close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3024392

код для вставки
March 6, 1962
N. F. VERSTER
3,024,379
ARRANGEMENT FOR ACCELERATING PARTICLES
Filed Nov. 2'7, 1959
3 Sheets-Sheet 1
March'?, 1962
N. FQVERSTER
. 3,024,379’
ARRANGEMENT FOR ACCELERATING PARTICLES
Filed Nov. 2'7, 1959
3 Sheets~$heet 2
i9
-
I
' Lin
32")
Jl
/1| 34’ /
Q?‘
'9-
'?
_
-
l
t.
r
d
-
k 14., "°_
2e
/27
\ 324
I
'
T
20
>
v
_
"'
AB
INVENTOR
N. F. VERS TER
L4 lP
AGENT
March 6, 1962
N. F. VERSTER
3,024,379
ARRANGEMENT FOR‘ ACCELERATING PARTICLES
_
Filed Nov. 27, 1959
'
s Sheets-Sheet s
F|G.6
\
+2
>
0° 30°
-‘z
6.7
360° "
INVENTOR
N.l-'. VERsTER
AGENT
United States Patent 0 M
3,024,379
Patented Mar. 6, 1962
1
2
3,024,379
FIG. 5 shows the variation in strength of the mag
netic ?eld along the radius 3-—3 in the central plane of the
cyclotron, along the horizontal axis on the same scale as
ARRANGEMENT FOR ACQELERATKNG
PARTICLES
Nico Frederick ‘Verster, Eindhoven, Netherlands, assignor
to North American Philips Company, lino, New York,
N.Y., a corporation of Delaware
Filed Nov. 27, 1959, Ser. No. 855,651
Claims priority, application Netherlands Jan. 23, 1959
4 Claims. (til. 313--62)
FIG. 2.
FIG. 6 shows, in rectangular co-ordinates, the cause
of the radial paths of three particles during the end of
the pre-ultimate revolution and during the ultimate revo
lotion, and
FIG. 7 shows, in rectangular co-ordinates, the cause
10 of the axial paths of four particles during the end of the
This invention relates to arrangements for accelerating
pre-ultimate revolution and during the ultimate revolu
particles, of the cyclotron type having a magnetic main
tion.
?eld which is substantially independent of the azimuthal
In FIG. 1, reference numeral 1 indicates the circum
angle, comprising a device for extracting accelerated
ference of one of the pole-pieces of the cyclotron. One
particles from the spiralised paths, having a regenerator 15 of the D-electrodes is indicated by 4. The second elec
ferromagnetic material which causes the magnetic ?eld
trode 5 is in known manner of the “dummy-D” type.
outside the spiralised paths to be increased through a
Between the two electrodes there is included an alternat
small azimuthal angle.
ing voltage source which is shown diagrammatically at
In cyclotrons and synchro-cyclotrons of known type the
6. The frequency of the alternating voltage applied is
accelerated particles are often extracted from the accel 20 constant in a classic cyclotron, whereas it is varied in a
eration path by utilising only the aboveanentioned re
synchro—cyclotron.
generator. It is also known to use, in addition, a so
called “peeler” which causes the magnetic ?eld outside
trons or alpha-particles are injected in known manner
The particles to be accelerated, such as protons, deu
the spiralised paths to be decreased through a small azi
into the central portion of the cyclotron. By the ac
muthal angle and which, as viewed in the direction of cir 25 tion of the constant magnetic ?eld, which is substantially
culation of the accelerated particles, is situated before
at right angles to the plane of the drawing, together with
the regenerator, that is to say, as measured azimuthally,
the electric alternating ?eld between the electrodes 4 and
about 90° before the regenerator. Between this “peeler”
5, the particles describe spiralised paths which, in the
and the regenerator there is located the mouth of the
case under consideration, are traversed in the clockwise
channel for the emergence of the particles.
>
30 direction.
In such arrangements the percentage of the particles
It is to be noted that the present invention relates to
which enters the channel of emergence and impinges on
arrangements, the magnetic main ?eld of which, that is to
the target arranged behind it, is compartively low due
say, the ?eld produced by the pole-pieces, is substantially
to considerable radial spread of the particles occurring
independent of the azimuthal angle, so that the magnetic
if the axial spread which likewise exists is maintained
. ?eld is substantially of equal strength at all points of a
within reasonable limits. Consequently, in such known
circle about the centre 7, located in a plane parallel to
arrangements, in general, only about 5% of the particles
the central plane.
reach the target.
For the extraction of the particles to be accelerated,
An object of the invention is to provide a cyclotron
there is ?rstly provided in known manner a regenerator
or synchro-cyclotron having a device for extracting the 40 8 which also utilises correcting bodies 10, 11, 12, 13
accelerated particles such that satisfactory radial con
positioned more inwards for the purpose of correcting the
centration into a beam is obtained for a considerable pro
orbital travel of the particles. The regenerator and cor
portion, for example at least 20%, of the particles, while
recting means will be explained hereinafter with refer~
retaining reasonable restriction of the deviations in the
ence to FIGS. 2 and 3.
axial direction.
