Extended
research experience
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Position Sensitive Detectors
Enhancement of the MCP dynamic range. Evaluation of microchannel plate
characteristics at high count rates. Conductively cooled low resistance
microchannel plates: operation and modelling.
Limitations on input count rates are among the main disadvantages of position-sensitive
detectors based on microchannel plates. In many cases these limitations
are determined by the count rate capabilities of the MCPs themselves. Enhancement
of the MCP dynamic range is one of the main requirements in current detector
applications. Reducing plate resistance is one of the possible ways to
increase the count rate capability of microchannel plates. The negative
temperature coefficient of resistance of the MCP ultimately results in
thermal instability as plate resistance is reduced. The results of our
tests with low-resistance, conductively-cooled microchannel plates open
up the possibility of increasing the count rate capability of MCP detectors
by using plates with much lower than normal resistance. The developed thermal
model is in a good agreement with experimental data and it provides estimation
of the lowest initial MCP resistance for given MCP geometry and applied
bias.
Experimental evaluation and computer modelling of a new type of electron
multiplier - Microsphere Plates.
Microsphere plates, a new type of electron multiplier, consist of sintered
disks of glass beads. Our tests of microsphere plates, operating in both
single-plate mode and in a two-stage stack reveal that the characteristics
of such detectors are quite similar to those of (multistage) MCP detectors,
although there are some essential differences in operation. I also describe
a simple Monte-Carlo model of MSP operation, which enables us to estimate
numerically a number of MSP characteristics, including output pulse height
distributions, output electron spatial and energy distributions and transit
time distributions.
Design, assembly and calibration of the IMAGE (Imager for Magnetopause-to-Aurora
Global Exploration) Wideband Imaging Camera (WIC) and the Spectrographic
Imager (SI) NASA space flight detectors.
WIC is a curved image intensifier optically coupled to a CCD. The optics
provides a field of view of 17x17 degrees. The size of two final images
is 256x256 pixel elements. SI cross delay line detector contains stack
of 3 back-to-back MCPs with spatial resolution of ~25 microns.
Tests and calibration of the Far Ultraviolet Spectroscopic Explorer double
delay line large format MCP NASA space flight detector.
The flight detectors consist of 2 detector segments that make up the final
170mm long x 12mm high detector area. Each detector segment has a surface
curved to match the focal plane surface. The current mission baseline for
the FUV detectors is about 48,000 x 320 detector pixels, with a spatial
resolution of about 20µm FWHM, capable of handling event rates ~ 4 x 104
sec-1.
Simulation of position sensitive detector based on microchannel plates.
The model of position-sensitive detector comprising microchannel plates
proved to be a useful tool for optimization of detector parameters and
development and testing of fast algorithms for preliminary data processing.
In many applications the spatial resolution of the detector is one of the
most critical parameter. A number of different readout techniques have
been developed in order to achieve the best detector's position sensitivity.
Computational experiment on the base of mathematical model is an effective
tool for readout system investigation. Computer simulation revealed the
high spatial resolution of a new proposed "coded" readout system.
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Photocathodes
Synchrotron calibration of alkali halide coated microchannel plate detectors.
The soft X-ray quantum detection efficiency of a microchannel plate has
discontinuities in the energy response due to absorption edges of the atomic
constituents of the MCP lead silicate glass, its electrode material and
of any alkali halide deposition photocathode. In the case of spectrometer
readout, where X-ray wavelength is mapped into position space it is essential
to map the efficiency function very precisely in order to avoid near-edge
structure in the detector response being misinterpreted in terms of emission
or absorption features.
Photocathodes radiation resistivity and ageing. Computer simulation and
damage measurements using synchrotron source.
There has been a growing interest in photon detectors combining solid photocathodes
and electron multipliers. It was observed that the current yield of alkali
halide photocathodes decreases very rapidly when exposed to X-rays in the
0.1-3keV band. Doped CsI is commonly used as a scintillator in protein
crystallography measurements and there is a great interest in the effect
of radiation damage in these materials. Our measurements made at the Daresbury
Sinchrotron Radiation Source included studies of radiation damage in several
photocathode materials, such as CsI, CsI(Tl) Gadox, Y2O2S(Eu) and Y2O3(Eu).
