Record of Proceedings of Session 4
Possibility of Controlled Fusion
TUESDAY AFTERNOON, 2 SEPTEMBER 1958
Chairman: Mr. H. J. Bhabha (India)
Scientific Secretaries: Messrs. H. Sethna and T. Coor
PROGRAMME
P/145
Magnetohydrodynamics and the thermonuclear problem
P/78
Controlled thermonuclear research in the United Kingdom
H. Alfvén
P. C. Thonemann
DISCUSSION
P/2298
Research on controlled thermonuclear reactions in the USSR
(Presented by Mr. E. I. Dobrokhotov)
P/2410
Peaceful uses of fusion
L. A. Artsimovich
E. Teller
DISCUSSION
P/1056
Recent work on controlled thermonuclear fusion in Germany (Federal
Republic)
,
L. Biermann
DISCUSSION
The CHAIRMAN : We come now to one of the sessions
which is going to raise the greatest interest. As all
of you who were at the 1955 Geneva Conference will
recall, there was no mention of fusion in that Conference
except for a very passing and brief remark which I
made in my presidential address. Since then a very
large amount of work has been declassified on this
subject and we all know that a tremendous amount of
work is going on in many countries. Briefly, the
work in this line takes two general directions: one
of accelerating plasma by electromagnetic forces; the
other of equilibrium containment, in which the pressure of the plasma is balanced by magnetic pressure.
As regards the first approach, it is very easy to see
the orders of magnitude. The time in which compression takes place is roughly the size of the vessel or
the distance which the plasma has to travel divided
by its velocity, and this is of the order of 10~~5 to
10~6 seconds. After that you have to do your best
to contain the plasma while it is hot and get all the
energy you can out of it.
As regards the second method there are two approaches. One is the approach of plasma containment and heating by closed discharge currents main-
tained through external electromagnetic forces. The
second one is what you might describe as a magnetic
trap in which the plasma is trapped and then heated
in some continuous way, as by injecting particles
into it.
In this connexion one might mention that as regards
the D-D reaction the temperatures to be achieved
are of the order of about 500 million volts, and for the
D-T reaction smaller by a factor of about 3.
The one other point I should like to mention is the
interesting question as to whether the fusion energy
can be turned directly into electrical energy, or
whether it must necessarily take its path through
heat. Here there is only one remark I should like to
make. In the course of fusion reactions a certain and
considerable amount of energy always escapes as
neutrons which are therefore lost from the direct
production of electricity. These neutrons, however,
are not entirely lost in the sense that one can think
of methods by which they might be utilized for
making some of the products that one wants. As I
have just mentioned, the D-T reaction is much more
favorable than the D-D reaction and one could
imagine that the neutrons might be used for producing
39
40
SESSION 4
tritium in some envelope of suitable material, like
lithium, which surrounds the reactor. However,
since the aim of fusion is really in the long run to
produce a virtually limitless source of energy, it is
clear that it would have to be based on the D-D
reaction rather than the D-T reaction, and for this
purpose one would naturally like not to base it on the
availability of such materials as tritium.
DISCUSSION OF P/145 AND P/78
There was no discussion of these papers.
DISCUSSION OF P/2298 AND P/2410
Mr. TELLER: I should be grateful, Mr. Dobrokhotov, if I could get information as to the status of the
machine which has been described to us and which,
I believe, is called the " Ogra " machine. In what
state of operation is it at the present time? What are
its stability properties? *
Mr. DOBROKHOTOV (USSR): The apparatus of
which I spoke, and which is displayed in the Scientific
Exhibition, was constructed very recently and the
experiments that will give the data asked for have not
been performed yet. The machine is operating and
data will soon be obtained.
Mr. HOY AUX (Belgium): Dr. Teller, can the
stabilized toroidal pinch of the Zeta type on the one
hand, and the toroidal stellarator with auxiliary
coils twisting the lines of force on the other hand, be
considered theoretically as one and the same apparatus, differing only in the relative amount of autoconfinement and external confinement?
Mr. TELLER: Thank you very much for the
question ; it gives me a chance to emphasize something
that I discussed briefly in my paper. The two machines
are not the same. The main differences are partly
the thing that is pointed out in the question : namely,
the predominance of the auto-confinement in the case
of the pinch, but the other part, which is connected
with it, is the following: the pinch is designed as a
pulsed machine which produces, nevertheless, a
considerable number of thermonuclear reactions
* Ed. Note: "Ogra" stands for ^rtsimovich-Golovin.
hopefully, because there is, due to the outer confinement, a great concentration of matter in the pinch;
and the rate at which a single deuteron reacts is proportional to the density of the other deuterons about
it. This compression is an advantage absent in the
stellarator. On the other hand, it has to be balanced
against the disadvantage that these high densities are
not maintained for a long time. It is in principle a
pulsed machine, whereas the stellarator in principle
is a stable machine—a steady machine in which the
steadiness does not last forever. If we could make it
last for a second we would be happy; that is what we
are shooting for. But we are not shooting for making
the pinch last a second, so there are various directions
in which these various machines are looking.
Mr. SPITZER (USA): I should like to ask Dr.
Dobrokhotov, what is the status in the USSR of
experimental and theoretical confinement in magnetic
traps with the figure-8 geometry?
Mr. DOBROKHOTOV (USSR): These theoretical
proposals have been studied only qualitatively. We
have not yet set up an actual trap with this geometry.
Mr. SINGWI (India) : I have a question for Professor Teller on his remarks about the diagnostic
importance of the "noble" neutrons. Could I ask
whether any experiments have been done regarding
the anisotropic distribution of these neutrons?
Mr. TELLER: The answer is yes. I think you will
find details in our papers and also in the description
of the exhibits. There have been investigations in
every case. Various cases have shown great anisotropies. Such great anisotropies, for instance, have been
found in the pinch but not in the mirror machine,
which did produce neutrons—not in the steady state
but when you apparently collapsed it. This is the
machine called Scylla. In this machine there is also
a trace of anisotropy but it is an anisotropy which is
quite small, so that in this case we seem to be getting
closer to the point where we might hope to call these
things mostly thermonuclear and where there might
therefore be a diagnostic value, but I should not like
to make any claim.
DISCUSSION OF P/1056
There was no discussion of this paper.