Aperture Quadrupole Research Articles

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Correction to: Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Correction to: Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Nonlinear field effects in the collector ring due to large-amplitude particle oscillations

In the frame of the FAIR project, the Collector Ring (CR) is planned to be built for efficient cooling of antiprotons and rare isotope beams [1]. In order to accept hot beam from separators large acceptances are required. This paper examines the effects which can influence the beam dynamics due to large betatron oscillation amplitude and momentum spread. Using analytic expressions, the amplitude-dependent tune shifts driven by sextupole magnets, the fringe field of quadrupole magnets, and kinematics effects have been calculated. The obtained results have been compared with numerical simulations by means of precise multi-turn particle tracing. The tracking analysis for the CR has been performed considering the real shape of the magnetic field of the wide aperture quadrupole. We report on quantitative studies of the effects on the dynamic aperture of the rings.

Test Results of the MQYYM: A 90 Mm NbTi Quadrupole Magnet Option for HL-LHC

For the HL-LHC project, a 90 mm NbTi cos(2θ) double aperture quadrupole magnet with an operating gradient of 120 T/m at 1.9 K has been designed as an option to replace the 70 mm aperture LHC quadrupole MQY. CEA in collaboration with CERN designed and manufactured a single aperture short model magnet with a magnetic length of 1.215 m at 1.9 K called MQYYM. The MQYYM cold test occurred at CEA at 4.2 K in a vertical cryogenic station. During the power test, the operating gradient at 1.9 K has been reached after two training quenches. All along the test, magnetic and mechanical measurements were done using respectively a rotating probe and strain gauges. This paper describes the performance of the MQYYM at 4.2 K and gives an analysis of the data acquired during the test, including training behavior, quench detection, protection and field quality measurements.

Development of the CEPC collider prototype magnets

A Circular Electron Positron Collider (CEPC) with a circumference of about 100 km and a beam energy up to 120 GeV is proposed to be constructed in China. Over 80% of the collider ring is covered by conventional magnets. Most dipole and quadrupole magnets are twin aperture magnets with an inter-beam separation of 350 mm. Two 1-meter-long twin aperture prototype magnets are designed and manufactured. One is a combined dipole–sextupole magnet with aluminum bus bar coils, and the other one is a twin aperture quadrupole magnet with a DT4 compensation sheet to reduce the crosstalk effect between the two apertures. The design, fabrication and magnetic measurement of two prototype magnets are described in this paper.

Development of a high precision small aperture quadrupole magnet with copper plate coils

Using the conventional coil manufacturing method, the iron core of a small aperture quadrupole magnet needs to be divided into four or more segments to install the excitation coils, which brings assembly errors and generates high-order magnetic field harmonics. In this paper, the development of a high-precision small-aperture quadrupole magnet named HQ22 using copper plate coils is described. The magnet has a bore aperture of 22 mm, a gradient of 90 T/m, and an effective length of 0.36 m. Its coil is mainly composed of a number of U-shaped copper plates, electrical connection sheets, and insulating sheets, which are directly assembled and connected on the pole. Outside the coil, water box with cooling water channel inside is installed to provide indirect cooling to the coil. Using copper plate coil, one-piece or two-piece structure can be adopted for the iron core, so the assembly error is reduced and magnetic field quality can be improved. The research provides an attractive technical scheme for small aperture quadrupole magnets in future light sources. The detailed magnet design, magnetic field calculation and measurement results of HQ22 are presented, and the application prospect of copper plate coil is discussed.

Magnetic Measurements at Warm of the First FCC-ee Final Focus Quadrupole Prototype

The first FCC-ee final focus quadrupole prototype has been designed, manufactured, assembled and tested at warm. The prototype is a single aperture quadrupole magnet of the CCT type. One edge of the magnet was designed with local multipole cancellation, whereas the other was left with the conventional design. An optimized rotating induction-coil sensor was used. A technique was developed to take into account field distortions due to the environment of the test and distinguish them from magnet effects, demonstrating an excellent field quality for the prototype.

