Feasibility of electron cyclotron autoresonance acceleration by a short terahertz pulse

A vacuum autoresonance accelerator scheme for electrons, which employs terahertz radiation and currently available magnetic fields, is suggested. Based on numerical simulations, parameter values, which could make the scheme experimentally feasible, are identified and discussed

Fields of an ultrashort tightly-focused laser pulse

Analytic expressions for the electromagnetic fields of an ultrashort, tightly focused, linearly polarized laser pulse in vacuum are derived from scalar and vector potentials, using a small parameter which assumes a small bandwidth of the laser pulse. The derived fields are compared with those of the Lax series expansion and the complex-source-point approaches and are shown to be well-behaved and accurate even in the subcycle pulse regime. We further demonstrate that terms stemming from the scalar potential and due to a fast varying pulse envelope are non-negligible and may significantly influence laser-matter interactions

High-quality multi-GeV electron bunches via cyclotron autoresonance

Autoresonance laser acceleration of electrons is theoretically investigated using circularly polarized focused Gaussian pulses. Many-particle simulations demonstrate feasibility of creating over 10-GeV electron bunches of ultra-high quality (relative energy spread of order 10^-4), suitable for fundamental high-energy particle physics research. The laser peak intensities and axial magnetic field strengths required are up to about 10^18 W/cm^2 (peak power ~10 PW) and 60 T, respectively. Gains exceeding 100 GeV are shown to be possible when weakly focused pulses from a 200-PW laser facility are used

Transport Properties in Ferromagnetic Josephson Junction between Triplet Superconductors

Charge and spin Josephson currents in a ballistic superconductor-ferromagnet-superconductor junction with spin-triplet pairing symmetry are studied using the quasiclassical Eilenberger equation. The gap vector of superconductors has an arbitrary relative angle with respect to magnetization of the ferromagnetic layer. We clarify the effects of the thickness of ferromagnetic layer and magnitude of the magnetization on the Josephson charge and spin currents. We find that 0-\pi transition can occur except for the case that the exchange field and d-vector are in nearly perpendicular configuration. We also show how spin current flows due to misorientation between the exchange field and d-vector.Comment: 6 pages, 8 figure

Evolution of Patient Dose in Chest Radiotherapy Planning

Radiographic image has been used for patient positioning, target localization radiation beam alignment, and subsequent verification of treatment delivery in radiotherapy. Radiographic imaging as all medical use of ionizing radiation can give significant exposure to the patient. The aim of this study was to determine the radiological dose for chest imaging. Imaging dose during course of radiotherapy add dose to high therapeutic dose therefore this raises the issue of the balance between the benefit of these additional imaging exposures and the associated risk of radiation induced cancer arising from them. Therefore, estimation of imaging doses and possibility of its risk is necessary to provide adequate justification of this exposure. In this dissertation the main investigated type of the X-ray simulation were chest AP and PA, the total number of patients was 10 ( 62 radiographs). The fluctuation of the entrance surface dose (ESD) was relatively ranging from 0.35 micro;Gy to 8.43 micro;Gy for AP projection, and from 0.12 micro;Gy to 0.46 micro;Gy for PA projection. The mean values of ESD were found to be within guidance limits which was proposed in some countries (CEC 2004, and Germany 2003)