U.S. patent application number 13/214118 was filed with the patent office on 2013-02-21 for system, apparatus and method for deflecting a particle beam.
This patent application is currently assigned to Pyramid Technical Consultants, Inc.. The applicant listed for this patent is Raymond Paul Boisseau, Andrew Dart, John Gordon. Invention is credited to Raymond Paul Boisseau, Andrew Dart, John Gordon.
Application Number | 20130043403 13/214118 |
Document ID | / |
Family ID | 47682803 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130043403 |
Kind Code |
A1 |
Gordon; John ; et
al. |
February 21, 2013 |
SYSTEM, APPARATUS AND METHOD FOR DEFLECTING A PARTICLE BEAM
Abstract
A variety of systems, apparatus and methods for deflecting a
particle beam are described. An apparatus comprises at least six
electromagnetic portions disposed on a plane. Each of the at least
six electromagnetic portions is aligned with a radius emanating
from an axis normal to the plane and is distanced from the axis to
form a volume about the axis. At least six coils are configured for
affecting a dipole magnetic field in the volume in response to
electrical currents applied to physically opposing coils where a
particle beam entering the volume is deflected. Each of the at
least six coils is disposed about a one of the at least six
electromagnetic portions. A yoke structure is configured for
returning a generated magnetic flux.
Inventors: |
Gordon; John; (Henfield,
GB) ; Boisseau; Raymond Paul; (Waltham, MA) ;
Dart; Andrew; (Swampscott, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gordon; John
Boisseau; Raymond Paul
Dart; Andrew |
Henfield
Waltham
Swampscott |
MA
MA |
GB
US
US |
|
|
Assignee: |
Pyramid Technical Consultants,
Inc.
Lexington
MA
|
Family ID: |
47682803 |
Appl. No.: |
13/214118 |
Filed: |
August 19, 2011 |
Current U.S.
Class: |
250/396ML |
Current CPC
Class: |
G21K 1/093 20130101;
A61N 2005/1087 20130101; A61N 5/1043 20130101; H05H 2007/046
20130101 |
Class at
Publication: |
250/396ML |
International
Class: |
H01J 1/50 20060101
H01J001/50 |
Claims
1. An apparatus comprising: at least six electromagnetic portions
disposed on a plane, each of said at least six electromagnetic
portions being aligned with a radius emanating from an axis normal
to said plane and being distanced from said axis to form a volume
about said axis; at least six coils being configured for generating
a dipole magnetic field in said volume in response to electrical
current patterns applied to physically opposing coils, said dipole
magnetic field comprising vectors being generally equal in
magnitude with a same direction of orientation on said plane
traversing said axis, said orientation being rotatable about said
axis in response to a change in said current patterns to deflect a
particle beam entering said volume in a direction away from said
axis, each of said at least six coils being disposed about a one of
said at least six electromagnetic portions; and a yoke structure
being configured for returning a generated magnetic flux.
2. The apparatus as recited in claim 1, in which said at least six
coils are further configured as at least three pairs of physically
opposing coils, each of said at least three pairs being configured
to be excited by a separate electrical current pattern.
3. The apparatus as recited in claim 2, in which said separate
electrical current patterns comprise a sinusoidal component.
4. The apparatus as recited in claim 1, in which tips of said at
least six electromagnetic portions that face said axis are shaped
to affect the dipole magnetic field.
5. The apparatus as recited in claim 1, in which tips of said at
least six electromagnetic portions that face said axis are shaped
to vary the distance from said axis along a length of said tips to
mitigate contact of said tips by said deflected particle beam.
6. The apparatus as recited in claim 1, in which said at least six
electromagnetic portions are distanced from said axis to form a
non-circular surface of said volume to correspond to a non-circular
deflection pattern.
7. The apparatus as recited in claim 2, in which said separate
electrical current patterns comprise a non-sinusoidal component to
produce changes in a shape of the particle beam.
8. The apparatus as recited in claim 1, in which tips of said at
least six electromagnetic portions that face said axis comprise
devices for measuring said dipole magnetic field.
9. The apparatus as recited in claim 1, in which an amount of
electromagnetic portions and an amount of coils is eight.
10. A system comprising: at least six electromagnetic portions
disposed on a plane, each of said at least six electromagnetic
portions being aligned with a radius emanating from an axis normal
to said plane and being distanced from said axis to form a volume
about said axis; at least six coils being configured for generating
a dipole magnetic field in said volume in response to electrical
current patterns applied to physically opposing coils, said dipole
magnetic field comprising vectors being generally equal in
magnitude with a same direction of orientation on said plane
traversing said axis, said orientation being rotatable about said
axis in response to a change in said current patterns to deflect a
particle beam entering said volume in a direction away from said
axis, each of said at least six coils being disposed about a one of
said at least six electromagnetic portions; a yoke structure being
configured for returning a generated magnetic flux; a plurality of
power amplifiers for supplying said electrical current patterns; a
control system for monitoring and controlling operations of said
power amplifiers; and a power supply for powering at least said
power amplifiers and said control system.
11. The system as recited in claim 10, in which said at least six
coils are further configured as at least three pairs of physically
opposing coils, each of said at least three pairs being configured
to be excited by a separate one of said plurality of power
amplifiers.
12. The system as recited in claim 11, in which said separate
electrical current patterns comprise a sinusoidal component.
13. The system as recited in claim 10, in which tips of said at
least six electromagnetic portions that face said axis are shaped
to affect the dipole magnetic field.
14. The system as recited in claim 10, in which tips of said at
least six electromagnetic portions that face said axis are shaped
to vary the distance from said axis along a length of said tips to
mitigate contact of said tips by said deflected particle beam.
15. The system as recited in claim 10, in which said at least six
electromagnetic portions are distanced from said axis to form a
non-circular surface of said volume to correspond to a non-circular
deflection pattern.
16. The system as recited in claim 11, in which said separate
electrical current patterns further comprise a non-sinusoidal
component to produce changes in a shape of the particle beam.
17. The system as recited in claim 10, in which tips of said at
least six electromagnetic portions that face said axis comprise
devices for feedback to said control system.
18. The system as recited in claim 10, in which said at least six
coils are further configured for generating said dipole magnetic
field for use in particle therapy.
