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Papers by Sabyasachi Paul

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Dec 31, 2023

Radiation Physics and Chemistry, Feb 29, 2024

Journal of Radioanalytical and Nuclear Chemistry, Oct 1, 2019

While measuring the neutron dose in accelerator radiation environment using CR-39 detector for ra... more While measuring the neutron dose in accelerator radiation environment using CR-39 detector for radiation protection purpose, LET (linear energy transfer) spectrometry method is implemented when the information about the radiation source term is unknown. In this work, the neutron dose has been measured for p+ 181 Ta reaction at different proton energies i.e. 8-20 MeV by LET spectrometry method using CR-39 detectors. The track density in CR-39 was found to increase exponentially with the proton energy and an empirical relation has been established. The dosimetric quantities viz. absorbed dose (D LET) and dose equivalent (H LET) were determined from the LET spectra and both these quantities were found to be increasing with the proton energy. Empirical relations were generated, which will be useful for predicting dose in similar radiation environment. The dosimetric data generated in this study would be useful for radiation protection of occupational workers working in the accelerator radiation environment.

Radiation Protection and Environment, Dec 31, 2022

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

European Physical Journal Plus, Oct 28, 2022

Radiation Physics and Chemistry

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Physical Review C, 2016

Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differentia... more Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differential neutron multiplicity distribution from heavy ion reactions (12 C + 165 Ho and 20 Ne + 165 Ho) at 10-30 MeV/u have been investigated in the framework of the semiclassical formalism for heavy ion reaction (henceforth termed "HION") developed earlier. HION follows the equilibration of a target+projectile composite system through the kinematics of two-body scattering. In the present work nuclear density distribution in the composite system is estimated in the relativistic mean field (RMF) approach. The nucleon-nucleon collision rates and subsequently the nucleon emission probability are calculated from this density distribution. A second approach based on a semiphenomenological formalism is also used for nuclear density distribution. Energy-angle distribution of neutron multiplicities calculated with this modified HION model coupled with multiple PEQ emission could reproduce the measured data of earlier workers in the projectile energy range of 10-30 MeV/u.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

Abstract The neutron spectral yields from the Li(p,n) reaction has been considered as an importan... more Abstract The neutron spectral yields from the Li(p,n) reaction has been considered as an important study due to its potential use as mono-energetic fast neutron source. This reaction has been studied at energies nearing Coulomb barrier for mono-energetic neutrons from 7Be ground state emissions and at energies beyond few tens of MeV to get the quasi mono-energetic fast neutrons, depending on their specific applications such as cross section studies, calibration of neutron detectors, etc. However, the number of measurements at proton energy of 8–20 MeV is sparse in the literature. In this energy range, the mono-energetic neutrons are strongly interfered by emissions from other excited states distorting the emission neutron spectra. Majority of the earlier measurements were carried out using carbon as the backing material during evaluation of neutron yields to minimize the interference of neutrons from the backing material. Here, a commonly used thick Ta target was explored as the backing material for the thin Li target and the neutron yields were measured with solid polymeric neutron track detector, CR-39. This is a passive technique and does not require any associated instrumentation during the irradiation process. This work presents the estimation of thin target neutron yields from Li target by subtracting the neutron yields contributed by the supporting material (Ta), which was separately measured in the same physical conditions.

Sabyasachi Paul, Maitreyee Nandy*, A. K. Mohanty, Y. K. Gambhir and P. K. Sarkar Health Physics D... more Sabyasachi Paul, Maitreyee Nandy*, A. K. Mohanty, Y. K. Gambhir and P. K. Sarkar Health Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, INDIA Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata -700064, INDIA Manipal Centre for Natural Sciences, Manipal University, Manipal 576104, INDIA Department of Physics, IIT Bombay, Powai, Mumbai 400076, INDIA . * email: maitreyee.nandy@saha.ac.in

Journal of Radioanalytical and Nuclear Chemistry, 2020

Rock aggregates are major ingredient of concrete used for shielding against ionising radiation ge... more Rock aggregates are major ingredient of concrete used for shielding against ionising radiation generated during the operation of nuclear particle accelerators. Their analysis for trace elements which may lead to neutron activation products during prolonged operation becomes important. Proper selection of ingredients helps in minimizing the radioactive concrete waste requiring disposal at the time of decommissioning.This work involves the collection of 42 samples of seven broad types of rock aggregates and their assessment for natural radioactivity (226 Ra, 232 Th and 40 K), lithium and other trace elements that may lead to the formation of gamma emitting, long lived neutron activation products.

