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Патент USA US3093775

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June 11, 1963
F. PREvoT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
Filed’ March 22, 1960
6 Sheets-Sheet 1
FIG.‘
I
A
21
22
June 11, 1963
>
F. PREVOT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
Filed March 22, 1960
G Sheets-Sheet 2
F[6.2
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20
25
24
23
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20
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23
24
24
June 11, 1963
FfPREvoT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
Filed March 22, 1960
FIG.3
38
34
.35
36
37
6 Sheets-Sheet 3
F164
June 11, I963
F. PREVOT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
6 Sheets-Sheet 4
Filad larch 22, 1960
FIG.6
F16.7
43
4/
45
June 11, 1963
F. PREVOT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
Filed March 22, 1960
6 Sheets-Sheet 5
FIG.9
June 11, 1963
F. PREVOT
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR PLASMA APPARATUS
Filed March 22, 1960
6 Sheets-Sheet 6_
FIG. 70
United States Patent 0
3,093,765
Patented June 11, 1963
1
'
2
3,093,765
ION INJECTION DEVICE FOR THERMONUCLEAR
sariat a l’Energie Atomique, Paris, France
along a circumference and alternating with insulators sup
porting the ion source.
A second embodiment of the simple acceleration elec
Filed Mar. 22, 1960, Ser. No. 16,830
Claims priority, applicationpFrance Apr. 20, 1959
means for the high tension insulators or their internal
‘
'
PLASMA APPARATUS
.
Francois‘Prévot, Antony, France, assignor to Commis
' ‘
ring and being supported at the interior of the casing
of the apparatus by high tension insulators distributed
‘
trode type, by the use of appropriate position-regulating
12 Claims. (Cl. 313-63) 7
elements, changes the form of the injected ion sheet,
' ‘The present invention relates to apparatus used for
which can either be located in a plane normal to the
axis of symmetry of the apparatus or in a cone of revolu
forming a plasma, i.e_., an ionized medium, wherein
thermonuclear, fusion reactions take place. It pertains
more‘pa‘rticularly to devices for the injection of fast ions
tion having an axis coinciding with the said axis of sym
metry and having an adjustable apex angle. This ar
rangement multiplies the passages of a given particle
in “such apparatus for the formation of a high tempera
along the axis.
;
ture and high density plasma, con?ned in a magnetic 15 A third embodiment is characterized in that the ac
?eld.
celeration electrode, housed within a circular insulator
In a certain known apparatus (such as apparatus DC-X
containing the ion source, is of the gradient type, which
at Oak Ridge, Tennessee, USA.) the ionized particles,
permits the use of injection tensions and acceleration
accelerated vby appropriate means, are injected in the
‘ ?elds greater than in the ?rst embodiments.
plasma formation zone shaped as a linear beam of mo
Whichever embodiment is being considered, the device
lecular ions, the molecular ions being dissociated into
of the invention is characterized in that the beam of
atomic, ions by an electric arc and then captured in the
injected ions has a form of a Sheet, plane or conical.
magnetic ?eld of con?nement crossed by the arc. Such
This beam therefore has a high intensity which leads to
an ‘apparatus has shortcomings which are essentially due
the formation of high density plasma. The intrinsic
to the method of injecting the ions.
25 very high intensity of the beam ensures on the other hand
The particles being injected in the form of a linear
beam, the intensity of that beam is limited by the ion
source, the ?ow and e?iciency in molecular ions of the
source being limited. The intensity is also limited by
the‘ spacial charging which has a tendency to expand the
beam, and by the requirement that the path be well de
?ned. It follows from ,thisjlimitation in intensity that
the plasma thus obtained is of low density. On the other
hand, the presence of a critical intensity in the injected
ion current, which intensity‘is a function of the energy
of these ions and below which the apparatus will not
operateyrequires the use of a high energy value thus
involving technological dif?culties of construction which
do not ‘improve the formation of the plasma.
that the operating condition of the apparatus mentioned
above, namely the necessity that the injection intensity
be higher than a critical intensity, is satisfactory. This
enlarges considerably the choice of the energy of the
30 ion and permits in particular, to use the most favourable
value for the desired temperature.
The device of the invention offers other advantages.
It does away for instance, with the necessity of stabilizing
the acceleration tension and the magnetic ?eld due to the
fact that, by virtue of its symmetry, it has a focusing
property independent of the energy of the ions, starting
with a certain value.
