Browsing by Author "V.S. Subrahmanyam"

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A novel approach to the interpretation of PAL spectra in glycerol
(Trans Tech Publications Ltd, 2009) S.V. Stepanov; D.S. Zvezhinskii; G. Duplatre; V.M. Byakov; V.S. Subrahmanyam
A new strategy for the treatment of positron annihilation lifetime (PAL) spectra in viscous liquids is proposed, enabling to extract values of the Ps reaction rate constants with intratrack radiolytic products as well as parameters of the free volume distribution in viscous media. © (2009) Trans Tech Publications, Switzerland.
Background rejection of TEXONO experiment to explore the sub-keV energy region with HPGe detector
(Scientific Publishers, 2017) M.K. Singh; V. Sharma; L. Singh; J.H. Chen; V. Singh; V.S. Subrahmanyam; A.K. Soma; H.T. Wong
To observe the neutrino–nucleus coherent scattering as well as for dark matter search, a detection system with ultra-low energy high purity germanium detector has been set up by the TEXONO Collaboration in Kuo-Sheng Nuclear Power Plant. Owing to the weak nature and small recoil energy of these rare events, understanding of background sources and their contribution to the energy spectrum are the key factors in this experiment. In this report, we will focus in detail on the different sources of backgrounds in the TEXONO experiment and the techniques used to reject/minimize them. © 2017, Indian Association for the Cultivation of Science.
Bremsstrahlung spectra produced from kilovolt electrons incident on thick targets of Ti, W and Pt
(Institute of Physics Publishing, 2008) A.N. Agnihotri; V.S. Subrahmanyam; R.K. Yadav; R. Shanker; X. Llovet
Measurements of x-ray emission spectra generated by 10-20 keV electrons impinging normally on bulk targets of pure elements Ti (Z = 22), W (Z = 74) and Pt (Z = 78) have been performed using an experimental setup developed for studying electron-atom/molecule collisions in our laboratory. Values extracted from the experimental data for bremsstrahlung yield, integrated yield and mean energy of the bremsstrahlung radiation beam for the above collision systems have been compared with the simulation results obtained from the general purpose Monte Carlo simulation code PENELOPE. The comparisons are found to show a satisfactory agreement between them within their statistical uncertainties. Some apparent mismatches are observed for which possible causes and their origins are discussed. © 2008 IOP Publishing Ltd.
Characterization and performance of germanium detectors with sub-keV sensitivities for neutrino and dark matter experiments
(Elsevier B.V., 2016) A.K. Soma; M.K. Singh; L. Singh; G. Kiran Kumar; F.K. Lin; Q. Du; H. Jiang; S.K. Liu; J.L. Ma; V. Sharma; L. Wang; Y.C. Wu; L.T. Yang; W. Zhao; M. Agartioglu; G. Asryan; Y.Y. Chang; J.H. Chen; Y.C. Chuang; M. Deniz; C.L. Hsu; Y.H. Hsu; T.R. Huang; L.P. Jia; S. Kerman; H.B. Li; J. Li; F.T. Liao; H.Y. Liao; C.W. Lin; S.T. Lin; V. Marian; X.C. Ruan; B. Sevda; Y.T. Shen; M.K. Singh; V. Singh; A. Sonay; J. Su; V.S. Subrahmanyam; C.H. Tseng; J.J. Wang; H.T. Wong; Y. Xu; S.W. Yang; C.X. Yu; Q. Yue; M. Zeyrek
Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues including quenching factors, energy reconstruction and calibration, signal triggering and selection as well as evaluation of their associated efficiencies have to be attended. The efforts and results of a research program to address these challenges are presented. © 2016 Elsevier B.V.
Characterization of the hybrid neutron detector
(Scientific Publishers, 2019) M.K. Singh; V. Singh; V.S. Subrahmanyam; H.T. Wong
We report the performance and characterization of a custom-built hybrid neutron detector (HND). The HND consists of BC501A liquid and BC702 phosphor powder scintillation neutron detectors, which is sensitive for the fast and thermal neutrons, respectively. Software analysis packages are developed to derive the energy spectra and compare with measured ones. Position variation of the Compton edge, the maximum probability and the location of the half-maximum intensity for the different γ-peaks of various sources (i.e., 22 Na, 60 Co, 137 Cs) used in this study is presented. © 2018, Indian Association for the Cultivation of Science.
Characterization of the sub-keV Germanium detector
(Scientific Publishers, 2018) M.K. Singh; Manoj K Singh; V. Sharma; L. Singh; V. Singh; V.S. Subrahmanyam; A.K. Soma; G. Kiran Kumar; H.T. Wong
Germanium ionization detectors having sensitivities as low as 100 eV open new windows for the studies of neutrino and dark matter physics. This novel detector demands overcoming several challenges at both hardware and software levels. The amplitude of physics signals is comparable to those due to fluctuations of the pedestal electronic noise in low energy range. Therefore, it is important to study the low energy calibration properly. In this article, we focus on the optimization of the calibration scheme. © 2017, Indian Association for the Cultivation of Science.
