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Патент USA US3019350

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Jan. 30, 1962
_
A. H. YOUMANS ETAL
METHOD OF STABILIZING THE OUTPUT OF A.
'
3,019,340
NUCLEAR EMISSION SOURCE
Flled July 1. 1957
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Jan. 30, 1962 _
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A. H. YOUMANS ETl'AL
METHOD OF STABILIZING THE OUTPUT OF A
_
3,019,340
NUCLEAR EMISSION SOURCE
Flled July 1. 1957
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Arthur H. Youman‘s
Thomas R-Hubbara; Jz
W714.
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Agenf
Unite grates
3,919,340
Patented Jan. 30, 1962
1
3,019,340
METHOD OF STABILIZING THE OUTPUT 0F
A NUCLEAR EMISSION SOURCE
Arthur H. Youmans and Thomas P. Hubbard, Jr., Tulsa,
Okla, assignors to Well Surveys, Incorporated, a cor
poration of Delaware
Filed July 1, 1957, Ser. No. 669,132
’
7 Claims.
(Cl. 250-845)
2
that of FIG. 1, with the shaded areas representing the
emission resulting from bombardment of a target of
?nite thickness with a beam composed of both mon
atomic and diatomic ions;
'i
FIG. 3 shows the same thin target yield curve as that
of FIG. 2 but the shaded portions represent the neutron
output at an increased accelerating voltage;
'
FIG. 4 shows thin target yield curves for the reactions
resulting from bombarding a target composed of deuter
This invention relates to nuclear emission and is par 10 ium and tritium with an ion beam having‘ deuterium
ticularly directed to novel methods for stabilizing the
ions, tritium ions and composite deuterium-tritium.ions
output of devices for producing nuclear emission through
with the shaded areas representing the emission ‘caused
ion bombardment.
by the various types of ions with a target of ?nite thick
In the art of nuclear physics ‘and chemistry, many
ness;
operations require a source of nuclear emissions, such 15
FIG. 5 shows a thin target yield curve similar to that
as gamma rays, neutrons, protons, deuterons or alpha
of FIG. 1 showing the result when the ion beam current
particles. Among the most common sources of nuclear
increases uniformly with the accelerating voltage.
emission have been those device-s which achieve nuclear
The applicants have found that there are four factors
emission by accelerating ions in a beam against a target
which vary the output of nuclear emission sources of the
formed of suitable material to produce a desired reaction.
ion bombardment type. These factors are ion beam
In sources of this sort it is conventional to produce ions
current, ion beam composition, ion beam accelerating
of some particular elements and let these ions fall
voltage and target thickness. In the preferred embodi
through a potential difference toward the target. This
ment of the invention the beam current is maintained
accelerating voltage accelerates them in a beam to strike
constant and stabilization is accomplished by varying the
the target at high energies, thus permitting certain nuclear 25
reactions.
For example, deuterons are accelerated to
other parameters.
.
,
Normally, the ion beam will be composed of a mixture
about 100 kev. against'a tritiumtarget to produce a
of monatomic, diatomic, triatomic and possibly heavier
nuclear reaction evolving neutrons of 14.1 mev. Un
fortunately, these sources have been unsatisfactory for
ions of one or more isotopes of the same element. Each
of these different types of ions will react somewhat differ~
many applications because extremely complicated and ex 30 ently with the target material. However, the beam com
pensive apparatus is required in order that the rate of
position, that is, the ratios of the diiferent types of ions,
emission be maintained constant. For example, it has
will generally be constant for any given sourcef It is
been particularly di?icult to ‘stabilize the output from a
possible by conventional means to cause the beam to
neutron source of the type employed in radioactivity well
have a predetermined composition in some instances and,
logging and comprising a sealed ion accelerator and as 35 in any case, the composition may be determined. With
sociated acceleration voltage generator.
the beam current constant and of known composition,
This disadvantage of the prior art is overcome with
stabilization of the output may be obtained by varying
the present invention and novel methods are provided
either the accelerating voltage or target thickness or both.
for‘ stabilizing the output of any device which produces
For simplicity, the method of stabilization will ?rst
nuclear emission through ion bombardment by means of 40 be described for the case of a pure ion beam, that is, a
a reaction which has a resonance peak.
