Hyyong Suk - Academia.edu (original) (raw)

Papers by Hyyong Suk

OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics ... more OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics Laboratory (PBPL) in UCLA for researches of laserplasma interactions. OSIRIS was reengineered and documented in UML by our group and ported to Linux cluster machine of 8 nodes. We report our current status of developing the extended version of OSIRIS, which was named as OSIRIS-X and maintained and developed with the Unified Process. Some guidelines in designing and refactoring large-scale scientific codes are presented and discussed. A design model of numerically intensive programs for large-scale computing is suggested, and it is discussed how we can use it for rapid development and prototyping of scientific programs. We also discuss future challenges and prospects in OSIRIS-X development.

Shaping of a petawatt laser pulses using relativistic transparency in a nonuniform overdense plas... more Shaping of a petawatt laser pulses using relativistic transparency in a nonuniform overdense plasma has been studied. The resultant pulse shape is the Concave and sharp-cut pulse front. As an application of such shaping, we consider the generation of a relativistic electron mirror, which is concave to the propagation direction, so that it can be used in generating and focusing X-ray by reflecting a counterpropagating laser pulses. For this study, for the first time, we derived an analytic formula to calculate the channeling speed of a linearly polarized pulse in an overdense plasma. Using that formula it was possible to design an optimal plasma density profile in transverse direction to make the pulse front not only sharp-cut, but also concave to the propagation direction. By accelerating a nano-film with such a concave sharp-cut pulse, we expect a concave relativistic electron mirror can be generated. The concavity of the electron mirror can be used in focusing X-rays into a very s...

We investigated by theory and simulations how fast a relativistically transparent channel is open... more We investigated by theory and simulations how fast a relativistically transparent channel is opened by a linearly polarized relativistic laser pulse in an overdense plasma, which is classically opaque. The relativistic transparency has been well known: the dispersion relations were revealed for various steady states. However, as long as we understand, the answer to the question `how the relativistic channel is formed dynamically from an opaque plasma' has not been so clear. In this work, we focused on finding analytically the speed of such a channel opening. By employing the `channel-opening-time' concept, we could derive semi-analytically a simple formula, which showed excellent agreement with the one-dimensional PIC simulations. The theory was successfully applied in predicting the pulse shape after the interaction of an ultraintense linear polarized laser pulse and a thin foil both in one- and two-dimensional systems.

ABSTRACT A versatile shaping of a laser pulse using relativistic transparency in an overdense pla... more ABSTRACT A versatile shaping of a laser pulse using relativistic transparency in an overdense plasma has been studied. First we present the propagation of a linearly polarized pulse through an overdense plasma and a semi-phenomenological 1-dimensional formula to calculate the channel-digging speed. Second the pulse shaping both in longitudinal and transverse directions using a non-uniform plasma slab is presented by 2-dimensional particle-in-cell simulations. The second subject is a unique point of this work in the context of relativistic transparency and pulse shaping. Furthermore the 2-dimensional results are shown to be in a good agreement with the 1-dimensional formula of the channel-digging. The shaping scheme using non-uniform plasmas gives more freedom to the control of the shape of ultraintense pulses for various purposes.

2007 IEEE Pulsed Power Plasma Science Conference, 2007

Summary form only given. The novel scheme of using Raman backscatter in plasmas for ultraintense,... more Summary form only given. The novel scheme of using Raman backscatter in plasmas for ultraintense, ultrashort pulse generation was proposed and has been intensively studied. Recently a fast envelope-based kinetic simulation code, the averaged-PIC (aPIC) was developed to simulate systematically the Raman backscatter in plasmas. In the last upgrade of the aPIC, two dimensional axis symmetric coordinate system is employed. Therefore, it is possible to simulate semi-three-dimensional, azimuthal symmetric laser propagation, which cannot be done by full PIC codes. From a series of aPIC simulations, several parameters for terawatt laser pulse generation are suggested. For various plasma and laser conditions, the kinetic properties of the amplified pulse are also discussed based on the envelope-kinetic model of the plasma wave.

