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The study of GRB prompt emission (PE) is one of the main goals of the Lomonosov
space mission, which is being prepared at Moscow State University. The GRB
monitor (BDRG) and the wide-field optical cameras (SHOK) are intended for detection of GRB
prompt emission as well as optical counterparts. The BDRG instrument consists of three
identical NaI(Tl)/CsI(Tl) (13.0 × 2.0cm ) phoswich detectors, whose axes determine the
Cartesian coordinate system. This allows to localize any GRB source on the sky by means of
the count rate seen by each detector with an accuracy of ~2 deg. The SHOK
instrument consists of two identical wide-field cameras (WFC) directed in such a way that
the field of view (FOV) of each WFC overlaps by the corresponding BDRG FOV, which produces
a trigger on the WFC in case of a GRB detection. With this setup, the GRB prompt light
curve will be obtained in the visible without any delay with respect to gamma-rays, which
is crucial for a GRB central engine understanding.
The number of experiments on-board Lomonosov spacecraft are preparing now at SINP MSU in
co-operation with other organisations. The main idea of Lomonosov mission is to study
extreme astrophysical phenomena, such as cosmic gamma-ray bursts and ultra-high energy
cosmic rays. These phenomena connect with processes occurred in very distant astrophysical
objects of the Early Universe and give us information about first stages of Universe
evolution. Thus, the Lomonosov mission scientific equipment includes several instruments
for gamma-ray burst observation in optics, ultra-violet, X-rays and gamma-rays and the
wide aperture telescope for ultra-high energy particle study by detection of ionisation
light along its tracks in the atmosphere. The main parameters and a brief description of
these instruments are presented.
The experiments to study the indirect drive targets'
dynamics in a highly symmetrical X-radiation field were
performed on the ISKRA-5 facility. This paper covered the
results of experiments with the targets in the form of
a Cu spherical hohlraum, the internal surface of which
is coated with Au, with six holes for laser radiation input.
In the center of the aforementioned hohlraum, a glass capsule
filled with D–T gas was placed. In several experiments,
the central capsule was coated with an ablator made of
plastic with a different thickness. This allowed us to
perform a series of experiments in which the different
compression degree of D–T fuel was achieved. The
analyses of experimental results revealed good agreement
between the latter and the spherically symmetrical hydrodynamic
The investigations of the influence of various
types of wavefront distortions, varying in time, on the
intensity distribution on the surface of a target are carried
out. It is shown that distortions of a wavefront, equivalent
to transverse displacement in time of a beam in far field
at an angle of approximately 10 diffraction angles, results
in practically full smoothing of a specl-structure of intensity
distribution. Creation of phase distortions of a beam assigned
as running in a cross section wave with an amplitude of
more than 3 radian and with a spatial size exceeding 20–30
times the size of the kinoform phase plate element, permits
us to reduce the depth of modulation in distribution of
intensity in far field also. The capability of application
is considered as a smoothing device of the dynamic plasma
layer, based on the volume-structured medium. The model
of energy transport process in such media is developed.
Matching of calculation and experimental results is conducted.
Two shells with the diameter of 0.8–0.9 mm
and a wall thickness of ≅1 μm were produced at
the Lebedev Physics Institute for the experiments conducted
at the ISKRA-5 facility. The results of two experiments
with the aforementioned shells conducted at the ISKRA-5
facility with the use of an indirect-drive set up. In one
of the experiments, the diameter of the golden hohlraum
was D = 2 mm while in the other it was D =
4 mm. In these experiments it was observed to be ≅4
times the difference of the average laser intensity on the
hohlraum surface. The results of computational analysis of the
experiments are also presented here.
The first experiments to study the shell's
controlled asymmetry of capsule with DT-fuel in a highly
symmetrical X-ray field, which is obtained inside a spherical
hohlraum, were implemented. The asymmetry results from
the coating of one hemisphere with the additional layer
of material. The main goal of the experiment was to define
the value of the capsule asymmetry, allowing us to experimentally
obtain the neutron yield, which would be very different
from the yield obtained in the experiment with the spherically
symmetrical shell having the same mass as the asymmetrical
one. It was shown that the shell asymmetry of ∼50%
leads to the ∼(2–4) times reduction of the neutron
yield as compared with the symmetrical shell. 2D calculations
of the asymmetric capsule compression, using the MIMOZA-ND
code, were conducted. The calculations demonstrated that
the compression of targets, when exploding pusher regime
occurs has a complicated character. The computational neutron
yield, and the delay of the neutron generation time are
in good agreement with the experimental data.
The experiments measuring the density of DT mixture
compressed in indirect drive targets (X-ray targets) were
conducted on the ISKRA-5 facility. The density was determined
from the line broadening of H- and He-like Ar doped in
DT-gas as a diagnostic substance. A series of three experiments
with the X-ray targets having different shell thickness
of capsule filled with DT + Ar mixture were carried out.
In two of the three experiments, radiation spectra of Ar
were recorded and the density of compressed gas was determined.
The analysis of the experimental results for the X-ray
target with a 280-μm diameter and a 7 μm wall thickness
revealed that the density of the compressed gas may be
estimated as ∼1 g/cm3.
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