力三 畠山

Bio: 力三 畠山 is an academic researcher. The author has contributed to research in topics: Ion & Electron cyclotron resonance. The author has an hindex of 1, co-authored 3 publications receiving 9 citations.

Plasma and trap-based techniques for science with positrons

Abstract: In recent years, there has been a wealth of new science involving low-energy antimatter (i.e., positrons and antiprotons) at energies ranging from 10 to less than 10 eV. Much of this progress has been driven by the development of new plasma-based techniques to accumulate, manipulate and deliver antiparticles for specific applications. This article focuses on the advances made in this area using positrons. However many of the resulting techniques are relevant to antiprotons as well. An overview is presented of relevant theory of single-component plasmas in electromagnetic traps. Methods are described to produce intense sources of positrons and to efficiently slow the typically energetic particles thus produced. Techniques are described to trap positrons efficiently and to cool and compress the resulting positron gases and plasmas. Finally, the procedures developed to deliver tailored pulses and beams (e.g., in intense, short bursts, or as quasi-monoenergetic continuous beams) for specific applications are reviewed. The status of development in specific application areas is also reviewed. One example is the formation of antihydrogen atoms for fundamental physics [e.g., tests of invariance under charge conjugation, parity inversion and time reversal (the CPT theorem), and studies of the interaction of gravity with antimatter]. Other applications discussed include atomic and materials physics studies and study of the electron-positron many-body system, including both classical electron-positron plasmas and the complementary quantum system in the form of Bose-condensed gases of positronium atoms. Areas of future promise are also discussed. The review concludes with a brief summary and a list of outstanding challenges. ∗ Contact information: jrdanielson@ucsd.edu † Contact information: ddubin@ucsd.edu ‡ Contact information: rgreaves@fpsi.edu § Contact information: csurko@ucsd.edu

Helicon-type radiofrequency plasma thrusters and magnetic plasma nozzles

Abstract: Development of electrodeless radiofrequency plasma thrusters, e.g., a helicon thruster, has been one the of challenging topics for future high-power and long-lived electric propulsion systems. The concept simply has a radiofrequency plasma production/heating source and a magnetic nozzle, while it seems to include many aspects of physics and engineering issues. The plasma produced inside the source is transported along the magnetic field lines and expands in the magnetic nozzle, where the plasma is spontaneously accelerated into the axial direction along the magnetic nozzle, yielding a generation of the thrust force. Hence, the plasma transport and spontaneous acceleration phenomena in the magnetic nozzle are key issues to improve the performance of the thrusters. Since the thrust is equal in magnitude and opposite in direction to momentum flux exhausted from the system, the direct measurement of the thrust can reveal not only the thruster performance but also fundamental physical quantity of plasma momentum flux. Here studies on fundamental physics relating to the thruster development and the technology for the compact and efficient system are reviewed; the current status of the thruster performance is shown. Finally, a recently proposed future new application of the thruster is also discussed.

Ultrafast Sources of Intense Radiation

Abstract: Exploration at the frontiers of modern physics depends on electromagnetic radiation with almost unimaginable properties. Attosecond pulses freeze the motion of electrons. Petawatt beams accelerate particles to relativistic velocities in femtoseconds. Brilliant x-rays capture the interior structure of proteins. Lasers and laser-like sources of coherent radiation with extreme intensity, wavelength, and pulse duration promise further groundbreaking advances in both fundamental and applied science, yet surpassing current capabilities requires new methods for generating and manipulating high-intensity light. This dissertation presents a series of experimental, computational, and theoretical advances towards the development of plasma-based sources of extreme radiation with a focus on relativistic high-order harmonic generation (HHG) from plasma mirrors for high-energy extreme ultraviolet and x-ray generation and plasma-mediated parametric amplification for high-power lasers. In particular, this work offers the following contributions to laser-plasma interaction physics. A detailed experimental characterization of ultrafast plasma mirror performance over a broad range of parameters provides spectral and spatial measurements of second, third, and fourth harmonic generation for varied intensity and contrast, demonstrates relativistic harmonic generation, and relates high-order harmonic generation to plasma-mirror mechanical stability. Key features of the relativistic HHG spectrum are explained by a model for the synchrotron-like motion of plasma electrons, which includes the dynamics of the electron bunch formation and quantifies the efficiency limits and scaling of the process. Harmonic generation dramatically improves for two-color and multi-color driving beams, with a strong dependence on the exact waveform shape; the mechanism for this enhancement arises from the sub-cycle interplay between laser and plasma fields. This also leads to predicted performance improvements for cascaded plasma mirror systems. The Brillouin mechanism outperforms Raman scattering for x-ray amplification and plasma amplification in the pump depletion regime tolerates substantial incoherence. These two observations

Nonlinear dynamics of ion acoustic waves in quantum pair-ion plasmas

Abstract: The nonlinear properties of the ion acoustic waves (IAWs) in a three-component quantum plasma comprising electrons, and positive and negative ions are investigated analytically and numerically by employing the quantum hydrodynamic (QHD) model. The Sagdeev pseudopotential technique is applied to obtain the small-amplitude soliton solution. The effects of the quantum parameter , positive to negative ion density ratio and Mach number on the nonlinear structures are investigated. It is found that these factors can significantly modify the properties of the IAWs. The existence of quasi-periodic and chaotic oscillations in the system is established. Switching from quasi-periodic to chaotic is possible with the variation of Mach number or quantum parameter .

Perspectives of Electron Cyclotron Resonance Ion Sources Beyond the Scaling Laws

Abstract: Electron cyclotron resonance ion sources (ECRIS) are the most efficient ion sources among those used in facilities for nuclear physics with stable and exotic beams, because of their ability to generate intense beams of medium charge state ions, or moderate intensities at high and very high state of charge (hundreds of ${\rm e}\mu \hbox{A}$ of ${\rm U}^{33+}{\rm o}\ {\rm Xe}^{34+}$ ). Their development has been based primarily on semi-empirical laws (High-B mode plus frequency scaling), which link the performances in terms of current and produced charge state distribution to the magnetic field (that provides the ion confinement in the plasma) and to the frequency of microwaves (used for plasma heating). A further scaling in field and frequency, to access larger extracted current and charge states, involves a considerable impact on the ion sources complexity and cost, probably exceeding the technological limits for superconducting magnets. The experience gained in the last decade produced an understanding of some new mechanisms of plasma production in ECRIS, highlighting the main weaknesses of the previous model. Additional requirements such as the improvement of stability and reliability or the minimization of beam-current ripple require a perfect knowledge of the plasma heating mechanism, to be obtained via experimental and theoretical work, accompanied by adequate plasma and beam diagnostics. We will review hereinafter the basis of the so-called “standard model” for ECRIS beam production along with the new ideas that in the coming years may disclose the path towards further improvements.