Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac2731
S. Aich, R. Kumar, T. Macwan, D. Kumavat, S. Jha, R. Tanna, K. Sathyanarayana, J. Ghosh, K. Jadeja, K. Patel, S. Patel, V. Ranjan, Madanlal Kalal, Dinesh Varia, D. Sadharkiya, D. Raju, P. Chattopadhyay, C. Gupta, Y. Saxena
Due to several forces acting on the plasma column in a tokamak, the plasma column tends to move horizontally and/or vertically leading to many adverse events including termination of plasma. Precise measurement of plasma column position throughout the discharge with good temporal resolution in the real time is hence necessary in order to restrict the column movement using the stabilizing equilibrium magnetic fields. The plasma column position is measured by several magnetic diagnostics such as magnetic pick-up probe, Mirnov coil, Sine-Cosine coil along with flux loops in ADITYA Upgrade tokamak (ADITYA-U). In spite of the simplicity of the measurement principle of these probes as well as of their construction, obtaining the position of the plasma column is not very straightforward. The diversity of all these magnetic diagnostics in terms of their structures, installation location, mounting scenario etc leads to improper position estimations as these probes are being affected differently by the unwanted magnetic pick-ups. These unwanted pickups, especially those arising from vessel eddies, are successfully removed by introducing a scaling method for all the above-mentioned position probes in ADITYA-U based on the in situ calibration of these probes. The correction factors are deduced by estimating the known positions of a central current carrying conductor correctly using the probe measurements during the in situ calibration. These correction factors are used for estimating the plasma column position in the tokamak experiment along with proper nullification of magnetic fields arising from other magnets during tokamak operation. The plasma column position estimation from different magnetic probes are compared with each other and also with those estimated from diagnostics other than the magnetic ones.
{"title":"Plasma column position measurements using magnetic diagnostics in ADITYA-U tokamak","authors":"S. Aich, R. Kumar, T. Macwan, D. Kumavat, S. Jha, R. Tanna, K. Sathyanarayana, J. Ghosh, K. Jadeja, K. Patel, S. Patel, V. Ranjan, Madanlal Kalal, Dinesh Varia, D. Sadharkiya, D. Raju, P. Chattopadhyay, C. Gupta, Y. Saxena","doi":"10.1088/2516-1067/ac2731","DOIUrl":"https://doi.org/10.1088/2516-1067/ac2731","url":null,"abstract":"Due to several forces acting on the plasma column in a tokamak, the plasma column tends to move horizontally and/or vertically leading to many adverse events including termination of plasma. Precise measurement of plasma column position throughout the discharge with good temporal resolution in the real time is hence necessary in order to restrict the column movement using the stabilizing equilibrium magnetic fields. The plasma column position is measured by several magnetic diagnostics such as magnetic pick-up probe, Mirnov coil, Sine-Cosine coil along with flux loops in ADITYA Upgrade tokamak (ADITYA-U). In spite of the simplicity of the measurement principle of these probes as well as of their construction, obtaining the position of the plasma column is not very straightforward. The diversity of all these magnetic diagnostics in terms of their structures, installation location, mounting scenario etc leads to improper position estimations as these probes are being affected differently by the unwanted magnetic pick-ups. These unwanted pickups, especially those arising from vessel eddies, are successfully removed by introducing a scaling method for all the above-mentioned position probes in ADITYA-U based on the in situ calibration of these probes. The correction factors are deduced by estimating the known positions of a central current carrying conductor correctly using the probe measurements during the in situ calibration. These correction factors are used for estimating the plasma column position in the tokamak experiment along with proper nullification of magnetic fields arising from other magnets during tokamak operation. The plasma column position estimation from different magnetic probes are compared with each other and also with those estimated from diagnostics other than the magnetic ones.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac077c
T. Abbaszadeh, H. Zahed
Using kinetic theory, the dispersion properties of dust ion-acoustic (DIA) wave propagation in the dusty plasma including electrons, ions, and dust particles are investigated. We obtain the dispersion relation of the DIA wave in the plasma with q-distribution. In the limit q → 1, the results are in agreement with Maxwellian distribution results. The wave frequency decreases as the nonextensive index q increases, particularly for the high magnitude of the q index. The phase velocity of the wave is achieved for short and long wavelengths. The wave frequency enhances by increasing the ion to electron density ratio.