beam composed of only one type of ions of a single iso
tope. For example, it may be desired to produce emis
The advantages of the present invention are preferably
sion by bombarding a suitable single isotope target with
attained by selecting the target thickness and ion ac
celerating voltage such that, due to the resonance peak
a beam of monatomic ions. Curve N of FIG. 1 rep
of the reaaion, operation at a maximum point on the 45 resents the thin target yield curve for a typical resonance
emission yield curve is obtained.
type reaction, and R represents the resonance peak.fFor
Accordingly, it is an object of the present invention
to provide novel methods for stabilizing the output of
devices which produce nuclear emission through ion
bombardment by means of a reaction having a resonance 50
any target thickness, the ions will be slowed down as they
pass through the target and, consequently, to obtain an
optimum emission yield, the ions must strike the target
peak.
with an energy above that of the resonance peakv R, "as
indicated by line E of FIG. 1. With any practical ac
' A speci?c object of the present invention is to provide
such a method comprising establishing the beam com
celerating voltage, the initial energies of the ions from
the ion source will be negligible relative to the energy
position, target thickness and acceleration voltage such
derived from the accelerating voltage. Substantially all
that, due to the resonance peak of the reaction, operation 55 ions will have the same charge, having lost one, and only
at a maximum point on the emission yield curve is ob
one, electron, and ‘therefore these ions upon striking the
tained.
target will have energy E e.v. derived from the accelerat
A further speci?c object of the present invention is
ing voltage E volts. In travelling through a thin target
,to provide a novel method of stabilizing the output of a
the ions are subject to atomic coulomb forces and are
neutron source comprising a sealed ion accelerator and 60 slowed down. A few react with nuclei of target atoms
associated acceleration voltage generator of the type em
and are annihilated, but these may be neglected relative
ployed in radioactivity well logging.
to the number that are merely slowed down on their way
These and other objects and features of the present
through the target. The number of ions leaving a target
invention will be‘apparent from the following descrip
thinner than the range of the ions is, therefore, virtually
tion wherein reference is made to the ?gures of the ac
the same as the number entering. Every ion not annihi
companying drawings.
In the drawings:
lated by a nuclear reaction is slowed or reduced in en
ergy, at the same rate.v As it is slowed it'will have, at
‘ FIG. 1 shows a thin target yield curve for a reaction
any instant, a- probability of reacting with nuclei in ac
having a resonance peak. The shaded areasrepresent the
cordance with curve N. The slowing may be measured
emission resulting from bombardment of a target of ?nite 70 in units of energy, and the thickness of a target may be
thickness with a pure monatomic ion beam;
measured in amounts of slowing or “stopping power.”
FIG. 2 shows a thin target yield curve similar ‘to
and therefore ‘also in units of energy. 'The target thick.
8,019,340
ness may thus be represented in FIG. 1 by the dimension
A in units of energy and the energy retained by ions
passing out of the target will then be E—A. The emis
sion produced per beam atom is shown in FIG. 1 plotted
as a function of energy and will be proportional to the
shaded area of FIG. 1 lying below the curve N and be»,
4
ion than in a monatomic ion, the emission yield for any
polyatomic ion will be greater than that for any smaller
ion of the same energy per atom. On the other hand,
since the mass of a polyatomic ion is greater than that
of a monatomic ion, the acceleration provided by any
given accelerating voltage will result in a lower-energy
It has been found that any change in the accelerating
per atom than for a smaller ion. Thus, for example,
one mioroampere of diatomic ions at energy E will pro
‘thickness is selected so that for such thickness the maxi
of the diatomic ions is greater than that of the mon-
tween the lines E and E—A.
vide an emission yield equal to that provided by two
voltage B will shift the position of the lines E and E—A
but, when the instant invention is employed, such a 10 microamperes of monatomic ions at energy E/2.
As seen in FIG. 2, to determine an optimum point
change will not substantially change "the area bounded
for reactions involving monatomic and diatomic beam
by these lines below the curve N and, hence, will have
ions, the emission resulting from the monatomic com
substantially no effect on the total emission yield.
ponent of the ion beam may be represented in the man
By properly selecting the values for the accelerating
voltage E and target thickness A, a condition may be 15 ner described in connection with FIG. 1. That is, if the
ion beam is maintained constant and an accelerating
obtained such that the reaction cross-section for ions
voltage E is applied, the target thickness will appear as
striking the target with energy E is approximately equal
dimension A and the monatomic ions will emerge from
‘to the reaction cross-section for ions leaving the target
the target with energy E—A. The shaded area beneath
with energy E—A. Applicants have found that, for any
given value of accelerating voltage, there is a speci?c 20 curve N and bounded by the lines E and E—A will then
represent the emission for each unit of beam current.