CLEO: 2013, 2013

ABSTRACT We observe enhanced supercontinuum (SC) radiation emitted from noncollinear bi-filaments... more ABSTRACT We observe enhanced supercontinuum (SC) radiation emitted from noncollinear bi-filaments produced by two crossed femtosecond laser pulses in air. The spectrum is much broader than single-filament-produced SC under the same net input energy.

Quantum Electronics, 2012

We consider acceleration of ions through the interaction of a laser pulse with a sharp leading ed... more We consider acceleration of ions through the interaction of a laser pulse with a sharp leading edge with nanofilms. At sufficiently large amplitude of the pulse, all the electrons can be expelled from the film, which provides an effective regime of ion acceleration. Limiting the maximum energy of ions can result from the longitudinal reverse motion of electrons to the

Physics of Plasmas, 2007

The electron kinetic effects on Raman backscattering and Raman backward laser amplification were ... more The electron kinetic effects on Raman backscattering and Raman backward laser amplification were analyzed. The analysis is based on the envelope-kinetic equations of a plasma wave, which are composed of the conventional envelope equation of a fluid plasma and the kinetic term. One major goal of this paper is to close the envelope-kinetic model by analyzing the kinetic term, which was not fully covered in the previous work [M. S. Hur et al., Phys. Rev. Lett. 95, 115003 (2005)]. It was found that the closed envelope-kinetic equation in the nontrapping regime takes the same form as the envelope equation of the fluid plasma used in the three-wave model. For the closure in the trapping-dominant regime, the test particle technique is employed to calculate the kinetic term. Results from the full kinetic and test particle simulations agree well with each other, while the latter has a great advantage in computation speed. The frequency shift and resonance breaking by the trapped particles ar...

Physics of Plasmas, 2011

Based on two-dimensional particle-in-cell simulations, we investigated the electron beam’s transv... more Based on two-dimensional particle-in-cell simulations, we investigated the electron beam’s transverse oscillations by temporally asymmetric laser pulses in laser wakefield acceleration. Of particular interest in this article are the effects of ultrashort laser pulses having sharp rising and slow falling time scales. In this situation, the accelerated electron beam interacts directly with the laser field and undergoes transverse oscillations due to a phase-slip with the laser field. This oscillation can be matched with the betatron oscillation due to the focusing force of the ions, which can lead to a large transverse oscillation amplitude due to the resonance between them. Furthermore, in this case, the electron beam can be microbunched at the laser wavelength, which may provide the possibility for generation of a coherent synchrotron radiation.

Physics of Plasmas, 2012

A scheme for the laser-induced acceleration of an electron from a double-ionizing neutral gas is ... more A scheme for the laser-induced acceleration of an electron from a double-ionizing neutral gas is investigated, where an inhomogeneous neutral gas profile (resembling a gas-jet experiment) is considered in order to observe the actual electron energy gain during acceleration. Optical-field ionization of the neutral gas can defocus the laser pulse significantly, and an electron accelerates by being pushed in front of a laser pulse in vacuum, and then decelerates due to the defocused (quite low-intensity) tail part of the laser pulse. The reduction in electron deceleration incurred by defocusing the laser-induced double-ionization of the neutral gas makes the electron acceleration continuous. In this study, we introduced an inhomogeneous gas profile that resembles a laser gas-jet experiment. However, the inhomogeneity of the gas reduced the rate of tunnel ionization, which limited the defocusing of the laser pulse; thus, though the electron energy gain is reduced but this proposal is mo...

