A general schematic of how an RF cavity and slit are used in tandem with an electron microscope to create a regular train of electron bunches.
An ideal dielectric filled pillbox cavity.
A cross-sectional view demonstrating the electric and magnetic fields of the TM110 mode in a pillbox cavity.
A contour plot of P d /P vac as a function of tan δ and ɛ r . The lines represent values of constant P d /P vac . The symbols represent various common dielectric materials and their typical values measured at 3 GHz. The blue square represents the material chosen for filling the pillbox, while the red star represents our measured value.
Realistic dielectric filled cavity. The expanded radius in one direction further reduces frequency to the intended operating frequency.
Two TM110 modal frequencies after alterations to cavity.
The magnetic field profile along the longitudinal axis of the cavity at r = 0 for the realistic cavity geometry (red solid line) and the ideal pillbox cavity (black dotted line).
The absorption spectrum of the cavity as a function of frequency with a Lorentzian fit.
Field profile measurement (black circles) and calculated field profile (red solid curve) of the TM110 mode.
Frequency shift versus the depth of the dielectric tuning stub, measurement (black dots) plotted against CST Microwave Studio simulation (red solid curve).
General schematics demonstrating the beamline that the cavity was designed for and tested in.
(a) Electron spot on detector with no power fed to the cavity. (b) Streak electron beam on detector with Prf = 3.2 W power fed to the cavity.
Theoretical (red solid line) and measured (black dots) streak length of the electron beam at the detector as a function of RF input power.
Waist scan measurements of (a) the dc beam and (b) the chopped beam. The red curves are fits using Eq. (15). The fits yield normalized transverse emittances of 0.9 and 9 nm rad for the dc and the chopped beams, respectively.
Comparison of estimated characteristics between vacuum and dielectric filled 3 GHz pillbox cavity with a magnetic field amplitude B 0 = 3 mT, relative permittivity ɛ r = 36.5–38, and loss tangent tan δ = 2 × 10−4.
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