19. A method comprising steps of: arranging at least six
electromagnetic portions of a multi-pole electromagnet to be
disposed on a plane where each of said at least six electromagnetic
portions are aligned with a radius emanating from an axis normal to
said plane and are distanced from said axis to form a volume about
said axis; configuring at least six coils for generating a dipole
magnetic field in said volume in response to electrical current
patterns comprising sinusoidal components being applied to
physically opposing coils, said dipole magnetic field comprising
vectors being generally equal in magnitude with a same direction of
orientation on said plane traversing said axis, said orientation
being rotatable about said axis in response to a change in said
current patterns; and exciting said at least six coils with said
current patterns for rotating said dipole magnetic field to deflect
a particle beam entering said volume to a desired position away
from said axis.
20. The method as recited in claim 19, further comprising the step
of applying a component to said electrical current patterns to
shape the particle beam.
Description
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] Not applicable.
REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER LISTING
APPENDIX
[0002] Not applicable.
COPYRIGHT NOTICE
[0003] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or patent disclosure as it appears in the
Patent and Trademark Office, patent file or records, but otherwise
reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
[0004] The present invention relates generally to implementations
of electromagnetic apparatus. More particularly, the invention
relates to delivering a charged particle beam to arbitrary points
in a region, such as for particle therapy in medical
applications.
BACKGROUND OF THE INVENTION
[0005] Many applications, including medical therapy and
diagnostics, semiconductor processing and industrial radiography
require beams of particles to be directed to particular positions
with good accuracy, and with repeatable and timely control. A
particular application where accurate scanning and positioning of
high energy particle beams may be required is particle therapy. For
particle therapy, beams of high energy charged particles, most
often protons, but also heavier ions such as ionized carbon, oxygen
and argon, may be used to deliver a therapeutic dose. Particle
therapy may offers improvements over more conventional X-ray
therapy by being able to deliver a dose much more precisely to a
region within the body and with reduced unwanted damage to healthy
tissues surrounding the region.
[0006] A method of particle beam therapy providing precise control
and the ability to deliver a dose to the most complex volumetric
shapes is pencil beam scanning. For pencil beam scanning, a narrow
beam of mono-energetic particles may be deflected by controlled
amounts so as to describe a pattern in space. For pencil beam
scanning, angular deflection is typically less than ten degrees. In
combination with modulation of the beam intensity and sequential
delivery of patterns at different beam energies, a desired dose
distribution may be achieved. Several such exposures may be
performed over a period of days or weeks in order to complete a
treatment plan.
[0007] A component of a pencil beam scanning system is the
electromagnets that deflect the beam to the desired trajectory.
These electromagnets may require timely magnetic field changes in
order to develop a desired pattern without experiencing undue
periods of time for the magnetic field to settle. These
electromagnets may be required to deliver good ion optical
qualities over the scanned portions in order to avoid disruption of
the beam shape. These electromagnets should not occupy excessive
space in the trajectory of the beam, as this may translate into a
larger system, potentially higher costs, and may preclude the
installation of systems in some locations. In order to support a
broad array of treatments, the electromagnets should not impose
arbitrary constraints for how the beam trajectory may be
manipulated.
[0008] FIG. 1 presents an example illustration of a conventional
electromagnetic apparatus for deflecting a charged particle
beam.
[0009] A deflecting mechanism 100 includes a horizontal
electromagnetic portion 102 and a vertical electromagnetic portion
104. The terms horizontal and vertical are used for convenience
only and do not represent actual positions.
[0010] Deflecting mechanism 100 may operate to deflect the
trajectory of a charged particle 106 in the horizontal direction
via horizontal electromagnetic portion 102 and in the vertical
direction via vertical electromagnetic portion 104. Not shown is a
typical yoke for returning magnetic flux from portions 102 and
104.
[0011] Horizontal electromagnetic portion 102 may operate to
generate a magnetic field in the vertical direction and vertical
electromagnetic portion 104 may operate to generate a magnetic
field in the horizontal direction.
[0012] Charged particle 106 may initially be moving in the
direction of an axis 108. After transitioning through horizontal
electromagnetic portion 102 and vertical electromagnetic portion
104, charged particle 106 may be moving in a different trajectory
as denoted by a trajectory 110.
[0013] High quality dipole fields, with minimal higher order
components, may be established via simple designs as illustrated in
FIG. 1. Furthermore, beam aberrations introduced by the
electromagnetic portions may be considered small. The operation of
the two electromagnetic portions may be distinct. For example,
horizontal electromagnetic portion 102 may have an air gap 112
where the magnetic field generated may be slightly greater than the
dimension of the received beam of particles. In contrast, vertical
electromagnetic portion 104 may have an air gap 114 which has a
larger separation distance than exhibited by air gap 112 in order
to accommodate the range of deflections generated by horizontal
electromagnetic portion 102. Furthermore, the increased separation
distance require for air gap 114 may require additional amp-turns
for an energizing circuit 116 and may translate into a slower beam
movement in the vertical direction generated via vertical
electromagnetic portion 104. The increased air gap and increased
amp-turns may result in more complexity for planning the map of
potential beam positions due to differing speed of response of the
in the horizontal and vertical axes. Furthermore, the conventional
deflection apparatus, as illustrated in FIG. 1, may require an
apparatus occupying increased space, which may be considered a
premium for many systems.
[0014] FIG. 2 presents an example illustration of a conventional
method and means for deflecting a charged particle using an
electromagnetic apparatus.
[0015] A deflecting mechanism 200 includes a horizontal
electromagnetic portion 202 and a vertical electromagnetic portion
204.
[0016] Deflecting mechanism 200 may operate to deflect the
trajectory of a charged particle 206 in the horizontal direction
via horizontal electromagnetic portion 202 and in the vertical
direction via vertical electromagnetic portion 204. Horizontal
electromagnetic portion 202 and vertical electromagnetic portion
204 may be configured as a quadrupole structure.
[0017] Horizontal electromagnetic portion 202 may operate to
generate a magnetic field in the vertical direction and vertical
electromagnetic portion 204 may operate to generate a magnetic
field in the horizontal direction.
[0018] Charged particle 206 may initially be moving in the
direction of an axis 208. After transitioning through horizontal
electromagnetic portion 202 and vertical electromagnetic portion
204, charged particle 206 may be moving in a different trajectory
as denoted by a trajectory 210.
[0019] The physical size for a two dipole design as illustrated in
FIG. 1 may be reduced by superimposing the vertical and horizontal
electromagnetic portions to create a quadrupole structure as
illustrated in FIG. 2. The excitation of the electromagnetic
portions for the quadrupole as illustrated in FIG. 2 may be
dissimilar from that of a conventional beam focusing quadrupole. A
conventional beam focusing quadrupole may be configured with four
coils and a single power supply, with the direction of the current
flow through the coils arranged to generate a zero magnetic field
on the central axis of the magnetic air gap and a linearly
increasing magnetic field with increased displacement from the
central axis to shape the beam cross-section.
