The Evolution of Lateral Dose Distributions of Helium Ion Beams in Air: From Measurement and Modeling to Their Impact on Treatment Planning

To start clinical trials with the first clinical treatment planning system supporting raster-scanned helium ion therapy, a comprehensive database of beam characteristics and parameters was required for treatment room-specific beam physics modeling at the Heidelberg Ion-Beam Therapy Center (HIT). At six different positions in the air gap along the beam axis, lateral beam profiles were systematically measured for 14 initial beam energies covering the full range of available energies at HIT. The 2D-array of liquid-filled ionization chambers OCTAVIUS from PTW was irradiated by a pencil beam focused at the central axis. With a full geometric representation of HIT’s monitoring chambers and beamline elements in FLUKA, our Monte Carlo beam model matches the measured lateral beam profiles. A second set of measurements with the detector placed in a water tank was used to validate the adjustments of the initial beam parameters assumed in the FLUKA simulation. With a deviation between simulated and measured profiles below ±0.8 mm for all investigated beam energies, the simulated profiles build part of the database for the first clinical treatment planning system for helium ions. The evolution of beamwidth was also compared to similar simulations of the clinically available proton and carbon beam. This allows a choice of treatment modality based on quantitative estimates of the physical beam properties. Finally, we investigated the influence of beamwidth variation on patient treatment plans in order to estimate the relevance and necessary precision limits for lateral beam width models.

Dynamics of a rotating beam with intermittent contact

A flexible beam that is attached to a rotating hub, and whose tip encounters intermittent contact with a flat rigid surface is modelled. The beam is modelled using Euler-Bernoulli beam theory. Lagrange Equations are used to develop the system governing equations of motion, impact is modelled using the momentum balance method and contact is represented via a Lagrange multiplier and Coulomb friction. The model does not allow penetration of the surface to occur by enforcing a geometric constraint throughout contact. Both flexible and rigid initial beam assumptions before impact were analyzed. The effects of angular velocity, depth of penetration and the friction coefficient were examined. A numerical algorithm is outlined and Matlab software is used to implement the procedure. The results show compliance with expected trends and they show smoother transition from unconstrained to constrained motion for the flexible initial beam configuration compared to the rigid configuration.

Dynamics of a rotating beam with intermittent contact

A flexible beam that is attached to a rotating hub, and whose tip encounters intermittent contact with a flat rigid surface is modelled. The beam is modelled using Euler-Bernoulli beam theory. Lagrange Equations are used to develop the system governing equations of motion, impact is modelled using the momentum balance method and contact is represented via a Lagrange multiplier and Coulomb friction. The model does not allow penetration of the surface to occur by enforcing a geometric constraint throughout contact. Both flexible and rigid initial beam assumptions before impact were analyzed. The effects of angular velocity, depth of penetration and the friction coefficient were examined. A numerical algorithm is outlined and Matlab software is used to implement the procedure. The results show compliance with expected trends and they show smoother transition from unconstrained to constrained motion for the flexible initial beam configuration compared to the rigid configuration.

Effects of Turbulence on the Vortex Modes Carried by Quasi-Diffracting Free Finite Energy Beam in Ocean

By developing new wave structure function of a beam waves, we derive the transmitting probability of signal vortex modes in oceanic turbulence based on Rytov approximation theory. Applying this transmitting probability of signal vortex modes, we study the influence of oceanic turbulence on the transmittance of the vortex modes carried by Mathieu-Gaussian beam. This model shows the transmitting probability of Mathieu-Gaussian beam with narrow initial beam width, long wavelength, and small ellipticity parameter is higher than the transmitting probability of the signal vortex modes in case of the beam with wide initial beam width, short wavelength, and great ellipticity parameter. Furthermore, when Mathieu-Gaussian beam has a suitable semi-cone angle, the effect of weak-turbulence channel on the transmitting probability of signal vortex modes with different topological charge can be ignored. Mathieu-Gaussian beam is a more suitable carrier for high information channel of underwater wireless optical communication than Laguerre-Gaussian beam.

Full \(\mathcal{O}(\alpha)\) Electroweak Radiative Corrections to \(e^-e^+ \rightarrow W^-W^+\) with Initial Beam Polarization Effects

We calculate full \(\mathcal{O}(\alpha)\) electroweak radiative corrections and \(\mathcal{O}(\alpha^3)\) initial state radiation (ISR) corrections to \(e^-e^+ \rightarrow W^-W^+\) with initial beam polarization effects. In phenomenological results, we study the impact of electroweak and ISR corrections on cross-sections as well as their relevant distributions. We find that the corrections are order of 10% contributions. They are sizable contributions and should be taken into account at future lepton colliders.

Evolution of rectangular and triangular initial beam profiles in positive Kerr local medium

The hyperbolic secant (Sech) shape, as the initial beam profile, is the well-know profile that compensates the diffraction and self-focusing effect during propagation in Kerr medium, and evolves as the bright spatial soliton. The Sech beam can be confined in the Kerr medium andinduces its own waveguide. In this work, two initial beam profiles, rectangular and triangular functions, that are different than Sech profile, are considered, and the propagation of these beam profiles in third-order nonlinear (Kerr) medium is investigated. As a result, the initialbeam-width played an important role in confining the beam profiles in direction of propagation. In addition, the intensity profiles change to the Sech profile after some initial step of propagation. All the calculations and simulations have been done by the Split-Step numericalmethod with MATLAB program.