Inductive Soldering of the Junctions of the Main Superconducting Busbars of the LHC
Jacquemod
A
Poncet
A
Schauf
F
Skoczen
Blazej
Tock
J P
2004
The Large Hadron Collider (LHC) is the next world-facility for the high energy physics community, presently under construction at CERN, Geneva. The LHC will bring into collisions intense beams of protons and ions. The main components of the LHC are the twin-aperture high-field superconducting cryomagnets that will be installed in the existing 26.7-km long tunnel. They are powered in series by superconducting Nb-Ti cables. Along the machine, about 60 000 joints between superconducting cables must be realised in-situ during the installation. Ten thousands of them, rated at 13 000 A, are involved in the powering scheme of the main dipoles and quadrupoles. To meet the requirements of the cryogenic budget, an electrical resistance at operating temperature (1.9 K) lower than 0.6 nW has to be achieved. The induction soldering technology was selected for this purpose. After a brief introduction to the LHC project, the constraints and requirements are listed. Then, the applied solution is detailed. The splices of the superconducting cables (Rutherford type) form a multi-interface "composite" which, from the electrical point of view, can be modelled as a pair of equipotential surfaces separated by an equivalent conductor with the resistance localized in the interfaces. A simple model is developed and the total cross-splice resistance is compared with the experimentally observed values. Validation of the resistance of splices and the associated heat dissipation to helium at 1.9 K has been successfully performed in STRING2, the prototype of the LHC full cell. This associated to laboratory measurements confirmed the reliability level of splices initially assumed in the whole LHC budget.
PREPRINT
Electronic Systems for the Protection of Superconducting Elements in the LHC
Denz
R
Rodríguez-Mateos
F
2004
This paper gives an overview about the electronic systems used in the protection system for the LHC superconducting elements. The final design of a variety of electronic devices, where the production has recently been launched, is presented and discussed.
PREPRINT
13000 A HTS Current Leads for the LHC Accelerator
Ballarino
A
Mathot
S
Milani
D
2004
The main dipole and quadrupole circuits of the LHC accelerator will be fed via 13000 A High Temperature Superconducting (HTS) current leads. To validate the design and technological choices prior to launching the industrial production of the serial components, CERN has designed and assembled in-house a pair of 13000 A HTS current leads. The HTS part of the lead consists of a number of stacks of BSCCO 2223 tapes soldered together according to procedures defined at CERN. This report summarizes the conceptual design of the lead and the technological choices made for the different parts of the lead assembly. Particular attention is given to the HTS component on which the results of thermal, electrical, soldering and impregnation tests are reported.
PREPRINT
The Enhancement of the Magnetization of Twisted Superconducting Strands due to the Distortion of the Filament Shape
Le Naour
S
Charifoulline
Z
Wolf
R
2004
Magnetization measurement is one of acceptance criteria for strands in the LHC (Large Hadron Collider) cable production. In a magnetic field, the superconducting filaments become magnetized due to the persistent currents and generate field errors in magnets. Over 3500 strands measured, we have observed an enhancement of magnetization for strands with filaments strongly deformed. Generally the strands are designed to have filaments with a circular cross-section, however these filaments can be deformed during the fabrication process. This paper presents detailed magnetization measurements on samples with increasing filament deformation and develops a simple theory, which enables to calculate the increase of the magnetization of independent twisted filaments as function of the roundness of the filaments and compare it with measurements. However we show that interfilament coupling is important and increases with filament deformation.
PREPRINT
Superconducting Cable and Magnets for the Large Hadron Collider
Rossi
L
2004
The Large Hadron Collider (LHC) is a high energy, high luminosity particle accelerator under construction at CERN and it will be the largest application of superconductivity. Most of the existing 27 km underground tunnel will be filled with superconducting magnets, mainly 15 m long dipoles and 3 m long quadrupoles. These 1232 dipole and 400 quadrupole magnets as well as many other magnets, are wound with copper stabilized NbTi Rutherford cables and will be operated at 1.9 K by means of pressurized superfluid helium. The operating dipole field is 8.33 T; however the whole system is designed for possible operation up to 9 T. The coils are powered at about 12 kA and about 12 GJ of magnetic energy will be stored in superconducting devices. After a brief review of the main characteristics of the superconductors and of the magnets, the special measures taken to fulfill the mass production with the necessary accuracy are presented. The results on one third of the superconducting cable production and on the first fifty magnets are reported and discussed.
research-article