A high gradient linear accelerating structure can propagate high frequency waves at a negative harmonic to accelerate low-energy ions. The linear accelerating structure can provide a gradient of 50 MV/m for particles at a of between 0.3 and 0.4. The high gradient structure can be a part of a linear accelerator configured to provide an energy range from an ion source to 450 MeV/u for .sup.12C.sup.6+ and 250 MeV for protons. The linear accelerator can include one or more of the following sections: a radiofrequency quadrupole (RFQ) accelerator operating at the sub-harmonic of the S-band frequency, a high gradient structure for the energy range from 45 MeV/u to 450 MeV/u.

A new ring coupling structure for a linear accelerator includes an acceleration cavity, a coupling cavity, and a beam hole. The acceleration cavity and the coupling cavity are alternately assembled together. The beam hole penetrates through the acceleration cavity and the coupling cavity. The acceleration cavity adopts a bowl-shaped structure, a convex cone structure with a mesoporous is disposed on an inner wall of the acceleration cavity along the beam hole. Coupling holes between the acceleration cavity and the coupling cavity are designed as at least two waist-shaped holes uniformly distributed around the beam hole. The coupling cavity adopts a disc-shaped cavity structure with a thickened edge, and a nose cone is disposed in the coupling cavity and welded with cavity walls at both ends of a coupler. The left and right waveguide plates of the coupling cavity are welded together by using the nose cone.

The invention provides a method for accelerating protons and carbon ions up to 450 MeV/u in a very compact linac, the method comprising subjecting the particles to a radio frequency quadrupole field to accelerate the particles to at least 3 MeV/u, a drift tube linac (DTL) to an energy of 20 MeV/u, followed by a coupled DTL to 45 MeV/u and finally a high-gradient section made of CCL-type standing wave cavities or negative harmonic traveling wave cavities operating at S-band frequencies and capable of delivering voltage gradients of 40 to 60 MV/m. Focusing the accelerated particles while accelerated to higher energy is provided by appropriately placed constant field permanent magnets and electromagnetic quadrupoles. The compactness and power efficiency of the linac is enabled by using high-gradient structure in the S-band frequencies for lower energy particles than ever before. The low-intensity required for hadron therapy allows the use of small-aperture S-band structures and the operation at very high gradient compared to high-intensity machines for research. Operating with very short sub-microsecond pulses at repetition rates up to 400 Hz allows the fast and flexible beam energy and intensity tuning not provided by existing hadron therapy machines. The designed linac is capable of accelerating ions as heavy as neon to the full 450 MeV/u energy, therefore allowing fast beam switching if different ion sources are installed in the front-end of the linac.

The present invention discloses a homologous dual-energy accelerator and a therapy device comprising the homologous accelerator. The homologous dual-energy accelerator comprises an electron emitting device and an accelerating device, wherein the electron emitting device is located at the input end of the accelerating device, and electrons generated by the electron emitting device are emitted from the output end of the accelerating device after being accelerated by the accelerating device; the homologous dual-energy accelerator further comprises at least one separation deflection device which is arranged on the output end side of the accelerating device and used for changing the motion trail of partial electrons among the electrons accelerated by the accelerating device. The homologous dual-energy accelerator has the advantages that the inventor discovers that the speeds and energy of all electrons are not completely same after the electrons are accelerated by the accelerating device; the inventor uses the separation deflection device arranged on the output end side of the accelerating device through the discovery, the motion trail of partial electrons having relatively low energy level among the particles accelerated by the accelerating device is forcibly changed, the electrons having different energy levels in a homologous electron beam are separated, and two energy levels of electron beams are thus obtained, wherein the high-energy electron beam continues an original path and is used for radiotherapy, and the other path of low-energy electron beam is used for tracking lesions and detecting the therapeutic effect.

