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Fukuda, Yuji; Matsui, Ryutaro*; Iwata, Natsuyo*; Kishimoto, Yasuaki
no journal, ,
In order to investigate the underlying physical mechanism of high power laser interaction with cluster medium, we have performed simulations using EPIC3D (Extended Particle based Integrated Code), which includes key atomic processes and relaxation processes self-consistently in fully relativistic three dimensional configuration, and systematically investigated the interaction processes of medium of carbon clusters embedded in helium gas. We found that the synergetic interplay of different mechanisms such as (1) acceleration of ions due to Coulomb explosion of individual carbon clusters, (2) compression and acceleration of background helium gas due to the Coulomb explosion of clusters, (3) magnetic vortex generation and associated pinching near the rare surface, and (4) sheath acceleration at the interface between the medium and vacuum, could play an important role in realizing the particle acceleration observed in the experiments.
Fukuda, Yuji; Matsui, Ryutaro*; Iwata, Natsuyo*; Kishimoto, Yasuaki
no journal, ,
The recent advancements of novel laser-driven ion acceleration techniques now allow and even exceed the maximum energy of ions up to several tens of MeV. For example, substantial enhancement of the accelerated ion energies has been demonstrated by utilizing a unique property of a cluster-gas target. In order to investigate the underlying physical mechanism of high power laser interaction with cluster medium, we have performed simulations using EPIC3D (Extended Particle based Integrated Code). We found that the synergetic interplay of different mechanisms could play an important role in realizing the particle acceleration observed in the experiments. More interestingly, in laser intensities of a relativistic ion regime, a new mechanism of ion acceleration can be incorporated with the Coulomb explosion.
Kanasaki, Masato; Jinno, Satoshi; Sakaki, Hironao; Nishiuchi, Mamiko; Faenov, A. Ya.*; Pikuz, T.; Kondo, Kiminori; Oda, Keiji*; Yamauchi, Tomoya*; Matsui, Ryutaro*; et al.
no journal, ,
In laser-driven ion acceleration using cluster-gas targets, generated ions can be assigned to two components. One is a low energy component produced by Coulomb explosions of clusters. The other is a high energy component produced by a magnetic vortex acceleration mechanism. In the past studies, high energy ions were mainly measured by stacked CR-39 detectors to obtain the energy spectrum. In the present study, to reveal the acceleration mechanism, a spatial distribution of MeV ions was measured by CR-39 detectors which were encircled equidistant from the laser focus spot. The etch pit distribution on the CR-39 suggests that the acceleration mechanism cannot be explained only by Coulomb explosion mechanism, but by other complicated mechanisms.
Kanasaki, Masato*; Jinno, Satoshi; Sakaki, Hironao; Nishiuchi, Mamiko; Kondo, Kiminori; Oda, Keiji*; Yamauchi, Tomoya*; Matsui, Ryutaro*; Kishimoto, Yasuaki; Doria, D.*; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas targets, in addition to the isotropic low energy component (
several MeV/n) due to Coulomb explosion of clusters, the directional high energy component (
several MeV/n) due to the magnetic vortex acceleration have been observed. In this study, we discuss an ion acceleration mechanism based on the recent measurement of the spatial and energy distributions of the lower energy component.
Fukuda, Yuji; Matsui, Ryutaro; Iwata, Natsuyo*; Kishimoto, Yasuaki
no journal, ,
In order to investigate the underlying physical mechanism of high power laser interaction with cluster medium, we have performed simulations using EPIC3D (Extended Particle based Integrated Code), which includes key atomic processes and relaxation processes self-consistently in fully relativistic three dimensional configuration, and systematically investigated the interaction processes of medium of carbon clusters embedded in helium gas. We found that the synergetic interplay of different mechanisms such as (1) acceleration of ions due to Coulomb explosion of individual carbon clusters, (2) compression and acceleration of background helium gas due to the Coulomb explosion of clusters, (3) magnetic vortex generation and associated pinching near the rare surface, and (4) sheath acceleration at the interface between the medium and vacuum, could play an important role in realizing the particle acceleration observed in the experiments.
Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Faenov, A. Ya.*; Pikuz, T. A.*; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; Matsui, Ryutaro; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas target, the acceleration mechanism consists of different processes such as, (a) acceleration of ions due to Coulomb explosion of individual clusters, (b) compression and acceleration of background gas ions due to the Coulomb explosion of clusters, (c) magnetic vortex generation and associated pinching near the rear surface, and (d) sheath acceleration at the interface between the medium and vacuum. To reveal the synergetic interplay between the processes (a) and (b), we have conducted ion acceleration experiments using CO
clusters embedded in background H gas with the J-KAREN laser. By a careful analysis of CR-39, we have found that the maximum energies of protons and carbon ions are 1.5 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters can be discussed with the help from numerical simulations.
Fukuda, Yuji; Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Nishiuchi, Mamiko; Faenov, A.*; Pikuz, T.*; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; et al.
no journal, ,
In this study, to understand the synergetic interplay between the Coulomb explosion of clusters and the background gas dynamics, we have conducted ion acceleration experiments using CO
clusters embedded in background H gas with the J-KAREN laser at JAEA-KPSI. As a result, energy spectra for protons (from background gas) and carbon/oxygen ions (from clusters) are obtained separately for the first time. We found that the maximum energies of protons and carbon/oxygen ions are 
1.5 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters is discussed with the help from numerical simulations which employ a particle-in-cell (PIC) method including relaxation and ionization processes of plasma particles (EPIC3D).
Fukuda, Yuji; Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Nishiuchi, Mamiko; Faenov, A.*; Pikuz, T.*; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas target, the acceleration mechanism consists of different processes such as, (a) acceleration of ions due to Coulomb explosion of individual clusters, (b) compression and acceleration of background gas ions due to the Coulomb explosion of clusters, (c) magnetic vortex generation and associated pinching near the rear surface, and (d) sheath acceleration at the interface between the medium and vacuum. To understand the synergetic interplay between the Coulomb explosion of clusters and the background gas dynamics, we have conducted ion acceleration experiments using CO clusters embedded in background H gas with the J-KAREN laser at JAEA-KPSI. By a careful analysis of CR-39, energy spectra for protons (from background gas) and carbon/oxygen ions (from clusters) are obtained separately for the first time. We found that the maximum energies of protons and carbon/oxygen ions are 1.5 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters is discussed with the help from numerical simulations which employ a particle-in-cell (PIC) method including relaxation and ionization processes of plasma particles (EPIC3D).
Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Faenov, A.*; Pikuz, T. A.*; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; Matsui, Ryutaro; et al.
no journal, ,
In the previous laser-driven ion acceleration experiment using cluster-gas target, we have only focused on the high energy ions with energies of multi-tens of MeV. In order to reveal synergetic interplay between the Coulomb explosion of clusters and the background gas ions, we have measured protons (background gas ions) separately from carbon and oxygen ions (clusters) by using magnetic spectrometer with CR-39 track detectors. We have found that the number of carbon and oxygen ions decrease sharply at 1 MeV/n. On the other hand, the protons show the Maxwell-Boltzmann energy distribution. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters can be discussed with the help from numerical simulations.
Jinno, Satoshi*; Tanaka, Hirotaka*; Kanasaki, Masato; Sakaki, Hironao; Kondo, Kiminori; Matsui, Ryutaro; Kishimoto, Yasuaki; Fukuda, Yuji
no journal, ,
Laser-driven ion acceleration, featured by its huge accelerating electric field gradient and short pulse length, has been one of the most active areas of research during the last several years, because ion beams generated from such compact sources can be employed in a broad range of applications. Here, the state of material is a key ingredient, which determines the characteristics of the interaction. We present the development of a new nozzle equipped with a liquid He cooling head, which has a potential to produce submicron-sized H clusters. Such H clusters could produce "pure" proton beams with energies of 100 MeV by using the upgraded J-KAREN-P laser.
