Laser driven ion accelerator

A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

FIELD OF THE INVENTION

This invention relates to method and apparatus for accelerating particles and, more particularly, to a method and apparatus of accelerating particles to achieve optimal energies.

BACKGROUND OF THE INVENTION

Conventional radiation therapy utilizes electron beams and x-rays as a means of treating and controlling cancer. Due to the inability of current technology to preferentially deposit the radiation at the site of the cancer, healthy tissues between the tissue surface and the cancer also receive high doses or radiation and, therefore, are damaged. Consequently, physicians use a less-than-optimal dose to reduce the undesirable damage to healthy tissues and the subsequent side effects. In many cases, this proves to be an unacceptable alternative.

SUMMARY OF THE INVENTION

Aspects of the present invention include an accelerator system having a light source; and a target having a concave shape.

Aspects of the present invention further include a method including firing a laser pulse having an energy range of approximately 1 to approximately 10 Joules from a light source at a target; guiding radiation elements emitted from said laser pulse striking said target; discriminating ions having a predetermined energy range from said radiation elements; and delivering said ions in an energy range of approximately 10 to approximately 500 Mega-Electron Volt (MeV) to a treatment field.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are described accelerator systems and methods which may deliver protons and other ions to higher energies in an efficient manner. The accelerator systems and methods described herein may be in a compact or portable form to increase the flexibility of its use. Exemplary applications of the disclosed accelerator systems and methods may include radiation oncology; ion radiology; ion isotope sources; pion, muon, and neutrino beams sources; and spectroscopic diagnosis (nondestructive or otherwise) of different types of materials. For illustrative purposes, the exemplary embodiments disclosed herein may be used in radiation oncology applications.

FIGS. 1A-1Eillustrate a schematic view of an embodiment of an accelerating system100. The accelerating system includes the following components: a light source system (e.g., laser system)101producing an energy pulse102which travels through a light source guide system101bto a target system110located in a vacuum chamber108. The pulse102strikes the target200in the target system110and an ion beam102ais produced which travels through an ion beam transport system and irradiation system120to a treatment field150. The operation of the accelerating system100is controlled by a controller160and feedback system170. These components may combine to form a compact (e.g., portable, tabletop) accelerating system. The length, L1, of the light source system101and light source guide system101bmay be in the range of approximately 1 to approximately 2 meters. The length, L2, of the target system110and a first section120aof the ion beam transport and irradiation system120may be in the range of approximately 1 to approximately 2 meters. Therefore, the overall length of the light source system101, light source guide system101b, the target system110and a first section120aof the ion beam transport and irradiation system120, L3, may be in the range of approximately 2 to approximately 4 meters. The length, L4, of separation of the vacuum chamber108and the treatment field (or object)150may vary depending on the specific application. For example, L4may range from approximately 0.25 to approximately 10 meters. It is to be understood that these exemplary lengths may vary higher or lower, again, depending on the specific application.

The accelerating system100is controlled by a controller160whose functions will be described in detail below. In order to maximize a flux of ions produced in the accelerator system100, a chirped-pulse amplification (CPA) based, compact, high-repetition, high fluence laser system (e.g., a Ti: sapphire laser) may be utilized as a light source system101. The basic configuration of such a light source system101is described in U.S. Pat. No. 5,235,606, issued Aug. 10, 1993 to Mourou et al., which is hereby incorporated by reference. The light source system101having a pulse shaper101aemits an energy pulse (or pulses)102having a pulse energy of approximately 1 to approximately 10 Joules (J). The pulses102may be delivered at a rate of approximately 0.1 to approximately 100 Hertz (Hz). The pulses102are transported by a light source guide system101bwhich may include a series of mirrors104and thin foils105. Mirrors104are configured to guide and focus the pulse102with a predetermined intensity using the last mirror in the mirror series104. Before the pulse102enters the target system110, the light source guide system101bmay include a series of thin foils (e.g., metal)105that are capable of controlling or reducing the prepulse of each pulse102. The prepulse section of each pulse102may comprise a field of the pulse102prior to the arrival of the main peak of the pulse102. Because a pulse102may be very short and intense, even a fraction of the peak intensity of the pulse102(e.g., the prepulse) may be sufficient to ionize and/or ablate the foils105. The prepulse may be controlled by using multiple foils105and a pulse shaper101ain the light source system101. The pulse shaper101amay optionally include a frequency multiplier.

