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The construction of the Terawatt Accumulator (TWAC) facility
is nearly completed at the ITEP in Moscow. All the major milestones
have been successfully passed with a beam of carbon ions, except
for the final result (the high power beam accumulation), which
is on the way. The beam of C4+ ions delivered by
the laser ion source is accelerated up to the energy of 300
MeV/amu by two steps—in the linear injector I3 and
in the booster synchrotron UK. The accelerated beam is extracted
from the UK ring and transferred to the U10 accumulator ring.
Non-Liouvillian stripping technique (C4+ ⇒
C6+) is applied for stacking of C6+ batches
into the accumulator ring U10. First experiments with extracted
beam of ions have started in 2002. Status of the TWAC components,
current results of activities aiming at mastering the ion beam
stacking technique, and outlook for the TWAC advance are presented.
Review of some research into laser thermonuclear fusion
carried out in Russian Federal Nuclear Center (RFNC-VNIIEF)
within the last several years is presented. The review
begins with a brief survey into ICF development in RFNC-VNIIEF
starting from A.D. Sakharov and S.B. Kormer's pioneer
proposals of the 1960s. The review concludes with the exposition
of historical background of the 10 TW ISKRA-4 and 100 TW
ISKRA-5 laser facilities creation and with the prospects
of the 300 kJ ISKRA-6 (λ= 0.35 μm) laser
development. The results of survey carried out at the ISKRA-5
facility are presented in the review. The high degree of symmetry
(nonuniformity < 3%) of irradiation of a DT-shell by the X-ray
emission made it possible to successfully conduct experiments
with the asymmetrical shells. The asymmetry was effected through
the asymmetrical Mg layers deposition on a spherically uniform
glass shell surface. The asymmetry impact on neutron yield and
the moment of neutron generation was investigated. The line
X-ray emission characteristics of the H-like and He-like
Ar, Fe, and Al ions were studied in another set of experiments.
Ar was doped into DT-gas, while Fe and Al were deposited
on the CH spherical hohlraums' inner surface. Development
of the Cherenkov radiation generator in which the electron
motion is actuated by the faster-than-light X-ray pulse
motion on the surface of a plane sample, being under voltage,
is reported. And in fine a brief description of experiments
carried out at the ISKRA-4 facility under the program of
turbulent mixing in plane multi layer targets is presented.
This paper is devoted to the investigation of powerful
laser pulse interaction with regularly and statistically
volume-structured media with near critical average density
and properties of laser-produced plasma of such a media.
The results of the latest experiments on laser pulse interaction
with plane foam targets performed on Nd-laser facilities
“ABC” in the ENEA-EURATOM Association (Frascati,
Italy) and “MISHEN” in the Troitsk Institute
of Innovation Thermonuclear Investigations (TRINITI, Troitsk
Russia), and J-laser “ISKRA-4” in the Russian
Federal Nuclear Center, All-Russian Scientific Research
Institute of Experimental Physics (RFNC-VNIIEF, Sarov,
Russia) are presented and analyzed. High efficiency of
the internal volume absorption of laser radiation in the
foams of supercritical density was observed, and the dynamics
of absorbing region formation and velocity of energy transfer
process versus the parameters of porous matter
are found. Some inertial confinement fusion (ICF) applications
based on nonequilibrium properties of laser-produced plasma
of a foam and regularly structured media such as the powerful
neutron source with yield of 109–1011
DT-neutrons per 1 J of laser energy, laser-produced X-ray
generation in high temperature supercritical plasma, and
the compact ICF target absorbers providing effective smoothing
and ablation are proposed.
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
We present the results of the experimental testing of the
laser facility LAMBDA, created and built at the Institute
of Experimental Physics of the Russian Federal Nuclear
Center for generation of quasi-steady-state laser fields
The facility includes: a single mode generator of reference
radiation (RR) producing about 10 mJ energy in a pulse
of controlled length from 3 to 30 ns; a target chamber
with an input objective focusing the RR beam to a micron-size
spot, and a 280-mm-diameter parabolic mirror with the focal
length also of 270 mm; a two-stage iodine amplifier with
the small signal gain coefficient 3·105
per one pass, to the input of which radiation from the
target chamber formed by the (microobjective + parabolic
mirror) system is applied; a phase conjugating device with
the system for the selection of the phase-conjugated component,
which allows us to realize the pulse compression in the
amplifier stages, and to provide the compensation of the
optical aberrations after the second pass amplification
and focusing of high-power radiation into the microvolume;
a complex for diagnostics of plasma and laser radiation
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.
Since 1973, research into the problem of laser
thermonuclear fusion has been carried out at VNIIEF. For
this purpose, laser iodine facilities ISKRA-4 and ISKRA-5
with the peak radiation power up to 100 TW have been created.
In the present work, the main stages of these facilities
creation, approaches to the selection of the pumping sources,
working media, optical scheme, radiation focusing system,
the system of the pumping sources energy feed, laser radiation,
and plasma parameters diagnostics methods are shown. There
are also presented types of the targets, filled with DT-gas,
in which the high temperature plasma is formed and its
parameters are studied. Data on values of neutron yield,
of X rays in wide energy range, degree of implosion, and
data on mix of heavy and light layers of matter are presented
The interaction of a plasma produced by irradiation of perforated foils with laser pulses was studied. The laser beam of the first harmonics of the iodine laser (λ = 1.315 μm) system PERUN was focused by anf/2 optics (f = 20 cm) on a hole in the foil target of high-Z material. The laser energy and the temporal shape of the pulses were monitored both before and behind the hole. Foils of two different materials (Pb, Cu) were used, and a series of hole diameters 2rH ranging from 100 μm to 500 μm were tested. The diameter of the laser focal spot 2r0 was about 150 μm. For hole diameters smaller than 300 μm, a shortening of the laser pulse was observed, demonstrating the effect of plasma shutter. The pulse shortening, which depends on the hole diameter, corresponds to the reduction in the pulse energy passing through the hole. An analysis of the experimental data is based on hydrodynamic computations, and the physics of the process is illustrated by a simple analytical model.
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