| Paper | Title | Other Keywords | Page |
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| MOPE041 | Peculiarities of Bunch Shape Measurements of High Intensity Ion Beams | target, electron, simulation, ion | 1065 |
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Bunch shape monitors with low energy secondary electrons transverse modulation have found a use for measurements of longitudinal distribution of charge in bunches for ion linear accelerators. Temporal bunch structure is coherently transformed into the spatial distribution through transverse rf scanning. The fields of the analyzed beam can influence the trajectories of the secondary electrons thus resulting in a distortion of the transformation and hence to a deterioration of measurement accuracy revealed in worsening of a phase resolution and in appearance of an error of phase reading. The first error component aggravates observation of the bunch fine structure. The second one distorts the measured shape of the bunch as a whole. Two models have been used for the effect analysis. In the first model a target potential of the bunch shape monitor is supposed to be undistorted by the analyzed beam space charge. In the second model a target potential is completely defined by the potential of the analyzed beam bunch. The applicability of the two models is discussed. The results of simulations for typical beam parameters are presented for the latest bunch shape monitor elaborations. |
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| TUPEC048 | Coupling Impedance Contribution of Ferrite Devices: Theory and Simulation | impedance, coupling, kicker, wakefield | 1829 |
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Beam coupling impedances have been identified as an appropriate quantity to describe collective instabilities caused through beam-induced fields in heavy ion synchrotron accelerators such as the SIS-18 and the SIS-100 at the GSI facility. The impedance contributions caused by the multiple types of beamline components need to be determined to serve as input condition for later stability studies. This paper will discuss different approaches to calculate the Coupling Impedance contribution of ferrite devices, exploiting the abilities of both commercial codes such as CST STUDIO SUITE® and specific extensions of this code to address kicker related problems in particular. Before addressing actual beamline devices, benchmark problems with cylindrical and rectangular geometry will be simulated and the results will be compared with the corresponding analytical formulations. |
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| TUPD050 | Impedances of an Infinitely Long and Axisymmetric Multilayer Beam Pipe: Matrix Formalism and Multimode Analysis | impedance, space-charge, vacuum | 2039 |
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Using B. Zotter's formalism, we present here a novel, efficient and exact matrix method for the field matching determination of the electromagnetic field components created by an offset point charge travelling at any speed in an infinitely long circular multilayer beam pipe. This method improves by a factor of more than one hundred the computational time with three layers and allows the computation for more layers than three. We also generalize our analysis to any azimuthal mode and finally perform the summation on all such modes in the impedance formulae. In particular the exact multimode direct space-charge impedances (both longitudinal and transverse) are given, as well as the wall impedances to any order of precision. |
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| TUPD053 | The Six Electromagnetic Field Components at Low Frequency in an Axisymmetric Infinitely Thick Single-Layer Resistive Beam Pipe | impedance, vacuum, coupling, space-charge | 2048 |
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In this study B. Zotter's formalism is applied to a circular infinitely long beam pipe made of a conductor of infinite thickness where an offset point-charge travels at any given speed. Simple formulae are found for the impedances and electromagnetic fields both at intermediate frequencies (recovering Chao's results) and in the low frequency regime where the usual classic thick wall impedance formula does not apply anymore due to the large skin depth compared to the pipe radius. |
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| THPEA019 | Thermal Deformation of Magnetic Alloy Cores for J-PARC RCS RF Cavities | cavity, synchrotron, gun, monitoring | 3717 |
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Several magnetic alloy cores of the RF cavities, which are installed in the 3 GeV rapid cycling synchrotron (RCS) of J-PARC have shown buckling after about two years operation. To find the reason, why the local deformation happened, we made a test setup. There we heat up MA cores in air by 500 kHz RF and measure the thermal deformation in order to collect information about the buckling process. The results obtained by comparing the expansion of cores made by different production methods are reported. |
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| THPEA051 | A Method for Establishing Q-factors of RF Cavities | cavity, electron, linac, acceleration | 3789 |
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The distribution of electromagnetic fields in an RF cavity is primarily determined by the geometry of the RF cavity. The quality factor (Q-factor) of an RF cavity characterizes RF losses in the cavity: an RF cavity having a higher Q-factor is a more efficient user of RF power. However, a cavity having a lower Q-factor can operate on a wider range of frequencies, shorter filling time and may be more stable and less sensitive to input power perturbations. A method is discussed in this paper for an RF cavity that provided a desired Q-factor for the cavity while enabling a desired field distribution for electron acceleration within the cavity. The structure forming the inner wall of the RF cavity may be comprised of different types of material(such as copper and steel). Using different materials for different portions of the inner walls forming a cavity will cause different Q-factors for the cavity while the shape of the cavity remains constant. contact: ding@radiabeam.com |
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| THPEA065 | RF Choke for Standing Wave Structures and Flanges | vacuum, coupling, resonance, quadrupole | 3822 |
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SLAC participates in the U.S. High Gradient collaboration whose charter includes basic studies of rf breakdown properties in accelerating structures. These studies include experiments with different materials and construction methods for single cell standing wave accelerating structures. The most commonly used method of joining cells of such structures is the high temperature bonding and/or brazing in hydrogen and/or vacuum. These high temperature processes may not be suitable for some of the new materials that are under consideration. We propose to build structures from cells with an rf choke, taking the cell-to-cell junction out of the electromagnetic field region. These cells will be clamped together in a vacuum enclosure, the choke joint ensuring continuity of rf currents. Next, we propose a structure with a choke joint in a high gradient cell and a view port which may allow us microscopic, in-situ observation of the metal surface during high power tests. And third, we describe the design of a TM01 choke flange for these structures. |
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| THPD061 | Nonlinear Theory of Wakefield Excitation in A Rectangular Multizone Dielectric Resonator | wakefield, electron, vacuum, induction | 4422 |
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To excite intensive accelerating fields a multi-zone dielectric structures can be used*. As have shown already carried out researches, at their excitation by relativistic charged particle bunches the maximal amplitude of an accelerating field significantly depends on group velocity of energized waves. Till now these effects in wakefield multi-zone dielectric accelerators in details are not investigated. In addition the large charge of drive bunches requires the obligatory account of its space charge on bunch dynamics. To account the specified effects we built the nonlinear self-consistent theory of wake field excitation in the multilayered dielectric resonators. Expressions for excited fields, functionally depending on position of bunch particles in the resonator are found analytically. Excited fields are presented in the form of superposition solenoidal (LSE and LSM types) and potential fields. The nonlinear theory built in a general view is valid for any number of dielectric layers. Use of the constructed theory for the account of nonlinear and groups velocity effects is demonstrated on an example of 5-zone dielectric resonator with parameters close to experiment**. * C. Wang et.al. In Proc. PAC 2005. IEEE, 2005, p. 1333. |