Transmission window for particle accelerator

A particle accelerator has a transmission window formed of a thin homogeneous foil having a predetermined thickness and having a predetermined length, and when laid fiat as a sheet having a transverse dimension. The window is formed to have a locus of a curve in cross section along the transverse dimension such that a radius of curvature of at least a portion of the curve in cross section is less than the length of the transverse dimension. Longitudinal channel and tubular shapes are preferred. Window cooling by gaseous and liquid fluid flows is also described. A transmission window assembly and a particle beam accelerator having an efficient rugged accelerator tube structure are also described. As one example, a liquid material processor and processing method employs either the curved window or a conventional window and advantageously directs liquid material onto the window to cool it, while a particle beam passing through the window enters the liquid material and changes it chemically in a predetermined manner. A mobile transporter enabling relocation of the liquid material processor between process sites is also described.

FIELD OF THE INVENTION 
The present invention relates to improvements in high energy particle 
accelerators especially for use within industrial processes for treating 
various materials. More particularly, the present invention relates to an 
improved transmission window for a particle accelerator and improved 
cooling methods and apparatus for drawing heat away from the transmission 
window, and for simultaneously processing the coolant. 
BACKGROUND OF THE INVENTION 
Particle accelerators are employed to irradiate a wide variety of materials 
for several purposes. One purpose is to facilitate or aid molecular 
crosslinking or polymerization of plastic and/or resin materials. Other 
uses include sterilization of foodstuffs and medical supplies and sewage, 
and the destruction of toxic or polluting organic materials from water, 
sediments and soil. 
A particle beam accelerator typically includes (i) an emitter for emitting 
the particle beam, (ii) an accelerator for shaping the emitted particles 
into a beam and for directing and accelerating the highly energized 
particle beam toward a transmission window, (iii) usually a beam scanning 
or deflection means and (iv) a transmission window and window mounting. A 
generator is provided for generating the considerable voltage difference 
needed to power the accelerator. 
The emitter and the accelerator section, which may comprise centrally 
arranged dynode elements or other beam shaping means, or electrostatic or 
electromagnetic lenses for shaping, focusing and directing the beam, are 
included within a highly evacuated vacuum chamber from which air molecules 
have been removed so that they cannot interfere with the particle beam 
during the emitting, shaping, directing and accelerating processes. 
The term "particle accelerator" includes accelerators for charged particles 
including, for example, electrons and heavier atomic particles, such as 
mesons or protons or other ions. These particles may be neutralized 
subsequent to acceleration, usually prior to exiting the vacuum chamber. 
The transmission window is provided at a target end of the vacuum chamber 
and enables the beam to pass therethrough and thereby exit the vacuum 
chamber. The workpiece to be irradiated by the particle beam is usually 
positioned outside the accelerator vacuum chamber and adjacent to the 
transmission window in the path of the particle beam. 
As used herein, "transmission window" is a sheet of material which is 
substantially transparent to the particle beam impinging thereon and 
passing therethrough. The transmission window is mounted on a window 
mounting comprising a support frame which includes securing and retention 
means which define a window envelope. 
The conventional beam transmission window, usually rectangular with 
filleted corners and generally perpendicular with respect to a 
longitudinal axis of the particle beam, must be sufficiently thin and of a 
suitable material so as not to attenuate the beam unduly from energy 
absorption and consequent heating. The window material must be 
sufficiently strong to withstand the combined stresses due to the pressure 
difference from typical ambient atmospheric pressure on one side thereof 
and high vacuum on the other and due to the heat generated by the particle 
beam in passing therethrough. 
Conventionally, transmission window foils have typically been lo installed 
between rectangular, generally flat flanges with filleted corners. The 
thin window foils are typically formed of titanium or titanium alloy 
sheets or foils which typically range in thickness between about 0.0005 
inches (0.013 mm) and 0.004 inches (0.104 mm). Much thicker stainless 
steel foils have been employed as transmission windows in irradiation 
apparatus for waste water/effluent processing. 
When vacuum is drawn on one side of a conventionally installed, flat foil 
window, the ambient air pressure on the other side tends to deform or 
"pillow" the foil window slightly. Part of this deformation results from 
transverse stretching of the foil. The radius of curvature of the foil 
resulting from drawing a vacuum is defined by the amount of transverse 
stress incurred. The relation therebetween for a foil of indefinite length 
(that is, neglecting end effects) is given by the following: 
EQU S1=(p(R/t) transverse stress (lb/in2) 
where 
p=differential pressure across foil (lb/in2) 
R=radius of curvature (inches) 
t=thickness of foil (inches); and 
S2=S1.sup.2 axial stress (lbs/in2) 
and the total stress S at any position on the window is given by: 
EQU S=(S1.sup.2 +S2.sup.2) (given in lbs/in2). 
Because the window is not of indefinite length, the ends thereof are 
subjected to additional axial stress as well as transverse stress because 
of the transverse and end retention structure adjacent thereto. The 
combination of axial and transverse stresses often results in wrinkling, 
non-uniform deformation, or even actual creasing at the window ends, and 
increases the chances of premature failure thereat. 
Because the sheet or foil materials used for conventional window 
configurations have inherent strength limitations, particle accelerator 
power output is limited, not by the high voltage generator capacity, but 
by the maximum heating due to the particle flux that the window material 
can withstand. The prior art has therefore sought to minimize the increase 
in temperature of the window during accelerator operation or decrease the 
mechanical stress it is subjected to. One known technique includes, for 
example, providing support grids inside the accelerator chamber and 
abutting against the window. In this particular technique, the support 
grids are often cooled by coolant flowing through internal cooling 
passages. While this technique effectively increases the active window 
area, the grids used in these known designs are within the beam path and 
therefore undesirably absorb a significant fraction of the incident 
accelerated particles. By "active window area" is meant that area of the 
window within and defined by the securing structure and having an active 
transverse dimension. A related technique of increasing the window area 
without providing additional support increases the tendency of the window 
foil to fail under stress. Thus, a hitherto unsatisfied need has arisen 
for an improved transmission window design wherein a given thickness of 
window foil can withstand a much higher particle flux than that 
contemplated heretofore. 
The efficacy of radiation-thermal cracking (RTC) and viscosity reduction of 
light and heavy petroleum stock, for example, has been reported in the 
prior art. Also, high energy particle experiments have been conducted in 
connection with processing of aqueous material including potable water, 
effluents and waste products in order to reduce chemically or eliminate 
toxic organic materials, such as PCBs, dioxins, phenols, benzenes, 
trichloroethylene, tetrachloroethylene, aromatic compounds, etc. 
The techniques heretofore employed have typically presented a liquid sheet 
or "waterfall" in front of, but spaced away from, the particle beam. 
Conventional wisdom associated with these techniques has been to employ 
very highly energetic particle beam sources (e.g. 1-3 MeV) in order to 
obtain sufficient particle penetration. In order to process usefully large 
quantities, high beam currents, such as 50 milliamperes or more have also 
been proposed. High energy and high beam currents require very expensive 
voltage generation and beam forming apparatus. 
