| Paper | Title | Other Keywords | Page |
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| MOPEB036 | A HTS Scanning Magnet and AC Operation | superconductivity, resonance, coupling, proton | 352 |
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A scanning magnet using high-temperature superconductor (HTS) wire was designed, fabricated, and tested for its suitability as beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. With DC current the magnet was successfully operated to generate designed field distributions and effective length. In AC mode, the magnet was operated at frequencies of 30-59 Hz and a temperature of 77 K as well as 10-20 Hz and 20K. The power loss dissipated in the coils was measured and compared with the model calculations. The observed loss per cycle was independent of the frequency and the scaling law of the excitation current was consistent with theoretical predictions for hysteretic losses in HTS wires. |
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| MOPEC051 | Induction Acceleration System for KEK Digital Accelerator | acceleration, ion, synchrotron, controls | 573 |
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The KEK-DA (Digital Accelerator) is a modification of the KEK 500 MeV booster*, in which an induction acceleration system is employed. It has an ability to accelerate arbitrary ions with their possible charge states**. An outline of the acceleration scenario is described and a necessary control system fully integrating the induction acceleration system is given in details. The KEK-DA is a rapid cycle synchrotron operating at 10 Hz; the accelerating pulse voltage must be dynamically varied in time to follow the ramping magnetic field. A novel technique combining the pulse density control and intermittent operation of acceleration cells is required. The intelligent gate control system which uses 1 GHz digital signal processors (DSPs) has been designed. Construction of the KEK-DA is in the final stage; installation of the induction cells and the power supplies are done. The whole system including gate control system is demonstrated with high voltage outputs,long-term stability of the system through a heat run is examined. Also a future plan which replaces DSPs by FPGA (Field Programmable Gate Array)is discussed. * K.Takayama et al., JOURNAL OF APPLIED PHYSICS 101, 063304 (2007). |
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| MOPEC052 | KEK Digital Accelerator for Material and Biological Sciences | ion, acceleration, vacuum, injection | 576 |
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A novel circular accelerator capable of accelerating any ions from an extremely low energy to relativistic energy is discussed. A digital accelerator (DA)* is based on the induction synchrotron concept, which had been demonstrated in 2006. All ions are captured and accelerated with pulse voltages generated by induction acceleration cell (IAC). The IAC is energized by the switching power supply, in which power solid-state conductors are employed as switching elements and their tuning on/off is maneuvered by gate signals digitally manipulated from the circulating signal of an ion beam. Acceleration synchronized with the revolution of the ion beam is always guaranteed. The concept is realized by renovating the KEK 500 MeV booster into the DA, introducing a laser ablation ion source. Ion energy of 85-140 MeV/au and intensity of 10+9 - 10+10 /sec are estimated and these ions will be delivered without any large-scale injector. Companion papers** will discuss more details of instruments of DA. Applications for innovative material sciences and life sciences will be briefly introduced as well as the outline of DA. *K. Takayam, J. of Appl. Phys. 101 (2007) 063304. |
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| MOPD036 | Simulations of Buncher-cavities with Large Apertures | cavity, simulation, linac, status | 765 |
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Buncher-cavities re-accelerate, bunch or re-bunch particle beams. A special form of these buncher-rf-cavities is a spiral-structure. Two different spiral resonators were simulated and build for the new EBIS LINAC at Brookhaven National Laboratory. These buncher-cavities have a remarkably large aperture of 100 mm. To optimize the cavities to the BNL-frequency of 100 MHz, simulations have been carried out. The impact of changing the gap width, drifttube-, and spiral arm-length on the design of the spiral cavities, has been analyzed. Results of simulations and measurement will be presented. |
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| MOPE027 | Simulations for the Measurements of Longitudinal Bunch Profile using Coherent Smith-Purcell Radiation | radiation, simulation, electron, diagnostics | 1026 |
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The coherent Smith-Purcell radiation (CSPR) has been demonstrated as an efficient technique for measuring the longitudinal profile of beam bunches. To measure the ultrashort beam bunches, the simulations for the measurements using CSPR are anlyzed with tools of three dimensional particle-in-cell simulations and Kramer-Kronig reconstruction. Different parameters such as rms length of beam bunch and profiles of grating are studied. Furthermore, the measurement device based on a Martin-Puplett Interferometer is introduced, in which noises and attenuation can be reduced. |
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| WEPD015 | Inductive Shimming of Superconductive Undulators: Preparations for a Realistic Test | undulator, coupling, alignment, controls | 3117 |
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The monochromaticity and intensity of synchrotron light emitted by undulators strongly depend on the undulator field quality. For the particular case of superconductive undulators it was shown recently that their field quality can be significantly improved by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. Local field errors induce currents in the coupled closed superconducting loops and, as a result, the hereby generated magnetic field minimizes the field errors. In previous papers the concept was described theoretically and a proof-of-principle experiment was reported. This paper reports results of the first quantitative measurement of the phase error reduction in a 12-period short model undulator equipped with a full-scale induction shimming system. |
