Magnet Design of the 150 mm Aperture Low-β Quadrupoles for the High Luminosity LHC

• Paolo Ferracin (CERN)

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: The High Luminosity LHC (HL-LHC) project is aimed at studying and implementing the necessary changes in the LHC to increase its luminosity by a factor five. Among the magnets that will be upgraded are the 16 superconducting low-β quadrupoles placed around the two high luminosity interaction regions (ATLAS and CMS experiments). In the current baseline scenario, these quadrupole magnets will have to generate a gradient of 140 T/m in a coil aperture of 150 mm. The resulting conductor peak field of more than 12 T will require the use of Nb3Sn superconducting coils. We present in this paper the HL-LHC low-β quadrupole design, based on the experience gathered by the US LARP program, and, in particular, we describe the support structure components conceived to pre-load the coils, withstand the electro-magnetic forces, provide alignment and LHe containment, and integrate the cold mass in the interaction regions of the LHC.

Fast Cycled Magnet demonstrator program at CERN: test station, instrumentation and measurement campaign

• Gerard Willering (CERN)

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: In an effort to develop economical magnets for an upgrade of the LHC injector complex, CERN started an R&D program on superconducting Fast Cycled Magnets (FCM) in 2009. One of the challenges in this program was to develop a test station, which started working in summer 2012 when the FCM dipole demonstrator was tested. The magnet contains several new features, like forced-flow cooling of supercritical He and it has a novel protection scheme. In this paper we report on the cryogenic and powering requirements and operation, the quench protection system, the temperature and mechanical measurements. The functioning of the test station and instrumentation are evaluated and we will discuss the measurements on a detailed level.

Critical Current measurements of High-Jc Nb3Sn Rutherford cables under Transverse Pressure

• Bernardo Bordini (CERN)

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: For the LHC upgrade, CERN has launched a large program to develop the next generation accelerator magnets based on high-Jc Nb3Sn Rutherford cables. These magnets are characterized by a magnetic field and/or an aperture significantly larger than that of current Nb-Ti LHC magnets. The increased field/aperture will require coil pre-stresses much larger than 100 MPa. Since Nb3Sn cables are extremely sensitive to strain, critical current measurements under traverse pressure are essential to estimate the transport current properties of the conductor within the magnet. For this purpose CERN has developed a sample holder (to be used in the FRESCA test station) that allows testing Rutherford cables under a transverse force up to 2 MN/m. The new holder can house cable samples up to 1.8 m long and 20 mm wide. The large transverse force is only applied over the sample high field region, which is 60 cm long and over which the FRESCA dipole magnet applies a homogeneous field up to 10 T. Recently the critical current of the first cable sample has been measured at different transversal pressure ranging from 80 MPa to 170 MPa. The measurement was carried out at 4.3 K on a 10 mm wide Rutherford cable based on eighteen Powder In Tube (PIT) wires with a diameter of 1.0 mm. In this paper the results are reported, discussed and compared with recently published data of the same type of single wire tested under transverse pressure.

Quadrupole Electro-magnets for Linac4 at CERN

• Liesbeth Vanherpe (CERN)

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: Linac4 is the first element of the LHC Injectors Upgrade Project and will replace the existing Linac2 as linear injector of protons for the CERN accelerators. A new transfer line will link Linac4 to the Proton Synchrotron Booster (PSB). Approximately hundred electro-magnets are required for beam steering and focusing along the linac and the transfer line. We present an overview of the new Linac4 electro-magnets, and concentrate on the design and manufacturing of the quadrupole magnets and their current status. In particular, we highlight the design and optimization of the transfer line quadrupole magnets. We show how the compatibility of a set of design requirements for a quadrupole magnet with a given pulsed power converter can be judged based on the stored magnetic energy, which in turn depends on the magnetic length and the aperture. We combine existing analytical relations to describe these dependencies and confirm them after comparison with a set of two-dimensional magnet designs. With this result, we develop a visual tool to assess the compatibility between a set of design requirements and the operation range of a pulsed power converter. We demonstrate the value of this tool, and conclude with the final design and layout of the transfer line quadrupole magnets.

LHC IR Upgrade Nb-Ti, 120mm Aperture Model Quadrupole Test Results at 1.8K

• Glyn Kirby (CERN)

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: Over the last five years, the model MQXC Quadruple; a 120 mm aperture, 120 T/m, 1.8 m long, Nb-Ti version of the LHC insertion upgrade (due in 2021), has been developed at CERN. The magnet incorporates several novel concepts to extract high levels of heat flux and provide high quality field harmonics throughout the full operating current range. Existing LHC-dipole cable with new, open cable and ground insulation was used. Two, nominally identical 1.8 m long magnets were built and tested at 1.8 K at the CERN SM18 test facility. This paper compares in detail the two magnet tests and presents: magnetic field measurements, quench performance, internal stresses, heat extraction simulating radiation loading in the superconducting coils, and quench protection measurements. The first set of tests highlighted the conflict between high magnet cooling capability and quench protection. The second magnet had additional instrumentation to investigate further this phenomenon. Finally we present test results from a new novel type of superconducting magnet protection system.

Deduction of Steady-State Cable Quench Limits for Various Electrical Insulation Schemes with Application to

• Pier Paolo Granieri (Ecole Polytechnique Federale de Lausanne (EPFL))

Room: 30/7-018 - Kjell Johnsen Auditorium Abstract: Undesired quenches of superconducting magnets can be a limiting factor for the operation of the LHC accelerator, both for its forthcoming exploitation at full energy as well as for its future upgrades. An accurate knowledge of the quench limit, the maximum amount of heat deposit the magnets can withstand, is required to be able to prevent beam induced quenches. In this paper we provide an overview of the heat extraction through the multitude of cable insulation schemes used in particle accelerators in the past 20 years and foreseen for the coming years. Based on the relevant heat transfer measurements, we deduce steady-state cable quench limits both for the LHC Nb-Ti magnets and for the future HL-LHC Nb3Sn ones. We provide them for different operating conditions and different locations within the coil.