Todesco, E
Ferracin, P
Limits to High Field Magnets for Particle Accelerators
IEEE Trans. Appl. Supercond.
4003106
22
What is the ultimate limit to high fields in superconducting magnets for particle accelerators? In this paper we review the present status of the technology, outlining the main limitations. We first analyse the needed margin for operating a magnet in an accelerator. We then review the relation between current densities, coil widths, and fields in the magnets build so far. The issue of stress and the dependence on the coil lay-out is then discussed: a careful optimization between current density and coil width can be needed to keep the forces and associated strain within acceptable limits. The main issues related to cable lay-out (strand diameter, filament size) are then discussed. We conclude by giving a hint on the requirements on a HTS conductor, and a summary of Nb-Ti and Nb$_{3}$Sn.
eng
2012
http://cds.cern.ch/record/1425903/files/CERN-ATS-2012-052.pdf;
http://cds.cern.ch/record/1425903/files/CERN-ATS-2012-052.pdf?subformat=pdfa;
Imported from Invenio.
Xu, K
Kikuchi, A
Nakamoto, T
Ogitsu, T
Sasaki, K
Takeuchi, T
Terashima, A
Todesco, E
Tsuchiya, K
Yamamoto, A
Conceptual Design of a Large-aperture Dipole Magnet for HL-LHC Upgrade
IEEE Trans. Appl. Supercond.
4901404
22
The development of a large-aperture (120-180 mm) dipole magnet is proposed in the framework of the CERN-KEK cooperation program. The application target is the D1 magnet (separation dipoles) replacement for the HL-LHC (High Luminosity - Large Hadron Collider) upgrade. The Cos-theta type coil cross section and the shell-based structure are adopted in the conceptual design of this magnet. The nominal field is estimated to be 6-10 T at 1.9 K with a 30-mm-width coil arranged in two layers. The candidates of superconductor are Nb3Al, Nb$_{3}$Sn and Nb-Ti. We present the analytical estimation of the key parameters of this magnet, and the magnetic & mechanical simulation results of the actual design, including the field quality in the aperture, the stray field of the magnet, and the stress distribution in the coil.
eng
2012
http://cds.cern.ch/record/1425902/files/CERN-ATS-2012-051.pdf;
http://cds.cern.ch/record/1425902/files/CERN-ATS-2012-051.pdf?subformat=pdfa;
Imported from Invenio.
Hourican, M
Balhan, B
Borburgh, J
Masson, T
Design and Development of Separation Septa for the CERN PS Booster Upgrade
IEEE Trans. Appl. Supercond.
4000304
22
The CERN PS Booster project foresees the injection of 160 MeV H- ions into the booster from Linac 4. For this substantial upgrade, a system of 5 pulsed magnets (BIDIS) and 3 vertical septa (BISMV) will distribute the Linac pulses into the four-vertically separated Booster injection lines before being injected into the rings. This paper describes the magnetic calculations and the design concept that will be used in the future upgrade of the BISMV. Subsequently the mechanical design of the septa and their integration into the existing transfer line will be discussed.
eng
2012
http://cds.cern.ch/record/1425901/files/CERN-ATS-2012-050.pdf;
http://cds.cern.ch/record/1425901/files/CERN-ATS-2012-050.pdf?subformat=pdfa;
Imported from Invenio.
Bocian, D
Ambrosio, G
Barzi, E
Bossert, R
Caspi, S
Chlachidze, G
Dietderich, D
Feher, S
Felice, H
Ferracin, P
Hafalia, R
Kashikhin, V V
Lamm, M
Sabbi, G L
Turrioni, D
Wanderer, P
Zlobin, A V
Steady State Heat Deposits Modeling in the Nb$_{3}$Sn Quadrupole Magnets for the Upgrade of the LHC Inner Triplet
IEEE Trans. Appl. Supercond.
4003704
22
In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. In previous papers, a Network Model has been used to study the thermodynamic behavior of magnet coils and to calculate the quench levels in the LHC magnets for expected beam loss profiles. This model was subsequently used for thermal analysis and design optimization of Nb$_{3}$Sn quadrupole magnets, which LARP (US LHC Accelerator Research Program) is developing for possible use in the LHC luminosity upgrade. For these new magnets, the heat transport efficiency from the coil to the helium bath needs to be determined and optimized. In this paper the study of helium cooling channels and the heat evacuation scheme are presented and discussed.
eng
2012
http://cds.cern.ch/record/1425900/files/CERN-ATS-2012-049.pdf;
http://cds.cern.ch/record/1425900/files/CERN-ATS-2012-049.pdf?subformat=pdfa;
Imported from Invenio.
Deniau, L
Baynham, E
Buzio, M
Knaster, J
Savary, F
Magnetic Measurement of the Current Center Line of the Toroidal Field Coil of ITER at Room Temperature
IEEE Trans. Appl. Supercond.
