LU102279B1 - A robotic gantry for radiation therapy comprising tuneable compact focusing system - Google Patents

Abstract

A particle beam transport method and a complete system used for the laser-driven electron FLASH radiation therapy is provided. A beam of particles is delivered from a laser driven accelerator and to the target (for treatment of patients) using a tuneable active plasma lens. In one embodiment, the system includes an active plasma lens as a beam focusing element that transport the beam at fixed energy to a point where the constant energy beam can be modified for use in radiation treatment. The size of the electron beam at the target depending on the electron beam energy and electron beam divergence is controlled by the tuneable strength of the plasma lens. Only one lens, placed behind of the LPA electron source, is needed to focus the electron beam in both horizontal and vertical planes, which allows to develop extremely compact irradiation system for radiation therapy.

Description

A robotic gantry for radiation therapy comprising tuneable compact focusing system Technical field

[001] The present invention relates to a method and a compact and flexible device capable to create, accelerate and deliver a focused electron beam. First object of the present invention is directed to the method for generating an accelerated electron beam and delivering a focused electron beam using a gas cell and an active plasma lens. The second object of the present invention is directed to a device capable to deliver a focused electron beam using the above-mentioned method. In a preferred embodiment, the electron beam is used for a radiation therapy, which can be used in a hospital or a centre for cancer treatment using radiation approach.

Background of the invention

[002] Radiation therapy is a well-known approach in treatment of different kind of cancer. Radiation therapy uses high-energy radiation such as X-rays, gamma-rays, electrons, protons, heavy ions, and neutrons to kill cancer cells by damaging their DNA. There is, however, a general need how to create and transport charge particles from the emitter (or a source of the particles) to a patient with sufficient intensity without significant losses during the beam transport.

[003] Laser-plasma accelerators provide electron beams with energy in a range of a few hundred MeV to several GeV with high bunch charge up to 100 pC. The electron bunch, accelerated by the high-power laser pulse with the pulse duration of ~ 30 fs, has the bunch length of ~ 10 fs. Usage of such electron beam for radiotherapy allows to deliver in a single short-pulse an ultra-high dose of more than 30 Gy/s, producing less treatment sessions than conventional dose-rate exposure (FLASH therapy). The reduction of the normal tissue complication probability (NTCP) associated to FLASH radiotherapy is very significant and the potential clinical benefit is very large. The laser- plasma accelerator approach attracts a great interest in the radiotherapy community. For the purpose of radiation therapy, the electron beam energy should not be more than 200 MeV. Laser plasma acceleration allows to produce such electrons in the laser- plasma interaction with the range of length ~ 1 cm, which opens a bright possibility to build a compact laser-based setup for radiotherapy. Such a laser plasma accelerator Page 1 from 22 can be a gas cell. The gas cell generally comprises a capillary. Gas or gases are fed LU102279 through a gas flow control system to the capillary. In some embodiment, it can be a two-stage gas cell separately fed by two gasses at the different pressures.

[004] Non-patent literature Laser-Driven Very High Energy Electron/Photon Beam Radiation Therapy in Conjunction with a Robotic System; Kazuhisa Nakajima; Appl. Sci. 2015, 5, 1-20; doi:10.3390/app5010001; Published: 29 December 2014, discloses a compact device suitable for radiation therapy. The device is capable to deliver an electron/photon beams to a patient. The device comprises a laser system for generating a high-power laser pulse; laser plasma accelerator for accelerating electrons; electron beam focusing system based on permanent quadrupole magnets; target system for a photon beam therapy, rotary ‘optical’ gantry, and laser beam stabilizing system. The beam transport system provides the electron beam focusing utilizing permanent quadrupole magnets. Compact ‘optical’ gantry contains the compact ‘in-vacuum’ laser beam transport is mounted by vacuum beam transport systems, a series of beam focusing quadrupole magnets with an electron beam diagnostic and a photon target with a collimation system.

