International Journal of Applied Electromagnetics and Mechanics - Volume 14, issue 1-4

Authors: Nisiyama, Shusuke | Tomioka, Satoshi | Enoto, Takeaki

Article Type: Research Article

Abstract: In this paper, a scattered field Finite-Difference Time-Domain (FD-TD) method is applied to wake-fields computation. In the ordinary FD-TD method or other methods based on the finite difference scheme, the trajectory of a traveling charged particle beam should be along the spatial grid. In the presented method, an arbitrary beam trajectory can be treated since the beam current is not placed on the spatial grid but is considered as an incident field source. Wake potentials of …a simple system with a slightly angled beam trajectory are calculated for a demonstration. Show more

DOI: 10.3233/JAE-2002-370

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 243-247, 2002

Authors: Krassilnikov, Mikhail | Novokhatski, Alexandre | Weiland, Thomas

Article Type: Research Article

Abstract: V-Code, based on the Ensemble Model [1], was elaborated as fast and efficient tool for the beam dynamics simulation. The Ensemble Model equations are derived from Vlasov equation and involve the second order moments of the distribution function. The structure of accelerators and the features of the Ensemble Model determine the choice of the object-oriented approach for the code elaboration. Such approach gives an essential advantage in further extension, as the code can be improved continuously …by introducing new element classes. The Ensemble Model is valid for any energy range and the V-Code can simulate the entire accelerator. The present beam line database has been developed for the TESLA Test Facility (TTF DESY) accelerator component description. The results of the beam dynamics on-line simulation for TTF injector are presented. Show more

DOI: 10.3233/JAE-2002-494

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 249-253, 2002

Authors: Kotaki, Hideyuki | Kando, Masaki | Hosokai, Tomonao | Kondo, Shuji | Masuda, Shinichi | Kanazawa, Shuhei | Yokoyama, Takashi | Matoba, Toru | Nakajima, Kazuhisa

Article Type: Research Article

Abstract: Laser wakefield acceleration (LWFA) experiment using 100TW laser is planned at JAERI-Kansai. High quality short pulse electron beams and the precise electron-laser synchronization are necessary to accelerate the electron beam by the laser. A microtron with a photocathode rf-gun was developed as a high quality electron injector. The quantum efficiency(QE) of the photocathode was measured to be 2 × 10^{-5} . Emittance and a pulse width of the electron beams were 6π mm-mrad and 10ps, …respectively. In order to produce a short pulse electron beam, and to synchronize between the electron beam and the laser pulse, the inverse free electron laser (IFEL) is planed. A gas jet was set up and a density of the gas was measured by Mach-Zehnder interferometer. In order to overcome a short acceleration length of the LWFA, the Z-pinch plasma waveguide has been developed for 1 GeV laser wakefield acceleration. Show more

DOI: 10.3233/JAE-2002-383

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 255-262, 2002

Authors: Koyama, Kazuyoshi | Hazama, Hisanao | Saito, Naoaki | Tanimoto, Mitsumori

Article Type: Research Article

Abstract: Self-focusing of the intense laser pulses as well as production of the well-collimated electron beams in the moderately underdense plasma of n_{e}/n_{c} ≥ 10% 7 ×10^{17} W/cm^{2} . Progresses of a relativistic self-focusing in the plasma of a gaussian density profile were observed by an ultra-fast optical probing. Even if the large gas-target of the quasi-uniform density was used, the self-focusing was terminated after traveling approximately 1.2 mm by …the abrupt transition of the propagation mode from the smooth channeling to the complex filamentation, which correlated with the emission of MeV-electron beams. High-energy electron beams have the power-law spectrum of E^{-3.5} reaching the maximum energy of 2 MeV. The maximum number of the electrons was (1.3 ± 0.6) × 10^{11} /sr/shot. Model calculations suggest that the most plausible mechanism of the production of high-energy electron beam in the moderately underdense plasma is that the phase of the electron oscillation in filaments of the laser beam randomly changes many times. Show more

DOI: 10.3233/JAE-2002-377

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 263-269, 2002

Authors: Hafz, Nasr A.M. | Hemker, R. | Zhidkov, A. | Okuda, H. | Ghaly, W. | Kinoshita, K. | Hosokai, T. | Yoshii, K. | Ueda, T. | Watanabe, T. | Uesaka, M.