9001704
22
Geometrical deformations and assembly errors in the ITER Toroidal Field (TF) coils will lead to magnetic field perturbations, which could degrade plasma confinement and eventually lead to disruption. Extensive computational studies of the influence of coil deformations and assembly errors on plasma behavior have given the basis for definition of the geometric tolerance of the Current Centre Line (CCL) of the winding pack of the TF coil. This paper describes an analysis method to establish the feasibility to measure the magnetic CCL locus of the final winding pack (WP) with accuracy better than 1 mm. The proposed method is based on arrays of gradient coils accurately mounted with respect to the WP fiducial marks and datum surfaces. The magnetic measurements will be performed at defined locations around the WP perimeter to characterize accurately the CCL locus. The analysis emphases the robustness and sensitivity of the method versus the measurement location and the TF coil 3D geometrical deformation. The analysis and proposed measurement techniques will be described in detail
eng
2012
http://cds.cern.ch/record/1425898/files/CERN-ATS-2012-048.pdf;
http://cds.cern.ch/record/1425898/files/CERN-ATS-2012-048.pdf?subformat=pdfa;
Imported from Invenio.
Ballarino, A
Bauer, P
Bi, Y
Devred, A
Ding, K
Foussat, A
Mitchell, N
Shen, G
Song, Y
Taylor, T
Yang, Y
Zhou, T
Design of the HTS Current Leads for ITER
IEEE Trans. Appl. Supercond.
4800304
22
Following the design, fabrication and test of a series of trial leads, designs of the three types of current leads required for ITER have been developed, and targeted trials of specific features are in progress on the way to fabrication and testing of prototype units. These leads are of the hybrid type with a cold section based on the use of high temperature superconductor (HTS) and a resistive section cooled by forced flow of helium gas, optimized for operation at 68 kA, 55 kA and 10 kA. The leads incorporate relevant features of the large series of current leads developed and constructed for the CERN-LHC, relevant features of the trial leads built for ITER, and additional features required to fully satisfy the exigent constraints of ITER with regard to cooling, insulation, and interfaces to feeder and powering systems. In this report a description of the design of the leads is presented, together with plans for the preparation of prototype manufacture and testing at ASIPP.
eng
2012
http://cds.cern.ch/record/1425897/files/CERN-ATS-2012-047.pdf;
http://cds.cern.ch/record/1425897/files/CERN-ATS-2012-047.pdf?subformat=pdfa;
Imported from Invenio.
Bielert, E
Verweij, A
ten Kate, H
Finite Element Modeling in 3D of the Impact of Superfluid Helium Filled Micro-channels on the Heat Transfer through LHC Type Cable Insulation
IEEE Trans. Appl. Supercond.
4701205
22
For a future luminosity upgrade of CERN’s Large Hadron Collider, a drastically improved heat removal in the inner triplet quadrupole magnets is required. One of the necessary improvements involves the cable insulation. A porous all-polyimide insulation scheme has been proposed recently. Essentially the insulation features a network of micro channels filled with superfluid helium that significantly increases the heat transfer through the insulation layer. A three dimensional Finite Element model required to simulate and study the enhanced heat transfer through the micro channels is presented here. The thermal coupling between heated cable and helium as well as the heat flux through the micro-channels are investigated. The model is validated by comparison of results with published measured data. Finally a sensitivity analysis is performed concerning the stability of the cables in magnet windings.
eng
2012
http://cds.cern.ch/record/1425896/files/CERN-ATS-2012-046.pdf;
http://cds.cern.ch/record/1425896/files/CERN-ATS-2012-046.pdf?subformat=pdfa;
Imported from Invenio.
Rossi, L
Bottura, K
de Rijk, G
Todesco, E
Advanced Accelerator Magnets for Upgrading the LHC
IEEE Trans. Appl. Supercond.
4002008
22
The Large Hadron Collider is working at about half its design value, limited by the defective splices of the magnet interconnections. While the full energy will be attained after the splice consolidation in 2014, CERN is preparing a plan for a Luminosity upgrade (High Luminosity LHC) around 2020 and has launched a pre-study for exploring an Energy upgrade (High Energy LHC) around 2030. Both upgrades strongly rely on advanced accelerator magnet technology, requiring dipoles and quadrupoles of accelerator quality and operating fields in the 11-13 T range for the luminosity upgrade and 16-20 T range for the energy upgrade. The paper will review the last ten year of Nb$_{3}$Sn accelerator magnet R&D and compare it to the needs of the upgrades and will critically assess the results of the Nb$_{3}$Sn and HTS technology and the planned R&D programs also based on the inputs of first year of LHC operation.
eng
2012
http://cds.cern.ch/record/1425893/files/CERN-ATS-2012-045.pdf;
http://cds.cern.ch/record/1425893/files/CERN-ATS-2012-045.pdf?subformat=pdfa;
Imported from Invenio.
Ravaioli, E
Dahlerup-Petersen, K
Formenti, F
Steckert, J
Thiesen, H
Verweij, A
Modeling of the Voltage Waves in the LHC Main Dipole Circuits
IEEE Trans. Appl. Supercond.
