Permanent magnets (PMs) have been used for some time incharged particle accelerators. Historically, their temperaturestability has been achieved by either the selection of a PMmaterial which has an inherently small magnetic variation withtemperature or by active control of the thermal environment.These approaches have the disadvantages of high cost andincreased complexity, respectively. An alternative is to useinexpensive ceramic ferrite PM material coupled with a passiveflux shunt to compensate for the relatively high temperaturesensitivity of that material. Potential applications includelarge fixed strength storage rings. For these, a method topassively compensate for the effects of temperature on the fieldstrength of the PM material 31 will enable inexpensive, simple,and reliable magnets to replace the more expensive resistivemagnets used now. This project will develop and demonstrate apassive method for reducing the effects of temperature on thefield strength of a permanent magnet iron core dipole, as wouldbe used in a storage ring. This will be done by using a fluxshunt made from a material with a saturation induction thatvaries with temperature. Phase I will concentrate on optimizingthe design of such a magnet to minimize the effect of temperatureand overall cost. A one meter long model will be fabricated todemonstrate feasibility. This will lead to a full scale prototypein Phase II and/or adaptation of the method to PM quadrupole andsextupole magnets. Anticipated Results/Potential Commercial Applications as described by the awardee: It is anticipated that this method willlead to magnet designs that are substantially more cost effectivethan resistive magnets, with field temperature stability suitedfor use in particle storage rings. The use of PMs in thisapplication will also result in an overall gain in systemreliability. The elimination of power supplies, coolingrequirements, interlocks, and controls not only reduces overallsystem costs, but makes the system immune to short interruptionsin power. Specifically, the technology developed here is directlyapplicable to the proposed luminosity upgrade at the FermiNational Accelerator Laboratory, as well as light sources,stretcher rings, beamlines, and other accelerator structures.
