The paper describes a detector for carrying out diffraction experiments on a beam of synchrotron radiation, which is being developed at the Institute of Nuclear Physics of the Siberian Branch of the ...Russian Academy of Sciences. The detector will operate in the mode of direct counting of X-ray photons with an energy of more than 3–4 keV. A general description of the detector and its components is given, as well as a detailed description of the recording channel of an application-specific integrated circuit (ASIC). The results of the first measurements of the ASIC parameters are given and discussed in the article.
The electromagnetic CsI(Tl) calorimeter is one of the key systems in the Belle II detector. The calorimeter is aimed primarily at efficiently detecting photons over a wide energy range from several ...tens of MeV units to
GeV. A highly efficient data acquisition system is required for a continuous readout of signal events at a trigger rate corresponding to the maximum collider luminosity. Problems solved by such a system for the calorimeter of the Belle II detector are described.
The process
e
+
e
-
→
n
n
¯
is studied in the experiment at the VEPP-2000
e
+
e
-
collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic ...calorimeter is used to select
n
n
¯
events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.
The work describes a one-dimensional detector for diffraction experiments at a synchrotron radiation beam. The detector is being developed at the Budker Institute of Nuclear Physics, Siberian Branch, ...Russian Academy of Sciences. Until recently the institute was developing gas one-coordinate detectors, in particular a one-coordinate detector with calculated channels (OD-3M), based on the technology of multiwire proportional chambers. To provide a spatial resolution better than 100 microns at a photon energy in a wide energy range (3–30 keV), it is necessary to use solid-state microstrip or matrix sensors in combination with specialized integrated registration circuits. The developed SOCOD detector, using a microstrip sensor based on gallium arsenide as a registration element, operates in the mode of the direct counting of photons with an energy of more than 3–4 keV and a speed of up to 1 MHz/channel. The work gives a general description of the current version of the detector, a block diagram of the registration channel, the software allowing users to control the operation of the detector and display the results obtained, and the developed algorithm for leveling the trigger thresholds in the channels. The results of electronic tests, the work of the alignment algorithm and their discussion are presented.
The process
e
+
e
-
→
η
η
γ
is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb
-
1
collected by the SND detector at the VEPP-2000
e
+
e
-
...collider. The
e
+
e
-
→
η
η
γ
cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the
ϕ
η
intermediate state. Our result on the
e
+
e
-
→
η
η
γ
cross section is consistent with the
e
+
e
-
→
ϕ
η
measurement in the
ϕ
→
K
+
K
-
mode. The search for radiative processes contributing to the
e
+
e
-
→
η
η
γ
cross section is performed, and no significant signal is observed.
In this paper, we describe the current state of development of a prototype detector for the study of fast processes (DIMEX) based on a silicon microstrip sensor. The silicon microstrip sensor is made ...of
n
-type silicon with
p
-type implants in the form of strips. Aluminum contacts with microwelding pads at the ends are applied to the strips along the entire length. The signals from the strips are read using a DMXS6A integrated circuit specially designed for this project, which contains six recording electronic channels with a dark-current compensation circuit at the input, four integrators, 32 analog memory cells, and an analog shift register. Each sensor strip is connected to the guard ring through a 400-Ω resistor and to the recording-channel input through a 100-kΩ resistor. This resistive divider at the input of the recording channel makes it possible to adapt the dynamic range of the recording microcircuit integrator to the full range of photon-flux changes in synchrotron-radiation output channel no. 8 of the VEPP-4M storage ring equipped with a nine-pole wiggler with a field of 1.95 T as the source of synchrotron radiation. Measurements of the dynamic range of the DIMEX-Si prototype show that the maximal flux that can be recorded in the linear mode exceeds 10
5
photons/channel from each electron bunch in the storage ring. The ability of the detector to detect signals from bunches following after 55 ns in the multi-bunch mode, which simulates the operation of the 4+-generation synchrotron-radiation source Siberian Circular Photon Source (SKIF) under construction in the Novosibirsk region, on which such a detector is planned to be used, is also demonstrated.
New
N, N
′-bis(4,6-dimethylpyrimidin-2-yl)- and
N, N
′-bis(2,3,5,6-tetrafluorophenyl)-substituted pyromellitic diimides were synthesized. Their properties were studied in comparison with the ...previously synthesized
N, N
′-bis(4-fluorophenyl)pyromellitic diimide. Thermogravimetry, UV spectroscopy, cyclic voltammetry, and quantum chemical calculations in the framework of the density functional theory were used to characterize the synthesized compounds. The introduction of the pyrimidine cycle significantly decreases the energy of the lowest unoccupied molecular orbital. The highest occupied molecular orbitals in all compounds synthesized are deep-lying (about −7 eV).
1,3-Dipolar cycloaddition of diphenyldiazomethane to substituted 1
H
-pyrrole-2,3-diones followed by the loss of a nitrogen molecule leads to the formation of spiropyrrole-3,2'-oxiran-2-ones ...(4-oxo-2,2,6-triphenyl-1-oxa-5-azaspiro2.4hept-6-enes), which are of interest for medical chemistry. The reaction proceeds under mild conditions with a good yield in the absence of catalysts and additives and does not require column chromatography to isolate the products.
The
cross section is measured in the center-of-mass energy range from 1.07 to 2.00 GeV in the decay channel
,
. The data set with an integrated luminosity of 242 pb
accumulated in the experiment with ...the SND detector at the VEPP-2000
collider is analyzed.
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