Multipacting-free transitions between cavities and beam-pipes

Belomestnykh, S.; Shemelin, Valery

doi:10.1016/j.nima.2008.05.041

Cited by 13 publications

(7 citation statements)

References 4 publications

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“…For example, the value of the rounding radius c influences the frequency and peak fields very weakly and can vary in a broad range. On the other hand, if this radius is small, a local minimum of the electric field occurs in this corner that can lead to multipactor [14] (in spite of weakness of this field). A reasonable choice for c is 2 Á ðR bp À R ae Þ as was checked in the cited paper.…”

Section: End Cells Of a Multicell Cavitymentioning

confidence: 99%

Optimal choice of cell geometry for a multicell superconducting cavity

Shemelin

2009

Phys. Rev. ST Accel. Beams

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An algorithm for optimization of the multicell cavity cells is proposed. Inner cells are optimized for minimal losses or minimal magnetic field, when the aperture diameter, E pk =E acc-the ratio of peak electric field to the accelerating field, and the wall slope angle are given. Optimization of the end cells is done for minimal losses or maximal acceleration in them. Two shapes of the end cells-with and without the end irises-are analyzed. This approach facilitates further optimization for higher order modes extraction because it permits keeping the achieved optimal values nearly the same while changing some dimensions of the cells. Comparison of the proposed cavity geometry with the TESLA cavity geometry illustrates the traits of the presented approach. It is also shown that lower values of the wall slope angle, which lead to the reentrant shape for the inner cells, are also beneficial for the end cells. For the Cornell Energy Recovery Linac most dangerous are dipole modes causing the beam breakup (BBU). Minimization of power of higher order modes (HOMs) in a multicell cavity was done using derivatives of the BBU parameter with respect to geometric parameters of the cavity cells. As a starting point of optimization, the shape with minimal losses at the fundamental mode was taken. Further changing the shape for better propagation of HOMs was done with degradation of the fundamental mode loss parameter G Á R sh =Q within 1% while decrease of the BBU parameter was nearly 3 orders of magnitude. The BBU threshold current tends to be inversely proportional to this parameter.

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Section: End Cells Of a Multicell Cavitymentioning

confidence: 99%

Optimal choice of cell geometry for a multicell superconducting cavity

Shemelin

2009

Phys. Rev. ST Accel. Beams

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“…The diameter of the beam tube was enlarged on one side of the cavity to allow for propagation of HOMs. The radius of the transition between the iris diameter and beam tube diameter was chosen as to avoid any local minimum of the electric field, avoiding possible multipacting in this region [18]. A summary of the electromagnetic parameters is given in Table I.…”

Section: A Cavity Designmentioning

confidence: 99%

Design of a cw, low-energy, high-power superconducting linac for environmental applications

Ciovati

Anderson

Coriton

et al. 2018

Phys. Rev. Accel. Beams

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The treatment of flue gases from power plants and municipal or industrial wastewater using electron beam irradiation technology has been successfully demonstrated in small-scale pilot plants. The beam energy requirement is rather modest, on the order of a few MeV, however the adoption of the technology at an industrial scale requires the availability of high beam power, of the order of 1 MW, in a cost effective way. In this article we present the design of a compact superconducting accelerator capable of delivering a cw electron beam with a current of 1 A and an energy of 1 MeV. The main components are an rf-gridded thermionic gun and a conduction cooled β = 0.5 elliptical Nb3Sn cavity with dual coaxial power couplers. An engineering and cost analysis shows that the proposed design would result in a processing cost competitive with alternative treatment methods. List of acronyms SRF -radio-frequency superconductivity GM -Gifford-McMahon BLA -beamline absorber HOM -higher-order mode FPC -fundamental power coupler BBU -beam breakup YBCO -yttrium barium copper oxide CW -continuous wave VED -vacuum electron device

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“…These electrons do not participate in multipacting near the equator region. Attraction towards the equator region or towards the beam axis, can be explained using the pandermotive forces [17]. In Figure 5, the satelite image shows an enhanced view of the equator region and trajectory of the particle.…”

Section: Identification Of the Multipacting Prone Locations And Reson...mentioning

confidence: 99%