value of target thickness at which, due to the resonance
In addition to this, there will be an emission yield due to
peak of the reaction, a maximum point on the emission
the diatomic ions. Since, as pointed out above, the mass.
yield curve is obtained at this voltage. That is, the target
mum yield is obtained at the selected accelerating voltage 25 atomic ions, the energy per atom of the diatomic ions
will be proportionately less for any given accelerating‘
‘in order that the neutron yield remains reasonably com
voltage. Thus, since the ion beam of FIG. 2 is com~
stant as the voltage varies by moderate amounts from
posed of monatomic and diatomic ions, the atoms of the
the selected value, the selected value being one con
diatomic ions will strike the target with energy E/ 2.
yeniently available. Obviously, this emission yield will
The target penetration or particle range of the diatomic
‘be ‘less than that which can be obtained with a thick 30
ions will be A’. Where A’ is the stopping power of the
target which absorbs all of the bombarding ions. How
target for diatomic ions of energy E; this stopping power,
ever, when applicants’ relationship has been established,
of course, is the same as the stopping power of the target
moderate changes in the value of the accelerating voltage for a monatomic ion of energy E/ 2. Thus A’ can be de
‘have substantially no effect on the emission yield. Hence,
(the operation'of the device has been stabilized. Con 35 termined from the range-energy curve for the monatomic
ions. Accordingly, the residual energy of each atom of
versely, for a given target thickness the accelerating‘ volt
the diatomic ions on leaving the target will be
age may be adjusted to operate on this maximum point
'on the emission yield curve.
Thus, this condition may
E
be obtained by adjusting either the accelerating voltage
2
E or the target thickness A or both. Thus, the operator 40
has the option of establishing the accelerating voltage at
‘a desired level and obtaining the desired equilibrium con
dition by varying the target thickness, or of maintaining
the target thickness ?xed and adjusting the accelerating
voltage to obtain equilibrium. Furthermore, as indicated
above, if neither of these parameters is critical, both may
be adjusted to obtain the desired condition for stabilized
operation.
'
I
A
and the emission yield resulting from bombardment of
the target by the diatomic component of the ion beam
may be represented in FIG. 2 by two times the shaded
area below curve N bounded by the lines
E
E
'2- and 2——.A
,
As will be seen in FIG.l, this equilibrium will be ob
tained when the energy of the ions striking the target, 50 It must be remembered that the diatomic component is
equivalent to a monatomic beam of half the energy and
E, is greater than the energy of the resonance peak R
of the reaction and the energy of the ions leaving the
twice the intensity. Therefore, the shaded area actually
represents only half of the emission caused by the dia
target, E—A, is less than the energy of the resonance
tomic ions.
'
point R. When this condition obtains, a change in ac
celerating voltage will shift the energy withwhich the 55 It will be apparent from FIG. 2, that any change in
the accelerating voltage E will cause both of these areas
ions strike the target, for example, from E to E’, and it
to shift. However, by using values of accelerating volt
vwill be seen that, in this case, the emission yield of these
age E and target thickness A to operate at the equilib
ions has been reduced. On the other hand, the change
rium point, additional moderate changes in accelerating
in accelerating voltage will also shift the energy of the
‘ions leaving the target after passing through it from 60 voltage B will have little effect on the emission yield.
E—A to E’-~A. This causes an increase in the emission
~yield of the ions leaving the target which will
sate for the loss of emission yield suffered by
entering the target with the result that the total
yield will remain unchanged. The are-a under
compen
the ions
emission
curve N 65
between E and E—A is substantially the same as the area
under the curve between E’ and E’—A. Thus, for mod
FIG. 3 is similar to FIG. 2, but shows that when the
equilibrium point has been obtained, a shift in accelerat
ing voltage from E, in FIG. 2, to E’, in FIG. 3, will
cause the emission yield of the monatomic ions to de
crease while the emission yield of the diatomic ions is
increased. Thus, for reasonably large changes in acceler
ating voltage, the total emission will be stabilized.
erate changes in accelerating voltage, the total emission
'yield has been stabilized.
In some instances, it may be necessary to employ a
composite target and/or an ion beam composed of more
In reactions involving more than one type of ion, for 70 than one isotope or even of isotopes of different elements.
