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octupole

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TUOBG02 Study of Beam Dynamics During the Crossing of Resonances in the VEPP-4M Storage Ring resonance, emittance, collider, betatron 965
 
  • P. A. Piminov, V. A. Kiselev, E. B. Levichev, O. I. Meshkov, S. A. Nikitin
    BINP SB RAS, Novosibirsk
  The influence of resonances on the beam dynamics in the storage rings is of a substantial interest for the accelerator physics. For example, a fast crossing of resonances occurs in the damping rings of future linear colliders during the beam damping due to the coherent shift that can result in a loss of particles. We have studied experimentally the crossing of resonances of different power nearby the working point of the VEPP-4M storage ring. The observation of the beam sizes and particle losses has been done with a single-turn time resolution. The comparison with the numerical simulation has been made.  
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TUPP035 Analysis of Intensity Instability Threshold at Transition in RHIC impedance, emittance, electron, coupling 1616
 
  • W. Fischer, I. Blackler, M. Blaskiewicz, P. Cameron, C. Montag, V. Ptitsyn, T. Roser
    BNL, Upton, Long Island, New York
  The beam intensity of ion beams in RHIC is limited by a fast transverse instability at transition, driven by the machine impedance and electron clouds. For gold and deuteron beams we analyze the dependence of the instability threshold on beam and machine parameters from recent operational data and dedicated experiments. We fit the machine impedance to the experimental data.  
 
WEPC153 Dipole Magnet for Use of RHIC EBIS HEBT Line multipole, dipole, sextupole, quadrupole 2365
 
  • T. Kanesue
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
  • M. Okamura, D. Raparia, J. Ritter
    BNL, Upton, Long Island, New York
  We present the design optimization of a dipole magnet for use of RHIC EBIS HEBT line. This magnet provides a total bending angle of 145 degrees by two identical magnets and it is used to guide H+ to Au32+ beam with energy of 2 MeV/amu. Magnetic field is required to change within 1 second corresponding to the ion species, so magnet body has the laminated structure to suppress eddy current. Effective length and field quality within a radius of 5 cm was optimized separately. Effective length was optimized by adjusting end shape not to change the beam orbit between low and high field operation more than 1 mm from intended beam orbit after bending. Then field quality was optimized by changing the shim position and additional bump. After modification, all multipole coefficients along the beam trajectory were reduced to within 10x10-4.  
 
WEPC154 Design and Fabrication of Multipole Corrector Magnet controls, power-supply, multipole, quadrupole 2368
 
  • F.-Y. Lin, C.-H. Chang, H.-H. Chen, C.-S. Hwang, C. Y. Kuo
    NSRRC, Hsinchu
  The Taiwan Light Source (TLS) had started to operate in top-up mode injection since October 2005. Meanwhile, the Elliptically Polarized Undulator (EPU5.6) was operated very well in the decay mode operation. However, the partial beam loss had occurred when the top-up injection was executed at magnet gap and magnet array phase are fixed at the minimum gap and π(vertical polarization mode), respectively. In order to solve the partial beam loss, we design a new multipole corrector magnet to be installed in the downstream of the EPU5.6 to compensate for the multipole field error. This multipole magnet can provide the normal and skew components of the dipole, quadrupole, sextupole, octople, and dodecapole field components. Changeable multipole field components mechanism has been designed by using a special electric circuit. In addition, the measurement systems of Hall probe and stretch wire are used to measure the field quality of the multipole corrector magnet. This report will discuss the magnet circuit design, mechanical design, the switching mechanism of the multipole field components, and the field measurement results.  
 
WEPP060 Abort Gap Cleaning Using the Transverse Feedback System: Simulation and Measurements in the SPS for the LHC Beam Dump System simulation, kicker, feedback, proton 2656
 
  • A. Koschik, B. Goddard, W. Höfle, G. Kotzian, D. K. Kramer, T. Kramer
    CERN, Geneva
  The critical and delicate process of dumping the beams of the LHC requires very low particle densities within the 3 microseconds of the dump kicker rising edge. High beam population in this so-called 'abort gap' might cause magnet quenches or even damage. Constant refilling due to diffusion processes is expected which will be counter-acted by an active abort gap cleaning system employing the transverse feedback kickers. In order to assess the feasibility and performance of such an abort gap cleaning system, simulations and measurements with beam in the SPS have been performed. Here we report on the results of these studies.  
 
WEPP156 Spherical Aberrations-free Wiggler wiggler, sextupole, quadrupole, multipole 2853
 
  • A. A. Mikhailichenko
    Cornell University, Department of Physics, Ithaca, New York
  We represented details of design of a wiggler with linear piecewise longitudinal field dependence. This type of field distribution eliminates spherical aberrations in wiggler. This wiggler can be recommended for usage in cooler rings including ILC ones.  
 
THPC002 Synthesis of Optimal Nanoprobe (Nonlinear Approximation) focusing, quadrupole, controls, multipole 2972
 
  • S. N. Andrianov, N. S. Edamenko, Yu. V. Tereshonkov
    St. Petersburg State University, Applied Mathematics & Control Processes Faculty, St. Petersburg
  This paper is a continuation of the paper devoted to synthesis of optimal nanoprobe in linear approximation. Here the main goal is the optimization of nanoprobe including nonlinear aberrations of different nature up to third order. The matrix formalism for Lie algebraic methods is used to account for nonlinear aberrations. This method gives a possibility to consider nonlinear effects separately. Here we mean that a researcher can start or remove different kind of nonlinearities. This problem is separated into several parts. On the first step, we consider possibilities of additional optimization for some structures, selected on the step of linear approximation. The most of aberrations have harmful character, and their effect must be maximally decreased. Therefore, on the next steps, some we use analytical and numerical methods for generation of nonlinear corrected elements. The matrix formalism allows reducing the correction procedure to linear algebraic equations for aberration coefficients. Some examples of corresponding results are given.  
 