Article Type: Research Article

Abstract: The generation of an ultrashort relativistic electron bunch from a strong laser-plasma interaction have been studied by particle-in-cell simulations and observed experimentally. The electron beam was generated from the plasma created by focusing 12 TW (tera watt) laser pulse at the edge of helium gas jet expanded into the vacuum from a pulsed supersonic nozzle. The laser pulse duration was 50~fs (femtosecond). In the interaction of 50 fs, 12 TW laser pulse with plasma of density …of 5 × 10^{19} cm^{-3} , the electron generation was observed in the simulation at the very beginning of the interaction region. The plasma electrons were gaining higher energies by the huge longitudinal electric fields (created by the laser pulse) as they move through the rest of the plasma following the laser pulse. In the experiment, the electron beam transverse profile and its total charge have been measured in the forward direction (the same direction of the laser pulse) by using imaging plate and Faraday-cup, respectively. Show more

DOI: 10.3233/JAE-2002-379

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 271-276, 2002

Authors: Namba, Shinichi | Kawachi, Tetsuya | Hasegawa, Noboru | Nagashima, Keisuke | Sukegawa, Kouta | Kado, Masataka | Tanaka, Momoko | Daido, Hiroyuki | Kato, Yoshiaki

Article Type: Research Article

Abstract: High-density nitrogen gas was irradiated with an ultrashort high-intensity pulse laser (pulse width: 1.5 ps, intensity: ≥ 10^{15} W/cm^{2} ). It was found that highly charged ions were produced effectively as the gas density became higher. From distribution of population densities of high-lying levels of lithium like nitrogen ions, the electron temperature in a recombining phase was estimated. This electron temperature together with a calculation using a collisional-radiative model, …in which doubly excited levels of beryllium like ions are included, indicated that the electron density was n_{e} = 3 × 10^{19} cm^{-3} . Moreover, the spectra also showed that population inversions between some excited states of hydrogen-, helium-, lithium like nitrogen ions were generated under this plasma conditions. Show more

DOI: 10.3233/JAE-2002-384

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 277-282, 2002

Authors: Ito, Kiyokazu | Ogata, Atsushi | Okamoto, Hiromi

Article Type: Research Article

Abstract: We describe a possible accelerator system to provide an ion beam of extremely low emittance and low current. It is possible to reduce the beam size down to nanometer order keeping the beam divergence of microradian order. It can be used as a nano beam source for single ion implantation onto semiconductors and for the systematic study of radiation damage in bio-molecules and semiconductors. The whole system basically has a radio-frequency quadrupole configuration with a Paul …ion trap as injector. Ions are confined and cooled in the trap section, and then accelerated to ∼ MeV through an RFQ linac. Design speculation is made assuming acceleration of ^7 Li^+ ions. Show more

DOI: 10.3233/JAE-2002-378

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 283-287, 2002

Authors: Nakamura, S. | Morita, A. | Iwashita, Y. | Shirai, T. | Noda, A. | Daido, H. | Kato, Y.

Article Type: Research Article

Abstract: A phase rotation scheme is investigated for the ion beam that is emitted from foil target irradiated by a high power (100 TW) short-pulse (20 fs) laser. By application of an RF electric field synchronized with the laser pulse, the ion beams in the energy range of ± 5% our goal. Assumed parameters are 144 MHz for RF frequency and 280 kV RF amplitude for C^{6+} with center energy of 2 MeV/u using ± …π/4 RF phase range. We think that a quarter wave resonator with double-gaps is a good candidate for the RF-cavity. The gap length is 2 cm. Show more

DOI: 10.3233/JAE-2002-382

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 289-294, 2002

Authors: Rizawa, Takahito | Tamura, Hitoshi | Sato, Kenji

Article Type: Research Article

Abstract: A new concept of a tuning free cavity for an ion synchrotron is described, which is based on an idea of applying an all-pass network to a ferrite LC resonator. Though the new type cavity has a smaller and simpler structure than bias-tuned one, it can produce comparably high RF voltage and a wide frequency range. After high power tests of newly developed ferrite materials and a proto-type cavity proved the concept practicable, beam acceleration tests …were performed at HIMAC successfully. The course of developing the cavity is described with its unique merits and further applicability. Show more

DOI: 10.3233/JAE-2002-517

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 295-300, 2002

Authors: Fadil, H. | Shirai, T. | Iwashita, Y. | Noda, A. | Noda, K. | Beutelspacher, M.

Article Type: Research Article

Abstract: We investigate a scheme for electron cooling of ion beams with large momentum spread of ± (1%) accelerator (IndAcc) is utilized to accelerate or decelerate the stored ion beam in order to shift its momentum distribution toward the sensitive region of the electron cooling force. This method will be applied for further cooling of phase rotated hot ion beams produced by a high-power short pulse laser, to be used as an injection beam for synchrotron. Also, …an induction accelerator has been designed for construction at the HIMAC ring, which will be used to test the feasibility of the present sweep scheme experimentally. Show more

DOI: 10.3233/JAE-2002-381

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 14, no. 1-4, pp. 301-306, 2002