Matsui, Ryutaro; Fukuda, Yuji; Kanasaki, Masato; Sakaki, Hironao; Iwata, Natsuyo*; Kondo, Kiminori; Kishimoto, Yasuaki*
no journal, ,
In the experiment conducted at JAEA-KPSI, we have observed an acceleration of background gas ions as a result of the interaction between a high peak power laser pulses and clustered media, where a few hundreds nanometer sized CO clusters are embedded in a background H gas. In order to understand the acceleration mechanism of the background gas ions, we have carried out numerical simulations using the 2D PIC codes in the parameter regime relevant to the experiment. The simulation results shows that background gas ions are compressed and accelerated due to the Coulomb explosion of clusters. In addition, some ions are accelerated in the laser propagation direction due to the anisotropic electric field created by the relativistic effect.
Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Faenov, A.*; Pikuz, T. A.*; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; Matsui, Ryutaro; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas targets, consisting of a few hundreds nanometer sized clusters and the background gas, the energy spectrum of accelerated ions has two components. The lower energy component is produced by the Coulomb explosions of clusters and the higher one is accelerated by electric fields created by the magnetic vortex. In this study, in order to reveal the acceleration mechanism of the background gas ions, we have measured the ion energy spectra for the background gas and for clusters separately. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters is discussed with the help from numerical simulations.
Fukuda, Yuji; Jinno, Satoshi*; Kanasaki, Masato; Tanaka, Hirotaka; Sakaki, Hironao; Kondo, Kiminori; Matsui, Ryutaro; Kishimoto, Yasuaki
no journal, ,
We have developed a new cluster target system which consists of a pulsed solenoid valve equipped with a conical nozzle and a liquid helium cooling head, having a potential to produce submicron-size hydrogen clusters. We have tried to generate submicron-size hydrogen clusters using this system. The size distribution measurement, conducted by using the Mie scattering method, demonstrates that hydrogen clusters with diameters of 400-2000 nm are produced at a nozzle temperature of 25 K and a gas pressure of 6 Mpa. The 2D PIC code simulation shows that protons can be accelerated up to several tens of MeV via the Coulomb explosion of a single submicron-size hydrogen cluster at a laser intensity of 1
10
W/cm
. Interestingly, the Coulomb explosion is anisotropic because electrons are significantly pushed forward due to the vB term of the Lorentz force.
Matsui, Ryutaro; Fukuda, Yuji; Kawahito, Daiki*; Kishimoto, Yasuaki*
no journal, ,
In interactions between a high peak power laser pulses and clustered media, where CO clusters are embedded in a background H gas, as the resent experiment at JAEA-KPSI shows, the Coulomb explosion of clusters contributes to the acceleration of background gas ions. In order to understand the dynamics of the cluster expansion in the ambient gas, we have carried out numerical simulations using the 2D PIC codes in the parameter regime relevant to the experiment. The simulation results show that the charge separation and the electric field formation near the contact surface of a cluster and background gas play an important role in the structure formation of a cluster expansion.
Fukuda, Yuji; Kanasaki, Masato*; Jinno, Satoshi*; Sakaki, Hironao; Nishiuchi, Mamiko; Pirozhkov, A. S.; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; Pikuz, T. A.*; et al.
no journal, ,
In order to understand the synergetic interplay between the Coulomb explosion of clusters and the background gas dynamics, an energy spectrum of carbon/oxygen ions from the CO clusters and that of protons from the background hydrogen gas are measured separately at 110
W/cm with a careful analysis of etch pit structures on CR-39. The maximum energies of carbon/oxygen ions and protons are determined as 1.1 MeV/n and 1.6 MeV, respectively. Moreover, we present a development of submicron-size hydrogen cluster targets using a cryogenic conical nozzle and their characterization with the Mie scattering method. Above 10
W/cm, the anisotropic Coulomb explosion of submicron-size hydrogen clusters could produce directional proton beams with energies of several tens of MeV, quite advantageous to the future applications, since they are inherently impurity-free, high rep.rate, and robust.
