The kinetic analyses are quite important when it comes to understanding the particle behavior in ... more The kinetic analyses are quite important when it comes to understanding the particle behavior in any device as they start to deviate from a continuum nature. In the present study, kinetic simulations are performed using the particle-in-cell method to analyze the behavior of ions inside a cylindrical inertial electrostatic confinement fusion (IECF) device which is being developed as a tabletop neutron source. Here, the lighter ions, like deuterium, are accelerated by applying an electrostatic field between the chamber wall (anode) and the cathode (cylindrical gridded wire), placed at the center of the device. The plasma potential profiles obtained from the simulated results indicate the formation of multiple potential well structures inside the cathode grid depending upon the applied cathode potential (from -1 to -5 kV). The ion density at the core region of the device is found to be of the order of 10^{16}m^{-3}, which closely resembles the experimental observations. Spatial variati...
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • Used an ingenious helium ion source to produce self-organized carbon nanostructure on graphite surface. • FESEM results confirm the formation of multi-modal spherical and elongated agglomerated structures. • AFM micrographs of irradiated samples also display rounded structures with the evidence of an increase in surface roughness with the increase in ion pulses. • The Raman study reads a decrease in the La value after ion irradiation and suggests a loss in crystallinity of the irradiated samples.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
The adaption of new generation portable neutron sources has been increasingly marked in a wide ra... more The adaption of new generation portable neutron sources has been increasingly marked in a wide range of research fields compared to the large-scale neutron generators. In this context, we have successfully demonstrated some of the essential parameters required for the emission of 2.45 MeV DD fusion neutrons from a steady state portable linear neutron source based on
An experiment on the formation of virtual electrode and ion sheath characteristics has been carri... more An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from-1000 to-5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper.
Abstract This paper studies the influence of helium ion irradiation on morphological and structur... more Abstract This paper studies the influence of helium ion irradiation on morphological and structural properties of graphite samples. The helium ions emanated from a plasma focus device have been used to irradiate graphite samples by varying the number of ion pulses. The effect of radiation induced changes in morphology and structure are examined by using optical microscopy, atomic force microscopy, transmission electron microscopy along with selected area electron diffraction and x-ray diffraction. A distinct change in the surface topography is marked in the case of the ion irradiated samples when viewed under the optical microscope. The micrographs of the ion irradiated samples confirm mostly rounded and sparely elongated type of structures arising due to intense melting and local ablation accompanied with ejection of graphite melts that depends upon the ion fluence. The atomic force microscopy images also reveal the formation of globules having sizes ∼50–200 nm which are the agglomeration of small individual clusters. Transmission electron micrographs of the ion irradiated samples furnish that the diameter of these individual small clusters are ∼10.4 nm. Moreover, selected area electron diffraction patterns corroborate that the ion irradiated sample retains its crystalline nature, even after exposure to larger helium ion pulses. It is noticed from the x-ray diffraction patterns that some new phases are developed in the case of ion irradiated sample.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • Deuterium plasma of a cylindrical inertial electrostatic confinement fusion device has been characterised using Langmuir probe and OES. • Plasma temperature is 3 eV in the case of hot cathode discharge whereas 10 eV in the case of cold cathode discharge. • The plasma density is two to three orders more in case of the hot cathode discharge than the cold cathode discharge. • The discharge modes such as "star" and "jet" are witnessed in the case of cold cathode discharge. • The observation of spontaneous oscillation along with the harmonics has been reported.
h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial ... more h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial electrostatic confinement fusion scheme. • The voltage and current that is to be applied to the grid is computed theoretically. • Neutron production rate is theoretically estimated and found to be of the order of 10 7-10 8 neutrons/s. • Electric potential distribution and ion trajectories are studied using SIMION code. • Optimized condition for the inner grid transparency has been found out.
ABSTRACT Energetic and high fluence helium ions emitted in a plasma focus device have been used s... more ABSTRACT Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed.
