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Banerjee, D.
- Development of a Cerium-Doped Lanthanum Bromide Gamma-Ray Spectrometer for Planetary Missions and Feasibility Studies for Determination of Elemental Abundances of Radioactive Elements (Th, K and U)
Abstract Views :408 |
PDF Views:145
Authors
Affiliations
1 Planetary Sciences and Exploration Group, Physical Research Laboratory, Ahmedabad 380 009, IN
1 Planetary Sciences and Exploration Group, Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Current Science, Vol 110, No 11 (2016), Pagination: 2135-2138Abstract
We present the development of a cerium-doped lanthanum bromide (LaBr3 : Ce) gamma-ray spectrometer (GRS) with the primary objective of determining the abundance and distribution of Th, U, K, and other major elements, including Fe on the entire planetary surface by measuring gamma-ray signals produced by radioactive decay, neutron inelastic scattering and neutron capture reactions in the energy region 0.03- 8 MeV. The energy resolution of the LaBr3 : Ce GRS developed in-house using front-end and processing electronics at 511 and 1274 keV is estimated to be 4.1% and 2.5% respectively. The intrinsic activity count rate for our 3n * 3n LaBr3 : Ce GRS is ~61 counts s-1 (i.e. ~0.18 counts s-1 cm-3) for the 40K energy window (1400-1520 keV) and ~3.4 counts s-1 for the 232Th (2550-2700 keV) energy window. Although this large intrinsic activity of the LaBr3 : Ce crystal inhibits estimation of the concentrations of Th and K, our attempts using a NaI(Tl) GRS (with electronics developed in-house) were more successful. The Th concentration of US-110 was estimated to be ~11.4 ppm and is within 14% of the 13.2 ppm value determined using a HPGe GRS. The K concentration of US-110 was estimated to be 0.87% and is within ~10% of the 0.78% value determined independently using a HPGe GRS.Keywords
Cerium Radioactive Elements, Gamma Ray Spectroscopy, Lanthanum Bromide, Sodium Iodide.- Levitation of Charged Dust Grains and its Implications in Lunar Environment
Abstract Views :364 |
PDF Views:132
Authors
J. P. Pabari
1,
D. Banerjee
1
Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
Source
Current Science, Vol 110, No 10 (2016), Pagination: 1984-1989Abstract
The surfaces of airless, non-magnetized bodies like the Moon are directly exposed to solar wind and ultraviolet radiation, causing surface dust grains to be electrically charged and levitated, whenever electric fields exceed the surface forces and gravity. For an improved understanding of the lunar dust environment, we study the surface charging processes using electrostatic modelling and present the results here. We apply Gauss's law to examine the dust levitation and compare the implications with those obtained using freespace capacitance of the particle. Calculating grain charge on surface by assuming its free-space capacitance is erroneous and is therefore inapplicable. The daytime surface potential during high solar activity is estimated to be ˜20 V, while the nighttime potential can be as high as -3.8 kV. The maximum radius of levitating particles is greatly affected by the method used to model the dust levitation. Using Gauss's approach, it comes out to be in the picometre range near the terminator, in contrast to existing calculations which estimate it to be in the nanometre to micrometer range. The LDEX provided no indication of 0.1 μm-sized particles near the terminator, as suggested previously from Apollo observations. This result is not inconsistent with our predictions based on Gauss's law. Hence, it still remains an open question whether dust levitation occurs on the Moon or not, and experiments are necessary on future lunar lander mission which provide direct measurement of surface potential and near-surface charged dust particles to confirm the same.Keywords
Dust, Levitation, Lunar Environment, Photoemission, Plasma.- National Large Solar Telescope
Abstract Views :360 |
PDF Views:154
Authors
Affiliations
1 Indian Institute of Astrophysics, Bengaluru 560 034, IN
1 Indian Institute of Astrophysics, Bengaluru 560 034, IN
Source
Current Science, Vol 113, No 04 (2017), Pagination: 696-700Abstract
The National Large Solar Telescope (NLST) aims primarily to carry out observations of the solar atmosphere with high spatial, spectral and temporal resolution. A comprehensive site characterization programme, that commenced in 2007, has identified an excellent site in the Ladakh region at the Pangong lake, India. With an innovative optical design, NLST is an on-axis Gregorian telescope with a low number of optical elements to reduce the number of reflections and yield a high throughput with low polarization. In addition, it uses high-order adaptive optics to produce close to diffraction limited performance. To control atmospheric and thermal perturbations of the observations, the telescope will function with a fully open dome, to achieve its full potential atop a 25 m tower. The post-focus instruments include broadband and tuneable Fabry-Perot narrow band imaging instruments and a high-resolution spectropolarimeter.Keywords
Adaptive Optics, High Angular Resolution, Magnetic Fields, Solar Telescope.References
- Shelyag, S., Keys, P., Mathioudakis, M. and Keenan, F. P., Vorticity in the solar photosphere. Astron. Astrophys., 2011, 526(A5), 1–7.
