Beam Dynamics and Electromagnetic Fields




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НазваниеBeam Dynamics and Electromagnetic Fields
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Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


586 - Luminosity and Energy Resolution in e+e- Colliding Rings
S. Petracca, University of Sannio, Benevento; K. Hirata, The Graduate University for Advanced Studies, Hayama

Luminosity is one of the key concepts for accelerator design. When the design target is a narrow energy peak, the collision energy resolution becomes more relevant. In this paper we give a fairly accurate expressions for luminosity and energy resolution based on the Gaussian approximation of the beam distribution functions[1]. All kind of couplings are considered.

Work sponsored in part by INFN and by EC through a grant to S.P.

[1] S.Petracca and K. Hirata, Jpn. J. Appl. Phys. 2001, vol. 40,p.5123-5129.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


973 - Small Isochronous Ring Project at NSCL*
E. Pozdeyev, F. Marti, J.A. Rodriguez, R.C. York, NSCL, East Lansing

The Small Isochronous Ring (SIR) is under development at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). The main objective of the project is the experimental study of space charge effects in the isochronous regime. The ring is a small-scale experiment that requires low beam intensities to simulate the dynamics of intense beams in large-scale accelerators. The important issues to be addressed by the ring are the space charge induced vortex motion specific to the isochronous regime, the longitudinal break-up of long bunches, formation of the self-consistent stable charge distribution by short bunches, and formation of weak beam tails and beam halo. This paper reports the status of the project and describes the design of major ring systems.

* Work supported by the NSF Grant # PHY 0110253 and the US Department of Energy Contract # DE-FG02-99ER41118

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


975 - Computer Simulations of the Beam Dynamics in the Small Isochronous Ring*
E. Pozdeyev, J.A. Rodriguez, NSCL, East Lansing

A Small Isochronous Ring (SIR), whose main objective is the experimental study of the space charge effects in the isochronous regime, is under development at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). To study the beam dynamics in the ring we tracked particle trajectories in a realistic magnetic field generated by TOSCA. The single-particle tracking shows that the horizontal and vertical dynamic apertures of the ring are 8 cm and 5 cm respectively at the injection energy. With the inclusion of an energy spread of +-5%, the dynamic aperture is still greater than 4 cm. To simulate the multi-particle beam dynamics in the ring, we have developed a three-dimensional PIC code that accurately calculates particle trajectories in a specified magnetic field. A field solver based on Fast Fourier Transformations calculates the space charge field of the beam. Multi-particle simulations show that the energy spread within a bunch circulating in the ring grows from 0 to +-3% in 20 turns. In addition, the bunch breaks into a set of small round clusters. Detailed investigation reveals that particles within each cluster are involved in a vortex motion induced by the space charge force.

* Work supported by the NSF Grant No. PHY 0110253

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


967 - Injection Line of the Small Isochronous Ring*
J.A. Rodriguez, F. Marti, E. Pozdeyev, NSCL, East Lansing

The Small Isochronous Ring (SIR), under development at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU), is a ring whose main purpose is the study of longitudinal space charge effects [1]. This paper describes the SIR injection line. Descriptions of the ion source, einzel lenses, bending magnet, diagnostics, chopper, and ring injection inflector plates are given. Single particle beam dynamics simulations performed using SIMION and TOSCA are detailed. Experimental results are provided and compared to simulations.

*Work supported by NSF Grant # PHY-0110253 and U.S. Department of Energy Contract # DE-FG02-99ER41118

[1] E. Pozdeyev et al, Small Isochronous Ring Project at NSCL, these proceedings

Type of presentation requested : Poster

Speaker :
Dr. E. Pozdeyev

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1366 - Simulation Study of Beam Compression by Barrier Bucket for ACR at RIKEN MUSES
A. Sakumi, RIKEN, Saitama; T. Katayama, T. Takeuchi, CNS, Saitama; P. Zenkevitch, ITEP, Moscow

MUSES-ACR is designed to make accumulated and cooled beam for not only the radioactive isotope ion beams, but also intense primary ion beams. We proposed the barrier bucket method as a beam bunching system in ACR. We calculated the dynamics of the accumulating beam in the ACR are compressed by barrier bucket.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


