Dependence of effective spectrum width of synchrotron radiation on particle energy

For an exact quantitative description of spectral properties in the theory of synchrotron radiation, the concept of effective spectral width is introduced. In the classical theory, numeric calculations of effective spectral width (using an effective width not exceeding 100 harmonics) for polarization components of synchrotron radiation are carried out. The dependence of the effective spectral width and initial harmonic on the energy of a radiating particle is established

Effective spectrum width of the synchrotron radiation

For an exact quantitative description of spectral properties of synchrotron radiation (SR), the concept of effective width of the spectrum is introduced. In the most interesting case, which corresponds to the ultrarelativistic limit of SR, the effective width of the spectrum is calculated for the polarization components, and new physically important quantitative information on the structure of spectral distributions is obtained. For the first time, the spectral distribution for the circular polarization component of the SR for the upper half-space is obtained within classical theory

The current status of orbital experiments for UHECR studies

Two types of orbital detectors of extreme energy cosmic rays are being developed nowadays: (i) TUS and KLYPVE with reflecting optical systems (mirrors) and (ii) JEM-EUSO with high-transmittance Fresnel lenses. They will cover much larger areas than existing ground-based arrays and almost uniformly monitor the celestial sphere. The TUS detector is the pioneering mission developed in SINP MSU in cooperation with several Russian and foreign institutions. It has relatively small field of view (+/-4.5 deg), which corresponds to a ground area of 6.4x10^3 sq.km. The telescope consists of a Fresnel-type mirror-concentrator (~2 sq.m) and a photo receiver (a matrix of 16x16 photomultiplier tubes). It is to be deployed on the Lomonosov satellite, and is currently at the final stage of preflight tests. Recently, SINP MSU began the KLYPVE project to be installed on board of the Russian segment of the ISS. The optical system of this detector contains a larger primary mirror (10 sq.m), which allows decreasing the energy threshold. The total effective field of view will be at least +/-14 degrees to exceed the annual exposure of the existing ground-based experiments. Several configurations of the detector are being currently considered. Finally, JEM-EUSO is a wide field of view (+/-30 deg) detector. The optics is composed of two curved double-sided Fresnel lenses with 2.65 m external diameter, a precision diffractive middle lens and a pupil. The ultraviolet photons are focused onto the focal surface, which consists of nearly 5000 multi-anode photomultipliers. It is developed by a large international collaboration. All three orbital detectors have multi-purpose character due to continuous monitoring of various atmospheric phenomena. The present status of development of the TUS and KLYPVE missions is reported, and a brief comparison of the projects with JEM-EUSO is given.Comment: 18 pages; based on the rapporteur talk given by M.I. Panasyuk at ECRS-2014; v2: a few minor language issues fixed thanks to the editor; to be published in the proceeding

Phase Composition and Microstructure of Ti-Nb Alloy Produced by Selective Laser Melting

The phase composition and microstructure of Ti-Nb alloy produced from composite titanium and niobium powder by selective laser melting (SLM) was studied. Produced monolayered Ti-Nb alloy enhanced the formation of fine-grained and medium-grained zones with homogeneous element composition of 36-38% Nb mass interval. Alloy phase composition responded to [beta]-alloy substrate phase (grain size was 5-7 pm) and non-equilibrium martensite [alpha]"- phase (grain size was 0.1-0.7 [mu]m). [alpha]"-phase grains were found along [beta]-phase grain boundaries and inside grains, including decreased niobium content. Alloy microhardness varied within 4200-5500 MPa

An extensive-air-shower-like event registered with the TUS orbital detector

TUS (Tracking Ultraviolet Set-up) is the world's first orbital detector of ultra-high-energy cosmic rays (UHECRs). It was launched into orbit on 28th April 2016 as a part of the scientific payload of the Lomonosov satellite. The main aim of the mission was to test the technique of measuring the ultraviolet fluorescence and Cherenkov radiation of extensive air showers generated by primary cosmic rays with energies above ~100 EeV in the Earth atmosphere from space. During its operation for 1.5 years, TUS registered almost 80,000 events with a few of them satisfying conditions anticipated for extensive air showers (EASs) initiated by UHECRs. Here we discuss an event registered on 3rd October 2016. The event was measured in perfect observation conditions as an ultraviolet track in the nocturnal atmosphere of the Earth, with the kinematics and the light curve similar to those expected from an EAS. A reconstruction of parameters of a primary particle gave the zenith angle around 44$^\circ$ but an extreme energy not compatible with the cosmic ray energy spectrum obtained with ground-based experiments. We discuss in details all conditions of registering the event, explain the reconstruction procedure and its limitations and comment on possible sources of the signal, both of anthropogenic and astrophysical origin. We believe this detection represents a significant milestone in the space-based observation of UHECRs because it proves the capability of an orbital telescope to detect light signals with the apparent motion and light shape similar to what are expected from EASs. This is important for the on-going development of the future missions KLYPVE-EUSO and POEMMA, aimed for studying UHECRs from space.Comment: 24 pages; v2: important changes to address comments by the anonymous referee; main conclusions unchange