THPC045 Beam Uniformization System Using Multipole Magnets at the JAEA AVF Cyclotron multipole, target, cyclotron, sextupole 3077
 
  • Y. Yuri, T. Agematsu, I. Ishibori, T. Ishizaka, H. Kashiwagi, S. Kurashima, N. Miyawaki, T. Nara, S. Okumura, K. Yoshida, T. Yuyama
    JAEA/ARTC, Takasaki
  It has been known that uniformization of a beam with a Gaussian profile is possible utilizing odd-order nonlinear forces*. Here, we investigate uniformization of the transverse beam profile using nonlinear-focusing forces produced by multipole magnets in detail. We show that it is possible to uniformize an asymmetric beam as well as a Gaussian beam utilizing the odd and even-order nonlinear forces in combination**. It enables us to perform high-uniformity irradiation at a constant particle fluence rate over the whole area of a large target. A research and development study of the beam uniformization system composed of sextupole and octupole magnets is now in progress at the JAEA AVF cyclotron facility. Some results of preliminary experiments on beam uniformization are also reported.

*P. F. Meads, Jr., IEEE Trans. Nucl. Sci. 30, 2838 (1983).
**Y. Yuri et al., Phys. Rev. ST Accel. Beams 10, 104001 (2007).

 
 
THPC049 Progress in the Beam Preparation for the Multi-turn Extraction at the CERN Proton Synchrotron extraction, sextupole, proton, resonance 3089
 
  • S. S. Gilardoni, F. Franchi, M. Giovannozzi
    CERN, Geneva
  A new type of extraction based on beam trapping inside stable islands in the horizontal phase space will become operational during 2008 at the CERN Proton Synchrotron. A series of beam experiments was carried out to prove loss-less capture with high intensity and multi-bunched beams, up to 1500·1010 protons per pulse, in preparation of the extraction commissioning. These fundamental steps for the new Multi-turn Extraction are presented and discussed in details.  
 
THPC050 Experimental Evidence of Beam Trapping with One-third and One-fifth Resonance Crossing resonance, proton, sextupole, synchrotron 3092
 
  • S. S. Gilardoni, F. Franchi, M. Giovannozzi
    CERN, Geneva
  Beam trapping in stable islands of the horizontal phase space generated by non-linear magnetic fields is realized by means of a given tune variation so to cross a resonance of order n. Whenever the resonance is stable, n+1 beamlets are created whereas if the resonance is unstable, the beam is split in n parts. Experiments at the CERN Proton Synchrotron showed protons trapped in stable islands while crossing the one-third and one-fifth resonance with the creation of 3 and 6 stable beamlets, respectively. The results are presented and discussed in details.  
 
THPC077 Transportation Channel with Uniform Electron Distribution for the Kharkov Neutron Source based on Subcritical Assembly Driven with Linear Accelerator target, electron, focusing, quadrupole 3164
 
  • A. Y. Zelinsky, I. M. Karnaukhov
    NSC/KIPT, Kharkov
  Electron beam transportation channel from linear accelerator to the neutron target of NSC KIPT neutron source should provide uniform distribution of electrons on target surface to prevent overheating of the target and reduce thermal stress. In the presented channel the method of uniform beam distribution formation with linear focusing elements and nonlinear focusing elements (octupole magnets) we used. Linear focusing elements were used to provide particle transportation through the channel without losses and to form required beam sizes at the target. Nonlinear focusing elements were used to modulate transverse velocity of peripheral particles. As a result the uniform electron beam of rectangular shape can be formed at the target. In the report the main principles of transportation channel design and results of calculations for NSC KIPT neutron source based on subcritical assembly driven by electron accelerator are presented. Lattice and parameters of focusing elements are presented. Calculation results show that proposed transportation channel lattice can provide uniform beam of rectangular shape with sizes 66x66 mm.  
 
THPC083 Simulation Studies of Space-charge Effects in the LENS Nonlinear Transport Lines space-charge, simulation, target, focusing 3179
 
  • M. Hess, A. Bogdanov
    IUCF, Bloomington, Indiana
  The upgraded IUCF LENS beamline is designed to deliver a square shaped 13 MeV proton beam at 25 mA with a relatively uniform density using two octupole magnets for nonlinear focusing in both transverse directions. The space-charge effects in the LENS beamline (without nonlinear focusing) can vary the beam profile by roughly 8%-13% compared to a zero current beam. In this paper, we show the results of simulation studies of the LENS beamline which incorporate the effects of space-charge, as well as, nonlinear focusing from the octupole magnets. The simulations utilize self-consistent methods for computing the space-charge fields, since the beam density distribution can be nonlinear. We also show simulation results for beam currents in excess of 25 mA, which may be useful for future upgrades of LENS.  
 
THPP114 LHC Transverse Feedback Damping Efficiency feedback, damping, injection, simulation 3632
 
  • G. Kotzian, W. Höfle
    CERN, Geneva
  • E. Vogel
    DESY, Hamburg
  A simulation model has been developed to predict the damping efficiency of the LHC transverse feedback system in the presence of coupled bunch instabilities and under realistic assumptions for the injection error. The model tracks both the centre of gravity of a bunch and the r.m.s beam size during and after injection. It includes the frequency characteristic of the transverse feedback system. Nonlinearities in the beam optics will cause the bunches to filament and lead to an increase of the transverse emittance after injection. The resistive wall instability reduces the effectiveness of the transverse feedback by slowing down the damping process. Possibilities for enhancing the performance of the feedback system by signal processing schemes are outlined.