ABSTRACT
High-resolution imaging of supermassive black hole shadows is a direct way to verify the theory of general relativity under extreme gravity conditions. Very Long Baseline Interferometry ...(VLBI) observations at millimetre/submillimetre wavelengths can provide such angular resolution for the supermassive black holes located in Sgr A* and M87. Recent VLBI observations of M87 with the Event Horizon Telescope (EHT) have shown such capabilities. The maximum obtainable spatial resolution of the EHT is limited by the Earth's diameter and atmospheric phase variations. In order to improve the image resolution, longer baselines are required. The Radioastron space mission successfully demonstrated the capabilities of space–Earth VLBI with baselines much longer than the Earth's diameter. Millimetron is the next space mission of the Russian Space Agency and will operate at millimetre wavelengths. The nominal orbit of the observatory will be located around the Lagrangian L2 point of the Sun–Earth system. In order to optimize the VLBI mode, we consider a possible second stage of the mission that could use a near-Earth high elliptical orbit (HEO). In this paper, a set of near-Earth orbits is used for synthetic space–Earth VLBI observations of Sgr A* and M87 in a joint Millimetron and EHT configuration. General relativistic magnetohydrodynamic models for the supermassive black hole environments of Sgr A* and M87 are used for static and dynamic imaging simulations at 230 GHz. A comparison preformed between ground and space–Earth baselines demonstrates that joint observations with Millimetron and EHT significantly improve the image resolution and allow the EHT + Millimetron to obtain snapshot images of Sgr A*, probing the dynamics at fast time-scales.
A new inorganic scintillation material based on Ba-Gd silica glass doped with cerium (BGS) is fabricated and studied. With the highest light yield among heavy glasses at the level of 2500 ph/MeV and ...fast scintillation response, the new scintillator ensures a good coincidence time resolution of < 230 ps FWHM for 511 keV γ-quanta from a 22Na source and SiPM readout. In addition to good performance in γ-quanta detection, the material demonstrates capability for efficient detection of low-energetic neutrons. The scintillator is produced by exploiting the standard industrial glass technology, which allows for an unlimited scaling up the conversion of raw material into a high-quality scintillator at a high rate. The glass can be casted in application-specific molds, so minimizing the material losses. The presented glass scintillator has potential for further improvement of its light output and scintillation response time.
Abstract
Experiments with polarized beams for EDM search in the NICA accelerator complex implies the design of an additional ByPass channels. Such alternative channels will make possible to use NICA ...as a storage ring and get enough statistical data.
The article presents the results of the
-scattering simulation at the total energy up to 27 GeV for the SPD Technical Design Report version of the Beam–Beam Counter. In the SPDRoot framework the ...simulation has been performed using the event generators: FRITIOF, Pythia8, and Pluto. The results have been compared with the differential cross section of the existing experimental data. The first estimations of the inclusive charged particle production asymmetries with Beam–Beam Counter have been obtained.
Compressed Baryonic Matter experiment at FAIR is devoted to the study of the strongly interacting matter properties at high baryonic densities and moderate temperatures. The systematic investigation ...of the Ring Imaging Cherenkov photodetector shielding box shape on its magnetic properties has been performed. It is demonstrated that the design of the shielding box with a “wing” located on the bottom plate and a back wall allows to decrease the stray magnetic field value in the vicinity of the photodetectors.
At an experiment on acceleration of a polarized proton beam up to an energy at
, the possibility of crossing the transition energy at
by a jump is considered. The scheme of crossing by a rapid change ...of transition energy, assumes the longitudinal movement in Barrier Bucket RF near the zero value of the slip-factor. The jump itself is carried out in the absence of an RF field. The paper presents the influence of the above features on the dynamics of a polarized beam.
The possibility to use the
pp
-,
pd
- and
dd
-elastic scattering for the polarimetry at NICA using the existing experimental data is discussed. The first results of the simulation of these processes ...at the total energy up to 27 GeV for the segmented scintillation counter are presented.
Experiments with polarized beams for electric dipole moment search in the NICA accelerator complex implies the design of additional bypass channels. Such alternative channels will make it possible to ...use NICA as a storage ring and collect enough statistical data.
Accurate phase diagram calculation from molecular dynamics requires systematic treatment and convergence of statistical averages. In this work we propose a Gaussian process regression based framework ...for reconstructing the free-energy functions using data of various origins. Our framework allows for propagating statistical uncertainty from finite molecular dynamics trajectories to the phase diagram and automatically performing convergence with respect to simulation parameters. Furthermore, our approach provides a way for automatic optimal sampling in the simulation parameter space based on a Bayesian optimization approach. We validate our methodology by constructing phase diagrams of two model systems, the Lennard-Jones and soft-core potential, and compare the results with the existing studies and our coexistence simulations. Finally, we construct the phase diagram of lithium at temperatures above 300 K and pressures below 30 GPa from a machine-learning potential trained on ab initio data. Our approach performs well when compared to coexistence simulations and experimental results.
The Beam–Beam Counter of the spin physics detector at NICA is proposed for local polarimetry and luminosity monitoring. The main option of the Beam-Beam Counter is the scintillation tiles with SiPM ...readout. In this paper, we present the results of studies of a scintillation detector prototype using two types of primary electronics. An estimation of the time resolution using the procedure for correcting the “time-walking” effect is discussed.
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