Interaction Region Quadrupoles Research Articles

Characterization of NbTi Busbar for HL-LHC Interaction Region Quadrupoles

The US Accelerator Upgrade for the HiLumi-LHC (US-HL-LHC AUP) project and CERN are designing and fabricating superconducting quadrupole magnets for the interaction regions of the High Luminosity Large Hadron Collider (HL-LHC). The triplet is made of three optical elements: Q1, Q2, and Q3. The Nb3Sn quadrupole magnets operate in superfluid He at 1.9 K with a nominal field gradient of 132.6 T/m. The three inner triplet elements are connected together with superconducting buses. The design and fabrication of the through and local buses is carried out at Applied Physics and Superconducting Technology Division (APS-TD) at Fermilab (FNAL). This paper reports the characterization of the bus-bar thermo-electric properties. The bus was tested with a short Nb3Sn magnet (MQXFS1e) in the vertical test facility of the APS-TD at FNAL. The test demonstrated that the bus design is adequate since no spontaneous quench took place up to 17.89 kA current value. Quench propagation velocities were investigated over a range of currents that is typical for accelerator superconducting magnets. Temperature margins were found above that required for the Hi-Lumi triplet bus. The design guarantees the protection of the bus at operational current value according to the quench detection voltage threshold (100 mV) established for the Hi-Lumi LHC interaction region.

Fracture Failure Analysis for MQXFA Magnet Aluminum Shells

The High-Luminosity LHC Accelerator Upgrade Project (HL-LHC AUP) is approaching the production phase of the US-contributed Q1 and Q3 Interaction Region Quadrupoles (MQXFA). The structures for the MQXFA prototypes were designed and inspected by the US-LARP (LHC Accelerator Research Program), AUP developed criteria, which will be used for the pre-series structures. The first two full-length prototypes with 4.2 m magnetic length, MQXFAP1 and MQXFAP2, were designed and assembled at Lawrence Berkeley National Laboratory (LBNL), and tested at Brookhaven National Laboratory (BNL). The end aluminum short shell of MQXFAP2 was fractured along the shell length during the test, and tests were stopped. Analytical and Finite Element analysis were performed in light of the graded procedure defined in the Structural Design Criteria to investigate the fracture failure for MQXFAP2. In this paper, we report the fracture analysis of the current shell design, including the elasto-plastic simulations with sub-model technique, and calculations with Linear Elastic Fracture Mechanics (LEFM). Test material properties are also presented. The results of this analysis explain why the end shell of MQXFAP2 failed, and suggest fillets on the end shell notches to meet the margin specified in the Structural Design Criteria.

Optimization of an Interaction Region Quadrupole Magnet for a Future Electron-Ion Collider at JLab

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 11 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 1034cm−2 sec−1. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The lattice file for the machine has changed to accommodate the higher energy; this change requires all the magnets in the interaction region to change. This paper will describe the requirements for both the ion and electron beam superconducting magnets around the interaction point. All the Final Focusing Quadrupole (FFQ) magnets now have preliminary designs. This paper will describe the optimization process for one of these FFQs. The optimization is performed using the optimization module of SIMULIA Opera FEA and compared with ROXIE. An analytical design tool has also been developed to estimate the peak field in the coils. The quadrupole has been optimized for peak field in the coils, and magnetic length.

Modular High Field Quadrupole Design for Electron–Ion Collider

The proposed electron-ion collider (EIC) needs high-gradient, large-aperture quadrupole magnets in the interaction region (IR). This paper presents the work under a Small Business Innovation Research Phase I grant to Particle Beam Lasers, Inc., and Brookhaven National Laboratory (BNL) to develop a novel modular design for EIC quadrupoles based on racetrack coils, which need no expensive tooling to build. It also enables the same coils to be used in Nb3Sn magnets of a range of apertures. Such a modular program may greatly facilitate R&D and reduce its costs, which often dominate the total cost of magnets that are one-of-a-kind or produced in limited numbers. For the EIC IR, the same coils are used in four R&D quadrupoles: one Nb3Sn quadrupole as proposed for the BNL eRHIC and three Nb3Sn quadrupoles as proposed by Jefferson Laboratory for JLEIC. This paper will present the basic magnetic and mechanical design of the several IR quadrupoles for the proposed EIC.