It leads to a high energy ef?ciency
cessitating an expensive ‘control system. Finally, et?
resulting, on the one hand, from the ions having several
passages in the magnetic ?eld and, on the other hand,
from the increase in dissociation efficiency in a single
passage; the particles being capable of dissociation among.
themselves on account of their higher density and the
ciency remains low due to the fact that the ions which
isotropy of the velocities. Finally, the possible weaken
were not captured in the plasma formation zone are lost
ing of the injection energy and the symmetry of the de
vice, in consequence of which the paths of the particles
It is, also necessary in an apparatus of this type, to‘
have a ‘well de?ned accelerating tension of the ions, ne
after only‘one passage through said zone and, further
more, the thermalization, i.e., the creation of a plasma
by‘ dissociation and capture of ionized particles, is ren
dered more dif?cult by the high energy combined with
the low intensity of the beam and its unidirectional
characteristic. It is well to note also the possibility of
instability due to the anisotropy of the ion velocities.
The instant invention therefore proposes a device for
injec‘ting'and capturing ionized particles within a mag
netic ?eld, to obtain a high temperature plasma which
obviates these various inconveniences while being simple
in‘manufa‘cture and safe in operation
1Tln's device for injecting and capturing ionized par
ticles is essentially characterized in that it comprises an
annular ion source combined with an annular accelera
tion electrode coaxial to said source and creating a sheet
like ‘ion beam; the con?nement magnetic ?eld of axial
symmetry being coaxial‘ with the ion source and the
all have one common point at the center, render the
heating of the ‘beam more rapid and e?icient and can
remove the instability mentioned above.
Other characteristics and advantages of the invention
will appear in the following description having reference
to the attached drawings wherein:
FIG. 1 shows schematically, in axial vertical section,
an apparatus provided with an injection device of the
invention;
FIG. 2 is a out along line A-A of FIG. 1;
FIG. 3 schematically shows a path of a particle pro
jected against the plane containing the axis of revolution
X—X of the apparatus;
FIG. 4 shows a projection of the path of FIG. 3 on
a plane normal to axis X—X;
FIG. 5 schematically shows the successive paths of
one particle making several passages on the axis;
electrode.
FIG. 6 shows one type of variable tension applied to
‘ In one embodiment of the invention, the acceleration
the ion source capable of de?ning the movement shown
electrode is simple, roughly having the form of a split 65 on FIG. 5;
3,093,765
3
4
FIG. 7 shows a method of attachment of the insulator
supports;
.
FIG. 8 shows an arrangement of the coils creating the
con?nement magnetic ?eld in the case of a conical ion
beam;
FIG. 9 shows another possible arrangement of the
con?nement coils;
in the vicinity of coils 5 and 6 in a pattern similar to that
shown by the two lines of force 30‘ and 31. The ferro
magnetic frame 26 prevents scattering of the lines of
force, all of which must close within the ion source, it
being necessary that the total magnetic flux embraced by
the annular ion source be zero.
A circular slit 32 (FIG. 1) in the plane ‘of symmetry
FIG. 10 shows, in axial vertical section, an apparatus
of the apparatus allows entry of the ion beam into the
provided with another embodiment of the device of the
enlarged portion 4 of chamber 2. An acceleration elec
invention.
10 trode 33 is supported by the ferromagnetic frame 26 and
It can be seen, on FIG. 1, shown schematically in ‘axial
at the same potential thereof, that is, the potential of the
vertical section, an apparatus used for the creation of a
mass.
plasma, provided with the injection device which is the
object of the present invention.
Vacuum providing components 14, 15, 16 and 17 per
mit the maintenance of a vacuum in the order of 10*5
This apparatus comprises, in known fashion, a cy 15 mm. of mercury at the interior of the casing 1 and in the
lindrical ?uid proof casing 1 of axis X—X, containing
order of 10-8 mm. in the chamber 2.
a chamber 2 de?ned by a housing 3 of heat resistant stain
The arrangement of the con?nement coils gives to the
less steel. The enlarged central section 4 of chamber 2
magnetic ?eld in the area of injection, an axial symmetry;
constitutes the plasma formation zone. The con?nement
an essential characteristic of the device of the invention.
magnetic ?eld is created by two magnetic coils 5 and 6, 20 Outside the injection area, the magnetic ?eld may have
respectively located on either side of enlarged part 4, co
any shape, provided that this does not modify the con
axially of chamber 2. The coils are cooled by ?uid
ditions indicated above ‘with regard to the injection Zone.
