DE102013010589A1 - Acceleration of ions used in e.g. cancer therapy, involves injecting gaseous mixture containing gas component containing hydrogen by nozzle into vacuum, irradiating pulsed laser light to gaseous mixture, ionizing, and accelerating - Google Patents

Abstract

Acceleration of ions involves injecting gaseous mixture containing gas component (A) containing hydrogen and gas component (B) by a nozzle into a vacuum, irradiating pulsed laser light to the gaseous mixture, ionizing the gas clusters in the gaseous mixture and accelerating. The density of clusters in the gas cluster is 2x 10 8>-2x 10 1> 0> cm -> 3>. Independent claims are included for the following: (1) ion irradiation device; and (2) medical ion irradiation device.

Description

[Technical part]

The present invention relates to ion acceleration methods in which the desired ions are accelerated and released to high energies, and ion accelerating devices. The invention further relates to the construction of ion irradiation devices based thereon, medical ion irradiation devices and nuclear fission ion irradiation devices.

[Technical background]

Various techniques are known for accelerating ions (including protons) and irradiating materials for processing, coating, analysis, medical treatment, etc. with the appropriate ion beams. Such techniques require the stable generation of an ion beam of high energy and high intensity. Devices for generating high energy ion beams and for irradiation generally require expensive equipment, particularly with regard to the mechanisms for accelerating ions to high energies, which makes the devices overall large. Accordingly, although such ion irradiation devices have been unequivocally established for medical use in particular, they have not been found to be sufficiently widespread.

As a way of allowing miniaturization against this background, ion irradiation devices based on laser-driven acceleration mechanisms are known. In laser-driven ion irradiation apparatuses, as described in Patent Documents 1 and 2, a target capable of generating protons and the desired ions in larger numbers is irradiated with ultrashort pulsed laser light of high intensity, thereby evaporated and thus transferred to the plasma state. In this plasma, the electrons whose mass is lower are first accelerated to high energies; The electric field generated by these accelerated electrons then accelerates the heavier protons and ions. These protons and ions are used as a high energy beam to irradiate materials. The acceleration fields used in prior art accelerators are limited by the dielectric strength of the material, etc., and therefore can only operate at low maximum values; In contrast, the acceleration fields generated in this plasma are stronger by several orders of magnitude and accordingly allow acceleration to high energies over short distances. As a result, these laser-operated ion irradiation devices can be made substantially more compact overall than was the case with the large prior art accelerators, etc. In various areas, for example for medical purposes, practical applications are to be expected.

For example, for medical purposes, it is necessary to irradiate diseased parts of the body at a specific position and depth (and only these) in a concentrated manner with ions of high energy. For this purpose, monochromatic ion beams of high energy (with delta-functional energy spectrum) must be generated in a highly concentrated manner. Efforts are therefore being made to realize laser-driven ion irradiation devices whose characteristics are at least equivalent to those of large prior art accelerators.

An effective technique is to select as the target object, ie as a plasma source, which is irradiated with the laser, no normal gases or solids, but "gas cluster"; This technique is described in Non-Patent Document 1 and Patent Document 3. "Gas clusters" are aggregates (clusters) of particulate accumulated atoms and molecules that are distributed in the air; the properties of such gases are between those of normal gases and those of solids. Here it was shown that helium (He), carbon (C) and oxygen ions (O) can be generated with particularly high energies, if a gas cluster is used as a dispersion of CO ₂ clusters in helium. Such gas clusters can be obtained by adiabatic expansion by injecting the appropriate gas mixture through a nozzle into a vacuum.

In particular, in the technique described in Non-Patent Document 1 and Patent Document 3, the plasma density distribution in the gas cluster is optimized by adjusting the conditions of the laser light irradiation; As a result, the energy and concentration of the ion beam can be increased. In particular, by using gas clusters with helium gas, helium, carbon and oxygen ion beams can be generated at high energies of 10 to 20 MeV per nucleon, which has been difficult with prior art laser powered designs.

Nonpatent Document 2 describes a technique in which hydrogen ions (protons) are accelerated by irradiation of microconical targets with laser light and energies of 80 J up to 67.5 MeV.

Such devices for ion acceleration (ion irradiation devices) allow the generation of high-intensity ion beams with high intensity.