9002704
22
When a fast power abort is triggered in the LHC main dipole chain, voltage transients are generated at the output of the power converter and across the energy-extraction switches. The voltage waves propagate through the chain of 154 superconducting dipoles and can have undesired effects leading to spurious triggering of the quench protection system and firing of the quench heaters. The phase velocity of the waves travelling along the chain changes due to the inhomogeneous AC behavior of the dipoles. Furthermore, complex phenomena of reflection and superposition are present in the circuit. For these reasons analytical calculations are not sufficient for properly analyzing the circuit behavior after a fast power abort. The transients following the switch-off of the power converter and the opening of the switches are analyzed by means of a complete electrical model, developed with the Cadence© suite (PSpice© based). The model comprises all the electrical components of the circuit, additional components simulating the dipole AC behavior, and the ground lines of the circuit including its parasitic capacitances. The simulation results are presented in order to illustrate the behavior of the circuit and to assess its performance under different operating conditions. The comparison between measurement data and simulations shows a very good agreement.
eng
2012
http://cds.cern.ch/record/1425892/files/CERN-ATS-2012-044.pdf;
http://cds.cern.ch/record/1425892/files/CERN-ATS-2012-044.pdf?subformat=pdfa;
Imported from Invenio.
Ravaioli, E
Dahlerup-Petersen, k
Formenti, F
Montabonnet, V
Pojer, M
Schmidt, R
Siemko, A
Solfaroli Camillocci, A
Steckert, J
Thiesen, H
Verweij, A
Impact of the Voltage Transients after a Fast Power Abort on the Quench Detection System in the LHC Main Dipole Chain
IEEE Trans. Appl. Supercond.
9002504
22
A Fast Power Abort in the LHC superconducting main dipole circuit consists in the switch-off of the power converter and the opening of the two energy-extraction switches. Each energy-extraction unit is composed of redundant electromechanical breakers, which are opened to force the current through an extraction resistor. When a switch is opened arcing occurs in the switch and a voltage of up to 1 kV builds up across the extraction resistor with a typical ramp rate of about 80 kV/s. The subsequent voltage transient propagates through the chain of 154 dipoles and superposes on the voltage waves caused by the switch-off of the power converter. The resulting effect caused intermittent triggering of the quench protection systems along with heater firings in the magnets when the transient occurred during a ramp of the current. A delay between power converter switch-off and opening of the energy-extraction switches was introduced to prevent this effect. Furthermore, the output filters of the power converters were modified in order to damp faster the voltage waves generated after the power-converter switch-off and to lower their amplitude. Finally, snubber capacitors were added in parallel to the extraction switches to help the commutation process by reducing the arcing effect and thus smoothing the voltage transient. A set of dedicated tests has been performed in order to understand the voltage transients and to assess the impact of the circuit modifications on the quench detection system. The results have been compared to the simulations of an electrical model of the LHC main dipole circuit developed with the Cadence© suite (PSpice© based).
eng
2012
http://cds.cern.ch/record/1425495/files/CERN-ATS-2012-043.pdf;
http://cds.cern.ch/record/1425495/files/CERN-ATS-2012-043.pdf?subformat=pdfa;
Imported from Invenio.
Fessia, P
Auchmann, B
Lackner, F
Regis, F
The LHC Incident in Sector 3-4: A Simplified Mechanical Model to Explain the Mechanical Damages
IEEE Trans. Appl. Supercond.
4905304
22
On the 19th of September 2008 during powering tests of the LHC main dipole circuit in sector 3-4 an electrical fault occurred. A part of the most important resulting damages were caused by the displacements of cryostated cold masses due to the effect of an over pressurization in the insulation vacuum enclosure. The relative displacement of the interconnected units was resulting in mechanical and electrical damages. Main objects concerned were the mechanical interconnect and the magnet bus bar system. Furthermore electrical arcs induced open breaches in the helium enclosure. In this paper a simplified dynamic numerical model is described to reproduce the observed mechanical defects. In addition the analysis indicates that only a few parameters are dominating the physical quantities in this very complex event.
eng
2012
http://cds.cern.ch/record/1425494/files/CERN-ATS-2012-042.pdf;
http://cds.cern.ch/record/1425494/files/CERN-ATS-2012-042.pdf?subformat=pdfa;
Imported from Invenio.
Lackner, F
Bertinelli, F
Fessia, P
Lopez, R
Prin, H
Tock, J Ph
Development of a New Insulation Approach for the LHC Main 13 kA Interconnection Splices
IEEE Trans. Appl. Supercond.
7700204
22
In the long LHC (Large Hadron Collider) shutdown in 2013 it is foreseen to intervene on all the 13 kA interconnections in order to guarantee the necessary margin and redundancy to provide safe LHC operation at 7 TeV per beam. This implies reinforcement of the present interconnection configuration including a new insulation scheme of the busbars. The purpose of the new insulation model is to provide dielectric insulation with at least the same performance as its predecessor currently installed in the LHC machine, but in addition to contain the Lorentz forces. This paper describes the analytic and empirical approach of development to reach a new insulation concept based on state of the art materials and manufacturing techniques.
eng
2012
http://cds.cern.ch/record/1425492/files/CERN-ATS-2012-041.pdf;
http://cds.cern.ch/record/1425492/files/CERN-ATS-2012-041.pdf?subformat=pdfa;
Imported from Invenio.