[005] US 5,382,866 relates to a method of focusing a beam of charged particles. The method, resp. device, employs a plasma lens as an integral part of a beam guide system of an accelerator. The accelerator is not specified into details. The particle beam is intended to be focused onto a target by means of the plasma lens. An embodiment of the document discloses a capillary in between two electrodes. When the plasma lens is in used, operating gas, Ar or Hy, is under pressure from 0.5 to 10 mbar. Said particles are also mentioned in general and not defined into particular particle species.

[006] Non-patent literature “Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams; J. van Tilborg; PRL 115, 184802 (2015) PHYSICAL REVIEW LETTERS; DOI: 10.1103/PhysRevLett.115.184802” discloses an active plasma lens for focusing a 100 MeV electron beam generated by a laser-plasma accelerator. The laser-plasma accelerator is a gas-jet. A capillary-discharge plasma channel consisting of a few cm hollow tube of diameter 250 — 1000 um serves as an active plasma lens. The capillary discharge is filled with Hz gas at pressures of order 10-200 Torr. The document further discloses that the device comprising a laser beam capable to generate and accelerate an electron beam via laser-matter interaction, also known as Page 2 from 22 a laser-plasma accelerator is particularly suitable for focusing the electron beam onto LU102279 a target. It is generally known that the gas jet requires a lot of gas supply for generation of electron, which is the main disadvantage of this solution. Furthermore, the gas jet must be synchronized with the laser pulse to produce sufficient density of electron beam.

[007] Thus, it is an object of the present invention to provide a flexible device which is at the same time compact and can be used for delivering a focused electron beam to an object while it is not consuming gas in large volume. Therefore, an object of the present invention is to provide a sources-saving device having the above-mentioned properties.

Summary of the invention

[008] In a first aspect of the present invention, a method for generating, accelerating and focusing an electron beam and delivering thereof to an object is provided.

[009] The method comprises the steps: — delivering a laser beam to a capillary of a gas cell, wherein the laser beam is interacting with the gas therein so that an electron beam is generated and accelerated via laser-plasma interaction inside the gas cell; — delivering the electron beam to a tuneable active plasma lens; — passing the electron beam through the tuneable active plasma lens, while controlling discharged current passing through the gas in the tuneable active plasma lens, thereby obtaining the focused electron beam; and — ejecting the focused electron beam from the tuneable active plasma lens in a forward direction of the object.

[010] In accordance with the above-mentioned object of the present invention, an injector of the gas cell must pump into the gas cell significantly smaller volume of the gas compared to a gas jet. According to inventors’ experiment, it is possible to fill the capillary volume using the limited amount of gas (typically with 2-3 litters of hydrogen gas per hour at pressure about 100 mbar). The laser pulse excites large-amplitude plasma wakefields of which an accelerating electric field can trap plasma electrons and accelerate them. The accelerated electrons are passing through a tuneable active plasma lens for focusing. The method thus provides generating, accelerating and Page 3 from 22 subsequent focusing of the electron beam by a tuneable active plasma lens which LU102279 focuses the electron beam in both transverse planes at the same time. The focusing properties of the active plasma lens is controlled by the discharge current to optimize the focusing strength of the active plasma lens for a wide energy range without changing the position of the lens — therefrom “tuneable”. Furthermore, the method, resp. device, allows to minimize a total length of the electron beam transport system using only one active lens instead of a set of permanent quadrupole magnets in addition to improving the focusing features of such beam transport system suitable for different energies of the beams. The method, resp. a device for carrying the method and irradiation system suitable for radiation therapy can be light weight, low cost, and absence of utilities required in the electro-quadrupole magnet beamlines, enabling compactness of non-planar facility arrangements, where accelerator can be placed at the basement level, reducing the total facility footprint and the need for shielding. The active plasma lens provides high magnetic field gradient by use of adjustable applied electric field. The required focusing of the electron beam can be performed in both transverse planes by using only one active plasma length, which is impossible in the case of traditional electro- or permanent quadrupole magnets. The gas cell saves the gas mixture pumped into a capillary to produce an electron beam via laser-plasma interaction.

[011] In a preferred embodiment, the ejecting of the focused electron beam is ejecting from a rotatable optical gantry.

[012] In another preferred embodiment, the laser beam ejected from the gas cell is directing to a beam dump.

