Transport of a space-charge dominated electron beam in a short-quadrupole channel

Bernal, S.; Chin, P.; Kishek, R. A.; Li, Y.; Reiser, M.; Wang, J. G.; Godlove, Terry F.; Haber, I.

doi:10.1103/physrevstab.1.044202

Cited by 23 publications

(11 citation statements)

References 8 publications

(9 reference statements)

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“…We show that containment of beams over such a broad range of intensities is possible thanks to the high density of quadrupoles in UMER, a feature not to be found in any other circular machine. (Previous work, published by some of us, related to matching of a space-charge dominated electron beam in a prototype experiment [11].) Further, we revisit the basic characterization of the short UMER magnets and show how proper modeling is important for envelope matching in special cases.…”

Section: Introductionmentioning

confidence: 92%

RMS envelope matching of electron beams from “zero” current to extreme space charge in a fixed lattice of short magnets

Bernal

Kishek

et al. 2006

Phys. Rev. ST Accel. Beams

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We present detailed calculations of RMS-envelope matching over a broad range of beam intensities for the University of Maryland Electron Ring (UMER). Containment of beams from zero current to extreme space charge, all without changing the strength of external focusing in the periodic lattice, is possible thanks to the high density of quadrupoles in UMER. In turn, the small-aspect ratio of the UMER magnets results in gradient or field profiles that are ''all edges,'' thus requiring special treatment when constructing accurate hard-edge models. Further, the results of matching calculations, for both symmetric and asymmetric FODO (alternating gradient) schemes, are compared with calculations from simple general expressions valid in the uniform-focusing approximation of the periodic lattice. Finally, some aspects of the source-to-FODO matching calculation/optimization problem are discussed, together with sensitivity studies of the matching solutions under realistic conditions. The examples from the UMER project, which include experimental results, emphasize the practical aspects of beam envelope matching.

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Section: Introductionmentioning

confidence: 92%

RMS envelope matching of electron beams from “zero” current to extreme space charge in a fixed lattice of short magnets

Bernal

Kishek

et al. 2006

Phys. Rev. ST Accel. Beams

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“…More recently, experimental evidence of beam hollowing was found in a high-brightness, space-charge-dominated electron beam experiment at the University of Maryland. 37,38 As an important application of the equilibrium beam theory presented in Sec. IV, we develop and demonstrate a technique for controlling of beam halo formation and beam hollowing in ultrahigh-brightness beams.…”

Section: Control Of Halo Formation and Beam Hollowingmentioning

confidence: 99%

Coherent Structures and Chaos in Beam Plasmas

Chen¹

2002

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instru the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, incl Coherent Structures and Chaos in Beam Plasmas AUTHOR(S)Chiping Chen Approved for public release; distribution unlimited. S. FUNDING NUMBERS F49620-97-1-0325 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air 12b. DISTRIBUTION CODE ABSTRACT (Maximum 200 words)This report summarizes our research carried out under the auspices of the above referenced grants from May 1, 1997 to December 31, 1999. The goal of this research is to investigate coherent structures and chaos in beam plasmas in regimes relevant to the development of advanced microwave/millimeter wave sources. Preprints and reprings describing detailed findings in recent investigations are provided in a compendium of 1997-2000 reprints in refereed journals at the end of the report. This report summarizes our research carried out under the auspices of the above referenced grant from May 1, 1997 to December 31, 1999. The goal of this research is to investigate coherent structures and chaos in beam plasmas in regimes relevant to the development of advanced microwave/millimeter wave sources. Preprints and reprints describing detailed findings in recent investigations are provided in a compendium of 1997-2000 reprints in refereed journals at the end of this report. The following is a brief summary of our research accomplishments in selected areas. Mechanisms of Chaotic Electron Motion and Beam Halo Formation [1-3]An important issue in the design of HPM tubes is how to prevent high-intensity relativistic electron beams from forming halos because they cause electron beam losses and subsequent plasma formation, rf pulse shortening and rf breakdown [4]. Under the auspices of this grant, investigations were conducted of mechanisms by which chaotic particle motion and halo formation occurs [1][2][3].In particular, it was found [5,6] that there are two important mechanisms for chaotic particle motion and halo formation in high-intensity electron beams in such systems as high power klystrons. One mechanism is due to a root-mean-square (rms) mismatch between the beam and externally applied focusing field [5], The rms mismatch is induced by the bunching of the electron beam by intense rf (radiation phis electrostatic wave) fields inside the device. Above a certain threshold, rms mismatched electron beams produce pronounced (sizable) halos asymptotically. For high-intensity electron beams, the threshold occurs at the relative envelope mismatch of 42%, as predicated analytically and confirmed by self-consistent simulations in earlier work [7], The other mechanism is due to the subtle effect of a mismatch in the particle phase-space distribution (e.g., a nonuniform charge density distribution) under the rms matching condition [6]. In HPM tubes...

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“…The K-V envelope computer code SPOT [8] is used for the calculations; the detailed procedure is presented in Ref. [4]. Table II contains the center locations of elements along the injector section, as well as the solenoid's peak field and quadrupole peak gradients.…”

Section: Root-mean-square Envelope Matchingmentioning

confidence: 99%

“…In addition, related matching experiments with a 4 keV, 17 mA, 5 µs electron beam appear in Ref. [4].…”

Section: Introductionmentioning

confidence: 99%

Beam tests of the 10 keV injector for the University of Maryland electron ring (UMER)

Bernal

Li²,

Virgo³

et al.

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

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Results are presented of the first experiments with a 10 keV, 100 mA beam in the matching section for UMER. The section, about 1.5 m long, consists of one short solenoid, six printed-circuit (PC) quadrupoles, a bend PC dipole, a number of steering dipoles, and two sets of Helmholtz coils for balancing the Earth's field. The 2 RMS beam radius as a function of axial distance in the straight part of the beam line is obtained from fluorescent screen pictures. The results are compared with calculations using the K-V envelope equations. The importance of an accurate determination of the initial conditions, i.e. beam envelope size and slope at the entrance plane, as well as the emittance, is emphasized. Furthermore, the role of different types of errors, specially misalignment and quadrupole rotations is discussed.

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Transport of a space-charge dominated electron beam in a short-quadrupole channel

Cited by 23 publications

References 8 publications

RMS envelope matching of electron beams from “zero” current to extreme space charge in a fixed lattice of short magnets

RMS envelope matching of electron beams from “zero” current to extreme space charge in a fixed lattice of short magnets

Coherent Structures and Chaos in Beam Plasmas

Beam tests of the 10 keV injector for the University of Maryland electron ring (UMER)

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