U.S. patent application number 12/814912 was filed with the patent office on 2010-09-30 for x-ray window with grid structure.
This patent application is currently assigned to Moxtek, Inc.. Invention is credited to Eric C. Anderson, Keith W. Decker, Raymond T. Perkins, Degao Xu.
Application Number | 20100243895 12/814912 |
Document ID | / |
Family ID | 40087073 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100243895 |
Kind Code |
A1 |
Xu; Degao ; et al. |
September 30, 2010 |
X-RAY WINDOW WITH GRID STRUCTURE
Abstract
A window for a radiation detection system includes a plurality
of intersecting ribs oriented non-perpendicularly with respect to
each other. The plurality of intersecting ribs defines
non-rectangular openings therebetween. A support frame is disposed
around a perimeter of the plurality of intersecting ribs. A film is
disposed over and spans the openings to pass radiation
therethrough. The film and the plurality of intersecting ribs are
integrally formed from a same material including a polymer.
Inventors: |
Xu; Degao; (Provo, UT)
; Anderson; Eric C.; (Taylorsville, UT) ; Decker;
Keith W.; (Pleasant Grove, UT) ; Perkins; Raymond
T.; (Orem, UT) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
P.O. Box 1219
SANDY
UT
84091-1219
US
|
Assignee: |
Moxtek, Inc.
|
Family ID: |
40087073 |
Appl. No.: |
12/814912 |
Filed: |
June 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11756946 |
Jun 1, 2007 |
7737424 |
|
|
12814912 |
|
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Current U.S.
Class: |
250/336.1 ;
250/505.1 |
Current CPC
Class: |
H01J 47/004 20130101;
H01J 5/18 20130101 |
Class at
Publication: |
250/336.1 ;
250/505.1 |
International
Class: |
G21K 1/00 20060101
G21K001/00; G01T 7/00 20060101 G01T007/00 |
Claims
1. A window for a radiation detection system, the window
comprising: a) a plurality of intersecting ribs oriented
non-perpendicularly with respect to each other; b) the plurality of
intersecting ribs defining non-rectangular openings therebetween;
c) a support frame disposed around a perimeter of the plurality of
intersecting ribs; d) a film disposed over and spanning the
openings to pass radiation therethrough; and e) the film and the
plurality of intersecting ribs being integrally formed from a same
material including a polymer.
2. A window as in claim 1, wherein the non-rectangular openings
have a substantially parallelogram shape.
3. A window as in claim 1, wherein at least one corner of each
opening is partially filled with a same material as the plurality
of ribs.
4. A window as in claim 1, wherein the openings are hexagonal.
5. A window as in claim 1, wherein at least one corner of the
openings includes a fillet with a width greater than a width of the
ribs.
6. A window as in claim 1, wherein the plurality of intersecting
ribs, the support frame and the film are integrally formed of the
same material.
7. A window as in claim 1, wherein the plurality of intersecting
ribs comprise silicon, and wherein the film comprises a polymeric
film.
8. A window as in claim 1, wherein each rib comprising the
plurality of intersecting ribs is about less than 100 .mu.m
wide.
9. A window as in claim 1, wherein the plurality of ribs includes a
first set of parallel ribs oriented non-orthogonal with respect to
and intersecting a second set of parallel ribs.
10. A window as in claim 1, further comprising a gas barrier film
layer disposed over the film.
11. A window for a radiation detection system, the window
comprising: a) a plurality of intersecting ribs oriented
non-perpendicularly with respect to each other; b) the plurality of
intersecting ribs defining non-rectangular openings therebetween;
c) the plurality of ribs including at least a first set of parallel
ribs oriented non-perpendicularly with respect to and intersecting
a second set of parallel ribs; d) a support frame disposed around a
perimeter of the plurality of intersecting ribs with ends of the
plurality of intersecting ribs joined to the support frame; e) a
film disposed over and spanning the plurality of intersecting ribs
and openings to pass radiation therethrough; f) the film and the
plurality of intersecting ribs being formed from a same material
including a polymer; g) the film having a thickness less than or
equal to 1 .mu.m; h) each rib of the plurality of ribs having a
width less than 100 .mu.m; and i) the openings forming between 75
and 90% of a total area within a perimeter of the support
frame.
12. A window as in claim 11, wherein the non-rectangular openings
have a substantially parallelogram shape.
13. A window as in claim 11, wherein at least one corner of each
opening is partially filled with a same material as the plurality
of ribs.
14. A window as in claim 11, wherein the openings are
hexagonal.
