WO2003092340A1

WO2003092340A1 - Particle accelerator

Info

Publication number: WO2003092340A1
Application number: PCT/IB2002/001374
Authority: WO
Inventors: Pierre Mandrillon
Original assignee: Accelerators For Industrial & Medical Applications. Engineering Promotion Society. Aima. Eps
Priority date: 2002-04-25
Filing date: 2002-04-25
Publication date: 2003-11-06
Also published as: EP1500313A1; CA2495460A1; CN1631061A; AU2002258016A1

Abstract

The invention concerns a particle accelerator, comprising a source for generating a beam of charged particles to be accelerated, at least one cyclotron for accelerating particles derived from the source, at least one actuator (40) for acting on the beam particles before they are accelerated by the cyclotron, at least one sensor (33) for delivering an information representing the intensity of the beam of particles accelerated by the cyclotron, and a programmable control device (50) for acting on the actuator on the basis of information delivered by the sensor and a programmed control law of the intensity of the beam of particles accelerated in time, so that the intensity of the beam delivered by the cyclotron observes the programmed control law.

Description

Particle accelerator The present invention relates to particle accelerators and their industrial and medical applications, in particular.

Particle accelerators are described in the publication CERN ACCELERATOR SCHOOL, CYCLOTRONS, LINACS AND THEIR APPLICATIONS, GENENA 96, following the seminar held in Belgium from April 28 to May 5, 1994, the content of which is incorporated into this application by reference .

There is a need to have an accelerator capable of delivering a beam of accelerated particles whose intensity can be controlled reliably and quickly.

The invention aims in particular to meet this need.

It achieves this thanks to a particle accelerator, comprising:

a source capable of generating a beam of charged particles to be accelerated,

- at least one cyclotron to accelerate particles from the source, - at least one actuator to act on the particles of the beam before their acceleration by the cyclotron,

at least one sensor capable of delivering information representative of the intensity of the particle beam accelerated by the cyclotron, and

- a programmable control device capable of acting on the actuator as a function of the information delivered by the sensor and of a programmed control law of the intensity of the particle beam accelerated over time, so that the he intensity of the beam delivered by the cyclotron respects the programmed control law.

Thanks to the invention, it is possible to deliver a beam of accelerated particles with a variable intensity over time and evolving in a predetermined manner.

It is thus possible, for example, to control more precisely the distribution of a dose of radiation in a volume to be treated, which can make it possible in particular to improve the effectiveness of hadrontherapy and of therapy by neutron capture by boron, also called BΝCT. It is still possible, thanks to the invention, to power the accelerator-controlled systems, also called ADS, more precisely.

The aforementioned sensor may include a peeler through which the beam of particles accelerated by the cyclotron. This peeler can be an electronic or nuclear peeler. A nuclear peeler can generate, for example, neutrons.

The actuator, which may or may not be mechanical, may comprise at least one electrostatic and / or magnetic deflector or at least one movable member capable of intercepting particles from the beam.

The actuator can also comprise, for example, at least one grouper, in particular two groupers. In the latter case, each grouper may include a central electrode having a time-varying potential, disposed between two end electrodes at the same potential, the central electrode creating with each of the end electrodes a potential difference acting on the particles from the source. The length of the central electrode of the grouper crossed first by the beam may be different from that of the central electrode of the grouper crossed second by the beam, and may in particular be greater, being worth for example double. The voltages applied to the central electrodes can be sinusoidal.

The voltages applied to the two groupers can correspond substantially to the first two terms of the Fourier series decomposition of a sawtooth tension.

The control device can be configured to modify the phase shift between the voltages applied to the groupers according to the information delivered by the sensor.

The programmed current law can comprise, as a function of time, at least two slots, in particular at least two slots of different amplitudes.

The source may be able to generate molecular ions, for example H ₂ ⁺ or H ₃ ⁺ ions.

The source may also be able to generate H ^" or D ^" ions, among others.

