scholarly journals Study of the volume reduction impact on secondary photons emergent from flattening filter for high radiotherapy quality

2019 ◽  
Vol 25 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Mohamed Bencheikh ◽  
Abdelmajid Maghnouj ◽  
Jaouad Tajmouati ◽  
Abdessamad Didi
Keyword(s):  
Energy Distribution ◽  
Spectral Distribution ◽  
Low Energy ◽  
Angular Spread ◽  
Volume Reduction ◽  
Energy Profile ◽  
Tumor Treatment ◽  
Energy Fluence ◽  
Flattening Filter

Abstract This study aims to investigate and evaluate the secondary photons characterizations under flattening filter (FF) for high radiotherapy quality in terms of fluence, energy fluence, energy fluence distribution, spectral distribution and angular spread distribution of secondary photons, which are mainly coming from primary collimator originated in the whole Linac head. However, the flattening filter illuminates the photons of low energy. After this component, the secondary photons of low energy are coming from flattening filter and secondary collimators that contaminate the dosimetry for deep tumor treatment. Fluence profile, energy profile and angular spread of secondary photons decreased with FF volume reduction percent but energy distribution and spectral distribution kept almost constant with FF volume reduction. The FF volume reduction allows reducing the secondary photons emergent from FF in number and in energy and it permits to increase the radiotherapy efficiency by decreasing the photons contamination when the cancer is treating.

Spectra of X-Ray Tubes with Transmission Anodes for Fundamental Parameter Analysis

1992 ◽  
Vol 36 ◽  
pp. 81-88
Author(s):  
Horst Ebel ◽  
Maria F. Ebel ◽  
Christian Pöhn ◽  
Bernd Schoßmann
Keyword(s):  
Energy Distribution ◽  
Penetration Depth ◽  
High Voltage ◽  
Spectral Distribution ◽  
Narrow Band ◽  
Typical Feature ◽  
Parameter Analysis ◽  
Fundamental Parameter ◽  
X Rays ◽  
X Ray

AbstractThe approach for the description of the emission of white and characteristic x-rays from standard x-ray tubes is modified for an application to transmission anodes. This modification is based on the assumption of a negligible penetration depth of the electrons in comparison to the thickness of the anode. The results of our considerations are presented for Cu, Mo and W anodes with two different thicknesses. For comparison, the spectra of standard anodes which have been operated with identically high voltages and anode currents are given. A typical feature of transmission anodes is their spectral hardening of the energy distribution of emitted photons. A further interesting detail is the development of narrow band excitation anodes as can be seen from the results for Mo. With anode thicknesses of approximately 200 μm and a high voltage of 30 kv the spectral distribution is restricted to an energy ranging from 15 to 20 keV.

Low Energy Electron Impact Ionization and Fragmentation: Cyclobutanone

1973 ◽  
Vol 51 (4) ◽  
pp. 624-627 ◽  
Author(s):  
Graham Richard Branton ◽  
Claudio Kong Nam Pua
Keyword(s):  
Energy Distribution ◽  
Electron Impact ◽  
Mass Spectrometer ◽  
Ionization Energy ◽  
Impact Ionization ◽  
Electron Impact Ionization ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron

Cyclobutanone is shown to yield both C3H6+ and C2H2O+ ions on fragmentation under electron impact in a mass spectrometer. Using the energy distribution difference (EDD) technique the ionization energy of cyclobutanone is found to be 9.58 eV and the appearance potentials of the C3H6+ and C2H2O+ ions are found to be 9.85 and 10.53 eV, respectively.

Collision-kerma conversion between dose-to-tissue and dose-to-water by photon energy-fluence corrections in low-energy brachytherapy

2016 ◽  
Vol 62 (1) ◽  
pp. 146-164 ◽  
Author(s):  
Vicent Giménez-Alventosa ◽  
Paula C G Antunes ◽  
Javier Vijande ◽  
Facundo Ballester ◽  
José Pérez-Calatayud ◽  
...  
Keyword(s):  
Photon Energy ◽  
Low Energy ◽  
Energy Fluence

The Effect of the Spectral Distribution of Wave Energy on the Performance of a Bottom Hinged Flap Type Wave Energy Converter

2012 ◽  
Author(s):  
D. Clabby ◽  
A. Henry ◽  
M. Folley ◽  
T. Whittaker
Keyword(s):  
Energy Distribution ◽  
Wave Height ◽  
Wave Energy ◽  
Spectral Distribution ◽  
Energy Production ◽  
Spectral Energy Distribution ◽  
Wave Climate ◽  
Wave Energy Converter ◽  
Spectral Energy ◽  
Energy Converter