926 - Beam Dynamics Design of a Superconducting 175 MHz CH-Linac for IFMIF
A. Sauer, H. Deitinghoff, H. Klein, U. Ratzinger, R. Tiede, IAP, Frankfurt-am-Main; R. Eichhorn, GSI, Darmstadt

In the IFMIF project the generation of a 125 mA, 40 MeV D+ beam is required to produce very high neutron fluxes from a liquid Li target to test possible wall materials for inertial fusion chambers. The linac design consists of a RFQ accelerator as first part (0.100 - 5 MeV) followed by a drift tube linac from 5 to 40 MeV. The required cw operation favours a superconducting approach with shorter length, high efficiency and larger aperture, which gives a higher safety margin against possible particle losses and resulting structure activation. One well suited candidate may be the CH-structure, which combines high acceleration efficiency with comparatively small geometrical dimensions. In a first attempt a beam dynamics design have been studied: a combination of a normal-conducting IH-cavity followed by a superconducting 175 MHz CH-section, which fulfills all IFMIF requirements. The DTL length is about 10 m only. Results of multiparticle simulations show very good beam behaviour and will be presented and discussed together with the main structure parameters.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1779 - Kinetic Theory of Periodic Holes in Debunched Particle Beams*
H. Schamel, J.-M. Griessmeier, University of Bayreuth, Bayreuth; R. Fedele, Universita Federico II and INFN, Napoli

A self-consistent theory of periodic hole structures in coasting beams in synchrotrons and storage rings is presented, extending the theory on localized holes. The analysis reveals new intrinsic nonlinear modes which owe their existence to a deficiency of particles trapped in the self-sustained potential well, showing up as notches in the thermal range of the distribution function. It is hence the full set of Vlasov-Poisson equations which is invoked; linearized treatments as well their nonlinear extensions fundamentally fail to cope with this strongly nonthermodynamic phenomenon. Qualitative agreement [1] with the holes recently found at the CERN Proton Synchrotron Booster [2] is shown.

* This work is supported by DAAD (Deutscher Akademischer Austauschdienst) and CRUI (Conferenza dei Rettori delle Universita Italiane) within the research program "Vigoni" between the University of Bayreuth and the University Federico II of Napoli.

[1] To appear in Phys. Rev. ST Accel. Beams (2002)

[2] S. Koscielniak, S. Hancock and M. Lindroos, Phys. Rev. ST Accel. Beams 4,044201 (2001)

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1223 - An Electron Cooler Design for the S-ring at NIRS
S. Shibuya, K. Noda, S. Yamada, NIRS, Chiba City; E. Syresin, JINR, Dubna, Moscow Region; T. Tachikawa, Sumitomo Heavy Industries, LTD.

A small synchrotron project for heavy ions has been started at NIRS. The small synchrotron (S-ring), whose circumference is less than 25-m has been designed to supply heavy-ion beams with a charge to mass ratio of 1/2 ranging of energy from 1 to 28-MeV/n. The project will be presented in this conference*. In this synchrotron, an electron cooler is installed to be able to deliver a low emittance beam at any energy range, a high intensity beam using cooling and stacking technique, and deliver a short-bunched beam using cooling and phase rotation technique. The cooler consists of two toloid magnets with a radius of 650-mm, a main solenoid magnet with a length of 900-mm, an electron gun with high perveance, and highly efficient collector system. A magnetic field of the main solenoid is 0.05-T, and the maximum expansion ratio is around 10. A design of the cooler are presented.

* K.Noda et.al, "S-ring project at NIRS", this conference.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1038 - Hamiltonian Dynamics of Intense Beams in a Nonlinear Focusing Channel
K. Sonnad, J. Cary, CIPS, Boulder

The continuous focusing model for high intensity beams shows that nonlinear terms in the external focusing induce damping of the envelope oscillations. We propose that this could be applied to reduce beam halos. We then derive a Hamiltonian that is averaged over a lattice period for an intense beam under the influence of quadrapole and octupole focusing terms. This analysis is for a thin, unbunched beam and assumes that the lattice period is much smaller than the period of the envelope oscillation. This averaging procedure reduces the computation time by eliminating the rapid time scale from the problem, while retaining the essential physics.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1093 - Cure for a Transverse Instability during Electron-Cooling Bunching
M. Takanaka, RIKEN, Saitama

We have studied characteristics of electron-cooled bunched ion beams using a multiparticle tracking simulation. During electron-cooling bunching, the beams become space-charge dominated and meet a transverse instability of which the source is the toroid field at the electron-cooling section. We check if a set of skew quadrupole magnets are an effective cure for the instability.