- Hasan, S. S., Soltau, D., Kärcher, H., Süss, M. and Berkefeld, T., NLST – India’s National Large Solar Telescope. Astron. Nachr., 2010, 331, 628–635.
- Hasan, S. S., Indian National Large Solar Telescope. ASP Conf. Ser., 2012, 463, 395–403.
- Khomenko, E., Collados, M., Solanki, S. K., Lagg, A. and Trujillo Bueno, J., Quiet-Sun inter-network magnetic fields observed in the infrared. Astron. Astrophys., 2003, 408, 1115–1135.
- Solanki, S. K., Livingston, W. L. and Ayres, T., New light on the heart of darkness of the solar chromosphere. Science, 1994, 263, 64–66.
- Ravindra, B. and Banyal, B., A dual Fabry–Perot based narrow band imager for the National Large Solar Telescope. ASI Conf. Ser., 2011, 2, 47–53.
- Elmore, D. F. et al., The advanced stokes polarimeter – a new instrument for solar magnetic field research. SPIE, 1992, 1746, 22–23.
- Hasan, S. S., Bagare, S. P. and Rangarajan, K. E., Solar astronomy at high altitude. Proc. Indian Natl. Sci. Acad., 2014, 80, 815–825.
- Chronology of Coastal Dune Ridges in Vaigai Prodelta Region, Southeastern Tamil Nadu, India
Abstract Views :381 |
PDF Views:133
Authors
Affiliations
1 Department of Remote Sensing, Bharathidasan University, Tiruchirappalli 620 023, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN
1 Department of Remote Sensing, Bharathidasan University, Tiruchirappalli 620 023, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Current Science, Vol 120, No 2 (2021), Pagination: 382-388Abstract
The Tamil Nadu coastline, India, has extensive dunes which can be used for inferring quaternary palaeoclimates. In the present study, we aim to determine the chronology of the dunes in the Vaigai prodelta region along the southeastern coastline of the country. Optically stimulated luminescence ages for the elevated beach ridge samples SANK-5, SANK-4, SANK-3, SANK-2 and SANK-1 were estimated to be 0.9 ± 0.1, 1.1 ± 0.1, 1.8 ± 0.2, 5.3 ± 0.4 and 27 ± 2.3 ka respectively, from top to bottom of the section. The first four phases of aeolian activation occurred in marine oxygen isotope stage-1, whereas the ~27 ka age suggests that sediment deposition occurred in marine oxygen isotope stage-3. The luminescence ages were in stratigraphic order, and represent the first dates of aeolian activation in the Vaigai region.Keywords
Aeolian Activation, Chronology, Coastline, Luminescence Ages, Palaeoclimate, Red Dunes.References
- Gardner, R. A. M., Reddening of dune sands – evidence from southeast India. Earth Surface Process. Landforms, 1981, 6, 459– 468.
- Jayangondaperumal, R., Murari, M. K., Sivasubramanian, P., Chandrasekhar, N. and Singhvi, A. K., Luminescence dating of fluvial and coastal red sediments in SE coast, India, and implications for paleoenvironmental changes and dune reddening. Quaternary Res., 2012, 77, 468–481.
- Huntley, D. J., Hutton, J. T. and Prescott, J. R., Optical dating using inclusions within quartz grains. Geology, 1993, 21, 1087– 1090.
- Banerjee, D., Bøtter-Jensen, L. and Murray, A. S., Retrospective dosimetry: estimation of the dose to quartz using the single-aliquot regenerative-dose protocol. Appl. Radiat. Isot., 2000, 52, 831– 844.
- Murray, A. S. and Wintle, A. G., Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiat. Meas., 2000, 32, 57–73.
