다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Review of Charged Particle Dynamics. Beam Optics and Focusing Systems Without Space Charge. Linear Beam Optics with Space Charge. Self-Consistent Theory of Beams. Emittance Variation. Beam Physics Research from 1993 to 2007. Appendices. List of Frequently Used Symbols. Bibliography. Index.

Theory and Design of Charged Particle Beams

Ion acceleration driven by superintense laser pulses is attracting an impressive and steadily increasing effort. Motivations can be found in the applicative potential and in the perspective to investigate novel regimes as available laser intensities will be increasing. Experiments have demonstrated, over a wide range of laser and target parameters, the generation of multi-MeV proton and ion beams with unique properties such as ultrashort duration, high brilliance, and low emittance. An overview is given of the state of the art of ion acceleration by laser pulses as well as an outlook on its future development and perspectives. The main features observed in the experiments, the observed scaling with laser and plasma parameters, and the main models used both to interpret experimental data and to suggest new research directions are described.

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Ion acceleration by superintense laser-plasma interaction

Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used the Yee staggered grid for field variables combined with a leapfrog EM-field update and the Boris algorithm for particle pushing. The general properties of such schemes are well documented. Modern PIC codes tend to add to these high-order shape functions for particles, Poisson preserving field updates, collisions, ionisation, a hybrid scheme for solid density and high-field QED effects. In addition to these physics packages, the increase in computing power now allows simulations with real mass ratios, full 3D dynamics and multi-speckle interaction. This paper presents a review of the core algorithms used in current laser-plasma specific PIC codes. Also reported are estimates of self-heating rates, convergence of collisional routines and test of ionisation models which are not readily available elsewhere. Having reviewed the status of PIC algorithms we present a summary of recent applications of such codes in laser-plasma physics, concentrating on SRS, short-pulse laser-solid interactions, fast-electron transport, and QED effects.

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Contemporary particle-in-cell approach to laser-plasma modelling

For many years, laser-driven ion acceleration, mainly proton acceleration, has been proposed and a number of proof-of-principle experiments have been carried out with lasers whose pulse duration was in the nanosecond range. In the 1990s, ion acceleration in a relativistic plasma was demonstrated with ultra-short pulse lasers based on the chirped pulse amplification technique which can provide not only picosecond or femtosecond laser pulse duration, but simultaneously ultra-high peak power of terawatt to petawatt levels. Starting from the year 2000, several groups demonstrated low transverse emittance, tens of MeV proton beams with a conversion efficiency of up to several percent. The laser-accelerated particle beams have a duration of the order of a few picoseconds at the source, an ultra-high peak current and a broad energy spectrum, which make them suitable for many, including several unique, applications. This paper reviews, firstly, the historical background including the early laser-matter interaction studies on energetic ion acceleration relevant to inertial confinement fusion. Secondly, we describe several implemented and proposed mechanisms of proton and/or ion acceleration driven by ultra-short high-intensity lasers. We pay special attention to relatively simple models of several acceleration regimes. The models connect the laser, plasma and proton/ion beam parameters, predicting important features, such as energy spectral shape, optimum conditions and scalings under these conditions for maximum ion energy, conversion efficiency, etc. The models also suggest possible ways to manipulate the proton/ion beams by tailoring the target and irradiation conditions. Thirdly, we review experimental results on proton/ion acceleration, starting with the description of driving lasers. We list experimental results and show general trends of parameter dependences and compare them with the theoretical predictions and simulations. The fourth topic includes a review of scientific, industrial and medical applications of laser-driven proton or ion sources, some of which have already been established, while the others are yet to be demonstrated. In most applications, the laser-driven ion sources are complementary to the conventional accelerators, exhibiting significantly different properties. Finally, we summarize the paper.

https://iopscience.iop.org/article/10.1088/0034-4885/75/5/056401/pdf

Review of laser-driven ion sources and their applications.

Laser-driven ions have compelling properties and their potential use for medical applications has attracted a huge global interest. One of the major challenges of these applications is generating beams of the required energies. To date, there has been no systematic study of the effect of laser intensity on the generation of laser-driven ions from ultrathin foils during relativistic transparency. Here we present a scaling for ion energies with respect to the on-target laser intensity and in considering target thickness we find an optimum thickness closely related to the experimentally observed relativistic transparency. A steep linear scaling with the normalized laser amplitude a0 has been measured and verified with PIC simulations. In contrast to TNSA, this scaling is much steeper and has been measured for ions with Z > 1. Following our results, ion energies exceeding 100MeV/amu are already accessible with currently available laser systems enabling realization of numerous advanced applications

