Results 1 - 10 of 1849
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[en] Wall shift limits the actual accuracy of the hydrogen maser to 10-12. After a review of the perturbation of the hydrogen atoms upon collision on the surface of teflon coated bulb, a new approach is proposed in which a teflon cylinder replaces the classical storage bulb. In this case a more reproducible wall shift is expected. (author)
[en] An experimental verification of Einstein's equivalence principle has been made using an atomic hydrogen maser in a space probe attaining an altitude of 10,000 km above the earth's surface. At the present stage of the data reduction, confirmation is at the 2 x 10-4 level of accuracy. The experiment and the resulting data are described including a comment on the limits to the anisotropy of the velocity of light. It is believed that this is the first direct, high-accuracy test of the symmetry of the propagation of light and a beginning in the use of high-accuracy clocks in space to measure relativistic phenomena. (author)
[en] In this work a synthesis method is applied to the design of an electron gun for a 94GHz gyrotron. Using the synthesis method, it is found the shape of the electrodes compatible with the laminar flow which minimizes the action of space change on the electron velocity dispersion. A sistematic procedure is presented to fuid the parameters of the synthesis method which, in turn, are closely related to the characteristics of the aptoclechonic system. (author)
[pt]Neste trabalho aplica-se o metodo de sintese ao projeto de um canhao de eletrons para um giratron de 94GHz. Usando o metido de sintese determina-se a forma dos eletrodos compativeis com o escoamento laminar que, deste modo, minimiza a acao da carga espacial sobre a dispersao de velocidade dos eletrons. Apresenta-se um procedimento sistematico para determinar os parametros do metodo de sintese que, por sua vez estao intimamente relacionados com as caracteristicas do sistema eletro optico. Finalmente projeta-se um canhao de eletrons cuja dispersao de velocidade obtida e da ordem de 1,5% e cuja potencia de feixe e de 2,3 MW. (autor)
[en] Aleksandr Mikhailovich Prokhorov was a Russian physicist, academician, one of the originators of quantum electronics, laser physics and laser technologies, winner of the 1964 Nobel Prize in Physics 'for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser – laser principle' (shared with N.G. Basov and Ch.H. Townes), Lenin Prize and State Prize winner and twice Hero of Socialist Labour. (personalia)
[en] There is reason to believe that the physical conditions in many astrophysical masers are far from homogeneous. In particular, if the maser pump involves the absorption of infrared photons, the pump rate may vary rapidly (perhaps exponentially) across the cloud. The consequences of such variation of the pump rate for the maser radiation are calculated, and it is shown that there are substantial asymmetries in the output of the maser. A general result is that the maser radiation is preferentially emitted back toward the source of pump radiation. The implication of this result for the interpretation of the circumstellar 1612 MHz OH masers is briefly discussed. 14 references
[en] Positions of 65 OH maser sources obtained with the 100-m radio telescope are presented. The positional accuracy is typically 10'', a conservative estimate for sources stronger than approx.10 Jy. The emphasis of this work was on OH/IR sources and 51 of the objects are certain type II OH/IR sources, of which only one (GX Mon) is associated with an optically known star. Three of the sources show only one 1612-MHz line component and these are probably also OH/IR sources but with a large ratio between the intensities of the high- and low-velocity components. Six of the objects are certain type I OH sources, i.e., maser emission associated with recently formed massive stars, and five more are probably of this type, although in some of these cases the 1612-MHz line is stronger than one of the main lines. This work has incidentally revealed (i) that the 1665-MHz emission which previously was assumed to be positionally coincident with the 1720-MHz emission of the source ON-3 originates approx.2.'3 to the southwest of the interferometrically determined 1720-MHz position, and (ii) that to within the positional accuracy, the position of the 1612-MHz emission from the core of the Kleinmann--Low nebula (Orion) is the same as that of the 1665-MHz emission; (iii) that the position of the 1667-MHz emission from VX Sgr is the same as that of the 1612-MHz emission; and (iv) that the position of the 1612-MHz emission from W 3(OH) is the same as that of the 1665/1667-MHz emission
[en] Two outstanding problems in the interpretation of OH masers are their narrow linewidths, and the rare occurrence of Zeeman pairs. In the Cook-Shklovskii model, if the magnetic field and the bulk velocity of the gas along the line of sight vary, the gradients in Zeeman shift and Doppler shift may match to keep only one component in resonance with the molecules for a significant distance. With this interpretation a Zeeman pair would be expected from a given region only when the relevant gradients are negligible. Some implications of this model were studied. The condition under which only one Zeeman component may be seen was derived and was shown to be satisfied at least for the source W3(OH). The model does not allow any line-narrowing but implies a broadening of features during saturated growth
[en] The analytical form of the emission probability produced by the interaction of an ultracold three-level atom with an electromagnetic bimodal cavity field with multi-photon transitions of the atoms (multi-photon mazer) is analysed in the framework of the dressed-state formalism, but is distinguished from other treatments by the inclusion of the spatial variation along the cavity axis. In particular, the cavity field mode profile is considered by using the mesa-mode function and differences in the collapse-revival patterns are reported. We demonstrate that, when propagation effects are taken into consideration, the emission probability is influenced significantly. We provide the necessary arguments to justify the validity of our conclusions for emission probability and the micromaser, whose dynamics are governed by the wavefunction. Our main conclusion is that, in the present system, the inclusion of the spatial dependence is necessary and important. The numerical illustrations provide evidence that, in cases of physical interest, the emission probability can be significant and can be reliably estimated for a broad range of field parameters using the present formalism
[en] A coaxial localized-defect Bragg resonator has potential applications in high-power CARM oscillators. When it operates at sub-terahertz and terahertz frequencies, a higher-order mode is always required so as to get enough large geometry size. Analysis shows that higher-order mode operation may cause undesired mode competition due to the localized defect coupling the operating mode with its neighboring modes. A simple but efficient method is presented to solve the mode competition problem, where Hamming windowing-function distribution is separately applied to both sides of the localized defect.
[en] We report multi-frequency Very Large Array observations of three massive star formation regions (MSFRs) containing radio continuum components that were identified as broad radio recombination line (RRL) sources and hypercompact (HC) H II region candidates in our previous H92α and H76α study: G10.96+0.01 (component W), G28.20-0.04 (N), and G34.26+0.15 (B). An additional HC H II region candidate, G45.07+0.13, known to have broad H66α and H76α lines, small size, high electron density, and emission measure, was also included. We observed with high spatial resolution (0.''9-2.''3) the H53α, H66α, H76α, and H92α RRLs and the radio continuum at the corresponding wavelengths (0.7-3.6 cm). The motivation for these observations was to obtain RRLs over a range of principal quantum states to look for signatures of pressure broadening and macroscopic velocity structure. We find that pressure broadening contributes significantly to the linewidths, but it is not the sole cause of the broad lines. We compare radio continuum and dust emission distributions and find a good correspondence. We also discuss maser emission and multi-wavelength observations reported in the literature for these MSFRs.