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Title: Wakefield suppression using beatwave structures

Abstract

A proposed method of suppressing transverse wakefields in an accelerating structure makes use of the fact that superposition of long-range wakes excited by an electron bunch transversing a series of accelerating cells with different transverse frequencies can produce interference cancellation, thereby significantly reducing the magnitudes of the harmful wake potentials. Analytic calculations as well as time-domain and modal sum simulations are performed to the beatwave effects produced by detuned, disk-loaded cavities as function of their transverse frequency spread and the population density.

Authors:
;
Publication Date:
Research Org.:
Duly Consultants, Rancho Palos Verdes, CA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
82268
Report Number(s):
CONF-910505-444
ON: DE95014736; TRN: 95:017367
DOE Contract Number:
FG03-90ER81080
Resource Type:
Conference
Resource Relation:
Conference: 1991 Institute of Electrical and Electronics Engineers (IEEE) particle accelerator conference (PAC), San Francisco, CA (United States), 6-11 May 1991; Other Information: PBD: [1991]
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; LINEAR ACCELERATORS; BEAM BUNCHING; STABILITY; HARMONICS; FREQUENCY MODULATION; DAMPING

Citation Formats

Yu, D., and Kim, J.S. Wakefield suppression using beatwave structures. United States: N. p., 1991. Web.
Yu, D., & Kim, J.S. Wakefield suppression using beatwave structures. United States.
Yu, D., and Kim, J.S. Tue . "Wakefield suppression using beatwave structures". United States. doi:. https://www.osti.gov/servlets/purl/82268.
@article{osti_82268,
title = {Wakefield suppression using beatwave structures},
author = {Yu, D. and Kim, J.S.},
abstractNote = {A proposed method of suppressing transverse wakefields in an accelerating structure makes use of the fact that superposition of long-range wakes excited by an electron bunch transversing a series of accelerating cells with different transverse frequencies can produce interference cancellation, thereby significantly reducing the magnitudes of the harmful wake potentials. Analytic calculations as well as time-domain and modal sum simulations are performed to the beatwave effects produced by detuned, disk-loaded cavities as function of their transverse frequency spread and the population density.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 31 00:00:00 EST 1991},
month = {Tue Dec 31 00:00:00 EST 1991}
}

Conference:
Other availability
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  • In order to prevent electrical breakdown occurring in the JLC/NLC (Japanese Linear Collider/Next Linear Collider) X-band structures several new structures are under investigation. These accelerating structures represent an evolutionary design of the DDS series of structures [1]. The phase advance per cell has been varied and the detailed elliptical shape of the cell has been varied in order to simultaneously minimize the group velocity, the surface electromagnetic fields and the pulse temperature rise on the copper surface [2]. It is also important to ensure that the wakefield induced by multiple bunches traversing the accelerating structures does not disrupt trailing bunches.more » The long-range wakefield must be decreased adequately in order to prevent a BBU (Beam Break Up) instability occurring and to ensure that emittance dilution due to the higher order modes is kept to acceptable levels. The long-range wakefield is forced to de-cohere by detuning all of the frequencies such that the mode density of frequencies is approximately Gaussian. In order to minimize the impact of the wakefield on the beam dynamics we change the bandwidth and the standard deviation of the Gaussian distribution of frequencies such that a ''cost function'' is minimized. Interleaving of cell frequencies of adjacent structures is required to adequately damp the wakefield of each particular structure under consideration. The resulting alignment tolerances imposed on the cells and structures is significantly looser alignment tolerances with the use of the code.« less
  • The Argonne Wakefield Accelerator group develops accelerating structures based on dielectric loaded waveguides. We use high charge short electron bunches to excite wakefields in dielectric loaded structures, and a second (low charge) beam to probe the wakefields left behind by the drive beam. We report measurements of beam parameters and also initial results of the dielectric loaded accelerating structures. We have studied acceleration of the probe beam in these structures and we have also made measurements on the RF pulses that are generated by the drive beam. Single drive bunches, as well as multiple bunches separated by an integer numbermore » of RF periods have been used to generate the accelerating wakefields.« less
  • We discuss wakefield excitation and propagation in dielectric structures, particularly concentrating on the case of multiple drive beam excitation in multimode structures. We emphasize calculations of the energy loss of the drive bunch train, the amplitude of the wakefield, and the relation between power flow and stored energy in the dielectric wakefield device. We show that for a collinear multimode structure the amplitude of the wakefield generated by a bunch train is less than or equal to the wakefield generated by a single bunch of the same total charge. Furthermore, the transformer ratio, R, is shown to be always lessmore » than 2, even in the multiple drive beam case. Plans for an experiment to measure wakes in a multimode structure at AWA are presented.« less