The present invention relates to a charged particle orbit control device, a charged particle accelerator, a charged particle storage ring and a bending magnet that control the ring-shaped orbits of charged particles.
Major types of ring-shaped charged particle accelerators include cyclotrons and synchrotrons. With a cyclotron, the orbital radius of an accelerating charged particle increases as its energy rises. On the other hand, with a synchrotron, the strength of the bending magnets increases in synchronization with the rising energy of an accelerating charged particle, and thus the orbit of the accelerating charged particle is kept constant.
Besides being used as high-energy accelerators for electrons (positrons) and protons, synchrotron-type charged particle accelerators and charged particle storage rings are currently being built and operated worldwide as rings for radiation sources of various size (see Non Patent Literature 1 to 5, for example). Also, a large number of synchrotron facilities that accelerate and store protons or carbon ions provided for medical use are being built recently (see Non Patent Literature 6 to 8, for example).
Particle orbits in these synchrotron accelerators disclosed in Non Patent Literature 1 to 8 all close in one cycle. In other words, charged particles in the accelerators return to their original orbit in one cycle around the ring.
In this way, ring-shaped charged particle accelerators and charged particle storage rings for radiation sources are being designed and manufactured such that a charged particle bunch (bunch) assumes the same ring orbit every cycle around the ring. In other words, in the charged particle accelerators and charged particle storage rings of the related art, one ring cycle becomes one period of the ring orbit.
In this case, the maximum number of storable bunches is uniquely determined by the RF frequency and the length of one ring cycle (path length). In the case of storing one bunch per cycle, the time interval at which a bunch arrives at a place on the ring is uniquely determined by the path length.
Thus, for example, in the case of conducting time-of-flight (TOF) that tracks the change over time in the electronic state of matter excited by radiation pulses, the maximum value of the pulse interval is determined by the ring path length, and thus tracking the process of the change all the way to the end becomes difficult if the ring path length is short.
In other words, with the charged particle accelerators and charged particle storage rings of the related art, since the time during which a bunch cycles and returns to its original orbit is determined by the path length, small-scale rings with short path lengths make it difficult to obtain a long bunch interval necessary for experiments such as TOF in research that utilizes radiation, even in the case of conducting single-bunch operation. In addition, the maximum number of storable charged particles is also determined by the maximum number of bunches, which is determined by the path length.
Furthermore, with an electron synchrotron which is used as a radiation source, a high-intensity light-emitting device called an insertion device is typically installed on the straight parts of the ring. With a ring that returns to the original orbit in one cycle, the number of straight parts where an insertion device is installable becomes limited.
The present invention, being devised in light of the foregoing circumstances, takes as an object to provide a ring-shaped charged particle orbit control device, a charged particle accelerator, a charged particle storage ring, and a bending magnet able to substantially lengthen the path length within the same installation area.
In order to achieve the above object, a charged particle orbit control device according to a first aspect of the present invention
is used in a ring-shaped charged particle accelerator or a charged particle storage ring,
is configured to enable a charged particle to return to an original orbit in a plurality of cycles, and includes
a plurality of bending magnets that bend the charged particle,
wherein the bending angle and relative position of each bending magnet are predetermined such that every time the charged particle passes through, an orbit of the charged particle in each bending magnet alternately switches between two orbits.
In another possible configuration,
the bending angle and the relative position of each bending magnet are predetermined such that every time the charged particle passes through, an incident position of the charged particle incident on each bending magnet alternately switches between two positions.
In another possible configuration,
the bending angle and the relative position of each bending magnet are predetermined such that every time the charged particle passes through, an incident angle of the charged particle incident on each bending magnet alternately switches between two angles.
In another possible configuration,
in each bending magnet,
a magnetic field gradient is formed from an inner side to an outer side of the orbit of the charged particle.
In another possible configuration,
provided that n is a natural number that is not a multiple of m, each bending magnet is disposed on an outer rim of an n-sided regular polygon, and configured such that the charged particle returns to the original orbit in m cycles (where m is a natural number other than 1).
In another possible configuration,
each bending magnet
bends the charged particle such that the orbit of the cycling charged particle contains part of each edge of the n-sided regular polygon, and in addition, the charged particle travels along every (m−1)th edge of the n-sided regular polygon.
In another possible configuration,
m is 3,
the bending magnets
are respectively disposed at each vertex of the n-sided regular polygon,
bend a charged particle arriving from a neighboring vertex on one side towards a vertex neighboring a neighboring vertex on the other side, and
bend the charged particle arriving from another vertex neighboring the neighboring vertex on the one side towards the neighboring vertex on the other side.
