نتایج جستجو برای: photon field size
تعداد نتایج: 1356235 فیلتر نتایج به سال:
These experiments compare the out-of-field dose delivered during different treatment techniques (photons, active and passive delivered protons and carbon ions) in standardized conditions. A water phantom is used as tissueequivalent material and is irradiated with a rectangular field. The dose is measured in lateral direction in the plane of the field as shown in Fig. 1. The composition of the o...
Introduction For dose measurement in Megavoltage (MV) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. Therefore, the result of measurement should be corrected with a displacement perturbation correction factor (Pdis) or using an effective point of measurement (EPOM). The aim of this study is to calculate the EPOM for cylindrical ion chamber and...
We study the spontaneous Lorentz symmetry breaking in a field theoretical model in (2+1)-dimension, inspired by string theory. This model is a gauge theory of an anti-symmetric tensor field and a vector field (photon). The Nambu-Goldstone (NG) boson for the spontaneous Lorentz symmetry breaking is identified with the unphysical massless photon in the covariant quantization. We also discuss an a...
Near-field two-photon optical lithography is demonstrated by using ;120 fs laser pulses at 790 nm in an apertureless near-field optical microscope, which produces lithographic features with ;70 nm resolution. The technique takes advantage of the field enhancement at the extremity of a metallic probe to induce nanoscale two-photon absorption and polymerization in a commercial photoresist, SU-8. ...
Three-photon wide-field depth-resolved excitation is used to overcome some of the limitations in conventional point-scanning two- and three-photon microscopy. Excitation of chromophores as diverse as channelrhodopsins and quantum dots is shown, and a penetration depth of more than 700 μm into fixed scattering brain tissue is achieved, approximately twice as deep as that achieved using two-photo...
Towards overcoming the size limitations of conventional two-photon fluorescence microscopy, we introduce two-photon imaging based on microelectromechanical systems (MEMS) scanners. Single crystalline silicon scanning mirrors that are 0.75 mm x 0.75 mm in size and driven in two dimensions by microfabricated vertical comb electrostatic actuators can provide optical deflection angles through a ran...
For decades, progress in the field of optical (including solar) energy conversion was dominated by advances in the conventional concentrating optics and materials design. In recent years, however, conceptual and technological breakthroughs in the fields of nanophotonics and plasmonics combined with a better understanding of the thermodynamics of the photon energyconversion processes reshaped th...
Introduction Superficial X-ray therapy is one of the most important treatment methods in radiotherapy especially in the treatment of superficial skin lesions (Up to 300 kVp). Quality of the X-ray beam that can be expressed by Half-Value Layer (HVL), are important indices for this type of treatment effective energy of photon and Homogeneity Coefficient (HC). Materials and Methods The HC of the s...
Background: Megavoltage beams used in radiotherapy are contaminated with secondary electrons. Different parts of linac head and air above patient act as a source of this contamination. This contamination can increase damage to skin and subcutaneous tissue during radiotherapy. Monte Carlo simulation is an accurate method for dose calculation in medical dosimetry and has an important role in opt...
Mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons enables the realization of optical nonlinearities which can modify light on the level of individual photons. This novel approach forms the basis of a growing Rydberg quantum optics toolbox, which already contains photonic logic building-blocks such as single-photon sources, switches, tr...
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