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Ahmad, Shahab
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Ahmad, Shahab
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Ahmad, S.
Ahmad S.
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29 results
Now showing 1 - 10 of 29
- PublicationA study of the Moon shadow by using GRAPES-3 muon telescope(2022-03-18)
;Zuberi, M.; ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Tanaka, K.Varsi, F.The GRAPES-3 experiment is designed to perform precision studies of gamma-ray sources in the TeV-PeV energy region. It consists of 400 plastic scintillator detectors spanning an effective area of 25000 m2 and a large area (560 m2) muon telescope which records ∼ 4 x 109 muons every day. With the recent installation of an improved triggerless data acquisition (DAQ) system, the information related to every muon is recorded with a timing resolution of 10 ns. The angular resolution and pointing accuracy of the upgraded muon telescope has been validated by characterizing the shadow of the moon among recorded muons. Here, the details of the analysis and results, as well as the simulation studies to account for the deflection of the particles in the Earth’s magnetic field will be presented. - PublicationVetoing the high energy showers in the GRAPES-3 experiment whose cores lie outside the array(2022-03-18)
;Chakraborty, M.; ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Soni, J. ;Tanaka, K. ;Varsi, F.Zuberi, M.The GRAPES-3 experiment located in Ooty consists of an array of 400 plastic scintillator detectors spread over an area of 25000m2 and a large area (560 m2) muon telescope. Every day, the array records about 3 million showers induced by the interaction of primary cosmic rays in the atmosphere. One of the primary objectives of the experiment is to measure the energy spectrum and composition of the cosmic rays in the TeV-PeV energy range. However, some of the detected showers have cores outside the array. This fraction increases with energy due to the higher lateral spread of shower particles at higher energies. Identifying these events is thus crucial for accurate measurement of the cosmic ray energy spectrum. This work will describe simple cut based as well as machine learning based strategies for identifying and excluding such events and their impact on the cosmic ray energy spectrum as measured by the Bayesian unfolding technique. - PublicationA machine learning approach to identify the air shower cores for the GRAPES-3 experiment(2022-12-06)
;Chakraborty, M.; ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A.; ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Tanaka, K. ;Varsi, F.Zuberi, M.The GRAPES-3 experiment located in Ooty consists of a dense array of 400 plastic scintillator detectors spread over an area of 25,000 m2 and a large area (560 m2) tracking muon telescope. Everyday, the array records about 3 million showers in the energy range of 1 TeV - 10 PeV induced by the interaction of primary cosmic rays in the atmosphere. These showers are reconstructed in order to find several shower parameters such as shower core, size, and age. High-energy showers landing far away from the array often trigger the array and are found to have their reconstructed cores within the array even though their true cores lie outside, due to reconstruction of partial information. These showers contaminate and lead to an inaccurate measurement of energy spectrum and composition. Such showers are removed by applying quality cuts on various shower parameters, manually as well as with machine learning approach. This work describes the improvements achieved in removal of such contaminated showers with the help of machine learning. - PublicationZenith angle dependence of pressure effect in GRAPES-3 muon telescope(2022-03-18)
;Zuberi, M.; ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Soni, J. ;Tanaka, K.Varsi, F.A large area (560 m2) muon telescope in the GRAPES-3 experiment at Ooty, India records muon intensity at high cutoff rigidities (Rc) varies from 14–32 GV along 169 independent directions spanning a field of view of 2.3 sr. The threshold energy of the recorded muons is sec(θ) GeV along a direction with a zenith angle (θ) and with the average angular accuracy of ∼4σ. The directional capabilities of the muon telescope are exploited for studying the effect of atmospheric pressure on the muon flux as a function of Rc. It is observed that the barometric coefficients relationship with logarithmic Rc can be well described by second-order polynomial function with a high Spearman Rank correlation coefficient of 0.99. - PublicationSmallest Organic Spacers-Based Ruddlesden-Popper and Dion-Jacobson Perovskites: Which One Is Better for Optoelectronics?(2023-11-16)
