Peter Galbraith

Testing Results for Nb-Ti, 120-mm-Aperture, Low-B Quadrupole Models for the LHC High-Luminosity Insertion

The design and construction of a 120-mm wide-aperture, Nb-Ti superconducting quadrupole magnet for the Large Hadron Collider (LHC) insertion region is part of a study towards a luminosity upgrade of the LHC at CERN, envisaged for 2020-22. The main challenges for this accelerator quality magnet are to operate reliably with the high heat and radiation loads that are predicted in the insertion magnet regions. Calculations give approximately 500 Watts over the 30-m-long string of insertion magnets, while today LHC is operating for a nominal heat load of 12 Watts. To extract this heat, the model magnets incorporate new features: Open cable insulation, open ground insulation, open magnet structure, and a quench heater that has open channels to help extract the steady state heat load. This paper presents results from tests at room temperature and 1.8 K for the initial model magnet. We report magnet training, transfer function and field quality measurements, quench heater performance, and heat extraction studies using imbedded heaters to simulate the deposited beam heating profile.

A Device to Measure Magnetic and Mechanical Axis of Superconducting Magnets for the Large Hadron Collider at CERN

The LHC will be composed of 1232 horizontally curved, 15 meter long, cryodipoles and 474 short straight sections, being assembled by different manufacturers. Magnetic axis alignment is an essential part of the magnets quality for two reasons: first, to be able to install correctly the magnets in the tunnel w.r.t. the reference beam orbit; secondly, to assess the relative alignment between the magnets composing the assembly, i.e. spool pieces for the dipoles and larger correctors for the SSS. A system called AC mole is being used extensively to measure magnetic and geometric axis, as well as roll angle, for every single magnet composing all the SSS. This paper describes its performance, its first years of operation, as well as the improvements that have made it very powerful, versatile and easy to use

A Hall Plate Based Instrument to Measure the Snapback in the Large Hadron Collider Superconducting Dipole Magnets

The decay and snapback of the magnetic field multipoles in superconducting particle accelerators like the Large Hadron Collider (LHC) could result in a significant particle beam loss unless adequately compensated. Whilst standard instrumentation used to measure the field quality of the superconducting magnets is good enough to measure the harmonic decay, it is not fast enough to measure the snapback. Therefore, a state of the art instrument was recently developed at CERN to measure the most important harmonics with a high measurement frequency and hence improve the understanding of the snapback phenomenon. In this paper we describe the instruments principle of operation, its mechanical arrangement, its compensation system and its digital acquisition system. We also compare the performance of two different techniques implemented to achieve the necessary measurement resolution of 6 orders of magnitude lower than the main superimposed dipole field

Models and experimental results from the wide aperture Nb-Ti magnets for the LHC upgrade

MQXC is a Nb-Ti quadrupole designed to meet the accelerator quality requirements needed for the phase-1 LHC upgrade, now superseded by the high luminosity upgrade foreseen in 2021. The 2-m-long model magnet was tested at room temperature and 1.9 K. The technology developed for this magnet is relevant for other magnets currently under development for the high-luminosity upgrade, namely D1 (at KEK) and the large aperture twin quadrupole Q4 (at CEA). In this paper we present MQXC test results, some of the specialized heat extraction features, spot heaters, temperature sensor mounting and voltage tap development for the special open cable insulation. We look at some problem solving with noisy signals, give an overview of electrical testing, look at how we calculate the coil resistance during at quench and show that the heaters are not working We describe the quench signals and its timing, the development of the quench heaters and give an explanation of an Excel quench calculation and its comparison including the good agreement with the MQXC test results. We propose an improvement to the magnet circuit design to reduce voltage to ground values by factor 2. The program is then used to predict quench Hot-Spot and Voltages values for the D1 dipole and the Q4 quadrupole.

Design and Implementation of an Automated Polarity Checker for Superconducting Magnets

In this paper a new measurement system for the polarity check of all the superconducting magnets that will compose the Large Hadron Collider (LHC) is described. The polarity checker is a scanning probe that, thanks to a rotating Hall plate, performs a complete local analysis of the magnet under test. By Fourier analysis of the radial component of the magnetic field picked up by the Hall sensor, the instrument identifies the magnet order and type, the field polarity, and provides the transfer function of the main harmonic and an estimation of the magnetic field angle. After the description of the measurement principle, the hardware and the software of the instrument are detailed. Particular attention is devoted to the metrological characterization and the correction of deterministic errors in order to ensure a polarity measurement practically error free on all the magnet types