ORIG. RUSSIAN: CONTROLLED NUCLEAR FUSION AND HIGH-TEMPERATURE PLASMA PHYSICS RESEARCH IN USSR

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP88-00904R000100100006-4
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 25
• Document Creation Date: December 22, 2016
• Document Release Date: August 12, 2009
• Sequence Number: 6
• Publication Date: May 1, 1964
• Content Type: STUDY

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Third United Nations
International Conference
on the Peaceful Uses
of Atomic Energy
A/CONF. 28/P/297
USSR
May 1964
Originals RUSSIAN
Confidential until official release during Conference
CONTROLLED NUCLEAR FUSION AND HIGH-TEMPERATURE
PLASMA PHYSICS RESEARCH IN USSR
L.A. Artsimovich
? 1. The final goal of controlled nuclear fusion re-
search is the development of methods permitting deuterium
and tritium be used as new nuclear fuels for energy pro-
duction. Exceedingly high temperatures are the necessary
conditions that intensive fusion reactions in deuterium
or its mixture with tritium take place. The temperature
required should be of an order of hundreds millions degrees.
In this region of temperatures the nuclear fuel is fully
ionized plasma. Besides very high temperatures a plasma
must also be of a concentration high enough as the reaction
yield is proportional to the square of concentration.
As far back as the idea of the controlled nuclear fu-
sion arose it became clear that the main task to be solved
is to provide a very perfect thermal insulation of the nuc-
lear fuel. High vacuum is the only medium that the hot
plasma can be in contact without instantaneous losing the
heat energy accumulated in it. To insulate, however, a
bunch of hot plasma in vacuum the plasma pressure must be
counterbalanced by some equilibrium force on its boundary.
Such a force can be produced by a magnetic field if the
magnetic lines of force of that field surround the plasma
region. The magnetic field serves here as an elastic sheat
of which the pressure balances the kinetic gas pressure of
the plasma -tending to expand.
It should be remarked, however, that the magnetic
thermal insulation is far from perfect and the energy leaks
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outward even through a very strong magnetic field. A pos-
sible measure of the thermal insulation quality is the
time while a temperature of the plasma in a magnetic field
remains sufficiently high. To find a characteristic time
7 the total thermal energy of all the particles available
in plasma should be divided by the energy flux transf'ered
by fast neutrals escaping from the plasma per unit time.
The parameter `L can be also considered as a mean lifetime,,
of a fast particle in plasma. It is obvious that a thermo-
nuclear reactor of net energy gain is possible to con-
struct only after some method has been found to cofine
fast particles in plasma for a sufficient period of time.
All the rather long history of the controlled nuclear re-
search is in fact a struggle for a longer r .
Research on controlled nuclear fusion has been going on
in different countries far about fifteen years. Some results
obtained in controlled nuclear fusion research were for the
first time presented for the international scientific
forum at the Second United Nations Conference on the Peace-
ful Uses of A tomic Energy in 1958.
The initial stage of tl'e research falling on the years
when the work was carried out in different countries in-
dependently from one another was reviewed there. A consi-
derable predominance of theoretical analysis over experimen-
tal investigations was characteristic for that time. The
status of experimental research did not correspond that
time to the complicity of the tasl:. During the years fol-
lowing the conference when a number of great difficulties
was everywhere encountered in practice it was gradually
understood that the experimental technics must be improved
far more. It also became clear that technical aspects of
the problems associated with controlledi nuclear fusion are
possible to discuss only if an experimental foundation is
layed down far the high temperature: plasma physics.
The present paper is a review of the recent develop-
ment of the high temperature plasma physics research in
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the USSR. These cover a large number of various approaches.
Of them the major ones are:
1. Investigation of plasma properties in what is cal-
led open magnetic traps, i.e, magnetic systems where plasma
Is confined in the region with a magnetic field with un-
closed lines of force. 2. Studies of heating a plasma by a
current passing through it in toroidal systems with a very
strong stabilizing magnetic field, 3. Studies of the plasma
behaviour in strong high-frequency electromagnetic fields
(plasma confinement and heating).
