| Paper | Title | Page |
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| MOPPA004 | Energy Spread Decreasing in Linear Mode Operating Laser Plasma Wakefield Accelerator | 251 |
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Laser plasma wakefield acceleration (LPWA)* is one of most popular novel methods of acceleration. The LPWA is very perceptively because the accelerating gradient in plasma channel can be a number of orders larger than in metal structures. But the LPWA has two serous disadvantages as very high energy spread and low part of electrons trapped into acceleration. The energy spectrum better than 10% does not observed anyone in simulations or experiments. It should be noted that the electron's beam dynamics in LPWA is different for underdense plasma (quasi linear mode) and in for dense plasma (non-linear and bubble modes). Non-linear mode is studying more intensive at present and methods of the energy spread decrease are under development **,***. But the linear LPWA mode also has interest for practical use. The rate of energy gain is very high in the linear mode also and compact laboratory scale facility could be designed to accelerate the electron beam up to a hundreds MeV. Bunching before injection into plasma channel will discuss to decrease the energy spread and to enlarge the electron trapping efficiency.
* T. Tajima, J.M. Dowson. Phys. Rev. Lett., 1979, v. 43, 4, 267. ** S.V. Bulanovet al. Physics of Plasmas, 2008, 15, 073111. *** E.Esarey et al. Phys. Rev. Lett., 1997, 79, 2682. |
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| TUPPB009 | RF Self–Consistent Electron Beam Dynamics Simulation in THz Generator Based on Photoinjector and Cherenkov Decelerating System | 328 |
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| The generator of high intensity monochromatic radiation in sub-mm band is currently under R&D at the Department of Electrophysical Facilities of MEPhI. This generator is based on photoinjector and irradiating Cherenkov capillary. It is necessary to have high brightness electron beams to generate of monochromatic radiation in this type of structure. These beams can be produced by photocathode and accelerated to energy of several MeV using short structure having high rate of energy gain. Irradiating capillary represents metal tube having inner radius of the radiation wavelength order and covered with dielectric layer or made of corrugated waveguide. It's important to study the self-consistent dynamics of the beam during the acceleration as the pulse current is equal several A, i.e. the beam dynamics should be studied taking into account RF (radiation) field and Coulomb field of self space charge. Another task is to study the electron beam dynamics and fields irradiated by it in decelerating structure in the absence of external fields. The scheme of the facility, its operation mode and high-current beam dynamics simulation results in accelerating and irradiating structures are presented. | ||
| TUPPB011 | Analytical Approach for Beam Matching | 334 |
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| Charge particle beams transportation with small cross-sections and low energies is an actual problem for a gantry. That beams are used actively for isotope therapy. Beam emittance is its quality factor, and it should be matched with a facility channel acceptance. The method for beam dynamics analysis in lattice is developed in terms of non-coherent particle oscillation study. Nonlinear beam dynamics is investigated by using this method. It is shown that this technique allows one to realize effective beam emittance control. Analytical results obtained are verified by means of numerical simulation. | ||
| TUPPB012 | Search of the Motion Integral at Linac with RF Focusing | 337 |
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| The problem of the effective low-energy linac design is of interest to many fields of science, industry and medicine. It is well known that nonsynchronous harmonics of RF field (RF undulator) are focusing the particles. Analytical beam dynamics investigation can be carried out by means of the averaging method over the rapid oscillations period (the so-called smooth approximation) in the oscillating fields. Motion equation is presented in the form of the Hamilton's equations. Motion integrals are found by means of Poincare mapping. | ||
| TUPPB040 | Angiography X-ray Monochromatic Source Based on Radiation From Crystals | 406 |
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| Nowadays angiography has become one of the most commonly used medical procedures. However the X-ray tubes are mostly used in angiography imaging systems. The problem that encounters in using X-ray tubes is low monochromaticity due to bremsstrahlung while angiography imaging requires quasimonochromatic energy spectrum for better image quality and lower dose rate obtained by the patient. The use of the monocrystaline target at the medical electron LINAC can be one of the possible ways to obtain the monochromatic X-ray radiation. This type of X-ray generator will provide monochromatic radiation with photon energy dependent on the electron beam energy. The X-ray generation mechanism, possibilities of monocrystal usage as an X-ray source for angiography and requirements for beam parameters are discussed. | ||
