of the LHC interconnections are very tight since the availability of the collider for physics cannot be compromised. One of the most important systems housed in the LHC interconnections is the thermal contraction/expansion compensation system (bellows expansion joints). In order to cope with the space limitations a deliberate choice, supported by a mathematical optimisation, was made and the LHC bellows expansion joints work in highly inelastic regime called the low-cycle fatigue. All deformation developed during cool-down and warm-up of the collider is localised in the interconnections (the accumulated value of thermal contraction approaches 70 m for LHC Arcs and DS). The failure modes, related to the response of the compensation system at cryogenic temperatures, are grouped into three categories: material failures (micro-damage and phase transformations), structural failures (instability modes) and fatigue failures (low cycle fatigue). All the above listed phenomena, which influence the reliability of the LHC interconnections, are analysed and evaluated.
23 May 2002 - Geometry and Metrology for LHC cryomagnetsby M. Bajko and D. Missiaen - The requirements for the dipole cold mass geometry stem from the LHC beam optics and from mechanical deformation limits in the interconnection zone. To provide the largest possible mechanical aperture, the dipole cold masses should match the circular trajectory of the beams. The method to accurately measure the geometry of the cold mass by measuring the cold bore tube axes using a high accuracy 3D system based on optical methods is presented, and results obtained for several cold masses are given. After the magnets arrive at CERN, metrological measurements are made for 10% of the cryo-dipoles in order to verify that the transport does not affect the geometry. The fiducialisation and the measurement of the tube position at the extremities of the magnet will be explained. The problem of the cold mass stability with respect to its cryostat will be addressed. For the SSS, the positioning of cold bore tubes and beam position monitor (BPM) supports in industry, the alignment of the drift tube and BPM at CERN, and the measurement of the position of all other tubes at each extremity require additional metrological measurements.
30 April 2002 - The LHC projectby L. Evans - At the halfway point in the construction of the LHC, the project is now moving from the design and procurement phase to the installation phase, which officially started on 1st March. An overview of the progress of the project is given and the final schedule for installation and commissioning is discussed.
; 25 April 2002 - Highlights of ECLOUD'02 Workshopby F. Zimmermann - A mini-workshop on electron-cloud simulations for proton and positron beams (ECLOUD'02) was held at CERN from April 15 to 18. The participation of about 50 scientists from more than 10 institutions reflects the importance of electron-cloud effects not only for the LHC, but also for B factories, high-intensity proton machines, and linear colliders. I will present the workshop results, summarize the discussions, and mention possible implications for the LHC, SPS, and PS.
11 April 2002- Cryogenic testing at the Central Cryogenic Laboratoryby G. Vandoni - The Central Cryogenic Laboratory (Cryolab) provides CERN-wide support for small-scale cryogenics up to the size of an LHC dipole. With more than 30 projects running every year, the Cryolab plays a significant role in cryogenic R&D, prototype testing and production follow-up. Thanks to the acquired experience with the diversity of the problems presented by the users, the Cryolab gives assistance in finding the appropriate measuring methods and help for the comprehension of thermal phenomena at low temperature. Calculation, bibliography, and facilities for material measurements support the tests. To illustrate this diversity, we analyze a few recent LHC-related projects, such as the assessment of the thermal performance of multi-layer insulation for the LHC cryostats, the evaluation of low temperature material properties during development and production follow-up, and the measurements of the Kapitza impedance and how to exploit this effect to size heat losses at superfluid helium temperature.
14 March 2002 - Mechanics and field quality in the main LHC dipoleby P. Ferracin - In the LHC superconducting dipole, the magnetic field strongly depends on the position of the coil conductors. The coils are clamped by a mechanical structure which compresses the cables to avoid conductor movements when the magnet is energised. During the assembly and the cool-down, stress changes affect the coil geometry, thus modifying field quality. We present measurements of the thermo-mechanical properties of the coil and their implementation in a finite element model of the dipole mechanical behaviour. The magneto-mechanical model has allowed a deep analysis of the field quality in the pre-series dipoles and of the available corrective strategies. We finally show how the model has provided a precise reconstruction of an assembly error observed in the dipole production.