[0020] The superimposed dipole as illustrated with reference to
FIG. 2 may be configured with two independent power supplies with
one power supply associated with an opposed electromagnetic
portion. The resultant magnetic field for the superimposed dipole
may be considered as a vector sum of the fields of the two
individual dipoles associated with the composite structure. The
superimposed deflection apparatus may be controlled similar to two
independent dipoles with one deflecting in the horizontal direction
and one deflecting in the vertical direction. A square
configuration for the electromagnetic portions is common, as other
structures and configurations may result in a poor quality dipole
magnetic field associated with the central axis and may also result
in large pole spacing. However, even a square configuration for the
superimposed dipole may result in a magnetic field which may be of
considerably less quality than realized with equivalent separate
dipoles as illustrated with reference to FIG. 1. Furthermore, as a
result of the less quality magnetic field generated by the
superimposed dipole, beam aberrations may be experienced.
[0021] In view of the foregoing, there is a need for improved
techniques for electromagnets associated with deflecting charged
particle beams.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present invention is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings and in which like reference numerals refer to similar
elements and in which:
[0023] FIG. 1 presents an example illustration of a conventional
electromagnetic apparatus for deflecting a charged particle
beam;
[0024] FIG. 2 presents an example illustration of a conventional
method and means for deflecting a charged particle using an
electromagnetic apparatus;
[0025] FIG. 3 presents an illustration of an example multi-pole
deflection apparatus for deflecting a charged particle, in
accordance with an embodiment of the present invention;
[0026] FIG. 4 presents a cross-section illustration of an example
sextupole deflection apparatus for deflecting a charged particle,
in accordance with an embodiment of the present invention;
[0027] FIG. 5 presents a cross-section illustration of an example
octupole deflection apparatus for deflecting a charged particle, in
accordance with an embodiment of the present invention;
[0028] FIG. 6 presents a geometrical illustration for calculating
coil currents for an example n-pole deflection apparatus for
deflecting a charged particle, in accordance with an embodiment of
the present invention;
[0029] FIG. 7 presents an example illustration of traverse plane
magnetic field vectors associated with the bore of a multi-pole
electromagnetic apparatus, in accordance with an embodiment of the
present invention;
[0030] FIG. 8 presents an example illustration of an
electromagnetic portion deflecting a beam of charged particles and
the orientation of the charged particles with respect to a
downstream plane, in accordance with an embodiment of the present
invention;
[0031] FIG. 9 presents a cross-section illustration of an example
multi-pole deflection apparatus with modified pole tips for
improving the quality of the associated dipole magnetic field for
deflecting a charged particle, in accordance with an embodiment of
the present invention;
[0032] FIG. 10 presents an illustration of an example multi-pole
deflection apparatus with modified air gaps between poles for
providing greater clearance for a charged particle beam as it
deflects into a magnetic dipole field, in accordance with an
embodiment of the present invention;
[0033] FIG. 11 presents a cross-section illustration of an example
multi-pole deflection apparatus with a non-circular bore, in
accordance with an embodiment of the present invention; and
[0034] FIG. 12 presents a cross-section illustration of an example
multi-pole deflection apparatus incorporating a Hall effect probe
to provide magnet field feedback for monitoring and control, in
accordance with an embodiment of the present invention.
[0035] Unless otherwise indicated illustrations in the figures are
not necessarily drawn to scale.
SUMMARY OF THE INVENTION
[0036] To achieve the forgoing and other objects and in accordance
with the purpose of the invention, a variety of systems, apparatus
and methods for deflecting a particle beam are described.
[0037] In one embodiment an apparatus comprises at least six
electromagnetic portions disposed on a plane. Each of the at least
six electromagnetic portions is aligned with a radius emanating
from an axis normal to the plane and is distanced from the axis to
form a volume about the axis. At least six coils are configured for
affecting a dipole magnetic field in the volume in response to
electrical currents applied to physically opposing coils where a
particle beam entering the volume is deflected. Each of the at
least six coils is disposed about a one of the at least six
electromagnetic portions. A yoke structure is configured for
returning a generated magnetic flux. In another embodiment the at
least six coils are further configured as at least three pairs of
physically opposing coils, each of the at least three pairs being
configured to be excited by a separate electrical current source.
In yet another embodiment the separate electrical current sources
comprise a component comprising a function of an angle of a pole
and a deflection angle. In still another embodiment tips of the at
least six electromagnetic portions that face the axis are shaped to
affect the dipole magnetic field. In another embodiment tips of the
at least six electromagnetic portions that face the axis are shaped
to vary the distance along the tip from the axis. In yet another
embodiment the at least six electromagnetic portions are distanced
from the axis to form a non-circular surface of the volume. In
still another embodiment the separate electrical current sources
comprise superimposed patterns to produce changes in a shape of the
particle beam. In another embodiment tips of the at least six
electromagnetic portions that face the axis comprise devices for
measuring the dipole magnetic field. In yet another embodiment an
amount of electromagnetic portions and an amount of coils is
eight.
[0038] In another embodiment a system comprises at least six
electromagnetic portions disposed on a plane. Each of the at least
six electromagnetic portions is aligned with a radius emanating
from an axis normal to the plane and is distanced from the axis to
form a volume about the axis. At least six coils are configured for
affecting a dipole magnetic field in the volume in response to
electrical currents applied to physically opposing coils where a
particle beam entering the volume is deflected. Each of the at
least six coils is disposed about a one of the at least six
electromagnetic portions. A yoke structure is configured for
returning a generated magnetic flux. A plurality of power
amplifiers supplies the electrical currents. A control system
monitors and controls operations of the power amplifiers. A power
supply powers at least the power amplifiers and the control system.
In another embodiment the at least six coils are further configured
as at least three pairs of physically opposing coils. Each of the
at least three pairs is configured to be excited by a separate one
of the plurality of power amplifiers. In yet another embodiment the
separate electrical current sources comprise a component comprising
a function of an angle of a pole and a deflection angle. In still
another embodiment tips of the at least six electromagnetic
portions that face the axis are shaped to affect the dipole
magnetic field. In another embodiment tips of the at least six
electromagnetic portions that face the axis are shaped to vary the
distance along the tip from the axis. In yet another embodiment the
at least six electromagnetic portions are distanced from the axis
to form a non-circular surface of the volume. In still another
embodiment the separate electrical current sources comprise
superimposed patterns to produce changes in a shape of the particle
beam. In another embodiment tips of the at least six
electromagnetic portions that face the axis comprise devices for
feedback to the control system. In yet another embodiment the at
least six coils are further configured for affecting the dipole
magnetic field for use in particle therapy.
