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Second-order nonlinear optical (SO-NLO) properties of group 8 half-sandwich organometallic complexes have been intensively studied throughout the last 15 years, making this class of compounds relevant for the continuous search of NLO materials. This contribution surveys the ongoing efforts to design, characterize and optimize the NLO properties of this class of compounds. Computational studies, namely DFT calculations, were performed for several model molecules in order to predict the first hyperpolarizabilities and to support experimental evidences. [ABSTRACT FROM AUTHOR]

Fluorescent screens are widely used for purposes of beam diagnostics in particle accelerators. When the screen intercepts the beam, it produces visible light, generating an image that can be visualized using CCD cameras. However, these materials are subject to saturation, when an increase in the beam charge is not followed by a proportional increment in the light emission. In this work we discuss how charge saturation influences the observation of charge distribution. Systematic errors are induced since the experimenter observes the beam wider than it actually is. Closer attention is given to gaussian distributions, but some other shapes are also discussed. An algorithm to correct beam diameter measurement is suggested and composite measurements are discussed. This study is relevant to improve the quality of the beam information provided to users. [ABSTRACT FROM AUTHOR]

Transition Radiation (TR) is a physical process in which a uniformly moving charge emits radiation. For emission to occur, it is necessary a variation of the electromagnetic properties of the media that surrounds the particle. The main characteristics of this kind of radiation are: linearity between the radiation intensity and the generating charge, polarization and formation time. The continuous spectrum covers a wide wavelength range, including visible light (Optical Transition Radiation-OTR). These characteristics make OTR an excellent tool for beam diagnostics in particle accelerators. In this work we discuss the role OTR plays in beam instrumentation and the progress of the undergoing project of an OTR based diagnostic tool for the IFUSP Microtron. This is an innovative design since it is planned to be used to diagnose a low energy and low current electron beam. [ABSTRACT FROM AUTHOR]

The first accelerating structures of the São Paulo microtron accelerator presently deliver a continuous-wave 1.9 MeV electron beam, which can be used in atomic physics studies. An energy-analyzed beam line with focalization magnets, irradiation chamber, movable target system and Faraday cup was built. Here, we will describe the preliminary results of two experiments. In the first one, upper limits on K-shell ionization cross sections of Pd and Au atoms by electron impact were obtained. To this end, thin targets of these elements were irradiated with the beam impinging at 45° while the emitted Kα x-rays were recorded with an HPGe x-ray detector positioned at 90° with respect to the beam direction. The other experiment was the measurement of the bremsstrahlung energy spectra produced by the aforementioned targets in the same geometrical configuration but using an HPGe γ-ray detector instead. The latter experiment enabled the determination of the electron-beam energy as 1.909(5) MeV. [ABSTRACT FROM AUTHOR]

The Laboratório do Acelerador Linear is building a racetrack microtron electron accelerator. It has two acceleration stages: the booster and the main microtron. The aim of this work is to optimize the operation parameters of the booster stage by means of simulation tools. The accelerator admittances were determined successfuly and the results are presented. The injection beam has been characterized previously, and the available data were used to match the transverse beam emittances of the injector to the transverse beam admittances of the booster. Preliminary results showed that the simulations have a good agreement with the working parameters. [ABSTRACT FROM AUTHOR]

This work describes a computer algorithm for automatic extraction of the energy calibration parameters from a Rutherford Back-Scattering Spectroscopy (RBS) spectrum. Parameters like the electronic gain, electronic offset and detection resolution (FWHM) of a RBS setup are usually determined using a standard sample. In our case, the standard sample comprises of a multi-elemental thin film made of a mixture of Ti-Al-Ta that is analyzed at the beginning of each run at defined beam energy. A computer program has been developed to extract automatically the calibration parameters from the spectrum of the standard sample. The code evaluates the first derivative of the energy spectrum, locates the trailing edges of the Al, Ti and Ta peaks and fits a first order polynomial for the energy-channel relation. The detection resolution is determined fitting the convolution of a pre-calculated theoretical spectrum. To test the code, data of two years have been analyzed and the results compared with the manual calculations done previously, obtaining good agreement. [ABSTRACT FROM AUTHOR]

There is a great need to quantify sub-ppm levels of boron in bulk silicon. There are several methods to analyze B in Si: Nuclear Reaction Analysis using the 11B(p,α0)8Be reaction exhibits a quantification limit of some hundreds ppm of B in Si. Heavy Ion Elastic Recoil Detection Analysis offers a detection limit of 5 to 10 at. ppm. Secondary Ion Mass Spectrometry is the method of choice of the semiconductor industry for the analysis of B in Si. This work verifies the use of NRA to quantify B in Si, and the corresponding detection limits. Proton beam with 1.6 up to 2.6 MeV was used to obtain the cross-section of the 11B(p,α0)8Be nuclear reaction at 170° scattering angle. The results show good agreementwith literature indicating that the quantification of boron in silicon can be achieved at 100 ppm level (high sensitivity) at LAMFI-IFUSP with about 16% uncertainty. Increasing the detection solid angle and the collected beam charge, can reduce the detection limit to less than 100 ppm meeting present technological needs. [ABSTRACT FROM AUTHOR]