Beam Dynamics and Electromagnetic Fields




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НазваниеBeam Dynamics and Electromagnetic Fields
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Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


1700 - Beam Stabilization in the SLAC A-line Using a Skew Quadrupole*
M. Woodley, P. Bosted, F.-J. Decker, R. Erickson, M. Libby, M.B. Woods, SLAC, Stanford

The E158 experiment at SLAC is a precision measurement of the left-right asymmetry in Moller scattering at low Q**2 utilizing a high-current long-pulse polarized electron beam scattering off unpolarized electrons in a liquid hydrogen target. Tolerances on beam size and position/angle stability for E158 are extremely tight, but the electron beam is subject to intensity jitter, dispersion, and wakefield effects in the linac which tend to make it unstable. Horizontal emittance growth due to synchrotron radiation in the transport line from the linac to the target ("A-line") reduces the sensitivity of the horizontal beam parameters at the target to incoming changes, but instability in the vertical plane was observed during the E158 pilot run. A skew quadrupole recently installed in the A-line just upstream of the target will be used to couple the projected transverse emittances, increasing the vertical emittance of the beam and thereby reducing its sensitivity to incoming changes. Simulations of the use and effects of this skew quadrupole, along with measured beam performance data with and without the skew quadrupole, will be presented.

*Work supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.

Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


1328 - The Design of the Isochronous and Achromatic Charge-Stripping Sections for RIA"*"
X. Wu, D. Gorelov, T.L. Grimm, W. Hartung, F. Marti, H. Podlech, R.C. York, NSCL, East Lansing

The proposed Rare Isotope Accelerator (RIA) uses a superconducting, cw linac to accelerate light and heavy ions to final energies of 400 MeV/u or more with a beam power of 100 to 400 kW. To meet the beam power requirements, simultaneous acceleration of several charge states is proposed for the heavier ions. For example, for U238, two charge states of 28+ and 29+ would be accelerated to an energy of about 13 MeV/u where the beam would be stripped and collimated to retain five charge states (73+ to 77+). These five charge states would then be accelerated to an energy of approximately 83 MeV/u where the beam would again be stripped and collimated to retain three charge states (87+ to 89+) that would be accelerated to the final energy of 400MeV/u. The optics design and simulation results for the two isochronous and achromatic charge-stripping sections are presented.

"*" Work supported by Michigan State University and NSF PHY 0110253.

Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


1711 - An SVD Enhanced Fitting for e+/e- Storage Ring Linear Optics Verification and Correction
Y. Yan, Y. Cai, J. Irwin, M. Sullivan, SLAC, Stanford

We use an SVD-enhanced least square fitting method to fit the phase advances and the Green's functions (specified by the local transfer matrix components R12, R34, R32, and R14) calculated from the lattice model to the corresponding measurements from turn-by-turn Beam Position Monitor (BPM) buffered data of a storage ring using a model-independent analysis (MIA) technique. The fitting variables are: all of the storage-ring quadrupole strengths (both normal and skew) and sextupole feed-downs and all of the BPM gains and BPM cross-plane couplings. Once fitted, the storage ring linear optics is verified and the magnet strength corrections are obtained, which would potentially correct the real machine linear optics to be the same as that of the lattice model. Furthermore a magnet correction priority sequence in terms of effectiveness in correcting the real machine linear optics can be exercised in the computer before correcting the real accelerator. Results from PEP-II measurement will be presented.

Work supported by US DOE contract DE-AC03-76SF00515.

Type of presentation requested : Poster

Speaker :
Yiton Yan

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


216 - Scaling Relations for the Determination of Beam Optics Errors using Response Matrix Analysis
V. Ziemann, TSL, Uppsala

Quadrupole gradient errors can be very accurately determined by carefully analysing difference orbits and their deviations from computer-model predictions. This method was successfully applied in synchrotron radiation sources. In order to allow easy before-hand estimates for the application to other accelerators we determine scaling relations for achievable accuracies as a function of BPM resolution and used number of BPM and dipole correctors.

Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


217 - A Proposal to Measure the Duodecapole Component of the LHC Triplet Magnets using a Wobbling Method
V. Ziemann, TSL, Uppsala

Due to finite manufacturing tolerances the triplet quadrupoles used in the interaction regions of LHC will have non-vanishing multipole errors which need to be measured and corrected in order to guarantee sufficient dynamic aperture at collision energy. Here we discuss a method to measure the unwanted multipole components by oscillating a closed orbit bump in the interaction region and observing the orbit at pickups outside the bump. The beam's response will contain very weak signals at harmonic frequencies of the sinusoidal excitation. Even though the amplitude of the harmonic signal will be below the resolution of the position monitor system, it can be made visible by adding noise to the original pickup data and subsequent careful filtering and averaging. We use a simple computer model to simulate the oscillating bump that generates pickup signals and then analyze those in a sophisticated signal processing chain in order to retreive the magnitude of the unwanted multipole components.

Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


703 - Modelling Nonlinear Optics in the CERN SPS
F. Zimmermann, G. Arduini, P. Collier, CERN, Geneva; A. Faus-Golfe, IFIC, Valencia

Nonlinear fields arising from eddy currents in the vacuum chamber and remanent fields in the magnets of the CERN SPS vary with time and with the acceleration cycle. We describe a procedure of constructing a nonlinear optics model for the SPS, by considering sextupolar, octupolar, and decapolar field errors in the dipole and quadrupole magnets, respectively, whose strengths are adjusted so as to best reproduce the measured nonlinear chromaticities up to third order in the

momentum deviation. Applying this procedure to SPS chromaticity measurements taken at 26 GeV/c, we have obtained a refined optics model. The tune shifts with the transverse amplitude predicted by this model are consistent with a direct measurement.

Type of presentation requested : Poster

Speaker :
Dr. Angeles Faus-Golfe

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


1418 - Beam Based Machine Modelling for Orbit Control and Feedback
D. Zimoch, M. Grewe, G. Schmidt, T. Weis, K. Wille, DELTA, Dortmund

The 1.5 GeV electron storage ring Delta uses quadrupole magnets with integrated sextupoles and steerers to obtain a compact lattice. However, saturation and hysteresis effects result in nonlinear interactions between the magnet components. Therefore, optic models have so far failed to reproduce the observed optics with the required precision. We thus used beam based methods to obtain a heuristic machine model. Beam based calibration has been used to measure offsets between the signal centers of the beam position monitors and the magnetic centers of their close-by quadrupoles. Measured response matrices are used as basis for orbit feedback and local orbit bumps. These steps have significantly improved machine stability and reliability.

Type of presentation requested : Poster

Classification : [D01] Beam Optics - Lattices, Correction Schemes, Transport


1052 - Study of Acceptance of FFAG Accelerator
M. Aiba, T. Adachi, S. Machida, Y. Mori, A. Mutoh, J. Nakano, C. Ohmori, I. Sakai, Y. Sato, M. Sugaya, A. Takagi, R. Ueno, T. Uesugi, T. Yokoi, Y. Yonemura, M. Yoshii, M. Yoshimoto, Y. Yuasa, KEK, Ibaraki-ken; K. Koba, FNAL, Batavia

The horizontal acceptance of radial sector Fixed Field Alternating Gradient (FFAG) accelerator is evaluated analytically and with particle tracking with its applications to phase rotation and acceleration of secondary particles in mind. In those machines, it is essential to accommodate beams with huge momentum as well as large transverse emittance although the number of revolution are limited, typically 10 turns or so. FFAG focusing structure has zero chromaticity, in other words, betatron tunes are independent of momentum in all momentum range. On the other hand, it introduces strong nonlinearity, therefore betatoron tunes have the amplitude dependence and linearized model easily fails. We first perform particle tracking and obtain the horizontal acceptance of the order of 10E4 pi mm-mrad when the machine parameters are optimized. Then the effects of isolated resonance and its amplitude dependent tune shift are analyzed taking phase per cell as a parameter. We will show systematic results in machine parameter space and give generalized design priciple.

Type of presentation requested : Poster

Classification : [D02] Non-linear Dynamics - Resonances, Tracking, Higher Order


1537 - Application of the Frequency Map Aanalysis to the New Lattice of SOLEIL Project*.
M. Belgroune, P. Brunelle, A. Nadji, SOLEIL, Orsay; J. Laskar, IMCCE, Paris

The SOLEIL lattice has been modified in order to increase the number of straight sections for Insertion Devices. The linear and non-linear optics have been optimised and satisfy as good results as in the APD study. A deep investigation of the dynamics was performed for several working points using the frequency map analysis. This technique enables a better understanding of the non-linear beam dynamics and the inner complexe structure of the dynamic aperture which is essential to choose the best working point.