[0039] In another embodiment a method comprises steps of arranging
at least six electromagnetic portions of a multi-pole electromagnet
to be disposed on a plane where each of the at least six
electromagnetic portions are aligned with a radius emanating from
an axis normal to the plane and are distanced from the axis to form
a volume about the axis. The method comprises the step of
configuring at least six coils for affecting a dipole magnetic
field in the volume in response to electrical currents applied to
physically opposing coils. The method comprises the step of
exciting the at least six coils with electrical currents for
rotating the dipole magnetic field to deflect a particle beam
entering the volume to a desired position. Another embodiment
further comprises the step of applying a component to the
electrical currents to shape the particle beam.
[0040] Other features, advantages, and objects of the present
invention will become more apparent and be more readily understood
from the following detailed description, which should be read in
conjunction with the accompanying drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] The present invention is best understood by reference to the
detailed figures and description set forth herein.
[0042] Embodiments of the invention are discussed below with
reference to the Figures. However, those skilled in the art will
readily appreciate that the detailed description given herein with
respect to these figures is for explanatory purposes as the
invention extends beyond these limited embodiments. For example, it
should be appreciated that those skilled in the art will, in light
of the teachings of the present invention, recognize a multiplicity
of alternate and suitable approaches, depending upon the needs of
the particular application, to implement the functionality of any
given detail described herein, beyond the particular implementation
choices in the following embodiments described and shown. That is,
there are numerous modifications and variations of the invention
that are too numerous to be listed but that all fit within the
scope of the invention. Also, singular words should be read as
plural and vice versa and masculine as feminine and vice versa,
where appropriate, and alternative embodiments do not necessarily
imply that the two are mutually exclusive.
[0043] It is to be further understood that the present invention is
not limited to the particular methodology, compounds, materials,
manufacturing techniques, uses, and applications, described herein,
as these may vary. It is also to be understood that the terminology
used herein is used for the purpose of describing particular
embodiments only, and is not intended to limit the scope of the
present invention. It must be noted that as used herein and in the
appended claims, the singular forms "a," "an," and "the" include
the plural reference unless the context clearly dictates otherwise.
Thus, for example, a reference to "an element" is a reference to
one or more elements and includes equivalents thereof known to
those skilled in the art. Similarly, for another example, a
reference to "a step" or "a means" is a reference to one or more
steps or means and may include sub-steps and subservient means. All
conjunctions used are to be understood in the most inclusive sense
possible. Thus, the word "or" should be understood as having the
definition of a logical "or" rather than that of a logical
"exclusive or" unless the context clearly necessitates otherwise.
Structures described herein are to be understood also to refer to
functional equivalents of such structures. Language that may be
construed to express approximation should be so understood unless
the context clearly dictates otherwise.
[0044] Unless defined otherwise, all technical and scientific terms
used herein have the same meanings as commonly understood by one of
ordinary skill in the art to which this invention belongs.
Preferred methods, techniques, devices, and materials are
described, although any methods, techniques, devices, or materials
similar or equivalent to those described herein may be used in the
practice or testing of the present invention. Structures described
herein are to be understood also to refer to functional equivalents
of such structures. The present invention will now be described in
detail with reference to embodiments thereof as illustrated in the
accompanying drawings.
[0045] From reading the present disclosure, other variations and
modifications will be apparent to persons skilled in the art. Such
variations and modifications may involve equivalent and other
features which are already known in the art, and which may be used
instead of or in addition to features already described herein.
[0046] Although Claims have been formulated in this Application to
particular combinations of features, it should be understood that
the scope of the disclosure of the present invention also includes
any novel feature or any novel combination of features disclosed
herein either explicitly or implicitly or any generalization
thereof, whether or not it relates to the same invention as
presently claimed in any Claim and whether or not it mitigates any
or all of the same technical problems as does the present
invention.
[0047] Features which are described in the context of separate
embodiments may also be provided in combination in a single
embodiment. Conversely, various features which are, for brevity,
described in the context of a single embodiment, may also be
provided separately or in any suitable subcombination. The
Applicants hereby give notice that new Claims may be formulated to
such features and/or combinations of such features during the
prosecution of the present Application or of any further
Application derived therefrom.
[0048] As is well known to those skilled in the art many careful
considerations and compromises typically must be made when
designing for the optimal manufacture of a commercial
implementation any system, and in particular, the embodiments of
the present invention. A commercial implementation in accordance
with the spirit and teachings of the present invention may
configured according to the needs of the particular application,
whereby any aspect(s), feature(s), function(s), result(s),
component(s), approach(es), or step(s) of the teachings related to
any described embodiment of the present invention may be suitably
omitted, included, adapted, mixed and matched, or improved and/or
optimized by those skilled in the art, using their average skills
and known techniques, to achieve the desired implementation that
addresses the needs of the particular application.
[0049] Detailed descriptions of the preferred embodiments are
provided herein. It is to be understood, however, that the present
invention may be embodied in various forms. Therefore, specific
details disclosed herein are not to be interpreted as limiting, but
rather as a basis for the claims and as a representative basis for
teaching one skilled in the art to employ the present invention in
virtually any appropriately detailed system, structure or
manner.
[0050] It is to be understood that any exact
measurements/dimensions or particular construction materials
indicated herein are solely provided as examples of suitable
configurations and are not intended to be limiting in any way.
Depending on the needs of the particular application, those skilled
in the art will readily recognize, in light of the following
teachings, a multiplicity of suitable alternative implementation
details.
[0051] Embodiments of the present invention will be described which
provide means and methods for delivering a charged particle beam to
arbitrary points in a region controlled by small angle deflection
of the charged particle beam. A non-limiting example of an
application for deflection and delivery of a charged particle beam
includes particle therapy associated with the practice of medicine.
A multi-pole electromagnet when disposed with an appropriate
excitation may operate to steer a charged particle beam with energy
in a typical range of 60 MeV to 6 GeV, via a sequence of
trajectories in order to deliver an ion beam to desired positions
located in a transverse surface located at a distance from the
electromagnet. The multi-pole electromagnet may be connected to a
multiplicity of power amplifiers. The power amplifiers may be
connected to opposing coils associated with the multi-pole
electromagnet. Furthermore, the multiplicity of power amplifiers
may be connected to a power supply. As an example associated with
particle beam therapy, the control of particle beam position
combined with kinetic energy adjustment may operate to control the
lateral distribution and range of particles projected into a body.