Nevertheless, it has been found that where the ratio of
example, where the ion beam is composed of both mon
the mass of the monatomic ion of the heavier isotope to
atomic and diatomic ions of a single isotope, stabilization
that of the monatomic ion of the lighter isotope is less
frnay be obtained in a similar manner in the vicinity of
than about two to one, the method of the present inven
the resonance peak of the reaction. It will be under
stood that, since there ‘are more atoms in a polyatomic 75 tion is still applicable.
However, since the ion beam
3,019,340
5
may be composed of both monatomic and polyatomic
ions of each isotope, the conditions for stabilization will
obviously be considerably more complex. In addition
there may be ions which are composed of particles of
both isotopes.
6
atoms by tritium ions.
Considering ?rst the T(d,n)
curve, the monatomic deuterium ions strike the target
with energy Em and the target thickness is Am so that
these ions after passing through the target emerge with
energy EDP-Am and the neutron emission yield is pro
portional to the area bounded by these lines and below the
curve T(d,n). The diatomic deuterium ions strike the
To demonstrate this form of the invention, let us as
sume that it is desired to bombard a target composed of
deuterium and tritium with an ion beam composed of
target with energy Em and the target thickness ‘is AM
ions of each or both of these isotopes. It will be seen
so that these ions after passing through the target emerge
that under these conditions there will be at least six 10 with energy ED2—AD2 and the neutron emission yield is
reactions taking place simultaneously. There will be
proportional to the area bounded by these lines and the
deuterium ions bombarding tritium atoms in the target,
curve T(d,n). Similarly, the deuterium components of
deuterium ions bombarding deuterium target atoms, tri
the composite deuterium-tritium ions will strike the tar
tium ions bombarding deuterium atoms, tritium ions
get with energy EDDT and will produce a neutron emis~
bombarding tritium atoms composite deuterium-tritium 15 sion yield proportional to the area bounded by the lines
ions bombarding deuterium atoms, and composite deute
EDDT and EDDT——ADDT and lying below the curve T(d,n) .
rium-tritium ions bombarding tritium atoms. Further
Looking at the curve D(t,n), the monatomic tritium
more, each of these reactions has a resonance at a differ
ions strike the target with energy ET, and the target
ent energy level. In addition, the deuterons and tritons
thickness is AT1 so that after passing through the target,
may be both monatomic and polyatomic.
Fortunately, much of this complexity may be ignored.
At energies between 100 kev. to 200 kev., the reactions
caused by deuterium ions bombarding tritium atoms and
‘by tritium ions bombarding deuterium atoms both reach
their resonance peaks. On the other hand, the emission 25
yield for deuterium ions bombarding deuterium atoms is
about 1/300 that of either of the two former reactions and
the emission yield for tritium ions bombarding tritium
atoms is considerably less than any of these.
Conse
quently, the emission yield resulting from these last two
reactions may generally be ignored. On the other hand,
when the composite deuterium-tritium ions strike thetar
these ions emerge with energy ET1~AT1 and will pro
duce a neutron emission yield proportional to the area
bounded by the lines BIT-AT, and lying below the curve
‘D(t,n). The diatomic tritium ions strike the target with
energy ‘Em and will produce a neutron emission yield
proportional to the area bounded by the lines Em and
Bin-Am and the curve D(t,n). To complete the pic
ture, the tritium components of the composite deuterium
tritium ions will strike the target with energy ETDT and
will produce a neutron emission yield proportional to the
area bounded by the lines ETDT and ETDT—ATDT and the
curve D(t,n).
,
>
As seen in FIG. 4, equilibrium may be obtained by
get atoms, the ions react as monatomic ions of their
vbalancing the neutronemission yields of the two mona
respective isotopes and the energy of the composite ion
tomic ion beam components against the neutron emis
is shared by its components in proportion to their mass 35 sion yields of the four diatomic and composite ion beam
ratio. Thus, the tritium component reacts as a monatomic
components in substantially the same manner as de
tritium ion of 175 the energy of the composite ion while
scribed above With respect to FIGS. 1, 2 and 3. Thus,
the deuterium ion reacts as a monatomic deuterium ion
by properly selecting the values of the accelerating volt—
of 2/s the energy of the composite ion. Since this is so,
age E and target thickness A, a point will be found about
the emission yield of the composite ions has a substantial 40 which reasonable changes in accelerating voltage have
effect on the total emission yield. This effect may be
little effect on the total neutron emission yield.
determined by considering the components separately at
their proportionate energies.
