Ripple Mitigation for Slow Extraction Beam Quality Improvement

IFAST-REX concerns the study of beam extraction dynamics with the main goal of applying practical technical mitigations of beam current fluctuations on the 10 µs to 10 ms time scale for a slowly extracted beam from a synchrotron, also referred to as spill micro-structure. Depending on the slow extraction mechanism, the dominant fluctuations are either caused by ripples of power supply currents for quadrupole magnets, causing a variation of the tune or by the excitation signal for utilized in transverse knock-out extraction. Within IFAST-REX, intensive beam-dynamics studies were performed to minimise the beam response and evaluate robust parameters to smoothen the extracted beam current. Experimental verifications at various facilities provide significant insight into the corresponding accelerator-physics.
The engineering design for two innovative technical systems was performed as a second task. The first device concerns the measurement of the magnet power supply ripples ΔIAC in the presence of a strong DC current IDC. A resolution of ΔIAC/IDC < 10-6 is reached within a bandwidth of 10 Hz to 40 kHz. The second topic contains the low-level control electronics and power amplification chain for the knock-out extraction, providing a power of 500 W within a bandwidth from 0.1 to 20 MHz. For the control, the versatile Software Defined Radio technology is now used on an operational basis and provides multi-band excitations and online feedback; TRL 7 is reached.

The project goal concerning the micro-structure improvement of slow extraction was achieved by the IFAST-REX partners' common effort, as documented in this report.