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1102 - Halo-formation and beam loss in the 3GeV Ring of the Joint Project
K. Takayama, T. Adachi, S. Igarashi, S. Machida, Y. Shimosaki, M. Shirakata, KEK, Ibaraki-ken; F. Noda, T. Shigaki, JAERI, Tokai; N. Tani, SOKENDAI, Tsukuba

A systematic study on the halo-formation predicted in the 3GeV Booster Ring for the Joint Project has been performed. Orbits of interacting particles are examined by utilizing three independently developed computer codes of ACCSIM, SIMPSONS, and PATRASH. Self-fields, higher multipole fields in the lattice magnets as well as sextupole fields for chromaticity correction are included in the tracking simulations. For a typical example, driving mechanisms of halo-formation are manifested. Absolute sizes of the halo are given as a function of the beam intensity for a set of possible machine parameters. The size tells us an achievable beam intensity under the best machine-condition, which would allow hands-on-maintenance.

Type of presentation requested : Poster

Speaker :
Dr. Susumu Igarashi

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


1609 - Comparison between the Predictions and Mmeasurements for the Beam Gas Interactions during the Last Gold and Proton Runs in RHIC
D. Trbojevic, W. Fischer, H.-C. Hseuh, W.W. MacKay, S.Y. Zhang, BNL, Upton, Long Island, New York

The last gold-gold and polarized proton-proton collision runs were performed at energies of 100 GeV/nucleon. The beam gas interactions in RHIC are very important for the beam lifetime in RHIC. This is a report where the pressure data differences between the beams on and beams off at injection and at the 100 GeV/nucleon energy are compared with predictions for the beam gas interaction and beam lifetime for both gold and proton beams.

[1] work supported under auspices of the U.S. Department of Energy

Type of presentation requested : Poster

Classification : [D03] High Intensity - Incoherent Instabilities, Space Charge, Halos, Cooling


977 - A High-Intensity Highly-Polarized Electron Beam for High-Energy Physics*
J.L. Turner, A. Brachmann, J.E. Clendenin, F.-J. Decker, D.-A. Luh, T. Maruyama, M.B. Woods, SLAC, Stanford

A new high-energy parity violation (PV) experiment at SLAC as well as particle-physics experiments using future e+e- colliders (such as NLC) operating at energies above the scale of unification of the electromagnetic and weak interactions require a highly-polarized electron beam with intensity requirements previously unachievable due to a surface charge limit effect at the cathode of the polarized electron source. Using a GaAs(0.95)P(0.05)/GaAs(0.66)P(0.34) single-layer photocathode with high surface doping that was recently developed at SLAC as part of the NLC R&D effort [1], a beam with >2x10^12 e- per 100 ns of pulse length (and up to 3 A/cm^2) has been produced at the electron source of the SLAC 3-km linac, limited only by the available laser energy. This is considerably more charge per unit pulse length than required for the NLC macropulse. The polarization measured in the laboratory is ~80%. The present PV experiment (E-158) at SLAC requires 8x10^11 e- in a 370 ns pulse (350 mA). Consequently there is sufficient head room to shape the pulse temporal profile to allow the necessary energy compensation for the linac beam loading to limit the energy spread at 48.7 GeV to ~0.3% rms. The intensity stability required for stable machine operation is determined by the source laser stability. After recent improvements [2], the SLAC-built flashlamp-pumped Ti:sapphire laser now has an energy stability of ~1% rms. Temporal pulse shaping is performed on the laser beam using an improved pulse shaper. Details of the beam generation, energy compensation, and linac performance recently achieved for E-158 will be discussed.

*Work supported by Department of Energy contract DE-AC03-76SF00515.

[1] T. Maruyama et al., "Overcoming the surface-charge-limit using high-gradient-doped strained photocathodes," to be submitted for publication.

[2] R. Alley et al., "SLAC's polarized electron source laser system for the E-158 parity violation experiment," to be submitted for publication.
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