The programmable control device is advantageously fast and has for example a response time less than or equal to 10 μs, preferably less than or equal to 5 μs, for example of the order of 1 μs. The accelerator may include any post-acceleration element operating continuously.

The accelerator can thus include, for example, two cyclotrons, for example a first cyclotron associated with the source and a second cyclotron to accelerate particles from the first cyclotron. In this case, the sensor may include a peeler disposed inside the second cyclotron and the particles, for example H ₂ ions, accelerated by the first cyclotron can leave the latter without passing through a peeler.

The accelerator may include a deflection device making it possible to carry out, with the beam of accelerated particles, a scanning of a predetermined area, for example a region of the human body. The programmable control device can then be arranged, for example, to modify the intensity of the beam of accelerated particles as a function of the position of the beam.

The present invention, according to another of its aspects, also relates to a method for producing a beam of accelerated particles having an intensity varying in a programmed manner over time, this method possibly comprising the step consisting in programming the programmable control device the accelerator defined above as a function of the variation over time of the desired intensity.

Another subject of the invention, according to another of its aspects, is a method for treating the human or animal body, which may include the step of irradiating an area to be treated with a beam of accelerated particles by means of an accelerator of particles as defined above. In such a method, it is possible, in particular in the case of hadrontherapy, to scan the area to be treated with the beam of accelerated particles and modify the intensity of the beam over time to take account of the dose received by the different regions when crossing them by the beam to treat the deepest regions. The intensity of the particle beam can, for example, evolve in slots of decreasing amplitude over time, the treatment being able to be carried out with a higher intensity to begin with, in order to treat the deepest regions, and weaker in last, in order to treat the shallowest regions.

It is also possible to use a particle accelerator according to the invention to power an accelerator-controlled system. Such an accelerator-driven system can include, for example, an energy amplifier, a subcritical nuclear reactor or a nuclear waste transmitter.

It is also possible to use a particle accelerator according to the invention to produce a neutron flux, in particular a substantially monoenergetic neutron flux.

The invention will be better understood on reading the detailed description which follows, of nonlimiting examples of implementation, and on examining the appended drawing, in which:

FIG. 1 is a schematic and partial view of an example of an accelerator according to the invention,

FIG. 2 is a block diagram illustrating the control of the intensity of the beam delivered by the accelerator, FIG. 3 represents in schematic and partial view, in axial section, two consolidators,

FIG. 4 represents the variation of the exit phase of the particles as a function of their entry phase, when they pass through the two groupers,

FIG. 5 represents an example of variation in the intensity of the beam of accelerated particles as a function of their phase of exit from the injection line,

FIG. 6 represents, in schematic and partial axial section, a movable element of another example of actuator according to the invention,

FIG. 7 schematically represents another example of an actuator, comprising an electrostatic deflector, FIG. 8 represents an example, among others, of the intensity law that can be programmed,

FIG. 9 schematically represents an area to be treated by a beam of accelerated particles,

FIGS. 10 and 11 show other nonlimiting examples of intensity laws that can be programmed, and

- Figure 12 shows, schematically and partially, in side view, an example of a double cyclotron particle accelerator that can use a programmable intensity control device.

FIG. 1 shows a particle accelerator 1 comprising an ion source 10 intended to generate charged particles, for example H ^" ions, and a cyclotron 20 to accelerate these particles.

The particles emitted by the source 10 are injected into the cyclotron, in the example illustrated, by an axial injection line 30. The latter incorporates an actuator 40, whose role will be explained below, comprising a first grouper 21 and a second grouper 22.

The injection line 30 also comprises, in a conventional manner, focusing lenses, magnetic or electrostatic.

The particles to be accelerated leaving the injection line 30 are injected into a central region of the cyclotron 20, in a manner known per se.

Cyclotron 20 is, for example, of the compact isochronous type, and may or may not be superconductive. The particles are accelerated by cyclotron 20 along a trajectory in the general form of a spiral, as illustrated in FIG. 1.