Controller160and feedback system170are configured to perform monitoring, controlling and feedback functions for the accelerator system100. Controller160may be a microprocessor or other conventional circuitry. A plurality of sensors103monitor the intensity of the pulse102and ion beam102athroughout the accelerator system100. As illustrated byFIGS. 1B and 1C, monitoring points where sensors103are positioned may include the light source system101output, mirror series104output, the target entry point of the pulse102, after the target200, before slit122, before magnets123, after filters126, and before and after the treatment field150. In alternative embodiments, it is to be understood that sensors103may not be limited to these numbers or positions. The monitoring information is forwarded through the feedback system170to the controller160. Based on this input, controller160is configured to fine-tune the light source system101and may provide control signals to light source101, mirror series104, foils105, magnets123,125,129and filters126to adaptively control the quality of pulse102and ion beam102a. Parameters of the pulse102and ion beam102awhich may be adaptively controlled by the controller160and the feedback system170may include repetition rate, laser flux, focus, aperture, angle, intensity, and pulse length.

The pulses102may be guided by the a light source guide system101binto vacuum chamber108which encloses target system110. The target system110may be composed of prefoils, target feed, slits and shields represented by reference numeral107and a target200. (Target200may also be referred to herein as a foil, a film, a source and accelerator element, or an interaction element). Pulses102may be intense, ultrafast (i.e., having a pulse length between approximately 1 to 500 femtoseconds (fs)) and ultra-relativistic. During operation, the pulses102immediately (within a few fs of the pulse entry to the target200) and substantially destroy the target200and ionize multiple electrons per each of the atoms contained in the target200to form “hot” electrons. Hot electrons may be defined as electrons having energy greater than approximately 1 MeV. Together with conduction band electrons, these hot electrons form a high density electron cloud201bin region201that is driven forward by the acceleration and heating of these electrons to high energies by the light source system101. An electrostatic field is set up through charge separation by these hot electrons. Therefore, according to a simple one-dimensional model, an accelerating gradient E0is wavelength, λ, proportional to the energy (or temperature) of hot electrons divided by the width of the charge separation, which is approximately the Debye length λDof hot electrons:
E0=αTh/λD,
where α is a constant (about 5 to 10) and This the energy of hot electrons. The energy gain of ions may be the following:
EI=ql E0,
where q is the ion charge and l is the acceleration distance. Therefore,
EI=αq(l/λD)Th.
When l is approximately λD, which is the case for a simple one-dimensional geometry, an energy gain of ions is obtained as
EI≅ql E0.
Based on these equations, the acceleration system100is designed to enhance EIby increasing α, l/λD, and Th(and except for protons, q also).

For example, when the geometry of the target200has a substantially concave geometry as shown inFIG. 2, both α and l may be increased. If electrons are heated or accelerated to higher energy, Th(or even Th/λD) increases. This is because λDis proportional only Th1/2. The changing target parameters (which are discussed in detail below) may increase α, l , or Th, or all of these.