? 2. Let us see first the investigations on plasma
properties in magnetic traps with open ends. The plasma
confinement in such systems is based on one law of the
motion of charged particles in a magnetic field. A particle
that moves along a line of force towards the region of the
increasing magnetic field undergoes slowing-down. If the
angle between the direction of its velocity and the line of
force is rather large the particle approaching the region
of a stronger field will experience a reflection as if from
a mirror, If therefore the magnetic field strength inc-
reased in both directions from some central region the
plasma particles could be confined inside a limited space
between the "magnetic mirrors 110 The simpliest magnetic
system of the type under question is a conventional trap
with two magnetic mirrors shown schematically in Fig.l.
The magnetic field cf that configuration could be produced
by two coils in which the currents would be in the same di-
rection. Note that in the trap with two mirrors a field
strength H increases with the distance from the centre along
the lines of force but also decreases in radial directions.
If the direction of the current would change in one of
the coils it would resemble a magnetic trap with magnetic
fields opposing each other given in Fig.2. The magnetic
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field strength in such a trap increases with the distance
from the central region in all directions. At some point
of this region HI drops down to zero. A great interest has
lately been payed to magnetic traps with more complex
field geometries ("hybride type" fields). These magnetic
systems will be discussed below.
First the attention of experimenters was mostly payed
to the simpllest type of traps with two magnetic mirrors.
The first experimental device with magnetic mirrors was
put into action at the Kurchatov Atomic Energy Institute
(AEI) in Moscow in 1957. A plasma at high ion tempera-
ture was built up in this device by the method of "ion
magnetron", i.e the ions were extracted from a cold plasma
are produced along the axis of the magnetic system aryl ac-
celerated by applying a short high-voltage pulse.
After applying the voltage the plasma arc sprays and
the space between the magnetic mirrors would thus be
filled with a high temperature plasma of a concentration=
109 - 1010cm 3. The net energy of plasma ions after swit-
ching off the high voltage makes 1.5 - 2 kev that cor-
responds to a temperature of the order of 2.10701. The
main aim of experiments have been carried out for a number
of years with the device which has been called the "ion
magnetron" (IM) was to study the properties of a plasma
captured in a magnetic field after witching off the high
voltage. First of all it wary needed plat a containment
time of the created plasma bunch, i.e. a lifetime 4 of
fast, ions in the trap be determined. To do it one should
measure how a plasma concentration (i.e. a number of fast
ions per cubic centimeter) varies in time. The scope of
the present paper do not permit ue to discuss here the
technique of these measurements and we shall therefore
report the experimental results only.
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The treatment of the experimental data collected in
three year work with IM enabled to make a basic conclu-
sion as follows: a plasma bunch having an initial concen-
tration of particles from 108 to M1010 and an ave-
rage ion energy of approximately 1.5 kev is unstable and
decays during the time not longer that several hundred
microseconds. Instability indications are clearly seen
in oscillograms obtained with the help of diagnostic
equipment used for measuring plasma parameters. The osci-
lloscope traces are traversed with numerous high fre-
quency oscillations.
These results were the first concincing confirmation
for theoretical predictions on plasma instability in
fields of this geometry characteristic of simple traps
with magnetic mirrors. The theoretical analysis has shown
that due to the decrease of the magnetic field atrengthu along
the radius a number of deformations having a shape of
repeated peaks and wells on the surface cf the plasma bunch
may appear and develop. Such a wrinkled structure has
been called a "flute deformation" and the reason causing
it has been called a convective instability. It is the
convective instability that took place in the experiments
done with the IM device. It follows in particular from
the analysis of observed plasma density fluctuations.
In 1958 when the experiments with IM were at an ear-
ly stage the construction of a large device with magnetic
mirrors was completed in the Kurchatov Atomic Energy
Institute. This device called "Ogra" is intended for
studying a possibility of producing a high temperature
plasma by injecting fast ions from outside. The fast mole-
cular ions of hydrogen injected into a trap are dissociat-
ed by collisions with residual gas atoms or with particles
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of a cold plasma produced within the trap volume. The dis-
sociation results in production of protons that in the
magnetic field follow a curved path having half the radius
of curvature of the molecular ion path. This irrever-
sible change of the trajectory leads to trapping atomic
ions between two magnetic mirrors. At an initial stage of
experiments carried out with OGRA the eimplieet method of
building up protons having an energy of 80 kev by the dis-
sociation of ions H2 on residual gas was studied. The
concentration of fast ions built up in a chamber depended
on the intensity of a current injected as well as a num-
ber of other factors but it remained very low at all
times. With the injector being on it usually made 107cm3
(in a volume of about 10 m3).