Furthermore, modulation of the particle beam intensity may allow a
desired volumetric dose distribution to be delivered. The
multi-pole electromagnet, via appropriate currents applied to the
coils of the electromagnetic, may operate to position a charged
particle beam at a location associated with a traverse plane
defined in polar coordinates as R and .theta.. For sinusoidal
currents applied to six or more coils as a function of the pole
angles, the resulting magnetic field created between the coils may
provide a good quality dipole magnetic field which can be rotated
to any arbitrary angle. Furthermore, the size of associated
electromagnets may be reduced, and higher quality beams may be
produced as compared to conventional means and methods.
[0052] In other embodiments of the present invention, methods and
means will be described for providing a multi-pole electromagnet
with modified tips for improving the quality of the generated
magnetic field. The modified tips may be configured with various
geometric shapes. Non-limiting examples of geometric shapes include
circular and elliptical.
[0053] In other embodiments of the present invention, methods and
means will be described for providing a multi-pole electromagnet
with modified air gaps for providing greater clearance for a
charged particle beam, resulting in less likelihood of sustaining
particle beam losses.
[0054] In other embodiments of the present invention, methods and
means will be described for providing magnetic field probes for
providing feedback in order to support systems operating with
non-linear configurations.
[0055] FIG. 3 presents an illustration of an example multi-pole
deflection apparatus for deflecting a charged particle, in
accordance with an embodiment of the present invention.
[0056] A multi-pole deflection apparatus 300 may operate to deflect
a received charged particle via a generated magnetic field. For
simplicity, a yoke for magnetic flux return is not shown.
[0057] Multi-pole deflection apparatus 300 includes an
electromagnetic portion 302, an electromagnetic portion 304, an
electromagnetic portion 306, an electromagnetic portion 308, an
electromagnetic portion 310, an electromagnetic portion 312, an
electromagnetic portion 314, an electromagnetic portion 316, an
amplifier 318, an amplifier 320, an amplifier 322, an amplifier 324
and a power supply 326. As a non-limiting example, power supply 326
may be configured as Direct Current (DC).
[0058] Electromagnetic portions 302, 304, 306, 308, 310, 312, 314
and 316 may operate to generate an associated magnetic field.
Amplifier 318, 320, 322, 324 may operate to provide amplified
power. Power supply 326 may operate to provide electrical
power.
[0059] The electromagnetic portions may be configured in a circular
fashion about a z-axis 328.
[0060] A first node of electromagnetic portion 310 may be connected
to a first node of amplifier 318 via a conductor 330. A second node
of electromagnetic portion 310 may be connected to a first node of
electromagnetic portion 302 via a conductor 332. A second node of
electromagnetic portion 302 may be connected to a second node of
amplifier 318 via a conductor 334. Electromagnetic portion 302 and
electromagnetic portion 310 may be configured as physically
opposing.
[0061] Electromagnetic portions 302, 304, 306, 308, 310, 312, 314
and 316 may be configured and connected (not shown) to amplifiers
320, 322 and 324 in a similar fashion as described previously with
reference to electromagnetic portion 302, 310, amplifier 318 and
conductors 330, 332 and 334.
[0062] Amplifiers 318, 320, 322 and 324 may be connected to power
supply 326 via a power conduit 336.
[0063] A charged particle 338 may initially be moving in the
direction of z-axis 328. After transitioning through
electromagnetic portions 302, 304, 306, 308, 310, 312, 314 and 316
and subjected to a dipole magnetic field located in the central
channel of multi-pole deflection apparatus 300, charged particle
338 may be moving in a different trajectory as denoted by a
trajectory 340.
[0064] The operation of multi-pole deflection apparatus 300 with
appropriated electrical currents traversing the coils of
electromagnetic portions 302, 304, 306, 308, 310, 312, 314 and 316
may provide a high quality dipole magnetic field.
[0065] For the number of electromagnetic portions six or greater
and a pattern of currents with an associated sinusoidal function of
the pole angles, a high quality dipole magnetic field may be
created which can be rotated to any angle.
[0066] The present invention combines the small physical size of
the quadrupole structure as illustrated with reference to FIG. 2
and the high quality magnetic field of the dipole pair as
illustrated with reference to FIG. 1.
[0067] FIG. 4 presents a cross-section illustration of an example
sextupole deflection apparatus for deflecting a charged particle,
in accordance with an embodiment of the present invention.
[0068] A sextupole deflection apparatus 400 includes six
electromagnetic portions with a sampling denoted as an
electromagnetic portion 402, six coils with a sampling denoted as a
coil 404 and a yoke structure 406. Non-limiting examples of
materials for constructing yoke structure 406 include iron and
steel.
[0069] The six electromagnetic portions may be arranged in a circle
about a central axis 408. Magnetization may be produced by applying
electrical currents to electrical coils for opposing
electromagnetic portions using three independent power amplifiers
(connections between coils and amplifiers not shown). A desired
dipole magnetic field may be created in the region enclosed by the
electromagnetic portions. The created magnetic flux may be returned
via yoke structure 406.
[0070] FIG. 5 presents a cross-section illustration of an example
octupole] deflection apparatus for deflecting a charged particle,
in accordance with an embodiment of the present invention.
[0071] An octupole deflection apparatus 500 includes eight
electromagnetic portions with a sampling denoted as an
electromagnetic portion 502, eight coils with a sampling denoted as
a coil 504 and a yoke structure 506. Non-limiting examples of
materials for constructing yoke structure 506 include iron and
steel.
[0072] The eight electromagnetic portions may be arranged in a
circle about a central axis 508. Magnetization may be produced by
applying electrical currents to electrical coils for opposing
electromagnetic portions using four independent power amplifiers
(connections between coils and amplifiers not shown). A desired
dipole magnetic field may be created in the region enclosed by the
electromagnetic portions. The created magnetic flux may be returned
via yoke structure 506.
[0073] The dipole magnetic quality increases with the number of
electromagnetic portions, but so does the complexity of the
apparatus (e.g. number of power amplifiers required--one for every
opposing electromagnetic portion). Common applications for the
present invention may be configured with six or eight
electromagnetic portions.
[0074] FIG. 6 presents a geometrical illustration for calculating
coil currents for an example n-pole deflection apparatus for
deflecting a charged particle, in accordance with an embodiment of
the present invention.
