We consider the gravitational energy of the material falling from the corona as a source of energy for the formation of spicules in the solar chromosphere. We show that in the quiet ...chromosphere–corona transition region a downward-directed flow of material can generate an upward-traveling shock wave. Part of the energy of the falling material returns to the corona and contributes to its heating. We find the velocities of the falling material needed for this purpose. The corresponding range of velocities agrees well with present-day observations.
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Precision instrumentation for measuring ultraweak optical emission from biocultures has been developed. A small-sized unit for detecting optical radiation in the single-photon counting mode based ...on sensitive photomultiplier tubes (PMTs) with a differential discriminator circuit in each PMT channel has been created. A new four-channel detector system has been designed for detection and processing of electromagnetic oscillations generated by microorganisms in the active and resting phases. The characteristics of the optical emission from
Saccharomyces boulardii
have been investigated.
An X-ray absorption spectroscopy method for the detection of heavy metals at the K-absorption edges is implemented using the designed Si-PIN detector. The limits of detection of heavy metals and ...uncertainty of measurement are estimated by the results of measurements of the thickness of gold and lead foil.
A silicon detector with a longitudinal silicon wafer has been developed. x-Ray spectra at the K-absorption edges of Au, Pb, and Bi are used to measure its energy resolution. The results are compared ...with measurements based on x-rays from a
241
Am gamma-ray source. The dependence of the energy resolution of the detector on the noise of a charge-sensitive amplifier and on statistical fluctuations in pair production of carriers in the silicon is calculated.
The physical properties of the quiet solar chromosphere–corona transition region are studied. Here the structure of the solar atmosphere is governed by the interaction of magnetic fields above the ...photosphere. Magnetic fields are concentrated into thin tubes inside which the field strength is great. We have studied how the plasma temperature, density, and velocity distributions change along a magnetic tube with one end in the chromosphere and the other one in the corona, depend on the plasma velocity at the chromospheric boundary of the transition region. Two limiting cases are considered: horizontally and vertically oriented magnetic tubes. For various plasma densities we have determined the ranges of plasma velocities at the chromospheric boundary of the transition region for which no shock waves arise in the transition region. The downward plasma flows at the base of the transition region are shown to be most favorable for the excitation of shock waves in it. For all the considered variants of the transition region we show that the thermal energy transfer along magnetic tubes can be well described in the approximation of classical collisional electron heat conduction up to very high velocities at its base. The calculated extreme ultraviolet (EUV) emission agrees well with the present-day space observations of the Sun.
Two competing fundamental hypotheses are usually postulated in the solar coronal heating problem: heating by nanoflares and heating by waves. In the latter it is assumed that acoustic and ...magnetohydrodynamic disturbances whose amplitude grows as they propagate in a medium with a decreasing density come from the convection zone. The shock waves forming in the process heat up the corona. In this paper we draw attention to yet another very efficient shock wave generation process that can be realized under certain conditions typical for quiet regions on the Sun. In the approximation of stationary dissipative hydrodynamics we show that a shock wave can be generated in the quiet solar chromosphere–corona transition region by the fall of plasma from the corona into the chromosphere. This shock wave is directed upward, and its dissipation in the corona returns part of the kinetic energy of the falling plasma to the thermal energy of the corona. We discuss the prospects for developing a quantitative nonstationary model of the phenomenon.
High energy resolution silicon semiconductor detectors are developed and used in RADIAN X-ray diffractometers. The use of these detectors reduces the requirements for monochromators and β-filters, ...simplifies the optical scheme of a diffractometer, increases the peak-to-background ratio, and decreases the radiation source power and sizes of a diffractometer. To select useful events, a tunable differential discriminator with a reconfigurable energy window is used in the detector. The detector can operate with different X-ray tube anode materials.
A Si-PIN detector with longitudinal arrangement of the silicon wafer for detecting X-ray quanta with an energy of up to 100 keV is designed. Its resolution is estimated. An X-ray absorption ...spectroscopy method for the detection of heavy metals at the
K
-absorption edges is implemented using the designed detector. The results of measuring the thicknesses of lead and gold foils placed behind a shield by the X-ray absorption spectroscopy method and with a micrometer gauge are compared. The detection limits of heavy metals behind steel or aluminum shields are determined. The measurement error of the metal-foil thicknesses is estimated.
The MPD detector at the NICA heavy-ion collider at JINR Afanasiev, S.V.; Alfeev, V.S.; Aslanyan, P.Zh ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2011, Letnik:
628, Številka:
1
Journal Article
Recenzirano
The MultiPurpose Detector (MPD) is designed to study heavy-ion collisions at the Nuclotron-based heavy Ion Collider fAcility (NICA) at JINR, Dubna. Its main components located inside a ...superconducting solenoid are a tracking system composed of a silicon microstrip vertex detector followed by a large volume time-projection chamber, a time-of-flight system for particle identification and a barrel electromagnetic calorimeter. A zero degree hadron calorimeter is designed specifically to measure the energy of spectators. In this paper, all parts of the apparatus are described and their tracking and particle identification (PID) parameters are discussed in some detail.
The possibility of applying silicon PIN detectors for recording the X-ray quanta in radiography within the energy range of 25–150 keV is considered with implementation of the dual-energy method. An ...approach for estimating the method’s resolution in determining the composition of materials is proposed. In the case of determining the atomic numbers of six chemical elements for dual-energy pairs, the resolution is quantitatively estimated. Limitations and factors affecting the method resolution are established.
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