15. A window as in claim 11, wherein at least one corner of the
openings includes a fillet with a width greater than a width of the
ribs.
16. A window as in claim 11, wherein the plurality of intersecting
ribs, the support frame and the film are integrally formed of the
same material.
17. A window as in claim 11, wherein the plurality of intersecting
ribs comprise silicon, and wherein the film comprises a polymeric
film.
18. A radiation detection system comprising: a) a window to pass
radiation therethrough, the window comprising: i) a plurality of
intersecting ribs oriented non-perpendicularly with respect to each
other; ii) the plurality of intersecting ribs defining
non-rectangular openings therebetween; iii) a support frame
disposed around a perimeter of the plurality of intersecting ribs;
iv) a film disposed over and spanning the plurality of intersecting
ribs and openings to pass radiation therethrough; and v) the film
and the plurality of intersecting ribs being integrally formed from
a same material including a polymer; and b) a sensor disposed
behind the window configured to detect radiation passing through
the window.
19. A radiation detection system as in claim 18, wherein at least
one corner of each opening is partially filled with a same material
as the ribs.
20. A radiation detection system as in claim 18, wherein the
plurality of ribs includes a first set of parallel ribs oriented
non-orthogonal with respect to and intersecting a second set of
parallel ribs.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY
[0001] This is a continuation of U.S. patent application Ser. No.
11/756,946, filed Jun. 1, 2007, now U.S. Pat. No. 7,737,424, which
is herein incorporated by reference.
[0002] This is related to U.S. patent application Ser. No.
12/124,917, filed May 21, 2008, now U.S. Pat. No. 7,709,820, which
is herein incorporated by reference.
[0003] This is related to U.S. patent application Ser. No.
12/783,707, filed May 20, 2010, which is herein incorporated by
reference.
FIELD OF THE INVENTION
[0004] The present invention relates generally to radiation
detection systems and associated high strength radiation detection
windows.
BACKGROUND
[0005] Radiation detection systems are used in connection with
detecting and sensing emitted radiation. Such systems can be used
in connection with electron microscopy, X-ray telescopy, and X-ray
spectroscopy. Radiation detection systems typically include in
their structure a radiation detection window, which can pass
radiation emitted from the radiation source to a radiation detector
or sensor, and can also filter or block undesired radiation.
[0006] Standard radiation detection windows typically comprise a
sheet of material, which is placed over an opening or entrance to
the detector. As a general rule, the thickness of the sheet of
material corresponds directly to the ability of the material to
pass radiation. Accordingly, it is desirable to provide a sheet of
material that is as thin as possible, yet capable of withstanding
pressure resulting from gravity, normal wear and tear, and
differential pressure.
[0007] Since it is desirable to minimize thickness in the sheets of
material used to pass radiation, it is often necessary to support
the thin sheet of material with a support structure. Known support
structures include frames, screens, meshes, ribs, and grids. While
useful for providing support to an often thin and fragile sheet of
material, many support structures can interfere with the passage of
radiation through the sheet of material due to the structure's
geometry, thickness and/or composition. The interference can be the
result of the composition of the material itself and/or the
geometry of the support structure. In addition, many known support
structures have drawbacks. For example, screens and meshes can be
rough and coarse, and thus the overlaid thin film can stretch,
weaken and burst at locations where it contacts the screen or mesh.
A drawback associated with unidirectional ribs is that the ribs can
twist when pressure is applied. This twisting can also cause the
overlaid film to stretch weaken and burst. Unidirectional ribs are
set forth U.S. Pat. No. 4,933,557, which is incorporated herein by
reference. Additionally, there can be substantial difficulty in
manufacturing many known support structures, thus resulting in
increased expense of the support structures and associated
windows.
SUMMARY OF THE INVENTION
[0008] Accordingly, it has been recognized that it would be
advantageous to develop a radiation detection system having a high
strength, yet thin radiation detection window that is economical to
manufacture, and further has the desirable characteristics of being
minimally absorptive and minimizing interference with the passage
of radiation therethrough. It is also desirable to provide a
radiation window having a support structure that will maintain
intact thin films that overlay the support structure.
[0009] Accordingly, the invention provides a window for a radiation
detection system. The window includes a plurality of intersecting
ribs oriented non-perpendicularly with respect to each other. The
plurality of intersecting ribs defines non-rectangular openings
therebetween. A support frame is disposed around a perimeter of the
plurality of intersecting ribs. A film is disposed over and spans
the openings to pass radiation therethrough. The film and the
plurality of intersecting ribs are integrally formed from a same
material including a polymer.