3D Mechanical Analysis of a Compact ${\text{Nb}}_{\text{3}}{\text{Sn}}$ IR Quadrupole for EIC

The Electron Ion Collider (EIC) will require large aperture quadrupole magnets for the Hadron beam in the insertion region. Key requirements include high field, compact size, and tight control of the fringe fields. A 120 mm aperture, 308.4 mm outer diameter actively shielded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm {Nb}}_{3}{\rm {Sn}}$</tex-math></inline-formula> quadrupole model is under development to support these goals. This work is being carried out by a collaboration of BNL, JLAB and LBNL. A compact shell-based structure preloaded with a bladder and key system was developed for this project. In this paper, the effect of the compact structure on the mechanical behavior was investigated. In particular, the impact of the assembly tolerances and coil size variations on the actual coil stresses and bladder pressures was computed and compared with results from larger bladder and key structures developed for the LHC IR. The longitudinal preload is provided by stainless steel rods. Differently from other bladder and key magnets, the rods are first preloaded axially before coil axial load is applied. This new design aims to increase the overall stiffness of the system and reduce the longitudinal coil displacement during powering. Based on the results of a 3D mechanical analysis, the preliminary pre-load targets for the EIC quadrupole assembly will be reviewed and discussed.

Assembly and Warm Magnetic Measurement of MQYYM: A 90 mm NbTi Quadrupole Magnet Option for HL-LHC

In the framework of the HL-LHC project, a NbTi double aperture quadrupole magnet MQYY is being developed as an option to replace the LHC magnet MQY. This 90 mm double aperture cos-2θ quadrupole has an operating gradient of 120 T/m at 1.9 K. To demonstrate the validity of the design, a single aperture short model of 1.2 m called MQYYM has been developed. Designed by CEA and manufactured in collaboration with CERN, the MQYYM magnet is being prepared for cold test at CEA in a dedicated cryogenic station with LHe bath at 1 bar 4.2 K and 23 mbar 1.9 K. First, this paper will summarize the initial and as-built magnet designs based on the assembly at CERN. Second, updated mechanical measurements of collaring and axial pre-loading will be presented. Finally warm magnetic measurements performed at CERN during the assembly and at CEA during test preparation will be detailed.

Design of a Tapered Final Focusing Magnet for eRHIC

Presently, the electron-ion collider electron relativistic heavy ion collider (eRHIC) is under design. It aims to provide a facility with a peak luminosity of 10 34 cm -2 sec -1 . In terms of magnet design, the IR magnets are particularly challenging due to the close proximity of the electron and hadron beams. This paper outlines the design for the so-called Q1 rear side magnet, which is a double aperture quadrupole magnet, 7.2 m from the interaction region. Due to space restrictions, both magnets are housed in the same iron yoke. The aperture of the hadron quadrupole is relatively small, but requires high gradients. While the required gradient for the electron quadrupole is relatively small, the aperture of this magnet needs to accommodate the beam and allow the synchrotron radiation fan to pass through. To accomplish this, both quadrupole magnets have a tapered aperture. To keep the gradients constant along the length of the magnets, a special winding pattern has been identified, which is described in this paper.

Progress on HL-LHC Nb3Sn Magnets

The high-luminosity Large Hadron Collider (HL-LHC) project aims at allowing to increase the collisions in the LHC by a factor of ten in the decade 2025-2035. One essential element is the superconducting magnet around the interaction region points, where the large aperture magnets will be installed to allow to further reduce the beam size in the interaction point. The core of this upgrade is the Nb3Sn triplet, made up of 150-mm aperture quadrupoles in the range of 7-8 m. The project is being shared between the European Organization for Nuclear Research and the US Accelerator Upgrade Program, based on the same design, and on the two strand technologies. The project is ending the short model phase, and entering the prototype construction. We will report on the main results of the short model program, including the quench performance and field quality. A second important element is the 11 T dipole that replaces a standard dipole making space for additional collimators. The magnet is also ending the model development and entering the prototype phase. A critical point in the design of this magnet is the large current density, allowing increase of the field from 8 to 11 T with the same coil cross section as in the LHC dipoles. This is also the first two-in-one Nb3Sn magnet developed so far. We will report the main results on the test and the critical aspects.