During operation, the energy of the light source system101may be compressed into an ultrashort time scale of approximately 10 to 100 fs after a CPA's time stretcher and compressor (not shown), but before the final focal mirror in the mirror series104. The final focal mirror in the mirror series104may focus the pulse102which has been time-compressed into a spatially compressed light spot (H inFIG. 2) on the target200in the target system110. The distance, d1(as shown in FIG.1A), from the final focal mirror in the mirror series104to the target200may be substantially less than 1 meter (m). The light source system101is capable of delivering to the target200a light beam intensity in the range of approximately 1018to 1023Watts (W)/centimeter (cm)2, with approximately 1021W/cm2being the typical intensity. The target system110is designed to allow the optical interaction of the intense short pulse102with the target200to yield a high flux of energetic ions such as protons201a(as shown in FIG.1B). As discussed above, the target200may be substantially destroyed when struck by the pulse102, forming a plasma201bcontaining electrons and ions (e.g., protons201a) in region201. The plasma electrons may then be driven towards the first section120aof the ion beam transport and irradiation system120and the plasma electrons may pull ions with them towards the first section120a. The distance from the target200to the treatment field150, d2, may also be less than approximately 1 m. Therefore, the combination of distances d1and d2may be less than approximately 1 m. The target200may be a film or foil that is rolled into position on rollers109under control of controller160for each shot of the light source system101. The target200may include a target portion and a prepulse controller portion which controls the prepulse of the pulse102or reduces it. Both target portion and prepulse controller portion may be moved synchronously with the pulse shots from light source101to expose a fresh film surface. The target200will be discussed in further detail below.

The first section120aof the ion beam transport and irradiation system120is located inside vacuum chamber108. The second section120bof the ion beam transport and irradiation system120is located between the vacuum chamber108and the treatment field150. The first and second sections120a,120bof the ion beam transport and irradiation system120may include slit122, magnet or magnets123, beam dump130, shields124, magnet or magnets125, filter or filters126, aperture or apertures127, foil or foils128, magnet or magnets129, optional electronic guide131and sensors103. The first and second sections120a,120bmay include other transportation and control elements not shown inFIGS. 1A-1C. Second section120bmay optionally include a support of the treatment field150for irradiation of a patient (support is not shown) in oncological applications.

The ion beam transport and irradiation system120is configured to discriminate among various radiation components produced by the pulse102striking the target200. The ion beam transport and irradiation system120is designed to achieve this discrimination by isolating predetermined energy ions which are to be used in irradiating the treatment field150and separating (i.e., dumping) the radiation components which are not to be used in the irradiation on the treatment field150. The radiation components which result from the pulse102striking the target200include different species of ions (e.g., protons), x-rays, electrons, remnants of the pulse102, and different energy components (e.g., MeV,10's MeV, and100's MeV within a certain energy band or window). After ion generation from the target200, ions such as protons201awith a predetermined emittance are allowed to pass through the slit122in the form of an ion beam102a. Beyond the slit122, magnets (or magnet)123are designed to discriminate the energy of the predetermined protons (and other types of radiation) by bending the different species and components of radiation and directing the remaining portion of the ion beam102ainto beam dump130. The magnets123may be pulsed as well as electronically modulated for control as well as for scanning. Combined with the magnets123are shields124and filter or filters126which may also be used not only to protect undesired radiation from hitting the treatment field150for irradiation, but also to define and discriminate a predetermined portion of the phase space of the given radiation component to be delivered to the treatment field150. A beam aperture127may be used to control the size of the beam102ato irradiate the treatment field150. A plurality of high Z metallic foils128may be configured inward to stop low energy or low ranged components of radiation and monitor the ion beam102a. Magnet(s)129may control the direction of the ion beam102a. An optional electronic guide131may be placed after the magnet(s)129to perform a scanning function of the ion beam102aon the treatment field150.

The width, angle and emittance of the ion beam102awhich strikes the treatment field150is controlled by a combination of accelerator system100design choices. These design choices may include the nature of the target200(which will be discussed in detail below), the light source system101intensity and focus, the distance of the light source system101from the target200, the choice of transport elements (e.g., magnets, filters, foils, shields, mirrors, and slits), the width of the beam aperture127, and the use of an optional electronic guide131. The size of the light source (e.g., laser) spot150aon the treatment field150may vary from about 0.5 to about 20 cm2in area in accordance with accelerator system100. For example, a pointed, small emittance beam (i.e., a pencil beam producing a light source spot150aof approximately 0.5 to approximately 2 cm2) on the order of approximately 1 millimeter milliradians (mm mrad) may be produced by the accelerator system100. Such a small pencil beam may be configured to scan through the electronic guide131and cover a portion of or the whole region of the treatment field150by scanning in a predetermined pattern where irradiation is desired. Therefore, in oncological applications, a small tumor (i.e., in the range of approximately 5 to 20 cm) may be more accurately targeted for localized or conformal treatment.