However, McKeown (Radiation Physics and Chemistry, volume 22, 1983, pp 
419-430) in a paper entitled "Electron accelerators--a new approach" has 
disclosed a waste water irradiation target chamber comprising a curved 
vacuum window of 0.75 mm thick stainless steel welded to a fiat window 
surround, apparently of the same material. Waste water to be irradiated 
passes through a u-shaped structure containing the window in one arm. The 
impinging scanned electron beam was produced by a microwave accelerator 
and had an energy of 4 MeV. He states: "The scanned 4 MeV beam penetrated 
a 0.75 mm thick stainless steel into a fast flowing effluent target to 
test the design criteria of the mechanical and thermal stresses in the 
window . . . Experiments showed that sustained power dissipation of 100 
W/cm.sup.2 on the window showed no deterioration and failure occurred at 
3.5 times this design value." 
A power dissipation of 100 W/cm.sup.2 in a window 0.75 mm thick results in 
a thermal load to the scanned portion of the window of 168 W/g (watts per 
gram). Failure thus occurred at a window thermal loading of 584 W/g. 
Energy losses in a 4 MeV beam passing through such a window would exceed 
24%, that is, about 33.8 keV per mil of window thickness. Furthermore, on 
page 423 of this reference it is stated "FIG. 6 is a symbolic 
representation of the main elements which make up a linac-based 
accelerator. The efficiencies shown have already been achieved under 
optimum conditions and it now seems possible that total conversion of main 
power to electron beam power in the target could exceed 50%." FIG. 6 of 
this reference shows that the conversion efficiency before the window for 
a 10 MeV linac is 60.6%. As the window shown in this figure is stated to 
pass electrons of this energy through with 90% efficiency, the total 
delivered efficiency would be expected to be 54.53%. 
The use of a thin sheet of liquid material being irradiated has not been 
simultaneously employed to transfer heat away from a curved transmission 
window of the beam. Heretofore, there has been an unsolved need for a 
lower particle energy, higher beam current, higher efficiency irradiation 
apparatus for radiation processing of materials such as petroleum stock, 
potable water, effluents and other aqueous and liquid materials. We have 
discovered that, contrary to the teachings of McKeown and the general 
understanding of the prior art, by the use of a curved transmission window 
one can greatly reduce the stresses caused by the pressure differential 
thereacross during operation, thereby enabling use of highly electron 
transparent window foils in demanding operating conditions. This discovery 
enables us to provide a highly efficient rugged high power particle 
accelerator apparatus, which may easily be rendered transportable. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a novel transmission 
window design whereby the window foil is subjected to lower transverse 
stress, lower axial stress and lower total stress when subjected to a 
pressure difference between the two faces thereof, which is more readily 
and effectively cooled, and which still enables substantially all, e.g. at 
least 80%, preferably 90% or even at least 95%, of the accelerated 
incident particles to pass therethrough in a manner which overcomes the 
limitations and drawbacks of the prior art. 
A further object of the invention is to provide a compact transportable 
rugged high power, high efficiency particle accelerator apparatus for the 
radiation processing of the materials carried in fluid mediums while at 
the same time advantageously using the fluid medium for the efficient 
cooling and conducting of heat away from a transmission window of the 
particle accelerator. 
One more object of the present invention is to provide an improved 
transmission window configuration for a particle accelerator in which 
overall stress for a given particle flux is considerably reduced over that 
manifested using a substantially flat window of equivalent active area. 
The term "overall stress" means the combined stress due to the pressure 
difference across the window between atmospheric pressure on one side 
thereof and high vacuum on the other as well as due to the increase in 
temperature caused by the energy given up by a given particle flux in 
traversing the window which temperature increase results in a decrease in 
the ability of the window material to resist mechanical stress. By 
"substantially flat" we mean that the window in the absence of any 
pressure difference thereacross has a radius of curvature which is 
relatively large, for example, 100 times the active transverse dimension 
thereof. Thus, the radius of curvature of such flat windows is essentially 
infinite in the absence of any curvature resulting from the application of 
a pressure differential across the thickness thereof when the window is 
first mounted in the accelerator. Of course, once a vacuum is drawn on one 
side of the window when mounted in the accelerator housing, the nominally 
fiat window will tend to yield both elastically and to some degree 
permanently. For titanium windows the deformation is largely elastic, and 
these foils substantially recover from such deformation when the deforming 
stress is removed. Aluminum windows used in the prior art often undergo 
some amount of permanent deformation after initial application of a 
pressure difference thereacross and exhibit some degree of "dishing" 
thereafter. 
Another object of the present invention is to provide a transmission window 
which reduces transverse stress by providing an active area following a 
curved contour in transverse cross-section such that a radius of curvature 
thereof is less than twice the length of the active transverse dimension. 
Yet another object of the present invention is to provide methods and 
apparatus for the radiation processing of materials carried in fluid 
mediums while at the same time advantageously using the fluid medium for 
the efficient cooling and conducting of heat away from a transmission 
window of a high power, low energy, preferably ruggedized and 
transportable particle accelerator. This method of using the process 
materials and fluid medium for cooling the window also achieves the 
desired result of raising the temperature of the materials in a controlled 
fashion as may be conducive to desired chemical reactions. By placing the 
materials to be processed into direct,proximity of the beam window for 
cooling it also advantageously increases the incidence of energetic 
particles and electrons in the material, leading to a desired process 
result at lower beam energies, and therefore lower cost and complexity, 
than heretofore achieved. 
A further object of the present invention is to provide a transmission 
window which may be cooled more efficiently with a cooling fluid stream, 
thereby increasing the capacity of the window to dissipate higher power 
levels for a given window foil thickness. 
Yet another object of the present invention is to provide an improved and 
more efficient cooling arrangement and method for conducting heat away 
from a transmission window of a high energy particle accelerator, thereby 
increasing the capacity of the window to dissipate higher power levels for 
a given window foil thickness. 
In accordance with principles of the present invention a transmission 
window for a particle accelerator is formed from a thin homogeneous foil 
having a predetermined thickness and having a predetermined length between 
a first end and a second end, and a width, when laid fiat as a sheet prior 
to forming. The window along at least part of its length comprising an 
active area is formed to have the locus of a curve in cross section along 
an active transverse dimension such that a radius of curvature R of at 
least a portion of the curve in cross section is less than twice the 
length of the active transverse dimension. 
In one presently preferred specific embodiment of the present invention, a 
particle beam accelerator includes a housing defining a vacuum chamber, a 
charged particle source for generating a particle beam within the vacuum 
chamber and a particle accelerator for accelerating and directing the 
particle beam toward a first end of the housing which has been adapted to 
allow accelerated particles to pass therethrough. The housing includes an 
upper flange at the first end and a removable lower flange which mounts 
against the upper flange. The terms "upper flange" and "lower flange" as 
used in this specification are to be understood and interpreted in 
relation to the particle beam direction, the upper flange being closer to 
the particle source than the lower flange. The upper flange and the lower 
flange together include a securing mechanism to secure the homogeneous 
window foil which is mounted therebetween and defines aligned openings to 
the interior of the chamber which have a length and an active transverse 
dimension. The aligned openings may or may not be coextensive. The upper 
flange and the lower flange further define a curved locus at each of said 
first and second ends along the active transverse dimension. A 
transmission window is formed of homogeneous foil sheet material of a size 
sufficient to cover the aligned interior openings of the upper and lower 
flanges and the securing mechanism, and being of predetermined thickness. 