Journal of Radioanalytical and Nuclear Chemistry, 2020

Cement is an important component of concrete used as a shielding material in nuclear accelerators... more Cement is an important component of concrete used as a shielding material in nuclear accelerators and reactors. Hence cement samples should be analysed for the presence of certain trace elements that may get activated by neutrons emitted during the production of radioisotopes in an accelerator, so as to minimize the low level radioactive waste to be handled during decommissioning. With this motivation the present work was undertaken and 44 samples of five broad classes of cements were analysed for natural radioactivity (226 Ra, 232 Th & 40 K) and trace elements capable of generating long lived gamma radioactivity due to neutron activation.

Journal of Radioanalytical and Nuclear Chemistry, 2020

Current research in the accelerator technology is focused towards achieving high energy, intense ... more Current research in the accelerator technology is focused towards achieving high energy, intense beams by minimizing conversion losses during beam acceleration. In such high current facilities, induced activity in structural materials become primary concern for radiation protection and materials like Ta and Nb, with low induced activity generation, high corrosion resistance characteristics are preferred along with conventional structural materials. In view of significant use of elements like Nb, Ta and Fe in the proton accelerators, a dose rate measurement and decay study has been carried out. The prompt γ-and neutron doses with residual activity profile from short and long lived isotopes were estimated using γ-ray spectrometric method.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

Abstract Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator envi... more Abstract Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator environment considering its enormous use in a proton accelerator. The Ta target has a unique advantage considering the generation of short half lived radionuclides upon interaction with protons. This advantage extends its use as the beam stopping material at various locations of an accelerator. However, this target has a varied range of reactions to produce neutrons and prompt gammas depending on proton energies. So in the present work, the neutron spectra were generated at various incident proton energies and neutron ambient dose equivalents were estimated close to the target projectile interaction at 90°with respect to the incident beam direction. A comparison of the spectral nature and doses were also done with measurements made by our earlier studies carried out at 0°. The comparison clearly showed that, apart from an increase in the low energy neutron yields at 90°, the overall yield distribution remains similar at both 0°and 90°angles with respect to the incoming beam direction. The ratio of the ambient neutron dose equivalent is found to reduce by a factor of 3–4 at 90°compared to 0°over the entire incident proton energy range. So, the dose equivalent ratio at two angles can be considered as independent of the incident projectile energy.

Journal of Radioanalytical and Nuclear Chemistry, 2019

Presently accelerator facilities emphasizes on generating charged particles with enhanced energy ... more Presently accelerator facilities emphasizes on generating charged particles with enhanced energy and flux. The radiation protection practices at these facilities are considered in civil engineering designs and strictly implemented through different administrative, access control measures (Sarkar in Radiat Meas 45:1476-1483, 2010). However, concern arises from induced activities, during maintenance and decommissioning stages, when sections of accelerator and shielding materials become highly radioactive. Major contribution of induced activity arises from stainless steel (SS-304) beam enclosures and Cu-dumps. Present work focuses on the generation of induced radioactivity profiles with delay counting of SS-304 and Cu along with instantaneous gamma and neutron dose rate measurements at various proton energies for source term estimation.

Physical Review C, 2017

The thick target neutron yield from a 16 O 6+ beam on a thick 27 Al target at 120-and 142-MeV (7.... more The thick target neutron yield from a 16 O 6+ beam on a thick 27 Al target at 120-and 142-MeV (7.5-and 8.8-MeV/nucleon, respectively) incident energies is presented and compared with theoretical calculations. The theoretical estimates for the yield of a high-energy neutron was obtained using a preequilibrium (PEQ) heavy-ion reaction model (HION), whereas that for the low-energy part was obtained using the standard evaporation models PACE4 and EMPIRE 3.2. In the present data a significant PEQ contribution, ∼2% to 3% of the evaporation contribution, is observed even at projectile energies below 10 MeV/nucleon. The measured energy spectrum of neutrons for E > 20 MeV (the predominant PEQ region) is in good agreement with the PEQ model code HION.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018

Abstract 181 Ta is a commonly used backing material for many targets in nuclear reaction studies.... more Abstract 181 Ta is a commonly used backing material for many targets in nuclear reaction studies. When the target thickness is less than the range of bombarded projectiles, the interaction via Ta(p,n) reactions in the backing can be a significant source of background. In this study, the neutron spectral yields from the reaction of protons of different energies (between 6 to 20 MeV) with a thick Ta target were determined using CR-39 detectors. The results from this study can be used as a correction factor in such situations. The parameters of registered tracks in CR-39 were analysed using an in-house image analysing program autoTRAK_n and then to derive the associated dose values. The spectral yields obtained experimentally were compared with those obtained from the theoretical calculations. The neutron yield was found to increase with increase in projectile energy mainly due to the opening of reaction channels from (p, n) to (p, 3n).

