We demonstrate that any two-dimensional accelerating beam can be described in a canonical form in Fourier space. In particular, we demonstrate that there is a one-to-one correspondence between complex functions in the real line (the line spectrum) and accelerating beams. An arbitrary line spectrum can be used to generate novel accelerating beams with diverse transverse shapes. The line spectra ...

A relatively fast and simple method utilizing Gaussian beams (GBs) is developed which requires only a few seconds on a workstation to compute the near/far fields of electrically large reflector antennas when they are illuminated by a feed with a known radiation pattern. This GB technique is fast, because it completely avoids any numerical integration on the large reflector surface which is requ...

Although highly conformal dose distributions can be achieved by IMRT planning, this often requires a large number of segments or beams, resulting in increased treatment times. While flattening-filter-free beams offer a higher dose rate, even more segments may be required to create homogeneous target coverage. Therefore, it is worthwhile to systematically investigate the dependence of plan quali...

We use a three-dimensional Gerchberg–Saxton algorithm (Shabtay (2003) Opt. Commun. 226 33) to calculate the Fourier-space representation of physically realizable light beams with arbitrarily shaped three-dimensional intensity distributions. From this representation we extract a phase-hologram pattern that allows us to create such light beams experimentally. We show several examples of experimen...

PURPOSE To characterize and quantify the distal edge activity fall off, created in a phantom by a proton therapy beam METHOD AND MATERIALS: A 30×30×10cm polymethylmethacrylate phantom was irradiated with a proton therapy beam using different ranges and beams. The irradiation volume is approximated by a right circular cylinder of diameter 7.6cm and varying lengths. After irradiation, the phantom...

We studied the nonlinear parametric interaction of femtosecond fractionally-charged optical vortices in a Raman-active medium. Propagation of such beams was described using the Kirchhoff–Fresnel integrals by embedding a non-integer 2π phase step in a Gaussian beam profile. When using fractionally-charged pump or Stokes beams, we observed the production of new topological charge and phase discon...

The propagation of light beams through astigmatic lens systems is accompanied by a transfer of orbital angular momentum. We develop a method to describe propagating light beams by operators of which the field is an eigenfunction. This method is applied to determine when an astigmatic lens system transforms gaussian beams into other gaussian beams and where in the system angular momentum is tran...

The resistive-wall instability of charged particle beams has been experimentally studied in space-charge dominated electron beams. The beam energy is in the range of 3 to 8.5 keV, the beam current is between 25 mA and 62 mA. In the experiment, electron beams produced from a thermionic cathode are passed through a 0.96 m long glass tube coated with a resistive material, and localized space-charg...

The behavior of four coupled self-excited elastic beams is numerically studied using the finite-difference method. Self-excitation is modeled by adding a van der Pol damping term. Coupling based on shared boundary conditions at the roots of the beams is proposed, and the influence of the coupling on the dynamics is analyzed. Time and space correlation coefficients are employed to measure the de...

We report experiments on self-focusing of femtosecond diffraction-resistant vortex beams in water. These beams are higher-order Bessel beams with weak azimuthal modulation of the transverse intensity patterns. The modulation overrides the self-focusing dynamics and results in the formation of regular bottlelike filament distributions. The peak-power thresholds for filamentation, at a particular...