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X-ray optics
Microchannel plate X-ray optics for X-ray astronomy and X-ray lithography.
Lightweight, low-cost microchannel plate X-ray optics has become available
recently. The possibility of producing microchannel plates slumped into
a spherical geometry provides a basis for an implementation of the so-called
lobster-eye telescope - an attractive option for an all-sky x-ray monitor
instrument. A wide-field X-ray telescope offers an order of magnitude increase
in sensitivity over previous, non-focusing, designs. The performance of
such optics is limited by the distortions in the MCP structure that occur
during the manufacturing process. A number of measurement techniques can
be used to qualify the structural imperfections in channel plates. The
disadvantage of previously used methods is their localized nature, therefore
a large number of data have to be analyzed in order to examine the whole
area of the channel plate with the required accuracy. We suggest another
simple method to evaluate the structural imperfections of the MCP over
a large area, in particular multifiber rotation, twist and long axis misalignment.
Profiled MCP's have proven to be effective soft X-ray collimators which
may be used in X-ray lithography and other applications. Two basic approaches
to X-ray lithography are distinguished currently by the X-ray source: synchrotron
and laser-plasma point source. The preferred X-ray source is the synchrotron,
which can provide a very intense almost parallel soft X-ray beam. However
the cost of these machines is huge. The inherently diverging beam from
the X-ray emitting plasma and smaller source strength are the main disadvantages
of the laser-plasma X-ray source. However, recent developments of collimator
optics provide the basis for their application in X-ray lithography.
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Experimental measurements of inter-molecular and inter-atom
potentials
Algorithm development for data processing in experiments with fast crossed
molecular beams. Experiment design, including determination of the limits
on the sensitivity of the instruments in order to resolve particular physical
parameters of the interactions. Calculating the apparatus functions and
solving incorrect inverse problems of experimental data interpretation.
Intermolecular and inter-atom potentials are the fundamental data necessary
for the mathematical modelling of many physical processes taking place
at high pressures and temperatures with the presence of fast chemical reactions.
One of the most promising techniques to measure these potentials for the
excited atoms and molecules is the method of fast crossed molecular beams.
It appeared that physical parameters of the interaction are not easily
obtained from the measured data and therefore new algorithms of data interpretation
had to be developed.
I also was involved in the design and testing of the experimental setup
and determination of the acceptable limits on the instrument sensitivities.
On the other hand, my project required the algorithm development for obtaining
physical parameters from the measured data. I also developed a computer
model of the entire experimental procedure in order to calculate the apparatus
function, which is used for improving data interpretation accuracy.
Computer simulation of the entire experiment, which takes into account
accuracy of all its devices, enables calculation of the apparatus function,
which is used for improving data interpretation accuracy.
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Parallel programming and teaching
Parallel programming and multiprocessor architecture in mathematical modelling
and experimental data processing (e.g. transputer-based networks).
Software interface for the transputer subsystem in the MS Windows
environment was designed. Power of parallel programming implemented in
the tranputer network and user friendly interface provide base for the
scientific work in the field of intensive computations.
Teaching and parallel computing.
I participated in teaching parallel programming on transputer-based
systems in experimental laboratories for students at Moscow Institute of
Physics and Technology (MIPT). My teaching experience also included teaching
basic physics and mathematics courses at the Physics and Mathematics school
affiliated with MIPT.
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Miscellaneous
"Cold fusion" computer simulation.
Interpretation of the cluster caused fusion experiments with
the help of molecular dynamics method implemented for heavy water molecules
clusters impact on deiterium doped titanium crystal lattice.
Real time experimental data processing and visualisation. Experiment automatization.
Software engineering.
I would like to mention also my experience in software engineering.
During my research work I have developed a large number of C, FORTRAN,
Assembler, SQL and Eiffel codes for both computer simulation of physical
phenomena and real-time experimental data acquisition and processing. Some
codes were implemented on a multiprocessor architecture substantially increasing
computational performance and enabling real-time experimental data interpretation.
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