[0075] A deflection apparatus 600 includes n electromagnetic
portions with a sampling denoted as an electromagnetic portion 602,
an electromagnetic portion 604, an electromagnetic portion 606 and
an electromagnetic portion 608.
[0076] The excitation pattern for the associated coils of the
electromagnetic portions for deflection apparatus 600 for steering
a charged particle via a high quality dipole field may be explained
with reference to FIG. 6.
[0077] The electromagnetic portions may be configured in a circle
about a z-axis 610 with z-axis 610 projected into the page.
Furthermore, electromagnetic portions may be configured with
respect to an x-axis 612 directed to the left with respect to the
page and a y-axis 614 directed vertically upwards with respect to
the page.
[0078] A charged particle (not shown) may enter deflection
apparatus 600 parallel and in close proximity to z-axis 610.
Magnetic poles, denoted as P.sub.k, k=1 to n, associated with n
magnetic portions may be arranged in a circular array at angles,
denoted as A.sub.k, with respect to x-axis 612. A positive charged
particle deflection angle, denoted as an angle 616, resulting from
a uniform dipole field 618 may be generated by coil currents
denoted as I.sub.k, k=1 to n/2.
[0079] The zero degrees direction of particle deflection may be
taken to be along x-axis 612. Angle 616 may be considered as the
direction of deflection relative to zero degrees with respect to
x-axis 612. A deflection for a positive ion with a value of 0
degrees for angle 616 may be associated with magnetic field vectors
for uniform dipole field 618 rotated from the arbitrary angle
illustrated so that they are pointing from the top of the page to
the bottom of the page and positioned in the plane of the page.
Furthermore, the n magnetic poles P.sub.k, k=1 to n, may be
arranged in a circular array with an even value for n. Furthermore,
the first n/2 magnetic pole tips may be centered at angles A.sub.k,
k=1 to n/2, with an increasing positive angle denoted in the
clockwise direction. Furthermore, corresponding opposing magnetic
portions may be positioned at A.sub.k+180 degrees. Furthermore,
every opposing pole pair may be powered by a single power amplifier
whereby coils may be connected in series such that the same
electrical current may traverse the coil pairs. Furthermore, the
operation may be considered similar as in the case of a
conventional magnetic dipole deflection apparatus. For purposes of
explanation and as a non-limiting example, the magnetic poles and
coils may be identical and arranged at regular angles starting from
zero degrees, however, any known configuration may be
considered.
[0080] A regular distribution of magnetic poles about z-axis 610
may operate to generate a high quality magnetic field. To generate
a particular dipole magnetic field for deflecting a charged
particle zero degrees for angle 616, the exciting currents I.sub.k,
k=1 to n/2 may be represented by Equation (1) as shown below:
I.sub.k=I.sub.p*sin(-A.sub.k) (1)
[0081] For Equation (1), I.sub.p may represent a particular
electrical current determining an amount of deflection to be
applied in the direction associated with the magnetic pole. A
positive value for the electrical current for I.sub.p may be
associated with a clockwise flow of electrical current when viewing
a magnetic portion from z-axis 610. A negative value for I.sub.p
may be associated with a counter-clockwise flow of electrical
current when viewing a magnetic portion from z-axis 610.
Furthermore, a coil for a pole may be considered as similar and
connected in series with a coil 180 degrees opposed, in a fashion
similar to a conventional dipole magnet. In order to rotate the
dipole magnetic field direction for producing a deflection in
another direction .theta., the excitation for I.sub.k, k=1 to n/2
may be represented as Equation (2) as shown below:
I.sub.k=I.sub.p*sin(.theta.-A.sub.k) (2)
[0082] The variable .theta. may be associated with any known value.
Furthermore, the rotation of the magnetic field may be associated
with any direction and as a result, the deflection direction may
also be associated with any direction. Furthermore, the magnitude
of the dipole magnetic field may remain constant, independent of
.theta..
[0083] FIG. 7 presents an example illustration of traverse plane
magnetic field vectors associated with the bore of a multi-pole
electromagnetic apparatus, in accordance with an embodiment of the
present invention.
[0084] A multi-pole electromagnetic apparatus 700 includes a
multiplicity of electromagnetic tip portion with a sampling denoted
as an electromagnetic tip portion 702 and an electromagnetic tip
portion 704.
[0085] Multi-pole electromagnetic apparatus 700 may be oriented
with respect to an x-axis 706, a y-axis 708 with a z-axis 710
projected into the page.
[0086] The electromagnetic tip portions may be separated by a
multiplicity of gaps with a sampling denoted as a gap 712. For
example, gap 712 may be located between electromagnetic tip portion
702 and electromagnetic tip portion 704. Furthermore, the
electromagnetic tip portions may be located such as to surround a
bore area 714.
[0087] A magnetic field may be created by multi-pole
electromagnetic apparatus 700 with the resultant magnetic field
illustrated by a multiplicity of magnetic field vectors with a
sampling denoted as a field vector 716. Magnetic field vectors
presented as black arrow heads may be oriented at a traverse plane
with respect to multi-pole electromagnetic apparatus 700. The equal
magnitude and direction orientation for the magnetic field vectors
illustrates the quality of the dipole magnetic field. For example,
the more diversity observed for the magnetic field vectors with
respect to magnitude and direction orientation, the less the
quality of magnetic field generated. For this example, the
calculation for coil current pattern produced a deflection angle of
260 degrees, which illustrates that there may be no constraint that
the field direction is aligned with the angular arrangement of the
electromagnetic tip portions.
[0088] The illustration presented by FIG. 7 provides a visual
indication of the dipole magnetic field quality for a magnetic
field rotated to an arbitrary angle. The associated magnetic field
quality may be confirmed quantitatively by evaluating Legendre
polynomial coefficients for the region where charged particles may
travel and by measuring the aberrations introduced into a known
beam transverse profile resulting from the beam traversing through
multi-pole electromagnetic apparatus 700.
[0089] FIG. 8 presents an example illustration of an
electromagnetic portion deflecting a beam of charged particles and
the orientation of the charged particles with respect to a
downstream plane, in accordance with an embodiment of the present
invention.
[0090] The illustration of FIG. 8 includes a charged particle beam
802, a multi-pole electromagnetic portion 804 and an intersect
plane 806.
[0091] Charged particle beam 802, multi-pole electromagnetic
portion 804 and intersect plane 806 may be orientated with respect
to an x-axis 808, a y-axis 810 and a z-axis 812.