In considering the isotopically pure ion beams, the
monatomic and diatomic components contribute signi?
Following this method, applicants have found that, in
' As seen in FIG. 4, the curve T(d,n) is the neutron
the series monatomic, diatomic, triatomic, etc. ions where
devices of the type which are employed in radioactivity
well logging to produce neutron emission by the deu
45 terium-tritium reaction, stabilization may be obtained
cantly to the emission yield. However, at energies less
with a target having a stopping power between 50 and
than about 400 kev., the emission resulting from heavier
250 kev., depending upon the target and beam composi
components is negligible and may safely be ignored.
tion, at accelerating voltages of less than 500 kev.
Applying the foregoing discussion to the case where a
For example, typical apparatus of this type used for
target formed of deuterium and tritium is bombarded by 50 radioactivity well logging is illustrated in FIG. 2 of US.
an ion beam composed of deuterium ions, tritium ions
Patent 2,689,918 to Arthur H. Youmans and is fully de
and composite deuterium-tritium ions, to produce neu
scribed in the speci?cation thcrof at column 3, line 70,
tron emission, as in the case of a borehole accelerator
to column 4, line 60. When such apparatus is made in
for radioactivity well logging, it will be seen that to ob
accordance with the present invention, high voltage sup
tain stable neutron emission We must obtain an equilib 55 ply 34 is less than 500 kev. and target 36 has a stopping
rium for the emission yields resulting from bombardment
power between 50 and 250 kev. or, more particularly, in
of deuterium atoms by monatomic and diatomic tritium
the relationships described herein.
ions and the tritium component of composite deuterium
In the foregoing description it has been shown that
,tritium ions and from bombardment of tritium atoms by
stabilization may be obtained both for simple cases, in
monatomic and diatomic deuterium ions and the deute 60 which a one or two component single isotope ion beam
rium component of the composite ions. Since the ener
bombards a single isotope target, and for more complex
gies with which these various types of ions strike the
cases, in which a multi-component multi-isotope ion beam
target are dependent upon mass, it will be apparent that
bombards a multi-isotope target, by properly selecting
these values will be different for each type of ion, as
accelerating voltage and target thickness. The problem
indicated in FIG. 4. As pointed out above, the target 65 thus becomes one of determining the values of these
thickness, measured in terms of stopping power will also
parameters.
be a function of the mass of the incident ions. However,
To provide a general equation for determining the
for deuterium and tritium ions having energies less than
proper accelerating voltage and target thickness, .it must
‘about 500 kev., the stopping power of the target may be
be considered that there may be both monatomic and
considered essentially independent of both the mass and 70 polyatomic ions bombarding a target composed of Q dif
the energy of the ions.
ferent isotopes. vThus, there will be N kinds of‘ ions, in
emission yield curve for bombardment of tritium atoms
polyatomic ions may be composed of more than‘ one
by deuterium ions while the curve D(t,n) is the neutron
isotope. As stated previously, the ion beam composi
emission yield curve for bombardment of deuterium 75 tion can be determined and, after this is known, the total
3,0193%
.
.
8
_
.
emission yield may be calculated for’ a variety of accele
beam as a result of a reaction having a resonance peak,
rating voltages fromthe formula
and adjusting the ion accelerating voltage to a value at
which, due to the resonance peak of said reaction,‘ the
nuclear emission produced per unit of thickness in the
?rst ditterential increment of said target is substantially
equal to the nuclear emission produced per unit of thick
Q
N
.
E 2InC'qnAn= Y=emission yield
g=1 1i=1
where :
ness in the last differential increment of said target.
3. The method of stabilizing the output of a device for
producing nuclear emission by means of ion bombard?
