Superconducting Quadrupole Magnets Research Articles

Power supplies of unbalance currents in focusing and defocusing structural superconducting quadrupole magnets of a nuclotron

The specifications and schemes of the main components of the power supplies of the unbalance currents of focusing and defocusing magnets with a series feeding scheme of a nuclotron are presented and the devices are described. The devices were made on the basis of thyristor rectifiers. High operating speed, small ripples, and low noise of the output current are achieved through the use of transistor blocks for the current regulation in a linear mode. The special feature of the described power supplies is the operation of the thyristor rectifiers in the so-called tracking mode that allows to minimise the power losses on the pass transistor bank and to regenerate the energy stored in the inductive elements to the AC network. An additional feedback loop is applied for precision current regulation.

Experimental study on heat transfer through a few layers of multilayer insulation from 300 K to 4.2 K

The final focusing magnet system at the SuperKEKB interaction region has been designed under stringent space constraints and consists of 8 main Superconducting (SC) quadrupole magnets, 4 compensation SC solenoids, and 43 SC correction coils. SC correction coils are directly wound on the inner containment tubes of liquid helium (LHe) vessels, which serve as support bobbins for SC cables. Beam pipes, which are kept at room temperature (∼300 K), are inserted into the cold bores of the vessel inner tubes. Between them, the minimal radial gaps are only 3.5 mm. Heat transfer from the warm beam pipes causes the raised operation temperatures of SC cables and increases heat leaks into cryostats. Multilayer insulation (MLI) is adopted to reduce heat flux in the narrow gaps. MLI performance as a function of the layer number was studied with a vertical anti-cryostat of dedicated design. The measurements were carried out by a calorimeter of thermal conduction and a modified LHe boil-off method. This paper presents the cryogenic measurement system and discusses the experimental results for the cryostats of the SuperKEKB final focusing SC magnets.

Simulation optimization on quench analysis of wide aperture superconducting quadrupole magnet

Wide aperture superconducting magnets are used in different accelerator laboratories as spectrometer magnets. These magnets are used in the accelerator facilities like ANURIB project, Kolkata, newly constructed BIGRips facility in Japan and FAIR project in GSI, Germany. Quench simulation is an important part of the design of superconducting magnet. The present simulation has been carried out using QUENCH code and QUENCH-ELECTRA coupled code of Vector Fields software for wide aperture superconducting quadrupole magnet. Since the quench calculation is highly nonlinear in nature, Computation time is generally high. As increased computation time increases cost of design, choosing proper mesh size and time stepping tolerances play an important role during quench calculation. This paper will discuss about convergence of hot spot temperature and maximum voltage on mesh size, tolerance criteria. Computation time for each case, effect of delay in actuation of quench circuit will also be discussed.

Analysis of Temperature Uniformity During Heat Treatment of Nb3Sn Coils for the High-Luminosity LHC Superconducting Magnets

The High-Luminosity upgrade of the Large Hadron Collider at CERN comprises the implementation of a new generation of high-field superconducting quadrupole and dipole magnets. The dipole fields of up to 12.1 T at nominal current require the use of high-critical-current Nb3Sn strand for the fabrication of the coils. These coils will be up to 8 m long and represent the longest Nb3Sn coils so far fabricated for operation accelerator magnets. This brittle A15 phase material requires coil winding prior formation of the superconducting material. The development program at CERN includes the construction of 2-m-long models and full-length prototypes by the wind-and-react technique. The process time and temperature uniformity are stringent during heat treatment and performed inside an EN 1.4841 (AISI Type 314) stainless-steel retort furnace with turbulent flow of Ar atmosphere. During the process, the coil is supported inside a reaction fixture made from 316LN. This paper presents temperature uniformity measurements and results from numerical simulations. The goal is to further improve the heat transfer in combination with turbulent flow generated by a ventilation system. This allows optimizing control parameters for improved heat performance during both the ramping and the dwell time.