Fabrication and Analysis of 150 mm Aperture Nb<sub>3</sub>Sn LARP MQXF Coils

The U.S. LHC Accelerator Research Program (LARP) and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150-mm-aperture, interaction region quadrupoles with a nominal gradient of 130 T/m using Nb3Sn. To successfully produce the necessary long MQXF triplets, the HiLumi-LHC collaboration is systematically reducing risk and design modification by heavily relying upon the experience gained from the successful 120-mm-aperture LARP HQ program. First generation MQXF short (MQXFS) coils were predominately a scaling up of the HQ quadrupole design allowing comparable cable expansion during Nb3Sn formation heat treatment and increased insulation fraction for electrical robustness. A total of 13 first generation MQXFS coils were fabricated between LARP and CERN. Systematic differences in coil size, coil alignment symmetry, and coil length contraction during heat treatment are observed and likely due to slight variances in tooling and insulation/cable systems. Analysis of coil cross sections indicate that field-shaping wedges and adjacent coil turns are systematically displaced from the nominal location and the cable is expanding less than nominally designed. Lastly, a second generation MQXF coil design seeks to correct the expansion and displacement discrepancies by increasing insulation and adding adjustable shims at the coil pole and midplanes to correct allowed magneticmore » field harmonics.« less

Design of a 120 mm Bore 15 T Quadrupole for the LHC Upgrade Phase II

Future upgrades to machines like the Large Hadron Collider (LHC) at CERN will push accelerator magnets beyond 10 T forcing the replacement of NbTi superconductors with advanced superconductors such as Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn. In support of the LHC Phase-II upgrade, the US LHC Accelerator Research Program (LARP) is developing a large bore (120 mm) Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Interaction Region (IR) quadrupole (HQ) capable of reaching 15 T at its conductor limit and gradients of 199 T/m at 4.4 K and 219 T/m at 1.9 K. The 1 m long, two-layer magnet, addresses coil alignment and accelerator quality features while exploring the magnet performance limits in terms of gradient, stress and structure. This paper summarizes and reports on the design, mechanical structure, coil windings, reaction and impregnation processes.

Compact IR Quadrupoles for Linear Colliders Based on Rutherford-Type Cable

The upcoming and disrupted beams in the interaction region (IR) of a linear collider are focused by doublets consisting of two small-aperture superconducting quadrupoles. These magnets need an effective compact magnetic shielding to minimize magnetic coupling between the two channels and sufficient temperature margin to withstand radiation-induced heat depositions in the coil. This paper presents conceptual designs of IR quadrupoles for linear colliders based on NbTi and Nb3Sn Rutherford-type cables.

Alignment and Strength Measurements of the LHC Interaction Region Quadrupole Magnets

Production and testing of the high-gradient superconducting quadrupole magnets developed by the US-LHC accelerator project is being completed. The production process included relative alignment of the two MQXB cold masses of the LQXB in a single cryostat, alignment of corrector magnet assemblies supplied by CERN on each of the triplet elements, and final magnet alignment for transfer to cryostat fiducials. Additionally, all LQXB magnets and one each of the LQXA and LQXC have had alignment measurements at Fermilab's magnet test facility (MTF) during cryogenic testing. This paper gives an overview and summary of the available alignment and strength data taken with the single stretched wire (SSW) system for the LQX magnets. Warm-to-cold changes in alignment parameters are also presented.

Quench Antenna Studies of Mechanical and Quench Performance in Fermilab Interaction Region Quadrupoles for LHC

As part of the US-LHC collaboration, Fermilab has built and tested seventeen high gradient quadrupole magnets, assembled into nine cryostats, for installation at the Large Hadron Collider Interaction Regions. Most of these magnets have only quarter coil voltage taps for quench characterization, but the magnetic measurement warm bore is instrumented with a quench antenna for localization and characterization. We report on studies using the quench antenna for pre-production prototype (with extensive voltage taps) and 17 production magnets. These include a summary of quench localization and development characteristics, as well as general features of flux changes observed during training ramps

Production LHC HTS Power Lead Test Results

The Fermilab Magnet test facility has built and operated a test stand to characterize the performance of HTS power leads. We report here the results of production tests of 20 pairs of 7.5 kA HTS power leads manufactured by industry for installation in feed boxes for the LHC Interaction Region quadrupole strings. Included are discussions of the thermal, electrical, and quench characteristics under standard and extreme operating conditions, and the stability of performance across thermal cycles.

