The paper describes a novel technique to harvest 222Rn laden air from soil gas of natural origin ... more The paper describes a novel technique to harvest 222Rn laden air from soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a walk-in type 222Rn calibration chamber. The technique makes use of a soil probe of about 1 m to draw soil gas, through a dehumidifier and a delay volume, using an air pump to fill the calibration chamber. 222Rn concentration in the range of a few hundred Bq m−3 to a few tens of kBq m−3 was easily attained in the chamber of volume 22.7 m3 within a short pumping duration of 1 h. A new technique referred to as “semi-dynamic mode of operation” in which soil gas is injected into the calibration chamber at regular intervals to compensate for the loss of 222Rn due to decay and leak is discussed. Harvesting soil gas has many important advantages over the traditional methods of 222Rn generation for calibration experiments using finite sources such as solid flow-through, powdered emanation, and liquid sources. They are: (1) so...
Indoor radon and thoron concentrations have been measured using solid state nuclear track detecto... more Indoor radon and thoron concentrations have been measured using solid state nuclear track detector (LR-115 type-ІІ) based twin cup dosimeter with single and double entry deployed side by side. The measurements have been carried out in 50 dwellings of 8 different villages/towns situated in Saiha and Lawngtlai districts, Mizoram. Dwellings were selected primarily from the gamma level measured using Micro-R survey meter and the construction type of the building. The average concentrations of radon and thoron were found to be 75.76 Bq/m3 and 96.50 Bq/m3 for single entry dosimeter and 63.47 Bq/m3 and 19.79 Bq/m3 for double entry dosimeter. The single entry dosimeter was found to give more reliable observations than that of double entry in terms of trends of seasonal data and also on the theory behind the manufacturing qualities.
Activated charcoal is a well‑known adsorber of 222Rn and 220Rn gases. This property can be effect... more Activated charcoal is a well‑known adsorber of 222Rn and 220Rn gases. This property can be effectively used for remediation of these gases in the workplaces of uranium and thorium processing facilities. However, the adsorption on charcoal is sensitive to variation in temperature and humidity. The successful designing and characterization of adsorption systems require an adequate understanding of these sensitivities. The study has been carried out towards this end, to delineate the effect of relative humidity on the efficacy of 220Rn mitigations in a charcoal bed. Air carrying 220Rn from a Pylon source was passed through a column filled with coconut shell‑based granular activated charcoal. The relative humidity of the air was controlled, and the transmission characteristics were examined at relative humidity varying from 45% to 60%. The mitigation factor was found to decrease significantly with an increase of humidity in the air.
In an adjoining publication, we demonstrated the novel technique to harvest soil gas of natural o... more In an adjoining publication, we demonstrated the novel technique to harvest soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a large volume 222Rn calibration chamber. Its advantages over the use of conventional high strength 226Ra sources, such as the capability to serve as a non-depleting reservoir of 222Rn and achieve the desired concentration inside the calibration chamber within a very short time, devoid of radiation safety issues in source handling and licensing requirements from the regulatory authority, were discussed in detail. It was also demonstrated that stability in the 222Rn concentration in large calibration chambers could be achieved within ± 20% deviation from the desired value through a semi-dynamic mode of injection in which 222Rn laden air was periodically pumped to compensate for its loss due to leak and decay. The necessity of developing a theory for determining the appropriate periodicity of pumping was realized t...
IOP Conference Series: Materials Science and Engineering, 2021
GaN/InxGa1-xN/GaN superlattice (SL) has electric field at interfaces termed as interfacial polari... more GaN/InxGa1-xN/GaN superlattice (SL) has electric field at interfaces termed as interfacial polarization electric (IPE) field. In this work, effect of this electric field on cross-plane thermal conductivity (kcp) of the SL is investigated for Indium content x ≤ 0.3. IPE field revises phonon velocity which enhances interfacial scattering and thermal boundary resistance (TBR). This is due to unequal changes in specific heat and phonon velocity which leads to decrease in phonon transmission and more mismatches of acoustic properties of material. This reduces kcp. Room temperature kcp in presence (absence) of IPE field for GaN (10nm)/InxGa1-xN (5nm) SL are 4.652 (5.720) and 4.282 (5.221) Wm−1K−1 respectively, for x=0.1 and 0.3. This work demonstrates that electric field of nitride SL can be utilized to reduce k for optimum thermoelectric power production.