[Prior Art Documents]

[Non-patent documents]

• [Non-patent document 1] "Energy increase in multi-motion acceleration in the interaction of a short-pulse laser with a cluster-gas target"; Y. Fukuda, A. Ya. Faenov, M. Tampo, TA Pikuz, T. Nakamura, M. Kando, Y. Hayashi, A. Yogo, H. Sakaki, T. Kameshuma, AS Pirozhkov, K. Ogura, M. Mori, T. Zh. Esirkepov, J. Koga, AS Boldarev, VA Gasilov, AI Magunov, T. Yamauchi, R. Kodama, PR Bolton, Y. Kato, T. Tajima, H. Daido and SV Bulanov; Physical Review Letters, Vol. 103, p. 165002 (2009) ,
• [Non-Patent Document 2] "Increased laser-accelerated proton energy via direct laser-light-pressure acceleration of electrons into microcone targets"; SA Gaillard, T. Kluge, KA Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, DT Offermann, M. Schollmeier, Y. Sentoku, and TE Cowan; Physics of Plasmas, Vol. 18, p. 056710 (2011) ,

[Patent Documents]

• [Patent Document 1] Laid-Open Publication No. 2006-244863 A
• [Patent Document 2] Laid-Open Publication 2008-198566 A
• [Patent Document 3] Laid-Open Publication 2012-119065 A

Summary of the Invention

OBJECT OF THE INVENTION

However, the energy of helium, carbon and oxygen ion beams per nucleon generated by the technique described in Non-Patent Document 1 and Patent Document 3 is about 10 to 20 MeV at the maximum. Also in the technique described in Non-Patent Document 2, the energy of the protons is at most 67.5 MeV. While these energies are higher than conventional laser-driven ion irradiation devices; However, since an energy of around 80 to 250 MeV is required, for example, for the hydrogen ion (proton) radiation used in cancer therapy, the given energies are not sufficient for such applications.

It was therefore difficult to generate stable ion beams with sufficiently high energies for use in cancer therapy by means of laser-driven acceleration mechanisms.

Purpose of the present invention is to provide a solution to the problems described in view of the above-described problems.

[Solution of the task]

The present invention solves the problems mentioned by the structure described below.

The method for ion acceleration according to the present invention is characterized in that
a gas mixture of a first gas component, which consists predominantly of hydrogen, and a second gas component is injected through a nozzle in a vacuum, whereby a cluster consisting of the molecules of the second gas component dispersed in the 1st gas component,
and this column-shaped gas cluster formed by the nozzle is irradiated with pulsed laser light approximately perpendicularly to the injection direction of the gas mixture,
whereby the gas cluster is transferred to the plasma state and the atoms forming the gas cluster are ionized and accelerated,
for the density of the cluster in the gas cluster, a range between 2.0 × 10 ⁸ and 2.0 × 10 ¹⁰ cm ^{-3 is} selected
and the pulsed laser light is focused from the central axis of the columnar gas cluster in the emission direction of the pulsed laser light to a position between 10 and 150% (here, the opening diameter of the nozzle is 100%).

The method for ion acceleration according to the present invention is further characterized in that a duration of 0.01 to 10 ms is selected for the gasification of the gas mixture, and that the column-shaped, formed in accordance with the injection duration gas cluster in the range of 10 to 20% of this injection period from clustering is irradiated with the pulsed laser light.

The ion acceleration method of the present invention is further characterized in that the second gas component is CO ₂ .

In the ion accelerating apparatus of the present invention, a gas cluster is irradiated with pulsed laser light and transferred to the plasma state, and the atoms forming the gas cluster are ionized and accelerated; the device has
a nozzle through which a gas mixture of a first gas component consisting mainly of hydrogen and a second gas component is injected into a vacuum, thereby producing a columnar gas cluster in which a cluster consisting of the molecules of the second gas component in the 1st gas component dispersed,
a laser light source that generates a pulsed laser light,
and a focusing optics which focuses the pulsed laser light for irradiation of the gas cluster at a preset focus point,
and is characterized in that, for the density of the cluster in the gas cluster, a range between 2.0 × 10 ⁸ and 2.0 × 10 ¹⁰ cm ^{-3 is} selected, and the focus is selected from the central axis of the columnar gas cluster in the emission direction of the laser light is in a position between 10 and 150%, with the opening diameter of the nozzle being 100%.