[013] In a more preferred embodiment, the laser beam ejected from the gas cell is directing to a mirror and subsequently is directing to the beam dump.

[014] In another embodiment, the electron beam ejected from the gas cell is passing through a collimator before entering the tuneable active plasma lens.

[015] More preferably, the laser beam is propagating through artificial atmosphere in the capillary of the gas cell, wherein the artificial atmosphere consists of pure hydrogen (Hz) or a mixture of 98% Hz and 2% Ne in order to utilize the ionization-injection laser wakefield acceleration mechanism.

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[016] More preferably, the electron beam is propagating through a capillary of the tuneable LU102279 active plasma lens, wherein the capillary comprising hydrogen.

[017] In a preferred embodiment, in order to minimize the required laser power acceleration, the electron beam is provided in a preformed plasma channel, which allows effective external guiding of the laser pulse in the plasma medium with a length needed to get the electron beam with a required energy. Such approach will allow usage of a high- repetition rate laser system with a moderate laser power, which are more stable and reproducible than high-power laser systems.

[018] One of the laser wakefield acceleration limitation is connected with the laser diffraction effect, which can be solved by using preformed plasma channel. It was demonstrated experimentally [K.Nakamura et al., Phys of Plasma 14, 056708 (2007)] that the use of a discharge-based waveguide permitted operation at an order of magnitude lower density and about 10 times longer distance than in other experiments, relied on laser preformed plasma channels. To accelerate electrons up to a few hundred MeV the laser pulse with pear power ranging 10-20 TW (laser pulse duration of ~ 30 fs, laser peak energy of ~ 500 mJ) is required instead of 100TW-class lasers. It opens the way to use high-repetition rate (up to 50 Hz) laser systems.

[019] In a second aspect of the present invention, a method for an object irradiation by an electron beam is disclosed.

[020] The method for an object irradiation comprising: — generating a laser beam capable of laser driven acceleration; — delivering the laser beam via an optical gantry to a capillary; and — the method for generating and focusing according to anyone of the preceding embodiments.

[021] In some embodiments, the object of irradiation can be a water phantom or a patient under treatment plan.

[022] In a third aspect of the present invention, a device for focusing an electron beam and delivering thereof to an object is provided.

[023] The device comprising: Page 5 from 22

— a gas cell, which can be both provided with or without discharge, configured to receive LU102279 a laser beam, wherein the laser wakefield acceleration of electrons is performed; = preferably, the laser beam is capable to generate an electron beam when the laser beam passed through a capillary without discharge (gas cell) or with discharge (external laser guiding); - a tuneable active plasma lens configured to receive the electron beam ejected from the gas cell with or without discharge, wherein the focusing of the accelerated electrons will be performed; wherein — the tuneable active plasma lens is provided with the means for controlling electric current passing through gas.

[024] The device provides the same technical advantages as mentioned above. The device, due to using the gas cell instead of a gas jet used as the laser driven accelerator, requires significantly less powerful pumping system to obtain a required underpressurized artificial atmosphere. This can be achieved by only one turbopump, which can be used effectively.

[025] In a preferred embodiment, the device further comprise a laser beam dump configured to receive a laser beam coming from the gas cell. The beam dump helps to prevent damages on device caused by the laser beam by absorbing the energy of the laser beam therein.

[026] In another preferred embodiment, at least two-stages gas cell is used as a laser driven accelerator.

[027] In a preferred embodiment, the device further comprises a means for re-directing the laser beam from the optical axis of the electron beam to the beam dump, wherein the means for re-directing is positioned between the gas cell and the tuneable active plasma lens.

[028] In another embodiment, the device further comprises a gas control system. The gas control system comprises an artificial atmosphere, wherein the gas control system is connected to the gas cell for supplying artificial atmosphere in the capillary of the gas cell.

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[029] In another embodiment, the gas control system comprises a gas mixture consisting of LU102279 98% H> and 2% No.

[030] In another embodiment, the device further comprises a second gas control system comprising gas for capillary in the tuneable active plasma lens, wherein the gas preferably comprising hydrogen.

