Conference Presentation

PUBDB-2026-02555

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Reverse undulator tapering for polarization control and short pulse generation

Schneidmiller, E. A. (Corresponding author)XFEL.EU*DESY*

2026

Abstract: Reverse undulator taper is a unique method allowing to strongly suppress radiation intensity at the exit of SASE undulator while maintaining microbunching at a significant level. Recently, it was used to generate high-purity circularly polarized radiation from dedicated afterburners (Apple-X at the European XFEL and Apple-III at FLASH, the latter operates at the 3rd harmonic of SASE undulator). Chirp-taper compensation is another method where a reverse taper is typically used to generate attosecond pulses in X-ray FELs. Recent results from the European XFEL on generation of extremely short (~ 100 as) and intense (~ 10 TW) pulses in soft X-ray regime are presented. Finally, so-called excessive reverse taper (beyond the compensation condition) helps to generate short pulses well below cooperation length limit. The validity of the concept is illustrated by the experimental results from FLASH.

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Contributing Institute(s):

1. Beschleunigerphysik (MPY)

Research Program(s):

1. 621 - Accelerator Research and Development (POF4-621) (POF4-621)
2. 6G13 - Accelerator of European XFEL (POF4-6G13) (POF4-6G13)
3. 6G2 - FLASH (DESY) (POF4-6G2) (POF4-6G2)

Experiment(s):

1. Facility (machine) FLASH2
2. Experiments at XFEL

Appears in the scientific report 2026

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