I summarize recent electron-cloud and coupled-bunch instability simulation studies for KEKB and SuperKEKB. The possible suppression of the electron-cloud build up inside quadrupole magnets by means of 4 permanent dipoles or by a super-imposed solenoid is investigated for the LER positron beam. Also studied is the electron accumulation in three different types of solenoidal fields, namely for a ...

In the CERN SPS microwave instability is an important limitation for the single bunch intensity of a proton beam. In the past this instability has been studied at energies above transition energy. In this paper we describe recent observations concerning the instability in the SPS at two different energies below transition. The results are compared with those obtained by the same measurement met...

Abstract Beam instability in the presheath region of negative ion beam extraction is investigated theoretically and experimentally. The linear stability analysis shows that unstable due to coupling between positive flow flow. On other hand, no clear activity can be seen experiment frequency range predicted by theory. may not cause degradation focusing because collisional damping and/or Landau d...

1.1.1 Introduction For linear accelerators, a single bunch instability of a positron bunch due to electrons created by ionization of the residual gas was discussed in Ref. [1], where a coherent oscillation of both electrons and positrons grows from any small initial perturbation of the bunch distribution, e.g. from the statistical fluctuations due to the finite number of beam particles. This in...

We review recent results on the propagation and self-focusing of intense femtosecond laser pulses with shaped beam profiles in transparent dielectric media. At sufficiently high optical power, beam shaping seeds into the transverse modulation instability and results in the deterministic placement of intense laser filaments within the beam profile. Resulting spatial filament distributions may be...

The electromagnetic wake field response of a hollow plasma channel to a driver (laser or charged particle beam) of arbitrary velocity is derived. The dispersion and loss factors of excited fundamental and higher order azimuthal modes are computed. Growth rates for beam breakup instabilities are calculated and beam transport is studied. External focusing is shown to provide a method of controlli...

The excitation of ion azimuthal surface oscillations with extraordinary polarization by light ion beam is studied analytically. Beam-plasma system consists of a cylindrical metal waveguide filled partially by cold magnetized plasma and light ion flow rotating around the plasma column. Dependencies of the beam instability growth rate on the system parameters (plasma and beam densities, value of ...

The electron beam which IS accelerated in the SLAC two-mile accelerator exhibits both transverse and longitudinal interactions with the disk-loaded waveguide, The transverse interactions include such effects as rf steering caused by field asymmetries which exist in the couplers, and beam breakup, The latter is a growing instability which occurs above a given current threshold and deflects the b...