Proof-of-principle experiment of a novel beam extraction over millions of turns using stable resonance islands and bent crystal

Abstract

A recent study [1] has introduced an advanced method aimed at extracting from a circular particle accelerator over millions of turns using stable islands and a bent crystal. This technique leverages the strength of non-linear beam dynamics along with adiabatic trapping and transport within stable islands, in combination with a bent silicon crystal, to provide an efficient extraction of hadron beams over millions of turns. The positive and encouraging results of the comprehensive numerical simulations were validated through a successful proof-of-principle experiment at the CERN Super Proton Synchrotron, which demonstrated the feasibility of the technique. This paper presents a detailed discussion and analysis of the experimental results.

Figures (5)

• Figure 1: Left: Illustration of key devices used in the proof-of-principle measurement at the SPS. Collimators' jaws and crystal positions are shown in black, the beam orbit is shown in blue. Non-linear elements (octupoles and extraction sextupole) are marked with green and red solid lines, respectively. Magnitudes are not to scale for better visibility. The phase-space portraits at the crystal and betatron collimator are also shown. Right: Magnetic cycle (black), and deflection angle of magnets used for orbit bumps in LSS4 (blue) and LSS5 (light blue) as function of time. Key events are marked with colored dashed vertical lines.
• Figure 2: Horizontal beam profile measured using a wire scanner throughout the proof-of-principle measurement. Scans were taken in different machine cycles, and the closed orbit was subtracted from the wire position.
• Figure 3: Local losses at the location of the bent crystal as a function of the crystal orientation. A minimum in losses, corresponding to channeling, is clearly visible.
• Figure 4: Intensity evolution (left) and total losses around the ring (right) for all collimator jaw positions with different crystal configurations. The debunching, horizontal kick, start of the magnetic-field ramp, and the dump are marked by vertical black dashed lines on the panels on the left. The location of off-momentum collimator, crystal and collimator BLMs are marked by vertical black dashed lines on the panels on the right.
• Figure 5: Total losses (top row) and start of losses (bottom row) at the collimator (first column) and crystal (second column) as a function of collimator jaw position for the three crystal configurations (color).