Speaker
Description
In the framework of the High-Luminosity (HL) upgrade of the Large Hadron Collider (LHC), the bunch intensity from the injectors must be doubled with respect to the nominal design value. To meet these demands, the Super Proton Synchrotron (SPS) has been extensively upgraded to deliver $2.3 \times 10^{11}$ protons per bunch in multiple trains of up to 72 bunches. An extensive campaign of beam studies in the SPS demonstrated that all required parameters in terms of bunch intensity and length, as well as their spreads, are achieved for the relevant production schemes. Evolved tuning of the longitudinal beam properties, including controlled emittance blow-up and optimization of the higher-harmonic RF system, was essential. Sporadic non-rigid dipole oscillations, likely induced during the longitudinal blow-up, have been investigated in detail. Spectral analysis of the measured bunch position reveals prominent lines at multiples of 600 Hz, crossing the frequency band in which the blow-up is active. The impact on beam quality is evaluated, and possible mitigation strategies are discussed.
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