Cqn=average probability, for the particular target, of 10 ment of a target, said method comprising the steps of
the reaction of the n ion with the q target atom in the
energy range En to En—An where En is the energy
with which the n ion strikes the target and An is the
stopping power of the target for the 11 ion of energy
En
In=number of n ions striking the target per unit of time.
producing an ion beam of predetermined composition,
If a graph according to this relation is plotted showing
due to the resonance peak of said reaction, upon moder
emission yield as a function of accelerating voltage for
the particular target thickness, target composition and
beam composition, the graph will indicate that the emis~
sion yield reaches a maximum at a particular value of
accelerating voltage and it is at this value the stabilized
forming a target of a material which will produce nu
clear emission in response to bombardment of said tar
get by ions of said beam as a result of a reaction having
a resonance peak, accelerating. said ions toward said
target with a predetermined accelerating voltage, and ad
justing the‘ thickness of said target to avalue at which,
ate variation in the accelerating voltage the change in
nuclear emission‘ occasioned by the change thus effected
in the energy of ions entering the target is substantially
equal and opposite to the change in nuclear emission oc
casioned by the change thus e?ected in the energy of
operation will be obtained.
ions leaving said target.
I
In the alternative, if the accelerating voltage is ?xed, 25 j 4. The method of adjusting for stable operation a
the total emission yield may be calculated for a variety
device which employs ion bombardment to produce nu
of target thicknesses and a graph showing the emission
yield as a function of target thickness will, then, indicate
the target thickness at which stabilized operation at the
clear emission from a target my means of a reaction hav
vided that the beam current varies in such a manner as to
substantially equals the reaction cross-section for ions
leaving the target after passing through the target.
ing a resonance peak, said method comprising the steps
of producing an ion beam composed of a single type of
given acceleraing voltages may be obtained.
30 ions of a single isotope, accelerating the ions of said
While it has been assumed in the foregoiig descrip
beam toward said target with an energy greater than
tion that the beam current is maintained constant, it is
that of the resonance peak of said reaction, and estab
possible to employ the same method of stabilization for
lishing the accelerating voltage and target thickness such
devices in which the beam current is not constant pro
that the reaction cross-section for ions entering the target
be always functionally related to the accelerating volt
age. Thus, for example, if the beam current increases
linearly with the accelerating voltage, the effect would
be essentially to increase the values of curve N propor~
tionately, and it will be obvious from FIG. 5 that the
method of the present invention will still be applicable to
obtain stabilization of the emission and, in fact, the equa- _
'tions given above would still be approximately correct.
Thus, in FIG. 5, curve N’ represents the number of par
ticles emitted for the total number of beam ions of par
45
ticular energy.
Numerous other variations and modi?cations of the
present invention may obviously be made without depart
5. The method of adjusting for stable operation a
device for producing neutrons by bombarding a target
composed of deuterium and tritium with an ion beam
composed of deuterium and tritium ions, said method
comprising the steps of producing an ion beam of pre
determined composition accelerating the ions of said
beam with a speci?c accelerating voltage greater than
that of a resonance peak of the deuterium-tritium reac
tion to cause said ion beam to strike said target, and es
tablishing the accelerating voltage and target thickness
such that upon moderate variation in accelerating volt
age the change in neutron emission occasioned by the
ing from the present invention. Accordingly, it should
change thus effected in the energy of the ions entering
be clearly understood that those forms of the invention
said target is substantially equal and opposite to the
described above and shown in the ?gures of the accom 50 change in nuclear emission occasioned by the change
panying drawings are illustrative only and are not in~
thus effected in the energy of the ions leaving said target.
tended to limit the scope of the invention.
6. The method of adjusting for stable operation a de
We claim:
vicev for producing nuclear emission by means of ion
1. The method of stabilizing the output of a device
bombardment of a target, said method comprising the
.for producing nuclear emission by means of ion bombard~ 55 steps of producing an ion beam of a predetermined com
ment of a target, said method comprising the steps of
position of ions of at least one isotope of hydrogen, form
producing an ion beam of predetermined composition,
ing a target of a predetermined thickness of at least one
forming a target of material which will produce nuclear
isotope ofhydrogen which will produce nuclear emis
emission upon bombardment of said target with ions of
sion in response to bombardment of said target by said
said beam by a reaction having a resonance peak, estab 60 ‘ion beam as a result of a reaction having a resonance
lishing the target thickness and ion beam accelerating
peak, and accelerating the ions of said beam with an ac
voltage such that, due'to the resonance peak of said
celerating voltage such that the nuclear emission pro
reaction, upon moderate variation in accelerating volt
duced per unit of thickness in the ?rst differential incre~
age the change in nuclear emission occasioned by the
ment of said target is substantially equal to the nuclear
change thus eifected in the energy of ions entering said 65 emission produced per unit of thickness in the last dif
target is substantially equal and opposite to the change
ferential increment of said target.
