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ACCELERATING STRUCTURE FOR C-BAND ELECTRON LINEAR ACCELERATOR |
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A.A. Anisimov¹, R.O. Bolgov¹, S.V. Kutsaevª¹, N.P. Sobenin¹, M. Ferderer², A.A. Zavadtsev², A.A. Krasnov² ¹Moscow Engineering Physics Institute (State University), Moscow, Russia ²Identification Beam Systems LLC, Atlanta, USA Abstract This paper presents the results of a survey study that analyzed and compared several linear accelerator designs operating in the range of 5 to 20 MeV for use in advanced cargo inspection systems. These designs were based on klystron generated RF power input of 3.2 and 4.5 MW at 5712 MHz. Several different accelerating structures were considered including standing wave (SW) and travelling wave (TW) structures. In addition several hybrid structures, composed of a SW buncher section and TW accelerator section, were included in the study. Cells geometries and beam dynamics parameters, for these accelerating structures, were calculated using advanced numerical simulation methods. Accelerating structures and input couplers for SW and hybrid structures were designed. ª corresponding author |
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DEVELOPMENT OF THE INR DTL RF SYSTEM CROWBAR OPERATION |
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A.I. Kvashaª, V.L. Serov Institute for Nuclear Research of Russian Academy of Sciences, Moscow, Russia Abstract DTL RF system of the INR linear accelerator consists of five RF channels. In turn, each channel maintains two powerful series connected vacuum tubes, installed in anode modulator and RF power amplifier PA. Operation of the both tubes is supplied with crowbar system that defends vacuum tubes from destroying as result of breakdowns in one of them. Since the energy storage in the INR DTL anode modulator is artificial forming line AFL (with impedance value 24 Ohm) in crowbar system can be used series thyristors and starting block, which opens the thyristors, when PA vacuum tube anode pulse current exceeds set-point value. In the paper an analysis of the processes in AFL and crowbar system is considered. Some results of the crowbar system upgrade are presented. ª corresponding author |
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DIFFRACTION ACCELERATING STRUCTURE FIELD DISTRIBUTION MEASUREMENTS |
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A.Yu. Baranov, A.N. Kamanin, N.I. Pakhomov, V.I. Shvedunovª Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia Abstract We describe method and results of field distribution measurements for the diffraction accelerating structure consisting of two conducting gratings embedded in dielectric. This structure with operating aperture close to wavelength can be used for high gradient acceleration in millimetre-miρron wavelength range. ª corresponding author |
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EXTERNAL PARAMETERS CALCULATIONS FOR RF RESONATOR EXCITED OVER AN APERTURE |
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V.G. Kurakinª Lebedev Physical Institute of Russian Academy of Sciences, Moscow, Russia Abstract Bubnov and Galerkin method is used to calculate the coupling strength and cavity detuning for an rf cavity being powered by rf waveguide over a rectangular aperture in cavity surface. Both these so call external parameters are of a value in order to develop properly accelerating system of an accelerator. Electrical fields on coupling aperture surfaces are approximated by finite sums coordinate functions and expansion coefficients are found out by appropriate procedure of solution join of neighboring regions. In Bubnov and Galerkin method, this procedure provides energy flow continuity while crossing coupling surfaces, and this provides fast convergence of appropriate infinite sums. Expressions for aperture conductances are derived followed by formulae for reflection coefficient and cavity detuning. ª corresponding author |
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HIGH-GRADIENT TWO-BEAM ACCELERATING STRUCTURE |
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S.V. Kuzikov¹, S. Kazakov²³, M.E. Plotkinª¹, J.L. Hirshfield³ ¹Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russia ²High Energy Accelerator Research Organization, Tsukuba, Japan ³Omega-P Inc., New Haven, USA Department of Physics, Yale University, New Haven, USA Abstract A new accelerating structure, which is aimed to provide gradient >150 MV/m for next generation of multi-TeV linear colliders, is suggested [1-3]. The structure is based on periodic system of quasi-optical cavities, which are not coupled with each other. Each of these cavities is excited in several equidistantly-spaced eigen modes by the spatially bunched 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 a cavity, thus exposing the cavity surfaces to strongest fields for only a small fraction of time. This feature is expected to raise the breakdown and pulse heating thresholds. The proposed structure has smaller ratio α of maximal surface field to accelerating gradient (1<α<2) in comparison with usual single-frequency structure, where this ratio is close to factor 2. Due to all cavities of new accelerating structure are uncoupled, the structure is very reliable, i.e. possible breakdown in a separate cavity does not spoil the whole accelerator. High efficiency and transformer ratio of drive beam power to accelerating beam power are expected to be provided by means of a so-called idea of frequency detuning. In accordance with this idea high-current drive beam leaves its power in a distributed way (at long distance along accelerator). This is achievable due to detuning of eigen frequencies of a structure cavity out of drive bunch frequency. Calculations of a new two-beam accelerating structure consisted of multi-mode rectangular cavities with the parallel driving and accelerated beams, show that high gradient (~150 MV/m), low surface field (~190 MV/m), and high efficiency (~30%) are achievable under beam parameters close to those projected for CLIC (CERN). This 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. ª corresponding author |
