Chapter 1
X-Ray Sources at Large-Scale Facilities
Philip R. Willmott
Abstract High-brilliance X-ray sources are powerful probes to investigate the properties of matter down to the sub-angstrom scale and on time scales that can extend
below a femtosecond. In this chapter, an introductory overview of the physics behind
storage ring-based synchrotrons and linear accelerator-based X-ray free-electron
lasers is presented, while the properties of the radiation they produce are explained.
1.1 Introduction
Since their discovery by Wilhelm Röntgen in the last decade of the nineteenth century,
X-rays have played a central role in all branches of the natural sciences and medicine.
The primary reasons for this are threefold. Firstly, ‘hard’ X-rays (that is, those with
photon energies in excess of a few keV and up to approximately 50 keV, see Fig. 1.1),
have interaction strengths that, on the one hand, are small enough to allow them to
penetrate deeply into solid matter, while, on the other, are sufficiently large that
these interactions are easily observable. Secondly, X-rays have wavelengths λ on
the nanometre to angstrom scale, meaning that, according to the Abbe limit, they
can be used to image objects composed of features down to sizes comparable to λ.
Finally, the binding energies of electrons, from weakly bound valence electrons to
very strongly bound core electrons in heavy elements, lie in the ultraviolet to hard
X-ray regime, allowing detailed studies of these bonds through spectroscopy, thereby
providing insights into chemistry, electronic structure and magnetic properties.
Modern scientific disciplines are increasingly concerned with correlating physical structure with physical properties. This has been long recognized in the lockand-key functionality of biological structures such as enzymes and proteins. In
condensed matter physics, the properties of many emergent materials, in particular (though not exclusively) transition metal oxides, depend exceedingly sensitively
P. R. Willmott (B)
Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland
e-mail: philip.willmott@psi.ch
URL: http://www.psi.ch/sls
© The Author(s) 2021
H. Bulou et al. (eds.), Magnetism and Accelerator-Based Light Sources,
Springer Proceedings in Physics 262,
https://doi.org/10.1007/978-3-030-64623-3_1
1
X-Ray Sources at Large-Scale Facilities
Philip R. Willmott
Abstract High-brilliance X-ray sources are powerful probes to investigate the properties of matter down to the sub-angstrom scale and on time scales that can extend
below a femtosecond. In this chapter, an introductory overview of the physics behind
storage ring-based synchrotrons and linear accelerator-based X-ray free-electron
lasers is presented, while the properties of the radiation they produce are explained.
1.1 Introduction
Since their discovery by Wilhelm Röntgen in the last decade of the nineteenth century,
X-rays have played a central role in all branches of the natural sciences and medicine.
The primary reasons for this are threefold. Firstly, ‘hard’ X-rays (that is, those with
photon energies in excess of a few keV and up to approximately 50 keV, see Fig. 1.1),
have interaction strengths that, on the one hand, are small enough to allow them to
penetrate deeply into solid matter, while, on the other, are sufficiently large that
these interactions are easily observable. Secondly, X-rays have wavelengths λ on
the nanometre to angstrom scale, meaning that, according to the Abbe limit, they
can be used to image objects composed of features down to sizes comparable to λ.
Finally, the binding energies of electrons, from weakly bound valence electrons to
very strongly bound core electrons in heavy elements, lie in the ultraviolet to hard
X-ray regime, allowing detailed studies of these bonds through spectroscopy, thereby
providing insights into chemistry, electronic structure and magnetic properties.
Modern scientific disciplines are increasingly concerned with correlating physical structure with physical properties. This has been long recognized in the lockand-key functionality of biological structures such as enzymes and proteins. In
condensed matter physics, the properties of many emergent materials, in particular (though not exclusively) transition metal oxides, depend exceedingly sensitively
P. R. Willmott (B)
Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland
e-mail: philip.willmott@psi.ch
URL: http://www.psi.ch/sls
© The Author(s) 2021
H. Bulou et al. (eds.), Magnetism and Accelerator-Based Light Sources,
Springer Proceedings in Physics 262,
https://doi.org/10.1007/978-3-030-64623-3_1
1