Open AccessHard X‐ray self‐seeding commissioning at PAL‐XFEL
Author(s) -
Min Chang-Ki,
Nam Inhyuk,
Yang Haeryong,
Kim Gyujin,
Shim Chi Hyun,
Ko Jun Ho,
Cho Myung-Hoon,
Heo Hoon,
Oh Bonggi,
Suh Young Jin,
Kim Min Jae,
Na Donghyun,
Kim Changbum,
Kim Yongsam,
Chun Sae Hwan,
Lee Jae Hyuk,
Kim Jangwoo,
Kim Sunam,
Eom Intae,
Kim Seung Nam,
Koo Tae-Yeong,
Rah Seungyu,
Shvyd'ko Yuri,
Shu Deming,
Kim Kwang-Je,
Terentyev Sergey,
Blank Vladimir,
Kang Heung-Sik
Publication year - 2019
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577519005460
Subject(s) - monochromator , physics , seeding , optics , brightness , free electron laser , wiggler , atomic physics , laser , electron , cathode ray , nuclear physics , wavelength , thermodynamics
A wake monochromator based on a large‐area diamond single crystal for hard X‐ray self‐seeding has been successfully installed and commissioned in the hard X‐ray free‐electron laser (FEL) at the Pohang Accelerator Laboratory with international collaboration. For this commissioning, the self‐seeding was demonstrated with a low bunch charge (40 pC) and the nominal bunch charge (180 pC) of self‐amplified spontaneous emission (SASE) operation. The FEL pulse lengths were estimated as 7 fs and 29.5 fs, respectively. In both cases, the average spectral brightness increased by more than three times compared with the SASE mode. The self‐seeding experiment was demonstrated for the first time using a crystal with a thickness of 30 µm, and a narrow bandwidth of 0.22 eV (full width at half‐maximum) was obtained at 8.3 keV, which confirmed the functionality of a crystal with such a small thickness. In the nominal bunch‐charge self‐seeding experiment, the histogram of the intensity integrated over a 1 eV bandwidth showed a well defined Gaussian profile, which is evidence of the saturated FEL and a minimal electron‐energy jitter (∼1.2 × 10 −4 ) effect. The corresponding low photon‐energy jitter (∼2.4 × 10 −4 ) of the SASE FEL pulse, which is two times lower than the Pierce parameter, enabled the seeding power to be maximized by maintaining the spectral overlap between SASE FEL gain and the monochromator.