A model of the reflection distribution in the vacuum ultra violet region

A reflection model with three components, a specular spike, a specular lobe and a diffuse lobe is discussed. This model was successfully applied to describe reflection of xenon scintillation light (175 nm) by PTFE and other fluoropolymers and can be used for Monte Carlo simulation and analysis of scintillation detectors. The measured data favors a Trowbridge-Reitz distribution function of ellipsoidal micro-surfaces. The intensity of the coherent reflection increases with increasing angle of incidence, as expected, since the surface appears smoother at grazing angles. The total reflectance obtained for PTFE is about 70% for VUV light at normal incidence in vacuum and estimated to be up to 100% in contact with liquid xenon

Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Fluoropolymers, namely ETFE, FEP and PFA were also measured

Componentes do balanco de energia em pomar irrigado no Nordeste.

Results of an energy balance based on the Bowen ratio method are presented. Two field experiments were carriedout in 1998 and 1999, with a mango orchard in Petrolina, PE. The mango trees were irrigated by a drip irrigationsystem. A micrometeorology tower was set up for installation of the instruments used for the energy balance,which are: net radiation, two psychrometers and two anemometers installed in two levels above the canopy of theculture, and more two radiometers (global solar radiation and the radiation reflected by the culture). Two plates formeasuring the soil heat flux in a depth of 5 cm were installed. The analog signals of all instruments were scannedonce every five seconds and averaged every 10 minutes using a micrologger. It was verified that didn't happengreat differences among the components of the energy balance in relation to the two experiments. In general, thelatent heat flux was of the order of 80% of Rn, while H and G represented around 15% and 5% of Rn, respectively.Such relationships were analyzed in different phenological phases, as well as the seasonal behavior of the energybalance component

Balanço de radiação na cultura da mangueira.

O presente trabalho objetivou a avaliação dos componentes do balanço de radiação sobre um cultivo demangueira, variedade Tommy Aktins, fertirrigado por gotejamento como parte de estudo do consumo hídrico evisando futuras aplicações no manejo de irrigação da cultura na região do submédio São Francisco

Influência de duas intensidades de exploração no crescimento da floresta residual.

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Energy balance in a mango orchard in Northeast of Brazil.

The main objective of this research was the determination of the energy balance in a mango orchard

Alguns aspectos fisiologicos da mangueira em condicoes irrigada e de estresse hidrico.

Este estudo analisou medidas porométricas feitas em um pomar de manga, variedade Tommy Atkins, plantado em Fevereiro de 1993, e irrigado por gotejamento no campo experimental da Embrapa Semi-Árido em Petrolina, PE, Brasil (Latitude: 090 09`S, Longitude: 400 22`W; altitude: 365,5m), usando um porômetro de difusão, LI - 1600 (Licor, EUA)

Balanço hídrico climático de Juazeiro - BA.

O objetivo desse trabalho foi realizar o balanço hídrico climático de Juazeiro-BA, no período de 1967 a1998, gerando uma idéia do que acontece com boa parte da região semi-árida, no que diz respeito a disponibilidadede água, observando-se ainda a tendência climática temporal da região

Scintillation efficiency of liquid xenon for nuclear recoils with the energy down to 5 keV

The scintillation efficiency of liquid xenon for nuclear recoils has been measured to be nearly constant in the recoil energy range from 140 keV down to 5 keV. The average ratio of the efficiency for recoils to that for gamma-rays is found to be 0.19+-0.02.Comment: 13 pages, 5 figure

Water consumption and energy balance in mango tree orchard at a tropiccal station.

Otherwise it includes both quantity of water a tree uses and the timing of water applications