A steady trend in improving gamma-ray telescopes is the creation of their 3D sensitive medium, trackers based on silicon position-sensitive detectors. Among them, planar double-sided silicon strip detectors (DSSDs) are planned to be used in space telescopes of international observatories and the Russian HERMES project. The characteristics of DSSDs prototype for the e-ASTROGAM and HERMES telescopes are presented, and critical elements of the detectors are discussed. The reality of creating silicon trackers based on the physical background and technologies for the development of silicon detectors in Russia is shown.

Radiation degradation of Si ion detectors becomes critical for the experiments at new facilities giving the beam intensity increase up to 10^5 times. The study is focused on the impact of heavily damaged Bragg peak region (BPR) at the ion range end on the bulk current of Si sensors irradiated with 53.4 MeV ^40Ar ions in the fluence range (1 ‒ 4)x10^9 ion/cm^2. It is shown that taking into account only the generation current component is insufficient to explain the experimental I-V curves. Simulating I-V characteristics and the electric field profiles demonstrated arising of a built-in junction in the BPR, which controls hole diffusion at voltages below full depletion voltage. Contribution of this component to the total diode current enabled the agreement between experimental and simulated I-V curves.

The study is devoted to the treatment of in situ radiation tests results for silicon p-i-n detectors of relativistic protons, which showed the two-stage process of charge transport with avalanche multiplication at a temperature of 1.9 K. The goal of the work is to extract the carrier transport parameters from the experimental data obtained by transient current technique. For that, the impact of a spatial nonuniformity of carrier generation by the laser and spreading of the drifting carrier cloud due to diffusion on the current pulse response formation were considered. The mathematical procedure proposed for the current pulse simulation showed a key contribution of avalanche multiplication in the signal formation and allowed direct estimation of the multiplication factor from the experimental pulses. It is found that this factor only slightly depends on the bias voltage, which suggests the electric field inside the detector to be affected by the space-charge-limited current.

The paper proposes a method and its realization for stabilizing the characteristics of a multichannel position-sensitive spectrometer. The device uses a new design of the semiconductor strip detector, which allows a simultaneous injection of stable in time electric charges on all strips. This solution enables the electronics to track changes in the conversion characteristics of all electronic channels including detectors strips, and correct them during the spectrometer operation. In addition, the proposed detector design makes it possible to control the signal propagation along the strips, thus providing an on-line check of the integrity of strips metallization and the quality of their connection with the readout electronics.

A method and unit for dynamic control of conversion characteristics of spectrometric paths of multichannel charged particle registration systems based on specialized microchip with a large degree of integration similar to IDE1140 in structure is proposed. The conversion characteristics are controlled during operation of the device by auto-adjusting the offset and gain of the scaling amplifier. The proposed method allows to use the entire dynamic range of the analog-to-digital converter and adjust the temperature drift for each channel at the hardware level during operation of the device.

Sensitive observations of energetic space phenomena in the 0.3 – 10 MeV range are needed to investigate a number of hot issues of modern astrophysics and cosmology. With the advanced technology of thick double sided silicon strip detectors (Si-DSSDs) it is possible to construct a space-borne gamma-ray telescope with sensitivity 30-100 times better than that of CGRO/COMPTEL. Synergies of MeV range observations from space with GeV-TeV range spectra to be obtained with future fast and sensitive imaging atmospheric Cherenkov arrays (CTA, TAIGA-IACT, ALEGRO) would allow one to reveal complex mechanisms of energy conversion in transient gamma-ray objects, in particular, sources of gamma-ray bursts. In this short note we briefly outline most demanding objectives of 0.3 – 10 MeV range astronomy and present a schematic view of HERMES gamma-ray spectrometer being developed at the Ioffe Institute.

Studies of radioactive ions (RIs) are the most thriving field of low-energy nuclear physics. In this paper, the concept and the scientific agenda of the prospective accelerator and storage ring facility for RI beam (RIB) research are proposed for a large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented and shown to be comparable to those of advanced world centers, the so-called “RIB factories”. In the project, the emphasis is made on studies with short-lived RIBs in storage rings. A unique feature of the project is the possibility of studying electron–RI interactions in a collider experiment to determine the fundamental properties of nuclear matter, in particular, electromagnetic form factors of exotic nuclei.