Only the last orbit of accelerated particles has been shown in this figure. The beam passes through an electronic peeler 33, comprising for example a carbon sheet having a density between 20 and 60 μg / cm ² . In the example considered, the accelerated particles are H ^" ions. The peeler 33 transforms them into H ⁺ protons and the curvature of their trajectory is reversed, which allows them to leave the cyclotron.

A conventional optical system 35 makes it possible to direct the beam thus extracted from the cyclotron towards a target for the production of radioelements or towards any zone of the human or animal body or of an object to be treated. The beam can in particular be directed towards a deflection device 41 making it possible to carry out, with the accelerated beam, a scan of an area to be treated, for example a tumor.

The peeler 33 is electrically isolated, which makes it possible to measure the intensity of the electric current corresponding to the beam of particles passing through it. The accelerator 1 comprises a programmable control device 50, shown diagrammatically in FIG. 2. This device 50 receives information representative of the intensity measured by the peeler 33 and makes it possible to control the intensity of the particle beam delivered by the 'accelerator.

The device 50 can be programmed with any intensity law, being configured to continuously control by feedback the actuator 40 so that the intensity actually delivered by the cyclotron respects the programmed intensity law. In the example illustrated, the device 50 is produced with components fast electronics, which makes it possible to obtain a very short response time, for example of the order of 1 μs.

We will now describe, with reference to FIG. 3, the two separate groupers 21 and 22 of the actuator 40. The particle beam emitted by the source 10 propagates along an axis X, passing through the grouper 21 then the grouper 22 .

The grouper 21 comprises a central electrode 60 and two end electrodes 61 and 62.

Similarly, the grouper 22 comprises a central electrode 63 and two end electrodes 64 and 65.

In the example considered, the length of the central electrode 60 of the first grouper 21, measured along the axis X, is twice that of the central electrode 63 of the second grouper 22, since the frequency of the voltage N ₂ applied to the central electrode of the second grouper 22 is twice the frequency of the voltage Vι applied to the central electrode of the first grouper 21. The end electrodes 61, 62, 64 and 65 are, in the example illustrated , to ground.

We can assign to each particle, coming from the source 10, an input phase φ _e and an output phase φ _s . These phases correspond to the relative position of the particles at the inlet and at the outlet of the injection line 30. The groupers 21 and 22 make it possible to act on the outlet phase φ _s of the particles as a function of their phase of entry φ _e . The particles whose exit phase φ _s is included in an interval [φ _l5 φ ₂ ] called acceptance interval, with <pι and φ ₂ neighbors of 15 ° for example in absolute value, are accelerated by cyclotron 20 while the particles having an output phase φ _s not included in this interval are lost and do not form part of the particle beam delivered by the cyclotron 20. The phases ψ \ and φ ₂ can be different or equal, in absolute value.

The shape of the voltage N, sum of the tensions Ni and N, can approach that of a sawtooth signal if one chooses the tensions Ni and N ₂ as the first two terms of the decomposition in series Fourier signal of a sawtooth signal. FIG. 4 illustrates the grouping of the particles after passage through the grouper 21 then in the grouper 22.

Thanks to the combined use of the two consolidators 21 and 22, it is possible to obtain for example around 70% of particles whose exit phase φ _s is within the cyclotron acceptance interval, therefore not lost.

In FIG. 5, the intensity I of the particle beam at the exit from the injection line is represented as a function of the exit phase φ _s . We can notice that the intensity varies very quickly near the limits of the acceptance interval.

Thus, a relatively small variation in the output phase φ _s can cause a relatively large variation in the intensity I of the delivered beam.

The programmable control device 50 is configured to act on the phase shift Δφ between the voltages Vι and N _{2 in} order to modify the shape of the curve shown in FIG. 4 and the efficiency of the grouping of particles, therefore the intensity at exit from the cyclotron.

By acting on the phase shift Δφ, it is thus possible to act on the intensity I and bring it to the desired value.

