853 research outputs found
Dedicated multichannel readout ASIC coupled with single crystal diamond for dosimeter application
This paper reports on the tests of a low-noise, multi-channel readout integrated circuit used as a readout electronic front-end for a diamond multi-pixel dosimeter. The system is developed for dose distribution measurement in radiotherapy applications. The first 10-channel prototype chip was designed and fabricated in a 0.18 um CMOS process. Every channel includes a charge integrator with a 10 pF capacitor and a double slope A/D converter. The diamond multi-pixel detector, based on CVD synthetic single crystal diamond Schottky diodes, is made by a 3 Ă— 3 sensor matrix. The overall device has been tested under irradiation with 6 MeV radio therapeutic photon beams at the Policlinico ``Tor Vergata'' (PTV) hospital. Measurements show a 20 fA RMS leakage current from the front-end input stage and a negligible dark current from the diamond detector, a stable temporal response and a good linear behaviour as a function of both dose and dose rate. These characteristics were common to each tested channel
Array of time-of-flight diamond detectors for particle discrimination in laser driven p-11B fusion experiments
The detection of radiation emission in laser induced plasma experiments is an helpful method for gaining information on the physics of laser-matter interaction. Time-of-Flight (TOF) approach is a powerful and effective method to obtain timely spectra of particles accelerated from laser-generated plasma. To this respect, diamond-based detectors are very attractive due to their interesting features such as fast signal collection time, signal proportional to the energy deposited by the incident radiation, blindness to visible radiation, high radiation hardness and low leakage current at room temperature operation. Unfortunately, they cannot supply discrimination on the species of the incoming ions, but only their energies. This may be overcome using specific filtering foils to exploit the different stopping powers of ions of different species and energies. In this work we describe the method to distinguish particles using an array of TOF diamond detectors. A first prototype array, consisting of 2Ă—2 diamond detectors, nominally identical and featuring by aluminum filters of different thicknesses, was developed and preliminary tested at PALS facility in Prague
Rede para construção de conhecimento sobre avaliação de sustentabilidade de agroecossistemas: tornando visĂvel o invisĂvel.
Este trabalho tem como objetivo relatar a estratĂ©gia adotada para fomentar as atividades de Rede de Construção de Conhecimento em Avaliação de Sustentabilidade em Agroecossistemas (Rede Consagro). Essa rede, de âmbito nacional, possui como base a compreensĂŁo da natureza multidimensional do desenvolvimento sustentável como um processo de construção social, e sua origem foi formalizada em dezembro de 2009. A proposta da rede Ă© facilitar a comunicação entre pessoas interessadas em estudos sobre sustentabilidade, procurando incentivar ações de desenvolvimento de atividades relacionadas com o tema e contribuindo para a construção de conhecimento sobre avaliação de sustentabilidade. A consecução desses objetivos será norteada pelos seguintes pressupostos: agroecologia; agroecossistema como unidade básica de análise; e ĂŞnfase em metodologias participativas, na agricultura familiar, e em populações tradicionais e campesinas. A estratĂ©gia para desenvolvimento da rede está baseada na modalidade denominada aprendizado hĂbrido, em que as atividades sĂŁo realizadas por meio de contatos pessoais e uso da informática. SĂŁo apresentados detalhes da estratĂ©gia utilizada e os resultados observados ao longo das atividades; Ă© destacada a aceitação das atividades da rede pelos seus participantes; e Ă© mostrado o caminho futuro, com o incentivo ao uso da rede e a busca de ferramentas de informática que permitam uma ação mais sincronizada entre os atores
Design, realization, and characterization of a novel diamond detector prototype for FLASH radiotherapy dosimetry