[0010] In addition, the invention provides a window for a radiation
detection system. The window includes a plurality of intersecting
ribs oriented non-perpendicularly with respect to each other. The
plurality of intersecting ribs defines non-rectangular openings
therebetween. The plurality of ribs includes at least a first set
of parallel ribs oriented non-perpendicularly with respect to and
intersecting a second set of parallel ribs. A support frame is
disposed around a perimeter of the plurality of intersecting ribs,
with ends of the plurality of intersecting ribs joined to the
support frame. A film spans the plurality of intersecting ribs and
openings to pass radiation therethrough. The film and the plurality
of intersecting ribs are formed from a same material including a
polymer. The film has a thickness less than or equal to 1 .mu.m.
Each rib of the plurality of ribs has a width less than 100 .mu.m.
The openings form between 75 and 90% of a total area within a
perimeter of the support frame.
[0011] An associated radiation detection system includes a high
strength window as described above and a sensor. The sensor is
configured to detect radiation passing through the high strength
window.
[0012] There has thus been outlined, rather broadly, various
features of the invention so that the detailed description thereof
that follows may be better understood, and so that the present
contribution to the art may be better appreciated. Other features
of the present invention will become clearer from the following
detailed description of the invention, taken together with the
accompanying claims, or may be learned by the practice of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a window in accordance
with an embodiment of the present invention;
[0014] FIG. 2a is a top view of a support grid of the high strength
window of FIG. 1;
[0015] FIG. 2b is a photograph of the support grid of FIG. 2a;
and
[0016] FIG. 3 is a cross-sectional schematic view of an x-ray
detector system in accordance with the present invention with the
window of FIG. 1.
DETAILED DESCRIPTION
[0017] Reference will now be made to the exemplary embodiments
illustrated in the drawings, and specific language will be used
herein to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended. Alterations and further modifications of the inventive
features illustrated herein, and additional applications of the
principles of the inventions as illustrated herein, which would
occur to one skilled in the relevant art and having possession of
this disclosure, are to be considered within the scope of the
invention.
[0018] The present invention provides embodiments pertinent to a
high strength window for a radiation detection system, an
associated radiation detection system, and an associated method of
manufacturing a high strength grid for a window in a radiation
detection system. In accordance with these embodiments, various
details are provided herein which are applicable to all three of
the window, system and method.
[0019] As illustrated in FIGS. 1-2b, a high strength window,
indicated generally at 10, is shown in accordance with an exemplary
embodiment of the present invention. Specifically, the window 10 is
configured for use in connection with a radiation detection system
30 (FIG. 3). The window and associated radiation detection system
can be useful for a variety of applications including those
associated with electron microscopy, X-ray telescopy, and X-ray
spectroscopy. In use, radiation in the form of high energy
electrons and high energy photons (indicated by line 42 in FIG. 3)
can be directed toward the window of the radiation detection
system. The window receives and passes radiation therethrough.
Radiation that is passed through the window reaches a sensor 44
(FIG. 3), which generates a signal based on the type and/or amount
of radiation it receives. The window can be oval, as shown in FIG.
2b.
[0020] As described above, the window 10 can be subjected to a
variety of operating and environmental conditions, including for
example, reduced or elevated pressures, a substantial vacuum,
contamination, etc. Such conditions tend to motivate thicker, more
robust windows. Such radiation detection systems, however, can
potentially be utilized to sense or detect limited or weak sources.
In addition, certain applications require or demand precise
measurements. Such systems or applications tend to motivate thinner
windows. Support ribs can span the window to provide support to
thinner windows. These supports, however, can introduce stress
concentrations into the window due to their structure (such as wire
meshes), have different thermal conductivity than the window and
introduce thermal stress, and can itself interfere with the
radiation directly or even irradiate and introduce noise or errors.
In addition, difficulty can arise in the manufacture of these
supports, thus making these support structures costly and
expensive. Therefore, it has been recognized that it would be
advantageous to develop an economical window that is thin as
possible and as strong as possible and resist introducing noise or
interfering with the radiation.
[0021] The window 10 of the present invention has a plurality of
intersecting ribs 12 defining a grid 18 having openings 20 therein,
and a support frame 14 around a perimeter of the plurality of
intersecting ribs. The support frame carries and supports the ribs.
The window also has a thin film 16 disposed over and spanning the
plurality of intersecting ribs and openings. This film is
configured to pass radiation therethrough.
