Atomic, Molecular, Optical, and Plasma Physics Division focuses on fundamental interactions of atoms, molecules, optical media, and charged particles to laser lights, x rays, or other novel sources of electric and magnetic fields. These fundamental interactions are important to understand natural phenomena such as solar flares, the birth of stars, and lightning, as well as to advance modern technology such as the development of efficient light bulbs, plasma televisions, lasers, and modern infrastructures for quantum computers. We will have one invited talk from an expert in the field and several contributed talks from young scholars.
Development of ultrafast X-ray sources driven by femtosecond lasers at the Extreme Light Infrastructure (ELI) Beamlines facility
ELI Beamlines, one of the pillars of the European Extreme Light Infrastructure project (ELI), is a high-power laser facility. The facility hosts several state-of-the-art, high-power laser systems ranging from a few Terawatt (PW) peak power to 10 PW (Petawatt) peak power. The main objective of the facility is to provide beams of ultrashort particles and photons sources to the user community from various fields of research. In this contribution I will introduce the ELI beamlines project, summarize the current status of research and implementation of three types of X-ray sources: the HHG Beamline, the plasma X-ray source, the Gammatron beamline based on laser-plasma accelerator (LPA), and a Betatron source dedicated to plasma physics research. X-ray pulse sources driven by high peak power kHz femtosecond lasers such as high-order harmonic sources and plasma X-ray sources have been commissioned and already entered the operation phase. The second LPA-based hard X-ray Betatron X-ray is being developed in the ELI plasma physics platform (P3) located at the experimental hall E3. It aims to serve as a backlighter for advanced laser-matter interaction experiments such as high-energy-density physics, intense laser-matter interaction, and advanced plasma physics experiments combined with multiple laser beams.
Besides, I will present an advanced scheme for the enhancement of hard X-ray photon flux by using the density-tailored plasma to control relativistic electron orbits and nonlinear resonances due to interaction with a two-color laser field. In addition, I will report a new mechanism of relativistic emission of radiation from plasma mirrors (RIME) that is identified with an extraordinary property that instead of following specular reflection, the radiation is emitted in the direction along the plasma mirror surface. The efficiency of this process can be orders of magnitude higher when compared to specular HHG originating from the relativistic oscillating mirror (ROM) for the same laser and plasma parameters.
Please look below for detailed schedule.
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Abstract Number: ANPA2023-N00017 Presenting Author: Num Prasad Acharya Presenter's Affiliation: Ph.D. scholar Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract We have investigated the evolution of dust charge and ion flow at the sheath boundary for the collisional magnetized dusty plasma in the presence of non-Maxwellian electron distribution in account of source and sink terms. The set of governing fluid equations have been solved for given initial conditions, whereas the dust charging equation have been solved using Newton-Raphson method. We have extended the Bohm sheath condition for dusty plasma using Sagdeev potential approach and it is found that gas pressure, obliqueness of magnetic field, ion loss term, and choice of electron distribution affect the evolution of dust charge and flow of positive ions at the sheath boundary.
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Abstract Number: ANPA2023-N00020 Presenting Author: Pradeep Karki Presenter's Affiliation: Tribhuvan University Title: EFFECT OF ELECTRON IMPACT IONIZATION SOURCE TERM ON MAGNETIZED PLASMA SHEATH Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract EFFECT OF ELECTRON IMPACT IONIZATION SOURCE TERM ON
MAGNETIZED PLASMA SHEATH
Pradeep Karki1*, Suresh Basnet1,2, and Raju Khanal2
1Department of Physics, GoldenGate International College, Tribhuvan University, Kathmandu 44600, Nepal
2Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu 44613, Nepal
Email: stonermind12@gmail.com
In this study, a fluid model has been used to explore the magnetized plasma sheath properties in the presence of ion-neutral collision and electron impact ionization source term. To solve the set of fluid equations, the initial conditions at the sheath edge and physical parameters are used. The obtained results reveal that the ionization source term affects the plasma sheath parameters: electric potential, net charge density, electron and ion density, and ion velocity. In terms of magnitude, the potential increases from about 17 to 68 as the magnitude of electron impact ionization frequency increases from 0 to 0.02. The net charge density is minimum at the sheath edge, and it increases towards the wall with its maximum peak value obtained in the sheath region. Once the maximum occurs, the net charge density decreases towards the wall. For the same increment of electron impact ionization frequency, the particle density decreases towards the wall, however, the decreasing rate is much slower for the ions than that of electrons. The electron density almost diminished at the wall while few ion densities reach the wall. Moreover, the velocity of ions increases toward the wall and the magnitude velocity with which it strikes the wall increases from about 5.7 to 11.6.