The transmission window is removably mountable between the upper flange 
and the lower flange such that the curved locus at each end along the 
active transverse dimension forms the homogeneous transmission window into 
a curved channel configuration having a finite radius of curvature in 
cross section along at least a portion of the transverse direction, the 
portion preferably being substantially the whole length of the active 
transverse dimension, but not greater. The term homogeneous foil or 
homogeneous (transmission) window when used in this specification means 
that the foils or window is substantially uniform in composition and 
structure, that is, without welds, bonds, seams or joints. A single 
longitudinal seamline to form the foil window as a tube is within our 
contemplation of "homogeneous" as used herein. 
In one aspect of the above described embodiment, the particle beam 
accelerator further comprises a sealing gasket disposed between the 
transmission window and the upper flange and functioning as a sealing 
mechanism therefor. 
In another presently preferred embodiment of the present invention, the 
curved transmission window may be formed to define a cylindrical tube 
through which a strand is drawn for radiation processing by the particle 
beam. 
In another aspect of the invention the active area of the transmission 
window prior to being mounted between the upper and the lower flanges of 
the accelerator housing is not substantially planar. Preferably, the 
transmission window of this aspect of the invention is preshaped to 
present a convex surface of generally elliptical shape to the vacuum 
chamber. 
In yet another aspect this invention provides a particle beam accelerator 
including a housing defining a vacuum chamber. A particle beam generator 
for generating a particle beam is within the vacuum chamber, as is a beam 
focussing and directing structure for directing the particle beam toward a 
radiation emission end of the housing. The housing includes an upper 
flange at the emission end and a removable lower flange. The upper flange 
and the lower flange define aligned interior openings. The openings have a 
length and an active transverse dimension. A transmission window is formed 
from a fiat foil sheet material of sufficient length and width so that 
after formation the window covers the aligned interior openings of the 
upper and lower flanges and window mounting mechanism. The window is of a 
predetermined thickness. The transmission window is removably mountable 
between the upper flange and the lower flange, such that the active area 
of the transmission window is at least 0.6 square inches, and such that 
the window is capable of withstanding energy deposition from the beam of 
at least 50 watts per square inch for a period of at least 1 hour without 
mechanical failure. Preferably, the window has an active area of a minimum 
of at least 1 square inch, for example 5 square inches, and most 
preferably an active area of 10 square inches; and it can withstand an 
energy flux from the beam of at least a minimum of about 75 watts per 
square inch, for example 100 watts per square inch, especially 125 watts 
per square inch, and most preferably at least 150 watts per square inch. 
As still a further facet of the present invention, a liquid material 
processor includes a housing containing a particle beam accelerator 
defining a vacuum chamber, a particle beam generator for generating a 
particle beam within the vacuum chamber, a particle beam focusing and 
directing structure for directing the particle beam toward a radiation 
emission end of the vacuum chamber, the housing including a transmission 
window at the radiation emission end for passing the particle beam and 
being formed of thin foil sheet material. In this facet of the invention, 
the processor comprises a source for supplying a quantity of liquid 
material to the housing, a liquid material flow directing structure within 
the housing and external to the vacuum chamber for directing a flow of 
liquid material supplied from the source: against an exterior surface of 
the transmission window in order to transfer heat from the transmission 
window to the liquid cooling fluid while simultaneous exposure to the 
particle beam modifies chemically the liquid cooling fluid, thereby 
resulting in processing of the liquid cooling fluid into processed liquid, 
and a liquid collection vessel within the housing for collecting the 
processed liquid. 
As one aspect of this facet of the invention, the liquid collection vessel 
defines a gaseous cavity above a liquid level, and the processor further 
comprising a pump, such as a vacuum pump, in communication with the 
gaseous cavity for reducing gas pressure within the cavity. 
As another aspect of this facet of the invention, a heat exchanger is 
provided for exchanging heat from the processed liquid within the liquid 
collection vessel to the supply of liquid material within the source. 
As a further aspect of this facet of the invention, the housing includes 
plural flanges, each flange defining a curve locus in an active transverse 
dimension lying in a plane substantially perpendicular to a longitudinal 
dimension. The transmission window is of a size sufficient following 
formation to enclose the curve locus of the plural flanges and extends 
therebetween in the longitudinal dimension and is of a predetermined 
thickness. Further, the transmission window is removably mountable between 
and positioned by the plural flanges such that the curve locus followed by 
the transmission window has a radius of curvature which does not exceed 
twice the length of the active transverse dimension. 
As a related aspect, the liquid material directing structure causes the 
flow of liquid material to be directed in accordance with an active 
transverse dimension of the transmission window. As a further related 
aspect, the liquid material directing structure comprises a knife-blade 
edge positioned adjacent to an edge of the active transverse dimension. In 
one more related aspect, the knife-blade edge is adjustably positionable 
in order to control thickness of a liquid sheet of the liquid cooling 
fluid as applied to cool the transmission window while undergoing the 
chemical processing. 
In accordance with a further facet of the present invention, a method is 
provided for processing materials by exposure to an accelerated particle 
beam. The method essentially comprises the steps of: 
generating a particle beam within a vacuum chamber, 
directing the particle beam toward a particle beam transmission window at a 
radiation emission end of the vacuum chamber, 
supplying from a source a quantity of said material to be processed within 
a fluid medium, such as a liquid, 
directing a flow of the fluid medium supplied from the source against an 
exterior surface of the particle beam transmission window in order to 
transfer heat therefrom to the medium, 
simultaneously exposing the material in the fluid medium to accelerated 
particles of said particle beam passing through the transmission window 
means in order to process the material. 
As one aspect of this facet of the invention, the step of exposing the 
material to accelerated particles of the particle beam causes chemical 
modification of the material. 
As another aspect of this facet of the invention, a further step is 
provided for collecting the fluid medium and processed material after heat 
transfer to the medium and simultaneous exposure of the material to the 
accelerated particles. 
As one more aspect of this facet of the invention, the medium itself 
comprises the material to be processed. 
As yet another aspect of this facet of the invention, further steps 
include: providing an enclosed processing chamber including the exterior 
surface of the particle beam-transmission window, and reducing gas 
pressure within the enclosed processing chamber to relieve stresses in the 
particle beam transmission window. 
As a still further aspect of this facet of the invention, a further step of 
exchanging heat from the fluid medium to an external heat transfer medium 
is carried out. 
Yet another aspect of this facet of the invention includes the further step 
of forming the particle beam transmission window means as a curved 
structure so that said external surface thereof has an active area along 
at least part of its length so that a locus of a curve in cross section 
along an active transverse dimension of the active area has a radius of 
curvature R of at least a portion of the curve in cross section less than 
twice the length of the formation transverse dimension. 
Still one more aspect of this facet of the invention includes the step of 
forming the particle beam transmission window means as a curved structure 
to follow guiding surfaces of plural flanges, each flange having a guiding 
surface defining a curve locus in an active transverse dimension lying in 
a plane substantially perpendicular to a longitudinal dimension, the 
particle beam transmission window being of a size sufficient following 
formation to enclose the curve locus of the plural flanges and extending 
therebetween in the said longitudinal dimension and being of predetermined 
thickness. 
As still one more aspect of this facet of the invention, the step of 
directing the flow of fluid medium includes the step of directing the flow 
of fluid medium to be directed in accordance with an active transverse 
dimension of the particle beam transmission window. As a related aspect, 
this step includes forming and directing a the fluid medium as a thin 
sheet of liquid against the particle beam transmission window along a 
longitudinal edge thereof. 