The device for ion acceleration according to the present invention is further characterized in that for the Einspitzung of the gas mixture, a duration of 0.01 to 10 ms is selected, and that the columnar, formed according to the injection duration gas cluster in the range of 10 to 20% of this injection period from clustering is irradiated with the pulsed laser light.

The ion accelerating apparatus of the present invention is further characterized in that the second gas component is CO ₂ .

The ion irradiation apparatus of the present invention is characterized by having a structure in which materials are irradiated with the ions accelerated by the ion accelerating apparatus.

The medical ion irradiation apparatus according to the present invention is characterized in that it has a structure in which diseased body parts are irradiated with the ions accelerated by the ion accelerating apparatus.

The nuclear fission ion irradiation apparatus of the present invention is characterized by having a structure in which materials are irradiated with the ions accelerated by the ion accelerating apparatus.

[Advantages of the invention]

The above-described construction of the present invention makes it possible to generate stable hydrogen ion (proton) rays with sufficiently high energies for use in cancer therapy by means of laser-driven acceleration mechanisms.

[Brief explanation of the figures]

[ 1 ] Schematic representation of the structure of an apparatus for ion acceleration according to an embodiment of the present invention

[ 2 ] Representation of the time course of on / off control of the nozzle, generated gas cluster amount and output of the pulsed laser light in an apparatus for ion acceleration according to an embodiment of the present invention

[ 3 ] Measurement results for distributing the gas injected through the nozzle in an ion accelerating apparatus according to an embodiment of the present invention; Measurement in the shadow method when irradiating the gas cluster with sample light

[ 4 ] Measurement results on the focus position dependency of the X-ray intensity and the probability of the formation of high-energy electrons

[ 5 ] Measurement results of the proton beam generated by an ion accelerating apparatus according to an embodiment of the present invention

[ 6 ] Measurement results on the number of generated protons with high energy when focusing on the generation of high-energy electrons and on the origin of X-rays

Embodiments of the Invention

Hereinafter, an ion accelerating apparatus according to an embodiment of the present invention will be explained. shows the structure of this device for ion acceleration 10 , The left part of this figure shows the structure in the overall picture, while the right part shows a detail (the area inside the dotted line) enlarged. The structure is similar to that described in Patent Document 3, but the composition of the gas clusters and the conditions of the laser light irradiation differ.

From a laser light source becomes laser light (pulsed laser light) 20 generated to cluster and gas molecules in the gas cluster (target object) 30 into the plasma state. For this purpose, the structure is chosen so that the laser light 20 to the interior of the gas cluster 30 and its environment is focused. As a laser light source, a structure can be used which, with appropriate focusing by the focusing optics 21 ultrashort pulsed laser light generated in sufficient intensity to the gas cluster 30 into the plasma state. In this point, the structure is the same as that described in Patent Documents 1 and 2 and Non-Patent Document 1 and Patent Document 3. Concretely, laser lasers and titanium: sapphire lasers can be used as the laser light source. As focusing optics 21 For example, aspherical focusing mirrors such as extra-axial parabolic mirrors can be used. The by means of focusing optics 21 set focus position will be explained later. The laser light 20 is generated pulsed at short intervals; the time course of the irradiation (excitation) becomes synchronous with the generation of the gas cluster 30 controlled.

The nozzle 40 is installed in a vacuum and is constructed so that gas is injected into the vacuum at its tip. When injection of this gas, which is a gas mixture of hydrogen (1. Gas Component: H ₂₎ and carbon dioxide (the second gas component: CO ₂₎ is, in the vacuum produced due to the rapid temperature drop by adiabatic expansion of a columnar gas cluster 30 in that the CO ₂ goes into the solid state and disperse clusters of CO ₂ in the H ₂ . Since the space into which this gas is injected is emptied by means of a vacuum pump (not shown), a sufficiently strong vacuum can be maintained even after injection of the gas in order to produce a stable gas cluster. In this point, the structure is the same as that described in Non-Patent Document 1 and Patent Document 3. The gas injection is not continuous, but pulsed. Therefore, the injection and the irradiation with laser light 20 synchronously controlled. As in the right part of shown are the injection direction of the gas mixture and the direction of irradiation of the laser light 20 approximately perpendicular to each other. By moving the nozzle 40 in the direction of the axis of the laser light 20 allows the focus position of the laser light 20 in the gas cluster 30 Taxes.