After the efficiency of the initial method for
building up a plasma was found inadequate it has been de-
cided to try a dissociation of molecular ions in passing
through a dense arc discharge (this method was formerly
applied with DCX in the USA). A method far producing
an intense lithium arc has been developed in the Scien-
tific and Research Vacuum Institute. A long arc dischare
column of a fully ionized cold plasma having a concentra-
tion of 3.1012cm 3 is established in vacuum along the
lines of force through all the length of the magnetic
trap. The ionized column may serve a ^ an effective means
for dissociating a beam of hydrogen ions passing through
it. The experiments on building up fast protons with the
use of the lithium arc in OGRA were initiated in 1963.
Correlating to initial assumptions the dissociation ef-
ficiency was found high enough. The method made possible
the average concentration of protons in OGRA to increase
up to 5.108 cm-3. It has also been discovered that the
dense lithium are column piercing a hydrogen plasma acts
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as a factor stabilizing plasma instabilities. Until the
lithium are operates the oscillations characteristic of a
flute instability development do not appear in the plasma.
The lifetime of protons extends up to 15 milliseconds. A
perspective of employing this phenomenon in practice to
stabilize "thermonuclear" plasma instabilities appears
doubtful for a dence column of lithium are if present in a
hot plasma would absorb the thermal energy of fast partic-
les. On the other hand, however, the stabilizing effect
of the arc column on a surrounding rarefied plasma with
fast ions has a certain heuristic value as an indication
that the search for new methods of suppressing plasma in-
stabilities in the simpliest systems with magnetic mirrors
is not hopeless.
? 3-The negative results of experiments aimed at pro-
ducing a high temperature plasma having high density in the
mirror machines have convinced a number of Soviet physi-
cists as far back as in 1960 that the task can be solved
quicker if using magnetic systems with fields of different
geometry where the main obstacle, i.e. the convective type
instability can be eliminated. The simpliest magnetic
system that should theoretically satisfy the above require-
ment is a system with opposing fields shown in Fig.2 with
lines of force of a hyperbolic shape. In a field of
this geometry a field strength H increases in all direc-
tions from the middle region. In accordance; with the basic
principles of the theory one may therefore. expect a plasma
trapped within the region of a weak field between the coils
be stable at least with respect to flute deformations. The
theory unfortunately predicts another substantial defect
for systems with opposing fields. A high density plasma
trapped in such a system should entirely push the magnetic
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field aside from the region surrounding the point in the
space where an initial value H is equal to zero. However,
the plasma cannot be confined in the region of zero field
for a long time as charged particles would leave that
region of space after several reflections from its bounda-
ries. It seems, therefore, difficult to hope the magnetic
trap of this class be suitable for confining a high tempe-
rature dense plasma for a long time.
It is long before that the point of view has been ex-
pressed in the USSR that a sufficient thermal insulation
can be provided for a high temperature.- plasma only im sys-
tems with hybrids magnetic fields comprizing the proper-
ties of the simple systems given in Fig.l and 2 but having
no their basic drawbacks. In such magnetic systems the
magnetic field strength should increase in all directions
outside from the plasma boundaries. However a field strength
H should not drop to zero in the region filled with the
plasma. One of the natural ways of realizing a magnetic
system satisfying both of the above conditions and ensur-
ing therefore a priori a plasma stability is schematically
presented in Fig.3. The magnetic field is produced by
coils and rectilinear current-carrying conductors disposed
symmetrically around the common axis of the coils. The
coils form a conventional field with two magnetic: mirrors
along the axis. A current being opiiosit in each two neigh-
boring rectilinear conductors produces a magnetic field
of which the configuration is given in Fig-4. The super-
position of the both magnetic fields leads to the increase
of a resultant vector i in all directions from the middle
region to be filled with a plasma. The experiments with
such a hybride magnetic configuration were performed for
the first time in the Kurchatov Atomic Energy Institute in
1961, where the device IM with 6 longitudinal current-
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on neutral atoms. The stated data indicate that under the
conditions in question plasma remains in a stable equili-
brium-state. The same has been proved by the shape of os-
cilloscope traces displaying a variation in plasma para-
meters. There is no high frequency oscillations on the one-
cilloscope traces. The significance of these experiments
lies in the fact that the possibility of a prolonged stable
confinement of such a plasma (with fast ions) in a magne-
tic field has been proved for the first time during all
the history of studying high temperature plasmas, The ex-
tension of the obtained information over the region of
higher concentrations naturally constitutes the greatest
interest. In accordance with the theoretical predictions
a new type of instability may occur at higher concentra-
tions due to growing of plasma oscillations at frequencies
close to the ion gyrofrequency in a magnetic field. To
check up if the instability exists the concentration should
be increased at least by a factor of 10, i.e. up to
1010- 1011 cm 3. We have already got the results of experi-
ments carried out with the device PR-5 in this direction.