The data set include 7-day continuous measurement (daily as well as diurnal) of radon-222 gas at ... more The data set include 7-day continuous measurement (daily as well as diurnal) of radon-222 gas at 1-hour resolution collected at a high-altitude Physics Observatory at Gulmarg which is situated roughly 55 Km from Srinagar, the capital city of Jammu & Kashmir and lies in the Pir Panjals range of the Himalayas. The longitude and latitude of Gulmarg are 74◦24'E and 34◦03'N with a mean altitude of 2743.2 m. The data was obtained using a scintillation detector (RnDuo Monitor), developed by Bhabha Atomic Research Centre, Mumbai, India. The first column (Column A), shows time (in hours) where cell A3 represents 1:00 am, A4 represents 2:00 am and so on. Columns B-H show daily Radon variation while as rows B-H shows the hourly variation of radon measured in Becquerel per cubic metre. Column I shows the average values. Value of the Data: • The Gulmarg High Altitude observatory primarily records meteorological parameters. However, the observatory is also equipped with many other scientific instruments to detect and record various other parameters like particulate matter, atmospheric electricity, seismic activities etc. However, as of now, no data about radon gas is available, the knowledge of which can be instrumental to other researchers working at the observatory. • Radon gas is a known carcinogen (Samet and Eradze, 2000). In fact, it is the first cause of lung cancer among non-smokers and second among smokers (Darby et al., 2005; World Health Organization, 2010). Therefore, the data pertaining to radon concentration, are vital from the epidemiological perspective. • The observatory was recently equipped with an Electric Field Mill (EFM) to measure atmospheric electricity, which is known to be influenced by Radon gas (Chandrashekara et al., 2006; García-Talavera et al., 2001). The data set for radon concentration will definitely serve as a yardstick for this and other such research works.
Superior thermoelectric property requires high electrical conductivity ( $$\sigma$$ ), Seebeck co... more Superior thermoelectric property requires high electrical conductivity ( $$\sigma$$ ), Seebeck coefficient (S) but low thermal conductivity (k). GaN/InxGa1-xN/GaN superlattice (SL) has a strong interfacial polarization electric (IPE) field ~ 1 MV/cm at hetero-interfaces. Experiments reported that IPE field enhances S and $$\sigma$$ of the SL. In this paper, IPE field on thermal boundary resistance (TBR) and cross-plane thermal conductivity (kcp) of the SL is explored for indium contents x = 0.1 and 0.3 theoretically. IPE field revises phonon velocity causing enhanced boundary/interface scattering. Our result shows that TBR is enhanced (2.10–5. 30) ✕ 10–9 m2 KW−1 due to unequal changes in specific heat and phonon velocity on both sides of interface leading to decreased phonon transmission and acoustic properties of material become more dissimilar under IPE field. This reduced kcp. For GaN (10 nm)/InxGa1-xN (5 nm) SL, room-temperature (RT) kcp in the presence (absence) of IPE field is 4.652 (5.720) and 4.282 (5.221) Wm−1 K−1, respectively, for x = 0.1 and 0.3 proving more than 20% reduction. This work demonstrates that desired value of k can be achieved by tailoring interfacial polarization field of SL for optimum power production at RT and above.
IOP Conference Series: Materials Science and Engineering, 2020
AlxGa1-x N UV LED is a promising light source for water purification, diagnosis and sterilization... more AlxGa1-x N UV LED is a promising light source for water purification, diagnosis and sterilization of medical equipment's, document authentication, security checking and general lightings. The device suffers from efficiency droop due to a number of factors like Shockley Read Hall recombination (SRH), Auger recombination (AR), electron delocalization (ED) and electron leakage (EL).In this work, effect of temperature on electron leakage and efficiency droop of AlGaN UV LED is investigated. It is found that electron leakage takes place at high injection current and high temperature. Electron leakage can be reduced by minimizing self-heating effect in the AlGaN UV LED.