{"title":"Investigation of dust ion-acoustic wave dispersion properties in the dusty plasma with q-distribution","authors":"T. Abbaszadeh, H. Zahed","doi":"10.1088/2516-1067/ac077c","DOIUrl":"https://doi.org/10.1088/2516-1067/ac077c","url":null,"abstract":"Using kinetic theory, the dispersion properties of dust ion-acoustic (DIA) wave propagation in the dusty plasma including electrons, ions, and dust particles are investigated. We obtain the dispersion relation of the DIA wave in the plasma with q-distribution. In the limit q → 1, the results are in agreement with Maxwellian distribution results. The wave frequency decreases as the nonextensive index q increases, particularly for the high magnitude of the q index. The phase velocity of the wave is achieved for short and long wavelengths. The wave frequency enhances by increasing the ion to electron density ratio.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac14ae
H. Itoh, T. Nagai, M. Taguchi, K. Teranishi, Susumu Suzuki
It is well known that a fine powder is deposited on the surface of coaxial cylinder electrodes made from stainless steel and borosilicate glass in ozone generators. We inspected the fine powder and the stainless steel by x-ray diffraction and Auger electron spectroscopy to clarify the relationship between the gradual decrease in ozone concentration, i.e., ozone zero phenomena (OZP) produced in the ozone generator, and the deterioration of stainless steel. The results of x-ray diffraction for both specimens suggest that several oxides with iron, chromium and nickel are formed from the stainless steel exposed to an ozone–oxygen mixture and the discharge. In particular, FeO detected by x-ray diffraction analysis means that the temperature of the surface of stainless steel and the powder reaches at least 843 K owing to the generation of heat by discharge and oxidation of the fine powder and electrode surface despite the inside of electrodes being refrigerated with circulating water. This temperature is much higher than the 453 K estimated in our previous work as a threshold temperature of the thermal decomposition of ozone by model experiments using a simulated ozone generator during the OZP. On the other hand, Auger electron spectroscopy is carried out in combination with the repeated tracing of the OZP, and we investigate whether oxygen atoms penetrate in the depth direction of the stainless steel. During this process, we observed serious OZP, meaning the ozone concentration at the outlet of the ozone generator is almost zero for 40–50 h continuously following the gradual decrease in ozone concentration. The penetration of oxygen atoms into the stainless-steel bulk is considered as the start of the collapse of the original passivation film covering on the surface of stainless steel. After the process, i.e., the cessation of the OZP, the formation of a new thin layer instead of the passivation film is observed with the coexistence of a strong oxidizer, i.e., ozone and atomic oxygen and the heat produced by discharge in the ozone generator. However, the recovered ozone concentration is realized up to half of the peak value in the measurement. This process corresponds to the recovery of the ozone concentration after the OZP. Hence, we concluded that the OZP is advanced by the thermal decomposition of ozone accompanied by the deterioration of the stainless-steel surface by ozone oxidation.
