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TU2A1 |
Coherent Free-electron Laser Pulses: The User Perspective |
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- G. De Ninno
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
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Are fully-coherent pulses the Holy Grail for experiments, which aim at taking full advantage of the properties of a free-electron laser (FEL)? What are the strategies to generate and diagnose them at seeded FEL facilities? What are the requirements for experiments based on pulse shaping and coherent control? How goes it for quantum coherence and the possibility to generate FEL pulses with sub-Poissonian statistics? We will talk about all this and more.
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Slides TU2A1 [1.584 MB]
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| TU2A2 |
Single Longitudinal Mode Generation in Slippage-dominated, Tapered-undulator SASE Soft X-ray FEL |
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- D.C. Nguyen, M. Dunham, W. Lou, C.E. Mayes, G. Stupakov
xLight, Palo Alto, USA
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SASE FELs operating in the soft X-ray region exhibit multiple temporal and spectral spikes with an overall spectral bandwidth of about 1.5 times the FEL rho parameter. While many ideas have been proposed to achieve fully coherent X-ray FELs, only monochromatic seeding, either harmonic seeding* or SASE self-seeding**, has been experimentally demonstrated to narrow the output spectra of soft X-ray FELs. In this paper, we study a different method that relies on the Slippage-dominated Tapered Undulator (STU) SASE concept to produce a single longitudinal mode in a soft X-ray FEL driven by ~10-fs, 16-pC electron bunches. We pre-sent numerical simulation results that demonstrate single-mode generation and narrow-lined spectra without seeding in a STU-SASE FEL at 6.67 nm.
* E. Alaria et al., Nat Photon 7 (2013) 913-918
** D. Ratner et al., PRL 114 (2015) 050801
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Slides TU2A2 [1.125 MB]
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| DOI • |
reference for this paper
※ doi:10.18429/JACoW-FLS2023-TU2A2
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| About • |
Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023 |
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TU2A3 |
Opportunities and Challenges of the Hard X-ray Self-seeding System at the European XFEL |
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- S. Liu, P. Dijkstal, C. Grech, M.W. Guetg, V. Kocharyan, T. Long, N.S. Mirian, W. Qin
DESY, Hamburg, Germany
- G. Geloni, N.G. Kujala, C. Lechner, S. Serkez, J.W. Yan
EuXFEL, Schenefeld, Germany
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The Hard X-ray Self-seeding system (HXRSS) at the European XFEL provides users with longitudinally coherent X-ray FEL pulses with narrow bandwidth and high spectral density. With this setup we have achieved a maximum spectral density of about 1 mJ/eV at 9 keV. Combined with the MHz repetition rate, it opens up exciting new opportunities in a wide range of scientific fields. However, the increasing user demand and expectations also poses challenges in machine tuning and operation parameter ranges. We will summarize the HXRSS performance we have achieved and the user delivery experiences in the last two years.
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TU2A4 |
A Low-loss 14 m Hard X-ray Bragg-reflecting Cavity, Experiments and Analysis |
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- R.A. Margraf, Z. Huang, R. Robles
Stanford University, Stanford, California, USA
- A. Halavanau, Z. Huang, J. Krzywiński, K. Li, J.P. MacArthur, G. Marcus, R. Robles, A. Sakdinawat, T. Sato, Y. Sun, D. Zhu
SLAC, Menlo Park, California, USA
- T. Osaka, K. Tamasaku
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
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Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
Bragg-reflecting cavities on the 10 s or 100 s of meter scale are a core component of proposed Cavity-Based X-ray Free-Electron Lasers (CBXFELs). While CBXFELs promise improved longitudinal coherence and spectral brightness over single-pass self-amplification of spontaneous radiation (SASE) FELs, construction and alignment of large Bragg-reflecting cavities can be difficult technical challenge. Our collaboration recently demonstrated stable operation of a low-loss 14 m 9.831 keV X-ray cavity of four Bragg-reflecting diamond mirrors*, a significant step towards a CBXFEL-scale cavity. We in-coupled X-rays from the Linac Coherent Light Source (LCLS) into our cavity via a transmission grating, then measured round-trip efficiencies approaching 88%, or >96% when neglecting losses on in-coupling and focusing optics. Additionally, we characterized transverse oscillations in the cavity, demonstrating the effectiveness of our cavity focusing. We will discuss these results, additional new analysis and consider implications for future CBXFEL projects.
* R. Margraf et al., ‘Low-loss Stable Storage of X-ray Free Electron Laser Pulses in a 14 m Rectangular Bragg Cavity’, In Review, preprint, 2023. doi: 10.21203/rs.3.rs-2465216/v1.
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Slides TU2A4 [3.245 MB]
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