370 research outputs found
Modeling charge transport in Swept Charge Devices for X-ray spectroscopy
We present the formulation of an analytical model which simulates charge
transport in Swept Charge Devices (SCDs) to understand the nature of the
spectral redistribution function (SRF). We attempt to construct the
energy-dependent and position dependent SRF by modeling the photon interaction,
charge cloud generation and various loss mechanisms viz., recombination,
partial charge collection and split events. The model will help in optimizing
event selection, maximize event recovery and improve spectral modeling for
Chandrayaan-2 (slated for launch in 2014). A proto-type physical model is
developed and the algorithm along with its results are discussed in this paper.Comment: 9 pages, 7 figures, Proc. SPIE 8453, High Energy, Optical, and
Infrared Detectors for Astronomy
Genetic Diversity Assessment of Rarely Cultivated Traditional Indica Rice (Oryza sativa L.) Varieties
Random amplified polymorphic DNA fingerprinting was performed to assess the genetic
diversity among rarely cultivated traditional indica rice (Oryza sativa
L.) varieties collected from a tribal hamlet of Kerala State, India. A
total of 664 DNA bands amplified by 15 primers exhibited 72.9% polymorphism (an
average of 32.3 polymorphic bands per primer). The varieties Jeerakasala and
Kalladiyaran exhibited the highest percent (50.19%) polymorphism, while Thondi and
Adukkan showed the lowest (9.85%). Adukkan (78 bands) and Jeerakasala (56 bands)
yielded the highest and the lowest number of amplicons, respectively. Unweighted
Pair Group Method with Arithmetic mean analysis using the Dice similarity
coefficient showed the highest value of similarity coefficient between the varieties
Adukkan and Thondi, both shared higher level of similarity (0.81), followed by
Kanali and Thondi (0.88). Of the three subclusters, the varieties of Adukkan,
Thondi, Kanali, Mannuveliyan, Thonnuranthondi, and Chennellu grouped together with a
similarity of 0.77. The second group represented by Navara, Gandhakasala, and
Jeerakasala with a similarity coefficient of 0.76 formed a cohesive group. The
variety Kalladiyaran formed an isolated position that joined the second cluster. The
Principal Coordinate Analysis also showed separation of Kalladiyaran from the other
varieties
RT-2 Detection of Quasi-Periodic Pulsations in the 2009 July 5 Solar Hard X-ray Flare
We present the results of an analysis of hard X-ray observations of the C2.7
solar flare detected by the RT-2 Experiment onboard the Coronas - Photon
satellite. We detect hard X-ray pulsations at periods of ~12 s and ~15 s. We
find a marginal evidence for a decrease in period with time. We have augmented
these results using the publicly available data from the RHESSI satellite. We
present a spectral analysis and measure the spectral parameters.Comment: 12 pages, 8 figures and 3 tables, accepted for publication in The
Astrophysical Journa
Instruments of RT-2 Experiment onboard CORONAS-PHOTON and their test and evaluation V: Onboard software, Data Structure, Telemetry and Telecommand
The onboard software and data communication in the RT-2 Experiment onboard
the Coronas-Photon satellite is organized in a hierarchical way to effectively
handle and communicate asynchronous data generated by the X-ray detectors. A
flexible data handling system is organized in the X-ray detector packages
themselves and the processing electronic device, namely RT-2/E, has the
necessary intelligence to communicate with the 3 scientific payloads by issuing
commands and receiving data. It has direct interfacing with the Satellite
systems and issues commands to the detectors and processes the detector data
before sending to the satellite systems. The onboard software is configured
with several novel features like a) device independent communication scheme, b)
loss-less data compression and c) Digital Signal Processor. Functionality of
the onboard software along with the data structure, command structure, complex
processing scheme etc. are discussed in this paper.Comment: 24 pages, 2 figures, Accepted for publication in Experimental
Astronomy (in press
Instruments of RT-2 Experiment onboard CORONAS-PHOTON and their test and evaluation III: Coded Aperture Mask and Fresnel Zone Plates in RT-2/CZT Payload
Imaging in hard X-rays of any astrophysical source with high angular
resolution is a challenging job. Shadow-casting technique is one of the most
viable options for imaging in hard X-rays. We have used two different types of
shadow-casters, namely, Coded Aperture Mask (CAM) and Fresnel Zone Plate (FZP)
pair and two types of pixellated solid-state detectors, namely, CZT and CMOS in
RT-2/CZT payload, the hard X-ray imaging instrument onboard the CORONAS-PHOTON
satellite. In this paper, we present the results of simulations with different
combinations of coders (CAM & FZP) and detectors that are employed in the
RT-2/CZT payload. We discuss the possibility of detecting transient Solar
flares with good angular resolution for various combinations. Simulated results
are compared with laboratory experiments to verify the consistency of the
designed configuration.Comment: 27 pages, 16 figures, Accepted for publication in Experimental
Astronomy (in press
Signatures of Topological Defects
We argue that due to various restrictions cosmic strings and monopole-string
networks are not likely to produce the observed flux of ultra-high energy
cosmic rays (UHECR). Among the topological defects studied so far, the most
promising UHECR sources are necklaces and monopolonia. Other viable sources
which are similar to topological defects are relic superheavy particles. All
these sources have an excess of pions (and thus photons) over nucleons at
production. We demonstrate that in the case of necklaces the diffuse proton
flux can be larger than photon flux, due to absorption of the latter on
radiobackground, while monopolonia and relic particles are concentrated in the
Galactic halo, and the photon flux dominates. Another signature of the latter
sources is anisotropy imposed by asymmetric position of the sun in the Galactic
halo. In all cases considered so far, including necklaces, photons must be
present in ultra-high energy radiation observed from topological defects, and
experimental discrimination between photon-induced and proton-induced extensive
air showers can give a clue to the origin of ultra-high energy cosmic rays.Comment: version accepted for publication in Phys. Rev. D. No changes in the
conclusions and in figure
Fundamental physics in space with the Fermi Gamma-ray Space Telescope
Successfully launched in June 2008, the Fermi Gamma-ray Space Telescope,
formerly named GLAST, has been observing the high-energy gamma-ray sky with
unprecedented sensitivity for more than two years, opening a new window on a
wide variety of exotic astrophysical objects. This paper is a short overview of
the main science highlights, aimed at non-specialists, with emphasis on those
which are more directly connected with the study of fundamental
physics---particularly the search for signals of new physics in the diffuse
gamma-ray emission and in the cosmic radiation and the study of Gamma-Ray Burst
as laboratories for testing possible violations of the Lorentz invariance.Comment: 12 pages, 7 figures, submitted for the proceedings of DICE 201
Diffuse inverse Compton and synchrotron emission from dark matter annihilations in galactic satellites
Annihilating dark matter particles produce roughly as much power in electrons
and positrons as in gamma ray photons. The charged particles lose essentially
all of their energy to inverse Compton and synchrotron processes in the
galactic environment. We discuss the diffuse signature of dark matter
annihilations in satellites of the Milky Way (which may be optically dark with
few or no stars), providing a tail of emission trailing the satellite in its
orbit. Inverse Compton processes provide X-rays and gamma rays, and synchrotron
emission at radio wavelengths might be seen. We discuss the possibility of
detecting these signals with current and future observations, in particular
EGRET and GLAST for the gamma rays.Comment: 13 pages, 5 figure
- …