[0092] Multi-pole electromagnetic portion 804 may operate to
receive and deflect charged particle beam 802.
[0093] Multi-pole electromagnetic portion 804 may be located a
distance 814, denoted as d, from intersect plane 806 and with
z-axis 812 traversing through its longitudinal center. Typical
values for d may be in the range of 1 m to 10 m.
[0094] Charged particle beam 802 may be deflected from z-axis 812
in the plane of the deflection direction by an angle 816, denoted
as .alpha., and intersect plane 806 at a point 818. Typical values
for a may be in the range of -10 degrees to +10 degrees.
[0095] Point 818 may be located a distance 822 from x-axis 808, a
distance 824 from y-axis 810 and a distance 820, denoted as R, from
z-axis 812. Furthermore, point 818 may be located at an angle 826,
denoted as .theta., with respect to x-axis 808.
[0096] Charged particle beam 802 may be considered as intersecting
intersect plane 806 at a polar location as denoted by R and
.theta.. The intersection of charged particle beam 802 with
intersect plane 806 at point 818 may also be resolved into x and y
coordinates.
[0097] Multi-pole electromagnetic portion 804 may operate to rotate
a fixed strength dipole magnetic field to any angle and as a result
deflect charged particle beam 802 to any angle. Furthermore,
multi-pole electromagnetic portion 804 may control the deflection
of charged particle beam 802 via parameters R and .theta..
[0098] For multi-pole electromagnetic portion 804 operating
sufficiently far from yoke saturation, the relationship between
I.sub.p and the dipole magnetic field may be considered as linear
with R a linear function of I.sub.p. Thus, maintaining I.sub.p
constant and incrementing .theta. transfers the location of point
818 (i.e. where charged particle beam 802 intersects intersect
plane 806) in a circle about intersect plane 806. For any
particular set of circumstances, point 818 may lie within a maximum
diameter circle. The diameter may be set by d and .alpha.. In a
non-limiting example, typical values for particle therapy are
diameters of 100 cm and less, although some treatments such as the
spine require larger fields. This may be achieved by increasing d
because a may be constrained by practical magnet design issues.
Furthermore, the maximum diameter of the circle may be dependant
upon a particular configuration and associated circumstances.
Non-limiting examples of circumstances contributing to the maximum
diameter of the circle include particle beam magnetic rigidity,
multi-pole electromagnetic portion 804 configuration, power supply
and distance of electromagnetic portion from intersect plane 806.
Charged particle beam 802 movement may not be dependant upon any
particular axis.
[0099] Conversion from coordinates associated with intersect plane
806 defined by Cartesian coordinates x, y to polar parameters R,
.theta. may be accomplished via conventional mathematical
transformations. For small angles of deflection for .alpha., the
I.sub.p, .theta. values for a given x,y position located on
intersect plane 806 may be given by Equation (3) and Equation (4)
shown below:
.theta.=sin.sup.-1(y/ (x.sup.2+y.sup.2)) (3)
I.sub.p=C.alpha. (4)
[0100] Standard sign conventions may be applied to .theta. based
upon whether point 818 lies within the right or left hand halves of
intersect plane 806. The element C in Equation (4) may represent a
proportionality constant. Non-limiting examples of parameters for
determining the value of C include coil design, size of
electromagnetic portion air gap, length of electromagnetic portion
and permeability of the magnetic flux for the return yoke.
Non-limiting examples of methods for determining the value of C
include direct measurement or electromagnetic modeling and ray
tracing. As a good approximation, a may be expressed in terms of
the beam rotation angle .theta. (or angle 826) and other geometric
parameters as given by Equation (5) below:
.alpha.=tan.sup.-1(x/d)/cos .theta. (5)
[0101] For Equation (5) d (or distance 814) may represent the
displacement along z-axis 812 from the center of multi-pole
electromagnetic portion 804 to intersect plane 806 and x (or
distance 824) may represent the displacement along x-axis 808.
[0102] The power amplifiers connected to the coils for supplying
power to electromagnetic portions may be of four-quadrant design
for supporting a charged particle beam placement at any geometric
location of intersect plane 806. The n/2 power amplifiers may
provide high-current and be supplied via a single DC power supply
with associated energy storage capacitors. The inductance of the
electromagnetic portion may be considered an energy storage device
which exchanges energy with the storage capacitors while
maneuvering the charged particle beam. High efficiency may be
experienced for a circular motion about z-axis 812, as the total
energy stored in multi-pole electromagnetic portion 804 remains
constant with small associated changes in electrical current,
resulting in small power amplifier switching losses.
[0103] Dipole magnetic field quality improves with an increased
number of poles. Furthermore, for most real-world cases, an eight
pole electromagnetic portion may be considered adequate for
practical and economic considerations. Furthermore, a six-pole
electromagnetic portion may yield sufficient dipole magnetic field
quality for many applications.
[0104] FIG. 9 presents a cross-section illustration of an example
multi-pole deflection apparatus with modified pole tips for
improving the quality of the associated dipole magnetic field for
deflecting a charged particle, in accordance with an embodiment of
the present invention.
[0105] A multi-pole deflection apparatus 900 has a similar
construction as sextupole deflection apparatus 400 (FIG. 4) except
the pole tips, with a sampling denoted as a pole tip 902, may be
configured with an associated circular profile in order to improve
the quality of the dipole magnetic field. Pole tips shaped as shown
for an inscribed circle 904 may operate to improve the magnetic
field quality at distances removed from a central axis 906.
Furthermore, the pole tips shaped for inscribed circle 904 may
operate to reduce charged particle beam aberrations at larger
angles of deflection.
[0106] FIG. 10 presents an illustration of an example multi-pole
deflection apparatus with modified air gap between poles for
providing greater clearance for a charged particle beam as it
deflects in the magnetic dipole field, in accordance with an
embodiment of the present invention.
[0107] A multi-pole deflection apparatus 1000 includes a
multiplicity of poles (some not shown) with a sampling denoted as a
pole 1002 and a pole 1004.
[0108] Pole 1002 and pole 1004 may be oriented with a z-axis 1006
running longitudinally through an air gap 1008 located between pole
1002 and pole 1004.
[0109] A charged particle 1014 may enter air gap 1008 at an entry
gap 1010 and exit at an exit gap 1012. A smaller distance between
pole 1002 and pole 1004 may be provided at entry gap 1010 than at
exit gap 1012. Furthermore, the distance between pole 1002 and pole
1004 may increase as a charged particle progresses from entry gap
1010 to exit gap 1012. As a result of the magnetic field provided
by multi-pole deflection apparatus 1000, charged particle 1014 may
follow a trajectory path 1016.
