HIGH BRIGHTNESS BEAMS — APPLICATIONS TO FREE-ELECTRON LASERS

2007 ◽  
Vol 22 (22) ◽  
pp. 3912-3924
Author(s):  
SVEN REICHE
Keyword(s):  
Free Electron ◽  
Beam Quality ◽  
Beam Parameter ◽  
Free Electron Lasers ◽  
High Quality ◽  
High Brightness ◽  
Radiation Sources ◽  
Beam Parameters ◽  
The Impact

Free-Electron Lasers as high-brilliance radiation sources, rely on a high quality of the electron beam driving the FEL process. The amount of energy, transferred from the electrons to the radiation field, and thus the efficiency of the FEL depends on the provided beam parameters. The presentation discusses the impact of various beam parameter and how current designs of FEL injector try to accomplish the demands on the beam quality for reaching saturation.

scholarly journals Matrix model for collective phenomena in electron beam’s longitudinal phase space

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Giovanni Perosa ◽  
Simone Di Mitri
Keyword(s):  
Free Electron ◽  
Analytical Models ◽  
Free Electron Lasers ◽  
Linear Accelerators ◽  
Transfer Lines ◽  
High Brightness ◽  
Harmonic Content ◽  
Intrabeam Scattering ◽  
Beam Parameters ◽  
The Impact

AbstractThe possibility to predict, characterize and minimize the presence of spurious harmonic content in the longitudinal profile of high brightness electron beams, namely the microbunching instability, has become vital to ensure accurate modeling and reliable operation of radiofrequency and plasma-based linear accelerators such as those driving free-electron lasers. Recently, the impact of intrabeam scattering (IBS) on the instability has been experimentally demonstrated by the authors. This work complements that experimental study by extending existing theories in a self-consistent, piece-wise calculation of IBS in single pass linacs and multi-bend transfer lines. New expressions for the IBS are introduced in two different semi-analytical models of microbunching. The accuracy of the proposed models and the range of beam parameters to which they apply is discussed. The overall modeling turns out to be a fast comprehensive tool for the optimization of linac-driven free-electron lasers.

Radiation of Charge Moving Between Two Planar Periodic Wire Structures

2020 ◽  
Vol 23 (1) ◽  
pp. 66-71
Author(s):  
E. A. Gurnevich ◽  
I. V. Moroz
Keyword(s):  
Angular Distribution ◽  
Charged Particle ◽  
Research And Development ◽  
High Power ◽  
Free Electron ◽  
Radiation Intensity ◽  
Free Electron Lasers ◽  
Radiation Sources ◽  
Power Radiation ◽  
High Power Radiation

The Smith-Purcell radiation of a charged particle moving in a periodic structure is analysed theoretically. The considered structure consists of two planar diffraction gratings with different periods which are formed by parallel conducting wires. The analytical expression for the spectral-angular distribution of radiation is obtained. It is shown that the angular distribution of radiation can be made narrower by using two gratings instead of one, and radiation intensity can be manipulated by parallel relative shift of gratings. The obtained results are of great importance for the research and development of high power radiation sources based on volume free-electron lasers.

scholarly journals How Different Fermentation Type Affects Volatile Composition of Plum Jerkums

2021 ◽  
Vol 11 (10) ◽  
pp. 4658
Author(s):  
Magdalena Januszek ◽  
Paweł Satora
Keyword(s):  
Volatile Compounds ◽  
Current Paper ◽  
Higher Alcohols ◽  
High Quality ◽  
Volatile Composition ◽  
Spontaneous Fermentation ◽  
Fermentation Efficiency ◽  
Yeast Strains ◽  
The Impact

Quality of plum jerkum is significantly associated to the profile of volatile compounds. Therefore, we decided to assess the impact of various fermentation types on selected properties of plum jerkums, especially compounds which contribute to the aroma of the finished product. We used the following yeast strains: S. cerevisiae S1, H. uvarum H2, and Ethanol RED (S. cerevisiae). Moreover, we considered spontaneous fermentation. S. cerevisiae and H. uvarum strains were isolated during the fermentation of Čačanska Lepotica or Węgierka Dąbrowicka (plum cultivars), respectively. As for fermentation type, spontaneous fermentation of H. uvarum H2 provided the best results. It could be associated to the fact that plum juices fermented with H. uvarum H2 presented the highest concentration of terpenoids, esters, or some higher alcohols. In the current paper, application of indigenous strains of yeasts resulted in the required oenological characteristics, e.g., highest fermentation efficiency and concentration of ethanol was determined in juices fermented with Ethanol RED (S. cerevisiae) and also with S. cerevisiae S1. Our results suggested that indigenous strains of yeasts present in plums demonstrate great potential for the production of plum jerkums of high quality.

scholarly journals Health-Related Quality of Life of Elderly Women with Fall Experiences

2021 ◽  
Vol 18 (15) ◽  
pp. 7804
Author(s):  
Jiyoung Song ◽  
Eunwon Lee
Keyword(s):  
Quality Of Life ◽  
Elderly Women ◽  
The Elderly ◽  
Basic Data ◽  
Health Related Quality ◽  
High Quality ◽  
Related Quality ◽  
Health Related ◽  
The Impact

This study aimed to describe the health-related quality of life of elderly women with experience in fall treatment as well as to prepare basic data for the development of interventions to improve the quality of life for this group. The study was based on raw data from the 2019 Korea Community Health Survey. Using the SPSS program, the characteristics of the subjects were tested by frequency, percentage, and chi-square test. To establish the impact of fall experience on the health-related quality of life of elderly women, the OR and 95% CI were calculated using multiple logistic regression analysis. Of the 4260 people surveyed, 44.7% of the elderly women said they had a high quality of life, whereas 55.3% of the elderly women said they had a low quality of life. A younger age was associated with a better-rated health-related quality of life. Those who lived in a city and had a high level of education tended to describe a high quality of life. The quality of life was considered high by those who exercised, but low by those who were obese or diabetic. The results of this study can lead to a better understanding of the experiences of elderly women who have experienced falls, and they can be used as basic data for the development of related health programs.

