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Large-Bandwidth Mode of Operation for the SwissFEL Hard X-ray Beamline

English title Large-Bandwidth Mode of Operation for the SwissFEL Hard X-ray Beamline
Applicant Reiche Sven
Number 140659
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Technical Physics
Start/End 01.04.2012 - 31.03.2015
Approved amount 158'406.00
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All Disciplines (2)

Technical Physics
Theoretical Physics

Keywords (3)

Large Bandwidth X-ray ; Accelerator Physics; Free Electron Laser

Lay Summary (English)

Lay summary

In linear accelerator to drive X-ray Free-electron Lasers, such as the SwissFEL facility at the Paul Scherrer Institute, the electron bunch is compressed in several stages to achieve sufficiently high beam currents. The compressions are done by flight-time differences of the electrons in a magnetic chicane but also causes the emission of coherent synchrotron radiation shearing the electron beam in the bending plane. The bunch is no further aligned to the main axis and the FEL performance is reduced.

The design of the SwissFEL magnetic chicanes offers the possibility to counteract this shearing by corrector quadrupoles and sextupoles. In particular, this allows very strong compressions and even overcompression, which provide a special mode of operation of an X-ray FEL, which is a unique feature of the SwissFLE facility and very attractive to potential users.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants


Name Institute


Dispersion Based Beam Tilt Correction
Guetg Marc, Beutner Bolko, Prat Eduard, Reiche Sven (2013), Dispersion Based Beam Tilt Correction, JaCow, Switzerland (CERN).
Optimization of free electron laser performance by dispersion-based beam-tilt correction
Guetg Marc, Optimization of free electron laser performance by dispersion-based beam-tilt correction, in Phys. Rev. STAB, 18, 030701-1-030701-10.


In this proposal the design study for a large-bandwidth mode of operation of the hard X-ray beamline Aramis at the SwissFEL facility is proposed. It is the central part of a Ph.D. thesis in accelerator physics.This mode of operation allows for single shot spectroscopic and crystallographic measurements of time-resolved processes such as photo-induced chemical reactions in liquids or on surfaces and biochemical processes in protein crystals. To measure these structural changes, subtle differences in the spectral absorption or the Laue diffraction pattern need to be measured, which is under normal operation (non large bandwidth mode) obscured by shot-shot fluctuations of the Self-amplifying spontaneous emission (SASE) Free-electron Laser (FEL), which occur while scanning over the desired spectral range. A special large-bandwidth mode of operation can be achieved by accumulating wakefields in the main SwissFEL linac, after the electron bunch has been over-compressed in the last bunch compressor. It requires additional correction and diagnostic elements to compensate degrading effects such as the beam distortion from coherent synchrotron radiation in bending magnets.Designing and instrumentation of SwissFEL for this purpose would provide a unique mode of operation with significant interest for users, which cannot be provided by other X-ray FELs worldwide.