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Dear McStas users,<br>
<br>
please find below two 6 month work placements (training for
students) and a PhD offer, funded for 3 years in Paris in
collaboration with the ILL, and as a continuation of one of the 2
work placements.<br>
<br>
Spread the word around you !<br>
<br>
Emmanuel.<br>
<br>
<div class="csc-header csc-header-n16">
<h4>work placement: Neutron coherent scattering study of liquid
hydrogen. Increase of thermal neutron cross sections accuracy -
réf. 15/CS-1</h4>
</div>
(ILL Science Division / Scientific Computing group)<br>
<br>
DNA investigations, smart materials understanding, solar cells
optimization, global warming studies, water treatment solutions,
drugs structural elucidation, all of these fields that recently
underwent breakthroughs have in common the use of neutron scattering
at the ILL. Indeed, when neutron beams are used to probe small
samples of materials they have the power to reveal what cannot be
seen using other types of radiation. Neutron diffraction (as well as
X-ray diffraction) is a standard method to study the crystal
structure of a solid, and more generally, to get insight about the
structure of a material. Every type of materials can be investigated
with this technique, ranging from crystals to liquids as well as
disordered polymers and colloids in solution. <br>
<br>
Hydrogen-based (H2, D2) neutron moderators are used to produce cold
neutrons which feed many neutron scattering experiments. This is the
reason why neutron production facilities need to get the highest
available level of accuracy for neutron cross-section data in such
materials. Modelling accurately such neutron sources is crucial for
their refurbishment or merely for safety considerations.
Furthermore, recent investments of the European Community addressed
to the general amendment of the poor accuracy of existing nuclear
databases, also regarded cryogenic liquids.<br>
<br>
This internship will thus be dedicated to a neutron inelastic
scattering experiment carried out on liquid hydrogen and the
treatment and analysis of the recorded data. Such measurements are
particularly challenging because of the experimental conditions and
because of the high level of accuracy required. The teachings will
be shared by scientists from the ILL and from the University of
Florence (Italy). Furthermore, the internship is part of the
NAUSICAA project (<a href="https://www.ill.eu/?id=15488"
target="_top">https://www.ill.eu/?id=15488</a>) which has just
been launched and takes part of an international collaboration,
under the auspices of the OECD/NEA.<br>
<br>
Duration: 5 months maximum <br>
Level: 5th year university studies in physics, chemistry or biology<br>
Supervisor: E. Farhi <a
href="javascript:linkTo_UnCryptMailto('hvdgoj5avmcdVdgg9am');">farhi(at)ill.fr</a>
and Y. Calzavara <a
href="javascript:linkTo_UnCryptMailto('hvdgoj5xvguvqvmvVdgg9am');">calzavara(at)ill.fr</a><br>
<br>
<div class="csc-header csc-header-n17">
<h4>work placement: Light and heavy water thermal cross sections
for neutron transport codes, up to 350C and 150 bar - réf.
15/BPC_1</h4>
</div>
<p class="bodytext">(ILL Projects and Techniques Division)<br>
<br>
DNA investigations, smart materials understanding, solar cells
optimization, global warming studies, water treatment solutions,
drugs structural elucidation, all of these fields that recently
underwent breakthroughs have in common the use of neutron
scattering at the ILL. Indeed, when neutron beams are used to
probe small samples of materials they have the power to reveal
what cannot be seen using other types of radiation. Neutron
diffraction (as well as X-ray diffraction) is a standard method to
study the crystal structure of a solid, and more generally, to get
insight about the structure of a material. Every type of materials
can be investigated with this technique, ranging from crystals to
liquids as well as disordered polymers and colloids in solution.
As matter is never completely disordered, these techniques yield
correlation distances exhibited by the sample when it is
disordered, and diffraction peaks corresponding to a particular
crystal structure when it is crystalline. Moreover, an energy
analysis provides information about the internal motions. <br>
<br>
Water is a major component of the nuclear facilities, including
research reactors, spallations sources and power plants. In these
facilities, water acts both as a coolant and a neutron moderator
(to slow down neutron emitted at very high energy). The resulting
neutrons, labelled as 'thermal', are used to probe matter in
neutron scattering instruments, to extract structural and
dynamical information. This is the reason why neutron production
facilities absolutely need to get the highest available level of
accuracy for neutron cross-section data. Moreover, modelling such
neutron sources is crucial for their refurbishment or merely for
safety considerations. Last, recent investments of the European
Community addressed to the general amendment of the poor accuracy
of existing nuclear databases, including common liquids.<br>
<br>
The neutron cross-section data can be obtained from e.g. neutron
scattering experiments, and from molecular dynamics simulations.