Summary of Test Results of MQXFS1—The First Short Model 150 mm Aperture Nb3Sn Quadrupole for the High-Luminosity LHC Upgrade

The development of Nb3Sn quadrupole magnets for the High-Luminosity LHC upgrade is a joint venture between the US LHC Accelerator Research Program (LARP)* and CERN with the goal of fabricating large aperture quadrupoles for the LHC interaction regions (IR). The inner triplet (low-β) NbTi quadrupoles in the IR will be replaced by the stronger Nb3Sn magnets boosting the LHC program of having 10-fold increase in integrated luminosity after the foreseen upgrades. Previously, LARP conducted successful tests of short and long models with up to 120 mm aperture. The first short 150 mm aperture quadrupole model MQXFS1 was assembled with coils fabricated by both CERN and LARP. The magnet demonstrated a strong performance at Fermilab's vertical magnet test facility reaching the LHC operating limits. This paper reports the latest results from MQXFS1 tests with changed prestress levels. The overall magnet performance, including quench training and memory, ramp rate, and temperature dependence, is also summarized.

Development of MQYY: A 90-mm NbTi Double Aperture Quadrupole Magnet for HL-LHC

In the context of the HL-LHC project, a NbTi double aperture quadrupole magnet called MQYY is being developed. This 90-mm-aperture quadrupole magnet has a magnetic length of 3.67 m and an operating gradient of 120 T/m at 1.9 K. Its development is done along two parallel paths: 1) the design, fabrication, and test of a short model; 2) the design and fabrication of two full-scale prototypes in industry within the H2020 EU Pre-Commercial Procurement project QUACO implemented by CERN, CEA, CIEMAT, and NCBJ. We report here on the short-model design choices the status of its fabrication and the preparation of the tests. In particular, we describe the magnetic and mechanical design relying on self-supporting collars, the protection aspects, the fabrication, and the cold test preparation. Finally, we present the unusual scheme of the QUACO project leading to the prototypes fabrication.

Coil End Parts Development Using BEND and Design for MQXF by LARP

End parts are critical components for saddle-shaped coils. They have a structural function where the cables are deformed in order to cross over the magnet aperture. Based on the previous design of the US LARP program for 90-mm aperture quadrupoles (TQ/LQ) and 120 mm aperture quadrupoles (HQ/LHQ) using BEND, the coil ends of the low-β quadruples (MQXF) for the HiLumi LHC upgrade were developed. This paper shows the design of the MQXF coil ends, the analysis of the coil ends during the coil fabrication, the autopsy analysis of the coil ends, and the feedback to BEND parameters.

The pseudopotential for quadrupole fields up to q = 0.9080

Pseudopotential models for radio frequency (rf) electric fields are widely used. However, these approximate and sometimes intuitively introduced methods, can sometimes lead to ambiguities and false conclusions. While a classical model works well for quadrupole fields with small q where the Mathieu parameter β≤0.4 there has been some discussion in the literature of the behavior of a pseudopotential, and, in particular, the secular frequency of ions for larger q near the far end of the stability zone (for example, near qmax≈0.908045 for a=0). This paper analyzes carefully the behavior of secular frequencies calculated both numerically and analytically and demonstrates that the classical formula for the secular frequency in the pseudopotential, ω=βΩ/2remains valid up to β=1. This means that both the secular frequency and the pseudopotential function well depth increase monotonically with q inside the stability zone. However, some models state that the well depth, identified as the pseudopotential function calculated at the edge of a quadrupole aperture, should be zero at both the low q and high q boundaries of the stability zone, with a maximum somewhere between. It is shown that the paradox that the acceptance is zero at both ends of the stability zone and hence the pseudopotential well depth and the pseudopotential quadratic coefficient should be zero at both boundaries of the stability zone is resolved by introducing for large q a pseudopotential well depth and a pseudopotential well width as separate pseudopotential objects to characterize the acceptance, while a quadratic pseudopotential function is used to describe the secular motion of ions but not the acceptance for large q.