The optical elements (e.g., mirror series104), target200, the magnets123,125, and129and other transport elements may be controlled adaptively through the controller160and feedback system170during and after each shot from light source system101. Through the use of the controller160and feedback system170, the control and modulation of the beam energy, energy band, size, and repetition rate may be achieved—shot by shot—of the light source system101. The ion beam transport and irradiation system120may also be configured to discriminate a portion or portions of the ion beam102ain angle and size to adjust the beam's size, emittance, and flux for predetermined ion beams102awhich allows for a highly flexible system.

At least four parameters of the target200may be varied to obtain a change in performance of the ion beam102awhich strikes the treatment field150. These four parameters may include the width, material, geometry (or shape) and surface of the target200. The modification of these parameters allows for the maximization of the interaction of the pulse102and the target200and the maximization of the energy and flux of the ion beam102awhich results from the pulse102striking the target200. A detailed discussion of the four parameters follows.

The pulse102which strikes the target200has a field (e.g., laser field) with an intensity in the ultra-relativistic region. In the ultra-relativistic region, the electron momentum in the field exceeds mc, where m is the electron rest mass and c the speed of light, so that the electron energy in the field far exceeds that of electron rest mass (e.g., at least approximately 1021W/cm2). The pulse102may be irradiated over a small spot200a(as shown inFIG. 2) (e.g., approximately 2 to approximately 10 square microns) on the target200. The target200acts as an ion source as well as an accelerator, emitting energetic ions (e.g., protons201aas shown inFIGS. 1A-1B) in the plasma region201behind the target200. As discussed above, the plasma region201is followed in sequence by the ion beam transport and irradiation system120which may extract a predetermined band of protons201afrom the plasma region201. The beam102awhich emerges from the ion beam transport and irradiation system120will be an ion (e.g., proton) beam and is capable of irradiating the treatment field150of a patient.

FIG. 2illustrates an enlarged side view of the target200. The first parameter of the target200that may be varied is the material of the target200. The target200may be a multilayer material having a first layer202and a second layer204. These layers202,204may be two different materials or bi-material (e.g., bi-metal). The layers202and204may be adhered together. The first layer202of the target200is designed to reflect the low-intensity prepulse of the pulse102and become transparent at higher intensities of the pulse102very quickly after being struck. The first layer202may be a metal or semiconducting film material. The first layer202may be made of a higher Z material than the second layer204. For example, first layer202may be aluminum, carbon, gold, or lead. A high Z material may contain high atomic number atoms that generate a large number of electrons, but ions in this setting do not gain much energy, while most of the pulse energy is absorbed here. The first layer202is capable of converting the photon momentum of the pulse102which strikes the target200into electron momentum. The first layer202may also compress the pulse102further by a small factor so that the intensity of the pulse increases at the moment of its impingement on the surface of the target200by the electromagnetic (EM) ponderomotive drive of electrons into the interior of the first layer202. The second layer204, on the side of the target200opposite to the entry of the pulse102, may be made of proton rich lower Z materials (e.g., hydrogen, hydrogen rich materials, plastics made of carbon, and water) than the first layer202material. Low Z materials contain low atomic number atoms that do not generate as many electrons, but generate light ions (e.g., protons, carbon, oxygen ions) and cause a strong electrostatic field. This electrostatic field may convert electron energy into ion energy. The second layer204may produce protons through irradiation leading to ionizing the material in the second layer204instantaneously (i.e., a range of about 1 to about 5 femtoseconds). Therefore, the first and second layer configuration may enhance electron production in the high Z material of the first layer202and stabilize the hot electron production and subsequent ion production. Although a first and second layer are illustrated, it is to be understood that further layers may also be used.