?owing in tubes 7, 8, 9 and 10'. Two electrodes 11 and 12
The annular source 18 ejects molecular ions, which
are used to create a dissociation arc in the plasma forma
are accelerated by the electric ?eld maintained between
tion zone.
the source and the injection Zone by the circular elec
Housing 3 is surrounded by a cooling coil (normal
trodes, such as 19 and 33. Any charged particle, the path
operation) or a heating coil 13 (during gas removal).
of which, outside the magnetic ?eld, is contained in a
Vacuum is produced in the casing 1 by means of two
meridian plane containing the axis of symmetry X—X,
identical groups each comprising a mechanical pump :14
passes by this axis if it achieves a minimum energy con—
and‘ a diffusion pump 15 associated with a liquid nitrogen 30 dition. FIGURE 3 schematically shows the pattern of
trap, having a condensation screen and a valve. The
the con?nement magnetic ?eld outlined by the lines of
primary vacuum thus produced in the casing 1 is in the
force 34, 35, 36 and 37, in a plane containing the axis
order of 10*5 mm. of Hg. Similarly, chamber 2 is placed
of revolution X—X, and a path of particle 38 entering
under vacuum by means of two identical groups, each
the ?eld in a certain meridian plane and moving out of
having a mechanical pump 16 and a diffusion pump 17 35 the ?eld in a different meridian plane. FIG. 4 shows this
associated with a liquid nitrogen trap, having a condensing
trajectory projected on a plane normal to» axis X—X.
screen and a valve. It is thus possible to produce in
The circumferences shown in dashed line de?ne the mag
chamber 2, a secondary vacuum in the order of 10‘-8
netic ?eld Zones in one direction and in the other, the
mm. of Hg.
circumference shown in dotted line represents the trajec
In ‘accordance with the invention, the ion injection 40 tory of the captured particle if it is dissociated on the
device used in the apparatus has an annular shape. It
axis.
is essentially composed of a circular source of ions 18
' All the particles, the trajectories of which lie outside
and a middle electrode 19, also circular, both of which
the magnetic ?eld ofmconfinement and generate a cone
are centered on axis X—X of the apparatus. The rela
tive arrangement of these components is best seen on
FIG. 2, which is a sectional view along line A-—A of
FIG. 1. The ion source 18 is of any adequate type giving
ions which may be molecular. It has the approximate
shape of an annular channel, the opening of which,
formed as a circular slit, is turned toward the axis of the
apparatus.
High tension insulators are evenly distributed around
' the cylindrical wall of easing 1 with their axis located in,
the plane of symmetry of the apparatus normal to- the
coaxial to magnetic ?eld, will effectively pass by the
axis. The trajectories may, particularly, be perpendicular
to the axis and consequently contained in a plane perpen
dicular to the axis. This is accomplished by the device
of FIGS. 1 and 2, where the particles emitted by source
18 have trajectories contained in a plane perpendicular to
the axis X——-X, the ion beam having the form of a plane
sheet. The molecular ions emitted by source .18 are
dissociated on the axis, for example, by means of a
carbon arc, a hydrogen arc, etc. The atomic ions thus
‘formed have a mass twice as small and consequently a
axis X—X. Half the insulators, identi?ed at 20‘ on FIG.; 55 radius of gyration twice as small in-the ?eld of con?ne
2, are ‘used to support and feed the ion ‘annular source.
ment where they are con?ned if the initial energy of the
To this end, they are crossed by two conductors 21 and
dissociated ions coincide with a condition of maximum
22. The other, half of the insulators identi?ed at 23,
value. (‘Maximum energy=four times minimum energy).
serve to support and to feed the middle circular electrode
Apart from itsrcircular shape, the ion source may be of
19.
The conductor supports 24 crossing the insulators
23 are adequately spaced around the ion source 18 to
prevent any electrical contact with electrode 19. The
insulators are of any adequate type that will ensure satis
factory insulation at the level of easing 1.
provided with a protection electrode 25.
They are
'
This'method of attachment and feeding of the ion.
any appropriate type whatever, high frequency source, arc
source, etc. The embodiment shown in FIGS. 1 and 2 is '
suitable because of the arrangement of the high tension
insulation for relatively moderate tensions, ‘for example,
up to 200 kv.
It is not necessary that the acceleration
65 tensions be subjected to regulation since all the trajec
tories pass by the axis of symmetry, independently of the
energy of the particles.
it is possible, within the spirit of the invention, to con
If an ion is ‘not dissociated, it moves out ‘of the mag
sider other appropriate alternatives, as, for example, using
netic ?eld and returns to the source, where it may leave
a different number and type of insulators.