Principe, R
Fessia, P
Fornasiere, E
13 kA Superconducting Busbars Manufacturing Process
IEEE Trans. Appl. Supercond.
4801604
22
In the LHC, the superconducting Main Bending magnets and Quadrupole magnets are series-connected electrically in different excitation circuits by means of superconducting busbars, carrying a maximum current of 13 kA. These superconducting busbars consist of a superconducting Rutherford cable thermally and electrically coupled to a copper section all along the length. The function of the copper section is essentially to provide an alternative path for the magnet current in case of resistive transition. The production of these components was originally outsourced. The decision to import the technology at CERN led to a global re-engineering of the standard process. Although based on the procedures adopted during the LHC construction, a few modifications and improvements have been implemented, profiting of the experience gained in the last few years. This document details the manufacturing process of the 13 kA busbars as it is actually performed at CERN, emphasizing the new solutions adopted during the first months of production.
eng
2012
http://cds.cern.ch/record/1425491/files/CERN-ATS-2012-040.pdf;
http://cds.cern.ch/record/1425491/files/CERN-ATS-2012-040.pdf?subformat=pdfa;
Imported from Invenio.
Granieri, P P
Casali, M
Bianchi, M
Breschi, M
Bottura, L
Willering, G
Analysis of Defective Interconnections of the 13 kA LHC Superconducting Bus Bars
IEEE Trans. Appl. Supercond.
4000504
22
The interconnections between Large Hadron Collider (LHC) main dipole and quadrupole magnets are made of soldered joints of two superconducting cables stabilized by a copper bus bar. The 2008 incident revealed the possible presence of defects in the interconnections of the 13 kA circuits that could lead to unprotected resistive transitions. Since then thorough experimental and numerical investigations were undertaken to determine the safe operating conditions for the LHC. This paper reports the analysis of experimental tests reproducing defective interconnections between main quadrupole magnets. A thermo-electromagnetic model was developed taking into account the complicated sample geometry. Close attention was paid to the physical description of the heat transfer towards helium, one of the main unknown parameters. The simulation results are reported in comparison with the measurements in case of static He I cooling bath. The outcome of this study constitutes a useful input to improve the stability assessment of the 13 kA bus bars interconnections.
eng
2012
http://cds.cern.ch/record/1425490/files/CERN-ATS-2012-039.pdf;
http://cds.cern.ch/record/1425490/files/CERN-ATS-2012-039.pdf?subformat=pdfa;
Imported from Invenio.
Granieri, P P
Fessia, P
Richter, D
Tommasini, D
Thermally Enhanced Cable Insulation for the Nb-Ti High Luminosity LHC Inner Triplet Model
IEEE Trans. Appl. Supercond.
7700404
22
A new concept of polyimide electrical insulation for superconducting cables of accelerator magnets was developed in the last years. Its enhanced He II permeability allows a significant improvement of the heat extraction from the coil. This cable insulation concept is used for the quadrupole magnet prototype for the insertion region of the High Luminosity - Large Hadron Collider project. It aims at pushing the limits of the Nb Ti technology to withstand high heat deposition. Cable samples wrapped with the new insulation scheme were characterized from the thermal standpoint, as well as from the electrical and mechanical ones. In particular, heat transfer measurements from insulated cables towards the helium cooling bath were performed in a coil-like configuration. Various wrapping schemes were tested in different mechanical conditions, and a model was developed to explain the experimental results. The paper summarizes the main results of all these investigations.
eng
2012
http://cds.cern.ch/record/1425489/files/CERN-ATS-2012-038.pdf;
http://cds.cern.ch/record/1425489/files/CERN-ATS-2012-038.pdf?subformat=pdfa;
Imported from Invenio.
Buzio, M
Golluccio, G
Lombardi, A
Mateo, F
Magnetic Qualification of Permanent Magnet Quadrupoles for CERN’s Linac4
IEEE Trans. Appl. Supercond.
4004304
22
This paper summarizes the results of the magnetic measurements done to qualify prototypes and series permanent- magnet quadrupoles for the new Linac4, currently in construction at CERN. The results, obtained with a combination of stretched wire and rotating coil techniques, include the individually tuned integrated field gradient, multipoles, magnetic axis and field direction. These magnets are characterized by a challengingly small 22 mm aperture diameter and we illustrate the methods adopted to guarantee instrument calibration, along with the estimated accuracies of the measured quantities and their impact on beam optics.
eng
2012
http://cds.cern.ch/record/1425488/files/CERN-ATS-2012-037.pdf;
http://cds.cern.ch/record/1425488/files/CERN-ATS-2012-037.pdf?subformat=pdfa;
Imported from Invenio.
Bauche, J
Compact Inter-cryomodule Combined Corrector Magnets for the HIE-ISOLDE Project at CERN
IEEE Trans. Appl. Supercond.