- Thiel, C., Buylaert, J. P., Murray, A. S., Terhorst, B., Hofer, I., Tsukamoto, S. and Frechen, M., Luminescence dating of the Stratzing loess profile (Austria) – testing the potential of an elevated temperature post-IR IRSL protocol. Quaternary Int., 2011, 234, 23–31.
- Buylaert, J. P., Jain, M., Murray, A. S., Thomsen, K. J., Thiel, C. and Sohbati, R., A robust feldspar luminescence dating method for Middle and Late Pleistocene sediments. Boreas, 2012, 41, 435– 451.
- Zhang, J., Tsukamoto, S., Nottebaum, V. and Lehmkuhl, F., De plateau and its implications for post-IR IRSL dating of polymineral fine grains. Quaternary Geochronol., 2015, 30, 147–153.
- Li, B. and Li, S. H., Thermal stability of infrared stimulated luminescence of sedimentary K-feldspar extracts. Radiat. Meas., 2011, 46, 29–36.
- Banerjee, D., Murray, A. S., Bøtter-Jensen, L. and Lang, A., Equivalent dose estimation using a single aliquot of polymineral fine grains. Radiat. Meas., 2001, 33, 73–94.
- Lamothe, M., Forget Brisson, L. and Hardy, F., Dose recovery performance in double IRSL/pIRIR SAR protocols. Radiat. Meas., 2018, 120, 120–123.
- Colarossi, D., Duller, G. A. T., Roberts, H. M., Exploring the behaviour of luminescence signals from feldspars: implications for the single aliquot regenerative dose protocol. Radiat. Meas., 2018, 109, 35–44.
- Rashidi, Z., Sohbati, R., Karimi, A., Farpoor, M. H., Khormali, F., Thomson. W. and Murray, A. S., Constraining the timing of palaeosol development in Iranian arid environments using OSL dating. Quaternary Geochronol., 2019, 49, 92–100.
- Godfrey-Smith, D. I., Huntley, D. J. and Chen, W. H., Optical dating studies of quartz and feldspar sediment extracts. Quaternary Sci. Rev., 1988, 7, 373–380.
- Murray, A. S., Thomsen, K. J., Masuda, N., Buylaert, J. P. and Jain, M., Identifying well bleached quartz using the different bleaching rates of quartz and feldspar luminescence signals. Radiat. Meas., 2012, 47, 688–695.
- Railsback, L. B., Gibbard, P. L., Head, M. J., Voarintsoa, N. R. G. and Toucanne, S., An optimized scheme of lettered marine isotope substages for the last 1.0 million years, and the climatostratigraphic nature of isotope stages and substages. Quaternary Sci. Rev., 2015, 111, 94–106.
- Alappat, L., Frechen, M., Ramesh, R., Tsukamoto, S. and Srinivasalu, S., Evolution of late Holocene coastal dunes in the Cauvery delta region of Tamil Nadu, India. J. Asian Earth Sci., 2011, 42, 381–397.
- Alappat, L., Joseph, S., Tsukamoto, S., Kaufhold, S. and Frechen, M., Chronology and weathering history of red dunes in the southwest coast of Tamil Nadu, India. German J. Geol., 2016, 168, 183–198.
- Tiwari, M., Singh, A. K. and Ramesh, R., High-resolution monsoon records since the last glacial maximum: a comparison of marine and terrestrial paleoarchives from South Asia. J. Geophys. Res., 2011; doi:10.1155/2011/765248.
- Overpeck, J., Anderson, D., Trumbore, S. and Prell, W., The southwest Indian monsoon over the last 18,000 years. Climate Dynamics, 1996, 12, 213–225.
- Kale, V. S. and Rajaguru, S. N., Late Quaternary alluvial history of northwest Deccan Upland region. Nature, 1987, 325, 612–614.
- Banerjee P. K., Holocene and Late Pleistocene relative sea level fluctuations along the east coast of India. Mar. Geol., 2000, 167, 243–260.
- Kunz, A., Frechen, M., Ramesh, R. and Urban, B., Luminescence dating of late Holocene dunes showing remnants of early settlement in Cuddalore and evidence of monsoon activity in south east India. Quaternary Int., 2010, 222, 194–298.
- Singhvi, A. K., Deraniyagala, S. U. and Sengupta, D., Thermoluminescence dating of Quaternary red sand beds. A case study of coastal dunes in Sri Lanka. Earth Planet. Sci. Lett., 1986, 80, 139– 144.