As in the right part of shown, it is the gas cluster 30 one from H ₂ molecules 31 existing gas, into the CO ₂ cluster 32 - Disperse nanoparticulate aggregates of CO ₂ molecules. With increasing distance from the nozzle 40 decreases the concentration of H ₂ molecules 31 and CO ₂ clusters 32 because they spread by heat movement; accordingly, the laser light 20 in the gas cluster 30 near the opening of the nozzle 40 focused and chosen a job with a particularly high intensity. The technique described in Patent Document 3 occurs in the gas cluster 30 a gas mixture of He molecules and CO ₂ molecules is used; He, C and O ions are generated and these ions, each having the same mass-to-charge ratio, accelerated. In contrast, comes with this device for ion acceleration 10 Instead of He gas, a gas mixture of H ₂ molecules and CO ₂ molecules are used, are generated from the H, C, and O ions; Therefore, by appropriately defining the focus position and the time of irradiation with laser light, hydrogen (H) ions whose mass-to-charge ratio is lowest can be specifically accelerated.

The timing of opening (ON) and closing (OFF) of the nozzle 40 , the amount of gas clusters generated 30 in the focal point as well as the emission of the laser light 20 is schematic in to (c).

This is the generation of the gas cluster 30 in the focal point (b) with respect to the time course of the opening and closing of the nozzle 40 (a) Delayed by the time the gas needed to move from the nozzle 40 to flow to the focal point; the gas cluster production is extended as far as time for the opening and closing of the nozzle 40 is needed. This delay time depends on the distance between the nozzle 40 and focus point as well as the velocity of the gas flow. The larger this distance, the longer the delay time will be.

The duty cycle of the nozzle 40 is typically about 0.01 to 10 ms; the switching on and off is controlled by an external signal. Turning on the gas cluster 30 becomes synchronous to the emission of the laser light 20 (c) controlled; taking into account the said delay times, the control is practically so that the switching on and off of the nozzle 40 (Times t ₁ and t ₂ ) on the one hand and the output of the laser light 20 (Times t ₃ and t ₄ ) on the other hand are synchronous with each other. The emission of the laser light 20 is composed of a main pulse of high intensity and a lower pulse of the pre-pulse preceding the main pulse, as described in Non-Patent Document 1. The time offset between pre-pulse and main pulse (time offset between t ₄ and t ₃ ) is about 1 to 1000 ps (for example, about 150 ps). The half width for pre-pulse and main pulse is equally about 3 to 1000 fs (for example, about 40 fs). These times in the control of the laser light 20 are compared to the aforementioned duty cycle of the nozzle 40 t ₂ -t ₁ of negligible duration. In the mentioned device for ion acceleration 10 the delivery time of the main pulse t _{4 is} fixed, while the turn-on time t _{1 of} the nozzle 40 is adjusted relative to the emission time of the main pulse t _{4 in} order to define the time of irradiation with laser light t ₄ -t ₁ during which an effective ion acceleration takes place.

By this construction, as described in Non-Patent Document 1, both H ₂ molecules 31 as well as CO ₂ clusters 32 in the gas cluster 30 dispersed and transferred to the plasma state to generate and accelerate electrons. These accelerated electrons generate an electromagnetic field structure in the plasma and a high intensity electric field that accelerates the ions. As in As shown, this electric field becomes an ion beam 50 from the high-energy accelerated carbon (C) produced in the plasma 51 , Oxygen (O) 52 and hydrogen (H) ions 53 generated.

