Cumulative beam breakup in linear accelerators with time-dependent parameters

Abstract

A formalism presented in a previous paper for the analysis of cumulative beam breakup (BBU) with arbitrary time dependence of the beam current and with misalignment of the cavities and focusing elements [J. R. Delayen, Phys. Rev. ST Accel. Beams 6, 084402 (2003)] is extended to include time dependence of the focusing and coupling between the beam and the dipole modes. Such time dependence, which could result from an energy chirp imposed on the beam or from rf focusing, is known to be effective in reducing BBU-induced instabilities and emittance growth. The analytical results are presented and applied to practical accelerator configurations and compared to numerical simulations.

Stability condition for the drive bunch in a collinear wakefield accelerator

“…4 were calculated by a numerical solution of equation ( 14) and ( 15) with f (s) determined from Eq. (34). One can clearly see that phase trajectories are indeed very close to being able to achieve the above formulated goal.…”

“…Ultimately, the BNS damping not only guarantees the stability of the electron bunch motion, but also the preservation of the electron bunch's projected emittance. More information about the BNS damping can be found in ( [23][24][25][26][27][28][29][30][31][32][33][34]) and in the Chapter 3 of the textbook [28].…”

“…Initially studied in a set of seminal papers ( [16][17][18]), the BBU has been a subject of many more investigations (e.g., see [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]). An elegant method to control the instability was proposed by Balakin, Novokhatski, and Smirnov in [19] and was named the BNS damping thereafter.…”

Filling Pattern Dependence of Regenerative Beam Breakup Instability in Energy Recovery Linacs

“…BBU has potential to occur where the beam interacts with a higher order mode (HOM) of an RF structure that it traverses and becomes deflected. There are two general classes of BBU, cumulative [15][16][17][18][19][20] and regenerative [21,22]. Cumulative is where the deflection builds up over multiple structures and is not the subject of this study.…”

Analytic model of 3D beam dynamics in a wakefield device

“…[4], and the most complete, recent solution was derived by Delayen in a series of publications Refs. [5][6][7].…”