LHC Interaction Region Quadrupole Cryostat Production, Alignment, and Performance Summary

The cryostat of a large hadron collider (LHC) interaction region (IR) quadrupole magnet consists of all components of the inner triplet except the magnet assembly itself. It serves to support the magnet accurately and reliably within the vacuum vessel, to provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. The major components of the cryostat are the vacuum vessel, thermal shield, multi-layer insulation system, cryogenic piping, interconnections, and suspension system. While responsibility for the design and manufacture of the main quadrupole elements is divided between Fermilab and KEK, Fermilab alone is responsible for the design and final assembly of the cryostat for the LHC inner triplets. This paper describes the experience gained during fabrication of the first complete Q2 magnets, the alignment operation and results, and the cryogenic performance of the magnet on the test stand at Fermilab.

Production and performance of the LHC interaction region quadrupoles at KEK

The MQXA superconducting low-beta quadrupole magnets for the LHC interaction regions are required to generate a field gradient of up to 215 T/m at 1.9 K along an effective magnetic length of 6.37 m. After completion of an R&D program on short models and full length prototypes, the series production of magnets has started, with to date five series magnets subsequently tested at KEK. Basic characteristics such as normal training, subsequent full energy dump, thermal cycle, ramp rate dependence and temperature dependence have been studied and results indicate that magnets have satisfactory quench performance. Magnetic field measurements performed at 1.9 K show the field quality to be uniform and to satisfy the stringent beam optics requirements.

LHC interaction region quadrupole cryostat design and fabrication

The cryostat of a Large Hadron Collider (LHC) Interaction Region (IR) quadrupole magnet consists of all components of the inner triplet except the magnet assembly itself. It serves to support the magnet accurately and reliably within the vacuum vessel, to house all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations, and must be able to be manufactured at low cost. The major components of the cryostat are the vacuum vessel, thermal shield, multilayer insulation system, cryogenic piping, and suspension system. The overall design of a cryostat for superconducting accelerator magnets requires consideration of fluid flow, proper selection of materials for their thermal and structural performance at both ambient and operating temperature, and knowledge of the environment to which the magnets will be subjected over the course of their expected operating lifetime. This paper describes the current LHC IR inner triplet quadrupole magnet cryostats being designed and manufactured at Fermilab as part of the US-LHC collaboration, and includes discussions on the structural and thermal considerations involved in the development of each of the major systems.

Thermal studies of a high gradient quadrupole magnet cooled with pressurized, stagnant superfluid

A 2-m long superconducting model of an LHC Interaction Region quadrupole magnet was wound with stabrite coated cable. The resulting low interstrand resistance and high AC losses presented the opportunity to measure magnet quench performance in superfluid as a function of helium temperature and heat deposition in the coil. Our motivation was to duplicate the high radiation heat loads predicted for the inner triplet quadrupoles at LHC and study the coil cooling conditions in the magnet. At the Magnet Test Facility in Fermilab's Technical Division, the magnet quench performance was tested as a function of bulk helium temperature and current ramp rate near the planned high luminosity interaction region field gradient of 205 T/m. AC loss measurements provided a correlation between current ramp rate and heat deposition in the coil. Analysis indicates that the results are consistent with there being little participation of superfluid helium in the small channels inside the inner layer in the heat removal from the coil. However magnet performance will be limited by the outer coil pole turn in LHC at a current level well above the operating current.