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MULTIPACTOR SIMULATIONS IN AXISYMMETRIC AND NON-AXISYMMETRIC RADIO FREQUENCY STRUCTURES |
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M.A. Gusarova¹, I.V. Isaev¹, V.I. Kaminsky¹, S.V. Kutsaevª¹, M.V. Lalayan¹, N.P. Sobenin¹, L.V. Kravchuk² ¹Moscow Engineering Physics Institute (State University), Moscow, Russia ²Institute for Nuclear Research of Russian Academy of Sciences, Moscow, Russia Abstract A new computer code for simulation of multipacting phenomenon in axisymmetric and non-axisymmetric radio frequency (RF) structures is presented. Simulation results in various RF devices are compared with theoretical calculations and experimental measurements. ª corresponding author |
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RF-GAP MODEL PRESENTATION |
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V.A. Moiseevª Institute for Nuclear Research of Russian Academy of Sciences, Moscow, Russia Abstract To design the linear accelerators and to make the particle tracking simulations a rf-gap model for the accelerating cells has to be implemented. The standard rectangular rf-gap field presentation, as well the trapezium and cos-like waveform field models were analyzed and compared. ª corresponding author |
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THE RF POWER SUPPLY SYSTEM OF THE ΜΡΡ-30/15 CYCLOTRON |
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I.N. Vasilchenko, V.G. Mudrolubovª, A.P. Strokach Federal State Unitary Enterprise Efremov Scientific Research Institute of Electrophysical Apparatus, Saint-Petersburg, Russia Abstract The RF power supply system for exciting the resonance system of the ΜΡΡ-30/15 cyclotron is presented. The main parameters of the RF power supply system are: the 40.68 MHz operating frequency, the 25 kW output power (the continuous mode), the operating mode-continuous or pulse. The parameters of the RF power supply system, its schematic and characteristics of the main units are given. ª corresponding author |
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THEORY OF THERMAL FATIGUE OF A COPPER SURFACE UNDER THE ACTION OF PULSED MICROWAVE HEATING |
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S.V. Kuzikov, M.E. Plotkinª Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russia Abstract The normal conducting electron-positron Linear Collider projects imply that accelerating structures and other RF components will undergo an action of extremely high RF fields. Except for the RF breakdown threat, there is an effect of the copper surface damage due to cyclic heating of the skin-layer under the action of currents, induced by microwave irradiation. In this paper we would like to introduce a new "grain" model of the processes responsible for the fatigue of the copper surface [1]. This model is based on the quasi-elastic interaction between neighboring grains in the copper due to the thermal expansion of the skin layer. This mechanism of fatigue is compared with another, where stresses are generated by the temperature gradient towards the bulk of the material. With the proposed formalism one can estimate the total number of the RF pulses required to fracture the surface depending on the temperature rise, pulse length and steady state temperature. The parameters necessary to finalize the proposed approach were found through the comparison of experimental data obtained at 11.424 GHz. ª corresponding author |
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UPGRADE OF FEEDBACK LOOPS IN ACCELERATING CAVITIES OF U70 |
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A. Markinª, V. Chubrik, S. Ivanov, O. Lebedev, I. Sulygin Institute of High Energy Physics, Protvino, Russia Abstract The entire accelerating system of the U70 proton syn-chrotron of IHEP-Protvino comprises 40 identical ferrite-loaded cavities yielding 10 kV per gap max [1]. To ensure control over amplitude and phase of RF voltage across the each accelerating gap, two feedback loops per cavity are employed for automatic voltage amplitude (shortly, AVC) and automatic resonant frequency (AFC) controls. Attaining higher intensity and better quality of beam in the U70 depends upon operational performance of the AVC and AFC circuits in question. To this end, these cru-cial sub-systems were recently renovated so as to imple-ment the up-to-date hardware and electrical-circuit solu-tions. The paper contains a brief technical specification of the thus updated feedbacks. Experience acquired during their turning on and beam-testing results are presented. ª corresponding author |
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