You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
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 @xmath00.01@xmath1 and @xmath01@xmath2 , respectively .
the motivation of presented results is to improve physical characteristics of the gamma-400 gamma - ray telescope in the energy range of @xmath020 - 100 mev .
minimizing the amount of dead matter in the telescope aperture allows us to obtain the angular resolution better than in the current space missions in this energy range .
the gamma - ray telescope angular resolution for 50-mev gamma rays is better than 5@xmath1 .
the energy resolution with the presented construction of the gamma - ray telescope gamma-400 is about 10@xmath2 for 50-mev gamma rays .
the gamma-400 physical scheme is shown in fig .
1 . from the top ,
the telescope consists of the following layers :    * the anticoincidence system ( ac ) is composed by two - layer plastic scintillators , located both on top and on the lateral side of the apparatus .
the system is essentially used to veto charged particles ; * the converter - tracker system ( c ) consists of 22 layers .
20 layers of converter - tracker have high - z material ( tungsten ) , in which @xmath3-rays incident on the instrument can convert to an e@xmath4/e@xmath5pair .
the converter planes are interleaved with position - sensitive detectors that record the passage of charged particles , thus measuring the tracks of the particles resulting from pair conversion .
the position - sensitive detectors are double ( x , y ) silicon strips ( pitch 0.08 mm ) .
the lowest two ( x , y)-planes have no tungsten converter material .
the total converter - tracker thickness is about @xmath01x@xmath6 ( x@xmath6 is the radiation length ) .
the converter - tracker information is used to precisely determine the conversion point and the direction of each incident particle .
also this information provides the possibility to measure polarization of gamma - rays ; * the time of flight system ( tof ) is formed by plastic scintillators s1 and s2 , separated by approximately 500 mm .
this system is used both to generate the trigger for the apparatus and to reject albedo particles by measuring time of particle passage ; * the deep electromagnetic calorimeter cc .
the total calorimeter thickness is @xmath021 x@xmath6 or @xmath01.0@xmath7@xmath6 ( where @xmath7@xmath6 is nuclear interaction length ) . using a deep calorimeter allows us to extend the energy range up to several tev for gamma rays , and to reach an energy resolution of approximately 1@xmath2 above 100 gev ; * the scintillation detector s3 improves hadrons and electromagnetic showers separation .
the main difference of this scheme from the previous one is using 20 thin layers of converter foils with thickness 0.025x@xmath6 , against 8 layers of tungsten with thickness 0.1x@xmath6 [ 1 ] .
+ @xmath8the gamma-400 gamma - ray observatory will be installed onboard the navigator space platform , which is designed and manufactured by the lavochkin association [ 1 ] .    the gamma-400 physical scheme . ]
the method to reconstruct the initial angle of incident low - energy gamma rays in the gamma-400 instrument was described in [ 2 ] . in this method ,
the effect of multiple scattering of produced pair components is used to involve the energy correction in the angle reconstruction procedure , involving the imaginary curvature radius for each component of the pair ( fig .
when simulating the support structures for the detectors and for the converter foil planes were taken into account to check its influence on converter - tracker performance .
we applied a similar construction as in the fermi - lat mission [ 3 , 4 ] .
the converter - tracker tower consists from the 23 trays supported by carbon - composite sidewalls with thickness of 0.8 mm .
each tray includes aluminum honeycomb core and has thickness about 3 cm .
the total thickness of the material just from above each tungsten foil is about 0.01x@xmath6 and comparable with thickness of tungsten layer 0.025x@xmath6 for pair production ( fig .
the geometrical thickness of the matter above tungsten is 3 cm that two orders of magnitude more than geometrical thickness of converter foil ( 0.09 mm ) . for such structure ,
the accuracy of vertical localization of gamma - ray conversion point is quite different for the cases shown in fig .
2 .    two types of gamma - ray conversion events in converter - tracker .
orange : plane of silicon strips ; blue : carbon - composite layers ; green : aluminum honeycomb layers ; grey : tungsten layers ( 0.025x@xmath6 ) .
r@xmath9(e@xmath9 ) is the radius r@xmath9 of imaginary curvature for the electron ( positron ) with the energy e@xmath9 after conversion . ]    in the left part of fig .
2 , the conversion is occurred inside tungsten layer , and in the right part of fig .
2 , the conversion is appeared inside support matter .
these two types of conversion events can be easily identified from the information of strip detectors in the tracker layer just under conversion point . in the `` left '' case ,
both pair components release energy in first single strip ( 1 point event ) , while in the `` right '' case , each component of the pair releases energy in separate strip ( 2 points event ) .
if one extract the events with 1-point topology , the accuracy of angular reconstruction appears significantly better than for events with 2-points topology .
the results of angle reconstruction are shown in fig .
3a for incident gamma rays with energy of 50 mev .
the distributions for deviation angle between reconstructed direction and initial direction are shown .
the initial gamma - ray direction was fixed as 2@xmath1 for zenith angle and 45@xmath1 for the polar angle just to check the robustness of the algorithm out from vertical direction .
the angular resolution , defined as condition of 68@xmath2 containment , for 1-point topology events is @xmath04.6@xmath1 and for 2-point topology events is @xmath07@xmath1 .
the energy dependence of the angular resolution of the gamma-400 gamma - ray telescope is presented in fig .
