Results 1 - 10 of 9839
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[en] We introduce a small correction term, δMν, in the neutrino sector and examine whether a large θ13 and an almost maximal θ23 can simultaneously be obtained starting from the tri-bimaximal neutrino mixing. It is found that one can easily gain θ13≅10 deg., which is favored by the recent T2K experiment, by taking account of the enhancement due to the degeneracy among three neutrino masses. We also find that (δMν)22=(δMν)33 is a key condition for θ23≅45 deg.
[en] The authors present a progress report on a program to develop a high-power X-band magnicon amplifier for linear accelerator applications. The goal of the program is to generate 50 MW at 11.4 GHz, using a 200 A, 500 keV electron beam produced by a cold-cathode diode on the NRL Long-Pulse Accelerator Facility. The initial experiment, designed to study the gain from the first (driven) deflection cavity to a second (passive) deflection cavity, has been completed. A gain of ∼15 dB has been observed in the preferred circular polarization, at a frequency shift of approximately -0.18%, in good agreement with theory and simulation. In addition, a design study for a complete magnicon circuit is under way
[en] The input-output phase relationships for the doubly degenerate superconducting unbiased parametric amplifier (SUPARAMP) are given. The general analysis is performed for the case when the information is injected into both the signal and idler input channels of the amplifier and the phases of the signal, idler, and pump waves are correlated. The expressions for the phase-dependent power gains are evaluated. The operation for a double-sideband input with symmetry and the usual single-sideband input is treated as a special case. Double-sideband input operation may result in an effective increase of the output signal-to-noise ratio. Another improvement in the signal processing can be achieved by synchronous detection of the SUPARAMP's output
[en] A permanent automatic recalibration system for a scintillation camera, of the type consisting chiefly of a collimator if necessary, a scintillator, a light guide and a network of n photomultipliers coupled to a display system, is described. It uses a device to form a single reference light signal common to all the photomultiplication lines, integrated to these latter and associated with a periodic calibration control generator. By means of associated circuits governed by the control generator the gain in each line is brought to and/or maintained at a value between fixed upper and lower limits. Steps are taken so that any gain variation in a given line is adjusted with respect to the reference light signal common to all the lines. The light signal falls preferably in the same part of the spectrum as the scintillations formed in the scintillator
[fr]On presente un systeme automatique de reetalonnage permanent pour camera a scintillation, du type comportant essentiellement un collimateur eventuel, un scintillateur, un guide de lumiere, un reseau de n photomultiplicateurs couple a un dispositif de visualisation. Il utilise un dispositif de formation d'un meme signal lumineux de reference, pour l'ensemble des voies de photomultiplication, qui est integre a ces dernieres et qui est associe a un generateur de commande periodique d'etalonnage. Des circuits associes sont places sous la dependance du generateur de commande et concus pour (dans chaque voie) ramener et/ou maintenir le gain a une valeur comprise entre les limites inferieure et superieure d'une fourchette. Des dispositions sont prises pour asservir toute modification du gain dans chaque voie, a la prise en compte du seul signal lumineux de reference dans l'ensemble des voies. Le signal lumineux se situe de preference dans la meme partie du spectre que les scintillations formees dans le scintillateur
[en] Highlights: • A four-atom chain encapsulated into a giant fullerene. • The observed clusterfullerene Y2C2@C1(1660)-C108 is computed. • The observed/computed features: near-linear Y2C2 with a near-triple CC bond. • The endohedral stability is related to energy gain upon encapsulation. • The encapsulation energy can presently be calculated but not measured. The very recently prepared clusterfullerene Y2C2@(1660)-C108 is computed and the observed structural features are confirmed, including the quasi-linear arrangement of the encapsulate and its near-triple CC bond. Its stability is explained by sizeable encapsulation energy. The endohedral stability is evaluated at both DFT and MP2 levels.
[en] It is shown that the use of a toothed nozzle array in the active medium generator (AMG) of continuous-wave chemical lasers (CWCLs) allows more efficient mixing of reagents to be achieved in the laser chamber than in an AMG with a slit nozzle array. The results of calculations of parameters of the active medium of a DF CWCL operating in the gain regime for the AMG with traditional and promising nozzle array designs are presented. A kinetic model of processes in the DF CWCL active medium is proposed, which allows obtaining a good agreement with the results of measurements of the small-signal gain. (paper)
[en] The possibilities of separating the fundamental optical mode in composite waveguides by selecting the structure of amplifying regions are analysed. Conditions are presented under which the fundamental mode preserves the highest gain at any saturation. (letters)