[en] The design of a device for the formation of a plasma with densities of the order of 10¹² cm^-3 and low temperatures (T_e ∼ 40 eV) is described. For such purpose it was carried out in the device a microwave discharge (f_o = 2.45 GHz) in a resonator of high Q factor, immersed in a static external magnetic field. The device worked in the regime ω_ce ≤ ω_o/2 (ω_ce- cyclotron frequency of the electrons, (ω_o = 2 π f_o) where is possible the excitement of non lineal phenomena of waves transformation. (Author)

[en] The thermoluminescent (TL) properties of amorphous aluminium oxide thin films (thicknesses as low as 0.3 μm) subjected to gamma (Co-60) irradiation are reported. Aluminium oxide thin films were prepared by laser ablation from an Al₂O₃ target using a Nd: YAG laser with emission at the fundamental line. The films were exposed to gamma radiation (Co-60) in order to study their TL response. Thermoluminescence glow curves exhibited two peaks at 110 and 176 C. The high temperature peak shows good stability and 30% fading in the first 5 days after irradiation. A linear relationship between absorbed dose and the thermoluminescent response for doses span from 150 mGy to 100 Gy was observed. These results suggest that aluminium oxide thin films are suitable for detection and monitoring of gamma radiation. (Author)

[en] The interaction of two plasmas generated by laser ablation from two perpendicular carbon (graphite, 99.99% purity) targets was analyzed by optical emission spectroscopy. The 1064 nm line of a Nd:YAG laser was used as energy source. Spatial and temporal measurements were performed. The covered spectral range was from 280 to 740 nm. Time of flight measurements were performed to determine the kinetic energies of different excited species. It was found that the excited species were more energetic; however, their lifetimes were shorter when the two plasmas were interacting. Carbon thin films were deposited at different positions relative to the plasmas and subsequently characterized by scanning electron microscopy and Raman spectroscopy

[en] Electron Cyclotron Resonance (ECR) plasma devices have an important place among the electrode less cold plasma sources, due to their potential applications in industry. Many different devices of this type are now under research around the world. This paper deals with the design description of a microwave ECR plasma source, in which an overdense plasma will be generated, making use of the plasma Eigen modes to induce wave conversion. (Author). 12 refs, 7 figs

[en] The plasmas technology occupies day by day a more important place in the development of new materials, with properties superior to those developed with conventional techniques. Some processes have already been established and are exploited to industrial level. These basically include the plasmas that are generated within discharges of continuous current, as well as those with alternate fields of frequency in the range of radiofrequency (13.6 MHz usually). Nevertheless, the need to increase the efficiency of the work of plasma used, has given as a result the study of plasmas generated to higher frequencies (2.45 GHz), known as ^microwave plasmas^. An important development in the treatment of materials at low pressures and temperature, are those known as microwave discharges of the type of cyclotron resonances of the electrodes, that is, a discharge submerged into a magnetic field. These discharges have the advantage of not including electrodes, they can generate plasmas with higher density of ionized and excited particles, can work under low pressures (∼ 1m Torr), and have higher ionizing coefficient (∼ 1%), than other kind of discharge. With the aim to study the accuracy in work of the microwave discharges in magnetic fields, the National Institute of Nuclear Research (ININ) designed and built a gadget of this type which is actually used in the formation of thin films of the diamond type and of amorphous silicon. At the same time, experiments for nitrating steels, in order to establish the mechanisms that would allow to build samples, with surfaces stronger and resistant to corrosion, at short-time treatments, than those needed, when using other kinds of discharges. (Author)

[en] Our Novillo Tokamak is a small toroidal device magnetically confined defined by the main design parameters: R_o=0.23 m, a_v=0.08 m, a_p=0.06 m, B_T=0.05-0.47 T, I_p=1-12 kA, n_e=1-2x10¹³ cm^-3, T_e=150 eV, T_i=50 eV. For the initial discharge chamber cleaning we have often used vacuum baking up to 100 deg. C and then conditioning using Taylor discharge cleaning (TDC) in H₂ and He. In this work we report that vacuum baking is effective for obtaining a final total pressure of the order of 1.6x10^-7 Torr. We have found that a single parameter, the performance parameter (PP), can be used to optimize the TDC method. This parameter represents the quantity of electron and ion energy incident on the chamber wall during the Taylor discharge, it is equal to (I_pτ), where I_p is the peak-to-peak plasma current and τ is the plasma current duration. In graphs of PP versus the gas pressure for different oscillator powers, the maximum value of PP indicates the best cleaning conditions when using TDC. The results of the vacuum chamber wall conditioning using this criterion are reported

[en] The thermoluminescence (TL) properties of amorphous aluminum oxide thin films subjected to ultraviolet (UV) irradiation are reported. Aluminum oxide thin films were prepared by laser ablation from an α-Al₂O₃ target using Nd:YAG laser with emission at the fundamental line. Compositional, structural and morphological properties of the obtained thin films as a function of the growth conditions have been studied. Experimental results show that amorphous aluminum oxide thin films with atomic concentrations of aluminum and oxygen close to those of stoichiometric Al₂O₃ and with splashed particles on its surface were obtained. The TL response as a function of the growth parameters has been investigated in order to improve such response. Thermoluminescence glow curves exhibited one peak centered at 174 deg. C. The results presented in this work, shows that it is possible to obtain materials in thin film form with thickness as low as 150 nm, which exhibits TL response to UV irradiation. These results suggest that aluminum oxide thin films are suitable for detection and monitoring of UV light

[en] The main thermoluminescence properties of amorphous aluminum oxide thin films prepared by pulsed laser deposition with thickness as low as 300 nm are presented. The obtained thin films were irradiated with UV (254 nm) and beta-particle radiation (⁹⁰Sr-⁹⁰Y). Thermoluminescence glow curves exhibited two peaks centered at 95 deg. C and 162 deg. C for UV irradiation. For beta-particle irradiation the thermoluminescence glow curve shows only the presence of the high temperature peak. The 162 deg. C peak shows good stability and 10% fading in the first 4 days after irradiation. A linear relationship between absorbed dose and the thermoluminescence response up to 20 Gy was observed for beta-particle irradiation. The thermoluminescence parameters obtained showed a second-order kinetics and an activation energy of 1.2 eV for the 162 deg. C peak. These properties make aluminum oxide thin films potentially attractive as an ultra-thin dosimeter for UV and beta-particle radiation

No abstract available

[en] By means of the laser ablation technique has been settled thin films of aluminium oxide on kapton substrates. These films present thermoluminescent response (Tl) when being exposed to beta radiation of a Sr⁹⁰ - Y⁹⁰ source (E max = 2.28 MeV). The brilliance curves show two peaks, one of them in 112 C degrees and the other one in 180 C degrees. The peak of low temperature is faded in some hours, whereas the high temperature one is more stable, showing a fading in the 15% order after three days of the irradiation. The Tl kinetic parameters were determined using the computerized deconvolution of the brilliance curve (CGDC). The results show that the high temperature peak is composed by four peaks which obey a second order kinetics with their maximum located at 165.7, 188.1, 215.3, and 246.5 C degrees. The depth of the traps (E) has values in the interval between 1.4 and 2.0 eV. The study of the dose response relation, show that the material presents a linear behavior in a dose interval from 150 mGy to 50 Gy. The obtained thin films of aluminium oxide could be a useful tool due to their potential applications in clinical dosimetry, in the determination of distributions of doses produced by penetrating weakly radiation, as well as in interfaces dosimetry. (Author)