{"title":"Advancement of ozone zero phenomenon by surface deterioration of stainless—steel electrode","authors":"H. Itoh, T. Nagai, M. Taguchi, K. Teranishi, Susumu Suzuki","doi":"10.1088/2516-1067/ac14ae","DOIUrl":"https://doi.org/10.1088/2516-1067/ac14ae","url":null,"abstract":"It is well known that a fine powder is deposited on the surface of coaxial cylinder electrodes made from stainless steel and borosilicate glass in ozone generators. We inspected the fine powder and the stainless steel by x-ray diffraction and Auger electron spectroscopy to clarify the relationship between the gradual decrease in ozone concentration, i.e., ozone zero phenomena (OZP) produced in the ozone generator, and the deterioration of stainless steel. The results of x-ray diffraction for both specimens suggest that several oxides with iron, chromium and nickel are formed from the stainless steel exposed to an ozone–oxygen mixture and the discharge. In particular, FeO detected by x-ray diffraction analysis means that the temperature of the surface of stainless steel and the powder reaches at least 843 K owing to the generation of heat by discharge and oxidation of the fine powder and electrode surface despite the inside of electrodes being refrigerated with circulating water. This temperature is much higher than the 453 K estimated in our previous work as a threshold temperature of the thermal decomposition of ozone by model experiments using a simulated ozone generator during the OZP. On the other hand, Auger electron spectroscopy is carried out in combination with the repeated tracing of the OZP, and we investigate whether oxygen atoms penetrate in the depth direction of the stainless steel. During this process, we observed serious OZP, meaning the ozone concentration at the outlet of the ozone generator is almost zero for 40–50 h continuously following the gradual decrease in ozone concentration. The penetration of oxygen atoms into the stainless-steel bulk is considered as the start of the collapse of the original passivation film covering on the surface of stainless steel. After the process, i.e., the cessation of the OZP, the formation of a new thin layer instead of the passivation film is observed with the coexistence of a strong oxidizer, i.e., ozone and atomic oxygen and the heat produced by discharge in the ozone generator. However, the recovered ozone concentration is realized up to half of the peak value in the measurement. This process corresponds to the recovery of the ozone concentration after the OZP. Hence, we concluded that the OZP is advanced by the thermal decomposition of ozone accompanied by the deterioration of the stainless-steel surface by ozone oxidation.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac1c5d
A. Tewari, Santanu Ghosh, P. Srivastava
The effect of process parameters such as the pressure, power, and substrate bias on the dimensions of CNT, graphene, and graphene-CNT hybrids in the low and high temperature regime is described by a multispecies plasma-assisted and catalyst-aided phenomenological growth model of graphene-carbon nanotube (CNT) hybrids. An interplay established in the present work between the process and plasma parameters (such as the electron density and temperature, and radical flux) characterizes the process parameters effects. It is found that this interplay is remarkably different at low and high temperature owing to the different processes that dominate during the growth in these temperature regimes.
{"title":"Modeling low and high temperature controls in the growth of graphene-CNT hybrids by PECVD: an interplay between process and plasma parameters","authors":"A. Tewari, Santanu Ghosh, P. Srivastava","doi":"10.1088/2516-1067/ac1c5d","DOIUrl":"https://doi.org/10.1088/2516-1067/ac1c5d","url":null,"abstract":"The effect of process parameters such as the pressure, power, and substrate bias on the dimensions of CNT, graphene, and graphene-CNT hybrids in the low and high temperature regime is described by a multispecies plasma-assisted and catalyst-aided phenomenological growth model of graphene-carbon nanotube (CNT) hybrids. An interplay established in the present work between the process and plasma parameters (such as the electron density and temperature, and radical flux) characterizes the process parameters effects. It is found that this interplay is remarkably different at low and high temperature owing to the different processes that dominate during the growth in these temperature regimes.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac2311
C. Rasouli, B. Pourshahab
In the present study, a series of experiments were performed to study collisions of runaway electrons in the Damavand tokamak by imaging hard x-ray radiations, as one of the secondary effects of these electrons, using radiochromic films. For these experiments, GAFCHROMIC™EBT2 dosimetry films were selected due to their high resolution imaging capability. These instruments were installed in two strip and screen structures for one- and two-dimensional imaging in high-dose areas of the Damavand tokamak, and after irradiation on the device, the recorded data were extracted using a flatbed scanner. The results showed that in runaway discharges of the Damavand tokamak, if active plasma position control system is off, predominant collision of the runaway electrons column occurs with outer wall of the vacuum chamber. Also, the recorded images indicated that dimensions of temporary sources of hard x-rays in the Damavand tokamak are about 10 cm × 10 cm. Two-dimensional imaging in these experiments showed that toroidal field coils are exposed to significant hard x-ray radiations, making the use of radiation-sensitive diagnostic systems in this area questionable. The results obtained from measurements also indicated that the highest radiation dose in the Damavand tokamak is in the limiter region and reaches up to 300 mSv shot−1.
