Nested high voltage generator/particle accelerator

A high voltage generator/particle accelerator with nested electrostatic generators each of which is sufficiently isolated from its neighbors that insulators between them can efficiently isolate them from one another at respectively lower voltages. The advantages of the greater efficiency of the insulators at lower voltages can be utilized to reduce the bulk of the over-all device.

FIELD OF THE INVENTION 
This invention relates to a high voltage electrostatic generator and to a 
particle accelerator which utilizes this generator. 
High voltage particle accelerators have a variety of applications in modern 
technology, including radiation processing, medical isotope production, 
semiconductor manufacturing, and surface studies. The majority of these 
applications require energies of 5 MeV or less. In this energy range, 
electrostatic generators, in which the full accelerating voltage exists 
across a single insulator or segmented insulator, are the most effective 
means of accelerating particles. At energies above one MeV, however, 
electrostatic insulators become extremely large and cumbersome. 
The size of the accelerator grows more rapidly than the energy because the 
electric field strength of insulators decreases with increasing voltage. 
If this problem can be overcome, more compact electrostatic generators can 
be developed. In the prior art, the resonant core transformer was 
developed in order to segment the applied voltage. However, the 
significance of topologically separating the various voltages was not 
understood. Similarly, resistive grading can be used to segment voltages. 
However, the inevitable existence of transients makes the development of 
pulsed unbalanced voltages unavoidable. 
In this patent, there is described a technique which will allow one to 
utilize the electric field strength of insulators which is available at 
low voltages to build a high voltage d.c. accelerator. The technique of 
topologically "nesting" high voltage systems allows one to isolate 
individual lower voltage systems without developing the full voltage in 
any one insulator or insulator stack. In a nested system, each voltage 
generator is disposed inside an adjoining generator. By the laws of 
electrostatics, these generators are totally isolated if they are 
separated by a continuous closed piece of metal. In the instant invention, 
in its embodiment wherein power is supplied externally, only small holes 
which allow particles to enter and leave the generator, and small slots 
which control magnetic field penetration are present. In embodiments 
wherein power is supplied internally by batteries or motor driven 
generators, even these slots are not needed. In both circumstances one may 
treat the insulation of each generator separately, with the criteria 
applicable to lower voltage equipment. This in turn will allow one to 
reduce the size and complication of d.c. high voltage accelerators. Using 
this technique, more compact and cost effective electrostatic generators 
can be developed. 
The objective is to provide a class of high voltage generators which makes 
use of the principles discussed above, thereby to provide novel, effective 
methods to provide power to individual nested modules. A device which 
embodies these concepts will be smaller and less expensive than a 
competing device. 
BRIEF DESCRIPTION OF THE INVENTION 
The invention is a group of high voltage generators, each inner one encased 
inside an adjoining outer one, with a power source available to each, a 
high voltage vacuum insulator, and a sufficiently complete conductive 
casing separating each pair of supplies. Power can be provided in various 
ways, the generator construction being adapted to each. Examples are a 
battery in each generator, power supplied from an external primary 
transformer winding through magnetic induction to a transformer secondary 
winding, or through a shaft driven internal alternator. 
Such a generator comprises a plurality of such high voltage power supplies. 
These generators are cup-like and are nested within one another to form an 
axially-extending assembly. Each of the generators is surrounded by a 
Faraday cage which sufficiently isolates the generators from one another 
electrostatically, depending on the type of power source employed. 
In some embodiments where the power is supplied externally, the 
electrostatic isolation is intentionally imperfect, because it will be 
penetrated by openings to permit flow of magnetic flux, but still will 
significantly and sufficiently isolate adjacent generators from one 
another. A primary transformer winding externally of the nested generators 
is thereby effective to develop a voltage by means of a secondary winding 
inside each of the generators. In other embodiments of the invention, the 
Faraday case can be complete, provided the power source is internal. 
Insulator means is provided between adjacent generators, so that the 
voltage across each is only a fraction of the total developed voltage 
across the entire device. Still, because the insulators are individually 
operating at a relatively lower voltage, advantage can be taken of the 
fact that they are more efficient at lower voltages. Accordingly, the 
device can be made much smaller than if all of the insulators have to 
resist the ultimate voltage.