In another possible configuration,
a bending magnet that bends the charged particle exiting each vertex towards a neighboring vertex is additionally provided between each vertex of the n-sided regular polygon.
In another possible configuration,
n is a natural number that is neither a multiple of 2 nor a multiple of 3, and
an electromagnet power source that controls the magnetic force of each of the plurality of bending magnets is additionally provided,
wherein the electromagnet power source, by adjusting the magnetic force of each of the plurality of bending magnets,
is able to switch m among the natural numbers 1 through 3.
In a charged particle accelerator according to a second aspect of the present invention, an orbit of a charged particle is controlled by a charged particle orbit control device according to the present invention.
In a charged particle storage ring according to a third aspect of the present invention, an orbit of a charged particle is controlled by a charged particle orbit control device according to the present invention.
A bending magnet according to a fourth aspect of the present invention
is used in a charged particle orbit control device according to the present invention,
the bending magnet receives a charged particle incident from different positions, includes a plurality of different orbits for the charged particle depending on an incident position, and ejects the charged particle from a plurality of different positions according to each of the different orbits.
According to the present invention, the number of cycles in which a charged particle returns to the original orbit is set to be multiple cycles, and thus the path length is substantially doubled or more within the same installation area. Lengthening the path length exhibits the advantages indicated below.
(1) In TOF conducted with a small-scale radiation source electron storage ring (time-resolved photoemission spectroscopy experiments, for example), it becomes possible to track the change over time in the electronic state of matter all the way to the end state.
(2) Since the path length is doubled or tripled within the same installation area, the maximum number of charged particles storable in the ring is also doubled or tripled, and thus in the case of application to an accelerator for medical applications, such as for radiation therapy, for example, the radiation dose potentially radiated in a beam onto an affected area is significantly increased.
(3) The number of straight parts allowing insertion of an insertion device is significantly increased, and thus, it becomes possible to install a greater number of experimental stations able to utilize high-intensity light.
(4) It becomes possible to configure a charged particle accelerator and charged particle storage ring in a small space at low cost. Also, according to the present invention, each bending magnet is disposed such that the orbit of the charged particle alternately switches every time the charged particle passes through a bending magnet. Thus, the present invention exhibits the following advantages.
(5) The number of straight lines in the orbit of the charged particle with respect to the number of bending magnets is further increased.
(6) It is possible to increase the number of bending magnets through which the charged particle passes during one cycle, and thus it is possible to decrease the bending angle while increasing the number of straight lines, and realize lower emittance.
Embodiments of the present invention will be described in detail and with reference to the drawings.
First, a first embodiment of the present invention will be described.
First, a configuration of a charged particle orbit control device 100 according to the present embodiment will be described with reference to
The bending magnets 1 (1A to 1K) are respectively disposed at the vertices of a regular hendecagon. In other words, in the present embodiment, the number of cycles m is 2, the number of edges n is 11, and n is not a multiple of m.
The bending magnets 1 (1A to 1K) bend a charged particle 3. The bending magnets 1 (1A to 1K) bend the charged particle 3 such that the charged particle 3 passes through every other vertex of the regular hendecagon. For example, the bending magnet 1A bends the charged particle 3 arriving from the bending magnet 1J towards the bending magnet 1C.
In
The quadrupole electromagnets 2 are disposed along the orbit of the charged particle 3. The quadrupole electromagnets 2 inhibit scattering of a charged particle bunch made up of charged particles 3.
Note that in
In
In the charged particle orbit control device 100, the charged particle 3 returns to the original orbit in two cycles. In other words, in the present embodiment, m=2.
In the charged particle orbit control device 100 according to the present embodiment, the number of cycles in which the charged particle 3 returns to the original orbit is two cycles, with two ring cycles making one period. Thus, the path length is substantially doubled or more within the same installation area. Lengthening the path length exhibits the advantages indicated below.
(1) In the case of single-bunch operation, the bunch interval is doubled. For example, in TOF experiments conducted with a small-scale radiation source electron storage ring (time-resolved photoemission spectroscopy experiments, for example), it becomes possible to track the change over time in the electronic state of matter all the way to the end state.
(2) In the case of multi-bunch operation, the amount of stored charge is doubled at maximum. For example, since the path length is doubled within the same installation area, the maximum number of charged particles storable in the ring is also doubled. Thus, in the case of application to an accelerator for medical applications, such as for radiation therapy, for example, the radiation dose radiated in a beam onto an affected area is significantly increased.