4001004
22
The new LINAC that will replace the current REX accelerating structure of the ISOLDE experiment at CERN will be made of superconducting cavities separated by small inter-tank spaces. Strong but compact normal conducting beam trajectory corrector magnets will have to be installed in these spaces without interfering with the adjacent vacuum and instrumentation equipment. This paper presents the technical solutions that have been chosen to meet these requirements, and reports about the design and manufacture of a prototype magnet.
eng
2012
http://cds.cern.ch/record/1425487/files/CERN-ATS-2012-036.pdf;
http://cds.cern.ch/record/1425487/files/CERN-ATS-2012-036.pdf?subformat=pdfa;
Imported from Invenio.
Arpaia, P
Buzio, M
Caspers, F
Golluccio, G
Oberson, D
Metrological Performance of a Ferrimagnetic Resonance Marker for the Field Control of the CERN Proton Synchrotron
IEEE Trans. Appl. Supercond.
9001904
22
In particle accelerators, “field markers” provide a digital trigger when the magnetic field crosses a given threshold. In this paper, the metrological characterization of a magnetic field marker, based on a ferrimagnetic resonance transducer referencing the flux sensed by a coil, is reported. The experimental results of a validation test campaign at the European Organization for Nuclear Research (CERN) to test the marker in static as well as fast ramping fields (up to 2.5 T/s) are illustrated. The repeatability of ±4 μT attained in the range (60 to 100) mT is very promising to increase the performance of the Proton Synchrotron accelerator at CERN.
eng
2012
http://cds.cern.ch/record/1425484/files/CERN-ATS-2012-035.pdf;
http://cds.cern.ch/record/1425484/files/CERN-ATS-2012-035.pdf?subformat=pdfa;
Imported from Invenio.
Perez, J C
Bajko, M
Bordini, B
Canfer, S
Ellwood, G
Feuvrier, J
Guinchard, M
Karppinen, M
Kokkinos, C
Manil, P
Milanese, A
Oberli, L
Regis, F
de Rijk, G
The SMC (Short Model Coil) dipole: An R&D program for Nb$_{3}$Sn accelerator magnets
IEEE Trans. Appl. Supercond.
4002704
22
The Short Model Coil (SMC) assembly has been designed, as test bench for short racetrack coils wound with Nb$_{3}$Sn cable. The mechanical structure comprises an iron yoke surrounded by a 20 mm thick aluminium alloy shell, and includes four loading pads that transmit the required pre-compression from the outer shell into the two coils. The outer shell is pre-tensioned with mechanical keys that are inserted with the help of pressurized bladders and two 30 mm diameter aluminium alloy rods provide the axial loading to the coil ends. The outer shell, the axial rods, and the coils are instrumented with strain gauges, which allow precise monitoring of the loading conditions during the assembly and at cryogenic temperature during the magnet test. Two SMC assemblies have been completed and cold tested in the frame of a European collaboration between CEA (FR), CERN and STFC (UK) and with the technical support from LBNL (US). This paper describes the main features of the SMC assembly, the experience from the dummy assemblies, the fabrication of the coils, and discusses the test results of the cold tests showing a peak field of 12.5 T at 1.9 K after training.
eng
2012
http://cds.cern.ch/record/1425482/files/CERN-ATS-2012-034.pdf;
http://cds.cern.ch/record/1425482/files/CERN-ATS-2012-034.pdf?subformat=pdfa;
Imported from Invenio.
Karppinen, M
Andreev, N
Apollinari, G
Auchmann, B
Barz, E
Bossert, R
Kashikhin, V V
Nobrega, A
Novitski, I
Rossi, L
Smekens, D
Zlobin, A V
Design of 11 T Twin-Aperture Nb$_{3}$Sn Dipole Demonstrator Magnet for LHC Upgrades
IEEE Trans. Appl. Supercond.
4901504
22
The LHC collimation upgrade foresees two additional collimators installed in the dispersion suppressor regions of points 2, 3 and 7. To obtain the necessary longitudinal space for the collimators, a solution based on an 11 T dipole as replacement of the 8.33 T LHC main dipoles is being considered. CERN and FNAL have started a joint development program to demonstrate the feasibility of Nb$_{3}$Sn technology for this purpose. The program started with the development and test of a 2-m-long single-aperture demonstrator magnet. The goal of the second phase is the design and construction of a series of 2-m-long twin-aperture demonstrator magnets with a nominal field of 11 T at 11.85 kA current. This paper describes the electromagnetic design and gives a forecast of the field quality including saturation of the iron yoke and persistent-current effects in the Nb$_{3}$Sn coils. The mechanical design concepts based on separate collared coils, assembled in a vertically split iron yoke are also discussed.
eng
2012
http://cds.cern.ch/record/1425478/files/CERN-ATS-2012-033.pdf;
http://cds.cern.ch/record/1425478/files/CERN-ATS-2012-033.pdf?subformat=pdfa;
Imported from Invenio.
