This self-contained, comprehensive book describes the fundamental properties of soft x-rays and extreme ultraviolet (EUV) radiation and discusses their applications in a wide variety of fields, including EUV lithography for semiconductor chip manufacture and soft x-ray biomicroscopy. The author begins by presenting the relevant basic principles such as radiation and scattering, wave propagation, diffraction, and coherence. He then goes on to examine a broad range of phenomena and applications. The topics covered include EUV lithography, biomicroscopy, spectromicroscopy, EUV astronomy, synchrotron radiation, and soft x-ray lasers. He also provides a great deal of useful reference material such as electron binding energies, characteristic emission lines and photo-absorption cross-sections. The book will be of great interest to graduate students and researchers in engineering, physics, chemistry, and the life sciences. It will also appeal to practicing engineers involved in semiconductor fabrication and materials science.

X-Rays and Extreme Ultraviolet Radiation: Principles and Applications

The design of a versatile high-precision eight-axis
ultrahigh-vacuum-compatible polarimeter is presented. This
multipurpose instrument can be used as a self-calibrating polarization
detector for linearly and circularly polarized UV and soft-x-ray
light. It can also be used for the characterization of reflection
or transmission properties (reflectometer) or polarizing and
phase-retarding properties (ellipsometer) of any optical
element. The polarization properties of Mo/Si, Cr/C, Cr/Sc,
and Ni/Ti multilayers used in this polarimeter as polarizers in
transmission and as analyzers in reflection have been investigated
theoretically and experimentally. In the soft-x-ray range, close to
the 2p edges of Sc, Ti, and Cr, resonantly enhanced phase
retardation of the transmission polarizers of as much as 18° has been
measured. With these newly developed optical elements the complete
polarization analysis of soft-x-ray synchrotron radiation can be
extended to the water-window range from 300 to 600 eV.

Soft-x-ray polarimeter with multilayer optics: complete analysis of the polarization state of light.

At the 1.7-GeV electron storage ring BESSY II, a first source of synchrotron radiation with 100 fs pulse duration, variable (linear and circular) polarization, tunable photon energy (300 to 1400 eV), and excellent signal-to-background ratio was constructed and is now in routine operation.

Femtosecond Undulator Radiation from Sliced Electron Bunches

The crystal monochromator beamline KMC-1 at a BESSY II bending magnet covers the energy range from soft (1.7 keV) to hard x-rays (12 keV) employing the (n,-n) double crystal arrangement with constant beam offset. The monochromator is equipped with three sets of crystals, InSb, Si (111), and Si (422) which are exchangeable in situ within a few minutes. Beamline and monochromator have been optimized for high flux and high resolution. This could be achieved by (1) a windowless setup under ultrahigh-vacuum conditions up to the experiment, (2) by the use of only three optical elements to minimize reflection losses, (3) by collecting an unusually large horizontal radiation fan (6 mrad) with the toroidal premirror, and (4) the optimization of the crystal optics to the soft x-ray range necessitating quasibackscattering crystal geometry (theta(Bragg,max)=82 degrees) delivering crystal limited resolution. The multipurpose beamline is in use for a variety of user facilities such as extended x-ray absorption fine structure, ((Bio-)EXAFS) near-edge x-ray absorption fine structure (NEXAFS), absorption and fluorescence spectroscopy. Due to the windowless UHV setup the k edges of the technologically and biologically important elements such as Si, P, and S are accessible. In addition to these experiments this beamline is now extensively used for photoelectron spectroscopy at high kinetic energies. Photon flux in the 10(11)-10(12) photons/s range and beamline resolving powers of more than E/DeltaE approximately 100.000 have been measured at selected energies employing Si (nnn) high order radiation in quasibackscattering geometry, thus photoelectron spectroscopy with a total instrumental resolution of about 150 meV is possible. This article describes the design features of the beamline and reports some experimental results in the above mentioned fields.