As one more aspect of this facet of the invention, further steps of 
collecting the fluid medium following heat transfer from the particle beam 
transmission window; and, transferring heat from the collected medium to 
said quantity of the material to be processed within the medium before it 
is directed against the particle beam transmission window, are carried out 
.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Window Configurations and Cooling 
Window materials useful in this invention include but are not limited to 
aluminum, titanium, beryllium and other materials such as organic polymers 
or polymer composites, such as metal coated polymers, for example. 
FIG. 1 illustrates an improved transmission window assembly configuration 
which reduces the value of the transverse stress in the window foil 
material to a much lower level by reducing the radius of curvature over 
that of a nominally fiat window configuration. 
In FIG. 1 a particle beam accelerator 10 is provided for irradiating a 
workpiece, such as a continuous strand or filament 11a. Alternatively, a 
workpiece sheet moving transversely with respect to the window opening 
along a direction of movement locus marked by the arrow 11b may also be 
irradiated by the accelerator 10 (see FIG. 4A discussed hereinafter). 
The accelerator 10 includes a housing 12 which provides an enclosure 
defining an vacuum chamber 21. A particle beam 13 is emitted from a source 
15 within the housing 10 and is denoted by the downwardly directed arrows 
in FIG. 1. The particle beam 13 may be focused and directed toward a thin 
titanium foil window 14 by any suitable conventional beam directing means 
(not shown). Thus, the particle beam 13 from the accelerator 10 may be 
linearly collimated and directed in conventional fashion, as shown in 
FIGS. 1, 2 and 4A, or it may be a swept and converged particle ribbon beam 
from an accelerator 10, in accordance with the teachings of the referenced 
and incorporated copending patent application Ser. No. 07/569,329, now 
U.S. Pat. No. 5,051,600 and as shown in FIG. 4. 
The foil window 14 is formed into an elongated, generally U-shaped channel 
structure having a radius of curvature R of the channel portion which 
radius is preferably much smaller than previously existing in conventional 
fiat window configurations of the prior art in which any radius of 
curvature resulted from imposition of a pressure differential between the 
ambient air outside the window and the vacuum inside the window once the 
window was installed in the accelerator. The foil window 14 may be a 
preform, as depicted in FIGS. 2 and 3 and discussed hereinafter, or it may 
be formed by following contour-forming peripheral surfaces of a window 
mounting structure. 
In one presently preferred form shown in FIG. 1, the foil window 14 is 
mounted between an upper flange structure 16 connected to or forming a 
part of the housing 12 and a detachable lower flange structure 18. A 
polymeric or metal O-ring gasket 20 provides a suitable vacuum seal 
between the foil window 14 and facing surfaces of the upper flange 16. A 
continuous loop of wire having a diameter of approximately 10 mils and 
formed of a suitable metal, such as tin, is presently preferred for 
providing a durable O-ring gasket 20. 
A series of screws 22 pass through openings 24 in the lower flange and 
engage threaded holes 26 formed in the upper flange 16 in order to 
securely affix and seal the window 14 to the housing 10. The flanges 16 
and 18 and associated structural elements described hereinabove may be 
formed as an assembly for retrofitting a conventional particle beam 
accelerator in order to achieve the advantages realized by practice of the 
principles of the present invention. Alternatively, the flanges 16 and 18 
may be parts of a particle accelerator, such as the accelerator 10, which 
is specially designed to make practical and effective use of the present 
invention. 
The arrangement illustrated in FIG. 1 enables ready and efficient 
replacement of the transmission window 14 and provides access to the 
interior vacuum chamber 21 defined by the housing 12. Contour-forming 
peripheral surfaces of the upper and lower flanges 16 and 18 of this 
arrangement guide and direct the transmission window 14 into an elongated, 
curved window structure, which, for the same material thickness, is 
considerably stronger than the substantially flat transmission window 
structures employed in the prior art. 
For example, for a three inch wide window using conventional flat flanges 
in lieu of the flanges 16 and 18, the radius of curvature R after vacuum 
loading would typically have a dimension of about six inches. Under those 
same conditions, a three inch wide window 14, when given a radius of 
curvature R of one and one half inches, manifests significantly reduced 
material stress in the thin foil of the window, the stress being less than 
about one quarter the comparable stress present in the vacuum loaded fiat 
window configuration. 
FIG. 2 illustrates a transmission window embodiment 14A of the present 
invention which presents a curved convex surface to the vacuum chamber 
along a substantial part of its length. The window 14A may be formed 
thusly by the configuration of the surfaces of the upper and lower flanges 
abutting thereto or it may be preformed to conform closely with the 
abutting surfaces of the upper and lower flanges. A preferred way of 
making the window mounting flanges, when used to conform the window into 
the desired curved shape is by electrodynamic machining (EDM). 
FIG. 3 illustrates a transmission window embodiment 14B of the present 
invention which presents a preformed curved convex surface to the vacuum 
chamber and which may be mounted between substantially fiat surfaces of 
the upper and lower window flanges. In all of the embodiments of this 
invention the window 14 may be preshaped to be thinner in those regions 
through which the particle beam passes and thicker in those regions 
adjacent to the window securing structure. In the particular embodiment of 
the invention shown in FIG. 3, thinning of those regions of the window 
through which the particle beam passes is an advantageous result of 
certain methods of preshaping, such as drawing down over a forming 
surface, or forming with pressure, vacuum, or intense magnetic field, for 
examples. 
With the new transmission window configuration illustrated in FIG. 1, it is 
therefore practical to reduce the thickness of the window by one half and 
thereby reduce heat dissipation of the window by at least one half over 
that of the conventional fiat window configuration. An additional very 
significant advantage is a substantial reduction (about 50% in this 
example) in angularity of scattering of the electrons as they traverse the 
window. Accelerator power may thereupon be increased to double the maximum 
value permitted by use of a conventional fiat window and still retain an 
additional fifty percent safety margin in window strength. 
Significant improvements in window cooling efficiency may also be realized, 
since forced cooling fluid (gas, mist or liquid) may now be directed 
specifically along the surface of the curved window 14 flowing against and 
guided by the curvature. As shown in FIG. 4, a knife-blade edge nozzle 
arrangement 28 is formed in the lower flange 18 along one edge of the 
curved window 14 and directs cooling fluid flow 29 from a passage 30 
directly against the ambient air side of the window 14 along its entire 
area in a direction transverse to the longitudinal axis along which the 
product strand 11a moves, as denoted by the arrows drawn adjacent to the 
window 14 in FIG. 4. (As also shown in FIG. 4, inside edges 17 of the 
upper flange structure 16 may be slightly curved to provide a forming 
surface for curving the window 14, as desired.) In this embodiment, the 
sheet of cooling fluid should enter the processing chamber tangential to 
the surface of curvature of the window 14 at the region of entry. If the 
sheet is formed and directed too shallowly away from the window, there 
will be dead air space adjacent to the window 14. If the sheet is formed 
and directed too steeply toward the window, excessive turbulence of the 
cooling fluid results. 
A fluid cooled base beam-absorption structure 33 having deep cavities 35 is 
provided below the strand 11a to absorb any stray remnants of the beam 13A 
emitted in the swept and converged ribbon beam generator 10'. 