For a new series of measurements another method different
from that mentioned above was used to fill a trap. An
original electrostatic instability that may occur in a
bunch of cold plasma is in use for the new method. At
some parameters c,f the discharge that creates a column
passing along the axis of the magnetic system the high
frequency electric fields appear in the discharge and
accelerate ions. The average ion energy is 1-2 kev. In
experiments on building up a high temperature plasma from
an unstable plasma column the average concentration of par-
ticles could be brought up to ti 3.1010cm-3: This con-
centration is about an order of magnitude higher than that
could be usually obtained by the magnetron method of
building plasma up. It has been shown from the experiments
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that at the mentioned concentration the instability indi-
cations are absent as formally although we remark that the
plasma decay followed by a flux of a neutral charge-exchange
particles is not any more exponentional in time.
Another device with a hybride field was decided to con-
struct to expand the utilization of the possibilities of
these fields. A plasma was assumed to build up in the de-
vice by ionizing a beam of fast atoms injected from out-
side. This device, named OGRA-II, repeats the configura-
tion of the magnetic field in PR-5, but exceeds it consi-
derably in size and in H. A strength of the field produced
by the coils in the middle part of the trap can be brought
up to 15,000 gauss at the field strength in the mirror re-
gion of 23,000 gauss. The inner diameter of the vacuum
chamber is 70 cm. The construction of OGRA-II was completed
in may 1964, its picture is given in Fig.7.
? 4. Investigation of the ohmic heating of plasma in
quazistationary discharges provided a plasma circular
column is in a strong longitudinal magnetic field repre-
sents a traditional trend in the Kurchatov Atomic Energy
Institute. The strength of the longitudinal magnetic field
stabilizing the- plasma column is many times higher than that
produced by the plasma current. That is the principle
difference between the experiments described and the expe-
riments implemented with the use of devices analogous to
the known device "ZETA". With the devices of the "TOKAIA
family ( see Fig.8) experiments have already been carried
out for a number of years. The toroidal chamber with a
plasma column created inside it is put on the core of an
iron transformer. The plasma current is initiated under the
influence of a voltage induced in the chamber. To provide
for better vacuum the chamber is made two-sheathed. The
inside chamber (liner) is made of thin stainless steel.
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A diaphragm limiting the plasma column cross section is
fitted inside the liner so that to reduce interaction
between the plasma and the liner surface. The liner is
isolated from the outside sheath made of thick, copper
that serves for maintaining the circular plasma current
column in equilibrium state by means of eddy currents.
A whole family of TOKAMAKS has been so far constructed;
of this family of devices the largest one T-3 is presented
in Fig.9; it was put into operation in 1962.
The theoretical analysis of the plasma column be-
haviour indicates that it may undergo a rough instability.
This instability occurs if the self-magnetic field of the
current to the longitudinal stabilizing field ratio is
wrong. To get
strength H to
should exceed
R is the ring
section.
a stable plasma the longitudinal field
a self-magnetic field of the current ratio
the ratio at least several times, where
radius, r is the radius of the column cross
At the early
stage of experiments with the first mo-
dels of the TOKAMAK devices the longitudinal field
strength did not exceed several thousand gauss; to pro-
vide therefore for that stability we had to limit strong-
ly the plasma current. Due to that the amount of energy
released in the discharge was also limited and it was im-
possible to heat the plasma up to h:i;:;.u?r temperatures.