Scaling of laser-driven ion energies in the relativistic transparent regime

In this paper we report an extension to Henderson et al.'s (2006) case study, in which we investigate the generality of the anticorrelation between the del.P-e and j x B terms in Ohm's law observed in the plasma sheet. Further current sheet crossings are investigated which occurred on 17 August 2003 and 24 September 2003. Data from this period are particularly relevant as the interspacecraft separations are at their smallest for the Cluster mission. We confirm the generality of the observed anticorrelation and observe that the contributions to the electric field were mainly in the direction normal to the neutral sheet. A simple magnetohydrostatic treatment is used to explain the correlation and directional organization. The treatment is able to explain the anticorrelation and how the relative contributions to the electric field from the del.P-e and j x B terms in Ohm's law may be linked to the temperature ratio of the different plasma constituents as well as their spatial scales. In the examples reported here, the scale length over which the electron pressure changed le was smaller than the scale over which the ion pressure changed l(i), with l(e)/l(i) being between similar to 0.1 and similar to 0.4.

The relationship between j x B and del center dot P-e in the magnetotail plasma sheet: Cluster observations

Erratum: “Use of external magnetic fields in hohlraum plasmas to improve laser-coupling” [Phys. Plasmas 22, 010703 (2015)]

Laser-driven particle acceleration has been under intense investigation for the last decade and is of particular interest for key applications such as medical physics, fast ignition and inertial confinement fusion. The dominant ion acceleration mechanism is known as target normal sheath acceleration (TNSA); although easy accessible it suffers from a low energy conversion efficiency. Recently reported maximum ion energies1 are in the range of a few tens of MeV, which is well below the energies needed for most applications. Recently proposed acceleration mechanisms utilize ultra-high contrast laser pulses and ultra-thin solid targets allowing for generation of ions in the GeV range from intense laser-plasma interaction. A high laser contrast suppresses pre-ionization of the solid target by any pre-pulses or laser pedestals and in theory enables acceleration beyond TNSA in regimes such as the break-out afterburner (BOA)2 or radiation pressure acceleration (RPA).

Generation of 0.5GEV C6+ ions from irradiation of ultra-thin foils with high contrast, high intensity laser pulses

To support the design and analysis of x-ray radiographic facilities and experiments at Los Alamos, we have developed an integrated chain model, which is a set of linked physics simulation codes to generate self-consistent synthetic radiographs of experiments [1]. The expectation-maximization (EM) algorithm [2] has recently been used to great advantage to link particle- in-cell (PIC) methods, which model electron propagation to a converter target, and Monte Carlo transport methods, which model bremsstrahlung photon generation and transport through the radiographic object onto a detector. The EM algorithm is a maximum- likelihood technique to estimate the probability density function (PDF) of a set of measurements. A high performance implementation of the EM algorithm to characterize multidimensional data sets using a PDF parameterized as a Gaussian mixture has been developed (GMIX). The resulting PDFs compare favorably to histograms / tallies---no binning artifacts and less noisy (especially in the tails). GMIX is being used extensively in the radiographic chain model to quantify bremsstrahlung x-ray emission from rod-pinch diodes and other devices. In particular, the PIC simulation code MERLIN is used to model the dynamics of the rod-pinch diode in the Los Alamos radiographic machine Cygnus for the linked calculations. The rod-pinch diode used in Cygnus consists of a 9- mm diameter aperture cathode and a 0.75- mm diameter needle anode. A TEM pulse launched at one simulation boundary sets up the voltage required for the electron emission. The electron trajectories are followed self-consistently in the electromagnetic fields as the electron beam pinches at the anode tip with energies up to 2.25 MeV. The Monte Carlo transport code MCNP is used to track the bremsstrahlung photons generated by electrons incident on the anode tip. GMIX is used to “upsample” the PIC electrons to provide a suitably large population for the Monte Carlo calculation (10 7 or greater) that would have been computationally expensive to generate directly. The motivation, the mathematical properties, and the implementation details, and applications of GMIX to plasma and Monte Carlo simulations will be discussed, including: improved coupling of PIC to Monte Carlo simulations, adaptive PIC simulations, and characterization of the Cygnus radiographic parameters such as energy and angular spectra, spot size, and dose.

/pdf/a-maximum-likelihood-method-for-linking-of-particle-in-cell-4719k8rw9c.pdf

Lin Yin

Papers

Scaling of laser-driven ion energies in the relativistic transparent regime

The relationship between j x B and del center dot P-e in the magnetotail plasma sheet: Cluster observations

Erratum: “Use of external magnetic fields in hohlraum plasmas to improve laser-coupling” [Phys. Plasmas 22, 010703 (2015)]

Generation of 0.5GEV C6+ ions from irradiation of ultra-thin foils with high contrast, high intensity laser pulses

A Maximum Likelihood Method for Linking of Particle-in-Cell and Monte Carlo Simulations