Poster

PUBDB-2026-03065

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Resonant filling for long pulse operation of EuXFEL using iterative learning based feed forward

Richter, B. (Corresponding author)DESY* ; Einstein-Curtis, J.DESY* ; Branlard, J.DESY*

2026

Abstract: A future operation scenario of the European XFEL (EuXFEL) is long pulse (LP) mode, where the 800 superconducting radio frequency (SRF) cavities of the linac are energized with RF pulse lengths of up to 500ms, in contrast to the current short pulse (SP) mode with only 1.4ms. To improve energy efficiency of LP operation, cavities must be operated at bandwidths in the range of tens of Hertz, narrower by a factor of 10 than in SP. Due to peak power limitation of the proposed high power amplifiers, the fill time will extend to several milliseconds, surpassing the period of mechanical resonances of TESLA cavities. To ensure RF filling on resonance, Lorenz force detuning induced cavity phase shifts are tracked by employing iterative learning control (ILC) on the incident RF phase in a single cavity regulation setup. In vector-sum RF regulation systems, the incident phase cannot be adjusted to each cavity individually. Hence, the concept is inverted by employing ILC on mechanical cavity tuners to align each individual cavity resonance with the common RF drive. Both approaches are simulated and evaluated experimentally. This work is a follow-up to work presented at LLRF25.

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Contributing Institute(s):

1. Strahlkontrollen (MSK)

Research Program(s):

1. 621 - Accelerator Research and Development (POF4-621) (POF4-621)
2. 6G13 - Accelerator of European XFEL (POF4-6G13) (POF4-6G13)
3. iSAS - Innovate for Sustainable Accelerating Systems (101131435) (101131435)

Experiment(s):

1. Facility (machine) XFEL

Appears in the scientific report 2026

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