JLAB's Super High Momentum Spectrometer's Superconducting Q1 Magnet

The commissioning and test results of a superferric superconducting quadrupole magnet constructed by Scientific Magnetics, Inc., for Thomas Jefferson National Accelerator Facility (TJNAF also known as JLAB) will be presented. The quadrupole magnet, named Q1, is the first focusing element in the Super High Momentum Spectrometer (SHMS). The SHMS, which is located within JLAB's experimental Hall C, consists of all superconducting magnets in a dQQQD configuration and is part of the JLAB's 12-GeV upgrade. Here, “d” refers to the small horizontal bend dipole, “Q” stands for focusing quadrupole magnets, and “D” is the vertical-bending momentum-selecting dipole magnet. Characterization of the magnet's cryogenic heat loads and magnetic field quality will be presented along with descriptions of the magnet's control system, power supply, and quench detection system.

Design of cryostat for superconducting quadrupole magnets in In-Flight fragmentation separator

Abstract The cryostat is designed for the superconducting quadrupole magnets to be used in a heavy-ion accelerator facility. The main accelerator is superconducting linac, which can accelerate a 238 U beam to 200 MeV/u (Mega electron voltage per nucleon). The cryostat for the magnet employs an innovative design primarily driven by the requirement of the compactness, user -friendliness and reliability. Also, several ancillary requirements such as background field, space restriction due to the beam line and cryostat structure need technical attentions. The development of the cryostat for three quadrupole magnets in the in-flight fragmentation separator is presented in the paper. The concept of cryogenic design is reported and the amount of cryogenic load is estimate d by a relevant analysis. The structure of the cryostat to endure the heavy iron yoke including three quadrupole magnets is presented. In addition, the design as well as the performance test of the support link for the cold mass is described.

Design and Construction of the SuperKEKB QC1 Final Focus Superconducting Magnets

The construction of SuperKEKB, which consists of 7 GeV electron and 4 GeV positron main rings, is now going on. The final focus superconducting quadrupole magnets in the interaction region have been designed and constructed. From the field qualities of the prototype magnets, the magnet designs were modified, and the manufacturing and assembling methods of the coils were changed to satisfy the design values. The field measurements of the magnets were performed at room temperature, and confirmed that they were acceptable for the beam operation. In the paper, the design and the construction of the final focus quadrupole magnets, QC1, which will be located at the closest position to the beam interaction point, are presented.

Magnetic and Thermal Performance of a Conduction-Cooled Splittable Quadrupole

A superconducting quadrupole magnet with splittable yoke has been designed for use in ILC Main Linac (ML) cryomodules. The splittable yoke allows assembly around the beam pipe, to avoid potential contamination of the superconducting RF cavities. The magnet is cooled by conduction and covers the full range of required ML field gradients. A critical requirement is stability of the magnetic center, at the level of 5 μm, for a 20% variation of the operating field. We report here the results of thermal, quench, and magnetic performance tests of a prototype splittable quadrupole, that were made up to the maximum design operating gradient in a conduction-cooled test cryostat.

Beam optical design of in-flight fragment separator for high-power heavy ion beam

An in-flight fragment separator has been designed for the rare isotope science project (RISP) in Korea. A beam used for the design is 238U in the energy of 200MeV/u with the maximum beam power of 400kW. The use of high-power beam requires careful removal of the primary beam by pre-separator, for which its configuration was revised to employ four dipole magnets instead of two. Different configurations of the separator have been tested in search of optimal design in non-linear optics, which was complicated by the space needed for the target, beam dump and radiation shielding. Non-linear optical calculations have been carried out using GICOSY and COSY Infinity including the fringe fields of large-aperture quadrupole magnets. Correction of non-linear terms is made with multipole coils located inside the superconducting quadrupole magnets and by external multipole magnets. Beam simulations using LISE++ and MOCADI have been performed to consider the effects of multiple charge states of the primary and isotope beams produced at the target. Layout of the separator is being finalized, and detailed optics simulation will continue to refine its design.

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.

