Author Affiliations
Department of Electrical Engineering, Technion, Israel Institute of Technology, Haifa 32000, Israelshow less
Fig. 1. Schematic description of the accelerating structure. A trigger bunch propagates in a cylindrical metallic waveguide of radius
filled with an active medium. This bunch is injected into the structure with velocity
larger than the Cerenkov velocity
and generates an entire manifold of TM modes which propagate behind. One of the eigenmodes is amplified by the active medium and many wavelengths behind the trigger bunch the former accelerates a trailing train bunch.
Fig. 2. (a) The dynamics of the wake
on the axis (solid curve), the PID,
(dashed–dotted curve), and the trigger bunch profile,
(dashed curve). The value of the saturated wake
is shown by the dotted curve. (b) A comparison of the nonlinear wake dynamics in real units (solid curve) with the linear wake dynamics (dots). In addition, the profile of the bunch is drawn as a reference (dashed curve).
Fig. 3. The mode spectrum of the wake
. Here, the single-resonance mode is
.
Fig. 4. (a) A two-dimensional plot of the longitudinal wake
. The green rectangle is the location of the trigger bunch. (b) The same as (a) but in the region that is marked in magenta in (a). (c) The radial dependence of the wake at
.
Fig. 5. The energy conservation. Here,
is the energy of the ground state and
is the energy of the excited state; (d) shows the deviation from energy conservation.
Fig. 6. The wake dynamics (a) and the wake spectrum (b) for various Cerenkov parameters and bandwidths. The solid curve corresponds to
and
, where
and
are the Cerenkov and bandwidth parameters as in Figure
2. The dotted curve corresponds to
and
. The dashed curve corresponds to
and
.
Fig. 7. The dependence of the saturation value (a) and saturation length (b) on the waveguide and trigger bunch parameters. Here, the index 0 represents the parameter value as in Figure
2 or Ref. [
18].
Parameter | Symbol | Value |
---|
Active medium resonance wavelength | | | Active medium resonance bandwidth | | 37 GHz | Active medium plasma frequency | | | Electrical dipole moment | | 0.0275 Debye | Initial PID | | | Einstein’s coefficient | | | Relative permittivity | | 1.0014 | Waveguide radius | | 5.065 cm | E-beam Lorentz factor | | 600 | E-beam total charge | | | E-beam length | | | E-beam modulation | | 20% | E-beam radius | | 4 mm |
|
Table 1. Structure parameters of our studied example. Note that the set of parameters used here is the same as in Ref. [
22].