(3) The number of straight parts allowing insertion of an insertion device or RF cavity is significantly increased. Thus, it becomes possible to install a greater number of experimental stations able to utilize high-intensity light.
(4) It becomes possible to configure a charged particle accelerator and charged particle storage ring in a small space at low cost.
Note that the lattice in which the number of cycles is 2 is not limited to being a regular hendecagon.
For example, it is also possible to form a regular pentagonal lattice, as illustrated in
It is possible to modify the shape of the lattice in a regular pentagon as illustrated in
As another example, it is also possible to form a regular heptagonal lattice, as illustrated in
It is possible to modify the shape of the lattice in a regular heptagon as illustrated in
As another example, it is also possible to form a regular nonagonal lattice, as illustrated in
It is possible to modify the shape of the lattice in a regular nonagon as illustrated in
As another example, it is also possible to form a regular hendecagonal lattice, as illustrated in
It is possible to modify the shape of the regular hendecagonal lattice as illustrated in
As another example, it is also possible to form a regular tridecagonal lattice, as illustrated in
It is possible to modify the shape of the regular tridecagonal lattice as illustrated in
An edge-type charged particle orbit control device 100 will now be described in further detail.
In
More specifically, in the charged particle orbit control device 100, the bending angle and relative position of each bending magnet 1 are prescribed such that every time the charged particle 3 passes through, the incident position of the charged particle 3 incident on each bending magnet 1 alternately switches between two positions. The incident position alternately switches, but since the bending angle is fixed in each bending magnet 1, the orbit of the charged particle 3 passing through the bending magnets 1 forms two types.
Note that it is necessary to design each bending magnet 1 such that the distance L and the length of the straight parts of the orbit of the charged particle 3 are suited to the usage of the charged particle orbit control device 100. Also, although the pole tips of the bending magnets 1 are orthogonal to the orbit, an arbitrary angle is typically selectable.
According to the charged particle orbit control device 100 illustrated in
(1)′ The number of straight lines in the orbit of the charged particle 3 with respect to the number of bending magnets 1 is further increased over the vertex-type charged particle orbit control device 100 illustrated in
(2)′ Since it is possible to increase the number of bending magnets 1 through which the charged particle 3 passes during one cycle, it is possible to decrease the bending angle while increasing the number of straight lines. For this reason, it is possible to realize lower emittance (smaller diameter) in the particle beam.
First, a second embodiment of the present invention will be described.
The charged particle orbit control device 100 according to the present embodiment differs from the foregoing first embodiment in that the charged particle 3 returns to the original orbit in three cycles rather than two cycles. In other words, in the present embodiment, m=3.
Among the particle orbit bends in
The bending magnet 1 bends a charged particle 3 arriving from a neighboring vertex on one side towards the vertex neighboring the neighboring vertex on the other side. Also, the bending magnet 1 bends a charged particle 3 arriving from another vertex neighboring the neighboring vertex on the one side towards the neighboring vertex on the other side. In terms of the charged particle orbit, with this layout the two neighboring bending magnets at each vertex of the regular hendecagon work as a group to bend (deflect) the orbit of the charged particle 3 towards another vertex that neighbors the neighboring vertices. Hereinafter, this type of lattice will also be called a double-bend-type.
As illustrated in
Note that the lattice in which the number of cycles m is 3 is not limited to being based on a regular hendecagon.
In the charged particle orbit control device 100 according to the present embodiment, the number of cycles in which the charged particle 3 returns to the original orbit is three cycles, with three ring cycles making one period. Thus, the path length is substantially tripled or more within the same installation area. Lengthening the path length exhibits the advantages indicated below.
(1) In the case of single-bunch operation, the bunch interval is triple the ordinary interval. For example, in TOF conducted with a small-scale radiation source electron storage ring (time-resolved photoemission spectroscopy experiments, for example), it becomes possible to track the change over time in the electronic state of matter all the way to the end state.
(2) In the case of multi-bunch operation, the amount of stored charge is potentially tripled at maximum. For example, since the path length is tripled within the same installation area, the maximum number of charged particles storable in the ring is also tripled. Thus, in the case of application to an accelerator for medical applications, such as for radiation therapy, for example, the radiation dose potentially radiated in a beam onto an affected area within the same treatment time is significantly increased. As a result, it is possible to greatly reduce the total treatment time.