* Work supported by Synchrotron SOLEIL

Type of presentation requested : Poster

Classification : [D02] Non-linear Dynamics - Resonances, Tracking, Higher Order


1546 - Non-linear Transverse Beam Dynamics Studies in the Super-ACO Storage Ring*
M. Belgroune, P. Brunelle, A. Nadji, SOLEIL, Orsay; L. Nadolski, ALS, Berkeley

Experimental turn by turn beam position measurements were performed in order to investigate the non-linear transverse beam dynamics in the Super-ACO storage ring. The aim of these experiments is to understand the aperture limiting effects of non-linearities and to complete the model used in tracking studies. The two aspects of non-linear beam behavior described here are the amplitude-dependent tune shift and the phase space trajectories near and far from resonances. This work was carried out with open and closed undulators for on and off-momentum particles. The effects of a strong octupolar-like component due to quadrupoles fringe field missing in the model will be highlighted. We will also show an analysis which enables to make the distinction between a physical and a dynamic aperture limitation.

* Work supported by Synchrotron SOLEIL

Type of presentation requested : Poster

Classification : [D02] Non-linear Dynamics - Resonances, Tracking, Higher Order


372 - Separatrix Formalizm in Super-conducting Linac Design
A. Bogdanov, R. Maier, Y. Senichev, FZJ, Jülich

Under design of the linear accelerator we use the accelerating systems with external synchronizing of the different groups of structures with few number of similar gaps. The equivalent phase velocity is constant along each structure and it is changed by step from cavity to cavity. The particles are sliding down or up relatively of RF wave in dependence on the ratio between the particles and the wave velocities. Thus, the particles are never in synchronism with the equivalent traveling wave, and even some time they have not instantaneous longitudinal stability. But due to a proper choice of the RF phase shift DjRF between the cavities we can create a quasi-synchronous motion, and in total we have a stable motion in the whole accelerator. Such structures are used for the acceleration of particles with different masses from the low energy and in the high-energy proton linear accelerators. These structures are cheaper, since they have the simpler cavity geometry. However, due to the bigger phase oscillation the particles are appeared in the nonlinear part of the separatrix, which one causes the growth of the longitudinal emittance. We developed the separatrix formalism for the optimized design of such linear accelerators.

Type of presentation requested : Poster

Classification : [D02] Non-linear Dynamics - Resonances, Tracking, Higher Order


1337 - Simulations and Measurements of Machine Background at DAFNE
M. Boscolo, S. Guiducci, INFN-LNF, Frascati (Roma)

DAFNE background is dominated by Touschek scattering. Studies have been carried out to provide a code reproducing the machine induced background. A comparison between the background simulation predictions in the KLOE interaction region and the corresponding KLOE data has been performed. These studies show a qualitative agreement between the expected and measured background rates. Simulations of new scrapers to be installed in the two rings are presented. Expected efficiencies on background reduction in the IRs are also presented. The comparison between the expected and measured efficiencies of the scrapers is discussed.

Type of presentation requested : Poster

Classification : [D02] Non-linear Dynamics - Resonances, Tracking, Higher Order


1392 - Computation of Insertion Device Fields and Simulation of their Effects on the SOLEIL Storage Ring*
P. Brunelle, O. Marcouille, A. Nadji, SOLEIL, Orsay

The lattice of the SOLEIL storage ring has been modified in order to increase the number of straight sections dedicated for insertion devices up to 21 [1]. Insertions with different characteristics have been chosen in order to produce photons in the large energy range from 5 eV to 50 keV at 2.75 GeV. Insertion devices such as high field wigglers, very long undulators, very small period minigap undulators and APPLE II type can affect the small emittance of the beam and the good beamlifetime. In order to validate the performances of the ring, their effects on emittance, energy spread, focusing and dynamic aperture have been studied. The complexity of the insertion magnetic structure leads to use a calculated field map generated by RadiaToTrack [2]and introduced in the ESRF BETA code version, especially to simulate the non linear effects for on and off-momentum particles.

* Work supported by SYNCHROTRON SOLEIL

[1] A. Nadji, P. Brunelle, J.-M. Filhol and M.-P. Level, "A modified lattice for SOLEIL with a large number of straight sections", Shanghai Symposium on Intermediate Energy Light Source, 23-26 september 2001.

[2] P. Elleaume, RadiaToTrack version 1.6.

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