The kinetic analyses are quite important when it comes to understanding the particle behavior in ... more The kinetic analyses are quite important when it comes to understanding the particle behavior in any device as they start to deviate from a continuum nature. In the present study, kinetic simulations are performed using the particle-in-cell method to analyze the behavior of ions inside a cylindrical inertial electrostatic confinement fusion (IECF) device which is being developed as a tabletop neutron source. Here, the lighter ions, like deuterium, are accelerated by applying an electrostatic field between the chamber wall (anode) and the cathode (cylindrical gridded wire), placed at the center of the device. The plasma potential profiles obtained from the simulated results indicate the formation of multiple potential well structures inside the cathode grid depending upon the applied cathode potential (from −1 to −5 kV). The ion density at the core region of the device is found to be of the order of 10 16 m −3 , which closely resembles the experimental observations. Spatial variation of ion energy distribution function has been measured in order to observe the characteristics of ions at different cathode voltages. Finally, the simulated results are compared and found to be in good agreement with the experimental profiles. The present analysis can serve as a reference guide to optimize the technological parameters of the discharge process in IECF devices.
This paper studies the influence of helium ion irradiation on morphological and structural proper... more This paper studies the influence of helium ion irradiation on morphological and structural properties of graphite samples. The helium ions emanated from a plasma focus device have been used to irradiate graphite samples by varying the number of ion pulses. The effect of radiation induced changes in morphology and structure are examined by using optical microscopy, atomic force microscopy, transmission electron microscopy along with selected area electron diffraction and x-ray diffraction. A distinct change in the surface topography is marked in the case of the ion irradiated samples when viewed under the optical microscope. The micrographs of the ion irradiated samples confirm mostly rounded and sparely elongated type of structures arising due to intense melting and local ablation accompanied with ejection of graphite melts that depends upon the ion fluence. The atomic force microscopy images also reveal the formation of globules having sizes ∼50-200 nm which are the agglomeration of small individual clusters. Transmission electron micrographs of the ion irradiated samples furnish that the diameter of these individual small clusters are ∼10.4 nm. Moreover, selected area electron diffraction patterns corroborate that the ion irradiated sample retains its crystalline nature, even after exposure to larger helium ion pulses. It is noticed from the x-ray diffraction patterns that some new phases are developed in the case of ion irradiated sample.
The adaption of new generation portable neutron sources has been increasingly marked in a wide ra... more The adaption of new generation portable neutron sources has been increasingly marked in a wide range of research fields compared to the large-scale neutron generators. In this context, we have successfully demonstrated some essential parameters required for the emission of 2.45 MeV DD fusion neutrons from a steady state portable linear neutron source based on inertial electrostatic confinement scheme. The parameters that control the production of neutrons are the working pressure of the fuel gas, applied voltage, measured current and cathode geometries. The neutrons emitted from the source are confirmed using neutron monitor, bubble dosimeters, nuclear track detectors, and He-3 proportional counter. Presently, the device produces neutrons up to the order of ∼ 10 6 n/sec at discharge voltage ranging from-60 kV to-80 kV, and discharge current of 20 mA to 30 mA.
Deuterium plasma has been produced in a cylindrical inertial electrostatic confinement fusion dev... more Deuterium plasma has been produced in a cylindrical inertial electrostatic confinement fusion device using hot and cold cathode discharges and the plasma parameters are determined by employing an electrostatic probe. The plasma temperature and density are estimated at optimum experimental conditions and it is noted that the plasma temperature is 3 eV in the case of hot cathode discharge whereas 10 eV in the case of the cold cathode discharge. The plasma density as determined is two orders more in the case of the hot cathode discharge than the other. The probe is also used to observe the ion oscillation in the negative potential well that is formed in between the cathode grid and chamber (anode). The observation of spontaneous oscillation along with the harmonics has been reported.
h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial ... more h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial electrostatic confinement fusion scheme. • The voltage and current that is to be applied to the grid is computed theoretically. • Neutron production rate is theoretically estimated and found to be of the order of 10 7-10 8 neutrons/s. • Electric potential distribution and ion trajectories are studied using SIMION code. • Optimized condition for the inner grid transparency has been found out. a b s t r a c t In this paper, we present the design of a linear neutron source based on the concept of inertial electrostatic confinement fusion. The source mainly comprises of a concentric coaxial cylindrical grid assembly housed inside a double walled cylindrical vacuum chamber, a gas injection system, a high voltage feedthrough and a high voltage negative polarity power supply. The inner grid will be kept at a high negative potential with respect to the outer grid that will be grounded. The effect of grid transparency on electric potential distribution and ion trajectories has been studied using SIMION. A diffuse deuterium plasma will be initially created by making filament discharge and subsequently, on application of high negative voltage to the inner grid, deuterons will be accelerated towards the axis of the device. These deuterons will oscillate in the negative potential and consequently fuse in between the grids to produce neutrons. This source is expected to produce 10 7-10 8 neutrons/s. The proposed linear neutron source will be operated both in the continuous and pulse modes and it will be utilized for a few near term applications namely fusion reactor material studies and explosive detection.