The paper describes a novel technique to harvest 222Rn laden air from soil gas of natural origin ... more The paper describes a novel technique to harvest 222Rn laden air from soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a walk-in type 222Rn calibration chamber. The technique makes use of a soil probe of about 1 m to draw soil gas, through a dehumidifier and a delay volume, using an air pump to fill the calibration chamber. 222Rn concentration in the range of a few hundred Bq m−3 to a few tens of kBq m−3 was easily attained in the chamber of volume 22.7 m3 within a short pumping duration of 1 h. A new technique referred to as “semi-dynamic mode of operation” in which soil gas is injected into the calibration chamber at regular intervals to compensate for the loss of 222Rn due to decay and leak is discussed. Harvesting soil gas has many important advantages over the traditional methods of 222Rn generation for calibration experiments using finite sources such as solid flow-through, powdered emanation, and liquid sources. They are: (1) so...
Indoor radon and thoron concentrations have been measured using solid state nuclear track detecto... more Indoor radon and thoron concentrations have been measured using solid state nuclear track detector (LR-115 type-ІІ) based twin cup dosimeter with single and double entry deployed side by side. The measurements have been carried out in 50 dwellings of 8 different villages/towns situated in Saiha and Lawngtlai districts, Mizoram. Dwellings were selected primarily from the gamma level measured using Micro-R survey meter and the construction type of the building. The average concentrations of radon and thoron were found to be 75.76 Bq/m3 and 96.50 Bq/m3 for single entry dosimeter and 63.47 Bq/m3 and 19.79 Bq/m3 for double entry dosimeter. The single entry dosimeter was found to give more reliable observations than that of double entry in terms of trends of seasonal data and also on the theory behind the manufacturing qualities.
Activated charcoal is a well‑known adsorber of 222Rn and 220Rn gases. This property can be effect... more Activated charcoal is a well‑known adsorber of 222Rn and 220Rn gases. This property can be effectively used for remediation of these gases in the workplaces of uranium and thorium processing facilities. However, the adsorption on charcoal is sensitive to variation in temperature and humidity. The successful designing and characterization of adsorption systems require an adequate understanding of these sensitivities. The study has been carried out towards this end, to delineate the effect of relative humidity on the efficacy of 220Rn mitigations in a charcoal bed. Air carrying 220Rn from a Pylon source was passed through a column filled with coconut shell‑based granular activated charcoal. The relative humidity of the air was controlled, and the transmission characteristics were examined at relative humidity varying from 45% to 60%. The mitigation factor was found to decrease significantly with an increase of humidity in the air.
In an adjoining publication, we demonstrated the novel technique to harvest soil gas of natural o... more In an adjoining publication, we demonstrated the novel technique to harvest soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a large volume 222Rn calibration chamber. Its advantages over the use of conventional high strength 226Ra sources, such as the capability to serve as a non-depleting reservoir of 222Rn and achieve the desired concentration inside the calibration chamber within a very short time, devoid of radiation safety issues in source handling and licensing requirements from the regulatory authority, were discussed in detail. It was also demonstrated that stability in the 222Rn concentration in large calibration chambers could be achieved within ± 20% deviation from the desired value through a semi-dynamic mode of injection in which 222Rn laden air was periodically pumped to compensate for its loss due to leak and decay. The necessity of developing a theory for determining the appropriate periodicity of pumping was realized t...
IOP Conference Series: Materials Science and Engineering, 2021
GaN/InxGa1-xN/GaN superlattice (SL) has electric field at interfaces termed as interfacial polari... more GaN/InxGa1-xN/GaN superlattice (SL) has electric field at interfaces termed as interfacial polarization electric (IPE) field. In this work, effect of this electric field on cross-plane thermal conductivity (kcp) of the SL is investigated for Indium content x ≤ 0.3. IPE field revises phonon velocity which enhances interfacial scattering and thermal boundary resistance (TBR). This is due to unequal changes in specific heat and phonon velocity which leads to decrease in phonon transmission and more mismatches of acoustic properties of material. This reduces kcp. Room temperature kcp in presence (absence) of IPE field for GaN (10nm)/InxGa1-xN (5nm) SL are 4.652 (5.720) and 4.282 (5.221) Wm−1K−1 respectively, for x=0.1 and 0.3. This work demonstrates that electric field of nitride SL can be utilized to reduce k for optimum thermoelectric power production.