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| WEPD099 | Secondary Electron Trajectories in High-gradient Vacuum Insulators with Fast High-voltage Pulses | electron, vacuum, simulation, high-voltage | 3332 |
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Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from the triple junction. These electrons strike the insulator surface and produce secondary electrons, which also strike the insulator surface to create more secondary electrons and lead to avalanche. Magnetic field from the external sources, the high-current electron beam, the conduction current in the transmission line or the displacement current in the insulator can deflect primary and secondary electrons' trajectories either toward to or away from the insulator surface, and hence affect the performance of the high-voltage vacuum insulator. The displacement current effects are particularly interesting for short pulse applications. This paper presents the displacement current effects with various short applied voltage pulses on performance of high-gradient insulators. Optimal HGI configurations will also be discussed. |
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| THPEA025 | HOM Characteristics Measurement of Mini-LIA Cavity | cavity, HOM, simulation, higher-order-mode | 3732 |
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Mini-LIA was a miniature linear induction accelerator designed and manufactured by China Academy of Engineering Physics and Tsinghua University. To investigate the higher order mode (HOM) of Mini-LIA cavity, especially the frequency and quality factor Q of the TM110 and TM120 in it, both numerical simulation and experiments were performed. Several models of the cavity were established and calculated by using E module of MAFIA code. Network analyzer was applied to measure the frequency and Q in cavity. Both the simulation results and the experiment results are presented in this paper. The results of the experiments were coincident with the calculated results. Finally, The HOM characteristic of Mini-LIA cavity with metglass core in it was explored, and some interesting results was obtained. |
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| THPD058 | Definition of Focusing System Parameters on the Basis of the Analysis of a Transverse Bunch Dynamics in Dielectric Loaded Wakefield Accelerator | focusing, wakefield, acceleration, electron | 4416 |
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The strong focusing of high current relativistic electron beams in multi-bunch wakefield acceleration is investigated. These beams are used for generating wake fields in dielectric loaded accelerating structures. We consider ramped charge distribution in the sequence of high current drive bunch. It is shown that the beam focusing system dumping beam break-up effect and elongating of a maximum distance the high current beam can travel determines the effectiveness of the energy transfer to the accelerated electron bunch. The optimal parameters of the focusing system on the basis of self-consistent transverse dynamics analysis are determined. |
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| THPD061 | Nonlinear Theory of Wakefield Excitation in A Rectangular Multizone Dielectric Resonator | wakefield, electromagnetic-fields, electron, vacuum | 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. |
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| THPD073 | Acceleration Module in Linear Induction Accelerator | cavity, high-voltage, acceleration, impedance | 4449 |
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Linear Induction Accelerator (LIA) is a unique type of accelerator, which is capable to accelerate kilo-Ampere beam current to tens of MeV. The LIA acceleration modules, filled with ferrite or ferromagnetic toroid cores, can be conveniently stacked to obtain high energy. During the evolution of LIA, several models for the LIA acceleration module and the function of the cores have been proposed. Authors of this paper surveyed these models and tried to bridged them to form a consistent understanding of the LIA acceleration module. The unified understanding should be helpful in the further development and design of the LIA acceleration module. |
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| THPD087 | Potential Forms for Electrostatic and Magnetic Cylindrical Lens and Tracking of Charged Particle | solenoid, optics, proton, focusing | 4488 |
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A cylindrical lens is mainly used for focusing and transporting low energy beam. Some analytical forms of scalar potential have been formulated to evaluate electric and magnetic field and its derivatives on the central axis, which help in evaluation of potential and field in the region about the central axis. They are, subsequently, used to analytically find out the optical properties of a lens as well as in tracking of charged particles. It turns into a tool to design an electrostatic or a magnetic cylindrical lens. A section-technique has been developed to evaluate the optical cardinal points of a thick lens very accurately. Smooth profiles of the field and potential along the axis are divided into large number of small stepped profile. Each step represents a weak thin lens as change in radial movement is very small. The effect of the individual weak lenses is evaluated and combined by matrix multiplication method to get optical property of the thick lens. The obtained values are verified by exactly tracking the particles by solving the Lorentz equation of motion of charged particle in electric or magnetic field. |