New Scientific Opportunities at the European Synchrotron Radiation ...

European Synchrotron Radiation Facility Long-Term Strategy 7 July 2006
4. Beamlines, Experimental, Scientific and Computer Infrastructure and
Instrumentation Developments
4.1 Introduction: optics and nano-focusing
New science is the driving force behind the ESRF’s long-term strategy. A common
feature of the new science summarised in Section 2.3 is the need for ever-smaller
beams of extremely high brilliance This trend towards nano-sized beams constitutes
the logical evolution of a trend which has been evident from the early days of ESRF
operation. In the ESRF Foundation Phase Report (Red Book) it was expected that a
“micro-focusing beamline” could deliver a beam size of ~30 µm and that most
beamlines would operate with a beam of about 1 mm dimension. Today, the limiting
capability of the “micro-focusing” beamlines is to deliver X-ray beams of less than
100 nanometre, but this performance remains far from routine. A “standard” beamline
operates routinely with sub-millimetre beams. The pressure from scientists and users
to have routine beams of 10 µm or less (down to 1 µm) is enormous. The reasons for
this are multiple and reflect many facets of the scientific case outlined in Section 2.
For example they are needed:
• to study small crystals of all materials, protein crystals, novel materials, nanostructures,
quantum confined structures;
• to investigate efficiently samples in extreme and exotic thermodynamic
conditions; pressures up to 3 Mbar; temperatures up to 5000 K and down to the
sub-Kelvin region; magnetic fields up to 50 Tesla; combinations of such
conditions;
• to develop advanced techniques, such as coherent X-ray scattering and
spectroscopy and, more generally, to combine imaging techniques with X-ray
scattering and absorption techniques to develop new X-ray methodologies.
Recent work performed by teams of ESRF scientists and external collaborators has
demonstrated a world leading performance in focussing X-ray beams of about 20
keV to less than 50 nm, using either a dynamically bent graded multilayer device or
an assembly of compound refractive lenses. In order to implement efficient focusing
options in the sub-micron region on generic beamlines providing stability and
compatibility with sophisticated sample environment equipment, it is necessary to
construct optical devices capable of very large source demagnification, in the range 1
in 1000 to 1 in 10,000. These requirements pose a number of new challenges. Not
only the optical quality of reflecting and refracting devices must be outstanding, but
also the temperature and vibration stability of the experimental environment must
satisfy extremely demanding criteria.
The “long” beamlines to enable these demagnification ratios need to be sensibly
longer than a typical ESRF beamline, which is ~ 50 m, extendable to a maximum
length of 70 m. In fact, with a 1:1000 demagnification at 50 m from the source, only
50 mm would be available between the centre of the optical device to the focal spot.
This could be increased to a much more comfortable value of 120 mm if the beamline
length could be extended to 120 m. The possibility to have a secondary source can
be a key parameter for the improvement of the stability and the overall control of the
critical parts of an experiment using very small beams. This option, if implemented
efficiently, also requires a beamline at least twice as long as that typically possible
today. Already, as part of the ESRF’s Medium Term Scientific Plan, two pilot nano-
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