DETAILED DESCRIPTION OF THE INVENTIONS 
There is shown in FIG. 1 a high voltage particle accelerator which operates 
in accordance with the principles of the invention. It consists of a 
number of individual high voltage d.c. generators arranged so that each 
individual generator is completely enclosed inside an adjoining generator, 
and completely encloses the other adjoining generator. The common wall 1 
between adjoining generators is arranged to be a nearly complete conductor 
with relatively few openings, or many small openings such as in a metal 
screen. Common walls 1 are separated by oil, gas, solid, or vacuum 
insulators 10, schematically shown as open spaces between the common 
walls. The outermost wall 1 has an insulator only at its inside surface. 
The walls are shown schematically by a single line, rather than with 
double lines in FIGS. 1 and 2. Openings of note are the slot 8 of FIG. 2 
which allows penetration of magnetic flux without unsuitably compromising 
the electrostatic shielding provided by the conductive walls 1. A 
conductive patch 19 fits across the overlapping edges of walls 1, but does 
not close slot 8. This enables magnetic flux to pass, but it assists in 
electrostatic separation. The winding 5 acts as a transformer secondary 
and converts the magnetic flux provided by the external generator into 
alternating electric currents which supply power to power supplies 7. The 
power supplies, which may be as simple as capacitor 12-diode 14 
combinations, or as complex as a switching power supply, provide a high 
voltage potential difference across respective insulators 10. These 
insulators, which may be made of dielectric film or an insulating liquid 
or gas, are designed to hold off the voltage across the module. The 
complete insulation afforded by the insulator 10 is terminated by vacuum 
interface 4 which provides a separation between the insulation required 
for the power supply, and the vacuum required for particle beam 
acceleration. The insulators may be angled or fluted in accordance with 
the principles of vacuum insulation. 
In the arrangement of FIG. 1, only the particle beam 3 develops the full 
voltage NVm, where Vm is the individual module voltage. Modules are 
completely separate since only the beam and the magnetic flux connect 
them. Thus, a transient which damages one module cannot cause a cascade 
type of breakdown as in other high voltage generators. 
For the device of FIG. 1, an external circuit is required to supply the 
magnetic flux which powers the modules, as shown schematically in FIG. 3. 
In FIG. 3, d.c. power is converted, by means of the power MOSFET switch 
11, into a high frequency oscillation suitable for driving the modules 
through the primary winding 9. In another embodiment of these concepts, 
power may be supplied by batteries contained in each power supply. A 
capacitor 12 is required in order to store energy for each pulse of 
magnetic flux. The voltage for a given beam current is proportional to the 
power in the external circuit. 
The current of the machine is controlled by varying the current in the 
particle source 2. This may be controlled in turn by a current control 15 
under control of a fiber optic link 13. After exiting the particle source, 
the particles are formed into a particle beam by the particle beam optics 
16. Auxiliary beam optics may be built into each module, and deployed in 
the region of the vacuum insulator 4. 
FIG. 4 shows an embodiment of the invention which includes internal power 
sources. It further shows the vacuum-tight nested structure required for 
all embodiments. 
Nested generators 50, 51, 52 are shown. Each is cup like, and each is 
nested into its neighbor to form a structure which extends axially along 
central axis 53. 
An outer shell 55 has a tubular wall 56 and a disc-like base 57 (FIG. 9). 
Its throat end 58 is closed by a closure 59. 
An exit neck 60 with a seal cap 61 closes throat 62 from which particles 
will be emitted. A vacuum pump 63 is provided to evacuate the enclosure 
formed by the outer shell and its closure. 
Generator 50 includes an insulating tubular wall 65 and an insulating base 
66. A tubular conducting outer member 67 is applied to the outer surface 
of wall 65, and a disc-like conductive outer base member 68 is applied to 
base 66. 
A tubular conductive inner member 70 is applied to the inner surface of 
tubular wall 65. A disc like conductive inner member 71 is applied to the 
inner surface of base 66. 
Generator 51 has a cup-like insulating structure with tubular wall 72 and 
base 73. It will be seen that conductive inner members 70 and 71 are also 
outer members for generator 51. 
A similar arrangement is provided for generator 52, in which an insulating 
cup-like member 74 has a tubular wall 75 and a disc like base 76. A 
conductive sleeve-like member 77 and disc-like member 78 form common means 
with generator 51. 
An innermost conductive sleeve like member 80 and disc-like member 81 are 
formed on the inside of insulating means 74. 
Thus, these three generators comprise a complete full-area conducting shell 
on each side of a cup-like insulating structure, each generator (except 
the outer most and innermost) sharing one of these conductive members. 
Conductive stage ending members 90, 91, 92, 93 extend from the conductive 
members to rings 94, 95, 96, 97 which form throat 62, and act as 
accelerators for the particles, because of the electrostatic voltage 
between them. 
Power supplies 100, 101 and 102 are provided for generators 50, 51 and 52, 
respectively. As schematically shown, these may be battery supplied 
devices which utilize conventional means to generate a high d.c. voltage 
between each adjacent pair of generators. 
As another example of an internally-contained power supply, FIG. 5 shows a 
motor-driven powered shaft 110 driving a plurality of rotors 111, 112, 113 
with stators 114, 115, 116 to generate a voltage which can be converted to 
a high voltage d.c. electrostatic voltage. If desired, in all embodiments, 
capacitors (not shown) can be charged to store energy that is to be 
released in bursts from the device. Such capacitors are optional. 
In all devices which have self-contained power supplies, the Faraday 
shields will be complete and without gaps. 
However, where energy is to be supplied from a power source which is 
coupled to an external supply, then the Faraday case must be modified in 
order that magnetic flux coupling is possible, but still with as little 
degradation of the electrostatic shielding as is possible. 
FIG. 6 is a somewhat schematic showing of a device 120 very similar to that 
of FIGS. 1 and 4, but modified to accept external power. 
In this device, power is derived from a primary transformer winding 122 
which encircles it. In this device, the power supply is completed by a 
secondary winding 123, 124, 125, 126, one for each generator. High voltage 
conversion devices 127 are provided to convert the ac output from the 
secondaries to d.c. 
Optional capacitors 130 are provided to store energy to be released as 
desired. 
Obviously this device will not function without magnetic flux. This is 
enabled by providing axial slots 80 (FIG. 7) in the tubular portions of 
the conductive members, for example in member 67. The conductive members 
on the bases will have openings, also. 
FIG. 8 shows the presently preferred shape of a conductive metal 135 for 
the end caps. It includes arcuate segments 136 and radial segments 137. 
Other forms are also useful, but the illustrated shape appears to provide 
for gap continuity with the slots in the tubular wall material, and good 
access to the secondaries through the ends. 
The device includes a particle source 140 of any suitable design. Cap 135 
is penetrable by the accelerated particles and is selected for that 
function. Control over the firing of the device can be exerted by any 
conventional means, including optical techniques. 
FIG. 6 also schematically shows beam 145 emitting from the particle source, 
on its way out of the throat through the emission end 146 of the device. 
This invention is characterized by the cup-like nesting of the generators. 
The auxiliary equipment and control equipment are entirely conventional. 
This invention is not to be limited by the embodiments shown in the 
drawings and described in the description, which is given by way of 
example and not of limitation, but only in accordance with the scope of 
the appended claims.