Mitigating Transition in the Fermilab Booster Using a Triple Phase Jump

Conference · Wed Aug 13 00:00:00 EDT 2025 · No journal information

DOI:https://doi.org/10.2172/3019356· OSTI ID:3019356

Ostiguy, Jean-Francois ^[1]; Bhat, Chandrashekhara M. ^[1]

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1. Fermilab

The PIP-II project will significantly enhance neutrino production for DUNE, Fermilab s flagship long-baseline neutrino oscillation experiment, by doubling the beam power delivered by the accelerator complex. To achieve this, the total charge injected from the new PIP-II linac into the Booster rapid cycling synchrotron (RCS) will increase from $$4.5\times 10^{12}$$ to $$6.5\times 10^{12}$$ protons per pulse. Simultaneously, the Booster s ramp rate will rise from 15 to 20 Hz, while the injection energy will go from 400 MeV to 800 MeV. The Booster accelerates the beam to 8 GeV and crosses transition at $$\gamma_t=5.45$$. In current operations, no dedicated $$\gamma_t$$ jump system is employed; instead, longitudinal emittance growth is controlled via an active quadrupole-mode feedback system. Downstream, the Recycler Ring uses slip-stacking to accumulate beam and increase bunch intensity. However, this process imposes a constraint on the longitudinal emittance at Booster extraction, limiting it to 0.1 eV-s (95\%) to avoid excessive particle loss. Because collective effects scale with intensity, additional measures to mitigate transition crossing may be required to stay below this limit. One potential approach is the so-called triple phase-jump technique. While the method has known limitations, it offers some advantages: it can be implemented using the existing digital low-level RF (LLRF) system, requires no additional magnets or pulsed power supplies, and remains compatible with quadrupole-mode feedback.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 3019356
• Report Number(s): FERMILAB-POSTER-25-0208-AD; oai:inspirehep.net:2963551
• Resource Type: Conference poster
• Conference Information: Journal Name: No journal information
• Country of Publication: United States
• Language: English