Design and performance of a hybrid fast and thermal neutron detector
(Elsevier B.V., 2017) M.K. Singh; A. Sonay; M. Deniz; M. Ağartıoğlu; G. Asryan; G. Kiran Kumar; H.B. Li; J. Li; F.K. Lin; S.T. Lin; V. Sharma; L. Singh; V. Singh; V.S. Subrahmanyam; A.K. Soma; H.T. Wong; S.W. Yang; I.O. Yıldırım; Q. Yue; M. Zeyrek
We report the characterization, calibration and performance of a custom-built hybrid detector consisting of BC501A liquid scintillator and BC702 scintillator for the detection of fast and thermal neutrons, respectively. Pulse Shape Discrimination techniques are developed to distinguish events due to γ-rays, fast and thermal neutrons. Software analysis packages are developed to derive raw neutron energy spectra from measured proton recoil spectra. The validity is demonstrated through the reconstruction of the 241AmBe(α,n) neutron spectrum. © 2017 Elsevier B.V.
Influence of temperature on intratrack processes and Ps formation and behaviour in liquid water
(Trans Tech Publications Ltd, 2009) S.V. Stepanov; G. Duplâtre; V.M. Byakov; V.S. Subrahmanyam; D.S. Zvezhinskii; A.S. Mishagina
Positron annihilation lifetime (PAL) spectra are measured in liquid water in the temperature range 2 - 930C. The spectra are treated by taking into account intratrack reactions and assuming that radical reactions with Ps are diffusion-controlled (the respective temperature dependences obeying the Stokes-Einstein law). Equilibrium Ps bubble parameters are obtained. © (2009) Trans Tech Publications, Switzerland.
Invited review: Physics potential of the ICAL detector at the India-based Neutrino Observatory (INO)
(Indian Academy of Sciences, 2017) A. Kumar; A.M. Vinod Kumar; Abhik Jash; Ajit K Mohanty; Aleena Chacko; Ali Ajmi; Ambar Ghosal; Amina Khatun; Amitava Raychaudhuri; Amol Dighe; Animesh Chatterjee; Ankit Gaur; Anushree Ghosh; Ashok Kumar; Asmita Redij; B. Satyanarayana; B.S. Acharya; Brajesh C Choudhary; C. Ranganathaiah; C.D. Ravikumar; Chandan Gupta; D. Indumathi; Daljeet Kaur; Debasish Majumdar; Deepak Samuel; Deepak Tiwari; G. Rajasekaran; Gautam Gangopadhyay; Gobinda Majumder; H.B. Ravikumar; J.B. Singh; J.S. Shahi; James Libby; Jyotsna Singh; K. Raveendrababu; K.K. Meghna; K.R. Rebin; Kamalesh Kar; Kolahal Bhattacharya; Lalit M Pant; M Sajjad Athar; M.V.N. Murthy; Manzoor A Malik; M.D. Naimuddin; Mohammad Salim; Monojit Ghosh; Moon Moon Devi; Naba K Mondal; Nayana Majumdar; Nita Sinha; Nitali Dash; Pomita Ghoshal; Poonam Mehta; Prafulla Behera; R. Kanishka; Raj Gandhi; Rajesh Ganai; Rashid Hasan; S. Krishnaveni; S.M. Lakshmi; S.K. Singh; S.S.R. Inbanathan; S. Uma Sankar; Sadiq Jafer; Saikat Biswas; Sanjeev Kumar; Sanjib Kumar Agarwalla; Sandhya Choubey; Satyajit Saha; Shakeel Ahmed; Shiba Prasad Behera; Srubabati Goswami; Subhasis Chattopadhyay; Sudeb Bhattacharya; Sudeshna Banerjee; Sudeshna Dasgupta; Sumanta Pal; Supratik Mukhopadhyay; Sushant Raut; Suvendu Bose; Swapna Mahapatra; Tapasi Ghosh; Tarak Thakore; V.K.S. Kashyap; V.S. Subrahmanyam; Venktesh Singh; Vinay B Chandratre; Vipin Bhatnagar; Vivek M Datar; Waseem Bari; Y.P. Viyogi
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles. © Indian Academy of Sciences.