However, even at a high Ho we could not first get smooth
oscilloscope traces and observed a fast decay of particle
concentration during the discharge. They tried to attri-
bute it to uncertain instability mechanisms that caused
a very fast "anomalous" diffusion of plasma across magne-
tic lines of force. This point of view predominated
until it was found that the phenomenon ascribed to the
"anomalous" diffusion could be explained as a motion of the
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plasma loop inside the chamber due to the disturbance of
its equilibrium state. Small displacements of the loop
effect strongly the plasma properties because of its inter-
action with the diaphragm. The plasma turn may move inside
the vacuum chamber under the influence of different cau-
ses. Even a very small component of the external magnetic
field perpendicular to the direction of the plasma current
may displace the turn for a noticeable distance. A change
in plasma pressure due to heating and current redistribu-
tion over the plasma loop cross section may be other cau-
ses of plasma motion. A vigorous effect of small displace.
ments of the plasma ring on the discharge process has been
proved experimentally. That is why a special correction
for a magnetic field is in use to compensate the influence
of factors affecting the plasma equilibrium conditions.
It led to a considerable change in the process picture. The
conditions of the,. discharge obtained with the T-3 device are
characteristic of a long confinement time and a high con-
ductivity of plasma (see Fig.10 with some results of the
measurements). The plasma conductivity increases with the
increase of H0. It 'Teaches 3.1016 CGSE at Ho= 25,000 gauss
and a plasma concentration n -1013cm 3. It corresponds to a
plasma electron temperature of about 2.106og. Note that in
such a way they have obtained a plasma loop with a con-
ductivity like that with a metal. Under such conditions
of the discharge the oscilloscope traces become smooth and
the measurements do not reveal a fast decay of n till the
plasma current remains high. So it can be concluded that
in circular systems with a strong field the plasma heating
can be performed together with maintaining its stability.
? 5. A significant place in investigations on high
temperature plasma physics in the USSR has been occupied
by research devoted to studying interaction between plas-
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mas and high-frequency fields. The following are the two
main purposes in the research: a/ to clear up if the plasma
can be confined and stabilized with the help of high-
frequency fields; b/ to develop methods of fast heating a
plasma. The development of various means of confining and
stabilizing plasmas with the help of high-frequency fields
is carried on in the Kurchatov Atomic Energy Institute and
in Radiotechnical Institute in Moscow, in Scientific and
Research Institute far Electrical and Physical Apparatus in
Leningrad and in Physical and Technical Institute in. Sukhumi.
Experimental research on methods far producing high tempe-
rature! plasma where the main function of confinement is
laid upon high-frequency fields have, not yet. brought posi-
tive results. Studying of combined systems advanced far
more. In combined systems an insulated plasma formation is
maintained at equilibrium state by means of stationary and
slowly changing magnetic fields and high-frequency fields
serve as a stabilizing factor. The method cf high-frequen-
cy stabilization of a plasma column with a high longitudinal
current is studied in the Kurchat ov Atomic Energy Institute.
A stabilising arrangement is a system of rods placed sym-
metrically around the discharge chamber and in. parallels
with the plasma column (Fig.ll). Currents produced by a
high-frequency generator flow through the each two rods in
opposite directions and thanks to that the high-frequency
fields are induced. At high enough amplitude and frequency
the fields can provide the plasma column stability with
respect to the most dangerous kink deformations. Experi-
ments prove the existence of the stabilizing effect.
The method of plasma dynamic stabilization is studied
in Sukhumi. In this case the stabilizing system consists
also of rods placed symmetrically relative to the axis of
the magnetic trap. A high-frequency current passes through
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them and produces a rotating magnetic field. Besides, di-
rect currents flowing through the each two rods in opposi-
te directions produce a stationary field of a geometry
analogous to that of the rotating one. The combined effect
of the high-frequency and the stationary fields is equiva-
lent to the effect of two fields rotating in opposite direc-
tions. As follows from experiments the development of flute
deformations characteristic of traps with magnetic mirrors
is suppressed in this system. However, it should be point-
ed out that in the experiments carried out so far the plasma
temperature was very low. It is therefore difficult to
evaluate the perspectives of using the described method for
the high frequency stabilization (it also concerns experi-
ments studying the effect of high frequency-fields on a
plasma column with current).