3b for 1-point topology , 2-point topology , and combined ( 1 point and 2 points ) topology events .
the angular resolution of fermi - lat instrument for on - axis gamma rays is also shown [ 3 ] .
( a ) the distributions of the deviation angle between the reconstructed and initial direction for incident gamma rays with energy of 50 mev .
the angular resolution is determined as condition of 68@xmath2 containment .
( b ) the energy dependence of the gamma-400 angular resolution ( low energy branch ) .
black points : 1-point topology events ; red points : 2 point - topology events ; green points : 1 or 2 point topology events .
the results of calculation of angular resolution for the fermi - lat on - axis gamma rays are shown by blue line ( b ) . ]
the angular resolution for 1-point events in the gamma-400 converter - tracker is better than angular resolution obtained from fermi - lat simulation data for gamma - ray energy less , than 200 mev . for gamma - ray energy range from 200 mev to 1 tev
another method is used to reconstruct initial gamma - ray direction in the gamma-400 gamma - ray telescope [ 5 ] .
the energy dependence of angular resolution of the gamma-400 gamma - ray telescope in the energy range from 10 mev to 3 tev is presented in fig .
psf of the fermi - lat telescope for front configuration is also shown there [ 6 ] .
the gamma-400 angular resolution is significantly better than ones of fermi - lat , begining from the gamma - ray energy of 10 gev .
( a ) the energy dependence of angular resolution of the gamma-400 gamma - ray telescope in the energy range from 10 mev to 3 tev .
psf of the fermi - lat gamma - ray telescope for front configuration is also shown .
( b ) the gamma-400 energy resolution dependence from initial gamma energy ( black line ) .
the energy resolution of fermi - lat instrument for back configuration [ 6 ] ( green line ) . ]
the gamma-400 energy resolution dependence on the initial gamma energy is shown in fig .
4b by black line .
to calculate this value , only events with successful gamma - ray incident angle reconstruction were used . for each event
the energy release in active matter of detectors was taken into account .
namely , the information from the position - sensitive silicon strips detectors of tracker c and the information from the deep electromagnetic calorimeter cc ( fig .
1 ) were used .
dotted line corresponds to the estimation of instrument limit due to the influence of electronic noises .
the energy resolution of fermi - lat instrument with back configuration [ 6 ] is also presented in fig .
4b by green line . involving some additional analysis of the conversion point position inside a converter - tracker system and taking into account the information from s1 and s2 layers , it is possible to significantly improve the energy resolution of gamma with energy less , than 100 mev . for 50-mev gamma - rays we obtained the value about 10@xmath2
to improve the incident angle reconstruction accuracy for low - energy gamma rays the following construction modification is used : in the converter - tracker c ( fig .
1 ) instead of 8 layers of tungsten with thickness 0.1x@xmath6 , 20 thin layers of converter foils with thickness 0.025x@xmath6 are installed . moreover , the special analysis of topology of pair - conversion events in thin layers of converter was performed . choosing the pair - conversion events with more precise vertical localization allows us to improve the angular resolution . for 50-mev gamma rays ,
the gamma-400 gamma - ray telescope angular resolution is 4.6@xmath1 that is several degrees better than in the fermi - lat mission .
the energy resolution for the considered physical scheme is @xmath010@xmath2 for 50-mev gamma - rays .
this work was supported by national research nuclear university mephi in the framework of the russian academic excellence project ( contract no .
02.a03.21.0005 , 27.08.2013 ) .
topciev , et al . , `` the gamma-400 gamma - ray telescope for precision gamma - ray emission investigations '' , journal of physics : conference series 675 032009 , 2016 .
m. d. kheymits , et al .
, `` method of incident low - energy gamma - ray direction reconstruction in the gamma-400 gamma - ray space telescope '' , journal of physics : conference series 675 032012 . , 2016 .
w. b. atwood et al . , `` the large area telescope on the fermi gamma - ray space telescope mission '' , the astrophysical journal , 697:10711102 , 2009 . c. sgro et al .
, `` construction , test and calibration of the glast silicon tracker '' , nuclear instruments and methods in physics research a 583 , 913 , 2007 .
a. leonov , et al .
`` physical performance of gamma-400 telescope .
angular resolution , proton and electron separation '' , physics procedia 74 183  190 , 2015 .
https://www.slac.stanford.edu/exp/glast/groups/canda/ + lat_performance.htm
the main goal for the gamma-400 gamma - ray telescope mission is to perform a sensitive search for signatures of dark matter particles in high - energy gamma - ray emission . 
 measurements will also concern the following scientific goals : detailed study of the galactic center region , investigation of point and extended gamma - ray sources , studies of the energy spectra of galactic and extragalactic diffuse emissions . to perform these measurements the gamma-400 gamma - ray telescope possesses unique physical characteristics for energy range from @xmath020 mev to @xmath01000 gev in comparison with previous and current space and ground - based experiments . 
 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 @xmath00.01@xmath1 and @xmath01@xmath2 , respectively . 
 the special goal is to improve physical characteristics in the low - energy range from @xmath020 mev to 100 mev . 
 minimizing the amount of dead matter in the telescope aperture allows us to obtain the angular and energy resolutions better in this range than in current space missions . 
 the gamma - ray telescope angular resolution at 50-mev gamma rays is better than 5@xmath1 and energy resolution is @xmath010@xmath2 . 
 we report the method providing these results .