The power output from a wave energy converter is typically predicted using experimental and/or numerical modelling techniques. In order to yield meaningful results the relevant characteristics of the device, together with those of the wave climate must be modelled with sufficient accuracy. The wave climate is commonly described using a scatter table of sea states defined according to parameters related to wave height and period. These sea states are traditionally modelled with the spectral distribution of energy defined according to some empirical formulation. Since the response of most wave energy converters vary at different frequencies of excitation, their performance in a particular sea state may be expected to depend on the choice of spectral shape employed rather than simply the spectral parameters. Estimates of energy production may therefore be affected if the spectral distribution of wave energy at the deployment site is not well modelled. Furthermore, validation of the model may be affected by differences between the observed full scale spectral energy distribution and the spectrum used to model it. This paper investigates the sensitivity of the performance of a bottom hinged flap type wave energy converter to the spectral energy distribution of the incident waves. This is investigated experimentally using a 1:20 scale model of Aquamarine Power’s Oyster wave energy converter, a bottom hinged flap type device situated at the European Marine Energy Centre (EMEC) in approximately 13m water depth. The performance of the model is tested in sea states defined according to the same wave height and period parameters but adhering to different spectral energy distributions. The results of these tests show that power capture is reduced with increasing spectral bandwidth. This result is explored with consideration of the spectral response of the device in irregular wave conditions. The implications of this result are discussed in the context of validation of the model against particular prototype data sets and estimation of annual energy production.

scholarly journals Identification of 90Sr and 204Tl beta radiation sources by energy distribution with a 3GEM detector

DYNA ◽  
2020 ◽  
Vol 87 (215) ◽  
pp. 174-179
Author(s):  
Freddy Fuentes Robayo ◽  
Rafael Maria Gutierrez Salamanca
Keyword(s):  
Energy Loss ◽  
Energy Distribution ◽  
Industrial Application ◽  
Radiation Source ◽  
Radiation Detection ◽  
High Energy ◽  
Low Energy ◽  
Beta Radiation ◽  
Detection And Identification ◽  
Radiation Sources

This paper presents the performance of a 3GEM in terms of identification of high and low beta energy radiation sources through the energy distribution of the main beta radiation sources used for industrial application 90Sr and 204Tl. We compare the beta radiation theoretical energy loss into the drift zone with experimental energy distribution at different 3GEM voltages. The experimental results show that the Most Probable Value (MPV) of the fitted Landau distribution obtained from 90Sr and 204Tl obtained a degree of error lower than 14% in comparison to the theoretical calculation. Additionally, high energy beta radiation source (90Sr) is identified in comparison to low energy (204Tl) - taking into account the MPV and sigma values from the fitted Landau distribution. These results are essential to design and implement a new application that utilizes the performance and special characteristics of the 3GEM for beta radiation detection and identification.

Accelerated Computation of Free Energy Profile at Ab Initio QM/MM Accuracy via a Semi-Empirical Reference-Potential. III. Gaussian Smoothing on Density-of-States

2020 ◽  
Author(s):  
Wenxin Hu ◽  
Pengfei Li ◽  
Jia-Ning Wang ◽  
Yuanfei Xue ◽  
Yan Mo ◽  
...  
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Density Of States ◽  
Energy Region ◽  
Potential Method ◽  
Small Sample ◽  
Low Energy ◽  
Energy Profile ◽  
Free Energy Profile ◽  
Reference Potential

Calculations of free energy profile, aka potential of mean force (PMF), along a chosen collective variable (CV) are now routinely applied to the studies of chemical processes, such as enzymatic reactions and chemical reactions in condensed phases. However, if the ab initio QM/MM level of accuracy is required for the PMF, it can be formidably expensive even with the most advanced enhanced sampling methods, such as umbrella sampling. To ameliorate this difficulty, we developed a novel method for the computation of free energy profile based on the reference-potential method recently, in which a low-level reference Hamiltonian is employed for phase space sampling and the free energy profile can be corrected to the level of interest (the target Hamiltonian) by energy reweighting in a nonparametric way. However, when the reference Hamiltonian is very different from the target Hamiltonian, the calculated ensemble averages, including the PMF, often suffer from numerical instability, which mainly comes from the overestimation of the density-of-states (DoS) in the low-energy region. Stochastic samplings of these low-energy configurations are rare events. If a low-energy configuration has been sampled with a small sample size N, the probability of visiting this energy region is ~ 1/N (shall be exactly 1/N for a single ensemble), which can be orders-of-magnitude larger than the actual DoS. In this work, an assumption of Gaussian distribution is applied to the DoS in each CV bin, and the weight of each configuration is rescaled according to the accumulated DoS. The results show that this smoothing process can remarkably reduce the ruggedness of the PMF and increase the reliability of the reference-potential method.

Sign in / Sign up

Export Citation Format

Share Document