[031] In a fourth aspect of the present invention, an irradiation system suitable for radiation therapy comprising — adevice according to anyone of the preceding embodiments, — a laser system generating a laser beam; and — a rotatable optical gantry for propagating the laser beam from the laser system to the device.

[032] In addition to the above-mentioned advantages, the irradiation system, compared to the “state-of-the-art” radiation therapy system and its method of beam transport using electromagnet or permanent magnet, is further reducing size and weight of the radiation system significantly preserving the flexibility.

Brief description of the drawings

[033] Fig. 1 represents a schematic layout of the device according to the present invention with the laser-plasma interaction area to accelerate electrons in a gas-cell and an active plasma lens to focus accelerated electrons.

[034] Fig. 2 represents a second embodiment of the device for creating and focusing an electron beam provided with different beam dump position.

[035] Fig. 3 represents a detailed schematic layout of the laser-plasma interaction area to accelerate electrons in a gas-jet or a capillary (with continuous gas-flow or with preformed plasma channel) and the active plasma lens to focus accelerated electrons.

[036] Fig. 4 represents an embodiment of robotic system using an optical gantry for delivering a focused electron beam to an object.

Detailed description Page 7 from 22

[037] Capturing and guiding of electron beam 3 suitable for radiotherapy, especially LU102279 generated by a laser driven accelerator, is very challenging because of the large divergence of the electron beams 3 at the plasma exit. A tuneable active plasma lens 4, as the main element of such electron beam 3 transport system, allows to capture and focus the electron beam 3 from the laser plasma accelerator source such as gas jet 2 by using the azimuthal magnetic field, created by the current passing along the plasma channel. Fig. 1 schematically represents an embodiment of the present invention, in particular a laser beam 1, which is incident to a capillary 21 of a gas cell

2. The gas cell 2 comprises the above-mentioned capillary 21 in which an artificial atmosphere is provided. The artificial atmosphere can be chosen in accordance with the state of the art teaching. The capillary 21 is connected to a gas control system 22 via channels 23 supplying the gas into the capillary 21, thus supplying the artificial atmosphere according to the requirements for generating and accelerating of electron beam 3 by the laser-plasma accelerator. The gas control system 22 controls gas mixture and pressure in the capillary 21 of the gas cell 2. In an embodiment, the gas cell 2 confines the mixture of 98% hydrogen and 2% of nitrogen, wherein the mixture is introducing into the capillary 21 of the gas cell 2 through the channels 23 and under control by the control system 22. The gas cell 2 comprises a 20 mm diameter cylinder with a 3 mm diameter gas inlet located on the side, close to the cell entrance, which can represent a preferred embodiment of the capillary 21 of the gas cell 2. Such as gas cell 2 can provide an electron beam 3 having energy around 4 GeV provided 200 TW femtosecond pulse laser is used. For the purpose of radiation therapy application, the required electron beam energy can be limited by 200 MeV. In another embodiment, the capillary 21 of the gas cell 2 can have diameter in range 0,1 — 0,25 nm and length in the range 6 — 10 mm. In order to achieve electron beam 3 having energy about 200 MeV, compact high repetition rate laser system (~ 1 J with the pulse duration of ~ 30 fs) can be used. In some embodiment, a femtosecond pulse laser having a peak power -10'8 W/cm? is sufficient. When the pulsed laser beam 1 interacts with the gas inside the capillary 21 of the gas cell 2, a plasma is formed, and the ponderomotive force of the laser beam 1 pulse generates a large amplitude plasma wave. This wave can break, trap, and accelerate electrons and forms an electron beam 3, however, the electron beam is highly defocused. Therefore, a focusing means of the electron beam 3, a tuneable active plasma lens 4, is used. Only one tuneable active plasma lens 4, placed close to the gas cell 2, focuses the electron beam 3 in both transverse phase-planes.