References:
[1] T. E. Sheridan and J. A. Goree, IEEE Trans. Plasma Sci. 17, 884 (1989).
[2] K. U. Riemann, J. Phys. D: Appl. Phys. 24(4), 493 (1991).
[3] N. Sternberg, V. Godyak, and D. Hoffman, Phys. Plasmas 13, 063511 (2006).
[4] S. Basnet, A. Maskey, A. Deuja, and R. Khanal, Phys. Plasmas 28, 083705 (2021).
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Abstract Number: ANPA2023-N00018 Presenting Author: Rajan Ghimire Presenter's Affiliation: Student Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract This work is concerned with the effect of non-Maxwellian electrons and obliqueness of magnetic field on magnetized plasma sheath characteristics, in which plasma interacts with tungsten (W) and molybdenum (Mo) surfaces via non-neutral plasma sheath using two fluids model. It is assumed that the singly charged positive ions are treated as warm fluid whereas the electrons obey q-nonextensive distribution. It is found that the q-nonextensive distributed electrons and the temperature of ions affect the entrance velocity of positive ions, which is a key parameter in the plasma sheath formation. Also, the nonextensive parameter q affects the distribution of ions and electrons in the sheath region and their distributions explicitly related with the electrostatic potential variation. The parallel and
perpendicular components of ions velocity are affected by the obliqueness of magnetic field. As the nonextensivity of electrons increases, the gradient in electric potential increases towards the wall and hence the impact energy also increases. The obliqueness of magnetic field and impact energy of ions is a key factor that determines the physical sputtering rate, particle reflection and absorption from the target surface. Furthermore, the probability of particle reflection coefficient from the W-surface is higher than that of Mo-surface.
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Abstract Number: ANPA2023-N00019 Presenting Author: Ramesh Khanal and Rajan Ghimire Presenter's Affiliation: Student Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract This work is concerned with the effect of non-Maxwellian electrons and obliqueness of magnetic field on magnetized plasma sheath characteristics, in which plasma interacts with tungsten (W) and molybdenum (Mo) surfaces via non-neutral plasma sheath using two fluids model. It is assumed that the singly charged positive ions are treated as warm fluid whereas the electrons obey q-nonextensive distribution. It is found that the q-nonextensive distributed electrons and the temperature of ions affect the entrance velocity of positive ions, which is a key parameter in the plasma sheath formation. Also, the nonextensive parameter q affects the distribution of ions and electrons in the sheath region and their distributions explicitly related with the electrostatic potential variation. The parallel and
perpendicular components of ions velocity are affected by the obliqueness of magnetic field. As the nonextensivity of electrons increases, the gradient in electric potential increases towards the wall and hence the impact energy also increases. The obliqueness of magnetic field and impact energy of ions is a key factor that determines the physical sputtering rate, particle reflection and absorption from the target surface. Furthermore, the probability of particle reflection coefficient from the W-surface is higher than that of Mo-surface.
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Abstract Number: ANPA2023-N00016 Presenting Author: Roshan Chalise Presenter's Affiliation: Central department of Physics, Tribhuvan University, Kathmandu, Nepal, Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract Atmospheric pressure plasma (APP) finds extensive applications across various fields to enhance human life quality such as food safety (microbial inactivation, bacteria-free food), healthcare (cancer treatment, wound healing, blood coagulation, dental procedures), micro-fabrication (etching, chemical vapor deposition), agriculture (insecticide, sterilization, growth enhancement, fertilizers), and environmental science (air and water pollution treatment). In this study, we have developed and characterized gliding arc, dielectric barrier discharge, and plasma jet systems using natural air in the laboratory of the Central Department of Physics. These plasma systems were then applied in agriculture fields (such as leaf mustard, paddy, cauliflower, coriander seed, and mushroom) both directly and indirectly (by exposing plasma to water and subsequently using the treated water on crops). The APP generates various reactive species, including nitrate, nitrite, hydrogen peroxide, and OH functional groups, which alter the properties of the seeds, seed germination, seedling growth, and water. The treated substrates exhibit decreased contact angles, rendering seeds more hydrophilic, enabling increased water absorption and improved germination rates. Plasma-activated water contains a higher concentration of reactive species, promoting growth enhancement and serving as a fertilizer and pesticide.