Physics Letters A, 2011

Acceleration of ions during interaction of a nonadiabatic laser pulse (i.e., a pulse with a sharp... more Acceleration of ions during interaction of a nonadiabatic laser pulse (i.e., a pulse with a sharp front) with a nanofilm is considered. If the amplitude of such a pulse is large enough, all electrons are removed from the target at the beginning of interaction and an energy of the most energetic ions follows approximately a parabolic law with time. Two main physical mechanisms limiting the maximal ions energy are identified and investigated in detail with the help of two-dimensional (2D) particle-in-cell (PIC) simulations. The first effect is a compensation of the ions charge due to the longitudinal return of the electrons to their initial position. The second effect is the compensation of the ions charge in the laser spot due to the transverse motion of the electrons from the periphery of the target. The theory for both effects is developed and a good agreement with the 2D PIC results is established. This theory allows predicting the optimal parameters for ions acceleration.

Physics Letters A, 2008

An externally applied longitudinal magnetic field was found to enhance the particle trapping in t... more An externally applied longitudinal magnetic field was found to enhance the particle trapping in the laser wakefield acceleration. When a static magnetic field of a few tens of tesla is applied in parallel with the propagation direction of a driving laser pulse, it is shown from two-dimensional particle-in-cell simulations that total charge of the trapped beam and its maximum energy

Physics Letters A, 2006

The formation of coherent structures, induced by a super-intense plane electromagnetic wave with ... more The formation of coherent structures, induced by a super-intense plane electromagnetic wave with a sharp rising edge in an ensemble of electrons (electron beam) in vacuum, is considered. The theory describing this process is elaborated. It is shown that the laser pulse can strongly compress the electron beam and also generate fast density modulations (microbunching) in it. Depending on the duration of a laser pulse front, two harmonics can be present simultaneously in longitudinal density modulations of the electron beam-one with laser wavelength and the other with half of the laser wavelength. By changing the form of the laser pulse envelope, one can control the average density of the electron beam (slow density modulation). By varying the laser pulse amplitude and initial length of the electron beam, it is possible to change the number of microbunches in the compressed electron beam, and for certain conditions only one electron bunch can be produced with ultrashort length smaller than the laser wavelength (attosecond length electron beam). The results of the theory are compared with 1D PIC (particle-in-cell) simulations and a good agreement is found.

Physical Review E, 2012

Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymme... more Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymmetric longitudinal profile using a thin plasma layer are investigated via particle-in-cell simulations and the analytical flying mirror model. It is shown that the transmitted pulses having a duration as short as about 4 fs (1.2 laser cycles) or one-cycle front (tail) asymmetric pulses with peak intensity of about 10 21 W/cm 2 can be produced by optimizing system parameters. Here, a new effect is found for the shaping of linearly polarized laser pulses, owing to which the peak amplitude of the transmitted pulse becomes larger than that of the incoming pulse, and intense harmonics are generated. Characteristics of the transmitting window are then studied for different parameters of laser pulse and plasma layer. For a circular polarization, it is shown that the flying mirror model developed for shaping laser pulses with ultrathin foils can be successfully applied to plasma layers having a thickness of about the laser wavelength, which allows the shape of the transmitted pulse to be analytically predicted.

Physical Review E, 2009

For controllable generation of an isolated attosecond relativistic electron bunch ͓relativistic e... more For controllable generation of an isolated attosecond relativistic electron bunch ͓relativistic electron mirror ͑REM͔͒ with nearly solid-state density, we proposed ͓V. V. Kulagin et al., Phys. Rev. Lett. 99, 124801 ͑2007͔͒ to use a solid nanofilm illuminated normally by an ultraintense femtosecond laser pulse having a sharp rising edge ͑nonadiabatic laser pulse͒. In this paper, the REM characteristics are investigated in a regular way for a wide range of parameters. With the help of two-dimensional ͑2D͒ particle-in-cell ͑PIC͒ simulations, it is shown that, in spite of Coulomb forces, all of the electrons in the laser spot can be synchronously accelerated to ultrarelativistic velocities by the first half-cycle of the field, which has large enough amplitude. For the process of the REM generation, we also verify a self-consistent one-dimensional theory, which we developed earlier ͑cited above͒ and which takes into account Coulomb forces, radiation of the electrons, and laser amplitude depletion. This theory shows a good agreement with the results of the 2D PIC simulations. Finally, the scaling of the REM dynamical parameters with the field amplitude and the nanofilm thickness is analyzed.

OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics ... more OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics Laboratory (PBPL) in UCLA for researches of laser- plasma interactions. OSIRIS was reengineered and documented in UML by our group and ported to Linux cluster machine of 8 nodes. We report our current status of developing the extended version of OSIRIS, which was named as OSIRIS-X and maintained and developed with the Unified Process. Some guidelines in designing and refactoring large-scale scientific codes are presented and discussed. A design model of numerically intensive programs for large-scale computing is suggested, and it is discussed how we can use it for rapid development and prototyping of scientific programs. We also discuss future challenges and prospects in OSIRIS-X development.

Journal of the Korean Physical Society, 2007

Attosecond (10−15 s) electron beams will have some important applications in physics, chemistry, ... more Attosecond (10−15 s) electron beams will have some important applications in physics, chemistry, material science, etc., where ultrafast phenomena play an important role. Hence, how to generate such ultrashort electron beams is an important issue. Here, we propose to use a thin plasma layer illuminated normally by an ultra-intense femtosecond laser pulse having a sharp rising edge (rising time ∼ laser oscillation period). In this process, the plasma layer is compressed nonadabatically by the laser pulse, and all electrons are synchronously accelerated to ultra-relativistic velocities by several half-cycles of the laser field. In an experiment, a solid nanofilm, a taped electron beam, or a thin gas jet can be used as possible targets. For these types of targets, we show the generation of an attosecond high-energy electron beam by using particle-in-cell (PIC) simulations.

Journal of the Korean Physical Society, 2007

A new envelope-kinetic method for the simulation of Raman backscattering and laser amplification ... more A new envelope-kinetic method for the simulation of Raman backscattering and laser amplification is presented. In the new scheme, the plasma wave envelope is obtained from the envelope-kinetic equation. For the self-consistent calculation of the kinetic term, a set of test particles is employed, and their motion is traced. The benchmark results of the new scheme against the averaged particlein-cell (aPIC) show quite reasonable agreement while the computation speed increases by a factor of more than 10, depending on the parameters.

Journal of Computational Physics, 2007

A new test particle method is presented for self-consistent incorporation of the kinetic effects ... more A new test particle method is presented for self-consistent incorporation of the kinetic effects into the fluid three-wave model. One of the most important kinetic effects is the electron trapping and it has been found that the trapping affects significantly the behavior of Raman backscatter and Raman backward laser amplification. The conventional fluid three-wave model cannot reproduce the kinetic simulations in the trapping regime. The test particle scheme utilizes the same equations for the laser evolution as in the three-wave model. However, the plasma wave is treated by the envelope-kinetic equation, which consists of envelope evolution and the kinetic term. The core of the new scheme is employing test particles to compute the kinetic term self-consistently. The benchmarking results against the averaged particle-in-cell (aPIC) code show excellent agreements, and the computation speed gain over the aPIC is from 2 to 20 depending on parameters.

Journal of Applied Physics, 1994

The predictions of the smooth-approximation theory for the effective radius of a space-charge dom... more The predictions of the smooth-approximation theory for the effective radius of a space-charge dominated beam in a periodic solenoid focusing channel were checked experimentally over a wide range of focusing conditions. Electron beams with an energy of 5 keV and currents of 50 to 70 mA were transported through a 5-m-long periodic channel and beam radii were measured by an axially moveable phosphor screen and a charge-coupled device camera. The phase advance of betatron oscillation per period without space-charge, σ0, was varied from σ0=45° to σ0=90°. The tune depression due to space-charge, σ/σ0, was in the range of 0.2–0.3. The theoretical results for average beam radius R̄ over one period and the ratio R̄/Rmax were found to agree with the experimental data to better than 5% when a correction due to spherical aberration was taken into account.

OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics ... more OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics Laboratory (PBPL) in UCLA for researches of laserplasma interactions. OSIRIS was reengineered and documented in UML by our group and ported to Linux cluster machine of 8 nodes. We report our current status of developing the extended version of OSIRIS, which was named as OSIRIS-X and maintained and developed with the Unified Process. Some guidelines in designing and refactoring large-scale scientific codes are presented and discussed. A design model of numerically intensive programs for large-scale computing is suggested, and it is discussed how we can use it for rapid development and prototyping of scientific programs. We also discuss future challenges and prospects in OSIRIS-X development.

Shaping of a petawatt laser pulses using relativistic transparency in a nonuniform overdense plas... more Shaping of a petawatt laser pulses using relativistic transparency in a nonuniform overdense plasma has been studied. The resultant pulse shape is the Concave and sharp-cut pulse front. As an application of such shaping, we consider the generation of a relativistic electron mirror, which is concave to the propagation direction, so that it can be used in generating and focusing X-ray by reflecting a counterpropagating laser pulses. For this study, for the first time, we derived an analytic formula to calculate the channeling speed of a linearly polarized pulse in an overdense plasma. Using that formula it was possible to design an optimal plasma density profile in transverse direction to make the pulse front not only sharp-cut, but also concave to the propagation direction. By accelerating a nano-film with such a concave sharp-cut pulse, we expect a concave relativistic electron mirror can be generated. The concavity of the electron mirror can be used in focusing X-rays into a very s...

We investigated by theory and simulations how fast a relativistically transparent channel is open... more We investigated by theory and simulations how fast a relativistically transparent channel is opened by a linearly polarized relativistic laser pulse in an overdense plasma, which is classically opaque. The relativistic transparency has been well known: the dispersion relations were revealed for various steady states. However, as long as we understand, the answer to the question `how the relativistic channel is formed dynamically from an opaque plasma' has not been so clear. In this work, we focused on finding analytically the speed of such a channel opening. By employing the `channel-opening-time' concept, we could derive semi-analytically a simple formula, which showed excellent agreement with the one-dimensional PIC simulations. The theory was successfully applied in predicting the pulse shape after the interaction of an ultraintense linear polarized laser pulse and a thin foil both in one- and two-dimensional systems.

ABSTRACT A versatile shaping of a laser pulse using relativistic transparency in an overdense pla... more ABSTRACT A versatile shaping of a laser pulse using relativistic transparency in an overdense plasma has been studied. First we present the propagation of a linearly polarized pulse through an overdense plasma and a semi-phenomenological 1-dimensional formula to calculate the channel-digging speed. Second the pulse shaping both in longitudinal and transverse directions using a non-uniform plasma slab is presented by 2-dimensional particle-in-cell simulations. The second subject is a unique point of this work in the context of relativistic transparency and pulse shaping. Furthermore the 2-dimensional results are shown to be in a good agreement with the 1-dimensional formula of the channel-digging. The shaping scheme using non-uniform plasmas gives more freedom to the control of the shape of ultraintense pulses for various purposes.

2007 IEEE Pulsed Power Plasma Science Conference, 2007

Summary form only given. The novel scheme of using Raman backscatter in plasmas for ultraintense,... more Summary form only given. The novel scheme of using Raman backscatter in plasmas for ultraintense, ultrashort pulse generation was proposed and has been intensively studied. Recently a fast envelope-based kinetic simulation code, the averaged-PIC (aPIC) was developed to simulate systematically the Raman backscatter in plasmas. In the last upgrade of the aPIC, two dimensional axis symmetric coordinate system is employed. Therefore, it is possible to simulate semi-three-dimensional, azimuthal symmetric laser propagation, which cannot be done by full PIC codes. From a series of aPIC simulations, several parameters for terawatt laser pulse generation are suggested. For various plasma and laser conditions, the kinetic properties of the amplified pulse are also discussed based on the envelope-kinetic model of the plasma wave.