in nuclear emission occasioned by the change thus ef~
7, The method of adjusting for stable operation a de
fected in the energy of ions leaving said target.
vice for producing nuclear emission by means of ion
2. The method of adjusting for stable operation a de
bombardment of a target, said method comprising the
vice for producing nuclear emission by means of ion 70 steps of producing an ion beam of predetermined com
bombardment of a target, said method comprising the
position, forming a target of a material which will pro
steps of producing an ion beam of predetermined com
duce nuclear emission in response to bombardment of
position, forming a target of a predetermlned thickness
said
target with ions of said beam by a reaction having
of a material which will produce nuclear emission in re
sponse to bombardment of said target by ions of said 75 a resonance peak, accelerating said ions toward said
8,019,840
9
target with an accelerating voltage which is related to the
target thickness in accordance with the equation
Q
N
17:2
zInCqnAn
g=1 n=1
10
2,525,832
2,769,096
Sheldon _____________ _.. Oct. 17, 1950
Frey ________________ __ Oct. 30, 1956
2,816,242
Goodman ___________ __ Dec. 10, 1957
2,845,560
Curtis et a1. __________ __ July 29, 1958
2,872,583
Owen _______________ __ Feb. 3, 1959
2,885,584
Van De Graaif ________ __ May 5, 1959
to obtain operation at a maximum in the emission yield
2,908,823
Ely _________________ __ Oct. 13, 1959
where Y is the emission yield, Q is the number of dif
2,929,933
Ela et al. ____________ __ Mar. 22, 1960
ferent isotopes in the target, q is a particular atom of
the target, N is the number of kinds of ions in the beam,
OTHER REFERENCES
n is a particular ion of the beam, In is the number of 10
Landenburg
et
al.: “On Neutrons From the Deuteron
n ions striking the target per unit time, Cqn is the aver
Deuteron Reaction,” Physical Review, Nov. 1, 1937,
age probability, for the particular target, of the reaction
pages 911 to 918.
of the n ion with the q target atom in the energy range
Hanson et al.: Reviews of Modern Physics, v01. 21,
En to En—An where En is the energy with which the
n ion strikes the target and An is the stopping power of 15 No. 4, October 1949, pp. 635-650.
Semat: Introduction to Atomic and Nuclear Physics,
the target for the n ion of energy En.
3 ed., published 1954 by Reinhart & Co., New York, pp.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,287,619
Kallmann et a1. ______ __ June 23, 1942
55-58.
Warters et al.: “The Elastic Scattering of Protons by
20 Lithuim,” Physical Review, vol. 91, Aug. 15, 1953, pages
UNITED STATES ‘PATENT, ()FFICE
CERTIFICATE OF (IQRRECTIQN
Patent Noa 3tvOl9q34O
January 30v 1962
Arthur HQ Youmans et al0
It is hereby certified that error appears in the above ‘numbered pat
> ent requiring correction and that the ‘said Letters Patent should read as
corrected below.
.
-
Column 6‘z line 22". after "lines" insert -=_=~== ETl and -==; line 52V for "therof" read -=== thereof —==; column 7v line 30‘,
for "acceleraing‘" read -=== accelerating -=~=-;; line 31n for
“'foregoiig" read —— foregoing ~==§ column 8‘I line 270 for
"my"
read
~‘=—
by
---~,,
7
'
'
Signed and sealed this 5th day of June 1962:.
(SEAL)
Attest: ‘
- DAVID L. LADD
ERNEST W, SWIDER
Attesting Officer
Commissioner of Patents
UNITED STATES‘IPATENT‘ OFFICE
CERTIFICATE OF CORRECTION‘
Patent No‘. 31019340
January 30‘, 1962
Arthur HQ Youmans et a1 0
It is hereby certified that error appears in the above ‘numbered pat
ant requiring correction and that the said Letters Patent should read as
corrected below.
Column 69 line 22‘, aften "lines" insert -=-== Em and -=-=-;
line 520 for "'therof" read me thereof -=-=; column 7 V line 30 9
for ‘"acceleraing“ read -== accelerating ===3 line 31‘, for
"fonegoiig" read -— foregoing ===-; column 8“ line 2'1V for
"my"
read
-=-=-
by
—-°
,
‘
,
'
Signed and sealed this 5th day of June 1962,
(SEAL)
Attest:
- DAVID L. LADD
ERNEST W a
SWIDER
Attesting Officer
Commissioner of Patents
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