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Abstract Number: ANPA2023-N00021 Presenting Author: Suresh Basnet Presenter's Affiliation: Tribhuvan University Location: Central Department of Physics, T.U., Nepal Show/Hide Abstract In laboratory and space plasmas, the emission of electrons from the surface significantly affects the characteristics of plasma sheath formed at that surface, which is crucial to understanding the overall plasma-wall interaction mechanism. In this work, the collisional fluid model is used for laboratory dusty plasma, whereas collisionless model is used for lunar dusty plasma. We have extended the Bohm sheath criterion for the formation of stable plasma sheath in account of electron emission from the surface, loss of ion flux, and gas pressure for the collisional laboratory dusty plasmas. It is found that ion flow at the sheath boundary is considerably influenced by the concentration of electron emission, ion loss term, and gas pressure. The equilibrium evolution of dust charge explicitly determines the magnitude of ion flow at the sheath boundary. The plasma parameters adopted in the present case are reliable in laboratory and space dusty plasmas, especially dusty plasma environment on the lunar surface. The surface of Moon and dust grains are electrically charged due to interaction of solar-wind plasma and photoemission electrons from the surface due to solar ultra-violet radiation. In addition, the plasma sheath characteristics, dust charging process, and stable dust levitation on the sheath region have been studied.
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Abstract Number: ANPA2023-N00025 Presenting Author: Uddhab Chaulagain (Invited) Presenter's Affiliation: Scientist, Laser Plasma Physicist, ELI Beamlines, Prague, Czech Republic Location: Virtual Presentation Show/Hide Abstract ELI Beamlines, one of the pillars of the European Extreme Light Infrastructure project (ELI), is a high-power laser facility. The facility hosts several state-of-the-art, high-power laser systems ranging from a few Terawatt (PW) peak power to 10 PW (Petawatt) peak power. The main objective of the facility is to provide beams of ultrashort particles and photons sources to the user community from various fields of research. In this contribution I will introduce the ELI beamlines project, summarize the current status of research and implementation of three types of X-ray sources: the HHG Beamline, the plasma X-ray source, the Gammatron beamline based on laser-plasma accelerator (LPA), and a Betatron source dedicated to plasma physics research. X-ray pulse sources driven by high peak power kHz femtosecond lasers such as high-order harmonic sources and plasma X-ray sources have been commissioned and already entered the operation phase. The second LPA-based hard X-ray Betatron X-ray is being developed in the ELI plasma physics platform (P3) located at the experimental hall E3. It aims to serve as a backlighter for advanced laser-matter interaction experiments such as high-energy-density physics, intense laser-matter interaction, and advanced plasma physics experiments combined with multiple laser beams. _x000D_
_x000D_
Besides, I will present an advanced scheme for the enhancement of hard X-ray photon flux by using the density-tailored plasma to control relativistic electron orbits and nonlinear resonances due to interaction with a two-color laser field. In addition, I will report a new mechanism of relativistic emission of radiation from plasma mirrors (RIME) that is identified with an extraordinary property that instead of following specular reflection, the radiation is emitted in the direction along the plasma mirror surface. The efficiency of this process can be orders of magnitude higher when compared to specular HHG originating from the relativistic oscillating mirror (ROM) for the same laser and plasma parameters.