Tanaka, Hirotaka; Jinno, Satoshi*; Kanasaki, Masato*; Sakaki, Hironao; Kondo, Kiminori; Matsui, Ryutaro; Kishimoto, Yasuaki; Fukuda, Yuji
no journal, ,
We present a development of submicron-size hydrogen cluster targets using a cryogenic conical nozzle and their characterization with the Mie scattering method. Above 10 W/cm, achievable soon with the coming PW laser facilities, the anisotropic Coulomb explosion of submicron-size hydrogen clusters could produce directional proton beams with energies of several tens of MeV, quite advantageous to the future applications, since they are inherently impurity-free, high rep. rate, and robust.
cluster targetsMatsui, Ryutaro; Fukuda, Yuji; Kawahito, Daiki*; Kishimoto, Yasuaki*
no journal, ,
In order to examine energy distributions of ions, we performed a 3D PIC simulation concerning an interaction between the high power laser and H cluster targets with a radius of 600 nm, at a laser intensity of 1.010 W/cm
. The simulation results shows that in addition to symmetric electric fields by the Coulomb repulsive force, asymmetric sheath electric fields are generated due to electrons pushed forward by the Lorenz force, JB. As a result, ions are accelerated forward up to 100 MeV by the anisotropic electric field of Coulomb explosion which consists of the symmetric electric fields and the asymmetric sheath fields. These results suggest that by using J-KAREN-P laser and submicron-size H cluster targets, protons with energies of 100 MeV can be produced.
cluster mediaMatsui, Ryutaro; Fukuda, Yuji; Kawahito, Daiki*; Kishimoto, Yasuaki*
no journal, ,
In order to examine energy distributions of ions, by using the particle based integrated code, EPIC3D, we performed a 3D numerical simulation concerning an interaction between the high power laser and cluster media, where submicron-size H cluster is embedded in a background H gas at a laser intensity of 1.010 W/cm. The simulation results shows that in addition to symmetric electric fields by the Coulomb repulsive force, asymmetric sheath electric fields are generated due to electrons pushed forward by the Lorenz force, JB. As a result, ions are accelerated forward up to approximately 100 MeV by the anisotropic electric field of Coulomb explosion which is the superposition of the symmetric electric field and the asymmetric sheath field.
Matsui, Ryutaro; Fukuda, Yuji; Kawahito, Daiki*; Kishimoto, Yasuaki*
no journal, ,
In the recent experiment concerning high power laser-cluster interaction, composed of CO clusters and background hydrogen gas, conducted at JAEA-KPSI, high energy background hydrogen ions, accelerated up to 1.6 MeV, have been observed. In order to examine the acceleration mechanism of the background gas ions, we have performed 2D and 3D PIC simulations in the parameter regime relevant to the experiment. The simulation results shows that at the contact surface area, the asymmetric electric field of Coulomb explosion from cluster and the additional electric field from background gas are generated and these electric fields contribute to the acceleration of background gas ions. From energy spectra of ions, the simulation results well support experimental ones.
Matsui, Ryutaro; Fukuda, Yuji; Kawahito, Daiki*; Kishimoto, Yasuaki*
no journal, ,
In the experiment concerning ion acceleration, composed of CO clusters and background hydrogen gas, conducted at JAEA-KPSI, high energy background hydrogen ions, accelerated up to 1.6 MeV, have been observed. In order to examine the structure dynamics of fields which trigger to the acceleration of background gas ions, we have carried out a series of 2D and 3D numerical simulations using the particle based integrated code, EPIC3D, in the parameter regime relevant to the experiments. The simulation results shows that at the contact surface area, the asymmetric electric field of Coulomb explosion from cluster and the additional electric field from background gas are generated and these electric fields contribute to the acceleration of background gas ions. From energy spectra of ions, the simulation results well support experimental ones.