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The length of the tuneable active lens 4 is a few centimetres, such as 3 cm in length, LU102279 which is much smaller than a typical length of a traditional electromagnetic quadrupole magnet. In addition to the compactness of the tuneable active plasma lens 4, the focusing strength thereof is controllable by adjusting the pulse current, passing through the plasma — therefore the focusing is tuneable and adaptable in accordance with energy of the electron beam 3. This feature allows to use the same tuneable active plasma lens 4 for wide range of the electron beam 3 without changing of the position thereof in the electron beam 3 transport, which is not possible in the case of a permanent quadrupole magnet. The tuneable high-field gradients of up to 1000 T/m can be obtained. In order to focus electron beam 3 with energy of ~ 200 MeV, one can use such tuneable active plasma lens 4 with the length of ~ 3 cm to collect the diverged electron beam 3 at the distance of ~ 50 cm behind the gas cell 2. Integration of the tuneable active plasma lens 3 into the compact electron beam 3 transport allows to build a compact and tuneable setup, which is not possible by utilizing a traditional electromagnetic or permanent quadrupole magnets. Using the active plasma lens 4 as the key element in combination gas jet 2 allows developing ‘all-optical’ laser-based setup for a robotic radiotherapy system which can be used while saving gas and requires less powerful pumping system.

[038] In the embodiment shown in Fig. 1, the active plasma lens 4 comprises a discharge capillary 41, which is a gas-filled elongated volume of square or circular cross section inside a glass or sapphire block. In principle, similar discharge capillary 41 can be used as the laser plasma acceleration element in the gas cell 2. As the result, the whole system can be constructed by placing two discharge capillaries 21 and 41 with a minimum distance between them. The laser beam 1 should be focused at the entrance of the first capillary 21 to produce accelerate electrons 3, which will be collected and focused at a required distance by the second capillary used as the active plasma lens 4 capillary 41. The plasma channel, created by the electrical discharge in the second capillary 41, will not be significantly affected by the laser light, because the laser pulse 3 is diverging significantly. Just a small portion of the laser beam power can pass through the active plasma lens 4 which do not affect the plasma itself. Fig. 1 further discloses a beam dump 24 for the laser beam 1 coming from the gas cell 2. The beam dump 24 is an optional feature of the device which prevents a laser beam 1 damage of the tuneable active plasma lens 4. The beam dump 24 cam be mounted on the entrance Page 9 from 22 of the tuneable active plasma lens 4 as schematically shown in Fig. 1 or can be LU102279 provided as a separated body as shown in Fig. 2.

[039] Fig. 2 schematically discloses an embodiment, where an electron beam 3 coming from the gas cell 2 is propagating together with a laser beam 1. The laser beam 1 is reflected to the beam dump 24 in different optical path compared to the electron beam 3. The electron beam 3 is further propagating to the tuneable active plasma lens 4.

[040] Both embodiments shown in Fig. 1 and Fig. 2 further shows a gas control system 42 connected to the capillary 41 of the tuneable active plasma lens 4. The gas is preferably hydrogen which is supplied to the capillary 41 via channels 43. The tuneable active plasma lens can focus the electron beam 3 in accordance with the applied discharge current. The applied discharged current is controlled via system 44, which only schematically shows a simple RC circuit, but it can be significantly more sophisticated.

[041] The magnetic field gradient near the centre of the active plasma lens can be estimated using the following relation between the peak current /o and the radius of the capillary Rc, where jo is the vacuum permeability

[042] (@B/0r), = Hoge

[043] In the case of the peak current of 300 A and the capillary radius of 250 um, the magnetic field gradient at the centre of the capillary is 960 T/m. The magnetic field gradient is proportional to the current, passing through the plasma channel.

[044] Fig. 3 represents a detailed scheme of focusing mechanism of the tuneable active plasma lens 4 implemented into the device according to the present invention. Fig. 3 represent the tuneable active plasma lens 4 focusing properties, controlled by the discharge current. The focusing strength of the lens has axial symmetry with the zero on the axis. Force 472 is the focusing force acting on an individual electron of the beam, passing along the plasma lens 4. The active plasma lens 4, which is can be a Sapphire capillary 42 with a controllable current 45 passing through the plasma, created by utilizing a discharge electrical circuit 44, placed near the capillary 21 of the gas cell 2. The passing current 45 creates a magnetic field 46 which force the electron beam 3 focus via force 472. As the result, near the centre of the system capillary 41 the magnetic field gradient will be created, depending on the current and the capillary Page 10 from 22 radius. The electron beam 3 from the laser-plasma gas cell 2 with the required energy LU102279 propagates through the tuneable active plasma lens 4, located near the source without significant degradation in a short drift space between. The capillary 42 with a small transverse size, typically less than 0.5 mm, is filled by the hydrogen gas, generated in a compact commercial hydrogen generator with controllable gas pressure. In a preferred embodiment, the focusing strength of the active plasma lens can be adjusted to provide required focusing of the electron beam 5 at the target 6 for the fixed electron beam 5 energy. It will allow to deliver a required size of the electron beam 5 from the irradiation system. “All-optical” setup for radiation therapy