Engineering Design and Manufacturing Challenges for a Wide-Aperture, Superconducting Quadrupole Magnet

The design and construction of a wide-aperture, superconducting quadrupole magnet for the LHC insertion region is part of a study towards a luminosity upgrade of the LHC at CERN. The engineering design of components and tooling, the procurement, and the construction work presented in this paper includes innovative features such as more porous cable insulation, a new collar structure allowing horizontal assembly with a hydraulic collaring press, tuning shims for the adjustment of field quality, a fishbone like structure for the ground-plane insulation, and an improved quench-heater design. Rapid prototyping of coil-end spacers and trial-coil winding led to improved shapes, thus avoiding the need to impregnate the ends with epoxy resin, which would block the circulation of helium. The magnet construction follows established procedures for the curing and assembly of the coils, in order to match the workflow established in CERN's “large magnet facility.” This requirement led to the design and procurement of a hydraulic press allowing for both a vertical and a horizontal position of the coil-collar pack, as well as a collapsible assembly mandrel, which guarantees the pack's four-fold symmetry during collaring. The assembly process has been validated with the construction of two short models, instrumented with strain gauges and capacitive pressure transducers. This also determines the final parameters for coil curing and shim sizes.

Mechanical Behavior of HQ01, a ${\hbox{Nb}}_{3}\hbox{Sn}$ Accelerator-Quality Quadrupole Magnet for the LHC Luminosity Upgrade

HQ01 is a superconducting quadrupole magnet under development by the LHC Accelerator Research Program (LARP) as a part of an R&D effort to demonstrate that Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn magnet technology is a viable option for a future luminosity upgrade of the LHC. The design is characterized by a 120 mm bore, a maximum gradient of 219 T/m at 1.9 K, and a support structure based on an aluminum shell pre-tensioned by water-pressurized bladders. The shell-based structure concept has already been successfully implemented in previous LARP quadrupole magnets. In HQ01, the structure incorporates additional features designed to provide full alignment between the support structure components and the coils. Specifically, the coil azimuthal alignment is achieved through outer layer pole keys which, by intercepting part of the force applied by bladders and shell, remain clamped to bolted aluminum collars from assembly to full excitation. A sequence of assemblies and cool-downs were executed with different keys sizes to characterize the alignment system and its impact on coil pre-load, at both room temperature and at 4.5 K. This paper reports on the mechanical behavior of the HQ01, by summarizing the strain gauge data and comparing them with FEM model predictions.

Development of the Superconducting Quadrupole Magnet for the SuperKEKB Final Focusing System

We have developed the superconducting final-focus quadrupoles for SuperKEKB, the next generation B-factory experiment in Japan. The system consists of four quadrupole doublets for incoming and outgoing electron and positron beams, respectively. A R&D superconducting quadrupole magnet was fabricated. In this paper, we describe the results on the excitation test and the magnetic field measurements of this R&D magnet.

Superconducting Splittable Quadrupole Magnet for Linear Accelerators

A new superconducting quadrupole magnet for linear accelerators was fabricated at Fermilab. The magnet is designed to work inside a cryomodule in the space between SCRF cavities. SCRF cavities must be installed inside a very clean room adding issues to the magnet design, and fabrication. The designed magnet has a splittable along the vertical plane configuration and could be installed outside of the clean room around the beam pipe previously connected to neighboring cavities. For more convenient assembly and replacement a “superferric” magnet configuration with four racetrack type coils was chosen. The magnet does not have a helium vessel and is conductively cooled from the cryomodule LHe supply pipe and a helium gas return pipe. The quadrupole generates 36 T integrated magnetic field gradient, has 600 mm effective length, and the peak gradient is 54 T/m. In this paper the quadrupole magnetic, mechanical, and thermal designs are presented, along with the magnet fabrication overview and first test results.