The second parameter of the target200that may be varied is the thickness, t3, of the target200. The thickness t1of the first layer202is designed to be large enough to stop substantially all of the pulse102. However, it may not be designed to be so large as to capture hot electrons generated by the first layer202. The typical thickness t1of the first layer202is also dependent and inversely proportional to the Z value of the material and, therefore, the stopping power. The range of the thickness t1may be approximately 50 to approximately 2000 nanometers (nm). If the prepulse of the pulse102from the particular light source system101varies longer and larger so as to ablate the first layer202, the thickness t1may be increased accordingly. The thickness t2of the second layer204may be smaller than the first layer202and in the range of approximately 10 to approximately 2000 nm, and, typically in the range of approximately 10 to approximately 100 nm. Therefore, the combined thickness of the first and second layers to form the thickness of the target, t3, may be in the range of approximately 60 to approximately 2500 nm.

The third parameter of the target200that may be controlled is the shape of the target200. The geometry (or geometries) of the target200may enhance the electron density and the ability to trap ions behind these electrons, thereby increasing both α and l. In order to enhance the accelerating electrostatic field that results from the pulse102striking the target200and the capacity to capture protons, the geometry of the target200may be substantially concave toward the acceleration direction as shown by reference numeral206in FIG.2. In addition, this concave configuration allows direct drive of electrons out of the target200into the hollow200cof the concavity206of the target200by an electric field caused by the light source (e.g., a laser field) as the angle θ between the target surface and the pulse incident direction allows greater energy and population of electrons driven out of the target200. Furthermore, the concave geometry introduces the ability to control the ion beam optics, such as the focusability, emittance and enhanced density of the ion beam102a. In alternative embodiments, a plurality of concavities may be used instead of a single concavity.

As discussed above, reference numeral H indicates the spot size of the pulse102as it reaches the target200. The first or light source side diameter J of the concavity facing the pulse102may be made substantially equal to the spot size H and the second or non-light source side diameter Y of the concavity206may be less than the spot size H. H, J and Y may each have a radius in the range of approximately 1 to approximately 10 microns. In alternative embodiments, H, J and Y may be designed to be substantially different in dimensions. For example, J may be substantially less than H or H may be substantially less than J. The concave shape of the target200may determine the focusability of ions (e.g., protons) depending on the curvature of the concavity206. Varying the aspect ratio of the concavity206, or the ratio of the diameter Y to the concavity measurement of concavity206(i.e., the slant of walls200dand200eoff axis A—A), may change the focal length of the target200. The smaller the aspect ratio, the shorter the ion focal length. The ion beam102aemittance may be determined by the spot size H on the target200times the angular divergence of the ion (e.g., proton). The angle, θ, of the concavity measurement of concavity206(i.e., the slant of walls200dand200eoff axis A—A), may be in the range of approximately 10 to approximately 90 degrees and, typically, may be approximately 40 to approximately 50 degrees. The angle, θ, of the concavity measurement of concavity206with respect to the first and second layers202,204(and the plane parallel to the phase front of the incident pulse102) may cause the transverse electric field of the pulse102to directly drive electrons into the first layer202and thereby enhance the energy of electrons coming off this first layer202to be higher. The nature of the concavity206may hold these electrons from dispersing to sustain a high density that sets up a high accelerating electrostatic field in the region201. The concave geometry of target200allows the charge of the electron cloud accelerated off the first layer202to see image charge not only behind the charge, but also beside it.

FIGS. 3A-3Eillustrate a series of alternative designs for the concavity206of target200.FIG. 3Aillustrates a concavity206with a dome shape having a base wider than a narrower curved shape at the distal end302.FIG. 3Billustrates a concavity206with a substantially pointed distal end304.FIG. 3Cillustrates a concavity206having an enhancement of the concave feature by increasing the angle of the concavity wall and, therefore, having a substantially circular shape306.FIG. 3Dillustrates a concavity206with a polygonal shape308with walls being extremely angled.FIG. 3Eillustrates a concavity206with a base being narrower than a substantially curved shape at the distal end310. These different concavity configurations allow electrons to propagate forward less impeded by the electrostatic force set up between the electrons and ions (which, otherwise, might turn the electrons back before the ions get accelerated), while ions are allowed to gain momentum to reduce the impedance mismatching between electrons and ions. The concave nature of the target200also allows the electrostatic fields and magnetic fields which are formed to pinch the electrons toward the axis (A—A inFIG. 2) of the concavity206, thereby increasing their density, which can induce axial electric current and the induced azimuthal magnetic fields further. These magnetic fields may further pinch the electron stream and increase the electron density and accelerating fields.