[045] A compact rotatable radiation therapy system is schematically shown in Fig. 4. The system comprises an optical laser beam transport LCH1, LCH2, LCH3, a laser system 11 generating a laser beam 1 capable to produce an electron beam 3 in a gas cell 2 and an active plasma lens 4 placed in a vacuum chamber ACH. A main constrain for the setup is a distance from the exit of the vacuum chamber ACH to the rotation axis of the system, which is preferably less than 1 m to have enough space for diagnostic elements and treatment (targeted) object 6. The rotatable “all-optical” setup suitable for radiation therapy contains only the optical elements to transport the laser beam 1 from the laser system 11 through a vacuum pipe and set of flat mirrors 13 and a spherical mirror 15 for focusing the pulse laser beam 1 into the laser plasma acceleration gas cell 2. The active plasma lens 4 is located after the laser plasma acceleration gas cell 2 and protected from the diverged laser beam 1, e.g. by a beam dump 24, coming from the acceleration gas cell 2 after the laser-plasma interaction. The differential pumping is preferably used between the beam transport LCH3 and vacuum chamber ACH to keep a high vacuum in the beam transport LCH3. Each beam transport LCH1 — LCH3 comprises a vacuum chamber 12 with a mirror 13 capable to change the direction of the laser beam 1 path. Part of the beam transport LCH3 comprises a mirror 14 having an aperture for passing a focused laser beam by the spherical mirror 15. Such scheme has been experimentally tested and approved for a long-term operation, performed for example for 24 hours continuous operation with the repetition rate of 1 Hz. The vacuum system, the gas distribution and electrical setups are preferably connected to vacuum chamber ACH. Other chambers can be equipped by vacuum pumps and motorization system to control the position of the optics elements of the laser beam transport. The Page 11 from 22 laser diagnostics as well as electron beam diagnostics can be incorporated into the LU102279 rotatable system.

[046] To provide a high intensity laser beam 1 at the entrance of the accelerator gas cell 4, the high-energy pulse laser beam 1 is preferably focused to a spot with FWHM size of ~ 20-30 um. The accelerator gas cell 2 is synchronized with the pulse laser beam 1 and/or with a continuous gas flow in a capillary 21 and/or 41 and/or a preformed plasma channel 23 and/or 43, created in the capillary 21 and/or 41 filled by the hydrogen gas, resp. gas mixture. The electron beam 3 self-injection mechanism allows to trap the plasma electrons into the acceleration wave, which moves behind of the laser pulse. The acceleration length is determined by the dephasing or depletion length in the case of the guiding regime. Latest experimental achievements indicate that the stable electron beam with the energy around 200 MeV with the bunch current ~ 100 pC can be produced using the laser pulse power at the focus ~ 40 TW. The tunable active plasma lens 4, which can be a single sapphire capillary with the length of 1-2 cm placed behind the ‘accelerator’ gas cell 2, allows to focus the accelerated electron beams 3 and transport the focused electron beam 5 to the target 6 without significant losses. The focusing strength of tunable active plasma lens 4 can be controlled by changing the discharge current. The plasma lens can be preferably synchronized with the laser pulse 1, used for the laser-plasma acceleration. In the case of significant degradation of the electron beam 5 parameters, caused by the chromatic and collective effects, a further collimation system placed after the active plasma lens 4 can be utilized with the motorized control of the gap size in both horizontal and vertical planes. By optimizing the LWFA process in the ‘accelerator’ gas cell 2, the chromatic effects caused by large transverse divergence and large energy spread of the electron beam can be minimized. In this case the spot size of the electron beam 5 can be controlled by the tunable active plasma lens 5 only.