{"title":"Imaging of hard x-ray radiations using Gafchromic™ dosimetry film in Damavand tokamak","authors":"C. Rasouli, B. Pourshahab","doi":"10.1088/2516-1067/ac2311","DOIUrl":"https://doi.org/10.1088/2516-1067/ac2311","url":null,"abstract":"In the present study, a series of experiments were performed to study collisions of runaway electrons in the Damavand tokamak by imaging hard x-ray radiations, as one of the secondary effects of these electrons, using radiochromic films. For these experiments, GAFCHROMIC™EBT2 dosimetry films were selected due to their high resolution imaging capability. These instruments were installed in two strip and screen structures for one- and two-dimensional imaging in high-dose areas of the Damavand tokamak, and after irradiation on the device, the recorded data were extracted using a flatbed scanner. The results showed that in runaway discharges of the Damavand tokamak, if active plasma position control system is off, predominant collision of the runaway electrons column occurs with outer wall of the vacuum chamber. Also, the recorded images indicated that dimensions of temporary sources of hard x-rays in the Damavand tokamak are about 10 cm × 10 cm. Two-dimensional imaging in these experiments showed that toroidal field coils are exposed to significant hard x-ray radiations, making the use of radiation-sensitive diagnostic systems in this area questionable. The results obtained from measurements also indicated that the highest radiation dose in the Damavand tokamak is in the limiter region and reaches up to 300 mSv shot−1.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.1088/2516-1067/ac0a43
Satadal Das, S. Karkari
The possibility of achieving uniform and controllable plasma distribution remain a fundamental challenge in low pressure plasma discharges, which has numerous applications in plasma technologies. An external object when introduced in a magnetized plasma can significantly alter the spatial plasma distribution. In this paper, the effect of external plate biasing on both axial as well as radial characteristics of an expanding, partially magnetized plasma column, created by hot cathode filament inside a linear plasma device is presented. It is found that by applying a positive potential to a conducting external electrode, placed at a remote location away from the primary discharge region; the back diffused plasma tends to become uniform. The plate biasing also results in an overall increase in electron temperature of the expanding plasma; however, it does not appear to alter the radial plasma characteristics inside the source and the biasing region. A possible mechanism behind observing this effect has been provided.
{"title":"Radial control of plasma uniformity and electron temperature by external plate biasing in a back diffused partially magnetized plasma","authors":"Satadal Das, S. Karkari","doi":"10.1088/2516-1067/ac0a43","DOIUrl":"https://doi.org/10.1088/2516-1067/ac0a43","url":null,"abstract":"The possibility of achieving uniform and controllable plasma distribution remain a fundamental challenge in low pressure plasma discharges, which has numerous applications in plasma technologies. An external object when introduced in a magnetized plasma can significantly alter the spatial plasma distribution. In this paper, the effect of external plate biasing on both axial as well as radial characteristics of an expanding, partially magnetized plasma column, created by hot cathode filament inside a linear plasma device is presented. It is found that by applying a positive potential to a conducting external electrode, placed at a remote location away from the primary discharge region; the back diffused plasma tends to become uniform. The plate biasing also results in an overall increase in electron temperature of the expanding plasma; however, it does not appear to alter the radial plasma characteristics inside the source and the biasing region. A possible mechanism behind observing this effect has been provided.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61181071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-18DOI: 10.1088/2516-1067/abd294
L. Klintberg, Erika Åkerfeldt, A. Persson
The spectral emissions from a microplasma have been used to predict the CO2 concentration in gas samples covering a concentration range of 0%–100%. Different models based on partial least squares have been evaluated, comparing two different spectral pre-processing filters –multiplicative scatter correction (MSC) and standard normal variate correction (SNV) – and three different wavelength ranges. The models were compared with respect to accuracy, precision, stability and linearity. CO2 samples were mixed with either air or nitrogen. The choice of mixing gas influenced the predicted concentration and basing the models on data from only one mixing gas resulted in higher prediction power. Using air as mixing gas and SNV filtering resulted in a root mean square error of prediction (RMSEP) of 0.03 for an independent test dataset. This RMSEP was of the same range as the experimental error. On the other hand, the models with the best long term stability, reaching the lowest Allan variance, were based on observations with both mixing gases. Models based on MSC filtering generally had slightly higher RMSEP than those based on SNV filtering. Generally, the CO2 concentration could be accurately predicted in the concentration range of 5%–90%. For higher and lower concentrations, the models underestimated the CO2 concentration and were less accurate and precise. Basing the models on fewer wavelengths resulted in reduced linearity. The models were also evaluated by applying them for transcutaneous blood gas monitoring, where they helped to reveal new physiological information.
