Collective Effects in High-Energy Physics Facilities
Collective effects play a crucial role in Higgs factories and high-energy physics facilities. Impedance effects are proportional to beam-induced voltage, with peak bunch current impacting SB effects and average current affecting MB effects. Factors like beam loading compensation and detuning of the fundamental mode are important in flavor factories like FCC-eeZ. The focus on quantitative scale and feasibility studies for controlling instabilities are key priorities in these facilities. Additionally, radiation damping and beam tilt analysis are critical considerations for optimal performance.
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Presentation Transcript
WG7 Summary: Collective Effects John Byrd and Xu Gang, conveners One talk from Na Wang (IHEP) on CEPC Collective Effects.
Collective Effects in Higgs Factories All impedance effects proportional to beam induced voltage Peak bunch current for SB effects. Average current for MB effects. V = I R E BB or narrowband impedance E Large E helps everything. Rad damping goes with E3. All instabilities for Higgs Factories appear to be below radiation damping threshold.
Effect of Pretzels: Beam tilt Requires more analysis.
FCC-eeH is a custom boutique. FCC-eeZ is a factory! The parameters of FCC-eeZ (1.4 A) put it into the class of flavor factories (B/Phi/t-c Factories) with high beam current, heavy beam loading, etc. All flavor factories have gone to single-cell RF systems to enable sufficient damping of HOMs. Beam loading compensation requires detuning of fundamental mode more than one rotation harmonic. For a 100 km ring, this could be big. Parasitic impedances can have glowing results.
TBD Focus on collective effects for FCC-eeZ to determine quantitative scale of collective effects. Required Qext in SCRF Consider Frf as part of study. Feasibility of FB systems for controlling Robinson- type and MB instabilities. Consider collective FX in boosters. CepC has almost no radiation damping at injection energy.