70 again, following a second trajectory similar to the ?rst one
The con?nement coils 5 and 6 (FIG. 1) are partially’
and consequently, pass again on the axis where it is'
surrounded by a ferromagnetic frame 26, cut off in the
afforded another chance to dissociate. It may also be lost
plane of symmetry of the apparatus to form a clearance
in the source. In order to avoid this second possibility
'27 between the polar extensions 28 and 25?. This frame
and obtain several passages on the axis, several. various
26 is intended to concentrate the lines of magnetic force 75 arrangements may be considered.
source and of the middle electrode is not restrictive and»
33093365
6
the apparatus. This arrangement permits the use of higher
tension than in the ?rst embodiment greater than 200
‘ i, It is possible, for instance, by holding ‘an ion beam in
the form of a plane sheet normal to the axis of symmetry,
to produce a, rapid increase of the tension at the source.
kv.
This ‘way the non-dissociated particle turns back before
bodiment of FIG. 1 and the elements have been identi?ed
by the same reference numeral.
In certain embodiments of the invention, the dissocia
tion arc can be removed, due to the fact that the plasma
which is obtained and which is of high density, will itself
cause dissociation of the particles reaching its sphere of
action.
Finally, the invention overcomes the inconvenience
of lost particles by exchange of load lead-ing to a neutrali
zation of ions, which causes heating and super?cial evapo
rization of the enclosing walls with generation of gas
and various impurities. In the embodiment of the in
vention, the neutralized particles are in 1a greater part in
the injection plane, in the case of the injection in plane
sheet, and because of this move out of zone 4, or plasma
formation zone. ‘On the other hand, the electric ?eld
due to the spacial loading of the injected beam modi?es
the movement in prior known devices, whereas, axial
tocal-ization is not changed in the case of the present in
vention.
It will be understood that the invention is not limited
to the embodiments described and shown which were
given only as examples and to which numerous changes
may be made without departing from the spirit of the in
vention.
The embodiments of the invent-ion in which an exclusive
property or privilege is claimed are de?ned as follows:
1. Ion injection device for thermonuclear plasma ap
‘ reaching and hitting the source. The successive trajec
tories obtained thereafter have the form shown on FIG
URE‘ 5 where 18 is theinterior limit of the source. A
simple method to achieve I; this result, without excessively
complicating the installation while varying the tension
‘ tatlthe‘souroe, consistsin. giving to this tension a saw tooth 10
r‘ shape, as is represented on FIGURE 6, where tension
is shown as a function of; time.
.
Another solution consists in injecting the ions in ac
cordance with trajectories. which are not normal to the
axis of ‘symmetry X—X. Thebeam of ions in this case 15
has‘the form of a sheet forming a cone of revolution of
axis X—X and of halfapex angle a. The movement of
thejfions in the con?nement ?eld there-fore has a com_
ponent parallel to the axis X~—-X: injected in a zone where
the central ?ux is weaker, the particles, under the drive of 20
' thiscomponent, enter a zone of stronger ?ux where they
remain for a certain time. The zones of weak magnetic
?ux are created by modifying the layout, the number or
the supply to the con?nement coils.
It‘ is possible to obtain an ion beam of conical shape 25
by‘ using an embodiment of j the invention wherein the in
The apparatus has the same elements as in the em
sulators 20 and 23, or only their internal elements re
spectively support the ion source and the middle electrode,
may be displaced parallel to the axis X—X to occupy
positions o?-set in relation to the plane of symmetry nor 30
mal‘ to the axis. In this embodiment of the invention,
thewsetting of the insulators may be made as indicated in
paratus including an enclosure under vacuum, an annular
FIG. 7. Opening 39 of easing 1, which, ‘for example,
source of ions, an annular accelerating elect-rode for said
‘receives an insulator 20, ‘is provided with a ?ange 40
ions, production and con?nement means for the plasma,
apertured with elongated anchorage holes 41. The body 35 means for dissociation of molecular ions centered on the
. of the insulator, the base of‘ which is schematically shown,
axis of said source, said electrode being coaxial with said
‘also has .a ?ange 42, ,apertured with holes 43. Bolts 44
source and creating with said source anion beam in sheet
hold the two ?anges in ?xed relation to one another and
form, said means including annular electric coils creating
compress a sealing ring 45 therebetween. The elongated
a con?nement magnetic ?eld of axial symmetrical and
holes ‘.41 allow for a relative displacement of the ?anges 40 coaxial with said ion source and said acceleration elec
40 and 42 and consequently allow change of the position
trode, a ferromagnetic frame surrounding said con?ne
‘of the‘insulators such as 20 and‘ 23. For greater accuracy,
ment coils and an annular air gap in said frame for the
passage of the ion beam.