The actuator 40 can be produced otherwise than with two groupers without departing from the scope of the present invention. It may for example comprise a movable element 70, as illustrated in FIG. 6, rotating around a geometric axis of rotation Y and comprising several openings which can be placed in the path of the beam, for example two openings 71 and 72 of different diameters . Depending on the selected aperture, a more or less significant quantity of particles can be intercepted, which can make it possible to vary the intensity I of the beam delivered by the cyclotron.

The actuator can also include an electrostatic deflector, as illustrated in FIG. 7. This deflector can comprise, for example, two electrodes 75 and 76 and the beam propagating along the X axis can be intercepted thanks to the voltage applied to these electrodes 75 and 76. It is understood that by applying a sufficiently high pulse voltage between the electrodes, it is possible to chop the beam. Such an actuator makes it possible to control the intensity in all or nothing.

FIG. 8 shows an example of a programmed control law for the intensity of the beam of charged particles as a function of time. This law can be, as illustrated, a law in time slots, each time window having for example an amplitude lower than that of the previous time window.

Such an intensity control law can be useful when processing an area 80 of the human body, shown diagrammatically in FIG. 9. This area 80 may be, for example, a tumor to be destroyed, and may be divided into strata 81 located at different depths. Treatment can be started with a relatively high intensity particle beam to treat the deepest strata. The programmed intensity law can make it possible to reduce the intensity to take into account, when processing the shallowest strata, of the fact that the latter have already received a significant dose of radiation during the passage of the beam intended to treat the strata the deepest.

The intensity control can be correlated to the position of the beam at the output of the deflection device 41. The latter can be controlled by the control device 50.

Figures 10 and 11 illustrate other non-limiting examples of control laws that can be programmed, for example sawtooth, possibly of non-constant amplitude (Figure 10) or according to any curve of shape (Figure 11 ).

The particle accelerator can have a single cyclotron to accelerate particles.

It can also include a post-acceleration element to accelerate the particles continuously as they exit the cyclotron. The accelerator can thus, for example, as illustrated in FIG. 12, comprise two cyclotrons, namely a first cyclotron 20 ′, for example of the compact isochronous type, surrounded by a second cyclotron 20 ″ for example of the isochronous type with separate sectors.

Molecular ions, for example H ₂ ⁺ , can be accelerated in the first cyclotron 20 'and directed to an electronic peeler located in the second cyclotron. The crossing of this peeler makes it possible to generate a beam of H protons. The intensity of the beam can be measured on this peeler and the output phase φ _s of the beam injected into the first cyclotron can be controlled by a programmable control device in a similar manner to what has been previously described.

It is not beyond the scope of the present invention when the accelerated particles are particles other than H ^" or H ⁺ , for example H ₃ or D ^" .

The invention is not limited to the examples which have just been described.

One can in particular use other actuators and intensity sensors.

Throughout the description, the expression "comprising a" must be understood as being synonymous with "comprising at least one", unless otherwise specified.

Claims

Particle accelerator, comprising: a source (10) capable of generating a beam of charged particles to accelerate, at least one cyclotron (20; 20 ', 20 ") to accelerate particles from the source,

- at least one actuator (40) for acting on the particles of the beam before their acceleration by the cyclotron, - at least one sensor (33) capable of delivering information representative of the intensity of the beam of particles accelerated by the cyclotron, and

- a programmable control device (50) capable of acting on the actuator as a function of the information delivered by the sensor and of a programmed control law of the intensity of the particle beam accelerated over time, so as to that the intensity of the beam delivered by the cyclotron respects the programmed control law.

2. Accelerator according to claim 1, characterized in that the sensor comprises a peeler (33) crossed by the beam of particles accelerated by the cyclotron.

3. Accelerator according to the preceding claim, characterized in that the peeler is an electronic peeler (33).

4. Accelerator according to any one of the preceding claims, characterized in that the actuator comprises at least one electrostatic deflector (75, 76).

