Seminars Archive
Development of XRF instrumentation based on Silicon Drift Detectors and Development of a Fast Readout CCD system to be used as a
Abstract
Friday, December 17, 2004, 15:30
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
Development of XRF instrumentation based on Silicon
Drift Detectors and Development of a Fast Readout CCD system to be used
as a Configurable Detector in Scanning Transmission X-ray Microscopy (STXM)
Alessandra Gianoncelli
(King’s College London, UK)
Abstract
The seminar will talk about the activity developed during the PhD at
the Electronics Department of the Politecnico di Milano (Milano, Italy)
and the current research at the Physics Department of the King’s College,
University of London (London, UK).
A part of my PhD activity was the development of an innovative XRF
instrumentation based on a new kind of detector: a ring-shaped monolithic
array of 12 Silicon Drift Detectors. As an excitation source, an X-ray
tube with policapillary lenses was used. The radiation is directed on the
sample through the central hole done on the detector chip: this configuration
allows to collect a big solid angle of the XRF radiation emitted by the
sample.
Thanks to the high spatial and energy resolution, this instrument is
especially suitable for elemental mapping and microanalysis of materials.
A first experiment of elemental mapping will be shown during the talk.
Moreover several XRF analyses, both qualitative and quantitative, were
carried out on different kinds of samples (works of art, metallic samples...)
by using a portable and compact instrument based on a single Silicon Drift
Detector. Some of the results of these analyses will be presented during
the seminar.
The current activity is part of the EC RT&D project "Twinmic" (HPRI-2001-RTD-50024).
King’s College is involved in the development of a fast Readout CCD system
to be used as a configurable detector in the Scanning Transmission Mode
of the Microscope. The system is based around a fast-readout electron-multiplying
CCD (EMCCD) camera from Andor Technology. The detector has 128_128 pixels
and it can be read out at more than 110 frames per second. The CCD is a
back-face imaging device, thermoelectrically-cooled, with high sensitivity
and low noise performance. It is not used in direct x-ray detection mode,
to avoid the possibility of radiation damage to the detector. Instead a
visible-light coupling system is currently in development, which allows
also the x-ray pattern on a phosphor screen to be matched to the active
area of the CCD. By using a CCD detector, a full frame is collected from
every pixel in the raster scan of the scanning microscope. In this way
it is possible to use a flexible range of configurable detector response
functions and produce different imaging modes of the sample (brightfield,
darkfield, absorption and phase contrast methods). In principle, the phase
contrast method also allows quantitative measurements of the complex refractive
index, and some examples of the analysis required to achieve this are presented.