The inventors have the circumstances in the irradiation of this gas cluster 30 with laser light 20 analyzed experimentally and were able to determine that the emitted ions can be accelerated to high energies by defining in particular the focus position and the time of irradiation with laser light. In the gas cluster 30 can be adjusted by changing the focus position in the emission direction of the laser light 20 adjust the circumstances of the plasma formation inside, the electron acceleration and the ion acceleration. Properties such as the energy distribution of the accelerated ions thus change depending on the focus position. In this point, the structure corresponds to that described in Patent Document 3; however, it was noted in particular that hydrogen (H) ions 53 whose mass-to-charge ratio is lowest, can be specifically accelerated to high energies by defining the focus position in a range other than that described in Patent Document 3. The energy of the hydrogen ions obtained 53 is orders of magnitude higher than the energy of He ions obtained by the technique described in Patent Document 3. It can therefore be with this device for ion acceleration 10 produce a proton beam whose energy is particularly high compared to the prior art.

The following are the results of experiments are explained, in which using this device for ion acceleration 10 Hydrogen ion (proton) rays were accelerated. Here, the time of irradiation with laser light t ₄ -t _{1 was} after at 0.45 ms and the duty cycle of the nozzle 40 t ₂ -t ₁ at 1 ms; the half width of the main pulse was 40 fs, the energy at 1 J and the contrast ratio of the pre-pulse at 10-10. shows the results of measurement of the electron density distribution in the emission direction of the laser light 20 when injecting a gas mixture of 70% H ₂ and 30% CO ₂ from the nozzle 40 (Opening diameter 2 mm) with a pressure of 60 bar in a chamber with a base pressure of 5 · 10 ^-5 (measurement in the shadow method). This was the gas cluster 30 irradiated with a sample light and measured from the opposite direction of this irradiation. As in showed, with the said gas mixture a gas cluster 30 produced by approximately cylindrical shape, which was somewhat wider than the opening of the nozzle 40 (2 mm), in the essential parts of the distribution, however, corresponded to this opening (2 mm). In the focal point corresponds to the front edge of the nozzle opening 40 in the emission direction of the laser light 20 (This point is referred to in the following descriptions as "100% front").

The relationship between the density D of the CO ₂ clusters and the radius r of the CO ₂ clusters can be expressed by the following formula, where D is the density of the CO ₂ clusters in the gas cluster 30 (cm ^-3 ), ρ the density of the CO ₂ molecules in the gas cluster 30 (cm ^-3 ), S is the CO ₂ density in solid CO ₂ (cm ^-3 ) and r is the radius of the CO ₂ clusters.

[Formula 1]

• r = (3ρ / 4πDS) ^1/3 (1)

The values for ρ and S are, for example, when the said gas mixture (H ₂ : 70%, CO ₂ : 30%) is used at 60 atm: ρ = 7.0 × 10 ¹⁸ cm ^-3 and S = 2.1 · 10 ²² cm ^-3 ; from this, formula (1) gives r = (8 × 10 ^-5 / D) ^1/3 .

In non-patent document 1, generated ion beams are collected with a solid-state track detector (CR39) and their traces are visualized and assessed two-dimensionally. Properties such as the energy distribution of the accelerated ions depend on the focus position; However, since the CR39 is difficult to estimate with high accuracy an optimum position for generation of high-energy ions, as in Patent Document 3, conditions have been worked out from the following measurement results under which ions are more likely to be accelerated to high energies. Here was a gas cluster 30 with D = 1.5 · 10 ⁹ cm ^-3 (r = 0.3 μm) with laser light 20 irradiated and the detected X-ray intensity upon displacement of the focal point in the direction of the axis of the laser light 20 measured. The reference point for the focus position was the center of the nozzle 40 (Central axis of the gas cluster 30 of approximately cylindrical shape). Here, the measured X-rays showed energies of 665.7 eV and 653.7 eV corresponding to the helium beta line (He _β ) for hexavalent oxygen ions (O ₆₊ ) and the Lyman alpha line (Ly _α ) for seven-valent oxygen ions (O ₇₊ ); this specific X-ray intensity corresponds to the generated plasma density. However, since X - rays are characteristic X - rays produced by random shock excitation of high - energy electrons, Emission of X-rays not directed - the X-rays detected here are from the entire gas cluster 30 ,

At the same time, the probability of origin of high-energy electrons (electrons with energies of at least 12.2 MeV) per irradiation with laser light was determined 20 examined.