The structures 10' and 10 shown in FIGS. 4 and 4A manifest an improved 
angle of incidence for, and radial acceleration of, the cooling fluid 
stream 29 relative to the window 14 which has a beneficial effect of 
reducing the boundary layer (Which had been a limiting factor in cooling 
efficiency in prior art fiat window configurations). Improved cooling of 
the transmission window enables use of even higher accelerator power 
levels, since the radiation flux and hence the window power loading may be 
increased with increased cooling efficiency. 
FIG. 4A shows a more structurally detailed view of a preferred arrangement 
for directing the cooling stream 29 against the window 14 in the 
accelerator 10, as applied in a process for irradiating a sheet workpiece 
11b moving in a direction relative to the window 14 as depicted in the 
FIG. 1 diagrammatic view. 
Windows 14 of the configuration shown in FIGS. 4, 4A, 5, 6 and 7 are best 
cooled by causing high velocity cooling fluid (e.g. air) to flow over the 
surface thereof in a direction which is transverse to the axial direction 
of product strand flow. In this manner, the short air cooling path and 
radius yield maximum air velocity while minimizing dispersion and volume 
flow. When this cooling method is practiced within the structure depicted 
in FIGS. 4-7, the cooling air has a minimal effect upon the temperature of 
the product strand passing through the window volume (irradiation zone) 
along the radial axis of the curved window 14, as best shown in FIG. 5. 
The cooling air stream 29 may transport a liquid agent, such as a water 
mist to the outside surface of the window 14, so that the cooling liquid 
evaporates in proximity of the window, thereby absorbing the heat of 
vaporization to achieve additional heat transfer and cooling of the heated 
window. 
Evaporation of the cooling liquid at the window surface also results in a 
volume expansion of cooling gas and resulting turbulence which breaks up 
surface boundary layers which may otherwise form and inhibit cooling 
efficiency. A nozzle arrangement 28 as shown in FIG. 5 may be employed to 
inject water or other liquid, solid or particulate material to be 
processed by exposure to the particle beam, onto the airstream in the 
airflow path 30 and thereby be carried into direct proximity of the 
surface of the window 14. 
Alternatively, droplets of a fluid material may be sprayed on to the window 
by a suitable nozzle structure. In this alternative approach, the nozzle 
structure causes a "cloudburst" of material as fine droplets and directs 
this mist against the transmission window. This spraying technique would 
also increase the load bearing capacity of a prior art fiat transmission 
window. 
Further advantages may be obtained by reduction in the particle beam 
dimensions and by reducing the radius of curvature of the window 14. In 
fact, a preferred species of the present invention is a tubular window as 
depicted in FIG. 8 and discussed hereinafter. These advantages are 
particularly evident in realizing efficient yet smaller sized, lower prime 
cost particle beam accelerators. 
For electron energies over 150 KeV the energy losses of the electron beam 
in the window 14 are reduced, for example, by about 19,000 electron volts 
for each 0.001 inch reduction in thickness of a titanium alloy window, 
wherein titanium is alloyed with vanadium and aluminum. This saving is 
particularly useful in lower energy accelerators, such as those operating 
in a range between about 100 and 500 KeV where the energy loss within the 
window is most significant. 
With reference now to FIG. 5, a modification of the FIG. 1 accelerator 10 
is shown which advantageously promotes self-centering of the strand 11 
relative to the window 14, thereby optimally positioning the strand 11 in 
the path of the particle beam for maximum exposure to the beam. In this 
modified accelerator 10', a region 37 of a modified lower flange 18 
defines a longitudinal well or chamber 32 which oppositely faces the 
window 14. This channel-shaped space 32 enables the laminar airflow sheet, 
depicted by arrows and identified by the reference numeral 34 to form into 
a spiral which surrounds the strand 11 and which creates a low pressure 
area at the nominal axis of the strand 11 and a surrounding high pressure 
area. This flow arrangement for the cooling stream 34 thereby not only 
effectively draws heat off of and away from the curved transmission window 
14, it also promotes centering and proper axial alignment of the workpiece 
11. 
The structural concept depicted in FIG. 5 is extended and presented in 
greater detail in FIGS. 6 and 7. Therein, the base structure 18 is 
provided with a nitrogen or air flowpath 30, and also with a plurality of 
water flow passages 36. The space 32 is defined by a box structure 38 
which is surrounded by the water flow passages 36, so that the box 
structure 38 will be effectively cooled by flow of water or other suitable 
coolant liquid through the flow passages. 
With reference to FIG. 8 a transmission window has been formed as a 
cylindrical tube, as by laser welding along a seam line (not shown). The 
product workpiece, such as the strand 11, is drawn through the inside 
space of the tube, while irradiation from the particle beam, denoted by 
the arrows 13 is directed from an evacuated chamber side of the particle 
beam accelerator, through the thin tubular window 14' and to the strand 
11. 
FIG. 9 shows a mounting arrangement for mounting the tubular window 14' 
between two flanges 50 and 52 which position and secure the tubular window 
14' at opposite end regions thereof. Two threaded nuts 54 and 56 compress 
respectively against the flanges 50 and 52, thereby to lock the tube 
window 14' in place. The flanges 50 and 52 are respectively mounted 
through aligned openings formed in two sidewalls 58 and 60 of a particle 
beam accelerator 62. The particle beam accelerator 62 generates and 
directs particle beams 13 from one or more emitters toward the window 14'. 
An interior space 64 within the particle beam accelerator 62 is highly 
evacuated, whereas the "interior" space defined by the window tube 14' is 
exposed to the ambient environment. One can appreciate by inspection of 
FIGS. 8 and 9 that the tube geometry of the window 14' provides vastly 
reduced hoop stress across the severe pressure gradient from ambient air 
pressure to the highly evacuated interior space 64. 
Cooling of the tube window 14' is an important consideration for its 
success and practicality. Generally speaking, airflow induced under 
pressure may be applied to the interior of the tube 14' and conduct away 
the heat generated as the particle beam passes through the thin window 
material. Also, in this example a cooling liquid, such as a water mist, 
may be injected at the periphery of, and carried by, the pressurized 
airflow to the window surface, thereby to provide additional cooling to 
the window by virtue of the heat of vaporization. Also, the expansion of 
volume resulting from evaporation of the moisture droplets aids in 
breaking up surface boundary layers of gas at the window, thereby 
promoting more intimate contact of the airflow with the window surface to 
be cooled. 
FIG. 10 illustrates an improved cooling arrangement employing a coaxial air 
nozzle structure 66 within a modified threaded nut 54'. The coaxial air 
nozzle structure 66 is disposed within an annular passage 68 defined in 
the modified nut 54'. The passageway 68 communicates with a nipple 70 for 
attachment to a supply of cooling air, typically under a pressure of 30 to 
80 pounds per square inch. The coaxial air nozzle structure provides a 
concentric nozzle annulus throughout its inner annular periphery which is 
directed toward the inside surface of the tubular window 14'. This nozzle 
creates an annular, layered airflow which passes against the tubular 
window 14 at high velocity. Due to a venturi effect experienced .within 
the interior of the tube window 14', some air volume flow amplification 
occurs. Because of this amplification, a low pressure region exists in the 
throat of the window interior which self centers the strand 11 and 
facilitates initially feeding the strand end into and through the window 
(so long as the direction of feed is the same as the direction of laminar 
air flow). 
