Intramode and Fermi relaxation in CO2, their influence on multiple-pass, short-pulse energy extraction

Analytical, experimental and numerical results concerning the influence of intramode and Fermi relaxation on multiple-pass, nanosecond-pulse energy extraction are presented. Multiple-pass energy extraction experiments show satisfactory agreement with the analytical and numerical calculations which predict a significant increase in extracted energy. In three passes, an amount of 9.7 J/l was extracted at an efficiency of 4.3%, These values are taken with respect to the volume of the beam inside the amplifier. In a single pass only 3.5 J/l was extracted

Subnanosecond pulse measurements of 10.6 μm radiation with tellurium

Subnanosecond infrared pulses have been measured by noncollinear secondharmonic generation in tellurium. The method is very practical because due to the high refractive index the fine tuning of the phase matching is easily obtained by rotating the crystal around the optic axis

Fermi and intramode relaxation phenomena in CO2lasers

Using a 1 ns pulse from a short-pulse CO2laser system, the evolution of the gain in a TEA system was studied during and after amplification. This resulted in a very direct observation of a few relaxation processes. We estimated the effective intramode relaxation rate constant to be larger than6 times 10^{6}torr-1/s. The Fermi relaxation time constant was found to be 30 ± 7 ns at 760 torr. We conclude that for nanosecond pulse amplification, intramode relaxation cannot be neglected

Longitudinal change of refraction over at least 5years in 15,000 patients

Background: To report the natural, longitudinal history of shifts in refractive errors in different age groups in a large western European cohort over at least 5years in the same patients. Methods: The electronic database of a large regional clinic containing 225,000 patients was searched for records of patients with a follow-up of at least 5years, excluding all patients who had received any surgical interventions in any eye. This search retrieved 15,799 patients aged 3months to 79years (median 37.8years) with refractive follow up of at least 5years (mean 8.8years) and no surgical interventions. Differences in spherical equivalents (sum of sphere +1/2 cylinder) and cylinder between first and last visit in the same patients in only the right eye were calculated, and used as the measure of refractive shift. Subsequently differences in change between the right and left eye were also determined. Results: Refractions were found to be mostly stable from 25 to 39years (n = 3,155 right eyes), with 50% of these patients not changing their refraction. In patients aged 20-24 (n = 825 right eyes), only 39% of the refractions remained stable, whereas 49% experienced a myopic shift. In the age group 40-69years (n = 6,694), 40-45% remained stable, with an increase in hyperopic shifts. Eighty-five percent of all patients had bilateral symmetric shifts, and 61% showed stable cylindrical values. Conclusions: This report documents clinical relevant changes in spherical equivalents in all age groups within 5 to 10years in the largest examined European cohort. Refractive surgery patients in particular should be selected accordingly, and be informed about the physiological changes which might still occur during their lifetim

Status of the "TEU-FEL" project

The free-electron laser of the TEU-FEL project will be realized in two phases. In phase I the FEL will be driven by a 6 MeV photoelectric linac. In phase II the linac will be used as an injector for a 25 MeV race-track microtron. Information is presented on some technical details and the status of the different subsystems

Proposal for a race-track microtron with high peak current

In order to obtain high gain in a free electron laser a high-quality electron beam with high peak current is required. It is well-known that a microtron is able to produce a high-quality beam having low emittance and small energy spread (1%). Because a circular microtron has a limited high-current capability a race-track design is adopted for providing flexibility, better beam quality and of course higher peak current in the microbunch. Space charge problems may be severe in a microtron. It can be shown that bunching on certain specific subharmonic frequencies will lead to a strong reduction of the space charge problems. The general layout of our microtron design will be presented. The characteristics are: energy 25 MeV, micropulse 10° of the rf frequency of 3 GHz. Our aim is to come beyond the present state of the art with the following characteristics: relative energy spread 0.001, emittance 3 mm mrad, current in the micropulse 100 A, macropulse length 50 μs and subharmonic bunching at 1:64

Acoustic Quality and Health in Urban Environments – The SALVE Project

Background sounds of urban regions have been a concern of architecture and construction engineering for years. In the context of health research however, sound has been restricted to the health risk factor noise, thus reduced to sound decibel levels. Accordingly, noise mitigation measures aim exclusively at the reduction of noise level below a certain threshold. Soundscapes on the other hand, comprise all acoustic events of the natural, physical and human environment, which are determined by sound level, frequency, time and space. Soundscape Ecology which includes the study of spatio-temporal heterogeneity of sounds in different landscapes, provides a suitable methodical approach to analyse the relationships between soundscapes, the built environment and human health. This paper presents SALVE (Acoustic Quality and Health in Urban Environments), a two year interdisciplinary pilot project that started in October 2018 and involves the disciplines of public health and spatial planning. The project aims at the identification of criteria for health-promoting soundscapes in cities. By making year long direct and automated auditory measurements of a robust landuse sample in the city of Bochum, located in the highly urbanized Ruhr Area of Germany, one of the largest multi-seasonal urban soundscape datasets will be generated. These data will be merged with health data from the longitudinal, population-based Heinz Nixdorf Recall (HNR) study. Spatio-statistical models will be further developed to analyse health effects of different types of soundscapes in urban neighborhoods. The project serves as a starting point for an innovative and comprehensive approach to understanding the effects of sound quality on urban public health beyond noise protection. Additionally, knowledge will be gained for the development of solution based health-promoting strategies in spatial planning

Xi Sigma Pi

The Department of Forestry at Iowa State University provides students with countless opportunities, acknowledgments, and awards. The opportunity to gain membership into the national forestry honor society, xi sigma pi, is one such benefit