The results of these measurements are in shown. The area between the two dashed lines shows the opening of the nozzle 40 (Diameter 1 mm). The X-ray intensity rises from the center of the nozzle 40 (in the position 0 mm on the horizontal) seen from a rear focal point (in on the right) in a range of 100% (in the position 1 mm on the horizontal) to 250% (dto 2.5 mm) (distance each converted to a reference of 100% equal radius of the nozzle 40 ) and occupies the largest value at a position of 200% (X-ray range). The reason is that the intensity of the laser light 20 also at locations away from the focal point (the point with the highest light intensity) is sufficiently large to transfer particles in the plasma state, and that the cross-sectional area on which X-ray radiation can be generated by shock excitation, here is the largest. Between the X-ray intensity and the probability of emission of high-energy electrons of at least 12.2 MeV, a reverse correlation can be observed. This can be attributed to the fact that when focusing on the center of the gas cluster 30 the energy of the resulting electrons is too large and the cross-sectional area on which X-rays can be generated by shock excitation, here is considerably smaller.

The probability of origin of high energy electrons is from the center of the nozzle 40 from a front focal point in a range of 10% (1 mm) to 150% (1.5 mm) highest and assumes stable values. While further in the technique described in Patent Document 3 (using He instead of H ₂ for the gas cluster 30 ) Bubble structures in the gas cluster 30 by the irradiation with laser light 20 could be observed here, as in shown, no bubble structures are detected.

As in the case described in Patent Document 3, even with the structure described above, electrons of lower mass are first accelerated, thus producing electrons of high energy. As a result, an electromagnetic field structure is formed in the plasma and a strong electric field is created (rapid potential change). Ions heavier than electrons are then accelerated by this electric field; it generates ions with high energy. Therefore, for the generation of high-energy ions, it is first necessary to generate a large number of high-energy electrons. In this case, bubbles form with the technique described in Patent Document 3, in the interior of which are particularly effective ions are accelerated. By contrast, the use of H ₂ gas according to the present application does not lead to the formation of bubble structures. It is therefore considered that ion acceleration is most effective when higher energy electrons are generated in larger numbers. It is obvious that first the gas cluster 30 transferred to the plasma state and the ions to be accelerated must have been generated.

The results of the spectral measurement of the proton (hydrogen ion) beam, which at a focal point in a range of 10% to 150% front of the center of the nozzle 40 (high probability range for high energy / high energy electrons) has been generated in shown. The peak energy here is about 135 MeV, but the spectrum extends even further to a maximum of about 500 MeV. This energy is an order of magnitude higher than the technique described in Patent Document 3. Also, in comparison with the technique for accelerating protons by laser light described in Non-Patent Document 2, protons can be accelerated to higher energies by using low-energy laser light of 1 J (in the technique described in Non-Patent Document 2: 80 J).

Taking into account the fact that 1. no bubble structures can be observed and that 2. the energy of the ions (protons) is enormously high, in the case of the above-mentioned device for ion acceleration 10 Although it is assumed that the structure of the devices is similar, but the acceleration is carried out via a different acceleration mechanism than in the technique described in Patent Document 3. However, it is obvious that high energy electrons are the main cause of proton acceleration.

The measured results for the generated number of protons having an energy of at least 200 MeV each at a focal point in a range of 70% to 100% front side from the center of the nozzle 40 from a high energy electron region and at a focal point in a range of 20% to 300% at the back of the center of the nozzle 40 (X-ray area) are in shown. From these results it is obvious that protons with high energy can be generated highly effectively at a focal point in the high-energy electron field.

Within the scope of these results, the optimal focus position for generating a high energy proton beam is, as mentioned, in the range of 10% to 150% front side of the center of the nozzle 40 seen from. In this case, this device can be used for ion acceleration 10 also in medical ion irradiation devices, which was difficult to realize with the technique described in Patent Document 3.

The fact that in the emission direction of the laser light 20 strong acceleration fields arise, means that the bundling degree of the ions increases there. By choosing a focal point in the region of the positions mentioned, a high degree of bundling can thus also be achieved. Thus, with the mentioned device for ion acceleration 10 So apparently also achieve a higher degree of bundling than with the technique described in Patent Document 3.

