[Show abstract][Hide abstract] ABSTRACT: In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope, UBAT, during the preliminary calibration with MAPMTs of 64 2:88 Â 2:88 mm 2 pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode. The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection by contracting the incident angle of the scintillation. We optimized the design in the simulation and fabricated a test sample. The test sample reduced 52% crosstalk with a loss of 6% signal yield. The idea of the Inverted-Conical light guide can be adapted by scintillation detectors multi-pixel, imaging-purpose scintillation detectors such as the ultra-fast GRB observatory UFFO-UBAT, whose performances are sensitive to responding time, image resolution, and geometrical modifications.
Nuclear Instruments and Methods 01/2015; 771:55-65.
[Show abstract][Hide abstract] ABSTRACT: UFFO-pathfinder is a pioneering space mission to observe the early evolution of Gamma-ray Bursts using a fast slewing strategy. It consists of the Slewing Mirror Telescope, for rapid pointing at UV/optical wavelengths and the UFFO Burst Alert and Trigger Telescope. It has a total weight of ̃ 20 kg and will be launched on-board the Russian Lomonosov satellite at the end of 2015. The instrumental details of UFFO-pathfinder and its performance are discussed briefly here.
[Show abstract][Hide abstract] ABSTRACT: The EAS Cherenkov light array Tunka-133, with ~3 km2 geometric area, is taking data since 2009. The array permits a detailed study of cosmic ray energy spectrum and mass composition in the PeV energy range. After a short description of the methods of EAS parameter reconstruction, we present the all-particle energy spectrum and results of studying CR composition, based on 3 seasons of array operation. In the last part of the paper, we discuss possible interpretations of the obtained results.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 08/2014; 756:94–101. · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: One of the goals of the Lomonosov satellite designed by scientists of
Moscow State University is to study the prompt emission of cosmic
gamma-ray bursts. This paper describes the gamma-ray burst monitor in
the gamma-ray range (the BDRG instrument) and the wide-field optical
cameras (the SHOK instrument) for detecting both the gamma-ray burst
prompt emission and its precursors.
[Show abstract][Hide abstract] ABSTRACT: At present, the Institute of Nuclear Physics of Moscow State University,
in cooperation with other organizations, is preparing space experiments
onboard the Lomonosov satellite. The main goal of this mission is to
study extreme astrophysical phenomena such as cosmic gamma-ray bursts
and ultra-high-energy cosmic rays. These phenomena are associated with
the processes occurring in the early universe in very distant
astrophysical objects, therefore, they can provide information on the
first stages of the evolution of the universe. This paper considers the
main characteristics of the scientific equipment aboard the Lomonosov
[Show abstract][Hide abstract] ABSTRACT: The Slewing Mirror Telescope (SMT) was proposed for rapid response to prompt UV/optical photons from Gamma-Ray Bursts (GRBs). The SMT is a key component of the Ultra-Fast Flash Observatory (UFFO)-pathfinder, which will be launched aboard the Lomonosov spacecraft at the end of 2013. The SMT utilizes a motorized mirror that slews rapidly forward to its target within a second after triggering by an X-ray coded mask camera, which makes unnecessary a reorientation of the entire spacecraft. Subsequent measurement of the UV/optical is accomplished by a 10 cm aperture Ritchey-Chr`etien telescope and the focal plane detector of Intensified Charge-Coupled Device (ICCD). The ICCD is sensitive to UV/optical photons of 200–650 nm in wavelength by using a UV-enhanced S20 photocathode and amplifies photoelectrons at a gain of 1.E4–1.E6 in double Micro-Channel Plates. These photons are read out by a Kodak KAI-0340 interline CCD sensor and a CCD Signal Processor with 10-bit Analog-to-Digital Converter. Various control clocks for CCD readout are implemented using a Field Programmable Gate Array (FPGA). The SMT readout is in charge of not only data acquisition, storage and transfer, but also control of the slewing mirror, the ICCD high voltage adjustments, power distribution, and system monitoring by interfacing to the UFFO-pathfinder. These functions are realized in the FPGA to minimize power consumption and to enhance processing time. The SMT readout electronics are designed and built to meet the spacecraft’s constraints of power consumption, mass, and volume. The entire system is integrated with the SMT optics, as is the UFFO-pathfinder. The system has been tested and satisfies the conditions of launch and those of operation in space: those associated with shock and vibration and those associated with thermal and vacuum, respectively. In this paper, we present the SMT readout electronics: the design, construction, and performance, as well as the results of space environment test.