Magnetic fringe field interference between the quadrupole and corrector magnets in the CSNS/RCS

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) employs large aperture quadrupole and corrector magnets with small aspect ratios and relatively short iron to iron separations; so the fringe field interference becomes serious which results in integral field strength reduction and extra field harmonics. We have performed 3D magnetic field simulations to investigate the magnetic field interference in the magnet assemblies and made some adjustments on the magnet arrangement. The Fourier analysis is used to quantify the integral gradient reduction and field harmonic changes of the quadrupole magnets. Some magnetic field measurements are undertaken to verify the simulation results. The simulation details and the major results are presented in this paper.

A Nb-Ti 90 mm Double-Aperture Quadrupole for the High Luminosity LHC Upgrade

The luminosity upgrade of the LHC requires replacing the magnets around the ATLAS and CMS experiments with larger aperture dipoles, quadrupoles and correctors. The goal is to have a magnetic lattice that can allow to halve the beam size in the collision points with respect to present baseline. Within the framework of HiLumi LHC, CEA-Saclay studied the replacement of the 70-mm double aperture quadrupole Q4, with a 90-mm magnet based on Nb-Ti technology. The main challenges are due to the distance between the beams of 194 mm, giving a non-negligible magnetic coupling between the two apertures. The coil chosen to be the baseline is a single layer with 15-mm-width cable of the LHC MQ quadrupole. The mechanical structure is based on stainless steel collars to withstand the Lorentz forces. The iron yoke has a magnetic function, and guarantees the alignment of the two apertures. Electromagnetic and mechanical aspects and effects of unbalanced regimes on the field quality have been analyzed. A 3-D design of the coil ends is obtained by minimizing both the integrated multipoles and the peak field.

Nb3Sn High Field Magnets for the High Luminosity LHC Upgrade Project

The high luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11-T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11-T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb 3 Sn conductor and are the first applications of this superconductor to actual accelerator magnets. Collaboration between the US LARP (LHC Accelerator Research Program) and CERN is developing the MQXF magnets, whereas the 11-T dipole magnets are being developed by CERN and Fermilab. This paper reviews the status of Nb 3 Sn technology for accelerator magnets, discusses its main challenges, and discusses how the MQXF and 11-T designs are addressing them.

Numerical Simulation of Microchannel Deformation in Enhanced Insulation for Nb–Ti Superconducting Accelerator Magnets

A new insulation scheme for the Nb-Ti superconducting magnets to better extract heat from the coil was proposed in 2007, and several experiments were done to validate this novel concept, including the construction of a large aperture quadrupole. An essential parameter of this scheme is the size of the microchannels provided by a new topology of the insulation wrapping, allowing a direct helium path from the helium bath to the strands. The main question is whether these channels are still open under the large pressures induced during assembly and by electromagnetic forces. In this paper, one shows that a thermal model of the insulation scheme can be used to interpret the experimental data. The model suggests that the microchannels are significantly reduced with respect to their nominal values but are still well open. To validate this result, a finite-element model of the insulation and strands under pressure is done, and the behavior of this complex topology is estimated. The mechanical model confirms that the microchannels are open even under pressures of 100 MPa, with a cross-sectional reduction on the order of 50%. A parametric analysis of the microchannel deformation versus pressure is carried out, showing a good agreement with the experiments.

Design and Magnetic Performance of Small Aperture Prototype Quadrupoles for the SwissFEL at the Paul Scherrer Institut

The Paul Scherrer Institut is building an X-ray free electron laser (SwissFEL) providing a source of intense, ultra-short pulses of coherent radiation in the wavelength range of 0.1 to 0.7 nm. In this facility, there will be 162 small aperture quadrupoles of two types (22- and 12-mm aperture), which both include horizontal and vertical steering functions, under preparation for the linac and the undulator line. Before the series production, eight full-scale prototypes of the final design were built in collaboration between Industry and the Paul Scherrer Institut. This paper describes the features of the quadrupole design and the measurement challenges and reports the main results obtained during the magnetic measurements. The integrated field gradient, the field profile, the harmonic content, and the magnetic axis are measured using four independent systems well suited for small bore apertures: an 8 mm and a 19-mm diameter rotating coil, a Hall probe, and a vibrating wire system. The results of the integrated transfer function and of the field quality are given and discussed.