Improved temporal coherence and short pulse generation in free electron lasers

The output from a Self-Amplified Spontaneous Emission (SASE) Free-Electron Laser (FEL) has poor temporal coherence because the SASE process is a localised collective interaction that occurs on a scale far smaller than the typical length of the electron bunch used within the FEL. In this thesis a new technique, called High-Brightness SASE [1], is described in which the temporal alignment between radiation and electrons in the FEL is manipulated using magnetic chicanes. This delocalises the SASE process allowing the temporal coherence length of the radiation to grow exponentially and be extended by up to two orders of magnitude. Simulations are shown which indicate the technique may generate fully transformlimited FEL pulses in the hard X-ray at 0.15 nm. In the second part of the thesis it is shown how the magnetic chicanes may be used to synthesise the effect of an optical cavity with an axial mode structure, and how these axial modes may be phase locked, using concepts from conventional lasers, to produce FEL pulses with durations an order of magnitude shorter than those predicted by other short pulse schemes. This technique is called the Mode-Locked Amplifier FEL [2] and simulations are shown which predict pulse durations of approximately 20 attoseconds in the hard X-ray at 0.15 nm.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2013

Author dc:creator

• Thompson, Neil Roger

DOI

10.48730/ezva-yc38

Identifier

T13599

OAI identifier oai:identifier

oai:strathclyde:3f462547h