Seminar

Title : Insights in to the development of Solar X-ray Monitor

Date : 24-01-2020
Time : 16:00:00
Speaker : Dr. M. Shanmugam
Area : Planetary Sciences Division
Venue : Seminar Room # 113/114 (Thaltej Campus)

Abstract

Solar X-ray Monitor (XSM) is one of the scientific instruments onboard Chandrayaan-2 Orbiter. This instrument provides the solar X-ray flux for the estimation of global elemental composition of the Moon by the companion instrument CLASS. The high cadence and high energy resolution solar X-ray measurement by XSM is first of its kind and this data will be used for solar studies. XSM instrument is performing as expected and even exceeding the expectations in terms of its sensitivity compared to the existing solar flux measurements. In this seminar, I will discuss the insights in to the design aspects, how the XSM instrument configuration evolved and the performance measurements.

Title : Role of active region filaments in triggering solar flares

Date : 23-01-2020
Time : 16:00:00
Speaker : Mr. Suraj Sahu
Area : Udaipur Solar Observatory (USO)
Venue : USO Seminar Hall

Abstract

Title : Continuous-variable quantum repeaters based on the quantum scissors and mode multiplexing

Date : 22-01-2020
Time : 16:00:00
Speaker : Kaushik P. Seshadreesan
Area : Atomic, Molecular and Optical Physics
Venue : Ground Floor Lecture Hall, PRL Main Campus

Abstract

Quantum repeaters are indispensable for high-rate, long-distance quantum communications. The vision of a future quantum internet hinges strongly on realizing quantum repeaters in practice. Numerous repeaters have been proposed for discrete-variable (DV) single-photon-based quantum communications. Continuous variable (CV) encodings over the quadrature degrees of freedom of the electromagnetic field mode offer an attractive alternative. For example, unlike DV, CV transmission systems do not involve single-photon detectors and hence are easier to integrate with existing optical telecom systems. Yet, repeaters for CV have remained elusive. We present a novel quantum repeater scheme for CV entanglement distribution over a lossy bosonic channel that beats the direct transmission exponential rate-loss tradeoff. The scheme involves repeater nodes consisting of a) Einstein-Podolsky-Rosen entanglement sources that generate CV entanglement in the form of two-mode squeezed vacuum (TMSV) states, b) the quantum scissors operation to perform nondeterministic noiseless linear amplification of lossy TMSV states, c) a layer of switched, mode multiplexing inspired by second-generation DV repeaters, which is the key ingredient apart from probabilistic entanglement purification that makes DV repeaters work, and d) a non-Gaussian entanglement swap operation. We present our exact results on the rate-loss envelope achieved by the scheme.

Title : Pancharatnam-Zak phase

Date : 20-01-2020
Time : 11:00:00
Speaker : Dr. Vivek Vyas
Area : Atomic, Molecular and Optical Physics
Venue : Ground Floor Lecture Hall, PRL Main Campus

Abstract

hree decades ago, in a celebrated work, Zak is credited to have found the geometric phase acquired by an electron in a one-dimensional periodic lattice as it traverses the energy band. It was found that such a geometric phase characterizes the topological state of the system and determines its electric polarization. Unfortunately, the expression given by Zak yields an arbitrary value for the geometric phase, which depends upon the choice of convention employed in expressing it. We rectify this gross error by providing a correct and consistent expression for such a geometric phase, which we call the Pancharatnam-Zak phase. In this talk we shall see that the Pancharatnam-Zak phase is a quintessentially geometric object, displaying gauge and reparametrization invariance, and correctly classifies the energy bands of the lattice. A filled band generalization of the Pancharatnam-Zak phase is also constructed and shall be discussed in the talk.

Title : Design Aspects of Venus Radiation environment monitor (VeRad) and Peak Detector

Date : 17-01-2020
Time : 16:00:00
Speaker : Sushil Kumar
Area : Planetary Sciences Division
Venue : Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Venus Radiation environment monitor (VeRad) is an instrument selected for upcoming Venus orbiter mission with an objective to measure the high energy particle flux in the energy range of 100 KeV to 100 MeV which will help in understanding the effect of interaction of these particles on Venus atmosphere. In this presentation, I will be discussing about design aspects of VeRad. In addition to this, I will also be discussing about the design aspects of the in-house developed Peak Detector. Peak detector is an important part of a spectrometer design where measurement of peak amplitude of incoming voltage signal is measured and is kept on hold up to the time required for ADC. This peak amplitude indirectly corresponds to the energy information of the incident radiation.