;Yadav, Abhishek ;Vashist, Rishabh ;Rahil, Mohammad ;Ren, Zhixiang ;Yang, Yichen ;Zhao, BaodanIn this work, the smallest and analogous organic spacers “ethylammonium” (EA) and “ethylenediammonium” (EDA) are incorporated in MAPbI3 to form RP-EA and DJ-EDA perovskites (n = 1-4), respectively, in order to compare their structural, morphological, optical, and optoelectronic properties, which revealed significantly different characteristics of both perovskite phases. Effective high frequency dielectric constants (ϵeff) of RP-EA and DJ-EDA are correlated with their optical properties, which show that the large difference between the ϵeff’s of DJ-EDA (9.62; n = 1 to 7.58; n = 4) and MAPbI3 (6.5) is responsible for sharp exciton absorbance peaks in DJ-EDA perovskites. Compared to RP-EA, the DJ-EDA perovskites showed improved stability and a higher photoresponsivity of ∼1.00 mA/W (n = 4) and retained 97.67% (n = 2) of the initial photocurrent after 50 cycles of transient photocurrent under 1 sun illumination (100 mW/cm2) performed under ambient atmosphere conditions owing to their van der Waals gap free structure. On the other hand, RP-EA perovskites possess relatively fast response times which are attributed to better band alignment and in-plane morphology. Our results provide fundamental insights about the structural and photophysical properties of the smallest carbon chain organic spacer-based RP and DJ perovskites, and these findings are crucial in order to find a suitable replacement of bulk perovskites for commercial PV applications. - PublicationMeasurement of large angle muon flux in GRAPES-3 experiment using triggerless DAQ system(2022-03-18)
;Hariharan, B. ;Hariharan, B.; ;Alt, T. ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Lindenstruth, V. ;Mahapatra, S. ;Manjunath, K. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shareef, M. S. ;Shibata, S. ;Soni, J. ;Sureshkumar, R. ;Tanaka, K. ;Varsi, F.Zuberi, M.The large area muon telescope of GRAPES-3 has been operating continuously for more than two decades with a DAQ which has several limitations. At present, this DAQ is in the process of being upgraded with a FPGA based system. The new DAQ system is designed to be triggerless and capable of recording every hit from the 3712 proportional counters along with a time-stamp (10 ns resolution) which has significantly expanded the physics horizon of the experiment. This triggerless feature allows the detection of muons beyond the nominal zenith range of the current system (θ<45◦). The upgraded DAQ system has been deployed for 25% of the telescope. An offline software trigger has been developed for the reconstruction of muon tracks by using the timing and pulse height information of each hit in the raw data. For the first time the muons are reconstructed in the entire zenith angle range. The extensive air showers (EAS) at large angles can be studied through the muon component. We present measurements of the flux of the large angle muons and their correlation with EAS triggers. - PublicationSearch for gamma rays above 30 TeV from the Crab Nebula with the GRAPES-3 experiment(2022-03-18)
;Pattanaik, D.; ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Soni, J. ;Tanaka, K. ;Varsi, F.Zuberi, M.The GRAPES-3 is a high-altitude, near-equator extensive air shower array at Ooty, India which is designed to observe cosmic and gamma-rays in TeV-PeV energy range. It consists of a dense array of 400 scintillator detectors operating in conjunction with a 560 m2 area muon telescope. Due to recent improvements in the measurements of shower arrival time and corrections for shower front curvature based on shower size and age, the angular resolution of the array has been significantly improved. By leveraging the resultant improved angular resolution and an efficient rejection of the cosmic ray background using the muon content of the shower, a search for gamma-rays above 30 TeV from the Crab Nebula has been performed. The results will be presented during the conference. - PublicationAn Advanced Triggerless Data Acquisition System for the GRAPES-3 Muon Detector(2022-03-18)