The previous discussion referred to the spatial limitations of laser light irradiation 20 , Practically, gas clusters are created 30 however, as in shown, also limited in time. Therefore, it is necessary to know the timing of the generation of the gas cluster 30 ( ) and the time of irradiation with laser light 20 ( ) match each other.

The generation time of the gas cluster 30 is how in shown, almost as long as the duty cycle of the nozzle 40 and is about 0.01 to 10 ms (for example, 1 ms). If this duration is too short, no gas cluster can 30 be generated in sufficient quantity, which makes it difficult to generate an ion beam of sufficient intensity. If this duration is too long, the background vacuum into which the gas mixture is injected reduces, whereby sufficient adiabatic expansion of the gas no longer takes place and it becomes difficult to form CO ₂ clusters 32 in the gas cluster 30 to create. This duration is above all in comparison to the distance between pre-pulse and main pulse of the laser light 20 , to the half-width of the pre-pulse and the main pulse, to the duration of the plasma generation and to the duration until the emission of electrons and ions in the gas cluster 30 orders of magnitude longer. As long as in the gas cluster 30 as mentioned H ₂ molecules 31 and CO ₂ clusters 32 can be generated, therefore, the irradiation time can be chosen freely.

The reduction of the vacuum with a long duty cycle depends on factors such as the structure of the vacuum chamber and the evacuation rate of the vacuum pump used; however, obviously the background vacuum is towards the end of the duty cycle of the nozzle 40 reduced. It is therefore assumed that gas cluster 30 practically only at the beginning of the duty cycle of the nozzle 40 generate stable. For example, it is advantageous if the irradiation with laser light 20 for example, during the first 10 to 20% of the time between turning on and turning off the nozzle 40 he follows. In the mentioned device for ion acceleration 10 was the time of irradiation with laser light t ₄ -t ₁ at 0.45 ms and the duty cycle of the nozzle 40 t ₂ -t ₁ defined with 1 ms. The practical duration of gas cluster production was about taking into account the delay for opening and closing the nozzle 40 required time 1.6 ms. Taking into account the delay time until the gas from the nozzle 40 flows to the focal point, the irradiation with laser light 20 in the example mentioned, 0.25 ms after the gas cluster generation in the focal point, ie in the first 16% of the generation period of the gas cluster.

In the example mentioned, D = 1.5 × 10 ⁹ cm ^-3 ; However, the same applies to the entire range of 2.0 × 10 ⁸ to 2.0 × 10 ¹⁰ cm ^-3 .

In the description of said construction, it was assumed that a gas mixture of H ₂ and CO ₂ and gas clusters with CO ₂ clusters are used. The same applies, however, when using differently constructed gas mixtures and differently formed cluster types.

In the mentioned device for ion acceleration can be controlled by control v. a. the focus position of the laser light (focusing optics) and the timing of opening and closing of the nozzle for injection of the gas mixture (time of irradiation with laser light) gain a high-quality ion beam. It can therefore be realized with laser-driven devices for ion acceleration according to the prior art, without the device structure itself would have to be changed greatly. Thus, the device as a whole can be made more compact in comparison with other types of accelerator devices and allows for use in medicine and numerous other fields.

A structure for irradiating materials with the ions accelerated by this ion accelerating apparatus can therefore be used as the ion irradiation apparatus for irradiating ion beams of various ions. In prior art ion irradiation devices, the mechanisms for ion acceleration with cyclotrons, high frequency cavities, etc., are larger, and compact design of the devices as a whole has heretofore been difficult. On the other hand, in this ion irradiation apparatus as described, such accelerating mechanisms can be made compact, whereby the apparatus as a whole can be made compact. Accordingly simple is the introduction of this ion irradiation device in a variety of facilities, such as medical facilities; it can be used particularly advantageously as a medical ion irradiation device. This applies not only to the application as a medical ion irradiation device, but equally also for use as an ion irradiation device for nuclear fission, in which a nuclear fission reaction is triggered by irradiation with an ion beam of high energy.

