Kirby, G A Ostojic, R Taylor, T M Yamamoto, A Tsuchiya, K Higashi, N Nakamoto, T Ogitsu, T Ohuchi, N Shintomi, T Terashima, A 1997 1997 The conceptual design study of a high gradient super conducting insertion quadrupole magnet has been carried out in collaboration between KEK and CERN for the Large Hadron Collider (LHC) to be built at CERN. A model magnet design has been optimized to provide a nominal design field gradient of 240 T/m with a bore aperture of 70 mm and an operational field gradient of 225 T/m at 1.9 K under radiation environment with a beam energy deposit of several watts per meter in the superconducting coils. The design and its optimization process are discussed. Verweij, A P Oomen, M P ten Kate, H H J 10.1109/77.614482 1996 1996 In this paper the existence of so called Boundary-Induced Coupling Currents (BICCs) is experimentally demonstrated in a 1.3 m long Rutherford-type cable. These BICCs are induced by applying a field change locally onto the cable and can be represented by a non-uniform current distribution between the strands of the cable during and after the field sweep. In order to better understand the characteristic time, amplitude and characteristic length of these coupling currents and the parameters by which they are influenced, a special set-up has been built. With this set-up it is possible to scan the field induced by the BICCs along the full length of a Rutherford-type cable. Special attention is paid on the influence of the contact resistance between crossing strands on the characteristics of the BICCs, and results are presented where parts of the cable are soldered, simulating the joints of a coil. Verweij, A P IEEE Trans.Appl.Supercond. 10.1109/77.614606 723-726 7 2 1997 1996 In this paper it is shown that spatial distributions in the field-sweep rate and in the contact resistances along the length of Rutherford-type cables provoke a non-uniform current distribution during and after a field sweep. This process is described by means of Boundary-Induced Coupling Currents (BICCs) flowing through the strands over lengths far larger than the cable pitch. The dependence of the BICCs on the cable parameters (geometry, contact resistances etc.) is investigated by modelling the cable by means of a comprehensive network model. Working formulas are presented that give a first estimate of the characteristic time, the amplitude, and the characteristic length of the BICCs in any kind of magnet wound from a Rutherford-type cable. The results of these calculations show that BICCs can attain large values in multistrand cables, and hence play an important role in the ramp-rate limitation and field quality of high-field accelerator magnets even if the field-sweep rate is small. Siegel, N 10.1109/77.614478 1996 1996 The Large Hadron Collider (LHC), approved by the CERN Council in December 1994, is a 7+7 TeV proton accelerator-collider, to be installed in the existing 27 km long LEP tunnel. It will represent a unique research facility for particle physics, allowing proton-proton collisions with a luminosity of 10^34 cm^-2s^-1 capable of providing also heavy ion (Pb-Pb) collisions with a luminosity of 10^27 cm^-2s^-1, using the existing CERN heavy ion source. The main technological challenges of the machine are the superconducting magnet system, in total over 8¹000 magnet units immersed in superfluid helium, with the lattice dipoles operating at 8.4 T, and the very large cryogenic system, which maintains the entire string of cryomagnets at its working temperature below 2 K. The paper discusses briefly the main issues which have led to the present layout of the LHC, gives an overview of the different machine components and characteristics and describes in more detail the recent development work and results of the LHC magnet program. Wilson, M N Wolf, R IEEE Trans.Appl.Supercond. 10.1109/77.614662 950-953 7 2 1997 1996 The Minimum Quench Energy MQE of a conductor may give some indication about the likelihood of training in magnets. We have used a numerical solution of the heat flow equation to calculate the MQE of a single superconducting wire and have found the results to be in good agreement with experiment. This model was then extended to an approximate representation of Rutherford cable by including current and heat transfer between strands. Reasonable agreement with experiment has been found, although in some cases it appears that the effective thermal contact between strands is greater than expected from electrical resistance measurements. Adam, J D Leroy, D Oberli, L R Richter, D Wilson, M N Wolf, R Higley, H C McInturff, A D Scanlan, R M Nijhuis, A ten Kate, H H J Wessel, S IEEE Trans. Appl. Supercond. 10.1109/77.614664 958-961 7 2 1997 1996 Putting a resistive core into the center of a Rutherford cable increases resistance between strands in the crossover direction, which greatly reduces the coupling currents, even when the resistance to adjacent turns remains small. This allows one to improve stability by soldering strands together or using porous metal, without incurring a penalty of increased coupling. We describe our manufacturing methods and an experimental measurement of coupling. Wolf, R Leroy, D Richter, D Verweij, A P Walckiers, L 10.1109/77.614623 1996 1996 Loss and field errors due to ramping in LHC accelerator dipole magnets are mainly determined by the contact resistance between the strands of the magnet cable. It is therefore important to develop cables having sufficiently high contact resistance in the magnets in order to ease operation of the future LHC collider during ramping. In this paper the contact resistance Rc and its distribution in the