Bordini, B
Bottura, L
Mondonico, G
Oberli, L
Richter, D
Seeber, B
Senatore, C
Takala, E
Valentinis, D
Extensive Characterization of the 1 mm PIT Nb$_{3}$Sn strand for the 13-T FRESCA2 Magnet
IEEE Trans. Appl. Supercond.
6000304
22
In the framework of the EuCARD program, CERN is participating in the development of a 13 T 100-mm-aperture dipole magnet to upgrade the superconducting cable test facility FRESCA at CERN. The conductor candidates for building this magnet are two 1-mm Nb$_{3}$Sn strands: the Powder In Tube (PIT) produced by Bruker-EAS and the 132/169 RRP by Oxford Superconducting Technology (OST). Recently the PIT strand has been extensively characterized by CERN in collaboration with the University of Geneva (UniGe). The critical current dependence on the magnetic field and on the axial strain e has been measured at different temperatures. Furthermore, the strand magnetization has been measured at different temperature using a vibrating sample magnetometer. Finally the magneto-thermal stability of this strand was studied by measuring the quench current between 0 T and 12 T at 1.9 K and 4.3 K. The experimental results are compared with an optimized scaling law for the critical current of Nb$_{3}$Sn strands. In this paper the results obtained for the PIT strand are summarized and discussed.
eng
2012
http://cds.cern.ch/record/1425476/files/CERN-ATS-2012-031.pdf;
http://cds.cern.ch/record/1425476/files/CERN-ATS-2012-031.pdf?subformat=pdfa;
Imported from Invenio.
Bordini, B
Bottura, L
Oberli, L
Rossi, L
Takala, E
Impact of the Residual Resistivity Ratio on the Stability of Nb$_{3}$Sn Magnets
IEEE Trans. Appl. Supercond.
4705804
22
The CERN Large Hadron Collider (LHC) is envisioned to be upgraded in 2020 to increase the luminosity of the machine. The major upgrade will consist in replacing the NbTi quadrupole magnets of the interaction regions with larger aperture magnets. The Nb$_{3}$Sn technology is the preferred option for this upgrade. The critical current density Jc of Nb$_{3}$Sn strands have reached sufficiently high values (in excess of 3000 A/mm2 at 12 T and 4.2 K) allowing larger aperture/stronger field magnets. Nevertheless, such large Jc values may cause magneto-thermal instabilities that can drastically reduce the conductor performance by quenching the superconductor prematurely. In Nb$_{3}$Sn magnets, a relevant parameter for preventing premature quenches induced by magneto-thermal instabilities is the Residual Resistivity Ratio (RRR) of the conductor stabilizing copper. An experimental and theoretical study was carried out to investigate how much the value of the RRR affects the magnet stability and to identify the proper conductor specifications. In this paper the main results are presented and discussed
eng
2012
http://cds.cern.ch/record/1425474/files/CERN-ATS-2012-030.pdf;
http://cds.cern.ch/record/1425474/files/CERN-ATS-2012-030.pdf?subformat=pdfa;
Imported from Invenio.
Kokkinos, C
Bajko, M
Guinchard, M
Karppinen, M
Manil, P
Perez, J C
Regis, F
The SMC (Short Model Coil) Nb$_{3}$Sn Program: FE Analysis with 3D Modeling
IEEE Trans. Appl. Supercond.
4900705
22
The SMC (Short Model Coil) project aims at testing superconducting coils in racetrack configuration, wound with Nb$_{3}$Sn cable. The degradation of the magnetic properties of the cable is studied by applying different levels of pre-stress. It is an essential step in the validation of procedures for the construction of superconducting magnets with high performance conductor. Two SMC assemblies have been completed and cold tested in the frame of a European collaboration between CEA (FR), CERN and STFC (UK), with the technical support from LBNL (US). The second assembly showed remarkable good quench results, reaching a peak field of 12.5T. This paper details the new 3D modeling method of the SMC, implemented using the ANSYS® Workbench environment. Advanced computer-aided-design (CAD) tools are combined with multi-physics Finite Element Analyses (FEA), in the same integrated graphic interface, forming a fully parametric model that enables simulation driven development of the SMC project. The magnetic and structural model is described and the results are compared with the experimental data from the strain gauges, which monitor the mechanical strain of the structure.
eng
2012
http://cds.cern.ch/record/1425472/files/CERN-ATS-2012-029.pdf;
http://cds.cern.ch/record/1425472/files/CERN-ATS-2012-029.pdf?subformat=pdfa;
Imported from Invenio.
Borgnolutti, F
Auchmann, B
Bottura, L
Carra, F
Foffano, G
Gomes De Faria, J M
Kalouguine, O
Kirby, G
Lopez, C
Tommasini, D
Construction of the CERN Fast Cycled Superconducting Dipole Magnet Prototype
IEEE Trans. Appl. Supercond.