CLEO: 2013, 2013

ABSTRACT We observe enhanced supercontinuum (SC) radiation emitted from noncollinear bi-filaments... more ABSTRACT We observe enhanced supercontinuum (SC) radiation emitted from noncollinear bi-filaments produced by two crossed femtosecond laser pulses in air. The spectrum is much broader than single-filament-produced SC under the same net input energy.

Quantum Electronics, 2012

We consider acceleration of ions through the interaction of a laser pulse with a sharp leading ed... more We consider acceleration of ions through the interaction of a laser pulse with a sharp leading edge with nanofilms. At sufficiently large amplitude of the pulse, all the electrons can be expelled from the film, which provides an effective regime of ion acceleration. Limiting the maximum energy of ions can result from the longitudinal reverse motion of electrons to the

Physics of Plasmas, 2007

The electron kinetic effects on Raman backscattering and Raman backward laser amplification were ... more The electron kinetic effects on Raman backscattering and Raman backward laser amplification were analyzed. The analysis is based on the envelope-kinetic equations of a plasma wave, which are composed of the conventional envelope equation of a fluid plasma and the kinetic term. One major goal of this paper is to close the envelope-kinetic model by analyzing the kinetic term, which was not fully covered in the previous work [M. S. Hur et al., Phys. Rev. Lett. 95, 115003 (2005)]. It was found that the closed envelope-kinetic equation in the nontrapping regime takes the same form as the envelope equation of the fluid plasma used in the three-wave model. For the closure in the trapping-dominant regime, the test particle technique is employed to calculate the kinetic term. Results from the full kinetic and test particle simulations agree well with each other, while the latter has a great advantage in computation speed. The frequency shift and resonance breaking by the trapped particles ar...

Physics of Plasmas, 2011

Based on two-dimensional particle-in-cell simulations, we investigated the electron beam’s transv... more Based on two-dimensional particle-in-cell simulations, we investigated the electron beam’s transverse oscillations by temporally asymmetric laser pulses in laser wakefield acceleration. Of particular interest in this article are the effects of ultrashort laser pulses having sharp rising and slow falling time scales. In this situation, the accelerated electron beam interacts directly with the laser field and undergoes transverse oscillations due to a phase-slip with the laser field. This oscillation can be matched with the betatron oscillation due to the focusing force of the ions, which can lead to a large transverse oscillation amplitude due to the resonance between them. Furthermore, in this case, the electron beam can be microbunched at the laser wavelength, which may provide the possibility for generation of a coherent synchrotron radiation.

Physics of Plasmas, 2012

A scheme for the laser-induced acceleration of an electron from a double-ionizing neutral gas is ... more A scheme for the laser-induced acceleration of an electron from a double-ionizing neutral gas is investigated, where an inhomogeneous neutral gas profile (resembling a gas-jet experiment) is considered in order to observe the actual electron energy gain during acceleration. Optical-field ionization of the neutral gas can defocus the laser pulse significantly, and an electron accelerates by being pushed in front of a laser pulse in vacuum, and then decelerates due to the defocused (quite low-intensity) tail part of the laser pulse. The reduction in electron deceleration incurred by defocusing the laser-induced double-ionization of the neutral gas makes the electron acceleration continuous. In this study, we introduced an inhomogeneous gas profile that resembles a laser gas-jet experiment. However, the inhomogeneity of the gas reduced the rate of tunnel ionization, which limited the defocusing of the laser pulse; thus, though the electron energy gain is reduced but this proposal is mo...