The affect of super nigh frequency of decimetric waves
electronagnetic fields on plasma is also being investigated.
The experiments with a super high-frequency field affecting
plasma in a stationary longitudinal magnetic field have
been carried out in the Kurchatov Atomic Energy Institute.
The super high frequency field produced an additional
radial pressure. In such a system a convective instability
of plasma may appear to be suppressed (or to be strongly
attenuated).
? 6. Methods of high frequency heating a plasma are
rapidly developed in the Soviet Union. A number of fruit-
ful theoretical ideas have recently been suggested in this
field. They have successfully being realized in practice.
Different resonance phenomena resulting in particle acce-
leration ban be used for heating a plasma. For example,
an alternating electromagnetic field of a rather small
amplitude and a frequency close to the angular velocity of
rotation (larmor frequency) of ions affects a plasma in
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a strong stationary magnetic field, then a resonance ac-
celeration may occur. This is what we call a cyclotron
resonance method that may be used for heating the ion
component of the plasma. The above mentioned method is
being developed in Physical and Technical Institute in
Kharkov for a number of years. The results obtained thus
far should be recognized promising. The ion component
of the plasma enclosed in a mirror machine was heated by
the cyclotron resonance up to the temperature of 15 mil-
lion degrees with the use of high frequency generators
of a comparatively low power. The concentration of the
plasma then made 12.1013cm 3
A new trend in plasma heating methods have lately
arisen in the USSR. It proceeds in general from the idea
that in a plasma any ordered motion of high enough inten-
sity is not stable and should dissipate into small-scale
oscillations that convert quickly its energy into the
energy of thermal motion. Theoretical research carried
out in the Kurchatov Atomic Energy Institute and the Novo-
sibirsk Nuclear Physics Institute have defined this gene-
ral idea more concretely that resulted in a new method
suggested for heating plasma by a steep front pulse of
high-frequency field. If a short high-frequency pulse
with amplitude H1~H0 where H 0 is a uniform stationary
(or slowly changing) field inside a cylindrical chamber
affects a cold plasma bunch a strong shock wave develops
and propagates in the plasma radially inward. to the axis
(the both fields are parallel to one another). The jump
in the magnetic field strength of this wave is caused by
the fact that there appears an azimuthal electron current.
At a very fast rate of rise of the alternating field the
kinetic energy of the directional azimuthal motion of
electrons reaches a great value. This motion is not stable
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and its energy should therefore convert into the thermal
energy of the plasma electron component. The new method
of heating a plasma by pulse high-frequency fields is named
"turbulent" heating. Experimental studies of the method are
developed at the Kurchatov Atomic Energy Institute and
Nuclear Physics Institute in Novosibirsk. In the experi-
ments being carried out at the Kurchatov Atomic Energy
Institute the alternative field of the frequency of about
10 MHz is produced by discharging a condenser bank of a
very low self-inductance across a one-turn coil wrapped
around a chamber filled preliminary with a cold plasma.
A stationary field strength Ho makes 500 to 2 or 3
thousand gauss. Duration of a fast-damping pulse of the
high-frequency fields makes several tenths of a micro-
second,
Experiments show that an alternative field pulse
sharply increases the energy of plasma electrons. At a
concentration of about 1012cm-3 the average energy of
plasma electrons is brought up to 1000-1500 ev in some
microseconds after the alternative field damped completely.
If the strength of the main field does not remain cons-
tant and increases then after a high-frequency pulse the
plasma undergoes compression and the energy of electrons
increases again. This is the way how the plasma with an
electron temperature of about 108 degrees and a concent-
ration of 1013cm-3 can be produced. A method for pro-
ducing pulse fields of an even higher rate of rise and a
higher amplitude has been developed in Novosibirsk. It
has enabled to realize the turbulent heating of the plasma
ion component. The ion energy brought up was -.,10 kev.
Thus judging from the results obtained on the first stage
of developing the method of turbulent heating is very pro-
mising.