The tubular window 14' illustrated in FIGS. 8-10 is particularly useful 
within the apparatus described in the referenced commonly assigned U.S. 
Pat. No. 5,051,600. 
Radiation Processing of Window Cooling Material 
For the processing of materials, such as the irradiation of an aqueous 
solution with toxic solutes for the purpose of reduction of the toxic 
materials to less toxic or non-toxic forms, the window cooling air may 
carry or be in part or entirely replaced with a fluid stream or cloudburst 
of mist carrying material to be processed by exposure to the energetic 
particle beam. Thus, if it is desired to facilitate a radiation initiated 
reaction between two separate phases such as a liquid and a gas, the 
liquid may be sprayed or injected into the gas stream impinging on the 
window (for example, in the manner shown in FIG. 5) or a fluid stream with 
bubbles of the gas dispersed therein may be directed against the window. 
The liquid may also be sprayed directly onto the window as fine droplets 
in an atmosphere of the gaseous coreactant. While a liquid medium is 
presently most preferred as a carrier medium for carrying (or comprising) 
the material to be processed, it is clear that particulates and other 
materials to be processed may be injected into a fluid stream provided for 
cooling the transmission window. 
The dimensions of the exit nozzle arrangement, i.e. cooling fluid nozzle 
opening 28 of FIG. 5 or coaxial air nozzle structure 66 of FIG. 10, can be 
spaced so as to establish that the maximum stream thickness flowing over 
the window is appropriate for the penetration depth of the energetic 
particle beam. 
Beam window cooling carried out with a liquid component is much more 
effective than air cooling and therefore permits much higher beam flux 
through the window. With a very high power beam, processing of very large 
amounts of material within a liquid medium or carrier may be achieved 
economically with a relatively low particle energy. Also, by employing a 
thin sheet of liquid-carried material to draw heat away from the 
transmission window, a thicker window may be employed. For example, a 
window formed of 4 mil thick foil may be advantageously employed in the 
liquid materials process. While about 20 kilovolts per mil is lost to 
heating in the window foil, this heat is advantageously transferred to the 
liquid material to be processed. At the same time, a more durable 
transmission window structure is realized by virtue of the increased 
thickness of the window material. Since liquid has a much greater heat 
capacity, and since the window is being cooled by the liquid, rather than 
by airflow, a partial vacuum may be pulled across the liquid side of the 
window which further reduces stresses in the window foil and adds 
robustness and longevity to the window and greater economy to the overall 
liquid process. Thus, as the heat capacity of the cooling fluid increases, 
the useful thickness of the thin window foil may likewise be increased. 
Turning now to FIG. 11, a liquid materials processing particle beam system 
100 includes a housing 101 enclosing a particle beam emitter for emitting 
a particle beam 102 from a source (not shown in this figure). For liquids 
processing the beam 102 most preferably may be deflected; and, it may also 
be deflected and converged in accordance with the teachings of the 
referenced and incorporated, and commonly assigned, co-pending U.S. patent 
application Ser. No. 07/569,329 filed on Aug. 17, 1990, now U.S. Pat. 
5,051,600. 
Alternatively, the beam 102 may be conventionally formed, focused, 
accelerated and deflected without convergence. In any event, the beam 102 
is directed toward and through a curved transmission window 104 of the 
type previously described herein. While a curved transmission window 104 
is presently most preferred, it will be clearly understood by those 
skilled in the art, that more conventional window structures, such as the 
slightly pillowed, nominally flat thin foil transmission windows of the 
prior art, may also be employed with considerably increased efficacy 
within the system 100. If there is a vacuum on both sides of the window, 
then the window can be fiat. 
A liquid manifold 106 provides a supply of liquid 108 to be processed under 
suitable pressure. The liquid 108 from the liquid manifold 106 flows along 
one or more internal passageways 110 toward a knife-blade edge structure 
112 at one longitudinal periphery of the curved transmission window 104. 
The knife-blade edge structure 112 forms and directs the liquid 108 
against the outside of the transmission window 104, thereby coming into 
contact with it and drawing off the heat generated by passage of 
particles, such as electrons, therethrough. At the same time, the beams 
particles efficaciously pass into and process the liquid emanating from 
the knife-blade structure 110, thereby heating the liquid to a suitable 
process temperature and inducing other desired changes, either chemical, 
as with petroleum cracking or chemical reduction of toxic compounds, or 
e.g. polymerization of other liquid materials, etc. 
After passing across the outer surface of the transmission window 104 for 
heat transfer therefrom and for processing, the liquid 108 falls as a 
stream or expanding sheet into a collection vessel 114 defining an 
interior collection space 116. The vessel 114 may advantageously be 
included within, or form a part of, the system housing 101. An outflow 118 
draws the processed and heated liquid 108 out of the collection vessel 
114, either for transfer or collection at a liquid receiver (not shown) or 
for heat exchange and recirculation to the inlet manifold 106, as may be 
desired by a particular process. 
The interior space 116 may be evacuated in order to reduce the pressure 
differential or-gradient across the thin foil transmission window 104. By 
reducing the pressure within the collection vessel space 116 to e.g. about 
5 pounds per square inch, or less, the stresses across the window 104 are 
correspondingly reduced, and the window may be operated at a higher 
temperature, e.g. 350 degrees C., or higher. Particular choices of window 
materials and dimensions including thickness will depend on temperature, 
pressure differential, flow rates, heat capacity, viscosity, corrosiveness 
and other factors of the selected cooling fluid. 
As shown in FIG. 12, the knife blade liquid sheet nozzle structure 112 may 
be positionably secured to an interior shelf 113 within the housing 101. 
Screws 115 may be provided to enable positional adjustment of the moveable 
knife blade structure 112 along a generally horizontal locus denoted by 
the double arrow locus line 117. When the blade assembly 112 is moved to 
the left in FIG. 12, the nozzle sheet orifice becomes smaller, and the 
liquid sheet directed at the thin titanium foil window 104 itself becomes 
correspondingly thinner. Adjustment of the nozzle structure 112 to the 
right widens the nozzle orifice and thickens the sheet of process liquid 
being directed against the curved exterior surface of the window 104. Also 
to be noted in FIG. 12 are the bullnose upper flange 105 and lower 
securement flange 107 which secure the e.g. titanium foil window 104 to 
the housing 101. 
Yet another liquid irradiation and processing system 120 is illustrated 
diagrammatically in FIG. 13. The system 120 takes advantage of the 
elevation of the temperature of the irradiated liquid material in such a 
way that a high energy efficiency may be attained. The system 120 includes 
a housing 122 having insulated sidewalls and a particle beam generator 123 
which emits an energy beam 102 toward and through a thin foil transmission 
window 126, most preferably of the curved configuration discussed 
hereinabove, but which less preferably may be a conventional fiat surface 
transmission window. 
A collection cavity 128 within the housing 122 collects a liquid 130 
undergoing processing within the system 120. Gases and vapors collecting 
in the cavity 128 above the level of the liquid 130 are conducted via a 
pipe 132 to a low temperature vapor condenser 134. The vapor condenser 134 
includes a coolant inlet 151 and a coolant outflow 153 which conducts 
coolant to and from the interior space of the condenser 134 in order to 
provide desired cooling of the vapors and consequent condensation thereof. 