Physics Letters A, 2011

Acceleration of ions during interaction of a nonadiabatic laser pulse (i.e., a pulse with a sharp... more Acceleration of ions during interaction of a nonadiabatic laser pulse (i.e., a pulse with a sharp front) with a nanofilm is considered. If the amplitude of such a pulse is large enough, all electrons are removed from the target at the beginning of interaction and an energy of the most energetic ions follows approximately a parabolic law with time. Two main physical mechanisms limiting the maximal ions energy are identified and investigated in detail with the help of two-dimensional (2D) particle-in-cell (PIC) simulations. The first effect is a compensation of the ions charge due to the longitudinal return of the electrons to their initial position. The second effect is the compensation of the ions charge in the laser spot due to the transverse motion of the electrons from the periphery of the target. The theory for both effects is developed and a good agreement with the 2D PIC results is established. This theory allows predicting the optimal parameters for ions acceleration.

Physics Letters A, 2008

An externally applied longitudinal magnetic field was found to enhance the particle trapping in t... more An externally applied longitudinal magnetic field was found to enhance the particle trapping in the laser wakefield acceleration. When a static magnetic field of a few tens of tesla is applied in parallel with the propagation direction of a driving laser pulse, it is shown from two-dimensional particle-in-cell simulations that total charge of the trapped beam and its maximum energy

Physics Letters A, 2006

The formation of coherent structures, induced by a super-intense plane electromagnetic wave with ... more The formation of coherent structures, induced by a super-intense plane electromagnetic wave with a sharp rising edge in an ensemble of electrons (electron beam) in vacuum, is considered. The theory describing this process is elaborated. It is shown that the laser pulse can strongly compress the electron beam and also generate fast density modulations (microbunching) in it. Depending on the duration of a laser pulse front, two harmonics can be present simultaneously in longitudinal density modulations of the electron beam-one with laser wavelength and the other with half of the laser wavelength. By changing the form of the laser pulse envelope, one can control the average density of the electron beam (slow density modulation). By varying the laser pulse amplitude and initial length of the electron beam, it is possible to change the number of microbunches in the compressed electron beam, and for certain conditions only one electron bunch can be produced with ultrashort length smaller than the laser wavelength (attosecond length electron beam). The results of the theory are compared with 1D PIC (particle-in-cell) simulations and a good agreement is found.

Physical Review E, 2012

Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymme... more Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymmetric longitudinal profile using a thin plasma layer are investigated via particle-in-cell simulations and the analytical flying mirror model. It is shown that the transmitted pulses having a duration as short as about 4 fs (1.2 laser cycles) or one-cycle front (tail) asymmetric pulses with peak intensity of about 10 21 W/cm 2 can be produced by optimizing system parameters. Here, a new effect is found for the shaping of linearly polarized laser pulses, owing to which the peak amplitude of the transmitted pulse becomes larger than that of the incoming pulse, and intense harmonics are generated. Characteristics of the transmitting window are then studied for different parameters of laser pulse and plasma layer. For a circular polarization, it is shown that the flying mirror model developed for shaping laser pulses with ultrathin foils can be successfully applied to plasma layers having a thickness of about the laser wavelength, which allows the shape of the transmitted pulse to be analytically predicted.

Physical Review E, 2009

For controllable generation of an isolated attosecond relativistic electron bunch ͓relativistic e... more For controllable generation of an isolated attosecond relativistic electron bunch ͓relativistic electron mirror ͑REM͔͒ with nearly solid-state density, we proposed ͓V. V. Kulagin et al., Phys. Rev. Lett. 99, 124801 ͑2007͔͒ to use a solid nanofilm illuminated normally by an ultraintense femtosecond laser pulse having a sharp rising edge ͑nonadiabatic laser pulse͒. In this paper, the REM characteristics are investigated in a regular way for a wide range of parameters. With the help of two-dimensional ͑2D͒ particle-in-cell ͑PIC͒ simulations, it is shown that, in spite of Coulomb forces, all of the electrons in the laser spot can be synchronously accelerated to ultrarelativistic velocities by the first half-cycle of the field, which has large enough amplitude. For the process of the REM generation, we also verify a self-consistent one-dimensional theory, which we developed earlier ͑cited above͒ and which takes into account Coulomb forces, radiation of the electrons, and laser amplitude depletion. This theory shows a good agreement with the results of the 2D PIC simulations. Finally, the scaling of the REM dynamical parameters with the field amplitude and the nanofilm thickness is analyzed.

OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics ... more OSIRIS is a large-scale particle-in-cell (PIC) code which was developed at Particle Beam Physics Laboratory (PBPL) in UCLA for researches of laser- plasma interactions. OSIRIS was reengineered and documented in UML by our group and ported to Linux cluster machine of 8 nodes. We report our current status of developing the extended version of OSIRIS, which was named as OSIRIS-X and maintained and developed with the Unified Process. Some guidelines in designing and refactoring large-scale scientific codes are presented and discussed. A design model of numerically intensive programs for large-scale computing is suggested, and it is discussed how we can use it for rapid development and prototyping of scientific programs. We also discuss future challenges and prospects in OSIRIS-X development.

Journal of the Korean Physical Society, 2007

Attosecond (10−15 s) electron beams will have some important applications in physics, chemistry, ... more Attosecond (10−15 s) electron beams will have some important applications in physics, chemistry, material science, etc., where ultrafast phenomena play an important role. Hence, how to generate such ultrashort electron beams is an important issue. Here, we propose to use a thin plasma layer illuminated normally by an ultra-intense femtosecond laser pulse having a sharp rising edge (rising time ∼ laser oscillation period). In this process, the plasma layer is compressed nonadabatically by the laser pulse, and all electrons are synchronously accelerated to ultra-relativistic velocities by several half-cycles of the laser field. In an experiment, a solid nanofilm, a taped electron beam, or a thin gas jet can be used as possible targets. For these types of targets, we show the generation of an attosecond high-energy electron beam by using particle-in-cell (PIC) simulations.

Journal of the Korean Physical Society, 2007

A new envelope-kinetic method for the simulation of Raman backscattering and laser amplification ... more A new envelope-kinetic method for the simulation of Raman backscattering and laser amplification is presented. In the new scheme, the plasma wave envelope is obtained from the envelope-kinetic equation. For the self-consistent calculation of the kinetic term, a set of test particles is employed, and their motion is traced. The benchmark results of the new scheme against the averaged particlein-cell (aPIC) show quite reasonable agreement while the computation speed increases by a factor of more than 10, depending on the parameters.

Journal of Computational Physics, 2007

A new test particle method is presented for self-consistent incorporation of the kinetic effects ... more A new test particle method is presented for self-consistent incorporation of the kinetic effects into the fluid three-wave model. One of the most important kinetic effects is the electron trapping and it has been found that the trapping affects significantly the behavior of Raman backscatter and Raman backward laser amplification. The conventional fluid three-wave model cannot reproduce the kinetic simulations in the trapping regime. The test particle scheme utilizes the same equations for the laser evolution as in the three-wave model. However, the plasma wave is treated by the envelope-kinetic equation, which consists of envelope evolution and the kinetic term. The core of the new scheme is employing test particles to compute the kinetic term self-consistently. The benchmarking results against the averaged particle-in-cell (aPIC) code show excellent agreements, and the computation speed gain over the aPIC is from 2 to 20 depending on parameters.

Journal of Applied Physics, 1994

The predictions of the smooth-approximation theory for the effective radius of a space-charge dom... more The predictions of the smooth-approximation theory for the effective radius of a space-charge dominated beam in a periodic solenoid focusing channel were checked experimentally over a wide range of focusing conditions. Electron beams with an energy of 5 keV and currents of 50 to 70 mA were transported through a 5-m-long periodic channel and beam radii were measured by an axially moveable phosphor screen and a charge-coupled device camera. The phase advance of betatron oscillation per period without space-charge, σ0, was varied from σ0=45° to σ0=90°. The tune depression due to space-charge, σ/σ0, was in the range of 0.2–0.3. The theoretical results for average beam radius R̄ over one period and the ratio R̄/Rmax were found to agree with the experimental data to better than 5% when a correction due to spherical aberration was taken into account.