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Dec 31, 2023

Radiation Physics and Chemistry, Feb 29, 2024

Journal of Radioanalytical and Nuclear Chemistry, Oct 1, 2019

While measuring the neutron dose in accelerator radiation environment using CR-39 detector for ra... more While measuring the neutron dose in accelerator radiation environment using CR-39 detector for radiation protection purpose, LET (linear energy transfer) spectrometry method is implemented when the information about the radiation source term is unknown. In this work, the neutron dose has been measured for p+ 181 Ta reaction at different proton energies i.e. 8-20 MeV by LET spectrometry method using CR-39 detectors. The track density in CR-39 was found to increase exponentially with the proton energy and an empirical relation has been established. The dosimetric quantities viz. absorbed dose (D LET) and dose equivalent (H LET) were determined from the LET spectra and both these quantities were found to be increasing with the proton energy. Empirical relations were generated, which will be useful for predicting dose in similar radiation environment. The dosimetric data generated in this study would be useful for radiation protection of occupational workers working in the accelerator radiation environment.

Radiation Protection and Environment, Dec 31, 2022

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

European Physical Journal Plus, Oct 28, 2022

Radiation Physics and Chemistry

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Physical Review C, 2016

Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differentia... more Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differential neutron multiplicity distribution from heavy ion reactions (12 C + 165 Ho and 20 Ne + 165 Ho) at 10-30 MeV/u have been investigated in the framework of the semiclassical formalism for heavy ion reaction (henceforth termed "HION") developed earlier. HION follows the equilibration of a target+projectile composite system through the kinematics of two-body scattering. In the present work nuclear density distribution in the composite system is estimated in the relativistic mean field (RMF) approach. The nucleon-nucleon collision rates and subsequently the nucleon emission probability are calculated from this density distribution. A second approach based on a semiphenomenological formalism is also used for nuclear density distribution. Energy-angle distribution of neutron multiplicities calculated with this modified HION model coupled with multiple PEQ emission could reproduce the measured data of earlier workers in the projectile energy range of 10-30 MeV/u.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

Abstract The neutron spectral yields from the Li(p,n) reaction has been considered as an importan... more Abstract The neutron spectral yields from the Li(p,n) reaction has been considered as an important study due to its potential use as mono-energetic fast neutron source. This reaction has been studied at energies nearing Coulomb barrier for mono-energetic neutrons from 7Be ground state emissions and at energies beyond few tens of MeV to get the quasi mono-energetic fast neutrons, depending on their specific applications such as cross section studies, calibration of neutron detectors, etc. However, the number of measurements at proton energy of 8–20 MeV is sparse in the literature. In this energy range, the mono-energetic neutrons are strongly interfered by emissions from other excited states distorting the emission neutron spectra. Majority of the earlier measurements were carried out using carbon as the backing material during evaluation of neutron yields to minimize the interference of neutrons from the backing material. Here, a commonly used thick Ta target was explored as the backing material for the thin Li target and the neutron yields were measured with solid polymeric neutron track detector, CR-39. This is a passive technique and does not require any associated instrumentation during the irradiation process. This work presents the estimation of thin target neutron yields from Li target by subtracting the neutron yields contributed by the supporting material (Ta), which was separately measured in the same physical conditions.

Sabyasachi Paul, Maitreyee Nandy*, A. K. Mohanty, Y. K. Gambhir and P. K. Sarkar Health Physics D... more Sabyasachi Paul, Maitreyee Nandy*, A. K. Mohanty, Y. K. Gambhir and P. K. Sarkar Health Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, INDIA Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata -700064, INDIA Manipal Centre for Natural Sciences, Manipal University, Manipal 576104, INDIA Department of Physics, IIT Bombay, Powai, Mumbai 400076, INDIA . * email: maitreyee.nandy@saha.ac.in

Journal of Radioanalytical and Nuclear Chemistry, 2020

Rock aggregates are major ingredient of concrete used for shielding against ionising radiation ge... more Rock aggregates are major ingredient of concrete used for shielding against ionising radiation generated during the operation of nuclear particle accelerators. Their analysis for trace elements which may lead to neutron activation products during prolonged operation becomes important. Proper selection of ingredients helps in minimizing the radioactive concrete waste requiring disposal at the time of decommissioning.This work involves the collection of 42 samples of seven broad types of rock aggregates and their assessment for natural radioactivity (226 Ra, 232 Th and 40 K), lithium and other trace elements that may lead to the formation of gamma emitting, long lived neutron activation products.

