29018425
Three-dimensional theory of the small-signal high-gain free-electron laser including betatron oscillations.
We have developed a three-dimensional free-electron laser (FEL) theory in the small-signal high-gain regime based upon the Maxwell-Vlasov equations including the effects of the energy spread, the emittance, and the betatron oscillations of the electron beam. The radiation field is expressed in terms of the Green's function of the inhomogeneous wave equation and the distribution function of the electron beam. The distribution function is expanded in terms of a set of orthogonal functions determined by the unperturbed electron distributions. The coupled Maxwell-Vlasov equations are then reduced to a matrix equation, from which a dispersion relation for the eigenvalues is derived. The growth rate for the fundamental mode can be obtained for any initial beam distribution including the hollow-beam, the water-bag, and the Gaussian distribution. Comparisons of our numerical solutions with simulation results and with other analytical approaches show good agreements except for the one-dimensional limit. We present a handy interpolating formula for the FEL gain of a Gaussian beam, as a function of the scaled parameters, that can be used for a quick estimate of the gain. The present theory can be applied to the beam-conditioning case by a few modifications.
54858442
Beam-Beam Interaction in an Asymmetric Collider for B-Physics
This note is devoted to deriving the minimum criteria to achieve a symmetrical behavior of unequal energy beams in asymmetric colliders for B-physics. The computer simulation results suggest that at least the following quantities should be equalized in the two rings: beam-beam tune shift, cross-sectional area at the interaction point, damping decrement per turn, and betatron phase modulation due to synchrotron motion. 5 refs., 5 figs., 1 tab.
122811670
Beam commissioning and operation of the J-PARC main ring synchrotron
Tadashi Koseki1∗, Yoshitugu Arakaki1, Yong Ho Chin1, Keigo Hara1, Katsushi Hasegawa1, Yoshinori Hashimoto1, Yoichiro Hori1, Susumu Igarashi1, Koji Ishii1, Norihiko Kamikubota1, Takuro Kimura1, Kunio Koseki1, Kuanjyun Fan1, Chikashi Kubota1, Yuu Kuniyasu1, Yoshinori Kurimoto1, Seishu Lee1, Hiroshi Matsumoto1, Alexander Molodozhentsev1, Yuichi Morita1, Shigeru Murasugi1, Ryotaro Muto1, Fujio Naito1, Hidetoshi Nakagawa1, Shu Nakamura1, Kazuaki Niki1, Kazuhito Ohmi1, Chihiro Ohmori1, Masashi Okada1, Katsuya Okamura1, Takao Oogoe1, Kazufumi Ooya1, Kenichi Sato1, Yoichi Sato1, Yoshihiro Sato1, Kenichirou Satou1, Masayuki Shimamoto1, Masashi Shirakata1, Hirohiko Someya1, Takuya Sugimoto1, Junpei Takano1, Yasuhiro Takeda1, Yoichi Takiyama1, Masaki Tejima1, Makoto Toda1 Masahito Tomizawa1, Takeshi Toyama1, Masahiko Uota1, Shuei Yamada1, Noboru Yamamoto1, Eiichi Yanaoka1, Masahito Yoshii1, Hiroyuki Harada2, Shuichiro Hatakeyama2, Hideaki Hotchi2, Masahiro Nomura2, Alexander Schnase2, Taihei Shimada2, Fumihiko Tamura2, Masanobu Yamamoto2 and Tetsushi Shimogawa3
53953604
Electron Gun Simulation Using MAGIC
The electron gun plays an important role concerning klystron performance, especially for X-band klystrons with a small drift-tube diameter. This paper describes a new method for an electron-gun simulation by using MAGIC. MAGIC solves the Maxwell equations in the presence of charged particles on a time-domain. The results simulated by MAGIC are compared with those by EGUN and measured values. It reveals that the perveance is almost the same as the measured values, and that the current-density distribution and beam angle are almost the same as those of EGUN. Although it takes half days to simulate the gun, the simulation has the potential that a single code can enable one to simulate the whole structure of a klystron.
