Simulation study of halo formation in breathing round beams

Okamoto, Hiromi; Ikegami, Machiko

doi:10.1103/physreve.55.4694

Cited by 59 publications

(52 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our preliminary results from PIC simulations show that the redistribution process can produce the beam halo in the same fashion as a small rms mismatch [13]. A similar conclusion was made for 2-D axysymmetric beams [5,9]. In 3-D, however, the effect can be amplified by the coupling, especially noticeable in the bunches with c=a close to 1.…”

supporting

confidence: 52%

Halo formation in three-dimensional bunches

et al. 1998

View full text Add to dashboard Cite

A new class of self-consistent 6-D phase space stationary distributions is constructed both analytically and numerically. The beam is then mismatched longitudinally and/or transversely, and we explore the beam stability and halo formation for the case of 3-D axisymmetric beam bunches using particle-in-cell simulations. We concentrate on beams with bunch length-to-width ratios varying from 1 to 5, which covers the typical range of the APT linac parameters. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches. An interesting coupling phenomenon -a longitudinal or transverse halo is observed even for very small mismatches if the mismatch in the other plane is large -is discovered.

show abstract

supporting

confidence: 52%

Halo formation in three-dimensional bunches

et al. 1998

View full text Add to dashboard Cite

show abstract

“…The analytic model thus predicted the formation of a "halo" [4] for certain combinations of mismatch and tune depression. The numerical simulations using the "particle-core" model confirmed the validity of the models, and pointed as well to the existence of chaotic motion as the tune depression became more severe [5]- [9]. Subsequent work focused on the possible mechanism for particles escaping from the beam into the region of nonlinear oscillation [10].…”

Section: -D Modelmentioning

confidence: 78%

Halo formation in intense bunched beams

Fedotov

Gluckstern²

1999

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366)

View full text Add to dashboard Cite

The latest designs for high current ion linacs (Accelerator for the Transmutation of Waste, Accelerator for the Production of Tritium, Heavy Ion Drivers, Spallation Neutron Source Injector) require minimal radioactivation by the beam striking the beam pipe. As a result, efforts are being made to understand and control the growth of beam halo. There is general agreement that halos develop as a result of the parametric resonance between the ion oscillations in the beam bunch and collective oscillations of the bunch itself induced by mismatch in the linac. Analytic studies for a 2-D KV beam were found to give excellent agreement with corresponding computer simulations, which were then extended to other 2-D beams. Recently, analytic and numerical studies were performed for 3-D beam bunches (6-D phase space distributions), focusing attention on the formation of longitudinal halos and the possibility of bunch growth or loss of longitudinal bunch stability, as well as coupling between the longitudinal and transverse halos.

show abstract

“…The physics of beam halo has been extensively studied through analytical theory and multiparticle simulations [3][4][5][6][7][8][9][10][11][12][13][14][15]. In these studies, the particle-core model has been frequently used due to its usefulness in understanding the essential mechanism of halo formation and helping to predict the extent of beam halo.…”

Section: Introductionmentioning

confidence: 99%

Beam halo studies using a three-dimensional particle-core model

Qiang

Ryne

2000

Phys. Rev. ST Accel. Beams

View full text Add to dashboard Cite

In this paper we present a study of beam halo based on a three-dimensional particle-core model of an ellipsoidal bunched beam in a constant focusing channel including the effects of nonlinear rf focusing. For an initially mismatched beam, three linear envelope modes -a high frequency mode, a low frequency mode, and a quadrupole mode-are identified for an azimuthally symmetric bunched beam. The high frequency mode has three components all in phase; the low frequency mode has the transverse components in phase and the longitudinal component 180 ± out of phase; the quadrupole mode has no longitudinal component, and the two transverse components in the mode are 180 ± out of phase. We also study the case of an ellipsoidal bunched beam without azimuthal symmetry and find that the high frequency mode and the low frequency mode are still present but the quadrupole mode is replaced by a new mode with transverse components 180 ± out of phase and a nonzero longitudinal component. Previous studies, which generally addressed the situation where the longitudinal-to-transverse focusing strength is roughly 0.6 or less, conclude that the oscillation of the high frequency mode is predominantly transverse, and that of the low frequency mode is predominantly longitudinal. In this paper we present a systematic study of the features of the modes as a function of the longitudinal-to-transverse focusing strength ratio. We find that, when the ratio is greater than unity, the high frequency mode may contain a significant longitudinal component. Thus, excitation of the high frequency mode in this situation can be responsible for the formation of longitudinal beam halo. Furthermore, while previous studies have observed halo amplitudes roughly 2-3 times the matched beam edge, for the present parameters we observe much larger amplitudes (5 times or more). This is due to the fact that the longitudinalto-transverse focusing ratio used here is greater than that of previous studies. The finding of large transverse halo amplitude can have significant impact on the design of high-intensity ion accelerators where the longitudinal-to-transverse focusing ratio is slightly greater than unity in some parts of the linac.

show abstract

Simulation study of halo formation in breathing round beams

Cited by 59 publications

References 6 publications

Halo formation in three-dimensional bunches

Halo formation in three-dimensional bunches

Halo formation in intense bunched beams

Beam halo studies using a three-dimensional particle-core model

Contact Info

Product

Resources

About