The invention provides a method for accelerating protons and carbon ions up to 450 MeV/u in a very compact linac, the method comprising subjecting the particles to a radio frequency quadrupole field to accelerate the particles to at least 3 MeV/u, a drift tube linac (DTL) to an energy of 20 MeV/u, followed by a coupled DTL to 45 MeV/u and finally a high-gradient section made of CCL-type standing wave cavities or negative harmonic traveling wave cavities operating at S-band frequencies and capable of delivering voltage gradients of 40 to 60 MV/m. Focusing the accelerated particles while accelerated to higher energy is provided by appropriately placed constant field permanent magnets and electromagnetic quadrupoles. The compactness and power efficiency of the linac is enabled by using high-gradient structure in the S-band frequencies for lower energy particles than ever before. The low-intensity required for hadron therapy allows the use of small-aperture S-band structures and the operation at very high gradient compared to high-intensity machines for research. Operating with very short sub-microsecond pulses at repetition rates up to 400 Hz allows the fast and flexible beam energy and intensity tuning not provided by existing hadron therapy machines. The designed linac is capable of accelerating ions as heavy as neon to the full 450 MeV/u energy, therefore allowing fast beam switching if different ion sources are installed in the front-end of the linac.

The present invention discloses a homologous dual-energy accelerator and a therapy device comprising the homologous accelerator. The homologous dual-energy accelerator comprises an electron emitting device and an accelerating device, wherein the electron emitting device is located at the input end of the accelerating device, and electrons generated by the electron emitting device are emitted from the output end of the accelerating device after being accelerated by the accelerating device; the homologous dual-energy accelerator further comprises at least one separation deflection device which is arranged on the output end side of the accelerating device and used for changing the motion trail of partial electrons among the electrons accelerated by the accelerating device. The homologous dual-energy accelerator has the advantages that the inventor discovers that the speeds and energy of all electrons are not completely same after the electrons are accelerated by the accelerating device; the inventor uses the separation deflection device arranged on the output end side of the accelerating device through the discovery, the motion trail of partial electrons having relatively low energy level among the particles accelerated by the accelerating device is forcibly changed, the electrons having different energy levels in a homologous electron beam are separated, and two energy levels of electron beams are thus obtained, wherein the high-energy electron beam continues an original path and is used for radiotherapy, and the other path of low-energy electron beam is used for tracking lesions and detecting the therapeutic effect.

A high gradient linear accelerating structure can propagate high frequency waves at a negative harmonic to accelerate low-energy ions. The linear accelerating structure can provide a gradient of 50 MV/m for particles at a of between 0.3 and 0.4. The high gradient structure can be a part of a linear accelerator configured to provide an energy range from an ion source to 450 MeV/u for .sup.12C.sup.6+ and 250 MeV for protons. The linear accelerator can include one or more of the following sections: a radiofrequency quadrupole (RFQ) accelerator operating at the sub-harmonic of the S-band frequency, a high gradient structure for the energy range from 45 MeV/u to 450 MeV/u.

A method for the suppression of upstream-directed field emission in RF accelerators. The method is not restricted to a certain number of cavity cells, but requires similar operating field levels in all cavities to efficiently annihilate the once accumulated energy. Such a field balance is desirable to minimize dynamic RF losses, but not necessarily achievable in reality depending on individual cavity performance, such as early Q.sub.0-drop or quench field. The method enables a significant energy reduction for upstream-directed electrons within a relatively short distance. As a result of the suppression of upstream-directed field emission, electrons will impact surfaces at rather low energies leading to reduction of dark current and less issues with heating and damage of accelerator components as well as radiation levels including neutron generation and thus radio-activation.

A slot-coupled CW standing wave multi-cell accelerating cavity. To achieve high efficiency graded beta acceleration, each cell in the multi-cell cavity may include different cell lengths. Alternatively, to achieve high efficiency with acceleration for particles with beta equal to 1, each cell in the multi-cell cavity may include the same cell design. Coupling between the cells is achieved with a plurality of axially aligned kidney-shaped slots on the wall between cells. The slot-coupling method makes the design very compact. The shape of the cell, including the slots and the cone, are optimized to maximize the power efficiency and minimize the peak power density on the surface. The slots are non-resonant, thereby enabling shorter slots and less power loss.

A method for the suppression of upstream-directed field emission in RF accelerators. The method is not restricted to a certain number of cavity cells, but requires similar operating field levels in all cavities to efficiently annihilate the once accumulated energy. Such a field balance is desirable to minimize dynamic RF losses, but not necessarily achievable in reality depending on individual cavity performance, such as early Q.sub.0-drop or quench field. The method enables a significant energy reduction for upstream-directed electrons within a relatively short distance. As a result of the suppression of upstream-directed field emission, electrons will impact surfaces at rather low energies leading to reduction of dark current and less issues with heating and damage of accelerator components as well as radiation levels including neutron generation and thus radio-activation.