The effects of helium ion irradiation on the graphite surface are studied by employing a plasma f... more The effects of helium ion irradiation on the graphite surface are studied by employing a plasma focus device. The device emits helium ion pulse having energies in the range of a few keV to a few MeV and flux on the order of 10 25 m −2 s −1 at 60 mm axial position from the anode tip. The field emission scanning electron microscopy confirms the formation of multi-modal spherical and elongated agglomerated structures on irradiated samples surface with increase in agglomerate size with increasing number of irradiation shots. The transient annealing in each irradiation was not enough to cause the Oswald ripening or sintering of particles into bigger particle or crystal size but only resulted in clustering. The atomic force micrographs reveal an increase in average surface roughness with increasing ion irradiation. The Raman study demonstrates increase in disordered D peak along with reduced crystallite size (L a) with increasing number of irradiation shots.
Energetic and high fluence helium ions emitted in a plasma focus device have been used successful... more Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed.
An experiment on the formation of virtual electrode and ion sheath characteristics has been carri... more An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from-1000 to-5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper. Published under license by AIP Publishing. https://doi.
The kinetic analyses are quite important when it comes to understanding the particle behavior in ... more The kinetic analyses are quite important when it comes to understanding the particle behavior in any device as they start to deviate from a continuum nature. In the present study, kinetic simulations are performed using the particle-in-cell method to analyze the behavior of ions inside a cylindrical inertial electrostatic confinement fusion (IECF) device which is being developed as a tabletop neutron source. Here, the lighter ions, like deuterium, are accelerated by applying an electrostatic field between the chamber wall (anode) and the cathode (cylindrical gridded wire), placed at the center of the device. The plasma potential profiles obtained from the simulated results indicate the formation of multiple potential well structures inside the cathode grid depending upon the applied cathode potential (from -1 to -5 kV). The ion density at the core region of the device is found to be of the order of 10^{16}m^{-3}, which closely resembles the experimental observations. Spatial variati...
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • Used an ingenious helium ion source to produce self-organized carbon nanostructure on graphite surface. • FESEM results confirm the formation of multi-modal spherical and elongated agglomerated structures. • AFM micrographs of irradiated samples also display rounded structures with the evidence of an increase in surface roughness with the increase in ion pulses. • The Raman study reads a decrease in the La value after ion irradiation and suggests a loss in crystallinity of the irradiated samples.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
The adaption of new generation portable neutron sources has been increasingly marked in a wide ra... more The adaption of new generation portable neutron sources has been increasingly marked in a wide range of research fields compared to the large-scale neutron generators. In this context, we have successfully demonstrated some of the essential parameters required for the emission of 2.45 MeV DD fusion neutrons from a steady state portable linear neutron source based on
An experiment on the formation of virtual electrode and ion sheath characteristics has been carri... more An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from-1000 to-5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper.