(3) The number of straight parts allowing insertion of an insertion device or RF cavity is significantly increased. Thus, it becomes possible to install a greater number of experimental stations able to utilize high-intensity light.
The charged particle orbit control device 100 includes multiple bending magnets 1 that bend the charged particle 3, and the bending angle and relative position of each bending magnet 1 are prescribed such that every time the charged particle 3 passes through, the orbit of the charged particle 3 in each bending magnet 1 alternately switches between the two orbits.
In further detail, in the charged particle orbit control device 100, the bending angle and relative position of each bending magnet 1 are prescribed such that every time the charged particle 3 passes through, the incident position of the charged particle 3 incident on each bending magnet 1 alternately switches between two positions. In addition, in the charged particle orbit control device 100, the bending angle and relative position of each bending magnet 1 are prescribed such that every time the charged particle 3 passes through, the incident angle of the charged particle incident on each bending magnet 1 alternately switches between two angles.
The charged particle orbit control device 100 according to the present embodiment has the following advantages.
(1)′ The number of straight lines in the orbit of the charged particle 3 with respect to the number of bending magnets 1 is further increased over the two-cycle, vertex-type charged particle orbit control device 100 (see
(2)′ Since it is possible to increase the number of bending magnets 1 through which the charged particle 3 passes during one cycle, it is possible to decrease the bending angle while increasing the number of straight lines. For this reason, it is possible to realize lower emittance in the particle beam.
First, a third embodiment of the present invention will be described.
The charged particle orbit control device 100 in
The charged particle orbit control device 100 is additionally equipped with an electromagnet power source 5 that controls the magnetic force of each of the bending magnets 1 and 4. In the present embodiment, it is possible to switch the number of cycles m from 1 to 3 by having the electromagnet power source 5 adjust the magnetic force of the bending magnets 1 and 4.
The lattice in the charged particle orbit control device 100 is based on a regular heptagon. In the present embodiment, n=7. The number n is a natural number that is neither a multiple of 2 nor a multiple of 3.
In addition,
In addition,
The charged particle orbit control device 100 according to the present embodiment is able to switch a single period of the charged particle 3 from one cycle to three cycles. According to this charged particle orbit control device 100, it becomes possible to adjust the path length of the orbit of the charged particle 3 according to the intended purpose.
Note that edge-type lattices typically have fewer bending magnets and more straight lines compared to vertex-type lattices. However, with an edge-type lattice, since the straight-line orbit in the first cycle and the straight-line orbit in the second cycle tend to be in proximity, the need to separate the two straight-line orbits to some degree should be noted.
Note that although the foregoing describes various lattices, the lattice in the charged particle orbit control device 100 is not limited to being in accordance with the foregoing embodiments.
For example, it is also possible to form a lattice based on a regular triangle, as illustrated in
Additionally, with a lattice based on a regular pentagon, it is also possible to form a lattice as illustrated in
In other words, in each bending magnet 1, there exist two orbits through which the charged particle 3 passes. The bending angle and relative position of each bending magnet are prescribed such that every time the charged particle 3 passes through each bending magnet 1, the orbit of the charged particle 3 in each bending magnet 1 alternately switches between the two orbits.
More specifically, in this charged particle orbit control device 100, the bending angle and relative position of each bending magnet 1 are likewise prescribed such that every time the charged particle 3 passes through, the incident position of the charged particle 3 incident on each bending magnet 1 alternately switches between two positions. Also, in this charged particle orbit control device 100, the bending angle and relative position of each bending magnet are prescribed such that every time the charged particle 3 passes through, the incident angle of the charged particle incident on each bending magnet 1 alternately switches between two angles.
The strength of the magnetic field of each bending magnet 1 is prescribed such that the bending angle of a charged particle 3 incident on the inner side of the orbit becomes slightly less than 72 degrees, and such that the bending angle of a charged particle 3 incident on the outer side of the orbit becomes slightly larger than 72 degrees. Thus, in each bending magnet 1, a charged particle 3 passing through the inner orbit and incident on each bending magnet 1 heads towards the outer orbit, while a charged particle 3 passing through the outer orbit and incident on each bending magnet 1 heads towards the inner orbit.
According to such orbit settings for the charged particle 3 and the placement of each bending magnet 1, the orbit of the charged particle 3 intersects on the straight parts of the orbits in the charged particle orbit control device 100 illustrated in
Note that in this charged particle orbit control device 100, it is still necessary to design each bending magnet 1 such that the length of the straight parts of the orbit of the charged particle 3 and the like are suited to the usage of the charged particle orbit control device 100. Although the pole tips of these bending magnets 1 are orthogonal to the orbit, an arbitrary angle is typically selectable.