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Abstract Number: ANPA2023-N00024 Presenting Author: Tikaram Neupane Presenter's Affiliation: Department of Chemistry and Physics, The University of North Carolina at Pembroke, Pembroke, NC 28372 Title: Polarity of Nonlinear Refraction coefficient in Graphene-Oxide Monolayer through SSPM Location: Virtual Presentation Show/Hide Abstract The study on the polarity and magnitude of nonlinear refraction (NLR) coefficient of the graphene-oxide (GO) atomic layer is of great interest for optoelectronic applications. It is studied through the laser-induced spatial self-phase modulation (SSPM) of an optical field which reveals the nonlinear refraction coefficients of GO atomic layers in an aqueous base solution with a resonant excitation using a chopped quasi-static laser at 532 nm. It displayed several concentric diffraction rings at the far field due to the laser-induced intensity-dependent refractive index in the materials (GO). The formation of concentric diffraction rings is due to the coherent superposition of transverse wave vectors. The number of concentric rings as a function of the applied intensity revealed the nonlinear refraction coefficient of GO which was estimated to be ~-6.65×10^-12 m^2/W for the laser-excitation duration of ~0.32 sec., where the negative polarity of nonlinear refraction coefficient was confirmed with the interference image profile of SSPM. The upper and vertical distortion of concentric rings at the far-field at the longer laser-excitation duration of ~0.8 sec. indicates the distortion of the coherent superposition of transverse wave vectors due to the localized thermal vortex of GO in the aqueous solution that offers novel platforms of thermal metrology based on the localized optical nonlinearity and temperature-sensitive all-optical switching.
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Abstract Number: ANPA2023-N00023 Presenting Author: Bhanu Ghimire Presenter's Affiliation: University of North Carolina at Charlotte Title: Design and Fabrication of Dipole Coupled Microbolometer as Infrared Sensor Location: Florida International University, FL, USA Show/Hide Abstract Dipole coupled microbolometer uses planar lithographic antennas to couple infrared radiation into the feed line. In this research, irradiance values at the dipole arm have been studies for direct incidence and using reflector behind substrate. Bolometer has been fabricated by sputtering process to measure electrical property and detectivity of infrared antenna. A new method to calculate the radiation efficiency based on the spatial and angular response of infrared antennas is presented and used to evaluate their performance. We have observed Fresnel losses in the system of around 12% due to reflection, absorption and transmission and concentration ratio ranges from 60 to 85 at the feed point. A dipole radiation pattern was studied for fixed length of 7.5 micrometer for operating wavelength 28.3 THz. The observed radiation pattern shows main lobe and side bands indicating capability of antenna for multiple communication.
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Abstract Number: ANPA2023-N00022 Presenting Author: Dipendra Khatri Presenter's Affiliation: University of Central Florida Location: Florida International University, FL, USA Show/Hide Abstract Spatiotemporal characterization of few-cycle Bessel-Gaussian and vector waveforms in the mid-infrared
Dipendra Khatri1, Yangyang Liu1, Shima Gholam-Mirzaei2, Tran-Chau Truong1,
Andre Staudte2, Paul B Corkum2 and Michael Chini1,3
1Department of Physics, University of Central Florida, Orlando FL 32816
2Joint Attosecond Science Laboratory (JASLab), National Research Council of Canada and
University of Ottawa, Ottawa, Ontario K1A 0R6, Canada
3CREOL, the College of Optics and Photonics, University of Central Florida, Orlando FL 32816
Author e-mail address: dskhatri@knights.ucf.edu
Abstract: Knowledge of the space-time properties of ultrafast laser pulses is necessary both for characterizing spatiotemporal distortions and for applications using structured beams. In the past, such space-time characterization has been achieved using either measurements of linear interference between an ‘unknown’ pulse and a well-characterized ‘reference’ pulse in the near-infrared and visible or using electro-optic sampling (EOS) in the THz spectral region. Very recently, EOS-based imaging techniques have been extended to the near-infrared, but this requires the synchronization of the unknown pulse with a few-femtosecond sampling pulse to achieve the necessary time resolution. Here, we demonstrate that a novel variant of TIPTOE (tunnel ionization with a perturbation for the time-domain observation of electric fields) capable of resolving three-dimensional (2D space + time) laser waveforms. By using multiphoton nonlinear excitation in a silicon-based CMOS image sensor as a sub-cycle “temporal gateâ€, we do the measurement of the full space, time, and polarization state of structured (Vector, and Bessel-Gaussian beams) few-cycle mid-infrared laser waveforms. The reversal of the electric field direction in adjacent Bessel rings, and radially polarized polarization-state of the vector beam is directly observed in the field-resolved measurement. The experiment is carried out using few-cycle mid-IR pulses centered near 3.4 μm, which are generated by nonlinear compression of multi-cycle pulses from an optical parametric amplifier (OPA).
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