Abstract This paper studies the influence of helium ion irradiation on morphological and structur... more Abstract This paper studies the influence of helium ion irradiation on morphological and structural properties of graphite samples. The helium ions emanated from a plasma focus device have been used to irradiate graphite samples by varying the number of ion pulses. The effect of radiation induced changes in morphology and structure are examined by using optical microscopy, atomic force microscopy, transmission electron microscopy along with selected area electron diffraction and x-ray diffraction. A distinct change in the surface topography is marked in the case of the ion irradiated samples when viewed under the optical microscope. The micrographs of the ion irradiated samples confirm mostly rounded and sparely elongated type of structures arising due to intense melting and local ablation accompanied with ejection of graphite melts that depends upon the ion fluence. The atomic force microscopy images also reveal the formation of globules having sizes ∼50–200 nm which are the agglomeration of small individual clusters. Transmission electron micrographs of the ion irradiated samples furnish that the diameter of these individual small clusters are ∼10.4 nm. Moreover, selected area electron diffraction patterns corroborate that the ion irradiated sample retains its crystalline nature, even after exposure to larger helium ion pulses. It is noticed from the x-ray diffraction patterns that some new phases are developed in the case of ion irradiated sample.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • Deuterium plasma of a cylindrical inertial electrostatic confinement fusion device has been characterised using Langmuir probe and OES. • Plasma temperature is 3 eV in the case of hot cathode discharge whereas 10 eV in the case of cold cathode discharge. • The plasma density is two to three orders more in case of the hot cathode discharge than the cold cathode discharge. • The discharge modes such as "star" and "jet" are witnessed in the case of cold cathode discharge. • The observation of spontaneous oscillation along with the harmonics has been reported.
h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial ... more h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial electrostatic confinement fusion scheme. • The voltage and current that is to be applied to the grid is computed theoretically. • Neutron production rate is theoretically estimated and found to be of the order of 10 7-10 8 neutrons/s. • Electric potential distribution and ion trajectories are studied using SIMION code. • Optimized condition for the inner grid transparency has been found out.
ABSTRACT Energetic and high fluence helium ions emitted in a plasma focus device have been used s... more ABSTRACT Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed.
The kinetic analyses are quite important when it comes to understanding the particle behavior in ... more The kinetic analyses are quite important when it comes to understanding the particle behavior in any device as they start to deviate from a continuum nature. In the present study, kinetic simulations are performed using the particle-in-cell method to analyze the behavior of ions inside a cylindrical inertial electrostatic confinement fusion (IECF) device which is being developed as a tabletop neutron source. Here, the lighter ions, like deuterium, are accelerated by applying an electrostatic field between the chamber wall (anode) and the cathode (cylindrical gridded wire), placed at the center of the device. The plasma potential profiles obtained from the simulated results indicate the formation of multiple potential well structures inside the cathode grid depending upon the applied cathode potential (from −1 to −5 kV). The ion density at the core region of the device is found to be of the order of 10 16 m −3 , which closely resembles the experimental observations. Spatial variation of ion energy distribution function has been measured in order to observe the characteristics of ions at different cathode voltages. Finally, the simulated results are compared and found to be in good agreement with the experimental profiles. The present analysis can serve as a reference guide to optimize the technological parameters of the discharge process in IECF devices.
This paper studies the influence of helium ion irradiation on morphological and structural proper... more This paper studies the influence of helium ion irradiation on morphological and structural properties of graphite samples. The helium ions emanated from a plasma focus device have been used to irradiate graphite samples by varying the number of ion pulses. The effect of radiation induced changes in morphology and structure are examined by using optical microscopy, atomic force microscopy, transmission electron microscopy along with selected area electron diffraction and x-ray diffraction. A distinct change in the surface topography is marked in the case of the ion irradiated samples when viewed under the optical microscope. The micrographs of the ion irradiated samples confirm mostly rounded and sparely elongated type of structures arising due to intense melting and local ablation accompanied with ejection of graphite melts that depends upon the ion fluence. The atomic force microscopy images also reveal the formation of globules having sizes ∼50-200 nm which are the agglomeration of small individual clusters. Transmission electron micrographs of the ion irradiated samples furnish that the diameter of these individual small clusters are ∼10.4 nm. Moreover, selected area electron diffraction patterns corroborate that the ion irradiated sample retains its crystalline nature, even after exposure to larger helium ion pulses. It is noticed from the x-ray diffraction patterns that some new phases are developed in the case of ion irradiated sample.
The adaption of new generation portable neutron sources has been increasingly marked in a wide ra... more The adaption of new generation portable neutron sources has been increasingly marked in a wide range of research fields compared to the large-scale neutron generators. In this context, we have successfully demonstrated some essential parameters required for the emission of 2.45 MeV DD fusion neutrons from a steady state portable linear neutron source based on inertial electrostatic confinement scheme. The parameters that control the production of neutrons are the working pressure of the fuel gas, applied voltage, measured current and cathode geometries. The neutrons emitted from the source are confirmed using neutron monitor, bubble dosimeters, nuclear track detectors, and He-3 proportional counter. Presently, the device produces neutrons up to the order of ∼ 10 6 n/sec at discharge voltage ranging from-60 kV to-80 kV, and discharge current of 20 mA to 30 mA.