— A new readout system for strip semiconductor detectors has been developed based on a dedicated IDE1140 chip. The system consists of 64 spectrometric channels that provide readout of signals from detector strips. The source of the trigger signal can be either an external signal or a detector that measures the passage of an ionizing particle through the strips. The amplitude of the signal from this detector can also be used for particle spectrometry. The control and signal-readout unit for the IDE1140 chip has been designed on an EP3C16Q240 field-programmable gate array and is used for processing, storage, and transfer of acquired data. The main characteristics of the system are presented: the integral nonlinearity is <1% in the range of 5−160 fC, and the equivalent noise charge is 0.7 fC.

A new two-coordinate position-sensitive spectrometer for the measurements of spatial and energy distribution of ionizing particles was developed. The sensitive elements of the device are two orthogonal 64 strip semiconductor detectors whose signals are read out by two Application-Specific Integrated Circuits (ASIC) IDE1140 comprising 64 spectrometric channels each. Control, pre-processing data acquisition and transfer to a computer are carried out using FPGA circuit EP3C16Q240. The main spectrometer characteristics obtained in the measurements are: equivalent noise charge of 0.7 fC and integral nonlinearity is below 1% in the range from 5 to 160 fC.

The characteristics of a beta spectrometer that consists of a total-absorption Si(Li) detector and a drift Si detector are presented. Using this spectrometer, it is possible to efficiently separate β radiation of nuclei from concomitant X and γ rays. The method is based on coincidences between signals from the thick and thin detectors. The spectrometer can be used to precisely measure the shape of the β spectra of various radioactive nuclei, in particular, of the 144Pr nucleus, which is the most promising antineutrino source for searching for neutrino oscillations into a sterile state.

A position-sensitive module for detecting ionizing radiation based on semiconductor strip detectors and a multichannel spectrometric route has been developed and implemented. The dynamic range of the detected charge generated by an ionizing particle in the detector is 5–250 fC. The position-sensitive module is a structurally complete device with the functions of amplifying the spectrometric signal, digitizing, buffering, preprocessing, and transmitting data to a computer.

The distribution of potentials over a voltage terminating structure (VTS) has been studied in silicon nuclear-radiation detectors irradiated with neutrons in the range of doses from 1 × 10 10 to 5 × 10 15 n eq /cm 2 , where the VTS represents a system of floating ring p + - n junctions. It is shown that variation in the profile of an electric field in the bulk of the detector as the radiation dose is increased is the determining factor in the distribution of potentials over the VTS. The mechanisms of VTS operation at irradiation doses lower than 5 × 10 14 n eq /cm 2 are established: the distribution of potentials between the rings is accomplished by a punch-through mechanism in the inter-ring gap, while, at higher doses, the distribution is controlled by a current-related mechanism, which is based on the density of the electron—hole generation current flowing in the bulk of the detector. The suggested mechanisms of VTS operation are confirmed experimentally and by simulation.

Development of silicon edgeless detectors started in 2004 and was motivated by preparations for the total elastic and diffractive cross-section measurement (TOTEM) experiment at the Large Hadron Collider (LHC) at CERN. In the context of this experiment, it would be necessary to detect protons scattered at ultimately small angles with respect to the LHC proton beam, which brings about a limitation imposed on the maximum distance between the beam and the sensitive region of the detector. In order to solve this problem, a new type of silicon detector (edgeless detectors) was developed; these detectors have the structure, which controls the distribution of the current near the edge of the p-n junction. In this paper we report the results of studying the distribution of the potential and an electric field in the region of the cut edge in the silicon edgeless detectors; the models, which account for the obtained results, as well as their consistency with current-voltage characteristics of silicon edgeless detectors developed for the TOTEM experiment, are discussed.

A model of the potential distribution in voltage terminating structures (VTSs) with floating p + - n junction rings in silicon radiation detectors is proposed. The model is based on experimental current-voltage characteristic of interring gaps, measured for detectors based on high-resistivity silicon with resistivities from 1 to 25 kΩ cm. The physical basis of the model is the injection principle of current flow through VTS interring gaps, which becomes possible at a certain electric field distribution in space charge regions of p + - n junctions of the sensitive contact and rings. It is shown that the injection current flow is a universal operation principle of the VTS with floating rings, which leads to rigid stabilization of potentials of individual rings. As a result, it becomes possible to divide the potential irrespective of the semiconductor material resistivity.