it?is possible to use a :nut ‘and bolt arrangement of the
micrometer type with the‘j‘nut ‘integral with ?ange 40 and
ajscrew, the longitudinal, displacementsjof which being
‘communicated to ?ange 42 and to the base of the insula
tor.
t»
>
‘ Naturally, the invention also includes the case of an ion
injection ‘device, including fastening‘ elements, insulators
, for ‘instance, for the source‘ and the middle electrode
fastened on the casing in .a‘position corresponding to the
formation of a beam in the‘ form a conical sheet.
In a case where the ion beam has a conical shape, the
, zones of strong and weak‘ magnetic ?ux may be obtained
2. A device as described in claim 1 including high ten
45 sion insulators spaced on the periphery of said enclosure
supporting said acceleration electrode within said en
closure and‘insulators supporting said ion source alternat
ing with said ?rst insulators.
3. A device as described in claim 1 including an an
nular insulator ?xed to the periphery of said enclosure
and means \for mounting said acceleration electrode in
said insulator, said annular ion source being mounted in
said insulator away from said enclosure.
4. A device as described in claim 2 wherein said insu
in two different ways. It is‘pos‘sible to obtain a deviation 55 lators being displaceable parallel to the axis of symmetry
of ‘the ‘magnetic lines of‘ torce by means of magnetic
of said ion source whereby said ion source can create
shunts whereby par-t of the lines of force close in around
selectively a beam in a plane normal to the axis and a
“the‘coils 5 and 6 without going from one to the other, as
shown on FIG. 8. Themagnetic ?ux is then more in
‘ tense in zoneA than in zone B. On the other hand, it is
possible to increase the number of‘coils as. shown in FIG.
.9,‘ and reversethe ?ow of current, for example, in coils
46fand ‘47. The lines of force distribute themselves then
i‘ as ‘indicated, which will again give a weaker ?ux in in
beam in form of a conical sheet.
5. A device as described in claim 4 wherein said insu
lators are located in an ionic plane sheet.
6. A device as described in claim 4 wherein said in
sulators are located in a conical sheet.
7. A device as described in claim 1 including at least
least two of said electric coils creating the con?nement
65 magnetic ?eld, said coils being fed in reverse directions
In a third embodiment of the invention, as shown in
to divert lines of the magnetic ?eld.
'
)ternal zone B’ than in internal “zone A'.
FIG. ‘10, the device differs from that shown‘ in FIG. 1
8. A device as described in claim 1 including magnetic
mainly in the arrangement of the ion source“ and the ac
shunts for said electric coils to divert lines of the mag
netic ?eld.
celeration‘ electrode. These are enclosed within a single
circular insulator 48, ‘which fcan‘be made up of several 70
9. A device as described in claim 1 wherein the tension
of said ion source is varied in a sawtoothed voltage wave.
elements. The ion so‘u‘rce‘49 is located at the bottom of
. the ‘insulator.
It ‘has an annular form and emits an ion
“beam in a plane sheet normal to axis X—X. The ac
10. A device as described in claim 1, said course of
7 ions emitting from an internal surface, said means for
celerlation electrode comprises several levels, such as 50,
production ‘and con?nement of plasma being disposed so
distributed between the ion source and the casing 1 of 75 that the ions issuing ‘from said source before reaching the
3,093,765
7
s
,
vaxis successively traverse two regions where the magnetic
?eld is directed parallel to the axis of said source in one
,
‘the other region, the total ?ux on a surface'bearing on
a
8
,
said ion source ‘being a saw-toothed voltage wave
.direction in one region and in the opposite direction to
said source *being approximately zero.
.
12. A device as described ‘in claim 10, the tension of
a
_.
_
"
_
References Clted “1 the ?le of vthls patent
5
'
UNITED STATES PATENTS
,11. A device as described in claim 10, said acceleration
electrode and said source of ions ‘being so disposed vthat
292023 5
2,920,236
B611 et‘ a1_ ______________ __ Jam 5, 1960
Chambers et a1. ____' _____ __ Jan. 5, 1960
the sheet of ions is conical.
2;927,23_2
'Luce __; ____ .._'_______ __ Mar. 1, 1960
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