| WEPPC009 | Using Genetic Algorithms for Electrode Shape Optimization in Accelerators with RF Focusing | 461 |
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| The drift tubes shape choice which provides the require distribution of the spatial harmonics amplitudes of RF field is an important problem in the design of RF focusing accelerators. It is necessary to have various relationships of the main (accelerating) and the first (as main focusing) harmonics of RF field for different types of accelerators. High order harmonics should be negligible for accelerators with an external focusing, and this ratio should be E1/E0 = 3-5 for the efficient operation of the axially symmetric RF focusing accelerator. Thus, the distribution and harmonic amplitude's ratios at the accelerator axis which provides stable beam dynamics are always known. The drift tubes shape study problem cannot be solved directly by ordinary methods because of unknown boundary conditions belongs to a class of ill-posed problem. At present, this problem can be solved by using genetic algorithms (GA). For this purpose, the electrode shape will be represent as the polynomial function, and then solve the Laplace equation with boundary conditions of Dirichlet and Neumann. The necessary electrodes shape can be quickly and easily simulated using the adaptive search. | ||
| WEPPC037 | Cylindrical Phased Dipoles Array for Hyperthermia of Deep-Situated Tumors | 521 |
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| The treatment of deep-situated malignant tumors is often a difficult problem in which the purpose is to reduce the size of completely remove a tumor by using one or more modalities. The traditional methods are: radiation therapy, chemotherapy and surgery. Hyperthermia is another method which is used alone or coupled with other methods of cancer treatment. Hyperthermia is a heating of the tumor that makes it more sensitive to chemotherapy or radiation therapy and leads to it thermal damage. Temperature range for hyperthermia treatment is from 42.5 C to 45 C. It is important to prevent heating of healthy tissues and to produce sufficient heating at the site of a deep-situated tumor. This kind of hyperthermia is called the local hyperthermia. The electromagnetic field in 100-200 MHz frequency range is optimal for heating of deep-situated tumors. The system for local hyperthermia of cancer was simulated. This system is based on cylindrical phased array consisting of multiple dipole antennas with operating frequency 150 MHz. The electric fields and specific absorption rate distributions are calculated in cut of tissue-equivalent phantom. Shown that electric field can be focused in desirable region by means of varying of amplitudes and phases of each dipole. The advantages of using combined therapy of common hyperthermia with chemotherapy or radiation therapy are discussed. | ||
| WEPPC038 | RF Power and Control Systems for Phased Dipoles Array System for Hyperthermia | 524 |
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| Cylindrical array of independently phased dipoles is suggested for hyperthermia of deep-situated tumors as a kind of treatment of cancer coupled with other methods such as radiation therapy and chemotherapy. It was proposed to focus the maximum of electromagnetic field at the site of tumor to produce high efficiency heating of tumor and to prevent overheating of surrounding healthy tissues. That's why we use system of independently fed dipole antennas. The operating frequency is 150 MHz. The independent feeding permits us to focus electromagnetic field producing by phased array in desirable area by means of changing of amplitudes and phases of each dipole. The RF power system schematic layout for 8 independently phased dipole antennas is presented. The control system of RF power system elements is considered. The software developing to provide choosing amplitude's and phase's values of dipoles are discussed. | ||
| WEPPC046 | RF Photoinjector Parameters Optimization | 535 |
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| Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector for THz source are reported. The photoinjector is based on disk loaded waveguide (DLW). Photoinjector consists of two accelerating structures: widespread 1.6 cell DLW structure and travelling wave resonator structure based on 8 cells traveling wave accelerating structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Electrodynamics models were tuned to the resonant frequency of 3000 MHz. Magnetic field coupling between cells of accelerating structure and optimization of the diaphragms sizes were analyzed to enlarge the structures efficiency. Diaphragms windows profiles were optimized to decrease the overvoltage on the windows edges and to eliminate the breakdown possibility. | ||