[047] The advantage of the gas-cell in comparison with the gas-jet is connected with the amount of gas, required for these two setups. In the case of the gas-cell the total volume (limited by the channel volume in the capillary) is extremely small and as the result the compact hydrogen generator can be used to fill this volume. Nobody makes the electrical discharge in the gas-jet.

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Claims (15)

1. Claims LU102279 Claim 1 A method for generating and focusing an electron beam (3) and delivering thereof to an object (6), wherein the method comprises the steps of: = delivering a laser beam (1) to a capillary (21) of a gas cell (2), wherein the laser beam (1) is generating and accelerating an electron beam (3) via laser- plasma interaction inside the gas cell (2); — delivering the electron beam (3) to a tuneable active plasma lens (4); — passing the electron beam (3) through the tuneable active plasma lens (4), while controlling discharged current passing through the gas in the tuneable active plasma lens (4), thereby obtaining the focused electron beam (5); and = ejecting the focused electron beam (5) from the tuneable active plasma lens (4) in a forward direction to the object (6).

   Claim 2 The method according to claim 1, wherein the ejecting of the focused electron beam (5) is ejecting from a rotatable optical gantry.

   Claim 3 The method according to anyone of the preceding claim, wherein the laser beam (1) ejected from the gas cell (2) is directing to a beam dump (24).

   Claim 4 The method according to claim 3, wherein the laser beam (1) ejected from the gas cell (2) is directing to a mirror and subsequently is directing to the beam dump (24).

   Claim5 The method according to anyone of the preceding claim, wherein the electron beam (3) ejected from the gas cell (2) is passing through a collimator before entering the tuneable active plasma lens (4).

   Claim 6 The method according to anyone of the preceding claim, wherein the laser beam (1) is propagating through artificial atmosphere in the capillary (21) of the gas cell (4), wherein the artificial atmosphere consist of 98% Hz and 2% Ne.

   Claim 7 The method according to anyone of the preceding claim, wherein the electron beam (3) is propagating through a capillary (41) of the tuneable active plasma lens (4), wherein the capillary (4) comprising hydrogen.

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   Claim 8 A method for an object irradiation by an electron beam (3) comprising: LU102279 — generating a laser beam capable of laser driven acceleration; — delivering the laser beam via an optical gantry to a capillary (21); and — the method for generating and focusing according to anyone of the preceding claims.

   Claim 9 A device for focusing an electron beam (3) and delivering thereof to an object (6) comprising: — a gas cell (2) configured to receive a laser beam (1), wherein the gas cell (3) is capable to provide an electron beam (3) by laser wakefield acceleration; — atunable active plasma lens (4) configured to receive the electron beam (3) ejected from the gas cell (2), wherein — the tunable active plasma lens (4) is provided with the means (44) for controlling electric current passing through gas.

   Claim 10 The device according to claim 9 further comprising a laser beam dump (24) configured to receive a laser beam (1) coming from the gas cell (3).

   Claim 11 The device according to claim 10 further comprising a means (31) for re-directing the laser beam (1) from the optical axis of the electron beam (3) to the beam dump (24), wherein the means (7) for re-directing is positioned between the gas cell (2) and the tuneable active plasma lens (4).

   Claim 12 The device according to anyone of the claim 9 — 11 further comprising a gas control system (22) comprising an artificial atmosphere, wherein the gas control system (22) is connected to the gas cell (2) for supplying artificial atmosphere in the capillary (21) of the gas cell (2).

   Claim 13 The device according to claim 12, wherein the gas control system (22) comprising a gas mixture consisting of 98% Hz and 2% No.

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   Claim 14 The device according to anyone of the claim 9 — 13 further comprising a second gas LU102279 control system (42) comprising gas for capillary (41) in the tuneable active plasma lens (4), wherein the gas preferably comprising hydrogen.

   Claim 15 An irradiation system comprising — adevice according to anyone of the claims 9 - 14, — a laser system generating a laser beam (1); and — arotatable optical gantry for propagating the laser beam (1) from the laser system to the device.

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