Journal of Instrumentation 07/2013; 8:P07012. · 1.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gamma-Ray Bursts (GRBs) are the most energetic explosions in the universe, their optical photon
flux rise very quickly, typically within one minute, then fall off gradually. Hundreds of GRBs optical light curves
have been measured since the first discovery of GRB in 1967. However, only a handful of measurements have
been made within a minute after the gamma ray signal. Because of this drawback, the short-hard type GRBs and
rapid-rising GRBs, which may account for 30% of all GRBs, remain practically unexplored. To reach sub-minute
timescales, the Ultra-Fast Flash Observatory (UFFO) uses a rapidly moving mirror to redirect the optical beam
instead of slewing the entire spacecraft. The first realization of this concept is UFFO-pathfinder, which is equipped
with fast-response Slewing Mirror Telescope (SMT) and a UFFO Burst Alert and Trigger Telescope (UBAT).
SMT has a slewing mirror to redirect optical photons into a telescope and then record them by an intensified CCD.
UBAT uses coded mask to provide X-ray trigger from a GRB and provides the GRB location for SMT. UFFOs
sub-minute measurements of the optical emission of dozens of GRBs each year will result in a more rigorous test
of current internal shock models, probe the extremes of bulk Lorentz factors, provide the first early and detailed
measurements of fast-rise GRB optical light curves, and help verify the prospect of GRB as a new standard candle.
The UFFO-pathfinder is fully integrated with the Lomonosov satellite and is scheduled to be launched in late 2013
or early 2014. We will present the latest progress in this conference.
33rd International Cosmic Rays Conference, Rio De Janerio, Brazil; 07/2013
[Show abstract][Hide abstract] ABSTRACT: Space-based detectors for study of extreme energy cosmic rays (EECR) are
being prepared as promising new direction of EECR study. Pioneering
space device - tracking ultraviolet set up (TUS) is at the last stage of
its construction and testing. TUS detector description is presented.
[Show abstract][Hide abstract] ABSTRACT: We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme
Universe Space Observatory, on-board the Japanese Experiment Module of the
International Space Station. Designed as a mission to explore the extreme
energy Universe from space, JEM-EUSO will monitor the Earth's nighttime
atmosphere to record the ultraviolet light from tracks generated by extensive
air showers initiated by ultra-high energy cosmic rays. In the present work, we
discuss the particularities of space-based observation and we compute the
annual exposure in nadir observation. The results are based on studies of the
expected trigger aperture and observational duty cycle, as well as, on the
investigations of the effects of clouds and different types of background
light. We show that the annual exposure is about one order of magnitude higher
than those of the presently operating ground-based observatories.
[Show abstract][Hide abstract] ABSTRACT: One of the least documented and understood aspects of gamma-ray bursts (GRBs) is the rise phase of the optical light curve. The Ultra-Fast Flash Observatory (UFFO) is an effort to address this question through extraordinary opportunities presented by a series of space missions including a small spacecraft observatory. The UFFO is equipped with a fast-response Slewing Mirror Telescope (SMT) that uses a rapidly moving mirror or mirror array to redirect the optical beam rather than slewing the entire spacecraft to aim the optical instrument at the GRB position. The UFFO will probe the early optical rise of GRBs with sub-second response, for the first time, opening a completely new frontier in GRBs and transient studies. Its fast response measurements of the optical emission of dozens of GRBs each year will provide unique probes of the burst mechanism and test the prospect of GRBs as a new standard candle, potentially opening up the z > 10 universe. For the first time we employ a motorized slewing stage in SMT that can point to the event within 1 s after the x-ray trigger provided by the UFFO Burst Alert and Trigger Telescope. These two scientific instruments comprise the UFFO-pathfinder payload, which will be placed onboard the Lomonosov satellite and launched in 2013. The UFFO-pathfinder is the first step of our long-term program of space instruments for rapid-response GRB observations. We describe early photon science, our soon-to-be-launched UFFO-pathfinder hardware and mission, and our next planned mission, the UFFO-100.
New Journal of Physics 02/2013; 15(2):023031. · 4.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Instruments and Experimental Techniques 01/2013; 56(6). · 0.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The TUS space experiment is aimed to study energy spectrum, composition, and angular distribution of the Ultra-High Energy Cosmic Ray (UHECR) at E ∼ 1020 eV. The TUS mission is planned for operation at the end of 2012 at the dedicated “Mikhail Lomonosov” satellite. The TUS detector will measure the fluorescence and Cherenkov light radiated by EAS of the UHECR using the optical system—Fresnel mirror-concentrator of 7 modules of ∼2 m2 area in total. Production of the flight model of the optical system is in progress. Status of the Fresnel mirror production, the method, and results of their optical parameters measurement are presented.
