Incoherent excitation and switching of spin states in exciton-polariton condensates

We investigate, theoretically and numerically, the spin dynamics of a two-component exciton-polariton condensate created and sustained by non-resonant spin-polarized optical pumping of a semiconductor microcavity. Using the open-dissipative mean-field model, we show that the existence of well defined phase-locked steady states of the condensate may lead to efficient switching and control of spin (polarization) states with a non-resonant excitation. Spatially inhomogeneous pulsed excitations can cause symmetry breaking in the pseudo-spin structure of the condensate and lead to formation of non-trivial spin textures. Our model is universally applicable to two weakly coupled polariton condensates, and therefore can also describe the behaviour of condensate populations and phases in 'double-well' type potentials

Compton scattering sequence reconstruction algorithm for the liquid xenon gamma-ray imaging telescope (LXeGRIT)

The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is a balloon born experiment sensitive to \g -rays in the energy band of 0.2-20 MeV. The main detector is a time projection chamber filled with high purity liquid xenon (LXeTPC), in which the three-dimensional location and energy deposit of individual \g -ray interactions are accurately measured in one homogeneous volume. To determine the \g -ray initial direction (Compton imaging), as well as to reject background, the correct sequence of interactions has to be determined. Here we report the development and optimization of an algorithm to reconstruct the Compton scattering sequence and show its performance on Monte Carlo events and LXeGRIT data.Comment: To appear in: Hard X-Ray, Gamma-Ray, and Neutron Detector Physics II, 2000; Proc. SPIE, vol. 4141; R.B. James & R.C. Schirato, ed

Quantum Hall Mach-Zehnder interferometer at fractional filling factors

We use a Mach-Zehnder quantum Hall interferometer of a novel design to investigate the interference effects at fractional filling factors. Our device brings together the advantages of usual Mach-Zehnder and Fabry-Perot quantum Hall interferometers. It realizes the simplest-for-analysis Mach-Zehnder interference scheme, free from Coulomb blockade effects. By contrast to the standard Mach-Zehnder realization, our device does not contain an etched region inside the interference loop. For the first time for Mach-Zehnder interference scheme, the device demonstrates interference oscillations with $\Phi^*=e/e^*\Phi_0=\Phi_0/\nu$ periodicity at fractional filling factor 1/3. This result indicates that we observe clear evidence for fractionally charged quasiparticles from simple Aharonov-Bohm interference.Comment: as accepted to EP

Spectroscopy and Imaging Performance of the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)

LXeGRIT is a balloon-borne Compton telescope based on a liquid xenon time projection chamber (LXeTPC) for imaging cosmic \g-rays in the energy band of 0.2-20 MeV. The detector, with 400 cm$^2$ area and 7 cm drift gap, is filled with high purity LXe. Both ionization and scintillation light signals are detected to measure the energy deposits and the three spatial coordinates of individual \g -ray interactions within the sensitive volume. The TPC has been characterized with repeated measurements of its spectral and Compton imaging response to \g -rays from radioactive sources such as \na, \cs, \yt and Am-Be. The detector shows a linear response to \g -rays in the energy range 511 keV -4.4 MeV, with an energy resolution (FWHM) of \Delta E/E=8.8% \: \sqrt{1\MeV /E}. Compton imaging of \yt \g -ray events with two detected interactions is consistent with an angular resolution of $\sim$ 3 degrees (RMS) at 1.8 MeV.Comment: To appear in: Hard X-Ray, Gamma-Ray and Neutron Detector Physics XI, 2000; Proc. SPIE, vol. 4140; K.A. Flanagan & O.H. Siegmund, ed