ALSO presented on 14 March 2002
Preliminary results of coil cross-section correction in the main LHC dipoleby W. Scandale and E. Todesco
28 February 2002 - Report from LHC String 2 Run 1by R. Saban / AC - F. Bordry, L. Bottura, C. Rathjen, F. Rodriguez-Mateos, R. Saban, L. Serio, B. Skoczen for the String Team - After the commissioning and the first powering of the main circuits in autumn 2001, a short yet vigorous experimental program was carried-out to validate the final design choices for the technical systems of LHC. This program included the investigation of thermo-hydraulics of quenches, quench propagation, power converter controls and tracking between power converters, sum currents induced in the interconnects after a quench. Parameters significant for the LHC, such as heat loads, were also measured.
After a brief description of the configuration of all the systems and a summary of the run, the experiments, their objectives, results and conclusions are reported.
17 January 2002 - Qualification of the geo-magnetic cold measurement system for the LHC SSSby P. Schnizer - The LHC arc quadrupoles have to be measured in cold conditions with an outstanding precision. We aim to reach a reproducibility of 1.5 . 10-4 on the field integral, while for the harmonic content we aim at 2 ppm of the main field. A scanner allowing the simultaneous measurement of the field axis geometry and of the field strength and quality (a geo-magnetic measurement) is the most complex system in the whole pool foreseen for the cold tests of the arc quadrupoles. In this talk I will show that the system as it stands fulfils the requirements for the magnetic measurement and the magnetic axis and thus provides a unique versatile equipment. The assessment was performed based on experimental results, direct calibration and using a new simulation tool. The main defects that affect a magnetic measurement are mechanical torsion and vibration of moving parts, electrical noise and power supply ripple, as well as their arbitrary combination.
22 November 2001 - Radiation environment in the main ring of the LHCby C. Fynbo - All components placed in the LHC will suffer from radiation damage during machine operation. Some will also be situated in a highly radioactive environment, thus reliable construction materials and electronics which are sufficiently radiation hard to survive LHC operation will be required. In order to judge the necessary component radiation hardness, detailed information regarding the expected radiation environment in the LHC is essential. This presentation is intended to provide an overview of the data which are now available concerning the expected radiation doses and particle fluences to be found in the main ring of the LHC. An in-depth discussion of the radiation environment in the LHC arcs will be given covering the expected annual dose due to beam-gas interactions, ratios of particle fluence:dose in the tunnel and an estimate of the extra dose in the arc sections due to point losses. Data will also be made available for the dispersion suppressor regions regarding the annual dose downstream of the high luminosity interaction points IP1&5 and discussion made of extension to regions DS3&7. Extra detail regarding the quench diodes in the arcs and the above dispersion regions will also be available.
8th November 2001 - Beam-based measurement of the non-linearity of the RHIC low-beta quadrupole magnetic field.by J.P. Koutchouk - In both RHIC and LHC, the low-beta quadrupole magnetic field is foreseen to require correction up to the dodecapole order. The best strategy to set the multipole correctors is to use beam diagnostics. The method tested at RHIC relies on the measurement of the feed-down of higher-order perturbations to the closed orbit and betatron tune orders. I will summarize in an informal talk the principle of the method, the experimental results obtained a few weeks ago (amongst which the measurement of a dodecapole field) and their estimated accuracy. The technical measurement issues which can be relevant to LHC will be analysed.
1st November 2001 - Energy extraction for the LHC supercoducting magnets - a vital part of the protection systems.by K. Dahlerup-Petersen - In case of a quench in one of the LHC superconducting elements, fast and reliable extraction of the magnetic energy represents an important feature of the protection system. Together with other protection elements, the energy extraction facilities protect the magnets from potentially massive damage. More than 200 energy extraction facilities will be installed for the 13 kA and 600 A electrical circuits of the LHC in order to extract the stored energy of more than 10 GJoule. Concept, design and manufacturing of the system will be discussed. Testing of prototype components will be described. Security, redundancy and radiation issues will be highlighted. The production of the 300 tons of components, their nstallation in the LHC underground locations as well as operational aspects, such as control and supervision, will also be described.
