A.F. Iyudin

Peculiarities of intrinsic background in LaBr3: Ce and CeBr3 scintillating crystals

The intrinsic background was measured in LaBr3:Ce and CeBr3 scintillating crystals grown at the Institute of Solid-State Physics of the Russian Academy of Sciences. The measurements were taken in the range of γ-ray energies from 20 keV to ∼5 MeV. Cylindrical samples with dimensions of Ø 1.5 × 1.8 cm for LaBr3:Ce and Ø 0.5 × 1.5 cm for CeBr3 were used. Well-known peculiarities due to the 138La radioactive iso-tope and actinide contaminants were reproduced in the recorded background spectrum of the LaBr3:Ce crystal. The detailed spectrum of the intrinsic background in the CeBr3 crystal was measured for the first time. At energies of >200 keV, the background rate of CeBr3 appeared to be much lower than that of LaBr3:Ce both in the continuum and in the peculiarities associated with the radioactivity of possible contaminants.

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part I: Description of the experiment

The program of physical studies on the Vernov satellite launched on July 8, 2014 into a polar (640 × 830 km) solar-synchronous orbit with an inclination of 98.4° is presented. We described the complex of scientific equipment on this satellite in detail, including multidirectional gamma-ray detectors, electron spectrometers, red and ultra-violet detectors, and wave probes. The experiment on the Vernov satellite is mainly aimed at a comprehensive study of the processes of generation of transient phenomena in the optical and gamma-ray ranges in the Earth’s atmosphere (such as high-altitude breakdown on runaway relativistic electrons), the study of the action on the atmosphere of electrons precipitated from the radiation belts, and low- and high-frequency electromagnetic waves of both space and atmospheric origin.

Improved COMPTEL maps of the milky way

In the course of the mission we have gradually developed an analysis method that separates in an iterative manner the celestial emission and the (a priori unknown) instrumental background. It has become our standard analysis tool for point sources. We illustrate here that this method is widely applicable now. It provides mutually consistent sets of model-fitting parameters (spectra) and sky maps, both for continuum and line studies. Because of the wide applicability, it has been possible to make various cross-checks while building up confidence in this procedure.

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part II. First results

We present the first experimental results on the observation of optical transients, gamma-ray bursts, relativistic electrons, and electromagnetic waves obtained during the experiment with the RELEC complex of scientific equipment on the Vernov satellite.

Characteristics of position sensitive detector pixels based on promising inorganic scintillators LaBr3:Ce and CeBr3

The energy resolution of different-geometry LaBr3:Ce and CeBr3 scintillation crystals grown by the Institute of Solid State Physics (Russian Academy of Sciences) by the order of the Skobel’tsyn Institute of Nuclear Physics (Moscow State University) was measured. The measurements were taken at energies of detected γ rays ranging from 20 keV to ∼5 MeV. The samples under investigation were shaped as cylinders with a diameter of 0.5 cm and heights of 1.5 and 3.0 cm. The positional resolution along the crystal axis was also investigated for the CeBr3 crystals by measuring the amplitudes of the scintillation signals from the opposite crystal ends. It was shown that the ratio of these amplitudes was dependent on the distance from a crystal end surface to the interaction point of a γ quantum inside the detector according to the linear law. The positional resolution along the crystal length appeared to be comparable to the crystal diameter. The results of the study suggest that CeBr3 crystals have a great potential as position-sensitive elements of space-sensitive detectors for high-energy charge particles and γ rays.

Complete set of detectors for studying cosmic gamma-ray bursts onboard the Lomonosov satellite

The scientific instruments onboard the Lomonosov satellite include a complete set of detectors designed to study the gamma and optical emission of cosmic gamma-ray bursts (GRBs). The BDRG gamma spectrometer ensures producing a trigger of a GRB and studying GRB properties in the energy range of 10–3000 keV as well as determining the GRB source coordinates by comparing readings of three differently directed detectors. The SHOK optical cameras (with a field of view of ~20 × 40 degrees) fix a set of images by the GRB trigger preceding the trigger and a post-trigger set at a frequency of about five frames per second. The UFFO instrument incorporates the UBAT telescope with a coding mask for measurements within a range of hard X rays and soft gamma rays and the SMT optical slewing mirror telescope, which can be directed at the GRB source in about 1 s to measure the GRB optical emission at early stages.

Comparison cosmic ray irradiation simulation and particle beam test on UFFO Burst Alert & Trigger telescope(UBAT) detectors

Ultra-Fast Flash Observatory pathfinder(UFFO-p) was launched onboard Lomonosov on 28th of nApril, 2016, and now is under various types of calibration for detection of Gamma Ray Bursts n(GRBs). Since last September UFFO-p has taken X-ray data in space with UFFO Burst Alert & nTrigger telescope (UBAT), those X-rays are mostly diffused backgrounds however, the rate turns nout to be higher than expected by a factor of three. We assumed cosmic rays can contribute by nmaking the count rate higher. We did such a simulation to investigate the effect of cosmic rays. nIn December 2016, we irradiated fragmented high energy heavy ions at CERN on the UBAT ndetector. We will report the result of comparison between simulation and beam test.

Cosmic ray effect on the X-ray Trigger Telescope of UFFO/Lomonosov using YSO scintillation crystal array in space

UFFO Burst Alert and Trigger telescope (UBAT) is the X-ray trigger telescope of UFFO/Lomonosov to localize X-ray source with coded mask method and X-ray detector. Its X-ray detector is made up of 36 8×8 pixels Yttrium OxyorthoSilicate (Y2SiO5:Ce, YSO) scintillation crystal arrays and 36 64-channel Multi-Anode PhotoMultiplier Tubes (MAPMTs) for space mission. Its effective detection area is 161cm2 and energy range is several keV to 150 keV. It was successfully launched in April 28, 2016. In several calibration run, we got several X-ray background data. We already knew X-ray background flux is 2-3 counts/cm2/sec in space. However our X-ray background data shows approximately 7-8 times higher than what we know. There are many candidates to explain high X-ray background count in space. One of candidates is cosmic ray. We will report cosmic ray effect on the X-ray detector using YSO scintillation crystal arrays in space.

The Slewing Mirror Telescope of UFFO-Pathfinder: first performance report in space

The Slewing Mirror Telescope(SMT) is the first orbital instrument, using motorized mirror for observations of the space, designed to shed light on first seconds of Gamma-Ray Bursts (GRBs) prompt UV/optical emission. The SMT is main component of the Ultra-Fast Flash Observatory (UFFO). Once GRB is detected by UFFO X-ray coded mask camera, SMT turns its motorized mirror within seconds to observe optical and UV emission of GRB. After several years of delay on its launch, UFFO was finally launched in 28 April 2016. Launch took place onboard Lomonosov satellite from new Russian kosmodrom Vostochny. Several space tests have been performed during that period, which proved the concept of SMT and gave precise values of SMT sensitivity and resolution. For the first time in the space observations, motorized mirror system is able to trace objects despite the drift of telescope FOV due to satellite orbital movement.

Results of the Multimessenger GRB Observations in the Lomonosov Mission

GRB study is one of the main goals of the Lomonosov space mission. Multimessenger GRB observation is the only way of progress achievement in their study. The Lomonosov satellite is the first space mission in which the multi-wave length observations of GRBs are realized in real time without necessity of optical instrument re-orientation on GRB monitor trigger. The mission payload includes the GRB monitor BDRG, wide field optical cameras SHOK and UFFO instrument consisting of X-ray imaging telescope UBAT and UV slewing mirror telescope SMT. Two wide field cameras are placed in such a way that their fields of view (FOV) are overlapped by the GRB monitor detector FOVs. This allows the simultaneous GRB observations in gammas and optics in all-time scale of event evolution including obtaining optical light curves of prompt emission as well as of precursors. The real time data transfer to the GCN for detected GRB is realized as well as operative control of BDRG data on triggers from ground based facilities including neutrino and gravitation wave detectors. The GRB catalogue is presented in this report, also those events, for which information was obtained in different bands, are discussed in details.