Analytical account for off-axis effects in X-ray radiation of free electron lasers

2021 ◽  
Vol 64 (1) ◽  
pp. 21-28
Author(s):  
K.V. Zhukovsky ◽  
Keyword(s):  
Free Electron ◽  
Finite Size ◽  
Photon Radiation ◽  
Beam Parameter ◽  
Beam Size ◽  
Free Electron Lasers ◽  
Airy Functions ◽  
X Ray ◽  
Harmonic Radiation ◽  
Gain Length

We give analytical description of generation of harmonics of the undulator radiation (UR) with account for the finite electron beam size, emittance, off-axis beam deviation and electron energy spread, as well as for the constant magnetic components and field harmonics effects. We give exact analytical expressions for the generalized Bessel and Airy functions, which describe the spectrum line shape and intensities in the two-frequency bi-harmonic undulator with account for the above factors. The obtained analytical formulae distinguish contributions of each field component and every undulator and beam parameter on the harmonic radiation in free electron lasers (FEL). The effect of the field on the harmonic radiation is analyzed with account for the beam finite size and its off-axis deviation. The phenomenological model is employed for the FEL modeling; with its help we study the harmonic generation, including even ones, in the experiments LCLS and LEUTL. We demonstrate analytically that strong second FEL harmonic in X-ray FEL at the wavelengths λ = 0.75nm in the LCLS experiment is caused by the deviation of the electron trajectories off the axis in 15 μm on the gain length 1.6 m, which is comparable with the beam size; the strong second FEL harmonic in the LEUTL experiment at the wavelength λ = 192nm can be attributed to interaction of the electrons in wide, ~ 0.2 mm, beam with the photon radiation at the gain length 0.87 m. The modeling results fully agree with the measurements. The developed formalism allows the analysis of projected and built FELs and their radiation, helps minimizing losses and correcting magnetic fields; it also shows physical background and reasons for each harmonic radiated power in the FEL.

scholarly journals An Adaptive Bitrate Switching Algorithm for Speech Applications in Context of WebRTC

2021 ◽  
Vol 17 (4) ◽  
pp. 1-21
Author(s):  
Mohannad Alahmadi ◽  
Peter Pocta ◽  
Hugh Melvin
Keyword(s):  
Real Time ◽  
Data Exchange ◽  
Quality Of Experience ◽  
End User ◽  
High Quality ◽  
Content Type ◽  
Switching Algorithm ◽  
Wide Range ◽  
The Impact

Web Real-Time Communication (WebRTC) combines a set of standards and technologies to enable high-quality audio, video, and auxiliary data exchange in web browsers and mobile applications. It enables peer-to-peer multimedia sessions over IP networks without the need for additional plugins. The Opus codec, which is deployed as the default audio codec for speech and music streaming in WebRTC, supports a wide range of bitrates. This range of bitrates covers narrowband, wideband, and super-wideband up to fullband bandwidths. Users of IP-based telephony always demand high-quality audio. In addition to users’ expectation, their emotional state, content type, and many other psychological factors; network quality of service; and distortions introduced at the end terminals could determine their quality of experience. To measure the quality experienced by the end user for voice transmission service, the E-model standardized in the ITU-T Rec. G.107 (a narrowband version), ITU-T Rec. G.107.1 (a wideband version), and the most recent ITU-T Rec. G.107.2 extension for the super-wideband E-model can be used. In this work, we present a quality of experience model built on the E-model to measure the impact of coding and packet loss to assess the quality perceived by the end user in WebRTC speech applications. Based on the computed Mean Opinion Score, a real-time adaptive codec parameter switching mechanism is used to switch to the most optimum codec bitrate under the present network conditions. We present the evaluation results to show the effectiveness of the proposed approach when compared with the default codec configuration in WebRTC.

scholarly journals A study of the impact of information disclosure quality on the efficiency of corporate investment—Based on civil engineering listed companies

2020 ◽  
Vol 198 ◽  
pp. 03032
Author(s):  
Liying Zhang
Keyword(s):  
Life Cycle ◽  
Civil Engineering ◽  
Listed Companies ◽  
Investment Efficiency ◽  
Disclosure Quality ◽  
High Quality ◽  
Life Cycle Stages ◽  
Quality Disclosure ◽  
The Impact

Most of the existing studies on the impact of disclosure quality of listed companies on the investment efficiency of enterprises are based on the static level, and the article investigates the evolution of disclosure quality on the investment efficiency of enterprises from the dynamic level by dividing the life cycle of enterprises. Taking the data of Shenzhen civil engineering companies from 2013-2017 as the research sample, it uses multiple regression analysis to empirically test the impact of disclosure quality of listed companies on the investment efficiency of enterprises at different life cycle stages. The results show that when no distinction is made between life cycle stages, high quality disclosure can significantly inhibit the inefficient investment behavior of firms; in the growth and maturity samples, high quality disclosure can significantly inhibit underinvestment and overinvestment; in the recessionary samples, high quality disclosure can significantly inhibit underinvestment and has no significant effect on overinvestment.

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