The fourth parameter that may be controlled of the target200is the design of the surface202b(as shown in FIG.2). The target material surface preparation may be designed so that pulse absorption is more efficient and resultant electron energy is greater. In order to enhance the absorption of the pulse102and the production of energetic electrons that drive the accelerating field of protons, the surface202bof the first layer202may be roughened. In another embodiment the surface202bof the first layer202may have at least one groove which has a depth and width of less than approximately 1 micrometer, and, typically in the range of approximately 10 to approximately 100 nm.FIG. 4Aillustrates a surface202bof the target200having a plurality of grooves402.FIG. 4Billustrates a surface202bhaving fibers (e.g., thin fibers)404.FIG. 4Cillustrates a surface202bhaving clusters406of approximately 10 to approximately 100 nm in diameter. Clusters from originally gaseous material may be made by spraying a gas jet into a vacuum. Another method of creating clusters may be found in U.S. Pat. No. 5,585,020, issued Dec. 17, 1996 to Becker et al. and hereby incorporated by reference. The packing ratio of the clusters may be defined as the ratio of the space occupied by clusters and that unoccupied by clusters. The packing ratio of the clusters may be high, specifically, up to about 1:1. A method of forming these clusters may include spraying or adsorbing them onto the second layer204of target200on the side facing the pulse102.FIG. 4Dillustrates a surface202bcomposed of foams408of approximately 10 to approximately 100 nm in diameter.FIG. 4Eillustrates a combination rounded concavity with grooves410. The surface preparations illustrated inFIGS. 4A-4Eare conducive of enhanced absorption of pulse102over a short distance which may be approximately less than 1 micron. For example, clusters406may be capable of absorbing nearly all (i.e., greater than approximately 70%) of the pulse energy when the pulse102has enough intensity. The size of grooves402, fibers404, clusters406or foams408may be designed to be shorter than the size of electron excursion in the pulse field (less than approximately 1 micron). For example, in the case of carbon such material may be soot. In alternative embodiments, hydrogen atoms may be adsorbed onto the back surface204a(the surface opposite to the direction of the laser pulse102as shown inFIG. 2) of the target200. In order to further control the prepulse of pulse102, several methods may be used. As discussed above, in front of the target, in reference numeral107(as illustrated byFIG. 1B) there may be placed an additional thin foil that is thick enough to absorb most of the prepulse energy of the pulse102but thin enough to be burned by the time the main peak of the pulse102arrives.

The material, thickness, geometry and surface design of the target200may be predetermined depending on the specific light source system101(e.g., laser system) used as well as the feedback system170in a shot-by-shot basis. In an alternative embodiment as illustrated byFIG. 5, a prepulse control foil CF may be placed at an angle with respect to the target200surface so as to cut off the prepulse of pulse102but to transmit the peak main pulse. Most of the prepulse will be reflected as shown by reflected pulse102b. In another embodiment, a plasma mirror (a mirror made up of a plasma that may be ionized by the light source itself or prefabricated) may be employed before the target200that transmits (or reflects) laser light according to its optical property as a function of intensity. In another embodiment, a frequency multiplier (i.e., double or triple) may be placed before the target200using a nonlinear crystal so that weaker prepulse components may be cut off (i.e., chopped). In another alternative embodiment, a genetic algorithm (or similar computer software) located in light source system101or controller160may be used to rearrange the spectrum of the broad band light source system101to sharpen the front side of the pulse102.