Physics of Particles and Nuclei Letters 01/2013; 10(1).
[Show abstract][Hide abstract] ABSTRACT: We present the main results of the Extensive Air Shower Cherenkov array Tunka-25. They cover the energy spectrum from 8 · 1014 to 1017 eV and mass composition of primary cosmic rays in the energy range of 3·1015 − 3 · 1016 eV. A new lateral distribution function (LDF) of Air Shower Cherenkov light and a new method to analyze the maximum depth distribution of the shower have been developed. Both have been successfully applied in the data analysis of Tunka-25. We also discuss methods of time and amplitude calibration of the array, providing an accurate determination of the primary energy and the steepness of the LDF.
Astroparticle Physics 01/2013; s 50–52:18–25. · 4.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Swift Gamma-ray Burst (GRB) observatory responds to GRB triggers with
optical observations in ~ 100 s, but cannot respond faster than ~ 60 s. While
some ground-based telescopes respond quickly, the number of sub-60 s detections
remains small. In mid- to late-2013, the Ultra-Fast Flash
Observatory-Pathfinder is to be launched on the Lomonosov spacecraft to
investigate early optical GRB emission. This pathfinder mission is necessarily
limited in sensitivity and event rate; here we discuss a next generation
rapid-response space observatory. We list science topics motivating our
instruments, those that require rapid optical-IR GRB response, including: A
survey of GRB rise shapes/times, measurements of optical bulk Lorentz factors,
investigation of magnetic dominated (vs. non-magnetic) jet models, internal vs.
external shock origin of prompt optical emission, the use of GRBs for
cosmology, and dust evaporation in the GRB environment. We also address the
impacts of the characteristics of GRB observing on our instrument and
observatory design. We describe our instrument designs and choices for a next
generation observatory as a second instrument on a low-earth orbit spacecraft,
with a 120 kg instrument mass budget. Restricted to relatively modest mass and
power, we find that a coded mask X-ray camera with 1024 cm2 of detector area
could rapidly locate about 64 GRB triggers/year. Responding to the locations
from the X-ray camera, a 30 cm aperture telescope with a beam-steering system
for rapid (~ 1 s) response and a near-IR camera should detect ~ 29 GRB, given
Swift GRB properties. Am additional optical camera would give a broadband
optical-IR slope, allowing dynamic measurement of dust extinction at the
source, for the first time.
[Show abstract][Hide abstract] ABSTRACT: New results of 300 hours of operation of the TUNKA array are presented. An improved parametrization of the Cherenkov light lateral distribution function (LDF), based on CORSIKA Monte Carlo simulations and the experiment QUEST, has been used for the reconstruction of EAS parameters. The corrected energy spectrum in the knee region is obtained. The mean depth of the EAS maximum has been derived both from the analysis of LDF steepness and the FWHM of Cherenkov light pulse. The mean mass composition around the knee is estimated.
International Journal of Modern Physics A 01/2012; 20(29). · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The project of an EAS Cherenkov array in the Tunka Valley/Siberia with an area of about 1 km2 is presented. The new array will have a ten times bigger area than the existing TUNKA-25 array and will permit a detailed study of the cosmic ray energy spectrum and the mass composition in the energy range from 1015 to 1018 eV.
International Journal of Modern Physics A 01/2012; 20(29). · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new EAS Cherenkov light array, Tunka-133, with ~1 km^2 geometrical area has
been installed at the Tunka Valley (50 km from Lake Baikal) in 2009. The array
permits a detailed study of cosmic ray energy spectrum and mass composition in
the energy range 10^16 - 10^18 eV with a uniform method. We describe the array
construction, DAQ and methods of the array calibration.The method of energy
reconstruction and absolute calibration of measurements are discussed. The
analysis of spatial and time structure of EAS Cherenkov light allows to
estimate the depth of the EAS maximum X_max. The results on the all particles
energy spectrum and the mean depth of the EAS maximum X_max vs. primary energy
derived from the data of two winter seasons (2009 -- 2011), are presented.
Preliminary results of joint operation of the Cherenkov array with antennas for
detection of EAS radio signals are shown. Plans for future upgrades --
deployment of remote clusters, radioantennas and a scintillator detector
network and a prototype of the HiSCORE gamma-telescope -- are discussed.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 01/2012; 692.