A vacuum pump 136 is provided in series with the cavity 128, pipe 132 and 
vapor condenser 134 so that the cavity 128 is evacuated. Condensed vapors 
are either passed out of the system 120 via a valve 138 to an exit conduit 
140, or the condensate may be returned as a viscosity reducer to a main 
fluid stream via a valve 142 and pipe 143 which communicates with a 
process outflow conduit 144 and flowpath. Advantageously, the process of 
evacuating the vapor portion of the cavity 128 removes e.g. oxygen and 
other reactive gases and vapors from the process thereby preventing such 
gases from interfering with the desired process result. As noted above, a 
still further significant advantage of evacuating the cavity 128 is that 
the reduction in pressure to about 5 psia or less, for example, 
advantageously reduces the axial and transverse .stresses otherwise 
present at the transmission window 126. These lower stresses make it 
possible to operate the process at very high window temperatures, such as 
350 degrees C., or higher, without rupture of the thermally weakened thin 
foil of the window. Not shown in FIG. 13 are other temperature 
heating/cooling controls and structure which may be required or included 
for regulating the temperatures of certain liquid process materials, 
depending-on the particular materials and the desired process 
temperatures. 
A process inlet 146 enables unprocessed liquid, such as highly viscous 
crude oil, to enter a thermally graded heat exchanger section 143 of the 
housing 122. A series of thermally insulative flow baffle plates 147 
separate the interior of the section 143 into a series of thermal stages 
or levels. At the same time, an internal conduit 150 snakes around the 
baffle plates 147 as shown in FIG. 13. 
Fluids such as heavy crude oils may have very high viscosities. To 
accommodate high viscosity of the process liquid material, the conduit 150 
is preferably divided into a series of progressively smaller diameter 
sections, with the largest diameter section 150a being located at a 
lowermost, and coolest level within the graded heat exchanger 143. The 
temperature at the coolest level may be about 28 to 30 degrees C., for 
example. 
A next smaller diameter section 150b of the conduit 150 sinuously snakes 
through a middle, medium temperature portion of the heat exchanger 143 
where the temperatures may range from about 100 to 300 degrees C., for 
example; while a smallest diameter section 146c extends through an 
uppermost, hottest portion of the graded heat exchanger 143 having 
temperatures ranging from 300 to 500 degrees C. After leaving the 
uppermost level, the segment 150c communicates with a knife-blade nozzle 
structure 148 of the type discussed e.g. in conjunction with FIGS. 11 and 
12, for example. In this manner the driving pressure for driving the 
liquid process material through the conduit 150 may be minimized by taking 
advantage of progressive reduction in hydraulic resistance with increasing 
temperature of the material. 
In applications of liquid irradiation and processing systems of the 
invention especially those involving exposure of the window to chemically 
hostile conditions, for example, high temperature liquids or corrosive 
fluids, it is especially advantageous to coat that side of the window in 
contact with the liquid or fluid to be processed with a chemically inert 
or anticorrosion heat resistant coating. Such coatings include thin layers 
of inert metals such as gold and the noble metals, nickel and the like; 
and abrasion resistant ceramic and or other oxide layers, for example, 
anodized surface coats and the like. 
A self contained, transportable fluid process beam system 160 is 
illustrated in FIG. 14. Therein, a conventional tractor 162 and 
semi-trailer contain a system liquid processor 164, power supply 166 and 
operator console 168. The diesel engine of the tractor 162 may be used to 
power a generator to supply primary operating power for the power supply 
166, or a separate generator may be provided. Hoses 170 and 172 
respectively provide an inlet and outlet for material to be processed and 
its carrier fluid medium. 
The transportable system 160 may be made to be very rugged, and safe, with 
necessary radiation shielding, and it may also be made to be used without 
direct human operator supervision and control. The system 160 may thus be 
taken to and used in oil fields for crude oil viscosity reduction and 
local cracking to produce refined products for field use. It may be used 
to lower the hydraulic horsepower required for pumping through pipelines. 
It may be taken to and advantageously employed to reduce or eliminate 
toxic contaminants in waste streams or in potable water supplies. 
In this embodiment of the invention, the particle accelerator is preferably 
an electron accelerator and the electron emitter is preferably an 
elongated electron beam emitter. The particle accelerator preferably 
comprises an all inorganic ion beam focussing and directing structure, for 
example, one formed from metal and ceramic components. Thus, the particle 
beam focussing and directing structure is preferably an all inorganic 
structure, for example, a metal and ceramic ion acceleration tube assembly 
comprising tube sections formed of ceramic and metal, for example, alumina 
ceramic and titanium components conventionally bonded together by heat, 
pressure and suitable fluxes, and containing internal electrodes. These 
sections may be bolted together using metal gasket seals (for example, 
aluminum, copper, or tin wire seals) between the component sections. A 
particular advantage of such structures is that, should a catastrophic 
condition occur, such as a beam window implosion, the tube assembly can be 
disassembled quickly and the components cleaned and baked at a high 
temperature, that is up to 200.degree. C., without harm to the components. 
Preferably the internal electrodes are demountable to facilitate cleaning 
of the components and electrodes. An especially preferred acceleration 
tube assembly is one intended for ion acceleration and is manufactured by 
National Electrostatics Corporation. 
FIG. 15 graphs fluid flow rate as a function of beam power for an electron 
beam liquids processor of fixed window area and employing the fluid flow 
to cool the particle beam window in accordance with the principles of the 
present invention. In the FIG. 15 graph, the electron beam operated in a 
KeV range of 150-400, and the liquid knife gap varied from about 0.005" to 
0.040". Beam scan width varied from about 2 inches to 10 inches. 
FIG. 16 depicts a preferred accelerator unit section, which acts as a beam 
focussing and directing unit. The accelerator unit 200 includes an upper 
flange 201 which mates to the filament flange 202 and a lower flange 203 
which mounts to an upper flange of an extension tube (not shown) or to a 
further accelerator tube section. A series of e.g. 18 annular metal dynode 
rings 204, fused into an assembly with ceramic tube separators 205 (shown 
in greater detail in the enlarged view FIG. 17a) are positioned between 
the flanges 201 and 203 in vacuum sealing relation therewith. Each dynode 
ring 204 includes an inner annular cap portion 206. The box shaped focus 
element 207 is optional, is positioned only within the accelerator unit 
section nearest to the filament flange, and is attached to a selected one 
of the dynode rings in order to be at its potential relative to the 
negative high voltage and chassis ground. In a preferred embodiment the 
interior annular cup shaped portion of each dynode is secured to the outer 
portion thereof by suitable mechanical interlocking fasteners and may be 
readily detached therefrom (e.g. for cleaning) and removed from the 
accelerator unit section. 
The voltage divider network 208 is formed of a series of high volume (10 
megohm, 2 watt carbon composition) resistors which are spiralled around 
the dynode rings 204. Some of the resistors of the network 208 are 
intentionally omitted in FIG. 16 for clarity. The rings 204 have tap 
points 209 which provide a predetermined voltage connection from the 
resistance network 208 to each ring 204. Thus, as the rings 204 extend 
from the top flange 201 to the bottom flange 203, the voltage applied to 
each particular ring is dependent upon the tap location and ranges between 
the minus high voltage applied to one or both of the filament pair and the 
ground potential of the exit window. 
