We study the coil layouts of superconducting dipoles for particle accelerators based on the sector geometry. We show that a simple model based on a sector coil with a wedge allows us to derive an equation giving the short sample field as a function of the aperture, coil width, cable properties, and superconducting material. The equation agrees well with the actual results of several dipole coils that have been built in the past 30 years. The improvements due to the grading technique and the iron yoke are also studied. The proposed equation can be used as a benchmark to judge the efficiency of the coil design, and to carry out a global optimization of an accelerator layout.

/pdf/electromagnetic-design-of-superconducting-dipoles-based-on-2u59x0i0zw.pdf

Electromagnetic design of superconducting dipoles based on sector coils

We report preliminary considerations for a higher-energy LHC (“HE-LHC”) with about 16.5 TeV beam energy and 20-T dipole magnets. In particular we sketch the proposed principal parameters, luminosity optimization schemes, the new HE-LHC injector, the magnets required, cryogenics system, collimation issues, and requirements from the vacuum system.

https://cds.cern.ch/record/1284326/files/CERN-ATS-2010-177.pdf

First Thoughts on a Higher-Energy LHC

The time variation in the magnetic field of a model Tevatron dipole magnet at constant excitation current has been studied. Variations in symmetry allowed harmonic components over long time ranges show a log t behavior indicative of 'flux creep'. Both short-time-range and long-time-range behavior depend on the excitation history. Similar effects are seen in the remnant fields present in full-scale Tevatron dipoles following current ramping. Both magnitudes and time dependences are observed to depend on details such as ramp rate, flattop duration, and number of ramps. In a few magnets, variations are also seen in symmetry-disallowed harmonics. >

/pdf/studies-of-time-dependence-of-fields-in-tevatron-qzg99e4cj4.pdf

Studies of time dependence of fields in Tevatron superconducting dipole magnets

Superconducting magnets have played a key role in advancing the energy reach of proton synchrotrons and enabling them to play a major role in defining the Standard Model. The problems encountered and solved at the Tevatron are described and used as an introduction to the many challenges posed by the use of this technology. The LHC is being prepared to answer the many questions beyond the Standard Model and in itself is at the cutting edge of technology. A description of its magnets and their properties is given to illustrate the advances that have been made in the use of superconducting magnets over the past 30 years.

/pdf/the-development-of-superconducting-magnets-for-use-in-tjczjahfao.pdf

The Development of Superconducting Magnets for Use in Particle Accelerators: From the Tevatron to the LHC

Availability of 20 T operational field dipole magnets would open the way for a 165 TeV beam energy accelerator in the LHC tunnel Here we discuss the main issues related to the magnet design of this extremely challenging dipole: main constraints, superconductor choice, coil lay-out, iron, forces and stresses, and field quality A tentative cost estimate is also given The present technology, based on Nb-Ti and now near to be extended to Nb3Sn superconductor, would allow reaching 15 T operational field To reach 20 T, HTS conductors capable to carry 400 A/mm 2 at 15-20 T under transverse stress of 150-200 MPa are an essential element

/pdf/conceptual-design-of-20-t-dipoles-for-high-energy-lhc-4q0vhtoboy.pdf

Conceptual design of 20 T dipoles for high-energy LHC

At Fermilab we have operated a production line for the fabrication of 901 21 foot long superconducting dipoles for use in the Energy Saver/Doubler. At any one time 772 of these dipoles are installed in the accelerator and 62 in beamlines; the remainder are spares. Magnetic field data are now available for most of these dipoles; in this paper we present some of these data which show that we have been able to maintain the necessary consistency in field quality throughout the production process. Specifically we report harmonic field coefficients, showing that the mechanical design permits substantial reduction of the magnitudes of the normal and skew quadrupole harmonic coefficients; field shape profiles; integral field data; and field angle data. Details of the measurement apparatus and procedures are described elsewhere.

/pdf/magnetic-field-properties-of-fermilab-energy-saver-dipoles-137clb3b7o.pdf

Magnetic Field Properties of Fermilab Energy Saver Dipoles

The measurement system and procedures used to test more than 900 superconducting dipole magnets and more than 275 superconducting quadrupole magnets for the Fermilab Energy Saver are described. The system is designed to measure nearly all parameters relevant to the use of the magnets in the accelerator including maximum field capability and precision field measurements. The performance of the instrumentation with regard to precision, reliability, and operational needs for high volume testing will be described. Previous reports have described the measurement system used during development of the Saver magnets from which this system has evolved.

/pdf/report-on-the-production-magnet-measurement-system-for-the-1isx4awrz4.pdf

Report on the Production Magnet Measurement System for the Fermilab Energy Saver Superconducting Dipoles and Quadrupoles

The Fermilab Energy Saver/Doubler (Tevatron) accelerator contains 216 superconducting quadrupole magnets Before installation in the Tevatron ring, these magnets plus an additional number of spares were extensively tested at the Fermilab Magnet Test Facility (MTF) Details on the results of the tests are presented here

Magnetic Field Data on Fermilab Energy Saver Quadrupoles

The quench and field properties of Energy Saver dipole and quadrupole magnets are measured at the Fermilab Magnet Test Facility shortly after the magnets have been produced. It is important that magnet properties remain unchanged with time. This question has been investigated by remeasuring magnets at a later time and comparing the two sets of measurements. Three sets of unbiased data are available: 1) Fifteen dipole magnets were remeasured after they were removed from the "B12" cryoloop test location. At B12, they were subjected to repeated thermal cycles, quenches at high current, steady state operation at high current, and ramping to high current with an accelerator type ramp cycle. The average time between the original measurement and the remeasurement was 22 months. 2) Five standard length (66 inch) quadrupole magnets were remeasured after an elapsed time averaging 5 months. These magnets were in storage during the period between the two sets of measurements. 3) Six long (99 inch) quadrupole magnets were remeasured after an average time of 12 days. These were also in storage. The remeasurements agree well with the original measurements. The measurement techniques and magnet properties obtained from the full magnet samples are described elsewhere.

/pdf/long-term-stability-of-fermilab-energy-saver-magnets-2r7dbjfdj7.pdf

E. E. Schmidt

Papers

Magnetic Field Properties of Fermilab Energy Saver Dipoles

Report on the Production Magnet Measurement System for the Fermilab Energy Saver Superconducting Dipoles and Quadrupoles

Magnetic Field Data on Fermilab Energy Saver Quadrupoles

Long Term Stability of Fermilab Energy Saver Magnets