TY  - JOUR
AU  - Schneidmiller, Evgeny Alexanrdovich
AU  - Dreimann, Matthias
AU  - Kuhlmann, Marion
AU  - Rönsch-Schulenburg, Juliane
AU  - Zacharias, Helmut
TI  - Generation of Ultrashort Pulses in XUV and X-ray FELs via an Excessive Reverse Undulator Taper
JO  - Photonics
VL  - 10
IS  - 6
SN  - 2304-6732
CY  - Basel
PB  - MDPI
M1  - PUBDB-2023-01949
SP  - 653
PY  - 2023
AB  - The pulse duration in short-pulse schemes for Self-Amplified Spontaneous Emission Free Electron Lasers (SASE FELs) is limited by the FEL coherence time. A recently proposed concept allows to overcome the coherence time barrier and to get much shorter pulses. When the lasing part of an electron bunch is much shorter than the coherence time, one can suppress the radiation in the long main undulator while preserving microbunching within that short lasing slice. Then a short radiation pulse is produced in a relatively short radiator. A possible suppression method, an excessive reverse undulator taper, is discussed and illustrated numerically in this paper. We also performed first experimental tests of this method at the soft X-ray FEL user facility FLASH. The measured pulse duration approaches 1 fs (FWHM) at the wavelength of 5 nm.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:001015702300001
DO  - DOI:10.3390/photonics10060653
UR  - https://bib-pubdb1.desy.de/record/582403
ER  -