When a laser system is used for the light source101, the laser energy per laser shot from the laser system101is typically approximately 1 to approximately 10 J at the target200, while the obtainable ion energy from the accelerator system100may be approximately 10 to approximately 100 mJ at a predetermined energy of approximately 10 to approximately 500 MeV and typically a predetermined energy in the range of approximately 100 to approximately 200 MeV. For a radiation oncology application, a radiation dose of ions (e.g., protons) of approximately 1 to approximately 10 Gray (Gy) on a 1 centimeter (cm)2area over the 10 cm range of 100 MeV portons, may yield 10 cm3volume of irradiated tissue. (The range may also depend on factors such as the ion focus size). Therefore, the accelerator system100may be capable of producing an ion beam102awhich may penetrate approximately 10 to approximately 20 cm beneath the surface of skin tissue in the treatment field150of a patient to reach a tumor sight; produce a dose per shot at the treatment field150in the range of approximately 0.1 to approximately 10 Gy; and produce a dose per second at the treatment field of approximately 0.1 to approximately 100 Gy/second. If the light source system101repetition rate is approximately 10 Hz, a dose delivered to the treatment field150by the accelerator system100in less than approximately 1 second may be capable of treating a small tumor target on the order of approximately 1 square cm or less. If the tumor target is larger than approximately 1 square cm, a dose delivered by the accelerator system100may be capable of treating the tumor target in less than approximately 1 minute.

FIG. 6discloses an alternative accelerating system and method500. Housing501may be a needle or a syringe. Housing501may have a length, d6, of approximately 10 to approximately 40 cm and width, d5, of approximately 50 to approximately 300 microns. Contained within the housing501are a first section502connected to a second section504. The first section502may be a fiberglass or fiberoptic material and is connected to a light source system (e.g., a laser system)506which is capable of producing an energy pulse510(e.g., laser pulse). The first section502may vary in length depending on the application. Typically, the first section502may vary from about 0.1 to 10 meters. A protective surrounding such as housing501may be used so that any stray light may be reflected and/or absorbed in case the application of the light source system506is to human tissue. The first section502and second section504are used as a light source guide to a target508. Target508may be rolled into laser shot position (as shown inFIG. 6) through a delivery system such as rollers530. Typically, the target508may be placed in a predetermined position before each shot of the light source system506. The second section504may also be a hollow fiberglass (or fiberoptic) material. The second section504may be capable of conducting pulses510(e.g., short pulses) with intensity exceeding approximately 1016W/cm2over a distance of approximately 10 cm. The pulse510is propagated through the first section502and second section504to a spot in proximity to the target508. The length of the first section502is may vary depending on the specific application. Light source system506may be a chirped-pulse amplification (CPA) based compact high-repetition, high fluence laser system (e.g., a Ti: sapphire laser). The light source system506may be inversely chirped so that as the pulse510propagates through the first section502and the second section504the pulse510may contact itself in time domain to yield maximally allowed intensity (e.g., approximately 1017W/cm2). Specifically, the pulse510(which was originally time stretched) may, in the first half of the CPA technique, be compressed by a compressor (not shown) only to the extent that the pulse510does not exceed a threshold intensity (approximately 1016W/cm2or less), which may be further compressed through the second section504. The second section504may be constructed such that its fiber radius, length, and index of refraction may be designed so that after the pulse510exits the second section504, the maximum time compression of the pulse510may be achieved. The mode of the pulse electromagnetic wave should be that of J0(i.e., the zeroth order Bessel mode [F.Dorchies et al., Phys.Rev. Lett. vol. 82, p.4655(1999)]) to avoid surface damage on the fiber of second section504. The pulse length at the target508irradiation is designed to maximally excite the shock wave resulting from the pulse striking the target508. The tip504aof the second section504may be replaceable if necessary after the material damage caused by the pulse510and/or radiation.

The diameter d7of the second section504may be approximately 30 to approximately 500 microns, and typically, approximately 75 to approximately 125 microns. The resulting laser spot LS on the target508also has a size d8of approximately 100 microns. The accelerated number of protons is approximately 1011per laser shot with typical proton energies of approximately 1 MeV. The resulting ion (e.g., proton) beam510ais directly irradiated on the treatment field510(e.g., biological issues) from a distance d4which may in the range of approximately 0.1 to approximately 10 millimeters. After the treatment field510, a backscatter film (e.g., higher Z metal such as aluminum (Al))540may be positioned with a thickness of approximately 10 to approximately 50 microns to absorb radiation. Backscatter film540serves to backscatter x-rays toward the treatment field510. Therefore, the geometry of the backscatter film540may be straight as shown inFIG. 6or concave or another shape that surrounds the treatment field510.