{"title":"Partial least squares modelling of spectroscopic data from microplasma emissions for determination of CO2 concentration","authors":"L. Klintberg, Erika Åkerfeldt, A. Persson","doi":"10.1088/2516-1067/abd294","DOIUrl":"https://doi.org/10.1088/2516-1067/abd294","url":null,"abstract":"The spectral emissions from a microplasma have been used to predict the CO2 concentration in gas samples covering a concentration range of 0%–100%. Different models based on partial least squares have been evaluated, comparing two different spectral pre-processing filters –multiplicative scatter correction (MSC) and standard normal variate correction (SNV) – and three different wavelength ranges. The models were compared with respect to accuracy, precision, stability and linearity. CO2 samples were mixed with either air or nitrogen. The choice of mixing gas influenced the predicted concentration and basing the models on data from only one mixing gas resulted in higher prediction power. Using air as mixing gas and SNV filtering resulted in a root mean square error of prediction (RMSEP) of 0.03 for an independent test dataset. This RMSEP was of the same range as the experimental error. On the other hand, the models with the best long term stability, reaching the lowest Allan variance, were based on observations with both mixing gases. Models based on MSC filtering generally had slightly higher RMSEP than those based on SNV filtering. Generally, the CO2 concentration could be accurately predicted in the concentration range of 5%–90%. For higher and lower concentrations, the models underestimated the CO2 concentration and were less accurate and precise. Basing the models on fewer wavelengths resulted in reduced linearity. The models were also evaluated by applying them for transcutaneous blood gas monitoring, where they helped to reveal new physiological information.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45502929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.1088/2516-1067/abd3f1
I. Gainullin, V. Dudnikov
This work addresses the negative ionization of hydrogen particles on low work function metal surfaces, which is an important process for the field of the surface plasma negative ion beams sources. We present the theoretical model for the computer calculation of the negative ionization probability which takes into account the component of atom/ion velocity, parallel to the surface. The calculated negative ionization probability of hydrogen quantitatively fits to the experimental data in the wide range of ion exit energies. The theoretical estimation shows, that for the low work function converter surfaces (φ ∼ 1.5 eV) the negative ionization probability of hydrogen can be enhanced up to 30% if the hydrogen has velocity component parallel to the surface ∼0.05 a.u. (∼60 eV). Therefore, the H- ion production rate can be increased for a negative ion source configuration that implements the oblique exit angle of hydrogen.
