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Heavy ion beam (HIB) inertial confinement fusion (ICF), or HIF would be a promising future energy source for society. 1 Particle accelerators produce HIBs with precise particle energies and pulse shapes with high energy efficiency of ~30-40%. Higher energy driver efficiency means that a lower fusion energy output is required to construct a HIF power station to supply ~1GW of electricity. The DT (Deuterium-Tritium) fusion fuel, with a total mass of several mg, must be compressed to about one thousand times solid density to reduce the input driver energy and to achieve an adequate burn fraction. The high density compression is a major challenge in ICF, requiring that non-uniformity in driver energy deposition be kept lower than a few percent. 2 The phase-controlled non-uniformity is realized in the HIF fuel target implosion by the wobbling HIBs, and the implosion non-uniformity is successfully mitigated in HIF. 1 , 3 The HIB axis can be oscillated sufficiently rapidly to improve the uniformity of energy deposition.

Dynamic mitigation for the tearing mode instability in the current sheet in collisionless plasma is demonstrated by applying a wobbling electron current beam. The initial small amplitude modulations imposed on the current sheet induce the electric current filamentation and the reconnection of the magnetic field lines. When the wobbling or oscillation motion is added from the electron beam having a form of a thin layer moving along the current sheet, the perturbation phase is mixed and consequently the instability growth is saturated remarkably, like in the case of the feed-forward control.

Dynamic mitigation for the tearing mode instability in the current sheet in collisionless plasmas is demonstrated by applying a wobbling electron current beam. The initial small amplitude modulations imposed on the current sheet induce the electric current filamentation and the reconnection of the magnetic field lines. When the wobbling or oscillatory motion is added from the electron beam having a form of a thin layer moving along the current sheet, the perturbation phase is mixed and consequently the instability growth is saturated remarkably, like in the case of the feed-forward control.

Infrared spectroscopy, ultra-fast x-ray high harmonic generation, and time-resolved imaging of molecular structures benefit from the availability of intense mid-infrared wavelength pulses. Here we present a new approach to generating these, in which an intense short laser pulse is incident upon a near-critical density, spherical, mass-limited carbon target. After the laser pulse interaction, the carbon ions produced form a central force field. Plasma electrons accelerated by the laser return to the positively charged carbon target under the action of this field. The energy of these electrons is reduced and is lower than their energy in the laser field. These low-energy refluxing electrons start to oscillate with a rotating figure-of-eight motion around the positively charged carbon target and emit relativistically intense mid-infrared pulses with the wavelength in the range 1 to 4 μm.

Unusual position exchange among ions constituting a swift cluster was found in a high-energy-density plasma. In this paper, the peculiar ion behavior appears in a Si cluster, moving with a speed of ~0.2c (c: speed of light) in a solid Al plasma in the context of the cluster-ion beam driven inertial confinement fusion (ICF). The ion position exchange behavior of cluster ions may influence the cluster-ion beam ICF (CIF) target structure design. In this paper we discuss a possibility of cluster-ion beams as the energy driver in CIF. In conclusions, the present work suggests that the following two points in CIF: (1) The unusual ion position exchange of the cluster ions would not induce a remarkable change in the ion stopping range in CIF targets, and (2) the swift cluster ions may not provide a significant vicinage effect on the stopping range.

Sunlight-like lasers that have a continuous broad frequency spectrum, random phase spectrum, and random polarization are formulated theoretically. With a sunlight-like laser beam consisting of a sequence of temporal speckles, the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles. The wave coupling can be further weakened by the random polarization of such beams. Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of ∼1% as compared with a monochromatic laser beam. Consequently, the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers. Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.

A dynamic mitigation is presented for sausage and kink instability growths of a z-current driven magnetized plasma column. We have proposed a dynamic mitigation method based on a phase control to smooth plasma non-uniformities and to mitigate the instability growth in perturbed plasma systems. In this paper we found that a wobbling motion of the z-current electron axis induces a phase-controlled perturbation, so that the growths of the sausage and kink instabilities are successfully mitigated. In general, plasma instabilities emerge from perturbations, and the perturbation phase is normally unknown. However, if the perturbation phase is known or actively imposed by, for example, a designed driver wobbling behavior, the instability growth would be controlled and mitigated by a superimposition of the perturbations imposed. The results in this paper demonstrate that the wobbling z-current electron beam would provide an improvement in the plasma column stability and uniformity., Comment: 11 pages, and 7 figures

We have proposed a dynamic smoothing method based on a phase control to smooth plasma non-uniformities in perturbed plasma systems. In this paper, the dynamic smoothing method is applied to a spherical direct-driven fuel target implosion in heavy ion inertial confinement fusion. We found that the wobbling motion of each heavy ion beam (HIB) axis induces a phase-controlled HIBs energy deposition, and consequently the phase-controlled implosion acceleration is realized, so that the HIBs irradiation non-uniformity is successfully smoothed. HIB accelerators provide a well-established performance to oscillate a HIB axis at a high frequency. In inertial confinement fusion, a fuel implosion uniformity is essentially significant for achieving the DT fuel compression and for releasing the fusion energy, and the non-uniformity of the implosion acceleration should be less than a few %. The results in this paper demonstrate that the wobbling HIBs would provide an improvement in the fuel target implosion uniformity.

In this paper, the robustness of the dynamic instability mitigation mechanism is first examined, and then the instability mitigation phenomenon is demonstrated in a deuterium–tritium (DT) fuel target implosion by wobbling heavy-ion beams (HIBs). 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. In general instability would emerge from the perturbation of the physical quantity. Normally the perturbation phase is unknown, so that the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superposition of perturbations imposed actively: if the perturbation is induced by, for example, a driving beam axis oscillation or wobbling, the perturbation phase could be controlled and the instability growth is mitigated by the superposition of the growing perturbations. In this paper, we realize the superposition of the perturbation by the wobbling HIBs’ illumination onto a DT fuel target in heavy-ion inertial fusion (HIF). Our numerical fluid implosion simulations present that the implosion non-uniformity is mitigated successfully by the wobbling HIBs illumination in HIF.