92319659
MOSES users' guide : MOde-coupling Single bunch instability in an Electron Storage ring
116485083
Design and Testing of the Horizontal Version of the Multi Beam Klystron for European XFEL Project
Toshiba Electron Tubes & Devices (TETD) has been developing 10-MW L-band Multi Beam Klystrons (MBKs) for the European XFEL project and future linear colliders. In order to allow horizontal installation in the XFEL tunnel, the horizontal version of MBK, MBK E3736H, has been designed, fabricated and tested. The MBK has six low-perveance beams operated at low voltage of less than 120 kV (for 10MW) and six ring-shaped cavities. After the successful acceptance testing at TETD in August 2007, the final acceptance test was carried out at DESY in February 2008. In the tests at DESY, the MBK achieved an output power of 10.1 MW at a beam voltage of 118.8 kV and at an RF pulse width of 1.5ms with an efficiency of 65.4%. The stability of the tube was verified by being operated continuously more than 24 hours above 10-MW output power. These tests demonstrated that MBK E3736H fulfilled all the requirements necessary as the RF power source of the XFEL linac.
39970530
Surface excitations of helium droplets.
32507985
Exact ground-state properties of SU(3) Hamiltonian lattice gauge theory.
21649370
Higher-order force gradient symplectic algorithms
We show that a recently discovered fourth order symplectic algorithm, which requires one evaluation of force gradient in addition to three evaluations of the force, when iterated to higher order, yielded algorithms that are far superior to similarly iterated higher order algorithms based on the standard Forest-Ruth algorithm. We gauge the accuracy of each algorithm by comparing the step-size independent error functions associated with energy conservation and the rotation of the Laplace-Runge-Lenz vector when solving a highly eccentric Kepler problem. For orders 6, 8, 10, and 12, the new algorithms are approximately a factor of 10(3), 10(4), 10(4), and 10(5) better.
27873762
Quadratic diffusion Monte Carlo algorithms for solving atomic many-body problems.
The diffusion Monte Carlo algorithm with and without importance sampling is analyzed in terms of the algorithm's underlying transfer matrix. The crucial role played by the Langevin algorithm in the importance-sampling process is made explicit and emphasized. The failure of existing second- order algorithms to converge quadratically for atomic many-body problems is shown to be caused by nonperturbative convergence errors due to the intrinsic inability of the Langevin algorithm to sample Slater orbitals. This failure can be simply circumvented by enforcing attractive cusp condi- tions on the trial function. Various new second-order diffusion Monte Carlo algorithms are sys- tematically derived and their quadratic convergence numerically verified in cases of He and H&. made explicit the crucial connection between the importance-sampling process and the Langevin algo- rithm. The failure of second-order DMC algorithms to converge quadratically is shown to be caused by nonper- turbative convergent errors due to the intrinsic inability of the Langevin algorithm to sample Slater orbitals, and has nothing to do with overshooting. I further show that, when computing the energy, this convergence failure can be averted by enforcing all attractive cusp conditions on the trial function. That this avoidance pro- cedure works as proposed is numerically demonstrated in the case of the helium atom and the hydrogen molecule. The paper is organized as follows. The perturbative analysis of the transfer matrix is outlined in Sec. II. In Sec. III, second-order Langevin algorithms are systemati- cally derived. These are then used in Sec. IV to generate corresponding DMC algorithms. In Sec. V, the failure of second-order DMC algorithms to converge quadratically is traced to the convergence failure of their underlying Langevin algorithms. After enforcing cusp conditions, quadratic convergences of the ground-state energies of He and H2 are demonstrated. In Sec. VI, the conver- gence behavior of the Langevin algorithm is studied in detail by Monte Carlo methods and by directly iterating the algorithms' integral equation. The fundamental mismatch between the Gaussian character of the algo- rithm and the exponential nature of the Slater orbital is shown to result in fractional power convergence errors that degrade the algorithm. Conclusions are summarized in Sec. VII. The present DMC calculations confirm the expectation that larger step sizes can be used with second-order algo- rithms. Moreover, they suggest the possibility that calcu- lations can be carried out at a reasonably large step size without the need of extrapolation. The efficiency of these new algorithms has been further verified in model nu- clei
43470878
Analytic wave functions for understanding the spectrum of the three-anyon problem.
We show that the low-lying spectrum of three noninteracting anyons in a harmonic potential can be qualitatively and quantitatively understood on the basis of a simple set of analytic wave functions. These wave functions are exact in both the boson and fermion limits and satisfy the anyon wave-function phase condition at all intermediate values of the statistical parameter 0<α<1. The resulting nonlinear spectrum agrees with those of exact numerical calculations to better than a few parts in a thousand