The data set include 7-day continuous measurement (daily as well as diurnal) of radon-222 gas at ... more The data set include 7-day continuous measurement (daily as well as diurnal) of radon-222 gas at 1-hour resolution collected at a high-altitude Physics Observatory at Gulmarg which is situated roughly 55 Km from Srinagar, the capital city of Jammu & Kashmir and lies in the Pir Panjals range of the Himalayas. The longitude and latitude of Gulmarg are 74◦24'E and 34◦03'N with a mean altitude of 2743.2 m. The data was obtained using a scintillation detector (RnDuo Monitor), developed by Bhabha Atomic Research Centre, Mumbai, India. The first column (Column A), shows time (in hours) where cell A3 represents 1:00 am, A4 represents 2:00 am and so on. Columns B-H show daily Radon variation while as rows B-H shows the hourly variation of radon measured in Becquerel per cubic metre. Column I shows the average values. Value of the Data: • The Gulmarg High Altitude observatory primarily records meteorological parameters. However, the observatory is also equipped with many other scientific instruments to detect and record various other parameters like particulate matter, atmospheric electricity, seismic activities etc. However, as of now, no data about radon gas is available, the knowledge of which can be instrumental to other researchers working at the observatory. • Radon gas is a known carcinogen (Samet and Eradze, 2000). In fact, it is the first cause of lung cancer among non-smokers and second among smokers (Darby et al., 2005; World Health Organization, 2010). Therefore, the data pertaining to radon concentration, are vital from the epidemiological perspective. • The observatory was recently equipped with an Electric Field Mill (EFM) to measure atmospheric electricity, which is known to be influenced by Radon gas (Chandrashekara et al., 2006; García-Talavera et al., 2001). The data set for radon concentration will definitely serve as a yardstick for this and other such research works.
Superior thermoelectric property requires high electrical conductivity ( $$\sigma$$ ), Seebeck co... more Superior thermoelectric property requires high electrical conductivity ( $$\sigma$$ ), Seebeck coefficient (S) but low thermal conductivity (k). GaN/InxGa1-xN/GaN superlattice (SL) has a strong interfacial polarization electric (IPE) field ~ 1 MV/cm at hetero-interfaces. Experiments reported that IPE field enhances S and $$\sigma$$ of the SL. In this paper, IPE field on thermal boundary resistance (TBR) and cross-plane thermal conductivity (kcp) of the SL is explored for indium contents x = 0.1 and 0.3 theoretically. IPE field revises phonon velocity causing enhanced boundary/interface scattering. Our result shows that TBR is enhanced (2.10–5. 30) ✕ 10–9 m2 KW−1 due to unequal changes in specific heat and phonon velocity on both sides of interface leading to decreased phonon transmission and acoustic properties of material become more dissimilar under IPE field. This reduced kcp. For GaN (10 nm)/InxGa1-xN (5 nm) SL, room-temperature (RT) kcp in the presence (absence) of IPE field is 4.652 (5.720) and 4.282 (5.221) Wm−1 K−1, respectively, for x = 0.1 and 0.3 proving more than 20% reduction. This work demonstrates that desired value of k can be achieved by tailoring interfacial polarization field of SL for optimum power production at RT and above.
IOP Conference Series: Materials Science and Engineering, 2020
AlxGa1-x N UV LED is a promising light source for water purification, diagnosis and sterilization... more AlxGa1-x N UV LED is a promising light source for water purification, diagnosis and sterilization of medical equipment's, document authentication, security checking and general lightings. The device suffers from efficiency droop due to a number of factors like Shockley Read Hall recombination (SRH), Auger recombination (AR), electron delocalization (ED) and electron leakage (EL).In this work, effect of temperature on electron leakage and efficiency droop of AlGaN UV LED is investigated. It is found that electron leakage takes place at high injection current and high temperature. Electron leakage can be reduced by minimizing self-heating effect in the AlGaN UV LED.
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Papers by Bijay Sahoo