{"title":"Theoretical investigation of the negative ionization of hydrogen particles on metal surfaces with low work function","authors":"I. Gainullin, V. Dudnikov","doi":"10.1088/2516-1067/abd3f1","DOIUrl":"https://doi.org/10.1088/2516-1067/abd3f1","url":null,"abstract":"This work addresses the negative ionization of hydrogen particles on low work function metal surfaces, which is an important process for the field of the surface plasma negative ion beams sources. We present the theoretical model for the computer calculation of the negative ionization probability which takes into account the component of atom/ion velocity, parallel to the surface. The calculated negative ionization probability of hydrogen quantitatively fits to the experimental data in the wide range of ion exit energies. The theoretical estimation shows, that for the low work function converter surfaces (φ ∼ 1.5 eV) the negative ionization probability of hydrogen can be enhanced up to 30% if the hydrogen has velocity component parallel to the surface ∼0.05 a.u. (∼60 eV). Therefore, the H- ion production rate can be increased for a negative ion source configuration that implements the oblique exit angle of hydrogen.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47845887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-10DOI: 10.1088/2516-1067/abc467
Shu Li, Shuguang Chen, Shi-fang Xiao, Xiang Zhai, Huang-qing Liu, Jingjing Mao, Jianzhong Mao
According to simulation results from FDTD, Fano resonance of the air-Si-Si-air combined waveguide cavity was mainly studied, including the distribution of the magnetic field, quality factor, extinction coefficient and transmission efficiency. Fano resonance was related to the height of Si. When the height H 2 = 140 nm of Si and the height of H 1 = 300 nm, there was higher extinction coefficient in the resonant cavity and the better quality of the resonator, whose transmission efficiency of surface plasma was up to 89% for 1110 nm. This combined cavity had very good filtering effect.
{"title":"Fano resonance of air-Si waveguide cavity","authors":"Shu Li, Shuguang Chen, Shi-fang Xiao, Xiang Zhai, Huang-qing Liu, Jingjing Mao, Jianzhong Mao","doi":"10.1088/2516-1067/abc467","DOIUrl":"https://doi.org/10.1088/2516-1067/abc467","url":null,"abstract":"According to simulation results from FDTD, Fano resonance of the air-Si-Si-air combined waveguide cavity was mainly studied, including the distribution of the magnetic field, quality factor, extinction coefficient and transmission efficiency. Fano resonance was related to the height of Si. When the height H 2 = 140 nm of Si and the height of H 1 = 300 nm, there was higher extinction coefficient in the resonant cavity and the better quality of the resonator, whose transmission efficiency of surface plasma was up to 89% for 1110 nm. This combined cavity had very good filtering effect.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45210866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-30DOI: 10.1088/2516-1067/abc311
S. Divya
The mechanism of generation of terahertz (THz) radiation with beating of two supergausssian lasers in corrugated density plasma containing hot electron-positron (e-p) is revisited. Resonance condition for optical excitation of THz emission is reported to be modified due to finite temperature of plasma species (electrons-positrons to the few order keV range) in the presence of weak collisions. The collision frequency is optimized to the range ν ≤ 0.5ω p in the e-p plasma depending on the temperature and collisional rates. The effect of electron temperature, collision frequency and suitability of supergaussian laser is investigated on phase modulation to achieve highest emitted THz field with 6% efficiency of the mechanism.
{"title":"Impact of hot electrons on optical excitation of terahertz radiation by beating of supergaussian lasers in electron-positron collisional plasma","authors":"S. Divya","doi":"10.1088/2516-1067/abc311","DOIUrl":"https://doi.org/10.1088/2516-1067/abc311","url":null,"abstract":"The mechanism of generation of terahertz (THz) radiation with beating of two supergausssian lasers in corrugated density plasma containing hot electron-positron (e-p) is revisited. Resonance condition for optical excitation of THz emission is reported to be modified due to finite temperature of plasma species (electrons-positrons to the few order keV range) in the presence of weak collisions. The collision frequency is optimized to the range ν ≤ 0.5ω p in the e-p plasma depending on the temperature and collisional rates. The effect of electron temperature, collision frequency and suitability of supergaussian laser is investigated on phase modulation to achieve highest emitted THz field with 6% efficiency of the mechanism.","PeriodicalId":36295,"journal":{"name":"Plasma Research Express","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43208103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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