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? 7. Besides the basic trends mentioned above wide-
scale experiments are being carried out in the Soviet
Union in a number of other branches of the high temperature
plasma physics. The present paper cannot describe the pur-
poses and the results of these numerous investigations and
we have to limit ourselves to irrelevant problems only.
Research on plasma injectors, on interaction between plasma
jets and magnetic fields as well as on methods of inject-
ing plasma into magnetic traps are developed in a wide
scale at Physical and Technical Institute in Kharkov, at
the Kurchatov Atomic Energy Institute and in Physical In-
stitute of the Academy of Sciences of the USSR. Investiga-
tion on powerful pulse discharges of a very short dura-
tion is going on at the Kurchatov Atomic Energy Institute,
at Physical and Technical Institute in Sukhumi and at the
Moscow State University of which the aim is to clear up
the cause of the appearence of fast particles in plasma
in such processes. The basic lows of plasma diffusion in
a magnetic field are studied at Physical and Technical
Institutes in Leningrad and Sukhumi and at Nuclear Physics
Institute in Novosibirsk. A relativistic plasma is stu-
died at Nuclear Physics Institute in Novosibirsk. Great
attention is also being payed to developing various ex-
perimental technics for measuring the main parameters
characteristic of plasma behaviour. The paper so far
spoke almost only about experimental studies. It does
not, however, mean that in the Soviet Union they do not
pay necessary attention to developing theoretical aspects
of the plasma physics. Our experimental program is in
fact mutually connected with the theory research. Theore-
tical investigations initiate the basic trends in expe-
riments. Any significant result obtained from experiments immedia-
tely becomes a subject of theoretical analysis. Theoretical
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research carried out in our country on the problem of sta-
bility has a great principle significance for the high tem-
perature plasma physics as a whole. A number of mechanisms
causing instabilities in nonhomogeneous plasma were for
the first time investigated in the Soviet Union. Since
plasma is always unstable near boundaries the above men-
tioned investigations have a direct practical significance.
Theoretical studies of processes occurring in turbulent
plasmas, i.e. in plasmas with a grown instability, have play-
ed an important role in developing physical notions of the
plasma properties. These studies enable to estimate a
possible rate, of diffusion and heat transfer in unstable
plasma. It is unfortunate that here we have to confine
ourselves to these general remarks since the purpose and
the size of the paper do not allow us to deep in the
plasma theory. In conclusion we must come back once again
to the problem of controlled fusion and to try to formu-
late in brief its present state and its probable future.
The development of this problem can be compared with
climbing up a stair with very high steps. The height of
each of them can be measured after have climbed it up. By
the time of the Second Geneva Conference we had a great
stock of ideas, but in practice we were able to produce a
plasma with temperatures of about one million degrees con-
fined for several seconds only. It was the first step of
the controlled fusion stair. The stable long-term confine-
ment of a plasma in hybride magnetic fields, the efficient
ohmic heating carried out in stabilized systems as well
as the successful development of the new method of the
plasma "turbulent" heating represent the second step. The
next (but not the last) one will be reached when a stable
high temperature plasma is produced with such a high den-
sity that it could serve as a powerful neutron source
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excelling accelerating devices in efficiency. The term
"controlled thermonuclear fusion" will actually acquire a
real meaning at that stage only.
We hope by the rourth Geneva Conference the climbing
up to the third step of the thermonuclear stair will be
completed.
CAPTIONS
Fig.1. Magnetic field geometry in the magnetic trap with
open ends.
Fig.2. Magnetic field geometry in the magnetic trap with
opposing rields.
L'ig.3 Disposition of the current-carrying conductors in
the trap with a hybride field geometry
Fig.4 Magnetic field geometry in the hybride magnetic trap
Fig-5 Oscilloscope traces of plasma decay in the PR-5
device. The top curve shows the case of having the
stabilizing field on; the bottom curve shows the
case of having the stabilizing field off.
Fig.6. Reverse lifetime of plasma as a function of neutral
hydrogen pressure:
1. The stablizing field being off
2. The stabilizing field being on
Fig. 7. General view of the OGRA-II device
Fig.8. Oscillogram of the loop voltage, of the plasma
current and of the microwave interferometer
signal (the TOKOMAK--3 device)
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Hai -
39000
~~ f
GY
y
L
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