Target508may be constructed in several ways. The target508may be constructed by varying at least four design parameters (thickness, material geometry, and surface) similarly to the target200as discussed above with respect toFIGS. 1-4E. In another embodiment, target508may be a thick, dense film such as plastic or a metal coated plastic. In another embodiment, target508may have a coating of metallic vapor surface designed to face the direction of the pulse510. In another embodiment, target508may be a metallic foil coated with hydrogen gas/liquid (e.g., water) spray602on the side facing away from the laser pulse510. In another embodiment, target508may be a spongy material with a porous structure (e.g., hydrocarbon, ceramic, or metals capable of absorbing a large amount of hydrogen or hydrogen rich substance) immersed in hydrogen. In another embodiment, shown inFIG. 7, a foil704made of a metallic material (e.g., Al) having a thickness in the range of approximately 10 to approximately 30 microns may be placed spaced apart from target508to screen the treatment field510from radiations of different characters and energies.

The accelerator system500may be used in the case of a medical application such as radiation oncology which allows for the irradiation of a treatment field such as tumorous tissue in situ (or under the skin surface) rather than from the exterior of the patient's body. In accelerating system500, ions (e.g., protons) are delivered to the spot of the tumor, for example, through a bodily opening or incision. Therefore, the typical energy of 100 to 200 MeV for a 10 to 20 cm range is not required. This type of irradiation is therefore nearly direct without significantly affecting healthy tissues.

The embodiments disclosed inFIGS. 1-5illustrate a system and method that may enable the delivery of ions (e.g., protons) energetic enough to make sufficiently high radiation dose for oncology and other applications. The disclosed embodiments may operate compactly, flexibly and inexpensively. The disclosed embodiments may be based on a high power compact light source irradiating a target(s) and associated devices described above. Many radiation oncology applications require irradiation of protons from outside of a body. Therefore, these applications may require energies beyond 100 MeV with a dose of approximately 1 Gy. The disclosed embodiments feature a method that may go beyond approximately 100 MeV with sufficient dose and irradiation properties needed for radiation oncology applications. Elements of the disclosed embodiments (which are described above) may include: deployment of intense compact high repetition laser and its conditions (particular laser technology to be deployed, intensity, pulse duration, aperture, and pulse shaping), irradiation of a target whose thickness, material (bimetal or bi-metal), geometry (concave and other variations) and surface (clusters or frustrated surface or other variations) are specified, the focusability and transport of the ion beams by the target geometry and additional magnetic and other transport devices, the prepulse control measures, the flexible adjustment, monitor, and feedback of various parameters of laser, target, optics, transport system, and treatment field, the overall systems concept, which among other things, allow flexible, compact, and inexpensive deployment of this device that includes intra-operative and portable usage as well as potential compatibility with existing treatment facilities. Unlike X-rays and electron beams, ion (e.g., proton) beams have a sharp Bragg peak, enabling the deposition of the precise dose at a predetermined location. With these flexible capabilities enabled in the disclosed embodiments a precise and flexible deposition of radiation dose may be possible. The disclosed embodiments may give rise to energies of beam protons (and other ions) in excess of approximately 100 MeV and doses in the range of approximately 0.01 to approximately 100 Gy, (and typically approximately 1 Gy), over an approximately 0.1 to approximately 100 second period (and typically approximately one second), which are in the range of oncological needs.

The embodiments disclosed inFIGS. 6-7allow for a compact delivery of protons, whose energy may be in the range of sub-MeV to several MeV with a similar (or less) dose. Since these embodiments may be inserted substantially adjacent to the location of the treatment field, this energy is sufficient to treat oncological targets.

The foregoing is for illustrative purposes and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.