Journal of Radioanalytical and Nuclear Chemistry, 2020

Cement is an important component of concrete used as a shielding material in nuclear accelerators... more Cement is an important component of concrete used as a shielding material in nuclear accelerators and reactors. Hence cement samples should be analysed for the presence of certain trace elements that may get activated by neutrons emitted during the production of radioisotopes in an accelerator, so as to minimize the low level radioactive waste to be handled during decommissioning. With this motivation the present work was undertaken and 44 samples of five broad classes of cements were analysed for natural radioactivity (226 Ra, 232 Th & 40 K) and trace elements capable of generating long lived gamma radioactivity due to neutron activation.

Journal of Radioanalytical and Nuclear Chemistry, 2020

Current research in the accelerator technology is focused towards achieving high energy, intense ... more Current research in the accelerator technology is focused towards achieving high energy, intense beams by minimizing conversion losses during beam acceleration. In such high current facilities, induced activity in structural materials become primary concern for radiation protection and materials like Ta and Nb, with low induced activity generation, high corrosion resistance characteristics are preferred along with conventional structural materials. In view of significant use of elements like Nb, Ta and Fe in the proton accelerators, a dose rate measurement and decay study has been carried out. The prompt γ-and neutron doses with residual activity profile from short and long lived isotopes were estimated using γ-ray spectrometric method.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

Abstract Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator envi... more Abstract Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator environment considering its enormous use in a proton accelerator. The Ta target has a unique advantage considering the generation of short half lived radionuclides upon interaction with protons. This advantage extends its use as the beam stopping material at various locations of an accelerator. However, this target has a varied range of reactions to produce neutrons and prompt gammas depending on proton energies. So in the present work, the neutron spectra were generated at various incident proton energies and neutron ambient dose equivalents were estimated close to the target projectile interaction at 90°with respect to the incident beam direction. A comparison of the spectral nature and doses were also done with measurements made by our earlier studies carried out at 0°. The comparison clearly showed that, apart from an increase in the low energy neutron yields at 90°, the overall yield distribution remains similar at both 0°and 90°angles with respect to the incoming beam direction. The ratio of the ambient neutron dose equivalent is found to reduce by a factor of 3–4 at 90°compared to 0°over the entire incident proton energy range. So, the dose equivalent ratio at two angles can be considered as independent of the incident projectile energy.

Journal of Radioanalytical and Nuclear Chemistry, 2019

Presently accelerator facilities emphasizes on generating charged particles with enhanced energy ... more Presently accelerator facilities emphasizes on generating charged particles with enhanced energy and flux. The radiation protection practices at these facilities are considered in civil engineering designs and strictly implemented through different administrative, access control measures (Sarkar in Radiat Meas 45:1476-1483, 2010). However, concern arises from induced activities, during maintenance and decommissioning stages, when sections of accelerator and shielding materials become highly radioactive. Major contribution of induced activity arises from stainless steel (SS-304) beam enclosures and Cu-dumps. Present work focuses on the generation of induced radioactivity profiles with delay counting of SS-304 and Cu along with instantaneous gamma and neutron dose rate measurements at various proton energies for source term estimation.

Physical Review C, 2017

The thick target neutron yield from a 16 O 6+ beam on a thick 27 Al target at 120-and 142-MeV (7.... more The thick target neutron yield from a 16 O 6+ beam on a thick 27 Al target at 120-and 142-MeV (7.5-and 8.8-MeV/nucleon, respectively) incident energies is presented and compared with theoretical calculations. The theoretical estimates for the yield of a high-energy neutron was obtained using a preequilibrium (PEQ) heavy-ion reaction model (HION), whereas that for the low-energy part was obtained using the standard evaporation models PACE4 and EMPIRE 3.2. In the present data a significant PEQ contribution, ∼2% to 3% of the evaporation contribution, is observed even at projectile energies below 10 MeV/nucleon. The measured energy spectrum of neutrons for E > 20 MeV (the predominant PEQ region) is in good agreement with the PEQ model code HION.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018

Abstract 181 Ta is a commonly used backing material for many targets in nuclear reaction studies.... more Abstract 181 Ta is a commonly used backing material for many targets in nuclear reaction studies. When the target thickness is less than the range of bombarded projectiles, the interaction via Ta(p,n) reactions in the backing can be a significant source of background. In this study, the neutron spectral yields from the reaction of protons of different energies (between 6 to 20 MeV) with a thick Ta target were determined using CR-39 detectors. The results from this study can be used as a correction factor in such situations. The parameters of registered tracks in CR-39 were analysed using an in-house image analysing program autoTRAK_n and then to derive the associated dose values. The spectral yields obtained experimentally were compared with those obtained from the theoretical calculations. The neutron yield was found to increase with increase in projectile energy mainly due to the opening of reaction channels from (p, n) to (p, 3n).