4001604
22
CERN is pursuing a small scale R&D on a fast cycled superconducting dipole magnet (FCM) of interest for the upgrade plan of the LHC accelerator complex. The FCM dipole prototype being built has a number of novel features if compared to other magnets for similar applications. In this paper we describe the magnet design, and its expected performance, focusing especially on the novel features (magnetic circuit, mechanical supports, cooling) and on the details of the manufacturing procedure (coil winding and impregnation, joints, instrumentation and quench protection).
eng
2012
http://cds.cern.ch/record/1425471/files/CERN-ATS-2012-028.pdf;
http://cds.cern.ch/record/1425471/files/CERN-ATS-2012-028.pdf?subformat=pdfa;
Imported from Invenio.
Kirby, G A
Auchmann, B
Bielert, E
Fessia, P
Karppinen, M
Lepoittevin, B
Lorin, C
Luzieux, S
Perez, J C
Russenschuck, S
Sahner, T
Smekens, D
Segreti, M
Durante, M
Engineering Design and Manufacturing Challenges for a Wide-Aperture, Superconducting Quadrupole Magnet
IEEE Trans. Appl. Supercond.
4001804
22
The design and construction of a wide-aperture, superconducting quadrupole magnet for the LHC insertion region is part of a study towards a luminosity upgrade of the LHC at CERN. The engineering design of components and tooling, the procurement, and the construction work presented in this paper includes innovative features such as more porous cable insulation, a new collar structure allowing horizontal assembly with a hydraulic collaring press, tuning shims for the adjustment of field quality, a fishbone like structure for the ground-plane insulation, and an improved quench-heater design. Rapid prototyping of coil-end spacers and trial-coil winding led to improved shapes, thus avoiding the need to impregnate the ends with epoxy resin, which would block the circulation of helium. The magnet construction follows established procedures for the curing and assembly of the coils, in order to match the workflow established in CERN’s ”large magnet facility.” This requirement led to the design and procurement of a hydraulic press allowing for both a vertical and a horizontal position of the coil-collar pack, as well as a collapsible assembly mandrel, which guarantees the pack’s four-fold symmetry during collaring. The assembly process has been validated with the construction of two short models, instrumented with strain gauges and capacitive pressure transducers. This also determines the final parameters for coil curing and shim sizes.
eng
2012
http://cds.cern.ch/record/1425459/files/CERN-ATS-2012-027.pdf;
http://cds.cern.ch/record/1425459/files/CERN-ATS-2012-027.pdf?subformat=pdfa;
Imported from Invenio.
Hagen, P
Auchmann, B
Todesco, E
Comparison between Electromagnetic Models and Magnetic Measurements in the LHC Magnets
IEEE Trans. Appl. Supercond.
9000104
22
We present a comparison between the electromagnetic model of the main LHC magnets and the magnetic measurements carried out during production. The goal of this study is to test the validity range of the model and to uncover discrepancies between models and reality. We de-compose the field computation into several parts: geometry (coils, collars, and yoke), persistent currents in the superconducting cables, and saturation of the iron yoke. For each component we give the agreement between model and measurements. This gives an indication about the precision one can expect to obtain from a simulation code - this information is particularly relevant for future upgrades of the LHC
eng
2012
http://cds.cern.ch/record/1425458/files/CERN-ATS-2012-026.pdf;
http://cds.cern.ch/record/1425458/files/CERN-ATS-2012-026.pdf?subformat=pdfa;
Imported from Invenio.
de Rijk, G
The EuCARD High Field Magnet Project
IEEE Trans. Appl. Supercond.
4301204
22
In the EC FP7 program EuCARD (European Coordination for Accelerator Research & Development) the subject of work-package 7 is High Field Magnets. The aim of the HFM work-package is to develop technologies for magnets in the range 13 T - 20 T for accelerator applications like HL-LHC and HE-LHC. The work-package foresees construction of a 13 T dipole with an aperture of 100 mm, an HTS dipole insert with deltaB = 6 T, an HTS current link and a helical undulator. The work-package has 12 European partners and the funding is shared between the EC and the partners. This contribution describes the aims of the work-package, the status of the work and the structure of the collaboration.
eng
2012
http://cds.cern.ch/record/1425456/files/CERN-ATS-2012-025.pdf;
http://cds.cern.ch/record/1425456/files/CERN-ATS-2012-025.pdf?subformat=pdfa;
Imported from Invenio.
Milanese, A
Devaux, M
Durante, M
Manil, P
Perez, J C
Rifflet, J M
de Rijk, G
Rondeaux, F
Design of the EuCARD High-Field Model Dipole Magnet FRESCA2
IEEE Trans. Appl. Supercond.
4002604
22
This paper reports on the design of FRESCA2, a dipole magnet model wound with Nb$_{3}$Sn Rutherford cable. This magnet is one of the deliverables of the High Field Magnets work package of the European FP7-EuCARD project. The nominal magnetic flux density of 13 Tesla in a 100 mm bore will make it suitable for upgrading the FRESCA cable test facility at CERN. The magnetic layout is based on a block coil, with four layers per pole. The mechanical structure is designed to provide adequate pre-stress, through the use of bladders, keys and an aluminum alloy shrinking cylinder.
eng
2012
http://cds.cern.ch/record/1425455/files/CERN-ATS-2012-024.pdf;
http://cds.cern.ch/record/1425455/files/CERN-ATS-2012-024.pdf?subformat=pdfa;
Imported from Invenio.