Date : 13-01-2020
Time : 16:00:00
Speaker : Ms. Komal Kumari, Department of Physics and Astronomy, Clemson University, Clemson, SC
Area : Space and Atmospheric Sciences Division
Venue : Ground Floor Lecture Hall, PRL

Abstract

Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are “Atmospheric Tides”. In particular, the eastward-propagating non-migrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus a key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We are utilizing 16 years of SABER (an instrument onboard TIMED satellite) DE3 tidal deconvolution diagnostics that provides a unique opportunity to investigate interannual changes in short-term tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. The statistically significant response to the inter-annual changes in short-term DE3 variability on planetary wave timescales with emphasis on 10-day wave associated with the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and solar cycle and their physical significance in relation to SABER 10-day wave diagnostics will be discussed in detail.

Title : Chondrules : noble gases and nitrogen isotopic studies

Date : 10-01-2020
Time : 16:00:00
Speaker : Ramakant R. Mahajan
Area : Planetary Sciences Division
Venue : Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Chondrules are the major constituents of chondritic meteorites. They are one of the early solar system objects, thus provide information of processes happened at that epoch. Noble gas isotopic studied in chondrules gives an important information such as homogeneity/heterogeneity of noble gas isotopic ratios in the solar nebula. Constraining the gas composition in solar nebula (as in the formed of trapped gases in chondrules) is one of the main objective of chondrule study. Exposure before compaction is another aspects in case of chondrules, to determine their formation scenario. In this talk literature survey will be discussed alongwith new initiative.

Title : Novel source of photon pairs for long-distance quantum communication

Date : 10-01-2020
Time : 15:30:00
Speaker : Dr. Shashi Prabhakar
Area : Atomic, Molecular and Optical Physics
Venue : Ground Floor Lecture Hall, PRL Main Campus

Abstract

Quantum technology is a fast-growing field of physics and engineering, which utilizes fundamental properties of quantum mechanics to enable new applications such as long-distance secure communication and metrology with sensitivity beyond classical limits. Currently, these technologies are available at visible, near-infrared (NIR) and telecom wavelengths but are strongly underdeveloped at longer wavelengths. There is a growing interest to deliver sources and detectors operating in the infrared, for various applications such as daylight satellite-to-ground and satellite-to-satellite based quantum communications, and future interferometric gravitational waves detection in LIGO experiments. In this talk, I am going to present the generation and characterization of a pulsed spontaneous parametric down-conversion photon pair source at 2.080 μm. The characterization includes the efficiency estimation of the crystal, coincidence-to-accidental ratio determination, estimation of quantum efficiency of single photon detectors at 2.080 μm, the two photon Hong-Ou-Mandel interference, and polarization entanglement

Title : Sample Acquisition through Core drilling for Planetary Remote Sensing Laboratory Studies

Date : 03-01-2020
Time : 16:00:00
Speaker : Abhishek Verma
Area : Planetary Sciences Division
Venue : Seminar Room # 113/114 (Thaltej Campus)

Abstract

Abstract : Sample acquisition for laboratory studies through sample return missions will play a pivotal role in future planetary exploration missions. Obtaining samples through core drilling is scientifically very important but technically equally challenging. In this seminar, I will be discussing the basic principles of core drilling and the challenges involved in the development of a suitable system for automated coring of planetary surfaces and their terrestrial analogues. Details of a few existing planetary core drilling systems and experiments will be described in detail.

Date : 01-01-2020
Time : 16:00:00
Speaker : Ranadeep Sarkar, SRF, Udaipur Solar Observatory, Physical Research Laboratory
Area : Space and Atmospheric Sciences Division
Venue :

Abstract

Coronal mass ejections (CMEs) are powerful expulsions of gigantic clouds containing magnetized plasma that routinely erupt from the Sun and propagate out through the solar system. When such an eruption is directed toward the Earth with high speed and has a southward component of the magnetic field (Bz), an intense magnetic storm occurs upon the impact of the CME on Earth’s magnetosphere. The storm can occur when the CME’s interplanetary flux rope (FR) and/or the sheath between the FR and the associated shock has southward Bz. Therefore, a prior knowledge of the strength and orientation of the magnetic field embedded in the FR is required in order to forecast the severity of geomagnetic storms caused by CMEs. We have developed an observationally constrained analytical model, the INterplanetary Flux Rope Simulator (INFROS), for predicting the magnetic-field vectors of interplanetary coronal mass ejections (ICMEs). The main architecture of INFROS involves using the near-Sun flux rope properties obtained from the observational parameters that are evolved through the model in order to estimate the magnetic field vectors of ICMEs at any heliocentric distance. As a proof of concept, we validate INFROS for an Earth-impacting CME which occurred on 2013 April 11. The predicted magnetic field profiles of the associated ICME show good agreement with those observed by the in-situ spacecraft, namely, WIND. In the talk, I will present these results obtained from INFROS model and its implication towards the space-weather forecasting. In addition, the INFROS model validation for an ICME event which was sequentially observed by the in-situ spacecraft, namely, MESSENGER at ≈ 0.45 AU and the STEREO-B at 1 AU will also be discussed. INFROS shows promising results in near real time which could prove to be an useful space-weather forecasting tool compared to the time-consuming and computationally expensive MHD models.