Deuterium plasma has been produced in a cylindrical inertial electrostatic confinement fusion dev... more Deuterium plasma has been produced in a cylindrical inertial electrostatic confinement fusion device using hot and cold cathode discharges and the plasma parameters are determined by employing an electrostatic probe. The plasma temperature and density are estimated at optimum experimental conditions and it is noted that the plasma temperature is 3 eV in the case of hot cathode discharge whereas 10 eV in the case of the cold cathode discharge. The plasma density as determined is two orders more in the case of the hot cathode discharge than the other. The probe is also used to observe the ion oscillation in the negative potential well that is formed in between the cathode grid and chamber (anode). The observation of spontaneous oscillation along with the harmonics has been reported.
h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial ... more h i g h l i g h t s • This paper reports the design of a linear neutron source based on inertial electrostatic confinement fusion scheme. • The voltage and current that is to be applied to the grid is computed theoretically. • Neutron production rate is theoretically estimated and found to be of the order of 10 7-10 8 neutrons/s. • Electric potential distribution and ion trajectories are studied using SIMION code. • Optimized condition for the inner grid transparency has been found out. a b s t r a c t In this paper, we present the design of a linear neutron source based on the concept of inertial electrostatic confinement fusion. The source mainly comprises of a concentric coaxial cylindrical grid assembly housed inside a double walled cylindrical vacuum chamber, a gas injection system, a high voltage feedthrough and a high voltage negative polarity power supply. The inner grid will be kept at a high negative potential with respect to the outer grid that will be grounded. The effect of grid transparency on electric potential distribution and ion trajectories has been studied using SIMION. A diffuse deuterium plasma will be initially created by making filament discharge and subsequently, on application of high negative voltage to the inner grid, deuterons will be accelerated towards the axis of the device. These deuterons will oscillate in the negative potential and consequently fuse in between the grids to produce neutrons. This source is expected to produce 10 7-10 8 neutrons/s. The proposed linear neutron source will be operated both in the continuous and pulse modes and it will be utilized for a few near term applications namely fusion reactor material studies and explosive detection.
The effects of helium ion irradiation on the graphite surface are studied by employing a plasma f... more The effects of helium ion irradiation on the graphite surface are studied by employing a plasma focus device. The device emits helium ion pulse having energies in the range of a few keV to a few MeV and flux on the order of 10 25 m −2 s −1 at 60 mm axial position from the anode tip. The field emission scanning electron microscopy confirms the formation of multi-modal spherical and elongated agglomerated structures on irradiated samples surface with increase in agglomerate size with increasing number of irradiation shots. The transient annealing in each irradiation was not enough to cause the Oswald ripening or sintering of particles into bigger particle or crystal size but only resulted in clustering. The atomic force micrographs reveal an increase in average surface roughness with increasing ion irradiation. The Raman study demonstrates increase in disordered D peak along with reduced crystallite size (L a) with increasing number of irradiation shots.
Energetic and high fluence helium ions emitted in a plasma focus device have been used successful... more Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed.
An experiment on the formation of virtual electrode and ion sheath characteristics has been carri... more An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from-1000 to-5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper. Published under license by AIP Publishing. https://doi.
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Papers by Neelanjan Buzarbaruah
study the radiation induced damage on tungsten. The reference and irradiated samples were characterized
by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness
testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of
cracks of micrometer width. However at higher magnification, various types of crystalline defects such
as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in
X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating
accumulation of compressive stress due to the heat load delivered by helium ions. A marginal
reduction in hardness of the irradiated sample is also noticed.
study the radiation induced damage on tungsten. The reference and irradiated samples were characterized
by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness
testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of
cracks of micrometer width. However at higher magnification, various types of crystalline defects such
as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in
X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating
accumulation of compressive stress due to the heat load delivered by helium ions. A marginal
reduction in hardness of the irradiated sample is also noticed.