5. Accelerator according to any one of the preceding claims, characterized in that the actuator comprises at least one movable member (70) capable of intercepting particles of the beam.

6. Accelerator according to any one of the preceding claims, characterized in that the actuator comprises at least one grouper (21, 22).

7. Accelerator according to the preceding claim, characterized in that the actuator (40) comprises two consolidators (21, 22).

8. Accelerator according to claim 7, characterized in that the control device is configured to modify the phase difference between the voltages applied to the two groupers according to the information delivered by the sensor.

9. Accelerator according to one of the two immediately preceding claims, characterized in that each grouper comprises a central electrode (60; 63) having a variable potential over time, disposed between two end electrodes (61, 62; 64 , 65) at the same potential, and creating with each of these a potential difference, and by the fact that the length of the central electrode (60) of the grouper (21) crossed first by the beam is twice that of the central electrode (63) of the grouper (22) crossed in second by the beam.

10. Accelerator according to any one of claims 7 to 9, characterized in that the voltages applied to the consolidators (21, 22) correspond substantially to the first terms of the decomposition in Fourier series of a sawtooth signal.

11. Accelerator according to any one of the preceding claims, characterized in that the programmed current law comprises, as a function of time, at least two slots, in particular of different amplitudes.

12. Accelerator according to any one of the preceding claims, characterized in that the source (10) is capable of generating molecular ions.

13. Accelerator according to the preceding claim, characterized in that the source is capable of generating H ₂ ⁺ or H ₃ ⁺ ions.

14. Accelerator according to any one of claims 1 to 11, characterized in that the source (10) is capable of generating H ^" ions.

15. Accelerator according to any one of claims 1 to 11, characterized in that the source (10) is capable of generating D ⁺ ions.

16. Accelerator according to any one of the preceding claims, characterized in that the programmable control device (50) has a response time less than or equal to 10 μs, preferably less than or equal to 5 μs.

17. Accelerator according to any one of the preceding claims, characterized in that it comprises at least one post-acceleration element (20 ") operating continuously.

18. Accelerator according to any one of the preceding claims, characterized in that it comprises two cyclotrons (20 ', 20 ").

19. Accelerator according to the preceding claim, characterized in that it has a first cyclotron (20 ') associated with the source and a second cyclotron (20 ") to accelerate particles from the first cyclotron.

20. Accelerator according to the preceding claim, characterized in that the sensor comprises a peeler disposed inside the second cyclotron, the particles accelerated by the first cyclotron leaving the latter without passing through a peeler.

21. Accelerator according to any one of the preceding claims, characterized in that it comprises a deflection device (41) making it possible to carry out a scanning of a predetermined area (80), in particular a region of the human body, with the beam of accelerated particles.

22. Accelerator according to the preceding claim, characterized in that the programmable control device (50) is arranged to modify the intensity of the beam of accelerated particles as a function of the position of the beam.

23. Method for producing a beam of accelerated particles having an intensity varying in a programmed manner over time, characterized in that it comprises the following step:

- Program the programmable control device (50) of the accelerator (1) as defined in any one of the preceding claims as a function of the desired intensity variation.

24. Method according to the preceding claim, characterized in that the control device (50) is programmed so as to, during a scanning of an area to be treated with the beam of accelerated particles, reduce the intensity of the beam in time to take into account the dose received by the different regions of the treated area when these pass through the beam to treat the deepest regions.

25. The method of claim 24, characterized in that the control device (50) is programmed so that the intensity of the particle beam changes in slots of decreasing amplitude over time.

26. Use of an accelerator as defined in any one of claims 1 to 22 to power an accelerator-controlled system.

27. Use according to the preceding claim, characterized in that the accelerator-controlled system comprises an energy amplifier, a nuclear reactor under criticism or a transmitter of nuclear waste.

28. Use of an accelerator as defined in any one of claims 1 to 22 to produce a neutron flux, in particular of substantially mono energetic neutrons.