The electron emitter structure 210 includes two holes defined through a 
central region of the flange 202 and they receive two electrical 
feedthrough insulator fittings 211 and 212 which pass electrical 
conductors 213 and 214 leading from the secondary of a toroidal 
transformer 215 to the emitters (not shown). Preferably the emitter 
structure contains two emitters, disposed parallel to each other. They are 
either energized one at a time, the other being used as a spare, or both 
are energized at the same time, with the current in one travelling in the 
opposite direction to that in the other, in order to cancel alternating 
current components of the filament current source. In operation, the beam 
of electrons 221 is accelerated down the tube evacuated core and exits 
towards a transmission window (not shown). 
FIG. 17a illustrates a sectional view of a portion of the accelerator unit 
section 200. One part of the preferred dynode assembly is a removable 
spark gap component 216 installed circumferentially about the fixed 
portion of the dynode ring 204. The fixed dynode ring is integral to the 
vacuum envelope and heat bonded to the ceramic tube sections 205. Each 
adjacent pair of dynode spark gap components comprises a spark gap 217 as 
well as mechanical supports and electrical terminations for the resistor 
assemblies 208 of FIG. 16. 
Another part of the dynode ring 204 is the interior removable cupped 
annular section 2 18. The cupped section of adjacent annular pieces nest 
together to eliminate any line of sight paths between the ceramic 
components 205 and the centrally located beam transmission region. The 
exclusion of line of sight paths is necessary to reduce or eliminate the 
possibility that charged particles from the beam transmission region could 
migrate out of the central region of the tube and settle upon the 
insulating surfaces of the ceramic dynode ring separators eventually 
causing voltage breakdown to occur across the insulator. 
FIG. 17b is a plane view of a cupped annular section and fixed portion of a 
dynode ring further illustrating the interlocking relationships 
therebetween. FIG. 17c shows the details of the interlock design. The 
cupped annular section can be removed by rotating the interior of the 
annulus slightly to align the tabs 219 with a plurality of indents 220 in 
the fixed portion of the dynode ring 204 shown in FIG. 17b and 17c. Thus, 
the cupped annular sections, resistor assemblies and spark gap components 
may be readily removed from within the vacuum envelope assembly and each 
component may be cleaned as necessary with solvents, followed, if desired, 
by heating in an oven to restore it substantially to its original 
condition. 
EXAMPLE 1 
Oil Viscosity Reduction 
A screening test was performed with apparatus similar to the FIG. 11 
apparatus to determine the gross effects of beam dose, dose rate and 
temperature upon the viscous characteristics of oil. The samples 
irradiated were SAE 120 weight gear oil. Using a control viscosity of 100, 
and measuring viscosities of processed oil with a Brookfield viscometer 
using the HB3 spindle and a rotation of 100 RPM, viscosity reductions 
following radiation processing ranged from 93 to 68, with some absolute 
error due to limited quantity of oil. The tests included water spray 
cooling and some under vacuum conditions. At a dose (MRad) of 1.66, the 
viscosity reduced to 93. When the dose was raised to 15 Mrad, the reduced 
viscosities ranged from 83 to 68. A similar test was performed upon 
Venezuelan Heavy Crude with similar results. 
In summary, test results have suggested that reduction of viscosities of 
heavy crude oil from this process yields products which are similar to 
those expected to result from a more conventional petroleum cracking 
process. Essentially no new compounds were noted as a result of this 
process. 
EXAMPLE 2 
Removal of Contaminants from Water 
Water containing 0.1 to 0.3% of various textile dyes is irradiated using 
the liquid processor of FIG. 11 a rate of about 1000 gallons an hour and 
at three minute intervals. Electron beam current is 6 mA at 400 kV. The 
color of the samples is removed after doses up to 150 kGy. 
In similar experiments, water samples containing trace amounts (up to 50 
micrograms per liter) of methylene chloride, chloroform, carbon 
tetrachloride, 1,1,1-trichloroethane, trichloroethylene and 
tetrachloroethylene are irradiated to a dose of less than 10 kGy, 
resulting in essentially complete removal of the contaminants. Similar 
results are obtained with bromodichloromethane, dibromochloromethane, 
bromoform, trans-1,2-dichloroethene, cis-1, 2-dichloroethene, 
1,1-dichloroethene, 1,2-dichloroethane, 1,1,2, 2-tetrachloroethane, 
hexachloroethane, hexachloro-1,3-butadiene, vinyl chloride, benzene, 
toluene, ethylbenzene, o-xylene, m-xylene, pxylene, chlorobenzene, 
1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, dieldrin, 
phenol, o-cresol, m-cresol, p-cresol, dieldrin, polychlorinated benzenes, 
polychlorinated biphenyls, dioxins, chlorine containing dioxins, bromine 
containing dioxins, brominated benzenes, brominated biphenyls, aromatic 
ethers and aromatic polyethers. Thus the processor and the process of the 
invention can be used to remove toxic or polluting materials comprising 
one or more of aliphatic, alkyl-aryl, aryl compounds and organic dyes, 
each of which independently comprises one or more hydroxyl, corbonyl, 
corboxyl, thiol, mercaptan or other sulfur containing moiety, amino, 
imino, amide, imide, nitro, nitroso or halogen groups, such as --F, --Cl, 
--Br and --I, from water or other liquids such as waste streams. 
EXAMPLE 3 
Determination of Window Robustness 
A test is performed to determine the robustness of a liquid cooled window. 
The window is 0.001 inch thick, homogeneous, and composed of a titanium 
alloy (3Al 2.5 V), 12 inches wide. The locus of a curve in cross section 
along an active transverse dimension of the active area of the window has 
a radius of curvature of 1.75 inches. The active transverse dimension of 
the window is 2.94 inches. The flow rate over the window is approximately 
1000 gph. 
To realistically simulate the kind of window power loading expected with a 
high power beam system, the beam scan is turned off leaving the beam as a 
spot on the window having approximately 75% of the beam power concentrated 
in an area of 0.75 square inches. The beam is operated for about 20 
minutes beginning with low power and gradually increasing up to a maximum 
of 5.2 kW (13 mA at 400 kV). This represents a window power loading of 
nearly 350 watts/sq. inch. After the test, the window does show some minor 
discoloration in the very highest flux area (probably well over 500 
watts/sq. inch) suggesting that for these liquid flow conditions (mixed 
turbulent and laminar flows) an upper limit may have been approached. For 
this window, 350 watts/sq. inch corresponds to an energy dissipation in 
the window of over 3 kw/gram, which the windows withstand easily without 
any sign of mechanical failure. Thus the windows of this invention can 
easily handle energy dissipations therein of 600 watts/gram, for example 
750 watts/gram. It is preferred that windows of the invention withstand 
energy dissipations therein of 1000 watts/gram, for example 1500 
watts/gram. More preferably, windows of the invention withstand energy 
dissipations therein of 2000 watts/gram, for example 2500 watts/gram. 
Having thus described an embodiment of the present invention, it will now 
be appreciated that the objects of the invention have been fully achieved, 
and it will be understood by those skilled in the art that many changes in 
construction and widely differing embodiments and applications will 
suggest themselves without departing from the spirit and scope of the 
invention, as particularly defined by the following claims.