As viewed in the direction of reduction of the particles,
45
The arrangement according to the invention is charac
about 30° further means 9 are provided for restricting
terized in that, as viewed in the direction of circulation
the paths of the particles in an axial direction. These
of the accelerated particles, within an azimuthal angle
restricting means will be referred to hereinafter as the
of about 60° after the regenerator, there are provided
compressor. Also positioned more inwards are correct
means of ferromagnetic material for restricting the paths 50 ing bodies 14, 15 and 16. The compressor and the asso
in an axial direction, these restricting means causing the
ciated correcting bodies will be explained with reference
decrease of the magnetic ?eld upon increasing radius to
to FIGS. 4 and 5.
be intensi?ed through a small azimuthal angle in the re
The last equilibrium path described by a particle be
gion of the last path of the particles.
fore being considerably in?uenced by variations in the
In order that the invention may be readily carried into 65 ?eld brought about by regenerator 8, compressor 9 and
effect, one embodiment will now be described in detail
the associated correcting means is shown diagrammatically '
by way of example, with reference to the accompanying
drawings, in which:
by a dotted circle 17. Subsequently, the particle describes
a further number of paths (not shown) whereafter the
FIG. 1 is a plan view of part of an arrangement of
particle, if su?icient concentration is provided, is either
the cyclotron type, of which only those elements are 60 extracted along the dotted path 18 or lost. Approxi
shown which are necessary for proper understanding of
the invention.
FIG. 2 is a cross-sectional view along the radius 2-2
at right angles to the plane of drawing of FIG. 1, but
on an enlarged scale.
FIG. 3 shows the variation in strength of the magnetic
?eld along the radius 2—2 in the central plane of the
cyclotron, along the horizontal axis on the same scale as
FIG. 2.
mately at the area 18 it is possible to arrange a channel
of emergence of magnetic material or a plurality of iron
bodies in order to lead the discharged particles towards
the target.
Since such means are known and not essen
65 tial to proper understanding of the invention, they are
omitted in the drawing for the sake of simplicity. -
Although it will be evident that the dimensions of the
regenerator and of the compressor, as well as the rela
tive positioning are dependent upon a number of param
FIG. 4 is a cross-sectional view along the radius 3-3
eters determined by the operational condition of the
at right angles to the plane of drawing of FIG. 1, on the 70 cyclotron, several possible dimensions and rules will be
same scale as FIG. 2.
given hereinafter.
3,024,379
3
FIG. 1 shows one embodiment approximately to scale,
in which the diameter of the pole-pieces is 300 cms. The
largest radial dimension of regenerator 8 is about 12 cms.
and the length of the regenerator, that is to say at right
angles to the radius 2—2, is about 20 cms., so that the
azimuthal angle of the regenerator in the present ex
4
along which the regenerator, the compressor and again
the regenerator are shown diagrammatically at 0°, 30°
and 360° respectively. The radial deviation r-—r0 is
plotted in a vertical direction. At the left-hand side of
the regenerator at 0° there are shown the radial devia
tions of three particles a, b and c at the end of the last
paths described by them before describing the path in
which they are extracted. Between the paths of the
measured azimuthally, is arranged about 30° further, has
particles a and c are the paths of about 40% of the
a largest radial dimension of about 3 cms., which is
particles of the beam. The particles in traversing the
10
shown too large for the sake of clarity. In the azimuthal
regenerator undergo a deviation which is strongly directed
direction, the compressor has a length of about 15 cms.,
inwards. After part of one revolution, the paths of the
which corresponds to an azimuthal angle of nearly 10°.
particles before the regenerator reach a caustic focus,
Insofar as reference is made to a variation in the mag
as shown at 28.
netic ?eld through a small azimuthal angle, this is to be
For the compressor which in this example comes an
understood to mean an angle which in practical cases is
azimuthal angle of 30° after the regenerator, it is of
usually less than 30°.
primary importance to be positioned so that the particles
In FIG. 2, the reference numerals 19 and 20 indicate
still have a positive radial amplitude at the area of the
parts of the two pole-pieces with their extreme edges 1.
compressor. With the paths of the particles as shown, it
The regenerator 8 comprises two parts arranged sym
was still possible to position the compressor a little farther
metrically with respect to the centre plane 21 of the cy
after the regenerator, viz. up to approximately an angle
clotron. The correcting bodies 10, 11, 12 and 13 also
of 45°. The maximum azimuthal angle which is still per
comprise parts which are arranged symmetrically. As in
missible in practice will be about 60", dependent upon the
the case of the regenerator 8, they are made of ferro
kind of the cyclotron.
magnetic material. It is common practice for the bodies
FIG. 7 again shows, along the horizontal axis, the
8, 10, 11, 12, and 13 to be rigidly secured to the pole
regenerator at 0° and 360° and the compressor at 30°.
pieces 19 and 20 by means of non-magnetic member 34.
The deviation in the Z-direction, the axial deviation, of
The envelope 33 encloses the evacuated chamber.
the particles is plotted in a vertical direction. To the
The distance between the two pole-pieces 19 and 20,
left of the regenerator at 0° there are shown the axial
in a direction towards the outer edge 1, decreases in
a stepwise manner in order to obtain a better course of 30 deviations of four particles, at the end of the last path
ample is about 12.5°..