[0110] Large deflection angles result in a charged particle beam
coming in close proximity to poles. In order to reduce the risk of
a charged particle beam coming in contact with a pole and an
associated charged particle beam loss, the inscribed diameter for
the air gap may be increased along the length of the
electromagnetic portion. The associated flaring of the inscribed
diameter may be continuous along the full length of the
electromagnetic portion or may initiate at some distance along the
length of the electromagnetic portion. The resulting deflection for
a given set of excitation currents may be reduced by the associated
flaring.
[0111] FIG. 11 presents a cross-section illustration of an example
multi-pole deflection apparatus with a non-circular bore, in
accordance with an embodiment of the present invention.
[0112] A multi-pole deflection apparatus 1100 has a similar
construction as octupole deflection apparatus 500 (FIG. 5), except
with a non-circular bore 1102. For this example, an elliptical bore
has been presented for non-circular bore 1102, however any known
geometrical shape may be applied.
[0113] An electromagnetic portion with a non-circular bore may
operate in a similar manner as described previously for a circular
bore (e.g. FIG. 5). For example, for an elliptical bore, a rotating
magnetic field with constant I.sub.p generates an elliptical path
at an intersection plane, rather than a circular path.
[0114] Coil currents may be delivered to the coils not conforming
to the sinusoidal pattern described previously. Other patterns of
coil currents introduce higher order terms into the magnetic field
and result in distortion in the shape of the charged particle beam.
In some embodiments additionally imposed pattern of currents may be
non-sinusoidal or sinusoidal to produce beam shaping. In a
non-limiting example an additional superimposed sinusoidal pattern,
at twice the spatial frequency of the basic pattern that gives the
dipole field, may produce a useful quadrupole field component that
gives beam shaping typical of a quadrupole magnet. Application of
particular patterns of coil currents may be applied in order to
introduce deliberate charged particle beam shaping such as, but not
limited to, the beam transverse shape to be more like a line than a
circle. Furthermore, a separate power amplifier may be connected to
individual coils, rather than to pairs of opposed coils as
described previously, providing further control over charged
particle beam shaping. In a non-limiting example, a useful use of
this beam shaping capability is to make the quadrupole field
component of this multipole magnet one half of a quadrupole
doublet. The other member of the doublet would be a conventional
quadrupole magnet structure positioned before the multipole magnet
in the beam path. This combination may provide focusing in both
transverse axes orthogonal to the beam axis, which is the typical
function of a quadrupole doublet. The benefit is that the need for
a second conventional quadrupole is avoided, and thus cost and
space are saved.
[0115] For many applications, the ability to perform timely
magnetic field changes may be required. A beam scanning magnetic
apparatus may be considered as a non-limiting example for an
application making use of a fast changing magnetic field.
Furthermore, to support a fast changing magnetic field, the return
yoke structure may be constructed from thin laminations in order to
minimize losses and field distortions associated with eddy
currents. Furthermore, as a non-limiting example, the yoke
structure maybe constructed of laminated steel, ferrite or any
material with relative permeability greater than 1. Furthermore, to
support a fast changing magnetic field, the coils may have a
relatively small number of turns in order to minimize the
inductance. Furthermore, to support a fast changing magnetic field,
the power amplifiers may support high current capability, typically
hundreds of amperes, in order to support the small number of turns
in the coils. Furthermore, to support a fast changing magnetic
field, the power amplifiers may support a wide voltage range,
typically up to +/-800V with currents up to 800 A, in order to
allow the inductive load to transition to a new current level.
Furthermore, to support a fast changing magnetic field, the power
amplifiers may support a wide bandwidth, typically DC to a
multiplicity of kilohertz in order to minimize the settling time
after transitioning to a new current level.
[0116] FIG. 12 presents a cross-section illustration of an example
multi-pole deflection apparatus incorporating a Hall effect probe
to provide magnet field feedback for monitoring and control, in
accordance with an embodiment of the present invention.
[0117] A multi-pole deflection apparatus 1200 has a similar
construction as octupole deflection apparatus 500 (FIG. 5), except
with a multiplicity of Hall effect probes, with a sampling denoted
as a Hall effect probe 1202, configured in a multiplicity of
recesses, with a sampling denoted as a recess 1204.
[0118] For applications where large magnetic field strengths may be
required, assumptions previously described for a magnetic field as
a linear function of I.sub.p may not hold. The magnetic field as a
linear function of I.sub.p may also not hold for conditions of
significant eddy currents and steel hysteresis. For these types of
applications and conditions, Hall effect probe 1202 may be
configured for accurately measuring magnetic fields. The signal
provided by Hall effect probe 1202 may be used as a confirmatory
function or as a process feedback for closed-loop electromagnetic
field control. Hall effect probe 1202 may be positioned at the tips
of individual poles in order to enable measurement of the
individual contributions to the net magnetic field.
[0119] Those skilled in the art will readily recognize, in
accordance with the teachings of the present invention, that any of
the foregoing steps and/or system modules may be suitably replaced,
reordered, removed and additional steps and/or system modules may
be inserted depending upon the needs of the particular application,
and that the systems of the foregoing embodiments may be
implemented using any of a wide variety of suitable processes and
system modules, and is not limited to any particular computer
hardware, software, middleware, firmware, microcode and the like.
For any method steps described in the present application that can
be carried out on a computing machine, a typical computer system
can, when appropriately configured or designed, serve as a computer
system in which those aspects of the invention may be embodied.
[0120] Having fully described at least one embodiment of the
present invention, other equivalent or alternative methods of
performing electromagnetic deflection of a charged particle beam
according to the present invention will be apparent to those
skilled in the art. The invention has been described above by way
of illustration, and the specific embodiments disclosed are not
intended to limit the invention to the particular forms disclosed.
For example, the particular implementation of the power amplifiers
described with reference to FIG. 3 may vary depending upon the
particular application the apparatus is to be applied. The
exemplary power amplifiers described in the foregoing were directed
to medical implementations; however, similar techniques may be
demonstrated for other applications such as for semiconductor
manufacture. Implementations of the present invention are
contemplated as within the scope of the present invention. The
invention is thus to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the following
claims.
[0121] Claim elements and steps herein may have been numbered
and/or lettered solely as an aid in readability and understanding.
Any such numbering and lettering in itself is not intended to and
should not be taken to indicate the ordering of elements and/or
steps in the claims.
* * * * *