The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19 , 024503 (2012)], based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–Taylor instability (RTI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3 , 1 (1977)] another mechanism was proposed to stabilize RTI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al. , Phys. Rev. Lett. 71 , 3131 (1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.
In this review paper on heavy ion inertial fusion (HIF), the state-of-the-art scientific results are presented and discussed on the HIF physics, including physics of the heavy ion beam (HIB) transport in a fusion reactor, the HIBs-ion illumination on a direct-drive fuel target, the fuel target physics, the uniformity of the HIF target implosion, the smoothing mechanisms of the target implosion non-uniformity and the robust target implosion. The HIB has remarkable preferable features to release the fusion energy in inertial fusion: in particle accelerators HIBs are generated with a high driver efficiency of ∼30%–40%, and the HIB ions deposit their energy inside of materials. Therefore, a requirement for the fusion target energy gain is relatively low, that would be ∼50–70 to operate a HIF fusion reactor with the standard energy output of 1 GW of electricity. The HIF reactor operation frequency would be ∼10–15 Hz or so. Several-MJ HIBs illuminate a fusion fuel target, and the fuel target is imploded to about a thousand times of the solid density. Then the DT fuel is ignited and burned. The HIB ion deposition range is defined by the HIB ions stopping length, which would be ∼1 mm or so depending on the material. Therefore, a relatively large density-scale length appears in the fuel target material. One of the critical issues in inertial fusion would be a spherically uniform target compression, which would be degraded by a non-uniform implosion. The implosion non-uniformity would be introduced by the Rayleigh-Taylor (R-T) instability, and the large density-gradient-scale length helps to reduce the R-T growth rate. On the other hand, the large scale length of the HIB ions stopping range suggests that the temperature at the energy deposition layer in a HIF target does not reach a very-high temperature: normally about 300 eV or so is realized in the energy absorption region, and that a direct-drive target would be appropriate in HIF. In addition, the HIB accelerators are operated repetitively and stably. The precise control of the HIB axis manipulation is also realized in the HIF accelerator, and the HIB wobbling motion may give another tool to smooth the HIB illumination non-uniformity. The key issues in HIF physics are also discussed and presented in the paper.
Abstract In this paper, a study on a fusion reactor core is presented in heavy-ion inertial fusion (HIF), including the heavy-ion beam (HIB) transport in a fusion reactor, an HIB interaction with a background gas, the reactor cavity gas dynamics, the reactor gas backflow to the beam lines, and an HIB fusion reactor design. The HIB has remarkable preferable features to release the fusion energy in inertial fusion: in particle accelerators HIBs are generated with a high driver efficiency of about 30–40%, and the HIB ions deposit their energy inside of materials. Therefore, a requirement for the fusion target energy gain is relatively low, that would be ~50 to operate an HIF fusion reactor with a standard energy output of 1 GW of electricity. In a fusion reactor, the HIB charge neutralization is needed for a ballistic HIB transport. Multiple mechanical shutters would be installed at each HIB port at the reactor wall to stop the blast waves and the chamber gas backflow, so that the accelerator final elements would be protected from the reactor gas contaminant. The essential fusion reactor components are discussed in this paper.
To investigate the chiral magnetic effect, 96Zr and 96Ru beams were accelerated at the relativistic heavy ion collider (RHIC) during Run-18 at Brookhaven National Laboratory. The 96Zr beam was provided from the electron beam ion source (EBIS) injector, which consists of a laser ion source, an EBIS high charge state ion breeder, a 300 keV/u radio frequency quadrupole, and a 2 MeV/u interdigital H type drift tube linear accelerator (IH-DTL). The natural abundance of 96Zr is only 2.8% with about 50% of 90Zr. To obtain a sufficient beam current, Zr material enriched to about 60% of 96Zr was used. The only available form of the enriched material was zirconium oxide (ZrO2) powder, which was not well suited for a laser ion source target. We studied and established a sintering technique of the ZrO2 powder to make a solid sample which could be installed into the laser ion source. The singly charged Zr was produced in a laser ablation plasma, extracted, and delivered to the EBIS to be ionized further to 96Zr16+. We optimized the laser irradiation condition, the EBIS confinement time, and transport through the RF linacs to maximize the performance of the injector. The total number of shots provided from the laser ion source for injection into the EBIS was 489 910. The EBIS facility provided a 192 MeV stable beam of 96Zr16+ ions to the booster ring of alternating gradient synchrotron (AGS) for further acceleration and stripping in the AGS/RHIC complex, allowing for successful data acquisition at the Solenoidal Tracker at the RHIC.
A dynamic mitigation mechanism for instability growth was proposed and discussed in the paper [Phys. Plasmas 19, 024503 (2012)]. In the present paper the robustness of the dynamic instability mitigation mechanism is discussed further. The results presented here show that the mechanism of the dynamic instability mitigation is rather robust against changes in the phase, the amplitude and the wavelength of the wobbling perturbation applied.
A fiber-coupled, acoustic-wave-assisted (AW) microchip laser-induced breakdown spectroscopy (mLIBS) system was developed to analyze the elemental composition and surface imaging. In this study, we measured the dependence of sample temperature and laser ablation angle (LAA) on the laser-induced plasma–optical emission (LIP–OE) and LIP–acoustic signal (LIP–AS). The intensity of the LIP–OE and ablated mass at three different temperatures and eight different LAAs were estimated using a zirconium sample. Simultaneously, we investigated the LIP–AS amplitude, propagation speed, and shape by synchronizing the AW-mLIBS system with a high-speed camera. The results revealed that the LIP–OE increases with increasing temperature and is unaffected by LAA up to 40° because the amount of the ablated mass was similar to the plasma. Additionally, no considerable variation in plasma temperature was obtained using the Boltzmann method over the sample temperature. However, the propagation speed of the LIP–AS differs with temperature but has marginal angular dependence because the LIP–AS propagates as semispherical. Furthermore, no considerable changes were observed in the LIP–AS amplitude up to 100°C, and the LAA showed a similar tendency to that of the LIP–OE.
The document describes a numerical algorithm to simulate plasmas and fluids in the 3 dimensional space by the Euler method, in which the spatial meshes are fixed to the space. The plasmas and fluids move through the spacial Euler mesh boundary. The Euler method can represent a large deformation of the plasmas and fluids. On the other hand, when the plasmas or fluids are compressed to a high density, the spatial resolution should be ensured to describe the density change precisely. The present 3D Euler code is developed to simulate a nuclear fusion fuel ignition and burning. Therefore, the 3D Euler code includes the DT fuel reactions, the alpha particle diffusion, the alpha particle deposition to heat the DT fuel and the DT fuel depletion by the DT reactions, as well as the thermal energy diffusion based on the three-temperature compressible fluid model.
