We present a theoretical model of spin transitions in stacks of molecular layers. Our model captures the already established physics of these systems (thermal hysteretic transitions and crossovers) ...and suggests a way towards in situ control of this physics by means of an external electric field. Our results pave the way toward both temperature and voltage controllable organic memory.
Spherical neutral detector for VEPP-2M collider Achasov, M.N; Aulchenko, V.M; Baru, S.E ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2000, Letnik:
449, Številka:
1
Journal Article
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The Spherical Neutral Detector (SND) operates at VEPP-2M collider in Novosibirsk studying e
+e
− annihilation in the energy range up to 1.4
GeV. Detector consists of a fine granulated spherical ...scintillation calorimeter with 1632 NaI(Tl) crystals, two cylindrical drift chambers with 10 layers of sense wires, and a muon system made of streamer tubes and plastic scintillation counters. The detector design, performance, data acquisition and processing are described.
The ATLAS experiment at the Large Hadron Collider employs a two-level trigger system to record data at an average rate of 1 kHz from physics collisions, starting from an initial bunch crossing rate ...of 40 MHz. During the LHC Run 2 (2015–2018), the ATLAS trigger system operated successfully with excellent performance and flexibility by adapting to the various run conditions encountered and has been vital for the ATLAS Run-2 physics programme. For proton-proton running, approximately 1500 individual event selections were included in a trigger menu which specified the physics signatures and selection algorithms used for the data-taking, and the allocated event rate and bandwidth. The trigger menu must reflect the physics goals for a given data collection period, taking into account the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout, online processing farm, and offline storage. This document discusses the operation of the ATLAS trigger system during the nominal proton-proton data collection in Run 2 with examples of special data-taking runs. Aspects of software validation, evolution of the trigger selection algorithms during Run 2, monitoring of the trigger system and data quality as well as trigger configuration are presented.
The conversion decays
φ→
ηe
+
e
− and
η→
γe
+
e
− were studied by the SND detector using
φ-meson production in
e
+
e
−-annihilation at VEPP-2M collider. The branching ratios of these decays were ...measured:
Br(
φ→
ηe
+
e
−)=(1.19±0.19±0.07)×10
−4 and
Br(
η→
γe
+
e
−)=(5.15±0.62±0.39)×10
−3. The
e
+
e
−-pair mass spectra and transition form factors were also studied.
The process e(+)e(-)-->mu(+)mu(-) has been studied by the SND detector at the VEPP-2M e(+)e(-) collider in the phi(1020)-resonance energy region. The measured effective phi meson leptonic branching ...ratio B(phi-->l(+)l(-)) identical with square root of B(phi-->e(+)e(-))B(phi-->mu(+)mu(-)) = (2.89 +/- 0.10 +/- 0.06) x 10(-4) agrees well with the Particle Data Group value B(phi-->e(+)e(-)) = (2.91 +/- 0.07) x 10(-4), confirming mu-e universality. Without additional assumption of mu-e universality the branching ratio B(phi-->mu(+)mu(-)) = (2.87 +/- 0.20 +/- 0.14) x 10(-4) was obtained.
The paper deals with results of the study on the main technological aspects relating to a full production cycle of silica multimode graded-index fibers with the refractive index profile having ...central defect in the form of a large dip. Preform synthesis conditions for implementation of the mentioned defect via MCVD method have been analyzed and optimized. We have carried out research of the effect of geometrical irregularities, induced by drawing optical fibers under the manual control of the outer diameter stability, on attenuation coefficient of the graded-index 50/125 μm optical fibers with a large dip in the center of the refractive index profile. It is shown that variations of the outer diameter within the limits ± 3.5 μm lead to an increase of attenuation by 2–5 dB/km at the wavelength λ = 1310 μm as compared to the optical fibers fabricated under the automatic maintenance of the outer diameter stability. It has been determined that in the latter case fibers with the parabolic refractive index profile, corresponding to numerical aperture of 0.20, and the dip depth equal to 0.0115 demonstrate the attenuation about 5 dB/km in the second and third optical fiber transmission windows. Applying the Weibull distribution, a statistical evaluation of mechanical properties of the optical fibers drawn at various temperatures has been carried out. Based upon measurements, tensile strength of the fibers was estimated to be 5.07–5.49 GPa, that is comparable with the strength properties of silica telecom fibers. The manufactured multimode fibers are attractive candidates for developing sensing elements of registering external influences in systems of fiber-optic sensor networks based on few-mode effects.
