Slow Extraction with Crystal from the SPS

The third-integer resonant extraction (3rd IRE) of the proton beam from the Super Proton Synchrotron (SPS) is a critical technique used for slow extraction of particles, enabling precise delivery of protons for various high-energy physics experiments. In this method, the beam is driven into a controlled resonance condition where the horizontal oscillation frequency of the protons becomes a rational fraction (one third) of the machine’s natural frequency. This resonance, enhanced by sextupole magnets, excites stable particles beyond the separatrix and gradually extracts them over a period of time, allowing for a continuous and tunable beam spill.

However, a significant challenge of this technique is the radio-activation of key components, particularly the ZS (Z-septum) device. The ZS, which is responsible for deflecting the extracted particles, experiences intense proton interactions, leading to significant activation over time. This radio-activation complicates maintenance procedures, increases radiation exposure risks to personnel, and requires frequent interventions for decontamination.

To address this issue, an active research and development effort is aimed at replacing the ZS with bent crystals. Bent crystals have the potential to guide the beam particles with higher precision and lower interaction rates, significantly reducing the levels of radio-activation. The crystal channelling technique leverages the electromagnetic potential within a bent crystal lattice to coherently deflect particles along specific trajectories. This innovative approach promises not only to mitigate the activation problem but also to enhance the overall efficiency and control of the slow extraction process. The adoption of bent crystals could lead to safer, more reliable, and cost-effective operations within the SPS accelerator complex.

In conclusion, while third-integer resonant extraction remains a cornerstone of proton beam manipulation in high-energy physics, the transition to bent crystal technologies holds the potential to revolutionize the method, addressing the long-standing issue of radio-activation and improving long-term operational sustainability.