The compressor 9 which, as
the lines of force of the barrel-like type and hence an in
crease of the region serviceable for spiralised paths.
In FIG. 2, the equilibrium paths of the particles ex
tend at the left-hand side of point 22, which corresponds
before that in which they are extracted. The compressor
causes the paths to be greatly bent backwards towards
the centre plane so that the beam is also restricted suf
?ciently in the axial direction.
To ensure satisfactory performance of the arrangement
it
is desirable for the position of the compressor to be
particle extend in the region between points 22 and 23,
also chosen so that for the majority of the particles reach
the particle upon being extracted subsequently entering
ing the compressor with a positive slope, the axial ampli
the zone outside point 24.
tude is also positive and that for the majority of the
The curve shown in FIG. 3 shows the variation AB
in the vertical component of the magnetic ?eld in the 40 particles reaching the compressor with a negative slope,
the axial amplitude is also negative, and that these slopes
centre plane 21 along the radius 2—2, which variation is
have become smaller upon leaving the compressor. These
brought about by regenerator 8 and the correcting means
requirements are ful?lled for the paths shown in the
10, 11, 12 and 13. The regenerator increases the mag
?gures.
netic ?eld outside the spiralised paths. The decrease of
In relation to FIG. 6, it is still to be noted that with
the ?eld which then occurs more inwards is corrected
proper choice of the strength of the regenerator and of
by the ?eld of the bodies 10, 11, 12, 13.
the compressor, the ratio between the various radial am~
In FIG. 4, the parts of the two pole-pieces are again
plitudes of the paths at 28 is considerably closer to unity
indicated by 19 and 20. In the embodiment shown, the
than at the end of the last path at 0°. Due to the re
compressor 9 comprises one body of ferromagnetic ma
sulting smaller difference in amplitude and in relative
50
terial which is arranged symmetrically with respect to
phase shift, the particles either approach one another or
the centre plane 21. Each of the correcting bodies 14,
describe paths which are more or less parallel. in either
15 and 16 comprises two parts likewise made of ferro
case
the extraction of the particles towards a target is
magnetic material. The compressor and correcting bodies
simpler. As previously mentioned, it is otherwise pos
are likewise secured to the pole pieces by member 34.
sible to use known expedients, such as a magnetic channel
The equilibrium paths of the particles extend in the re
or means correcting the path, for leading the particles
gion to the left of point 26, the further paths of the
towards a target.
particles passing through the region inside points 26
What is claimed is:
and 27.
1. A particle accelerator comprising in combination an
FIG. 5 shows in full line the variation AB in the vertical
component of the magnetic ?eld in the centre plane 21 60 evacuated chamber, means to inject particles into said
evacuated chamber, means for accelerating particles in
along the radius 3-3. The compressor 9 decreases the
said chamber in spiral paths including means for produc
magnetic ?eld outside the spiralised paths. The decrease
ing a magnetic ?eld substantially independent of azi
of the ?eld which occurs more inwards is corrected by the
to the circle 17 of FIG. 1. All the further paths of the 35
muthal angle and means to produce an electrostatic ?eld,
correcting bodies 14, 15 and 16. The curve of FIG. 5
shows a negative slope at the area of the last path of the 65 means to extract accelerated particles from said chamber,
a regenerator of ferromagnetic material for producing a
particles, that is to say, in the region directly to the left
magnetic ?eld in the region outside of the spiral paths
of point 27 in FIG. 4. It is to be noted that there is no
which is increased through a small azimuthal angle, and
need to obtain an absolute decrease of the ?eld at this
ferromagnetic means for restricting the spiral paths in an
area. If, for example, the correcting body 14 is larger,
a variation is obtained as shown in dotted line in FIG. 70 axial direction positioned within an azimuthal angle of
60° after the regenerator whereby the decrease of the
5, in which event the ?eld though being increased at the
magnetic ?eld with increasing radius is intensi?ed through
area of the last path, still exhibits a decrease upon increas
a small azimuthal angle in the region of the last path of
ing radius.
the particles.
In FIG. 6, the horizontal axis indicates the circle 17 of
2. A particle accelerator as claimed in claim 1 in which
FIG. 1 of the last equilibrium path having a radius r0, 75
8,024,379
5
6
the ferromagnetic means for restricting the spiral paths in
an axial direction includes a magnetic ?eld weakening
member positioned to decrease the magnetic ?eld outside
4. A particle accelerator as claimed in claim 3 in which
the magnetic ?eld producing means are a pair of pole
members and the correcting bodies are attached to the
-
the spiral paths.
pole members by bodies of non-magnetic material.
3. A particle accelerator as claimed in claim 2 in which 5
References Cited in the ?le of this patent
the ferromagnetic means Includes correcting bodles of
ferromagnetic material located to correct the decrease in
the magnetic ?eld in an inward radial direction.
UNITED STATES PATENTS
2,812,463
Teng et a1 _____________ __ Nov. 5, 1957
Документ
Категория
Без категории
Просмотров
0
Размер файла
461 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа