Registered events identification procedures details in three apertures of gamma-telescope GAMMA-400 are discussed in the presented article for gammas, electrons/positrons and protons both in low and ...high energy bands. Gamma-telescope GAMMA-400 consists of the converter-tracker (C) surrounded by anticoincidence system, time-of-flight system (2 sections S1 and S2) and calorimeter. Anticoincidence system will make of top and lateral sections - ACtop and AClat, time-of-flight system TOF contain 2 segments S1 and S2. Calorimeter consists of position-sensitive calorimeter CC1 makes of 2 strips layers and 2 layers of CsI(Tl) detectors and electromagnetic calorimeter CC2 composed of CsI(Tl) crystals surrounded by plastic lateral detectors LD. Scintillation detectors of the calorimeter S3 and S4 placed correspondingly between CC1 and CC2 and after electromagnetic calorimeter. All segments of detector systems ACtop, AClat, S1-S4, LD composed of two BC-408 based sensitive layers thickness of 1 cm each. Events registration both from upper and lateral directions provides due three apertures: main, additional and lateral. GAMMA-400 parameters are optimized for detection of gamma-quanta with the energy ∼ 100 GeV in the main aperture. Gammas, electrons/positrons and protons recognition in main aperture provides due energy deposition analysis in individual detectors of ACtop, AClat, S1-S3 and CC1 individual scintillator detectors discriminators. Particles identification in the additional aperture supplied by study of energy deposition in the individual detectors S2, S3 and position-sensitive calorimeter individual scintillator detectors discriminators. In the lateral aperture low energy (0.2 - 100 MeV) photons classified by using simple anticoincidence signals from the individual detectors of LD and CC2. Higher energies γ-quanta (E>100 MeV) recognized using energy deposition analysis in the individual detectors of S3, S4, LD and CC2.
The GAMMA-400 currently developing space-based gamma-ray telescope is designed to measure the gamma-ray fluxes in the energy range from ∼20 MeV to several TeV in the highly elliptic orbit (without ...shadowing the telescope by the Earth) continuously for a long time. The physical characteristics of the GAMMA-400 gamma-ray telescope, especially the angular and energy resolutions (at 100-GeV gamma rays they are ∼0.01° and ∼1%, respectively), allow us to consider this space-based experiment as the next step in the development of extraterrestrial high-energy gamma-ray astronomy. In this paper, a method to improve the reconstruction accuracy of incident angle for low-energy gamma rays in the GAMMA-400 space-based gamma-ray telescope is presented. The special analysis of topology of pair-conversion events in thin layers of converter was performed. Applying the energy dependence of multiple Coulomb scattering for pair components, it is possible to estimate the energies for each particle, and to use these energies as weight in the angle reconstruction procedure. To identify the unique track in each projection the imaginary curvature method is applied. It allows us to obtain significantly better angular resolution in comparison with other methods applied in current space-based experiments. When using this method for 50-MeV gamma rays the GAMMA-400 gamma-ray telescope angular resolution is about 4°.
The GAMMA-400 gamma-ray space-based telescope has as its main goals to measure cosmic γ-ray fluxes and the electron-positron cosmic-ray component produced, theoretically, in dark-matter-particles ...decay or annihilation processes, to search for discrete γ-ray sources and study them in detail, to examine the energy spectra of diffuse γ-rays - both galactic and extragalactic - and to study gamma-ray bursts (GRBs) and γ-rays from the active Sun. Scientific goals of GAMMA-400 telescope require fine angular resolution. The telescope is of a pair-production type. In the converter-tracker, the incident gamma-ray photon converts into electron-positron pair in the tungsten layer and then the tracks are detected by silicon- strip position-sensitive detectors. Multiple scattering processes become a significant obstacle in the incident-gamma direction reconstruction for energies below several gigaelectronvolts. The method of utilising this process to improve the resolution is proposed in the presented work.
The GAMMA-400 gamma-ray telescope is designed to measure the gamma-ray fluxes in the energy range from ∼20 MeV to ∼1 TeV, performing a sensitive search for high-energy gamma-ray emission when ...annihilating or decaying dark matter particles. Such measurements will be also associated with the following scientific goals: searching for new and studying known Galactic and extragalactic discrete high-energy gamma-ray sources (supernova remnants, pulsars, accreting objects, microquasars, active galactic nuclei, blazars, quasars). It will be possible to study their structure with high angular resolution and measuring their energy spectra and luminosity with high-energy resolution; identify discrete gamma-ray sources with known sources in other energy ranges. The major advantage of the GAMMA-400 instrument is excellent angular and energy resolutions for gamma rays above 10 GeV. The gamma-ray telescope angular and energy resolutions for the main aperture at 100-GeV gamma rays are ∼0.01% and ∼1%, respectively. The motivation of presented results is to improve physical characteristics of the GAMMA-400 gamma-ray telescope in the energy range of ∼20-100 MeV, most unexplored range today. Such observations are crucial today for a number of high-priority problems faced by modern astrophysics and fundamental physics, including the origin of chemical elements and cosmic rays, the nature of dark matter, and the applicability range of the fundamental laws of physics. To improve the reconstruction accuracy of incident angle for low-energy gamma rays the special analysis of topology of pair-conversion events in thin layers of converter performed. Choosing the pair-conversion events with more precise vertical localization allows us to obtain significantly better angular resolution in comparison with previous and current space and ground-based experiments. For 50-MeV gamma rays the GAMMA-400 gamma-ray telescope angular resolution is better than 50.