LIST OF REFERENCE NUMBERS

10

Device for ion acceleration

20

Laser light (pulsed laser light)

21

focusing optics

30

Gas cluster (target object)

31

Hydrogen molecules (H ₂ )

32

CO ₂ cluster

40

jet

50

ion beam

51

Carbon ions (C)

52

Oxygen ions (O)

53

Hydrogen ions (H)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• "Energy increase in multi-motion acceleration in the interaction of a short-pulse laser with a cluster-gas target"; Y. Fukuda, A. Ya. Faenov, M. Tampo, TA Pikuz, T. Nakamura, M. Kando, Y. Hayashi, A. Yogo, H. Sakaki, T. Kameshuma, AS Pirozhkov, K. Ogura, M. Mori, T. Zh. Esirkepov, J. Koga, AS Boldarev, VA Gasilov, AI Magunov, T. Yamauchi, R. Kodama, PR Bolton, Y. Kato, T. Tajima, H. Daido and SV Bulanov; Physical Review Letters, Vol. 103, p. 165002 (2009) [0009]
• "Increased laser-accelerated proton energy via direct laser-light-pressure acceleration of electrons into microcone targets"; SA Gaillard, T. Kluge, KA Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, DT Offermann, M. Schollmeier, Y. Sentoku, and TE Cowan; Physics of Plasmas, Vol. 18, p. 056710 (2011) [0009]

Claims (9)

A method for ion acceleration, characterized in that a gas mixture of a first gas component, which consists primarily of hydrogen, and a second gas component is injected through a nozzle into a vacuum, whereby a cluster consisting of the molecules of the second gas component in the 1 Gas component is dispersed, and this is irradiated from the nozzle columnar gas cluster approximately perpendicular to the injection direction of the gas mixture with pulsed laser light, whereby the gas cluster is transferred to the plasma state and the gas cluster forming atoms are ionized and accelerated, wherein the density of the cluster in the gas cluster is a range between 2.0 × 10 ⁸ and 2.0 × 10 ¹⁰ cm ^{-3 is} selected and the pulsed laser light is focused from the central axis of the columnar gas cluster in the emission direction of the pulsed laser light to a position between 10 and 150% (Here, the opening diameter of the nozzle applies as 100%). Method for ion acceleration according to claim 1, characterized in that for the Einspitzung of the gas mixture, a duration of 0.01 to 10 ms is selected, and that the columnar, formed according to the injection duration gas cluster in the range of 10 to 20% of this injection period from clustering with the pulsed laser light is irradiated. Method for ion acceleration according to one of claims 1 and 2, characterized in that the second gas component consists of CO ₂ . Device for ion acceleration, in which a gas cluster is irradiated with pulsed laser light and transferred to the plasma state and the atoms forming the gas cluster are ionized and accelerated, characterized in that this device for ion acceleration via a nozzle, through which a gas mixture of a first gas component consisting primarily of hydrogen, and a second gas component is injected into a vacuum, thereby producing a columnar gas cluster in which a cluster consisting of the molecules of the second gas component disperses into the first gas component, a pulsed laser light source Laser light generated, and a focusing optics which bundles the pulsed laser light for irradiation of the gas cluster at a pre-set focus point has, and characterized in that the density of the cluster in the gas cluster, a range between 2.0 · 10 ⁸ and 2.0 · 10 ¹⁰ cm ^{-3 is} chosen and the focus of the Mittelac of the columnar gas cluster is in the emission direction of the pulsed laser light in a position between 10 and 150%, wherein the opening diameter of the nozzle is considered 100%. Device for ion acceleration according to claim 4, characterized in that for the Einspitzung of the gas mixture, a duration of 0.01 to 10 ms is selected, and that the columnar, formed according to the injection duration gas cluster in the range of 10 to 20% of this injection period from clustering with the pulsed laser light is irradiated. Device for ion acceleration according to one of claims 4 and 5, characterized in that the second gas component consists of CO ₂ . Ion irradiation apparatus, characterized in that it has a structure in which materials are irradiated with the ions accelerated by an ion accelerating apparatus according to any one of claims 4 to 6. Medical ion irradiation device, characterized in that it has a structure in which diseased body parts are irradiated with the accelerated by an apparatus for ion acceleration according to any one of claims 4 to 6 ions. An ion irradiation apparatus for nuclear fission, characterized in that it has a structure in which materials are irradiated with the ions accelerated by an ion accelerating apparatus according to any one of claims 4 to 6.

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