Tommasini, D
Buzio, M
Thonet, P
Vorozhtsov, A
Design, Manufacture and Measurements of Permanent Quadrupole Magnets for Linac4
IEEE Trans. Appl. Supercond.
4000704
22
Compact quadrupole magnets are required for the CCDTL (Cell-Coupled Drift Tube Linac) of Linac 4, a 160 MeV linear accelerator of negative hydrogen ions which will replace the old 50 MeV proton Linac2 at CERN. The magnets, of an overall physical length of 140 mm and an aperture diameter of 45 mm, are based on Sm2Co17 blocks and can provide an integrated gradient of up to 1.6 Tesla. The magnetic field quality is determined by 4 ferromagnetic pole tips, aligned together with the permanent magnets blocks inside a structure made in a single piece. Tuning bars allow to individually trim the magnetic flux provided by each pole, to correct possible differences between blocks and to modify the field gradient intensity within about 20% of the nominal value. The paper describes and discusses the design, manufacture and magnetic measurements of a first prototype magnet.
eng
2012
http://cds.cern.ch/record/1425452/files/CERN-ATS-2012-023.pdf;
http://cds.cern.ch/record/1425452/files/CERN-ATS-2012-023.pdf?subformat=pdfa;
Imported from Invenio.
Tommasini, D
Buzio, M
Chritin, R
Dipole Magnets for the LHeC Ring-Ring Option
IEEE Trans. Appl. Supercond.
4000203
22
The Ring-Ring option of a Large Hadron electron Collider (LHeC) requires 3080 bending magnets, 5.35-meter-long each providing a magnetic field ranging from 0.0127 T at 10 GeV to 0.0763 T at 60 GeV. Main issues in the design of these magnets are the very low injection field, constituting a challenge in achieving a satisfactory field reproducibility from cycle to cycle, and the required compactness to fit in the existing LHC tunnel. This paper describes and discusses a design meeting these requirements, together with its experimental validation by the manufacture and measurement of a 400-mm-long magnet model.
eng
2012
http://cds.cern.ch/record/1425451/files/CERN-ATS-2012-022.pdf;
http://cds.cern.ch/record/1425451/files/CERN-ATS-2012-022.pdf?subformat=pdfa;
Imported from Invenio.
Superconducting magnets can exhibit training quenches during successive powering to reaching nominal performance. The slip–stick motion of the conductors is considered to be one of the mechanisms of training. In this paper, we present a simple quantitative model where the training is described as a discrete dynamical system matching the equilibrium between the energy margin of the superconducting cable and the frictional energy released during the conductor motion. The model can be explicitly solved in the linearized case, showing that the short sample limit is reached via a power law. Training phenomena have a large random component. A large set of data of the large hadron collider magnet tests is postprocessed according to previously defined methods to extract an average training curve for dipoles and quadrupoles. These curves show the asymptotic power law predicted by the model. The curves are then fit through the model, which has two free parameters. The model shows good agreement over a large range, but it fails to describe the very initial part of the training.
eng
2011
http://cds.cern.ch/record/1415479/files/CERN-ATS-2012-003.pdf;
http://cds.cern.ch/record/1415479/files/CERN-ATS-2012-003.pdf?subformat=pdfa;
http://cds.cern.ch/record/1415479/files/06007058.pdf;
Imported from Invenio.
Takala, E
Bordini, B
Bremer, J
Balle, C
Bottura, L
Rossi, L
An Experimental Setup to Measure the Minimum Trigger Energy for Magneto-Thermal Instability in Nb$_{3}$Sn Strands
IEEE Trans. Appl. Supercond.
6000704
22
Magneto-thermal instability may affect high critical current density Nb$_{3}$Sn superconducting strands that can quench even though the transport current is low compared to the critical current with important implications in the design of next generation superconducting magnets. The instability is initiated by a small perturbation energy which is considerably lower than the Minimum Quench Energy (MQE). At CERN, a new experimental setup was developed to measure the smallest perturbation energy (Minimum Trigger Energy, MTE) which is able to trigger the magneto-thermal instability in superconducting Nb$_{3}$Sn-strands. The setup is based on Q-switched laser technology which is able to provide a localized perturbation in nano-second time scale. Using this technique the energy deposition into the strand is well defined and reliable. The laser is located outside the cryostat at room temperature. The beam is guided from room temperature on to the superconducting strand by using a UV-enhanced fused silica fibre. The strand is mounted on a VAMAS barrel. A part of the beam’s energy is absorbed into the strand acting as the trigger energy for the magneto-thermal instability. In this paper the experimental setup and the calibration of the absorbed energy is presented
eng
2012
http://cds.cern.ch/record/1425477/files/CERN-ATS-2012-032.pdf;
http://cds.cern.ch/record/1425477/files/CERN-ATS-2012-032.pdf?subformat=pdfa;
Imported from Invenio.