Studying high-energy (>50GeV) cosmic gamma radiation raises a problem of selection of neutral gamma rays from a background of charged particles. The problem is embarrassed by the backsplash effect. ...The backsplash consists, in the main, of low-energy (1 MeV) secondary photons moving backwards and is produced by any high-energy gamma quantum. A charged-particle rejection method using the anticoincidence and time-of-flight systems is proposed. Charged-particle events are distinguished from those being triggered by high-energy gamma-rays producing backsplash. The method is based on the time separation of signals. It allows us to keep the gamma-ray detection efficiency high up to high energies.
The GAMMA-400 gamma-ray telescope currently under development is designed to measure fluxes of gamma rays and electron-positron cosmic-ray components, which could be associated with the annihilation ...or decay of dark matter particles, and to survey in detail the celestial sphere in order to search for and investigate discrete gamma-ray sources; to measure the energy spectra of Galactic and extragalactic dif- fuse gamma-ray emissions; and to study gamma-ray bursts and the gamma-ray emissions of active Sun. The GAMMA-400 energy range is 100 MeV to 3000 GeV. The gamma-ray telescope has an angular resolution of ∼0.01°, an energy resolution of ∼1%, and a proton rejection factor of ∼10
6
. The GAMMA-400 will be installed on Russia’s
Navigator
space platform. Observations are planned to commence in 2018.
The GAMMA-400 gamma-ray telescope is intended to measure the fluxes of gamma-rays and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV. Such measurements concern the ...following scientific tasks: investigation of point sources of gamma-rays, studies of the energy spectra of Galactic and extragalactic diffuse emission, studies of gamma-ray bursts and gamma-ray emission from the Sun, as well as high precision measurements of spectra of high-energy electrons and positrons. Also the GAMMA- 400 instrument provides the possibility for protons and nuclei measurements up to knee. But the main goal for the GAMMA-400 mission is to perform a sensitive search for signatures of dark matter particles in high-energy gamma-ray emission. To fulfill these measurements the GAMMA-400 gamma-ray telescope possesses unique physical characteristics in comparison with previous and present experiments. The major advantage of the GAMMA-400 instrument is excellent angular and energy resolution for gamma-rays above 10 GeV. The GAMMA-400 experiment will be installed onboard of the Navigator space platform, manufactured by the NPO Lavochkin Association. The expected orbit will be a highly elliptical orbit (with apogee 300.000 km and perigee 500 km) with 7 days orbital period. An important profit of such an orbit is the fact that the full sky coverage will always be available for gamma ray astronomy.
The GAMMA-400 experiment: Status and prospects Topchiev, N. P.; Galper, A. M.; Bonvicini, V. ...
Bulletin of the Russian Academy of Sciences. Physics,
03/2015, Volume:
79, Issue:
3
Journal Article
Peer reviewed
The development of the GAMMA-400 γ-ray telescope continues. The GAMMA-400 is designed to measure fluxes of γ-rays and the electron-positron cosmic-ray component possibly associated with annihilation ...or decay of dark matter particles; and to search for and study in detail discrete γ-ray sources, to measure the energy spectra of Galactic and extragalactic diffuse γ-rays, and to study γ-ray bursts and γ-rays from the active Sun. The energy range for measuring γ-rays and electrons (positrons) is from 100 MeV to 3000 GeV. For 100-GeV γ-rays, the γ-ray telescope has an angular resolution of ∼0.01°, an energy resolution of ∼1%, and a proton rejection factor of ∼5 × 10
5
. The GAMMA-400 will be installed onboard the Russian Space Observatory.
The future space-based γ-ray telescope GAMMA-400 will be installed on the Navigator platform of the Russian astrophysical observatory. A highly elliptical orbit will allow prolonged (~100 days) ...continuous observations of many regions of the celestial sphere for 7–10 years. GAMMA-400 will measure fluxes of γ‑ray emission in the energy range of ~20 MeV to several TeV and electrons + positrons to ~20 TeV. The γ-ray telescope will have excellent separation of γ-ray emissions against the background of cosmic rays and electrons + positrons from protons, along with unprecedented angular (~0.01° at
E
γ
= 100 GeV) and energy (~1% at
E
γ
= 100 GeV) resolutions 5–10 times better than for the Fermi-LAT and ground-based γ-ray telescopes. GAMMA-400 observations will provide fundamentally new data on discrete sources and spectra of γ-ray emissions and electrons + positrons.
The GAMMA-400 space project is one of the new generation of space observatories designed to search for signs of dark matter in the cosmic gamma emission, and to measure the characteristics of diffuse ...gamma-ray emission and gamma-rays from the Sun during periods of solar activity; gamma-ray bursts; extended and point gamma-ray sources; and electron, positron, and cosmic-ray nuclei fluxes with energies in the TeV ranges. The GAMMA-400 γ-ray telescope constitutes the core of the scientific instrumentation. The nature of the intended experiments imposes stringent requirements on the gamma telescope’s system of trigger signal formation, now being developed using the state-of-the-art logic devices and fast data links. The design concept of the system is discussed, along with the chosen engineering solutions and some experimental results obtained during the operation of the system prototype using a positron beam with energies of 100–300 MeV from the PAKHRA S-25R synchrotron at the Lebedev Physical Institute.
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