Electromagnetic Design of Superconducting Quadrupoles

We study how the critical gradient depends on the coil lay-out in a superconducting quadrupole for particle accelerators. We show that the results relative to a simple sector coil are well representative of the coil lay-outs that have been used to build several quadrupoles in the past 30 years. Using a semi-analytical approach we derive a formula that gives that critical gradient as a function of the coil cross-sectional area, of the magnet aperture, and of the superconducting cable parameters. This formula is used to evaluate the efficiency of several types of coil lay-outs (shell, racetrack, block, open mid-plane)

An Estimate of Multipolar Errors in the LHC Dipoles

Magnetic measurements of 60 collared coils and of 14 cryomagnets are available for the LHC dipoles. These data are used to work out an estimate of the systematic and random components of the field harmonics, in the hypothesis of a complete mixing of the manufacturers

A Solution for Phase-one Upgrade of the LHC Low-beta Quadrupoles Based on Nb-Ti

We discuss the possibilities of upgrading the LHC triplet quadrupoles by significantly increasing their aperture (and length), using the Nb-Ti cable of the main dipoles. The goal of this first phase in upgrading the triplet is to allow a rapid improvement of the luminosity mostly by removing limitations related to the triplet aperture. Neither the experimental area, including the TAS, nor the basic optics are modified. By the same token, steps are made to allow a moderate increase of the luminosity within the capabilities of the existing detectors. The triplet aperture is sized to decrease the collimator impedance below significance, allow a potential increase of the luminosity by some 50% or up to a factor of 2 with an external ancillary system acting on the geometrical loss factor. Some extra aperture is foreseen to lower the power deposition, to improve field quality and/or to allow a stronger focusing in the event some baseline beam parameters would not be reached. In this way, the proposed phase-one upgrade is versatile and should allow improved performance in a large range of situations

Pharmacological manipulation of L-carnitine transport into L6 cells with stable overexpression of human OCTN2

Abstract.: The high-affinity Na+-dependent carnitine transporter OCTN2 (SLC22A5) has a high renal expression and reabsorbs most filtered carnitine. To gain more insight into substrate specificity of OCTN2, we overexpressed hOCTN2 in L6 cells and characterized the structural requirements of substances acting as human OCTN2 (hOCTN2) inhibitors. A 1905-bp fragment containing the hOCTN2 complete coding sequence was introduced into the pWpiresGFP vector, and L6 cells were stably transduced using a lentiviral system. The transduced L6 cells revealed increased expression of hOCTN2 on the mRNA, protein and functional levels. Structural requirements for hOCTN2 inhibition were predicted in silico and investigated in vitro. Essential structural requirements for OCTN2 inhibition include a constantly positively charged nitrogen atom and a carboxyl, nitrile or ester group connected by a 2-4-atom linker. Our cell system is suitable for studying in vitro interactions with OCTN2, which can subsequently be investigated in viv

A Method to Measure Thermal Deformation of Superconducting Magnet Cross Sections

The precision measurement of the cable positioning in superconducting coils is of great interest both at room and liquid nitrogen temperatures because mechanical and thermal deformations affect the quality of the magnetic field. The paper describes a new two-coordinate measuring device, which is able to obtain scanned images of flat composite samples at liquid nitrogen temperature. The sample is cooled at 77 K into a flat quartz tray to permit the optical access to the sample from the bottom. The comparison of the images taken at room and liquid nitrogen temperatures by a high-resolution flatbed scanner gives the thermal contraction of the components

Status Report on Field Quality in the Main LHC Dipoles

We give the present status of the field quality in the main LHC dipoles. Special emphasis is given to the collared coil data: a few tens of coils have been built, allowing a first analysis of the variability between producers, and estimates of the random part. Effects of the corrective actions implemented to fine tune the systematics components of low-order multipoles are presented. Correlations of collared coil data to the magnetic field measurements in operational conditions are discussed. Comparison to specifications imposed by beam dynamics allows to pin out the most critical requirements that will have to be met during the LHC dipole production

Impact of the First Powering Cycles on the LHC Superconducting Dipole Coil Geometry

The impact of the first powering cycles on the LHC superconducting dipoles coil geometry has been investigated. Dedicated magnetic measurements have been performed to estimate the changes in the geometric component of the harmonics, caused by the last highest Lorentz force the coil has ever experienced. Several magnets have been powered at increasing current steps while the field quality has been measured to quantify the changes in geometry. The effect of the thermal cycles has been also considered as well as the systematic differences between measurements before and after the quench training. The reconstruction of the coil geometry variations is discussed in terms of continuous modes of deformation as well as single block displacements

Optimization of the Even Normal Multipole Components in the Main Dipole of the Large Hadron Collider

In this paper we discuss even multipolar components of the Large Hadron Collider dipole in relation to the manufacturing features and target values required by beam dynamics. Due to the two-in-one collar geometry, systematic components are induced by the mutual influence of the two apertures and are strongly affected by the shape of the magnetic iron yoke. In order to optimize the normal quadrupole and octupole harmonics, a new design was chosen for the ferromagnetic insert between the iron yoke and the collars. Three different insert shapes were selected and installed in a full scale prototype. The measured dependence of the even multipoles on the insert shape shows a good agreement with simulations based on a magnetostatic code. A final design of the insert has been worked out and implemented in pre-series magnets. Data relative to even multipoles in pre-series magnets are presented, both at room temperature and at the operational temperature of 1.9 K. Comparison with target values required by beam dynamics is discussed

Steering the Field Quality in the Production of the Main Quadrupoles of the Large Hadron Collider

The main issues concerning the field quality in the main quadrupoles of the Large Hadron Collider are presented. We show the trend plots for the focusing strength and multipoles at room temperature covering more than 2/3 of the production. We describe the correction of the coil layout to improve b6 at injection field level. A non-negligible fraction of the quadrupoles has been manufactured with collars featuring a magnetic permeability somewhat higher than the specified limits. We show plots for this anomaly. Field quality correlations to measurements in operational conditions are discussed. The dependence of field quality on cable manufacturer is analyse

Field quality of the LHC dipole magnets in operating conditions

We report here the main results of the field measurements performed so far on the pre-series LHC superconducting dipoles at superfluid helium temperature. After discussing the results at injection and collision conditions, we focus on the non-linear contributions at high field, on the contribution of superconductor magnetization at injection, and on ramp rate effects. The statistics accumulated on the first magnets of the production verify the hypotheses that have been used to design the correctors scheme for the LHC. In particular high field saturation is in line with the expectations, although a small systematic deformation due to Lorentz forces affects both sextupole and decapole terms. The decay at injection and snap-back at beginning of beam acceleration require careful characterization