[0022] The support frame 14 can be made of the same material as the
plurality of ribs 12 defining the grid 18. Accordingly, both the
ribs and support frame can be or include a silicon material,
although this is not required. According to one aspect, the support
frame can be integral with the grid. In this case, both the support
frame and grid can be formed from a single piece of material by
removing or etching the openings 20 in the grid to leave the ribs
joined at their ends to the support frame. Alternatively, the
support frame can form a separate piece that can be coupled to the
grid by an adhesive for example. In another embodiment, the support
frame can be made of a material that is different from the material
comprising the ribs. In addition to providing support for the grid
and the layer of thin polymer film 16, the support frame can be
configured to secure the window 10 to the appropriate location on a
radiation detection system. Each rib comprising the plurality of
intersecting ribs can be less than 100 .mu.m wide.
[0023] The thin film 16 is disposed over and spans the plurality of
ribs 12 and openings 20. The film can be selected to be highly
transmissive of X-rays, for example, and of X-rays having energies
greater than 100 electron volts, while blocking visible light
energy and other unwanted radiation. In addition, the film can be
selected to withstand fluid pressures of up to one atmosphere
(caused by fluids into which the structure may be immersed) without
breaking so that fluid may not penetrate the window.
[0024] The thin film can include a layer of polymer material, such
as poly-vinyl formal (FORMVAR), butvar, parylene, kevlar,
polypropylene, lexan or polyimide. Nonpolymer materials such as
boron, carbon (including cubic amorphous and forms containing
hydrogen), silicon, silicon nitride, silicon carbide, boron
nitride, aluminum and beryllium could also be used. In one aspect,
the film can include doped silicon. Desirably, the film should be
configured to avoid punctures, uneven stretching and localized
weakening. To further reduce the chance of these undesirable
characteristics, the tops of the ribs 12 can be rounded and/or
polished to eliminate sharp corners and rough surfaces.
[0025] The thin film should be thick enough to withstand pressures
to which it will be exposed, such as gravity, normal wear and tear
and the like. However, as thickness of the layer increases so does
undesirable absorption of radiation. If radiation is absorbed by
the layer of thin material, it will not reach the sensor or
detector. This is particularly true with respect to soft X-rays,
which are likely to be absorbed by a thicker film. Therefore, it is
desirable to provide a thin film that is as thin as possible but
sufficiently thick to withstand the pressures explained above. In
one aspect, the film will be able to withstand at least one
atmosphere of pressure, and thus the film can have a thickness
substantially equal to or less than about 1 .mu.m (1000 nm).
[0026] In addition, a gas barrier film layer can be disposed over
the thin film.
[0027] The material comprising the thin film 16 can be different
than the material comprising the intersecting ribs 12 and/or
support frame 14. Alternatively, all three of the thin film
material, ribs and support frame can be or include the same
material. According to one embodiment, the thin film, the support
frame and the intersecting ribs can be integrally formed of the
same material. By way of example, and not by way of limitation,
silicon may be used for this purpose. In another embodiment, the
plurality of intersecting ribs can comprise silicon and the thin
film material can comprise a polymeric film.
[0028] To reduce the chance of damage that can result to the thin
film 16 overlaying the grid 18, the top edges of the intersecting
ribs 12 can be rounded and/or polished to eliminate sharp corners
and rough surfaces which might otherwise cause damage. In one
aspect, forming the ribs from a single crystal of silicon by
etching results in the rounding and polishing action desired.
Alternatively, if other materials and method of construction are
used, the tops of the ribs may require rounding and/or polishing
via known mechanical and/or chemical processes.
[0029] As indicated, the ribs define a grid 18 having openings 20
therein. The ribs terminate substantially in a common plane. The
ribs 12 can include or can be formed entirely of a silicon material
in order to provide a high strength support for the thin film while
being as thin as possible. For example, the height of the ribs can
range from about 100 .mu.m to about 385 .mu.m, and the width of
each rib can be about 60 .mu.m. The ribs are oriented
non-perpendicularly with respect to each other and define
non-rectangular openings. Non-rectangular openings can assume a
variety of different shapes so long as the ribs defining the
openings intersect one another at other than 90 degree angles. The
ribs can include a first set of parallel ribs that intersect and
are oriented non-orthogonally to a second set of parallel ribs.
[0030] According to one embodiment, the openings 20 can be shaped
substantially like a hexagon. The openings can also be shaped in
the form of a trapezoid, such as a parallelogram. This shape can
prevent twisting problems that are commonly associated with
unidirectional line ribs, which experience maximum stress at the
two opposing ends of the longest rib when the window receives a
pressure load. When a window incorporating the unidirectional line
ribs fails it is usually due to breakage at one or both ends of the
longest rib. Mechanical analysis also indicates that many
structures incorporating support ribs will twist when a load is
applied to the window. This twisting action weakens the rib support
structure and the window in general.