The paper deals with results of the study on the main technological aspects relating to a full production cycle of silica multimode graded-index fibers with the refractive index profile having ...central defect in the form of a large dip. Preform synthesis conditions for implementation of the mentioned defect via MCVD method have been analyzed and optimized. We have carried out research of the effect of geometrical irregularities, induced by drawing optical fibers under the manual control of the outer diameter stability, on attenuation coefficient of the graded-index 50/125 μm optical fibers with a large dip in the center of the refractive index profile. It is shown that variations of the outer diameter within the limits ± 3.5 μm lead to an increase of attenuation by 2-5 dB/km at the wavelength λ = 1310 μm as compared to the optical fibers fabricated under the automatic maintenance of the outer diameter stability. It has been determined that in the latter case fibers with the parabolic refractive index profile, corresponding to numerical aperture of 0.20, and the dip depth equal to 0.0115 demonstrate the attenuation about 5 dB/km in the second and third optical fiber transmission windows. Applying the Weibull distribution, a statistical evaluation of mechanical properties of the optical fibers drawn at various temperatures has been carried out. Based upon measurements, tensile strength of the fibers was estimated to be 5.07-5.49 GPa, that is comparable with the strength properties of silica telecom fibers. The manufactured multimode fibers are attractive candidates for developing sensing elements of registering external influences in systems of fiber-optic sensor networks based on few-mode effects.
This paper investigates the possibilities of creating magnetic field sensors using the direct magnetoelectric (ME) effect in a monolithic heterostructure of amorphous ferromagnetic ...material/langatate. Layers of 1.5 μm-thick FeCoSiB amorphous ferromagnetic material were deposited on the surface of the langatate single crystal using magnetron sputtering. At the resonance frequency of the structure, 107 kHz, the ME coefficient of linear conversion of 76.6 V/(Oe∙cm) was obtained. Furthermore, the nonlinear ME effect of voltage harmonic generation was observed with an increasing excitation magnetic field. The efficiency of generating the second and third harmonics was about 6.3 V/(Oe
∙cm) and 1.8 V/(Oe
∙cm), respectively. A hysteresis dependence of ME voltage on a permanent magnetic field was observed due to the presence of α-Fe iron crystalline phases in the magnetic layer. At the resonance frequency, the monolithic heterostructure had a sensitivity to the AC magnetic field of 4.6 V/Oe, a minimum detectable magnetic field of ~70 pT, and a low level of magnetic noise of 0.36 pT/Hz
, which allows it to be used in ME magnetic field sensors.
We present a theoretical model of spin transitions in stacks of molecular layers. Our model captures the already established physics of these systems (thermal hysteretic transitions and crossovers) ...and suggests a way towards in situ control of this physics by means of an external electric field. Our results pave the way toward both temperature and voltage controllable organic memory.
Tungsten crystals oriented on their 〈111〉 axis, were submitted to 6 and 10 GeV electron beams on the SPS-CERN transfer lines. The crystals, 4 and 8 mm thick, used alone or associated to 4 mm thick ...amorphous disk, were studied as positron sources. The emerging positrons were detected by a Drift Chamber partially immersed in a magnetic field, where their trajectories were reconstructed providing the energy spectrum and the angular distribution. Significant enhancements were observed for the crystal source when compared to the amorphous one of the same thickness. The gain was larger than 3 and 2 for the 4 mm and 8 mm targets, respectively. The presented results look very promising for e+e− linear colliders.
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