Also, although the foregoing embodiments describe lattices in which the charged particle 3 returns to the original orbit in two cycles or three cycles, the present invention is not limited thereto. For example, it is also possible to form a lattice in which the charged particle 3 returns to the original orbit in four or more cycles.
In any case, m is a natural number other than 1, and n is a natural number that is not a multiple of m.
In this way, in a charged particle orbit control device 100 according to the foregoing embodiments, the bending magnet 1 has two intersecting orbits, as illustrated in
The two angles that characterize the structure of a bending magnet 1 in an charged particle orbit control device 100 having an n-sided polygonal shape and m cycles are summarized below, classified into the two types of the double-bend type and the triple-bend type.
First, in the case of a double-bend-type charged particle orbit control device 100, a single inner angle of the n-sided regular polygon becomes 180(n−2)/n [deg.], and the total sum of bending angles θ1 becomes 360×m [deg.]. In addition, the total number of bending magnets 1 through which the charged particle 3 passes in one period becomes 2×n. In this case, the bending angle θ1 of each bending magnet 1 becomes the following formula.
MATH. 1
θ1=360×m/(2×n)=180m/n [deg.] (1)
Also, the intersection angle θ2 between two orbits becomes the following formula.
MATH. 2
θ2=180(n−2)/n−(180−180m/n)=180(m−2)/n [deg.] (2)
Intersection angles θ2 in a double-bend-type charged particle orbit control device 100 having an n-sided polygonal shape and m cycles are summarized in the following table.
Next, in the case of a triple-bend-type charged particle orbit control device 100, a single inner angle of the n-sided regular polygon becomes 180(n−2)/n [deg.], and the total sum of bending angles θ1 becomes 360×m [deg.]. Also, the total number of bending magnets 1 through which the charged particle 3 passes becomes n for the bending magnets 4 in which the orbit does not intersect, and 2×n for the bending magnets 1 in which the orbit does intersect. In this case, the bending angle θ1 of each of the bending magnets 1 and 4 becomes
MATH. 3
θ1=360/n [deg.] (3)
for the bending magnets 4 without intersection, and
MATH. 4
θ1=[360×m−n×(360/n)]/(2×n)=180(m−1)/n [deg.] (4)
for the bending magnets 1 with intersection.
Also, the intersection angle θ2 between two orbits becomes the following formula.
MATH. 5
θ2=180(m−1)/n [deg.] (5)
Intersection angles θ1 in a triple-bend-type charged particle orbit control device 100 having an n-sided polygonal shape and m cycles are summarized in the following table.
Also, in the foregoing embodiments, a configuration is possible in which a magnetic field gradient is provided in each bending magnet 1 from the inner side to the outer side of the orbit of the charged particle 3. For example, as illustrated in
Also, although the each bending magnet 1 is disposed on the outer periphery of a regular polygon in the foregoing embodiments, the present invention is not limited thereto. For example, as illustrated in
As illustrated in
In any case, a charged particle orbit control device 100 according to the foregoing embodiments accepts a charged particle 3 incident from multiple different positions, has multiple orbits for the charged particle 3 depending on the incident position, requiring bending magnets 1 that eject the charged particle 3 from multiple different positions according to the orbit. By providing such bending magnets 1, the advantages of the charged particle orbit control device 100 discussed above are exhibited.
The present invention is not limited by the foregoing embodiments and drawings. Obviously, it is possible to modify the embodiments and drawings within a scope that does not alter the principal matter of the present invention. Essentially, the configuration is such that one period in the orbit of a charged particle has multiple cycles rather than one cycle.
In other words, various embodiments and modifications of the invention are possible without departing from the scope and spirit of the invention in the broad sense. Furthermore, the foregoing embodiments are for the purpose of describing the invention, and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims rather than the embodiments. In addition, various alterations performed within the scope of the claims or their equivalents are to be regarded as being within the scope of the invention.
This application is based on Japanese Patent Application No. 2010-283850 filed in the Japan Patent Office on Dec. 20, 2010, and the entirety of the specification, claims, and drawings of Japanese Patent Application No. 2010-283850 are hereby incorporated by reference.
The present invention is suitable for use in a charged particle accelerator and charged particle storage ring, as discussed above.
Number | Date | Country | Kind |
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2010-238850 | Dec 2010 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2011/079423 | 12/19/2011 | WO | 00 | 6/19/2013 |