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Description
There are 96 combined function magnets, 48 focusing and 48 defocusing, that have been in operation in the Fermi NAL Booster without a critical failure requiring replacement for over 50 years. The Proton Improvement Plan-II (PIP-II) poses risk to these magnets and Fermilab does not currently have the tooling or knowledge of process to fabricate spares. A longer straight section between two defocusing magnets is required by PIP-II to provide room for new Orbital Bump magnets at the injection region. This will be accomplished by replacing one defocusing magnet on either side of the injection region with new shorter magnets (Booster Gradient Defocusing Short, or BGDS). PIP-II also aims to increase the efficiency of the extraction region of the Booster that sees beam loss due to tight vertical aperture. To reduce this loss, a defocusing magnet will be replaced with a similar magnet with greater vertical aperture (Booster Gradient Defocusing Wide, or BGDW) upstream of the septum magnet used for extraction. The combined function magnets are void-free monolithic structures accomplished by vacuum impregnating the core and coils with epoxy resin simultaneously. They do not have a beam tube for the purpose of maximizing aperture while reducing physical dimensions, peak stored energy, and power demand. Risk of failure and need for spares will increase substantially with the implementation of PIP-II in consequence of a frequency increase from 15 Hz to 20 Hz and a 30 percent increase in peak to ground voltage. The BGDS and BGDW magnets will be fabricated in the same way as the current booster magnets so that future combined function magnet spares can be produced using learned processes. BGDS and BGDW mechanical design and vacuum pressure impregnation technique will be discussed in this paper.