Polariton Pattern Formation and Photon Statistics of the Associated Emission

We report on the formation of a diverse family of transverse spatial polygon patterns in a microcavity polariton fluid under coherent driving by a blue-detuned pump. Patterns emerge spontaneously as a result of energy-degenerate polariton-polariton scattering from the pump state to interfering high order vortex and antivortex modes, breaking azimuthal symmetry. The interplay between a multimode parametric instability and intrinsic optical bistability leads to a sharp spike in the value of second order coherence g (2)(0) of the emitted light, which we attribute to the strongly superlinear kinetics of the underlying scattering processes driving the formation of patterns. We show numerically by means of a linear stability analysis how the growth of parametric instabilities in our system can lead to spontaneous symmetry breaking, predicting the formation and competition of different pattern states in good agreement with experimental observations

The first result of the neutrino magnetic moment measurement in the GEMMA experiment

The first result of the neutrino magnetic moment measurement at the Kalininskaya Nuclear Power Plant (KNPP) with the GEMMA spectrometer is presented. An antineutrino-electron scattering is investigated. A high-purity germanium detector of 1.5 kg placed 13.9 m away from the 3 GW reactor core is used in the spectrometer. The antineutrino flux is $2.73\times 10^{13} \nu_e / cm^2 / s$. The differential method is used to extract the $\nu$-e electromagnetic scattering events. The scattered electron spectra taken in 6200 and 2064 hours for the reactor ON and OFF periods are compared. The upper limit for the neutrino magnetic moment $\mu_\nu < 5.8\times 10^{-11}$ Bohr magnetons at 90{%} CL is derived from the data processing.Comment: 9 pages, 10 figures, 2 table

The role of zoophilous flies in the spread of zoonoses in cattle breeding farms of the Ivanovo region and measures to combat them

The purpose of the research is to study the fauna of zoophilous flies on the territory of the farms of the Palekh district of the Ivanovo region, to determine the comparative effectiveness of insecticidal preparations and the duration of their action; establish the role of zoophilous flies in the spread of helminth eggs and protozoan oocysts.Materials and methods. The faunistic collection of zoophilous flies was carried out in calf dispensaries of livestock farms in the farms of the Palekh district of the Ivanovo region. The species of zoophilic flies was determined at the Department of Infectious and Parasitic Diseases of the Ivanovo State Agricultural Academy. The comparative effectiveness of insecticidal preparations was carried out.Results and discussion. The fauna of zoophilic flies on cattle farms in the farms of the Ivanovo region of the Palekh district is represented by three families: Muscidae (92.78%), Calliphoridae (1.16%), Scatophagidae (5.69%). They are equally contaminated with eggs of pathogens of helminthoses and oocysts of pathogens of protozooses, and their role in the spread of helminthosis and protozoosis is determined by the index of dominance in the fauna of livestock buildings. The fastest effect of acute insecticidal action was observed in the drug with AD imidacloprid – 4 min. after contact of insects with treated surfaces of objects. In preparations with AD, thiamethoxam and cypermethrin showed insecticidal properties after 8 min. The longest insecticidal effect was observed in the drug with AD imidacloprid; it was 13 days, while for drugs with DV thiamethoxam and cypermethrin - a little more than half of this period

A Combine On-Line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for The ATLAS Silicon Tracker

An upgrade to the ATLAS silicon tracker cooling control system may require a change from C3F8 (octafluoro-propane) to a blend containing 10-30% of C2F6 (hexafluoro-ethane) to reduce the evaporation temperature and better protect the silicon from cumulative radiation damage with increasing LHC luminosity. Central to this upgrade is a new acoustic instrument for the real-time measurement of the C3F8/C2F6 mixture ratio and flow. The instrument and its Supervisory, Control and Data Acquisition (SCADA) software are described in this paper. The instrument has demonstrated a resolution of 3.10-3 for C3F8/C2F6 mixtures with ~20%C2F6, and flow resolution of 2% of full scale for mass flows up to 30gs-1. In mixtures of widely-differing molecular weight (mw), higher mixture precision is possible: a sensitivity of < 5.10-4 to leaks of C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 160) has been seen. The instrument has many potential applications, including the analysis of mixtures of hydrocarbons, vapours for semi-conductor manufacture and anaesthesia