| Paper | Title | Page |
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| WEPP132 | Efficiency Enhancement of Active High-Power Pulse Compressors | 2803 |
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| High power microwaves needed to accelerate particles in multi-TeV colliders can be produced using active pulse compressors. An active compressor has a storage cavity whose Q-factor is modulated by means of RF switch. An efficiency of such compressor is limited due to diffraction losses at power accumulation regime and in conventional case does not exceed 81.4%. A new microwave pulse compressor operated with a superposition of quasi-degenerated modes is suggested. A proper choice of eigen frequencies and Q-factors of these modes allows essential enhancement of efficiency (asymptotically up to 100%). A 30 GHz project of multi-megawatt compressor based on dual-mode circular cross-section cavity is considered. | ||
| WEPP133 | High-gradient Multi-mode Two-beam Accelerating Structure | 2806 |
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A new accelerating structure which is aimed to provide gradient >150 MV/m for next generation of multi-TeV linear colliders is suggested. The structure is based on periodic system of quasi-optical cavities*. Each of these cavities is excited in several equidistantly-spaced eigen modes by the drive beam in such a way that the RF fields reach peak values only during the short time intervals when an accelerating bunch is resident in the cavities, thus exposing the cavity surfaces to strong fields for only a small fraction of time. This feature is expected to raise the breakdown and pulse heating thresholds. The proposed structure embodies most of additional attractive properties: the cavity is an all metallic structure, no transfer or coupling structures are needed between the drive and acceleration channels, the cavity fields are symmetric around the axes of the drive beam and the accelerated beam, the cavity can exhibit high transformer ratio. Calculations of single quasi-optical rectangular cavity with parameters of drive and accelerating beams close to ones adopted for the CLIC project show that high gradient as well as high efficiency are achievable.
*S. V. Kuzikov et al. "Quasi-optical accelerating structure operated with a superposition of synchronized modes," Conf. Digest of Joint 32nd IRMMW Conf., Cardiff, UK, 2007, Vol.2, p.797-798. |
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| THPC091 | Experimental Study of an Intense Relativistic Helical Electron Beam Formed with Interception of the Electrons Reflected from the Magnetic Mirror | 3200 |
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| A new method of formation of pulsed intense relativistic helical electron beams (HEBs) for gyroresonant devices has been presented. The method is aimed at the increase of pitch-factor and the reduction of HEB velocity spread and is intended for use in the formation systems of laminar HEBs characterized by low influence of space charge on their parameters. The method is based on the operation of a special diaphragm located at one of minima of trajectories at the beginning of the transportation channel. The diaphragm diameter is chosen so that the electrons with the lowest oscillatory velocities cannot bend round the diaphragm and settle on it. The rest electrons pass by moving in the increasing magnetic field. Then, the electrons with the greatest oscillatory velocities are adiabatically reflected from the magnetic mirror between the electron gun and the transportation channel and settle on the back of the same diaphragm. Reduction of space charge of the reflected electrons has led to the increase of HEB pitch-factor (HEBs have been formed with the record of pitch-factors exceeding 2), while the accumulation of space charge worsens the HEB provoking modulation of formed HEB current. |