Superconducting 13 cm corrector magnets for the Relativistic Heavy Ion Collider (RHIC)

A total of 72 corrector magnets of 13 cm aperture and 0.5 m length are required in RHIC to correct for field errors in the interaction region quadrupoles and for other global corrections. The coils for these magnets were wound on a flat substrate using a computer controlled machine. Each corrector has four such coils of multipolar orders ranging from the dipole through the dodecapole, wrapped onto support tubes and concentrically assembled inside an iron yoke. There are five different model types depending on the combination of coils used. A critical issue was the alignment of the magnetic centers and the field angles of various coils. Adjustable shims were incorporated in the design to deal with unacceptable misalignments that could result from construction tolerances. Each magnet was partially assembled with nominal shims and was warm-measured with a rotating coil system. The shims were then adjusted as necessary to keep the field angles within /spl plusmn/1 mrad, and the relative alignment of the magnetic centers within /spl plusmn/0.2 mm. The field error harmonics are typically below 1% of the dominant multipole term at a reference radius of 40 mm, with some exceptions. All the magnets were tested for reliable operation at 4.35 K by performing bipolar power cycles to the maximum test current of 70 A for the dipole and 100 A for all the other coils, well above the maximum operating current of 50 A.

Analysis of parameters affecting beam gauge performance

Beam gauges have been used in the last decade or so for measuring the internal azimuthal compressive coil stresses in superconducting magnets. In early model Large Hadron Collider Interaction Region (LHC IR) quadrupoles tested at Fermilab, the beam gauges indicated excessively high amounts of inner and outer coil prestress during the collaring process, inconsistent with the coil size and modulus data. In response to these measurements, a simple mechanics based quantitative understanding of different factors affecting beam gauges has been developed. A finite element model with contact elements and non-linear material behavior, confirmed with experimental results, was developed. The results indicate that a small plastic deformation of either the beam or the backing plate can cause significant errors in the measured stress values. The effect of variations in coil modulus and support boundary conditions on beam gauge performance are also discussed.

Quench protection studies of LHC interaction region quadrupoles at Fermilab

High gradient quadrupoles are being developed by the US-LHC Accelerator Project for the LHC interaction region inner triplets. Protection strip heaters are the primary means of protecting these magnets against excessively high coil temperatures and coil voltage to ground as a result of a spontaneous quench. The main objective of the quench protection R&D program is to optimize the heater performance within the constraints of the LHC heater power supply and quench detection system. The results of these studies on several two meter long model magnets are presented.

Accurate computation of transfer maps from magnetic field data

Abstract Consider an arbitrary beamline magnet. Suppose one component (for example, the radial component) of the magnetic field is known on the surface of some imaginary cylinder coaxial to and contained within the magnet aperture. This information can be obtained either by direct measurement or by computation with the aid of some 3D electromagnetic code. Alternatively, suppose that the field harmonics have been measured by using a spinning coil. We describe how this information can be used to compute the exact transfer map for the beamline element. This transfer map takes into account all effects of real beamline elements including fringe-field, pseudo-multipole, and real multipole error effects. The method we describe automatically takes into account the smoothing properties of the Laplace–Green function. Consequently, it is robust against both measurement and electromagnetic code errors. As an illustration we apply the method to the field analysis of high-gradient interaction region quadrupoles in the Large Hadron Collider (LHC).

The pipe-quadrupole, an alternative for high gradient interaction region quadrupole designs

In the design of interaction region (IR) quadrupoles for high luminosity colliders such as the LHC or a possible upgrade of the Tevatron, the radiation heating of the coil windings is an important issue. Two obvious solutions to this problem can be chosen. The first is to reduce the heat load by added shielding, increased cooling with fins or using Nb/sub 3/Sn to increase the temperature margin. The second solution eliminates the conductor from the areas with the highest radiation intensity, which are located on the symmetry-axes of the midplanes of the coils. A novel quadrupole design is presented, in which the conductor is wound on four half-moon shaped supports, forming elongated toroid sections. The assembly of the four shapes yields a quadrupole field with an active flux return path, and a void in the high radiation area. This void can be occupied by a liquid helium cooling pipe to lower the temperature of the windings from the inside. The coil layout, harmonic optimization and mechanical design are shown, together with the calculated temperature rise for the radiation load of the LHC interaction region quadrupoles.

Superfluid performance of Tevatron IR quad heaters

Laboratories measured the performance of a Tevatron interaction region (IR) quadrupole at temperatures from 1.8 K to 4.4 K. These studies included measurement of their performance as a function of temperature as well as measurement of the effectiveness of the protection heaters. Heater diffusion times were measured for various temperatures, current levels, and power densities. These results and their implications on the design of magnet protection systems and magnet design operating in this temperature range will be discussed.