Veena Joshi

Measurements of Radon Flux and Soil-Gas Radon Concentration along the Main Central Thrust, Garhwal Himalaya, Using SRM and RAD7 Detectors

Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. 222Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then 222Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m−3 with geometrical mean value of 302 ± 84 Bq·m−3. Th significance of this work is its usefulness from radiation protection point of view.

Study of natural radionuclide and absorbed gamma dose in Ukhimath area of Garhwal Himalaya, India

Natural radiation is the largest contributor to the collective radiation dose of the world population. It is widely distributed in different geological formations such as soil, rocks, air and groundwater. In the present investigation, (226)Ra, (232)Th and (40)K were measured in soil samples of the Ukhimath region of Garhwal Himalaya, India using NaI(Tl) gamma-ray spectrometry. The activity concentrations of naturally occurring radionuclides (226)Ra, (232)Th and (40)K were found to vary from 38.4 ± 6.1 to 141.7 ± 11.9 Bq kg(-1) with an average of 80.5 Bq kg(-1), 57.0 ± 7.5 to 155.9 ± 12.4 Bq kg(-1) with an average of 118.9 Bq kg(-1) and 9.0 ± 3.0 to 672.8 ± 25.9 Bq kg(-1) with an average of 341 Bq kg(-1), respectively. The total absorbed gamma dose rate varies from 70.4 to 169.1 nGy h(-1) with an average of 123.4 nGy h(-1). This study is important to generate a baseline data of radiation exposure in the area. Health hazard effects due to natural radiation exposure are discussed in details.

Variations in radon concentration in groundwater of Kumaon Himalaya, India.

The radon content in groundwater sources depends on the radium concentration in the rock of the aquifer. Radon was measured in water in many parts of the world, mostly for the risk assessment due to consumption of drinking water. The exposure to radon through drinking water is largely by inhalation and ingestion. Airborne radon can be released during normal household activities and can pose a greater potential health risk than radon ingested with water. Transport of radon through soil and bedrock by water depends mainly on the percolation of water through the pores and along fracture planes of bedrock. In this study, the radon concentration in water from springs and hand pumps of Kumaun Himalaya, India was measured using the radon emanometry technique. Radon concentration was found to vary from 1 to 392 Bq l(-1) with a mean of 50 Bq l(-1) in groundwater in different lithotectonic units. The radon level was found to be higher in the area consisting of granite, quartz porphyry, schist, phyllites and lowest in the area having sedimentary rocks, predominantly dominated by quartzite rocks.

Structural Modifications of PMMA and PMMA/CNT Matrix by Swift Heavy Ions Irradiation

The effects of multi walled carbon nanotube (MWCNT) as well as swift heavy ion (SHI) irradiation on the optical and electrical properties of polymethyl methacrylate (PMMA) have been investigated. The self-sustaining films of non-conducting PMMA and PMMA/MWCNT nanocomposites were irradiated under vacuum with 50 MeV Lithium (Li3+) and 80 MeV Carbon (C5+) at 1×1013 ion fluence. One peak photoluminescence (PL) band was found in Raman spectra. All these results were explained on the basis of charge transfer complex (CTC).

Modifications induced by O+8 ion beam to Lexan polycarbonate

High-energy ion beam irradiation of polymer is an effective technique to enhance the optical, structural and mechanical properties. Lexan polycarbonate films were irradiated by oxygen ions (energy 100 MeV, charge state O+8) with fluence varying from 3×1010 to 3×1012 ions/cm2. Ion beam-induced optical and structural modifications were studied by ultraviolet–visible (UV–Vis), X-ray diffractometer and Fourier Transform Infrared (FTIR) spectroscopy. It is observed that optical absorption increases with increasing fluencies. The absorption edge was also found to shift from the UV region to the visible region. Value of band gap shows a decreasing trend with increasing ion fluences. The correlation between the optical band gap and number of carbon atoms inside the carbon clusters embedded in the network of Lexan has been discussed. X-ray Diffraction (XRD) analyses show the significant change in crystallinity with fluences. FTIR spectra show that the intensity of the absorption bands of Lexan polymer decreases after ion beam irradiation.

Effect of 50 MeV Li+3 and 80 MeV C+5 ions’ beam irradiation on the optical, structural, chemical and surface topographic properties of PMMA films

ABSTRACT The self-standing films of polymethyl methacrylate (PMMA) were irradiated under vacuum with 50 MeV lithium (Li3+) and 80 MeV carbon (C5+) ions to the fluences of 3 × 1014, 1 × 1015, 1 × 1016 and 1 × 1017 ions µm−2. The pristine and irradiated samples of PMMA films were studied by using ultraviolet–visible (UV–Vis) spectrophotometry, Fourier transform infrared, X-ray diffractrometer and atomic force microscopy. With increasing ion fluence of swift heavy ion (SHI), PMMA suffers degradation, UV–Vis spectra show a shift in the absorption band from the UV towards visible, attributing the formation of the modified system of bonds. Eg and Ea decrease with increasing ion fluence. The size of crystallite and crystallinity percentage decreases with increasing ion fluence. With SHI irradiation, the intensity of IR bands and characteristic bands of different functional groups are found to shift drastically. The change in (Eg) and (N) in carbon cluster is calculated. Shifting of the absorption band from the UV towards visible along with optical activity and as a result of irradiation, some defects are created in the polymer causing the formation of conjugated bonds and carbon clusters in the polymer, which in turn lead to the modification in optical properties that could be useful in the fabrication of optoelectronic devices, gas sensing, electromagnetic shielding and drug delivery.