[0031] The arrangement of ribs 12 and openings 20 in the grid 18 of
the present invention can minimize or even prevent the twisting
problems experienced in prior teachings. According to one
embodiment, at least one corner of each opening includes a fillet
that is partially filled with a material, such as the same material
as the ribs. By filling the corners, twisting action of the ribs
can be further minimized or eliminated altogether. Filling the
corners also results in an overall increase in strength of the
support grid.
[0032] The material used to fill the corners of the openings 20 and
the material used to form the ribs 12 can be the same. In one
embodiment, this material can be or can include silicon, although
the present invention is not limited to the use of silicon. The
intersecting ribs can be integrally formed from a single piece of
material. Silicon can also be incorporated into this embodiment.
Likewise, the ribs and the filled corners can be formed from a
single piece of silicon material by removing or etching the
openings or cavities to form the interwoven grid 18. The
manufacture of the ribs and filling of corners can occur
substantially simultaneously. Alternatively, the ribs can be formed
first and the corners filled thereafter. In this case, the ribs may
comprise a material that is not the same as the material used to
fill the corners of the openings.
[0033] The result of the geometry of the intersecting ribs 12 in
combination with the filled corners of the openings 20 is that the
tolerant strength of the window 10 is increased. By increasing the
tolerant strength, it is possible to also increase the percentage
of open area within the support frame 14 and/or reduce the overall
height of the ribs, both of which are desirable characteristics
since this they increase the ability of the window to pass
radiation.
[0034] Specifically, in accordance with the present invention, the
openings 20 preferably occupy more area within the perimeter of the
support frame 14 than the plurality of ribs 12 or grid. This is due
to the fact that the openings will typically absorb less radiation
than the surrounding ribs and radiation can more freely pass
through the openings than through the ribs. In one aspect, the
openings take up between about 75% to about 90% of the total area
within the perimeter of the support frame. For example, in one
embodiment the openings in the grid comprise at least about 75% of
the total area within the perimeter of the support frame and the
plurality of ribs comprise no more than about 25% of the total area
within the perimeter support frame. Alternatively, the openings can
comprise at least about 90% of the total area within the support
frame, and the plurality of ribs can comprise no more than about
10% of the total area within the frame.
[0035] In addition to increasing the open area within the support
frame 14, the arrangement of ribs 12 and openings 20 makes it
possible to reduce the height and/or thickness of the ribs, and
thus the collimation required for passing radiation through the
window 10 can be reduced to some degree. By reducing the amount of
collimation required it is possible to increase the amount of
radiation that can pass though the window since the amount of
collimation required is proportional to the amount of radiation
that is absorbed, and therefore not passed through the window.
[0036] Referring to FIG. 3, the window 10 can be part of a
radiation detection system 30. The radiation detection system can
include a high strength window for passing radiation 42
therethrough, which is described in detail in the embodiments set
forth above. The radiation detection system 30 also can include a
sensor 44 disposed behind the window. The sensor can be configured
to detect radiation that passes through the window, and can further
be configured to generate a signal based on the amount and/or type
of radiation detected. The sensor 44 can be operatively coupled to
various signal processing electronics.
[0037] A method of manufacturing a high strength grid for a window
in a radiation detection system includes growing a first oxide
layer on a bare silicon wafer by thermal oxidation. The oxide layer
can then be patterned by traditional lithography techniques. The
plurality of intersecting ribs can be formed by anisotropic etching
of a silicon wafer. Since the silicon etching rate along some
particular planes of single silicon is much faster than other
directions, those silicon beams have super flat side walls. As a
result of the etching, the corners near the ends of those ribs and
the edges between the top and bottom surfaces and side walls of the
ribs can be very sharp and rough. The corners can be rounded and
smoothed.
[0038] It is to be understood that the above-referenced
arrangements are only illustrative of the application for the
principles of the present invention. Numerous modifications and
alternative arrangements can be devised without departing from the
spirit and scope of the present invention. While the present
invention has been shown in the drawings and fully described above
with particularity and detail in connection with what is presently
deemed to be the most practical and preferred embodiment(s) of the
invention, it will be apparent to those of ordinary skill in the
art that numerous modifications can be made without departing from
the principles and concepts of the invention as set forth
herein.
* * * * *