Purpose: FLASH radiotherapy (RT) is an emerging technique in which beams with ultra-high dose rates (UH-DR) and dose per pulse (UH-DPP) are used. Commercially available active real-time dosimeters have been shown to be unsuitable in such conditions, due to severe response nonlinearities. In the present study, a novel diamond-based Schottky diode detector was specifically designed and realized to match the stringent requirements of FLASH-RT. Methods: A systematic investigation of the main features affecting the diamond response in UH-DPP conditions was carried out. Several diamond Schottky diode detector prototypes with different layouts were produced at Rome Tor Vergata University in cooperation with PTW-Freiburg. Such devices were tested under electron UH-DPP beams. The linearity of the prototypes was investigated up to DPPs of about 26 Gy/pulse and dose rates of approximately 1 kGy/s. In addition, percentage depth dose (PDD) measurements were performed in different irradiation conditions. Radiochromic films were used for reference dosimetry. Results: The response linearity of the diamond prototypes was shown to be strongly affected by the size of their active volume as well as by their series resistance. By properly tuning the design layout, the detector response was found to be linear up to at least 20 Gy/pulse, well into the UH-DPP range conditions. PDD measurements were performed by three different linac applicators, characterized by DPP values at the point of maximum dose of 3.5, 17.2, and 20.6 Gy/pulse, respectively. The very good superimposition of three curves confirmed the diamond response linearity. It is worth mentioning that UH-DPP irradiation conditions may lead to instantaneous detector currents as high as several mA, thus possibly exceeding the electrometer specifications. This issue was properly addressed in the case of the PTW UNIDOS electrometers. Conclusions: The results of the present study clearly demonstrate the feasibility of a diamond detector for FLASH-RT applications
Produção orgânica de diferentes cultivares de morangueiro cultivados em solo coberto com acĂculas de pĂnus e plástico preto na regiĂŁo de ChapecĂł, SC.
bitstream/item/60636/1/boletim-133.pd
Post-processing of vis, nir, and swir multispectral images of paintings. New discovery on the the drunkenness of noah, painted by andrea sacchi, stored at palazzo chigi (ariccia, rome)
IR Reflectography applied to the identification of hidden details of paintings is extremely useful for authentication purposes and for revealing technical hidden features. Recently, multispectral imaging has replaced traditional imaging techniques thanks to the possibility to select specific spectral ranges bringing out interesting details of the paintings. VIS–NIR–SWIR images of one of the The Drunkenness of Noah versions painted by Andrea Sacchi, acquired with a modified reflex and InGaAs cameras, are presented in this research. Starting from multispectral images we performed post-processing analysis, using visible and infrared false-color images and principal component analysis (PCA) in order to highlight pentimenti and underdrawings. Radiography was performed in some areas to better investigate the inner pictorial layers. This study represents the first published scientific investigation of The Drunkenness of Noah’s artistic production, painted by Andrea Sacchi
Electroluminescence from a diamond device with ion-beam-micromachined buried graphitic electrodes
Focused MeV ion microbeams are suitable tools for the direct writing of
conductive graphitic channels buried in an insulating diamond bulk, as
demonstrated in previous works with the fabrication of multi-electrode ionizing
radiation detectors and cellular biosensors. In this work we investigate the
suitability of the fabrication method for the electrical excitation of colour
centres in diamond. Differently from photoluminescence, electroluminescence
requires an electrical current flowing through the diamond sub-gap states for
the excitation of the colour centres. With this purpose, buried graphitic
electrodes with a spacing of 10 micrometers were fabricated in the bulk of a
detector-grade CVD single-crystal diamond sample using a scanning 1.8 MeV He
micro-beam. The current flowing in the gap region between the electrodes upon
the application of a 250 V bias voltage was exploited as the excitation pump
for the electroluminescence of different types of colour centres localized in
the above-mentioned gap. The bright light emission was spatially mapped using a
confocal optical microscopy setup. The spectral analysis of electroluminescence
revealed the emission from neutrally-charged nitrogen-vacancy centres (,
= 575 nm), as well as from cluster crystal dislocations
(A-band, {\lambda} = 400-500 nm). Moreover, an electroluminescence signal with
appealing spectral features (sharp emission at room temperature, low phonon
sidebands) from He-related defects was detected ( = 536.3 nm,
= 560.5 nm); a low and broad peak around {\lambda} = 740 nm was
also observed and tentatively ascribed to Si-V or GR1 centres. These results
pose interesting future perspectives for the fabrication of
electrically-stimulated single-photon emitters in diamond for applications in
quantum optics and quantum cryptography
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