KMC-1: A high resolution and high flux soft x-ray beamline at BESSY

Using x-ray absorption spectroscopy recent progress is achieved all over in solid state physics. This review focuses on these advances, with particular emphasis on applications to surface physics and to magnetism of ultrathin 3d and 5d films that are made possible by the use of undulators in third generation synchrotron radiation sources: the unambiguous appearance of an atomic extended x-ray absorption fine structure for atomic adsorbates and of σ* resonances in near-edge x-ray absorption fine structure spectra of oriented molecules is demonstrated. The induced magnetism at the interfaces of 3d and 5d layers is studied by x-ray magnetic circular dichroism. Fundamental aspects of the spectroscopy are clarified for rare earth crystals. The determination of the ground state properties and the detailed understanding of the underlying mechanisms was obtained by comparison of the experimental data to state-of-the-art ab initio calculations.

https://qmlab.ubc.ca/ARPES/PEOPLE/Andrea/Teaching/PHYS555_2007/XASreview.pdf

Recent advances in x-ray absorption spectroscopy

We present the design of a beamline for circularly polarised radiation from an elliptical double undulator to be built at BESSY II. The UE56 undulator of Sasaki type will emit simultaneously two angularly separated circularly polarised beams of opposite helicities. The undulator will, through emissions in first, third and fifth harmonics, provide circularly polarised radiation in the energy range 89–1328 eV. The beamline essentially consists of a plane grating monochromator (PGM) working with collimated light and employing only one set of optical elements for steering and monochromatising the two beams. A high energy resolution from 6000 to 13 000 can be achieved at a flux between about 10 10 and 10 12 photon/s, respectively. The helicity of circular polarisation can be switched dynamically in the beamline at a high rate (>100 Hz) by use of a suitable chopper. The degree of circular polarisation of the source ranging from 78 to 100% is well preserved by the beamline. In the worst case — at the lowest energy — the degree of polarisation is reduced by 5%. In the higher energy range above 357 eV the input degree of circular polarisation can even be increased by the beamline.

A novel undulator-based PGM beamline for circularly polarised synchrotron radiation at BESSY II

During 1998/99 three beamlines of the UE56-PGM type were built at BESSY-II to meet the increased need for synchrotron radiation of tuneable, i.e. linear to fully circular, polarization. We report on the results of characterization measurements, which were focused on spectral resolution, photon flux and polarization properties. The spectral resolution for all three beamlines exceeds E=DE ¼100 000 at 64.1 eV as obtained from absorption spectra of doubly excited He. The flux measurements resulted in values that closely follow the theoretical prediction of up to 1 � 10 14 photons/(s 100 mA 0.1%) at 160 eV. The degree of polarization turned out to be close to 100% with circular and linear content, each of up to 100% depending on the undulator shift value, as predicted by theory. We also give first results on the double beam mode in which both undulator modules produce horizontally separated beams. This mode was used for fast switching of the polarization, utilizing a motorized chopper in the beamline. # 2001 Published by Elsevier Science B.V.

/pdf/the-elliptically-polarized-undulator-beamlines-at-bessy-ii-2i4varz4lb.pdf

The elliptically polarized undulator beamlines at BESSY II

The first experimental results from a double undulator with crossed magnetic fields for producing circularly polarized synchrotron radiation in the vacuum ultraviolet‐soft x‐ray range are presented The observed variation of the extent of circularly polarized radiation with photon energy is discussed A strong dependence of the state and degree of polarization on the exact details of the tuning of the two undulators and the monochromator is observed This probably accounts for the measured degree of polarization being smaller than theoretically expected

Circularly polarized synchrotron radiation from the crossed undulator at BESSY

Two APPLE II type twin undulators are installed at BESSY II. They can either be operated in a chicane mode providing variable polarization at high switching rates or in a combined mode using a modulator for phase adaption. Studies on magnet block inhomogeneities have started to further improve the field quality and to reduce the effort on shimming.

Elliptically polarizing insertion devices at BESSY II

Techniques for improving the magnetic field quality of APPLE II undulators are discussed. Individual block characterization including the inhomogeneities of the magnetization permits a precise prediction of field integrals as required for sorting. Specific shimming procedures adapted to the magnetic design of APPLE II undulators have to be employed in order to meet the stringent requirements of insertion devices in third generation synchrotron radiation sources as demonstrated for BESSY.

M. Scheer

Papers

A novel undulator-based PGM beamline for circularly polarised synchrotron radiation at BESSY II

The elliptically polarized undulator beamlines at BESSY II

Circularly polarized synchrotron radiation from the crossed undulator at BESSY

Elliptically polarizing insertion devices at BESSY II

Magnetic field optimization of permanent magnet undulators for arbitrary polarization