Measurement of characteristic impedance of silicon fiber sheet based readout strip panel for RPC detector in INO
(Institute of Physics Publishing, 2017) M.K. Singh; A. Kumar; N. Marimuthu; V. Singh; V.S. Subrahmanyam
The India-based Neutrino Observatory (INO) is a mega science project of India, which is going to use about 30,000 Resistive Plate Chambers (RPC) as active detector elements for the study of atmoshpheric neutrino oscillations. Each RPC detector will consist of two orthogonally placed readout strip panel for picking the signals generated in the gas chamber. The area of RPC detector in INO-ICAL (Iron Calorimeter) experiment will be 2 m × 2 m, therefore the dimensions of readout strip panel should also be 2 m × 2 m. To get undistorted signals pass through the readout strip panel to front-end electronics, their characteristic impedance should be matched with each other. In the present paper, we describe the need and search of new dielectric material for the fabrication of flame resistant, waterproof and flexible readout strip panel. We will also describe the measurement of characteristic impedance of Plastic Honeycomb (PH) based readout strip panel and Silicon Fiber Sheet (SFS) based readout strip panel in a comparative way, and its variation under loading and with time. Based on this study, we found that a 5 mm thick SFS-based readout strip panel has a minimum signal reflection at 49.5 ohm characteristic impedance value. Our study shows that SFS is a good dielectric material for the purpose. © 2017 IOP Publishing Ltd and Sissa Medialab srl.
Measurement of the bremsstrahlung spectra generated from thick targets with Z=2-78 under the impact of 10 keV electrons
(2010) Namita Yadav; Pragya Bhatt; Raj Singh; V.S. Subrahmanyam; R. Shanker
We present new experimental data on thick target bremsstrahlung spectra generated from the interaction of energetic electrons with bulk matter. The 'photon yields' in terms of double differential cross-sections (DDCS) are measured for pure elements of thick targets: Ti (Z = 22), Ag (Z = 47), W (Z = 74) and Pt (Z = 78) under the impact of 10 keV electrons. Comparison of DDCS obtained from the experimental data is made with those predicted by Monte-Carlo (MC) calculations using PENELOPE code. A close agreement between the experimental data and the MC calculations is found for all the four targets within the experimental error of 16%. Furthermore, the ratios of DDCS of bremsstrahlung photons emitted from Ag, W and Pt with those from Ti as a function of photon energy are examined with a relatively lower uncertainty of about 10% and they are compared with MC calculations. A satisfactory agreement is found between the experiment and the calculations within some normalizing factors. The variations of DDCS as a function of Z and of photon energy are also studied which show that the DDCS vary closely with Z; however, some deviations are observed for 'tip' photons emitted from high Z targets. © Indian Academy of Sciences.
Prospects of dark matter direct search under deep sea water in India
(2013) V. Singh; V.S. Subrahmanyam; L. Singh; M.K. Singh; V. Sharma; N.S. Chouhan; M.K. Jaiswal; A.K. Soma
There is compelling evidence from cosmological and astrophysical observations that about one quarter of the energy density of the universe can be attributed to cold dark matter (CDM), whose nature and properties are still unknown. Around the world large numbers of experiments are using different techniques of dark matter direct and indirect detections. According to their experimental requirements location of the experiment prefer to use either underground, under ice, or under sea water. Country like India, digging underground cavern and long tunnel is not very convenient. Therefore, authors look from the either solutions of this problem preferring to use deep sea water. In this article, we discuss the pros and corns of use of deep sea water in the dark matter search. © 2013 AIP Publishing LLC.
Status of the search of coherent neutrino nucleus elastic scattering at KSNL
(Scientific Publishers, 2018) V. Sharma; V. Singh; V.S. Subrahmanyam; H.T. Wong
Status of search of coherent elastic neutrino-nucleus scattering (CEνNS) for reactor neutrino flux at Kuo-Sheng nuclear laboratory is discussed. Different detector candidates being used for CEνNS detection across the globe while Germanium detector with its well matured technology and sub-keV threshold, seem to open unseen experimental approach to CEνNS is widely discussed. Reactor neutrinos having energy below 10 MeV are ideal source for the study of CEνNS interaction. We studied about the possible CEνNS signals with associated uncertainties and limit on percentage of channeled nuclei in germanium crystal is quoted. Detection of flavourless CEνNS interaction can play a key role to open the new window on understanding of some unknown processes of the nature. © 2018, Indian Association for the Cultivation of Science.
Structural and Mössbauer spectroscopic investigation of Fe substituted Ti-Ni shape memory alloys
(2009) D.K. Rai; T.P. Yadav; V.S. Subrahmanyam; O.N. Srivastava
In the present investigation the effect of Fe substitution in Ti51Ni49 alloy has been studied. The alloys were synthesized through radio frequency induction melting. The alloy was characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and positron annihilation techniques. It was found that the Fe substitution stabilized the TiNi type cubic (a = 2.998 Å) phase. The microstructure and presence of the oxide phase in Ti51Ni45Fe4 alloy have been investigated by scanning electron microscopy. The positron annihilation measurements indicated a similar bulk electron density in both the as-cast and annealed (1000 °C for 30 h) alloys, typically like that of bulk Ti. Mössbauer spectroscopy studies of as-cast and annealed iron substituted samples showed regions in the samples where nuclear Zeeman splitting of Fe levels occurred and an oxide phase was found to be present in as cast Ti51Ni45Fe4 alloy, while annealed sample indicated the presence of bcc iron phase. © 2009 Elsevier B.V. All rights reserved.