The neutron scattering experiments will be performed at the ILL,
on time-of-flight spectrometers, which will directly provide
structural and dynamic properties of water. As the measurement
range is finite, we plan to extend the determination of these
properties using molecular dynamics simulations, with codes such
as NAMD. This study will consider both light (H2O) and heavy (D2O)
water, from normal conditions up to T=350 oC and P=150 bar. Last,
the data sets must be combined and treated to extract the dynamic
structure factor <<a
href="http://en.wikipedia.org/wiki/Dynamic_structure_factor"
target="_top">http://en.wikipedia.org/wiki/Dynamic_structure_factor</a>>
(see also Ashcroft and Mermin, Solid State Physics, Appendix N)
and compute the neutron scattering cross-sections.<br>
<br>
This internship sits within this ambitious task. The internship is
part of the international NAUSICAA collaboration <<a
href="https://www.ill.eu/?id=15488" target="_top">https://www.ill.eu/?id=15488</a>>
which has just been launched, under the auspices of the OECD/NEA.
A six months' research activity is appropriate for the performance
and analysis of the measurements, and for learning and practising
with available calculation tools. The teaching will be shared by
scientists from the ILL, with collaborations in Italy, Germany and
Canada. In this project we shall use the IN4 and IN5
spectrometers, the iFit and LAMP data treatment software, the NAMD
and nMoldyn molecular dynamics simulation codes, and the McStas
neutron ray-tracing simulation package. <br>
<br>
Duration: 6 months maximum<br>
Level: 5 th year university studies in physics<br>
Supervisors : E. Farhi, e-mail :farhi@ill.fr and Y. Calzavara,
e-mail : <a class="moz-txt-link-abbreviated" href="mailto:calzavara@ill.fr">calzavara@ill.fr</a><br>
</p>
<p class="bodytext"><br>
</p>
<h4 class="bodytext">PhD: Experimental
and Theoretical Studies of Light Water Effective Thermal
Scattering
Kernel</h4>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><font
color="#365f91"><u><b>Job
Description</b></u></font></p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify">Neutronic
calculations
of nuclear reactor core in operation in France are based
on two major essential principles, namely, the use of computer
codes
to model and solve the neutron transport equation and the
underlying
nuclear data describing the neutron interaction with the reactor
material components. The past 30 years have seen an overwhelming
improvement in the methodologies used for reactor calculations
leading to significant reduction in the reactor uncertainty
results.
However, nuclear data libraries have not yet achieved the level of
self-assurance needed for reactor applications and consequently
there
are still needs for improvements of nuclear data and their
uncertainties.</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify">Neutron
slowing
down and thermalization by water are very important for
pressurized water reactors (PWR) core calculations. A good
knowledge
of nuclear data and uncertainties for these processes are required
to
address the uncertainty in the system multiplication factors.
Although progress has been reached for improving nuclear data
evaluation for fission, capture, and elastic cross sections very
little has been done for double-differential neutron scattering
cross
sections in the energy region where the incident neutron energies
are
comparable to the molecular energy. The proposed thesis consists
of
performing nuclear data measurements of light water thermal
scattering cross section corresponding to conditions of a PWR
operation, i.e., high-temperature, high-pressure, etc. The
measurements will be performed at the Lau Langevin Institute (ILL)
located in Grenoble using the thermal neutron time-of-flight (TOF)
spectrometer IN4 and the cold neutron multi-chopper TOF
spectrometer
IN5. Subsequently the measured data will be analyzed and evaluated
using molecular dynamics technique to extract the
double-differential
cross section and the scattering Kernel S(a,b). The evaluation of
the
experimental data will provide the grounds to obtain the
uncertainties associated with the experimental conditions in
connection with the measurements, namely, the systematic and the
statistical uncertainties. While existing nuclear data libraries
contain S(a,b) evaluation for water for certain reactor
operational
condition it should be noted that no uncertainty information
exists
based on actual experimental data. The results of the proposed
work
will improve calculation of PWR effective multiplication factor
and
will provide a better understanding of its uncertainties. </p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><a
name="_GoBack"></a>
<font color="#365f91"><u><b>Candidate Profiled</b></u></font></p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify">Applicants
are
expected to be familiar with the nuclear physics dealing with
thermal neutron scattering. In addition, familiarization with
experimental techniques used for nuclear data measurements is
needed.
In particular some knowledge of the technique commonly used in
molecular dynamic application will be of extreme value for the
success of the work. Familiarization with format of the nuclear
data
library and processing codes used to process the library are
deemed
needed.</p>
<p style="margin-bottom: 0cm; line-height: 100%" align="justify">Duration:
3 years (Paris IRSN, CEA/Saclay and ILL)<br>
Contact: E. Farhi, e-mail :farhi@ill.fr and Y. Calzavara, e-mail :
<a class="moz-txt-link-abbreviated" href="mailto:calzavara@ill.fr">calzavara@ill.fr</a></p>
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<pre class="moz-signature" cols="72">--
Emmanuel FARHI,<a class="moz-txt-link-abbreviated" href="http://www.ill.eu/computing/people/emmanuel-farhi">www.ill.eu/computing/people/emmanuel-farhi</a> \|/ ____ \|/
CS-Group ILL4/221, Institut Laue-Langevin (ILL) Grenoble ~@-/ oO \-@~
71 av des Martyrs,CS 20156,38042 Grenoble Cedex 9,France /_( \__/ )_\
Work :Tel (33/0) 4 76 20 71 35. Fax (33/0) 4 76 48 39 06 \__U_/
</pre>
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