12th July 2001- The Cryogenic Distribution Line for LHCby G. Riddone and R. Trant - The LHC superconducting magnets will operate in superfluid helium below 2K. The cryogenic distribution scheme for each of the eight sectors, individually served by a refrigeration plant, is based on a separate Cryogenic Distribution Line (QRL). Via the QRL helium at different temperatures and pressures feeds the local cooling loops. With an overall length of 25.8 km the QRL has a very critical cost-to-performance ratio. Therefore three pre-series test cells (each ~112 m long) were built in industry and extensively tested at CERN. The QRL layout, considering the cryogenic flow schemes, tunnel installation and other aspects, as well as the tests performed on the pre-series test cells will be presented
31st May 2001 - Quench Simulations and Measurements of LHC Superconducting Magnets and Busbarsby F. Sonnemann For the LHC superconducting magnets and busbars a detailed understanding of the quench process requires the combination of thermo-hydraulic and electrodynamic effects. The quench process has been studied by analysing quench data of various prototype busbars and magnets. A numerical program (SPQR - Simulation Program for Quench Research) was developed to evaluate temperature and voltage distributions during a quench as a function of space and time. The model includes the impact of induced eddy currents, heat transfer through an insulation layer into helium and forced quenching by heaters. The simulation outcome and the experimental results will be compared and some of the consequences for the LHC protection system will be presented.
26th April 2001 - Advanced Cryogenics process Control: Non-linear Predictive Controlby E. Blanco (>10 MB file) / LHC Division - Most of the industrial processes are typically operated using linear controllers, although it is well known that many of these processes are highly nonlinear. Proportional, Integral and Derivative (PID) regulation is still the preferred control method in industry but "modern" advanced control techniques are emerging and have already proven significant improvements over PID performance in processes where dynamics are highly complex and/or profit maximization is an issue.
Cryogenic processes dynamics are inherently very nonlinear and present a fertile ground for applying modern control algorithms. These algorithms are intended to be better at handling undesirable features such us inverse response, variable dead time and non-self regulating behaviour. A nonlinear predictive controller for the superconducting magnet temperature regulation has been developed, commissioned and fully validated on the LHC String Test and the Inner Triplet (IT-HXTU). The followed methodology is a very illustrative procedure of how to successfully apply these optimization techniques to other areas of interest.
19th April 2001 - Modeling of transmission line effects for a string of LHC dipole magnetsby F. Bourgeois / Division LHC - Each LHC sector is comprised of 154 dipole magnets, and transmission line effects and their impact on magnet protection and beam operation need to be considered. This seminar will discuss the synthesis methodology used for the electrical modeling of dipole magnets as a passive device into an R/L/C circuit. Amplitude and phase measurements of the device under test are used to find sets of poles and zeros approximating its electrical behavior through the whole frequency bandwidth. An electrically compatible R/L/C model can then be synthesized by means of the combination of two conventional algorithms. Some consequences for the instrumentation of a dipole magnet string will be presented. Other areas of application of the proposed methodology will be briefly discussed.
8th February 2001 - Superconducting Nb3Sn accelerator magnetsby A. den Ouden / Univ. of Twente - With the LHC the limits of NbTi superconductors have been reached. For future accelerators (VLHC, muon collider) not only the accelerator dimensions but also the main dipole field must be increased, preferably in the range of 11-14 T. With two experimental dipole magnets employing Nb3Sn superconductors it has already been demonstrated that these expectations appear to be realistic: - 11.3 T at 4.4 K, dipole magnet MSUT (Univ. of Twente, STW, NIKHEF, CERN) - 13.3 T at 1.8 K, dipole magnet D-20 (LBNL,USA). In this talk the opportunities and challenges with respect to higher fields and current densities in accelerator magnets employing Nb3Sn superconductors will be discussed. The development and test results of the dipole magnet MSUT illustrates the technological issues and the need for dedicated R&D in order to obtain Nb3Sn magnets within accelerator specifications. Finally, current developments in the field of magnets and conductors will show that actual implementation of Nb3Sn magnets in accelerators can be expected within a few years.
20th April 2000 - "Results from the LHC inner triplet quadrupole model magnet program at Fermilabby J. Kerby and J. Strait / FNAL - Fermilab has recently completed a series of 2 m long model magnets to develop and prove the design of the MQXB Inner Triplet Quadrupoles for the LHC. The MQXB has a 70 mm bore, and provides a gradient of 215T/m at IP2/8 and 205T/m at IP1/5. In the high luminosity interaction regions, the magnets are subjected to large energy deposition from particles generated by the collisions at the IP. The presentation will include the quench performance, thermal margin, and field quality demonstrated in the model magnets. Furthermore, the series of model magnets was constructed with a number of design and production process variants, and the effect of these variations on magnet performance will be discussed.