Control of fast electron propagation in foam target by high-Z doping

Xu, Han; Yang, X. H.; Liu, J; Borghesi, M.

doi:10.1088/1361-6587/aaefce

Cited by 12 publications

(9 citation statements)

References 53 publications

(90 reference statements)

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“…13. In this small ELMs regime, it is clearly seen that the C W is well controlled at 10 −5 level (C W always exceeds 10 −4 in type-I ELMy H-mode [52] ) and can be further reduced from ∼ 5.0 × 10 −5 to ∼ 2.5 × 10 −5 with the decrease of ν eff . As ν eff is proportional to T e (0) −2 • Z eff , the ν eff is more sensitive to T e (0) than to Z eff , which can be checked in Figs.…”

Section: Impurity Confinement In Lhw and Ecrh Heated Small Elmy H-mod...mentioning

confidence: 87%

Reduction of impurity confinement time by combined heating of LHW and ECRH in EAST*

Xu¹,

Wu²,

Zhang³

et al. 2021

Chinese Phys. B

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The core impurity confinement properties are experimentally investigated in the Experimental Advanced Superconducting Tokamak (EAST) plasma heated by lower hybrid wave (LHW) and electron cyclotron resonance heating (ECRH) (LHW+ECRH). It is shown that the impurity confinement time (τ imp) in the L-mode plasma jointly heated by LHW and ECRH is weakly dependent on electron density but strongly dependent on the heating power, thus it is shorter than that in LHW-only heated L-mode plasma with the similar plasma parameters. The combined heating of LHW and ECRH can reduce the collisionality and indicates a more effective heating method for core τ imp reduction and normalized poloidal beta (β P) improvement. It should be emphasized that in this high β P operation window the small ELM regime can be accessed, and an L-mode level τ imp (40 ms–80 ms) and high β N (∼ 1.7) can be obtained simultaneously. It means that this typical small ELMy H-mode regime has an advantage in avoiding the serious tungsten accumulation, and will be competitive in future long-pulse steady-state and high-performance operation with high-Z material plasma-facing components.

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Section: Impurity Confinement In Lhw and Ecrh Heated Small Elmy H-mod...mentioning

confidence: 87%

Reduction of impurity confinement time by combined heating of LHW and ECRH in EAST*

Xu¹,

Wu²,

Zhang³

et al. 2021

Chinese Phys. B

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“…Therefore, the collisional coupling and state-dependent coefficients are no longer needed as used in fluid descriptions, as such coupling coefficients are usually obtained with approximations of the Fokker-Planck collision operator. Note however in a fluid model, such coupling coefficients are not even uniquely defined [8][9][10][11] , with various researchers employing different approximations.…”

Section: Algorithm Of the Modelmentioning

confidence: 99%

Head-on collision of large-scale high density plasmas jets: a first-principle kinetic simulation approach

Wu¹,

Zhang²

2023

Preprint

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In the double-cone ignition (DCI) inertial confinement fusion scheme, head-on collision of high density plasma jets is one of the most distinguished feature when compared with the traditional central ignition and fast ignition of inertial confinement fusion. However, the application of traditional hydrodynamic simulation methods become limited, due to serious plasma penetrations, mixing and kinetic physics that might occur in the collision process. To overcome such limitations, we propose a new simulation method for large-scale high density plasmas. This method takes advantages of modern particle-in-cell simulation techniques and binary Monte Carlo collisions, including both long-range collective electromagnetic fields and short-range particle-particle interactions. Especially, in this method, the restrictions of simulation grid size and time step, which usually appear in a fully kinetic description, are eliminated. In addition, collisional coupling and state-dependent coefficients, that are usually approximately used with different forms in fluid descriptions, are also removed in this method. Energy and momentum exchanges among particles and species, such as thermal conductions and frictions, are modelled by "first principle" kinetic approaches. The correctness and robustness of the new simulation method are verified, by comparing with fully kinetic simulations at small scales and purely hydrodynamic simulations at large scale. Following the conceptual design of the DCI scheme, the colliding process of two plasma jets with initial density of 100 g/cc, initial thermal temperature of 70 eV, and counterpropagating velocity at 300 km/s is investigated using this new simulation method. Quantitative values, including density increment, increased plasma temperature, confinement time at stagnation and conversion efficiency from the colliding kinetic energy to thermal energy, are obtained with a density increment of about three times, plasma temperature of 400 eV, confinement time at stagnation of 50 ps and conversion efficiency of 85%. These values agree with the recent experimental measurements at a reasonable range.

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“…In order to validate the two-pulse scheme further, some 3D hybrid PIC/fluid simulations are carried out by using the code HEETS [28], which treats the fast electrons as a fully dynamical method including collisions (i.e., explicit PIC), while the background electron-ion plasmas are described by a reduced two-fluid model. The simulation box is 200 × 200 × 200 µm 3 with grid of ∆x = ∆y = ∆z = 1 µm.…”

Section: D Hybrid Simulationsmentioning

confidence: 99%

“…On the other hand, the resistive magnetic fields are self-generated in the solid target, which are azimuthal and hence produce some collimating effect on the electron beam [24,25]. With this, the propagation characteristic of fast electrons can be modulated by using some specially designed targets, such as targets consisted of alternating layers of different Z materials [26,27] and low-Z targets doped with high-Z elements [28]. It is also reported that the resistivity at low temperature (e.g., several eV), which also relies on the material microstructure, has a significant effect on the resistive magnetic field and thus the propagation of the fast electrons [29,30].…”

Section: Introductionmentioning

confidence: 99%

Collimation of high-current fast electrons in dense plasmas with a tightly focused precursor intense laser pulse

Yang

Sheng

et al. 2019

Nucl. Fusion

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High current fast electrons at the megaampere level provide a unique way to generate high energy density states of matter, which are related to many applications. However, the large divergence angle of the fast electrons typically over 50 degrees is a significant disadvantage for applications. The guiding effect by the self-generated azimuthal magnetic fields of the fast electron current is found to be very limited due to their cone-shaped spatial structure. In this work, we present a new understanding on the collimation conditions of fast electrons under such a magnetic field structure. It is shown that the transverse peak position of the magnetic field layer plays a crucial role to collimate the fast electrons rather than its magnitude. Based upon this, a new two-pulse collimating scheme is proposed, where a guiding precursor pulse is adopted to form proper azimuthal magnetic fields and a main pulse is for fast electron generation as usual. The present scheme can be implemented relatively easily with the precursor lasers at the 10 TW level with a duration of two hundred femtoseconds, with which the divergence angle of fast electrons driven by the main pulse can be confined within a few degrees. Our scheme can find practical applications in high energy density science.

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Control of fast electron propagation in foam target by high-Z doping

Cited by 12 publications

References 53 publications

Reduction of impurity confinement time by combined heating of LHW and ECRH in EAST*

Reduction of impurity confinement time by combined heating of LHW and ECRH in EAST*

Head-on collision of large-scale high density plasmas jets: a first-principle kinetic simulation approach

Collimation of high-current fast electrons in dense plasmas with a tightly focused precursor intense laser pulse

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