Simulation of Electromagnetic and Thermal Processes in Fastcycling Magnets for Calculation Parameters of Stability

Abstract SIS300 fast-cycling superconducting quadrupole magnet is developed at IHEP. Temperature margin and minimum quench energy are main parameters of stability of superconducting magnets. These parameters are important for the design and safe operation of superconducting magnets. But additional understanding for fast-cycling superconducting magnets is needed. To calculate the temperature margin one needs coupled numerical transient simulation of electromagnetic and thermal processes in the coil because critical temperature, operating temperature and AC losses are nonuniform over turns and their magnitudes vary in time during accelerator cycles. For calculation of the minimum quench energy the combination of the network model with thermal analysis is necessary, which allows one to model quench dynamics, including the effects of a current redistribution between strands of cable and spatial inhomogeneity of cable. Results for the temperature margin and the minimum quench energy for the magnet are presented and theirs dependence on various parameters is discussed.

Novel Ways of Heat Removal from Highly Irradiated Superconducting Windings in Accelerator Magnets

Novel ideas of heat removal from superconducting windings in accelerator type magnets are investigated with the help of a recently developed and validated thermal model of a magnet cold mass implemented in COMSOL Multiphysics. Here the focus is on how to improve heat removal from the midplane of a superconducting quadrupole magnet, the area exposed to the highest radiation heat load. In addition, this part of the coil windings has the longest thermal path towards the heat sink and several thermal design improvements proposed in the past are not very effective here. It is shown that with minor changes in the geometrical design, the cooling of the midplane conductors can be strongly increased

Design and Construction of the Final Focus Quadrupole R&amp;D Magnet for Super-KEKB

For upgrading the electron-positron collider KEKB, the final focusing magnet system in the beam interaction region has been studied. The designed magnet system consists of five superconducting and three permanent quadrupole magnets. A superconducting quadrupole magnet has been constructed as the R&D of this system. In this paper, design and construction of this R&D magnet are reported.

Radiation Resistant Superferric Quadrupole Magnets With Warm Iron

The Facility for Rare Isotope Beams to be built at Michigan State University will be capable of providing beams of any element at energies of at least 200 MeV/u at beam powers of 400 kW. The fragment production target is in close proximity to the superconducting quadrupole magnets. These magnets have to operate in the high-radiation environment, with calculated radiation doses of more than 10 MGy per year. The design of a large bore, superferric quadrupole magnet that provides high field gradient of 15 T/m and effective length of 0.6 m is presented. The current design is “warm-iron” with a nominal yoke length of 520 mm and a pole radius of 135 mm. A coil design based on spinel insulated cable-in-conduit conductor that provides ample current margin provides significant long lifetime against radiation damage. The major challenges are the tight geometry, high forces and remote handling of an irradiated magnet. This paper presents the magnet design including coil forces and coil restraint system. In addition, coil properties, conductor stability and full mechanical details are also presented.

Analysis of the Factors Affecting Field Quality and Heat Releases of the Quadrupole Magnet for the SIS 300

IHEP has developed a design of a superconducting quadrupole magnet for the SIS 300, project FAIR. The main parameters of this quadrupole are: 45-T/m central gradient with the gradient ramp rate of 10 T/m/sec in the useful aperture of 105 mm and the coil ID of 125 mm; the geometric length of the magnet is 1 m. This work includes the analysis of the factors affecting field quality and heat releases of the quadrupole magnet for the SIS 300. Particularly, influence of the weak magnetic elements of the design on the field quality in the magnet is examined as well as the effect of generated heat releases in the resistive parts on the temperature margin in the quadrupole. Tolerances for the manufacturing accuracy of various geometrical parameters are presented. Examination of the parameters affecting the integral field quality is described. Presented law of dependence of low integral field multipoles on both thickness of the spacer and its position in the end parts allows one to quickly find optimized geometry with a viewpoint of the integral field quality.

Control application of a superconducting magnet power supply based on EPICS

The superconducting quadrupole magnets (SCQs) are powered by 16 power supplies in the interaction region of the BEPCII. The control application of these power supplies must be interlocked with the quench protection system to protect the superconducting magnet and relevant devices. This paper describes the development procedures of this control application using EPICS and the operating result with the quench protection system on-site.