; ; ;Alt, T. ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ;Kawakami, S. ;Kojima, H. ;Lindenstruth, V. ;Mahapatra, S. ;Manjunath, K. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pattanaik, D. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shareef, M. S. ;Shibata, S. ;Soni, J. ;Sureshkumar, R. ;Tanaka, K. ;Varsi, F.Zuberi, M.The large area (560 m2) muon telescope at Gamma Ray Astronomy at PeV Energies phase -3 (GRAPES-3) experiment in Ooty, India was designed primarily to study extensive air showers (EAS) and made operational in the year 1998. It has turned out to be a unique instrument capable of studying exotic phenomena by introduction of a new parallel data acquisition system (DAQ) in year 2000 to measure the muon directional flux. The recent discoveries of transient weakening of Earth’s magnetic shield probed by a Cosmic Ray Burst [1] and measurement of the electrical properties of a thundercloud through muon imaging [2] has demonstrated the capabilities of this instrument. The design and deployment of a new triggerless muon data acquisition system (TM-DAQ) using Field Programmable Gate Array (FPGA) would enhance the present capabilities and open a new window on several physics fronts such as, a) precise measurement of the muon flux for thunderstorm studies, b) study of large angle EAS using the muon component, c) search for exotic particles characterized by early or delayed arrivals. We present here the salient features of the TM-DAQ along with initial observations - PublicationMeasurement of the improved angular resolution of GRAPES-3 EAS array by the observation of the Moon shadow(2022-03-18)
;Pattanaik, D.; ;Chakraborty, M. ;Chandra, A. ;Dugad, S. R. ;Goswami, U. D. ;Gupta, S. K. ;Hariharan, B. ;Hayashi, Y. ;Jagadeesan, P.; ; ;Kawakami, S. ;Kojima, H. ;Mahapatra, S. ;Mohanty, P. K.; ;Muraki, Y. ;Nayak, P. K. ;Nonaka, T. ;Oshima, A. ;Pant, B. P. ;Pradhan, G. S. ;Rakshe, P. S. ;Rameez, M.; ;Reddy, L. V. ;Sahoo, R. ;Scaria, R. ;Shibata, S. ;Soni, J. ;Tanaka, K. ;Varsi, F.Zuberi, M.The Moon acts as a shield against the cosmic rays, preventing them from reaching the earth, which gives rise to a deficit in the flux along the direction of the Moon. The observed deficit can be used for obtaining the absolute calibration of the angular resolution and to verify the pointing accuracy of the array. GRAPES-3 is an extensive air shower experiment located at Ooty, India consisting of a dense array of scintillator detectors. It records ∼109 showers per year with a median energy of 10 TeV. With the precise determination of the arrival time of shower particles and an accurate correction for the shower front curvature, a major improvement in the angular resolution of the array has been achieved. This was done by the array division methods including the left-right and even-odd methods. Here, we present a verification of the angular resolution estimates and the pointing accuracy by observing the shadow of the Moon in the cosmic ray flux. - PublicationStrong Photocurrent from Solution-Processed Ruddlesden–Popper 2D Perovskite–MoS2 Hybrid Heterojunctions(2023-04-04)
;Ansari, Rashid M. ;Salunke, Akshaykumar D. ;Rahil, MohammadThis study reports overall improvement in structural, morphological, and optoelectronic properties of Ruddlesden–Popper (RP) perovskites of type (BA)2(MA)n−1PbnI3n+1 by forming their bulk heterojunction hybrids with few-layer MoS2 nanoflakes. RP perovskite–MoS2 hybrid thin films have shown significantly improved packing and crystallinity compared to pristine perovskites. The presence of MoS2 at RP perovskite interface has improved the quantum confinement effects and transport of photogenerated charge carriers from perovskite to MoS2, due to suitable conduction band of MoS2 and more number of decay channels. The optoelectronic properties of RP perovskite–MoS2 hybrids are studied for various MoS2 concentrations (4.2–25.6 × 10−3 m) and at optimum concentration (12.8 × 10−3 m) the photodetectors (n = 2, 4) have shown strong, sharp, and highly stable photocurrent response. At 0.0 V bias, the RP perovskite (n = 4) and MoS2 (12.8 × 10−3 m) hybrid-based photodetectors, prepared without any encapsulation, have shown strong photocurrent density of ≈9.8 µA cm−2 under 1 sun illumination, which is ≈17 times higher compared to the pristine RP perovskites-based photodetector (0.6 µA cm−2). Further transient photocurrent, performed over 200 cycles for hybrid (n = 4+MoS2) thin film photodetector under laser (λex ≈ 405 nm, ≈630 mW cm−2) illumination and ambient air conditions has shown highly stable photocurrent with only ≈9.6% reduction in the peak photocurrent density.
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