magnet windings are determined for several dipole prototypes using both the measured loss and field errors during ramping of the magnet. We compare these results with interstrand contact resistance measurements made on short samples of the cables used in these magnets. Wilson, M N 10.1109/77.614607 1996 1996 Superconducting magnets have enabled the construction of some very large accelerators to explore the structure of matter at the highest energies. Small superconducting accelerators are used in medicine and industry. We review the special demands which accelerators make on superconductor technology, describe the magnets for large and small accelerators and mention some exciting prospects for the future. Depond, J M Leroy, D Oberli, L R Richter, D 10.1109/77.614622 1996 1996 The contact resistance (crossing and adjacent) between the strands of Rutherford type superconducting cables has been proven to be an essential parameter for the behaviour of the main magnets in accelerators like the LHC. A strong development program has been launched at CERN. Contact resistances were measured by means of a DC method at 4.2 K. The strand deformation and the chemical conditions at the contacts were analyzed in order to interpret the electrical resistances measured by a 3 contacts method on individual strands as well as the resistances measured independently on cables. Richter, D Adam, J D Depond, J M Leroy, D Oberli, L R IEEE Trans. Appl. Supercond. 10.1109/77.614621 786-792 7 2 1997 1996 In the LHC main magnets, using Rutherford type cable, the eddy current loss and dynamic magnetic field error depend largely on the electrical resistance between crossing (Rc) and adjacent (Ra) strands. Cables made of strands with pre-selected coatings have been studied at low temperature using a DC electrical method. The significance of the inter-strand contact is explained. The properties of resistive barriers, the DC method used for the resistance measurement on the cable, and sample preparation are described. Finally the resistances are presented under various conditions, and the effect is discussed that the cable treatment has on the contact resistance. Kirby, G A Ostojic, R Taylor, T M Trinquart, G 10.1109/77.614566 1996 1996 The LHC dump insertion features a pair of superconducting quadrupoles located on either side of a 340 m long straight section. Two horizontally deflecting kickers, located in between the quadrupole pairs, and a septum in the centre of the insertion, vertically deflect the two counter-rotating beams past the quadrupoles on the downstream sides, and into the dump areas. Due to the layout, the optical ß function in the quadrupoles is around 640 m, the largest around the LHC at injection. The quadrupoles must therefore have enlarged aperture and specially designed cryostats to allow for the safe passage of both the circulating and ejected beams. In this paper we present the design of the twin aperture dump quadrupole based on the 70 mm four layer coil proposed for the LHC low-ß quadrupoles. In preparation for model construction, we report on improvements of the coil design and a study of the retaining structures. Jongeleen, S Leroy, D Siemko, A Wolf, R 10.1109/77.614458 1996 1996 Quench development is studied for the first few milliseconds after the start of a quench with the help of voltage taps and pickup coils in the LHC accelerator dipole models. The reliability of the pickup coil method (the so called quench antenna) is discussed. By studying the flux through the pick-up coils as a function of time, information about the current redistribution after the quench in the magnet cable is obtained. Several possible current redistribution models are studied: current transfer between the two layers of the cable, adjacent strand current transfer and redistribution governed by magnetoresistance, strand and interstrand resistance. Comparison of the simulations with the measurements in the magnets shows that the magnetoresistance of the copper in the cable matrix is the main mechanism responsible for current redistribution just after a quench. Bottura, L Walckiers, L Wolf, R IEEE Trans. Appl. Supercond. 10.1109/77.614576 602-605 7 1997 1996 The magnetic field in accelerator magnets decays when the current is kept constant during the particles injection phase, and returns quickly (snaps back) to the original values as soon as ramping is restarted. Here we show results of measurements of the decay of the field errors in 10 m long LHC model dipole magnets. In accordance with previous findings, precycles and stops at intermediate current levels influence the decay. We discuss a possible mechanism causing the decay and snap-back, based on the internal field change in the cable. Bottura, L Walckiers, L Ang, Z 10.1109/77.614624 1996 1996 The field quality of 10 m long LHC dipole models has been measured with short rotating coils to explore its dependence on time and position. Multipoles exhibit a longitudinal periodic variation, with period equal to the twist pitch length. This periodicity is shown here to have at least two components with very different time constants. The amplitude of the component with the shorter time constant, in the range of 100 to 300 s, depends on position and time. Larger amplitudes are measured at early times after a ramp and close to regions with incomplete cable transposition with respect to the non-uniform external field change. As the multipoles periodicity is due to current imbalance in the cables, we attribute the short time scale variations to the presence of space and time decaying boundary induced coupling currents (BICC's) in the cable. An estimate of their value is given