Intersegment insulation in p—n-junction arrays based on high-resistivity silicon, which controls the interaction of neighboring elements of position-sensitive detectors, was studied. It was shown that current-voltage characteristics of the intersegment gap of the p—n junction deeply depleted due to an applied reverse voltage contain a portion of a step change in the current, which controls the intersegment insulation resistance. This feature is caused by the effect of switching of a small fraction of the bulk current between neighboring segments. In this case, the effect of the ohmic conductance between segments on the intersegment insulation resistance is ten times weaker than the effect of bulk current switching.

The characteristics of detectors based on bulk semi-insulating GaAs (SI-GaAs) have been studied by α particle detection and spectrometry. A distinctive feature of these detectors is the dependence of the width of the space charge region W on reverse bias voltage U. The rate of increase in W(U) is ∼1 µm/V, which permits formation of a sensitive region a few millimeters thick. The main obstacle to applying kilovolt-range bias voltages U is the reverse current noise. The characteristics of diode structures in which a rectifying barrier to SI-GaAs was formed by metal deposition (Schottky diodes) and by growing heterostructures with heavily doped AlGaAs or GaAsSb epitaxial layers were compared. Nonequilibrium carrier transport in epitaxial structures capable of sustaining bias voltages above 1 kV was investigated in both weak (below 1 kV/cm) and strong (10–30 kV/cm) electric fields. In both cases, the carrier lifetimes were found to be about a few nanoseconds. Such low values are due to the high concentration of trapping centers (EL2-type native defects), which limits the carrier transport. An analysis of the spectral line shape revealed that the lifetime is almost constant throughout the detector volume. The charge introduced by a particle was found to be enhanced in fields of ∼30 kV/cm. This effect can be qualitatively explained by focusing the electric field lines at the vertex of the α-particle track, which leads to an increase in the local field strength to ∼10−5 V/cm and impact ionization by nonequilibrium electrons.

The performance of radiation detectors fabricated from semi-insulating (SI) GaAs is highly sensitive to EL2+-concentration in the material. Near-infrared optical absorption measurements are commonly used to determine the EL2-concentration and to roughly estimate the EL2+-concentration under the assumption that the optical absorption is mainly determined by the photoionization and the photoneutralization of EL20 and EL2+, respectively. However, the presence of different native defects can contribute to optical absorption and reduce the precision of determination of EL2-concentration. In this work, we evaluate the contributions into optical absorption from EL2 and other deep center namely EL3 defect (0.55eV) using near-infrared optical absorption and photoconductivity (PC) measurements in the photon energy interval 0.5–1.4eV for SI GaAs crystals grown by the liquid encapsulated Czochralski method from melts with As content changing from 50% to about 46%. The photoelectrical spectra were measured on p–i–n structure detectors with heavily doped p+ and n+ layers grown by Liquid Phase Epitaxy and on Schottky diodes. The short circuit photocurrent spectra were registered for all detectors in the energy interval 0.65–1.4eV. Unexpectedly, the current sensitivities in the regions of the extrinsic and intrinsic absorption were comparable. A comparative study of optical absorption, PC and short circuit photocurrent spectra resulted in determination of EL2+-concentration. It was concluded that contribution of additional deep centers, particularly the ionized EL3+ defect could be comparable to the EL2-contribution. The EL3 centers were attributed to oxygen-related defects based on published results and on some indirect evidence in our experimental data.

Electrical and photoelectrical properties, deep levels spectra and microcathodoluminescence spectra were measured for bulk high-resistivity GaAs samples grown from Ga-rich solution by a synthesis solute diffusion technique. It is shown that the main portion of the grown crystal is high-resistivity p-type with electrical properties determined by deep hole traps with the level near 0.43 eV from the valence band edge. The density of these 0.43 eV hole traps was shown to decrease with increasing distance from the crystallization front and the traps were associated with the deep hole traps observed earlier in Ga-rich liquid-phase-epitaxy-grown films. The single crystalline end portion of the crystal was semi-insulating n-type with a very low (some 1014 cm−3) concentration of midgap EL2 donors. This end portion of the crystal was characterized by a very high photosensitivity. Possible advantages of the use of such material in radiation detectors are briefly discussed.